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Hand(black) Users Manual - Computer Science Department

1. 51 FIGURE 18 MANUAL TORQUES WITCH 54 FIGURE 19 SHROUD COVER REMOVAL sscsssssssssssssscssscsssessscssesssssessseezers 56 FIGURE 20 BARRETTHAND CONTROLLER BLOCK DIAGRAM 58 FIGURE 21 BARRETT S PATENTED TORQUESWITCH MECHANISM 62 FIGURE 22 TORQUES WITCH OPERAT ION eren eene 64 FIGURE 25 BARRETTHAND IN ZERO POSITION ccccssssssssssssssssssscessssees 69 FIGURE 26 D H FRAME ASSIGNMENT FOR FINGER 1 70 4 Barrett Technology Inc BH8 255 User Manual version 1 0 FIGURE 27 D H FRAME ASSIGNMENT FOR FINGER 2 72 FIGURE 28 D H FRAME ASSIGNMENT FOR FINGER 74 FIGURE 29 FINGER JOINT MOTION LIMIT RANGE eres 76 FIGURE 30 SPREAD JOINT MOTION LIMIT RANGE eere 77 List oF TABLES TABLE 1 FIRMWARE FILE LIST ocssssssssssssrsssscssrssssessscssesssssssssrsssssssseesees 20 TABLE 2 MOTOR PREETIXEG scsscssssssssssssscsssesssssssesscesscssrssssssssesssessssssseessees 22 TABLE 3 REALTIME CONTROL PARAMETERS eren nnne 34 TABLE 4 HAND STATUS CODKG scssscssssssscssscsssesscssrsssssssscsssessssssssscsssssossees 35 TABLE 5 LUBRICATION SCHEDULE
2. 12 Rides 21 Hysteresis toten ath RO Dosti Eeer eens 41 82 Idler UE 51 82 Ind pendent control4 i e Aen tento tete ue dt 80 Industrial rippers eee eei peto qe eee atate edes 8 83 J Joint eer ERE rt e tec se edere eet 68 Joint imotion eerte tec res o t cte e o uper out 76 78 Torque Sensors eo d duo ee ese vet bs 14 K Kanematies ieee ec nie ee eh ea OR EE ets 66 78 83 Kinematics E D H Meel 67 Finger EE 70 Rasse Eeer 72 Bin Ger E eege 74 ee 67 Homogeneous Transform 67 L bench stand nieht Eee E EE ERTE 11 17 Doce 11 83 been zu se EE AEN EE A eei esee 12 43 M Maintenance oe s sd e t edd esa 41 Maintenance Klb er eM NEAL e 12 43 Monitor Strain geed ee ee 48 chip ete tro etiem eere dee ae eee 58 Motor Power ted eene eee aen eee eee 58 Motor prefixes ices eee PA qe ree ee aere te eq 22 4521 NE eer a v te t 59 78 leie E e DEE 60 IN ee 59 Maximum velocity
3. Use Equation 10 and the values Table 7 to determine finger F2 s end tip position Barrett Technology Inc 73 BH8 255 User Manual version 1 0 Finger Kinematics Fingers 1 amp 2 Zw 230 2131 Figure 28 D H Frame Assignment for Finger Note The spread motion only affects motions for fingers F1 and F2 Therefore we added an extra frame for finger F3 for consistency between all finger joint variables Table 10 D H Link Parameters for Finger F3 ex _ LA m2 Dj 0 The relationship between frame 0 and the wor d coordinate frame is determined by using Barrett Technology Inc 74 BH8 255 User Manual version 1 0 oor CH ooo The transforms from each axis to its previous axis can be determined using the homogeneous transform in Equation 5 and the link parameters for finger F3 in Table 10 Using Equation 6 the forward kinematics were determined to be Cap 0 Sap Dis A c 4 F 1 0 0 rl Sa Gs 455 Data 4 8 0 0 0 1 Equation 11 Forward Kinematics for Finger Where a 0 P b 0 P Cap b 5 Sin a b Use Equation 11 and the values in Table 7 to determine finger F3 s end tip position Barrett Technology Inc BH8 255 User Manual version 1 0 75 7 6 Joint Motion Limits The maximum joint motion limits for the BarrettHand are calculated based on the zero position seen in F
4. de 24 60 ERG mE 24 60 HOLD ifs eee attendent tate ea meo Dim 24 ellc 24 34 EENG M 25 34 25 34 LEAP cotton 25 34 Seege eie e ede 25 34 3 gen pet Reo e tee e an get Ait E pe 25 34 LEES 26 34 ieu Me 26 34 EEVGC zu etd nace tete Sees ep RI ge du EA S 26 34 t oli e e e D BO E HO gerit senda 26 61 erster au eg oH Bero eH I I ps RE s 26 61 de etti to t 27 60 MS ee eege Eer ESA ee 27 27 5 27 SO dade ath tint epee 27 EIER MEET 28 ed Muertos dee alten Re r 28 SSOP he Miu do M A A 28 60 G aet e Ee EE ee 9 65 80 82 eege d 8 82 Guide cltps n nat e dut 11 17 18
5. control data follows respond with an acknowledgement character C Terminate loop mode The possible feedback block header bytes are ds The BarrettHand has received the control block successfully lt CRLF gt ERR An error occurred the status code will follow immediately Before sending information to the BarrettHand in RealTime mode it is necessary to determine what the control and feedback blocks will contain Do this by setting the RealTime control flags before entering RealTime mode Setting a flag TRUE indicates that it will be part of the control or feedback block A flag for each motor needs to be set Set the flags by using the FSET command See Table 3 for a detailed description of the flags There are also three RealTime variables that need to be set before entering RealTime mode These three variables affect how the RealTime control values are interpreted Set these variables by using the FSET command See Table 3 for a detailed description of the variables Barrett Technology Inc 33 BH8 255 User Manual version 1 0 Table 3 RealTime Control Parameters Size in Block LCV Loop Control Flag If True RealTime control signed byte Velocity block will contain control velocit N A Loop Control Variable LCV is multiplied by Velocity integer LCVC to determine control Coefficient velocit LCPG Loop Control Flag If True RealTime control 1 unsigned Proportional Gain block will contain byte Proportional G
6. cscssssssssssssssssssersessressssserssesssesseesssers 43 TABLE 6 BARRETTHAND MOTOR PROPERTIES eere eene eene 59 Barrett Technology Inc BH8 255 User Manual version 1 0 TABLE 7 D H PARAMETER VALUES FOR ALL 67 TABLE 8 D H LINK PARAMETERS FOR FINGER Fl1 eene 70 TABLE 9 D H LINK PARAMETERS FOR FINGER FP2 eren 72 TABLE 10 D H LINK PARAMETERS FOR FINGER LF3 eee 74 List or EQUATIONS EQUATION 1 VELOCITY CONVERSION sssssssssssssrssesssssssssssessssserssessssssessers 59 EQUATION 2 VELOCITY CONTROOL scssscssrsssssssessrsssessssssrssssssssssesssessresees 60 EQUATION 3 TRAPEZOIDAL PROFILE CONTARODL eene 60 EQUATION 4 MOTOR eene 61 EQUATION 5 HOMOGENEOUS TRANSFORM BETWEEN 1 AND K 67 EQUATION 6 FORWARD KINEMATICS FROM FINGERTIP TO WORLD 67 EQUATION 7 MOTOR TO JOINT ANGLE TRANSFORM BEFORE TORQUESWITCH M ACTIVATION eeeeee eene eene enne onu nee 68 EQUATION 8 MOTOR TO JOINT ANGLE TRANSFORM AFTER TORQUESWITCH M ACTIVATION eeeeee eene nennen nounou aane nn 68 6 Barrett Technology Inc BH8 255 User Manual version 1 0 Barrett Technology Inc BH8 255 User
7. ime void Set RealTime Flags to be sent during RealTime control if result bh RTSetFlags 123 1 1 0 0 1 Errori 0 1 0 1 MUIMMLMMlMIMIMMlIR YTT TT PTT P P P Pg TATA TATA TTT TTT TTT P P P TTT g Run RealRime loop return 1 if interrupted with a key int RunReal Time void double var 4 3 int N 0 motor DWORD time tmstart bool terminate false Start RealTime Mode bh REStart 12 31 Start timer tmstart GetTickCount Send RealTime control to hand bh RTUpdate printf Press Any Key to Abort Control Hand until termination while terminate amp amp kbhit time GetTickCount tmstart Get RealTime Position and time For motor 0 motor lt 4 Get motor position var motor 0 bh RTGetPosition Get time var motor 1 double time Get number of iterations var motor 2 double N Set F1 close velocity to 55 value int 55 00 bh RTSetVelocity 1 value If Fl position is 5000 then set F2 velocity to 55 otherwise set to 0 value int 01 101 gt 5000 00 55 bh RTSetVelocity 2 value F2 position is gt 5000 then set F3 velocity to 55 otherwise set to 0 value int var 1 0 5000 00 55 Barrett Technology Inc BH8 255 User Manual versi
8. ete dt Mee Eia tee ese etus 33 K 33 5 DS ALC TY EE 15 Electrical Shock oet E Re edt eue I d 15 E VE RII Seu Eumene 15 16 ie WI HE GR E RIEN EERSTEN ENEE 15 Serial communication 5 emet NRI OD ati 10 58 83 OE M 45 47 51 52 83 SEI Mee EE 47 56 en 9 64 80 83 el TT 44 62 83 Status Codes soc 21 33 35 TASTAN EEN 14 41 47 65 Balancing potentometer inneren enne nennen nnne nnne nenne nennen nnne 47 NUM EP RE 65 Ve e 66 E 47 S ubs ription Ee 14 jesse EE 19 Supervisory Control 21 36 83 SUrge protectio esie egets 10 KOL E 14 KE EE 8 Threaded eet RR E EU ERR S 9 Threaded locking ring 50 1 eee eee Dreh I RENE 13 18 83 Torque wrench Renee egt m e dte datasets ene ise 12 42 Kee UE 9 61 67 80 81 84 TorqueSwitclM scs isse eie peteret tie it ge i ee ede tieu te t R6S6t EE 63 68 Threshold torque eee ee id e eie e te 62 6Tro bleshooting 4 echte ie ede e beech et t e i deer Hd 50 Close position ENEE edes e Ree eee e E EAR ERR 55 Communication idein ned pepe e ENEE e E ee Tes ed desde RENE eds 50 Finger closed o E A 52 Fret OO EE o eee Re
9. ASS EBLE Ven sak a dea 19 Control block NOT AN EE ER aE 33 1 1 7Control software 11 Installation IE 19 CPU board ee tiet dite e ie RES 58 Gycle etu Rep ee eae n i tbe EE 44 82 D RE Ee 79 eere fives deca e 29 30 31 58 3 2Blectrical connections c ete tu eer Mee 18 AC Tine cord xe tero everest 10 11 19 eret nt eoim opem equipe iei 10 11 18 Serial cable esu dome guine e a e mi Ev 10 11 18 Electronic architecture x ei aeg e HEC EPOR E P 58 i2 gue EA EE 53 58 59 68 78 F iuo 80 Bastemet check een an eee aic ate HIT 42 Feedback block header RETE EE eR 33 Angles o eda enel Due e Deas eias 46 55 Attachment ry rea p RET e e AER OR AE HERE 47 LEE 81 MOLIOD c mee ee 80 Removals asioi Iane TE E A a E oit M i e e EESTI INTERN 45 Farmware i tees pec EQ 11 50 82 e Download BEE 19 loj C PER 20 UDgrades Eeer ee ee ie R
10. eres oe eese eene ae eon e Ye Sea ao EN Uo uuu S eeu Ve ua Uno Pa oes eoa Pede 42 5 3 LUBRICATION NEUES ses UU aea eoo 43 5 4 STRAIN E 47 6 TROUBLESHOOTING oio eo sasassdsesacesassiscessesossedsassssocbeeVevesesosececocdssstecee 50 7 THEORY OF io 5525 ei iai ee eo d neuen o soos oia 000 58 7 1 ELECTRONIC ARCHITECTURE see ee euo eet ones U eoa pa oes SS eae a ee de 58 7 2 MOTOR e EE 59 7 3 MEGCHANISMS eno and ea sio SU epe Re RN See eo ope Vo Use e eR U SE 61 T 3 TORQUES WITCH teer e 61 LB 25 SPREAD MOTION eerte lu d e ee eb v ieu t P ee OE vB eI ins 64 7 4 OPTIONAL STRAIN GAGE JOINT TORQUE SENSOR eene eese ette 65 7 5 66 7 6 JOINT MOTION 5 76 2 Barrett Technology Inc BH8 255 User Manual version 1 0 List or FIGURES FIGURE 1 BARRETTHAND scsscsssssssssssrssscsssesscssrsssssssscsssesscsssssssssscssssssssecssasers 9 FIGURE 2 BARRETTHAND POWER SUPPLY eere eene nnnnn 10 F
11. e Plug the other end of the AC line cord into a suitable AC wall source 3 3 Host Computer The BH8 255 Control Software was written for computers running Windows 95 98 NT 4 0 Barrett Technology recommends using a Pentium based processor with a minimum CPU clock speed of 266 MHz and 32 Mbytes of RAM The software requires 10 Mbytes of free disk space 3 4 Installing BH8 255 Control Software The BH8 255 Control Software consists of the BHControl Interface firmware and example programs The BHControl Interface is a Windows API that allows you to control the BarrettHand quickly and easily The BHControl Interface can be used to test Supervisory and RealTime control sequences communication loop rates demonstrate functionality learn how to independently write C code and automatically generate C code based on tested algorithms Run the setup exe program on the disk labeled BH6 255 Control Software Disk 1 of 5 This will install all necessary files for using the BHControl Interface the most recent version of firmware online manuals and example programs 3 5 Download Firmware The BarrettHand has firmware that resides in the onboard electronics This firmware is stored in RAM that receives its power from the Power Supply when the system is turned on and from an embedded super capacitor when powered down This super capacitor maintains the firmware in RAM from one day up to one week before the capacitor is fully discharged and the memory is
12. 7 Theory of Operation 7 1 Electronic Architecture CPU Board The CPU board handles all set up communications and high level control of the power boards including coordinated motion force monitoring and motor speed monitoring The main processor is a Motorola 68HC811E2FN microcontroller which contains 256 bytes of RAM and 2Kbytes of EEPROM The CPU board contains a 128 Kbytes RAM chip external to the microprocessor which is used to store the BarrettHand firmware The microcontroller operates at 1 25 MHz and communicates via standard RS 232C protocol at a factory selected baud rate of 9600 no parity bits eight bits per character and one stop bit The BarrettHand is capable of communicating at rates up to 38 4K baud Motor Power Boards Each power board handles current control of a single DC brushless motor in the BarrettHand using a Hewlett Packard HCTL 1100 motion control chip The optical incremental encoder signals from each motor with 360 counts per motor revolution are amplified and sent to the HCTL 1100 chip The controller uses the encoder feedback for alignment at startup and for commutation of the motors via 10 20 kHz Pulse Width Modulation PWM It can also perform position and velocity control A functional block diagram of the power board and its relation to other pieces of the control system is shown in Figure 20 CPU Board MC68HC11 Motion Controller HCTL 1100 i Ph
13. BH8 255 User Manual version 1 0 Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes 30 FLOAD Loads the saved parameters from EEPROM into memory N A This command loads the following parameters MCV MOV DS MSG DP FPG FIP FDZ EN SGFLIP ACCEL MPG TSTOP HOLD LCV LCVC LCPG LFV LFVC LFS LFAP LFAP LFDPC See Section 4 2 3 for the parameter definitions FSAVE Saves the present values of the parameters to EEPROM N A This command saves the following parameters MCV MOV DS MSG DP FPG FIP FDZ EN SGFLIP ACCEL MPG TSTOP HOLD LCV LCVC LCPG LFV LFVC LFS LFAP LFAP LFDPC See Section 4 2 3 for the parameter definitions FSET Sets the specified parameters to the desired value MOV MCV MSG DS DP LCV LCVC LCPG LFV LFVC LFS LFAP LFDP LFDPC FPG FIP FDZ ACCEL MPE TSTOP HOLD SGFLIP EN BAUD See Section 4 2 3 for information on the firmware parameters HI Initializes the finger and spread motors Opens all of the joints to their full open position and sets it to be zero N A The BarrettHand will vibrate the joints during this operation This command needs to be executed before any motion commands IC Incremental close for specified motors N A The increment size is defined in the
14. and cost of the BarrettHand one motor drives the spread action of both fingers synchronously and symmetrically about the palm The spread motion adds surprising dexterity One design feature of the spread motion is that unlike the curling motions of each finger the spread is highly backdrivable so that the spread compliance is controllable By setting low spread compliance the BarrettHand dynamically finds the lowest energy state as the fingers close resulting in a firm and reliable grasp Can the two finger joint motions be controlled independently No the two joints are controlled by one servo motor Although the mechanism behaves in an intelligent manner for grasping we traded the second motor and motor electronics for the TorqueSwitch mechanism to save weight bulk heat power and cost 03 04 4 Q5 5 How does the Torque Switch mechanism work and what is the clutch used for See Section 7 3 for information on how the TorqueSwitch mechanism works What materials are the fingers made of particularly the fingertips Nylon is used for the fingertips and covers The finger links are made of aluminum and the gearing is made of steel and bronze Is it possible to determine the instant when the TorqueSwitch is activated It is possible to determine the approximate time when the TorqueSwitch is engaged by monitoring the velocity in RealTime mode The velocity will approach zero and
15. e Maintenance e Troubleshooting e Theory of operation e Technical specifications e Frequently asked questions The second manual is the BHControl Interface Manual and is a tool for learning the BHControl Interface The BHControl Interface is a Windows application and allows you to control the BarrettHand quickly and easily Refer to this manual for instructions on how to control the BarrettHand Both manuals are also in electronic form on the Control Software diskettes 8 Barrett Technology Inc BH8 255 User Manual version 1 0 1 1 3 BarrettHand BarrettHand shown in Figure 1 is comprised of three fingers two of which rotate about the base joint The fingers are labeled F2 and Each of the three fingers on the BarrettHand feature two joints driven by a single DC brushless servo motor Finger joints are coupled through Barrett s patented TorqueSwitch which automatically switches motor torque to the appropriate finger joint when closing on a target object Using the fingers together allows the BarrettHand to grasp different objects securely The fourth motor moves F1 and F2 in the coupled spread motion around the palm allowing on the fly grasp reconfiguration to adapt to varying target object sizes shapes and orientations The BarrettHand spread function in conjunction with TorqueSwitch effectively makes object grasping target independent The BarrettHand shown in Figure 1 is equi
16. finger close command Barrett Technology Inc 63 BH8 255 User Manual version 1 0 Figure 22 shows the sequence of events occurring when the clutch is utilized Finger Starts from Home Position Both Joints Move with Motor Clutch Engaged Threaded Shaft Rotates with the Clutch Gear Inner Link Contacts an Object Clutch Disengages Disengaged and Free wheeling Down the Threaded Shaft Fingertip Continues to Close while the Inner Link Holds Position Clutch Near End of Travel on Threaded Shaft when Fingertip Contacts Object Figure 22 TorqueSwitch Operation 7 3 2 Spread Motion The spreading action of fingers F1 and F2 on BarrettHand increases the dexterity of the entire unit with only one additional actuator Optimal grasp configurations can be achieved on the fly without costly tool changes Barrett Technology Inc BH8 255 User Manual version 1 0 associated with traditional grippers In addition the backdrivability built into this degree of freedom causes the BarrettHand s grasp shape to change in mid grasp creating a more stable grasp of oddly shaped target objects Should you wish to control the spread position of the fingers the complete command set available to the fingers is also available for the spread including commands for fixed increment motion and move to position commands 7 4 Optional Strain Gage Joint Torque Sensor The BarrettHand provide
17. 12 bit integer For example Integer Fraction 200 Control Velocity 0000 0000 1100 1000 Binary Lower 8 bits of Integer 0000 1100 12 Maximum Velocity 12 quadrature counts sample time It is important to note the minimum velocity required to move the motors during Trapezoidal Profile Mode is 16 7 3 Mechanisms 7 3 1 TorqueSwitch Barrett Technology s patented TorqueSwitch mechanism affords the BarrettHand unparalleled weight reduction without sacrificing dexterity or functionality by serving as a smart coupling of two finger joints to one motor The mechanism s operation is similar to that of a simple screw fastener Theoretically the torque with which one tightens a uniform screw should be equal to that which is required to subsequently loosen it neglecting inertia and provided all materials deformations remain elastic This principle holds true for the TorqueSwitchTM mechanism The TorqueSwitch consists of a threaded shaft a pair of Belleville spring washers and a spur gear with a threaded bore shown in Figure 21 Barrett Technology Inc 61 BH8 255 User Manual version 1 0 J2 Worm Gear Motor Pinion 4 Threaded Spur J1 Worm Gear Gear Belleville Threaded Washers Worm Shaft Figure 21 Barrett s Patented TorqueSwitch Mechanism The following description follows the progression of Figure 22 When the clutch is engaged both worm gear drives and their corresponding finger links are coup
18. Cap 5 0 0 0 1 Equation 9 Forward Kinematics for Finger F1 Where a 0 b 0 Cap cos a b 8 51 b c cos 54 sin O Use Equation 9 and the values in Table 7 to determine finger F1 s end tip position Barrett Technology Inc 71 BH8 255 User Manual version 1 0 Finger F2 Kinematics 7 oi Finger 3 x rh e Z J2T D Chi i C gt um SC 2120 Zu o N M S Qn Figure 27 D H Frame Assignment for Finger F2 Table 9 D H Link Parameters for Finger F2 Joint Qa di 6 1 foto of 2 2 0 On 3 Ae 0 0 T Aj m2 D 0 The relationship between frame 0 and the world coordinate frame is determined by using 100 0 n 1010 D of 001 0 0001 Barrett Technology Inc 72 BH8 255 User Manual version 1 0 transforms from each axis to its previous axis be determined using the homogeneous transform in Equation 5 and the link parameters for finger F2 in Table 9 Using Equation 6 the forward kinematics were determined to be 4 7 54 A5C4 D 7648 Ac T S4Cab Sab 4598465 54 4 54 434 D Sab 0 Ass 4 5 0 0 0 1 Equation 10 Forward Kinematics for Finger F2 Where a 0 P b 0 Cap b 5 51 b c cos 4 54 sin
19. Help information about the lt Command gt specified Parameters N A Notes None Command C Function Stops the motors and clears the input buffer A new prompt will be output Parameters Notes None 32 Barrett Technology Inc BH8 255 User Manual version 1 0 4 2 5 RealTime Control One features of the BarrettHand is the RealTime control This control mode allows you to send commands and receive feedback continuously from the BarrettHand Any desired control law can be applied by using the host computer to determine the desired motor command and then applying that command to the BarrettHand in real time The communication bandwidth is dependent on the amount of control information sent feedback information requested and the selected baud rate Data from the host computer to the hand is grouped into control and feedback blocks Each block has a single byte header followed by a set of data The control block header specifies whether or not control data is to follow and whether or not a feedback block is to be returned The feedback block header returned acknowledges the receipt of the control block or indicates an error The control block header can also terminate the loop mode The possible control block header bytes are C Control data follows respond with a feedback block c Control data follows respond with an acknowledgement character A control data follows respond with a feedback block a
20. LFAP 0 LFDP 1 LFDPC 1 Enter RealTime control by issuing the following command Barrett Technology Inc 34 BH8 255 User Manual version 1 0 1241 The BarrettHand will then send a single and wait for control blocks Each control block will consist of three bytes C Control data follows respond with feedback block 1 signed byte of velocity for motor F1 1 signed byte of velocity for motor F2 Each feedback block will consist of six bytes acknowledge character unsigned byte of strain for motor F1 1 signed byte of delta position for motor F1 1 unsigned byte of strain for motor F2 1 signed byte of delta position for motor F2 1 signed byte of delta position for motor 4 Each control block from the host will stimulate a feedback block from the BarrettHand When the host is finished it will send the single character C 0x03 the BarrettHand will respond by printing the command prompt gt and waiting for a new command 4 2 6 Status Codes Status codes see Table 4 are sent by the BarrettHand when the communication was successful but the BarrettHand encountered a problem Keep in mind that BarrettHand status codes are powers of 2 so the return value may encode multiple flags Example a status code of 3 indicates status code 2 and status code 1 Table 4 Hand Status Codes O A j Nomotrfound 8 Unknown command Barrett Technology Inc 35 BH8 255 User Man
21. Spread 1 See Section 7 2 for more detailed description of how ACCEL affects motion BAUD Returns the current baud rate of the hand divided by 100 6 12 24 48 96 192 and 384 96 The value returned is in hundreds of bytes per second To determine the actual baud rate multiply the value returned by 100 DP This parameter defines the default position for a move command 0 20000 encoder counts 150 Spread 1000 Fingers None DS This parameter defines default step sizes for incremental open and close commands 0 20000 encoder counts 150 Spread 1200 Fingers None EN Specifies if a motor should be selected when a command has no prefix TRUE selected FALSE not selected Grasp TRUE Spread TRUE When a close command is issued C with no motor prefixes all motors will close with the default values Barrett Technology Inc 23 BH8 255 User Manual version 1 0 Purpose Values Default Notes Parameter Purpose Values Default Notes Parameter Purpose Values Default FDZ Derivative zero value for the motor control filter 0 255 Grasp 221 Spread 221 See section 7 2 for more detailed description of how FDZ affects motion FIP Integral pole value for the motor control filter 0 255 Grasp 66 Spread 66 See section 7 2 for more detailed description of how FIP affects motion FPG Proportional gain value for the motor co
22. accurately determined until the TorqueSwitch mechanism is reset Reset the TorqueSwitch by opening the finger against its open stop with a minimum speed of 40 Note The feedback device for each of the motors uses a 90 line or 360 count encoder Thus the motor angle is the encoder position Barrett Technology Inc 68 BH8 255 User Manual version 1 0 All of the kinematics for the BarrettHand derived from the zero position The zero position of the BarrettHand is shown in Figure 25 Figure 25 BarrettHand in Zero Position Barrett Technology Inc 69 BH8 255 User Manual version 1 0 Finger F1 Kinematics Finger 3 8 Zur b Figure 26 D H Frame Assignment for Finger 1 Table 8 D H Link Parameters for Finger F1 Joint ax or 6 pt 01 10 A 0 Ontos A 0 Ontos A 2 Ds o The relationship between frame 0 and world coordinate frame is determined by using Barrett Technology Inc BH8 255 User Manual version 1 0 70 100 0 0 1 0 D of 0 0 1 0 0 0 0 1 transforms from each axis to its previous axis be determined using the homogeneous transform in Equation 5 and the link parameters for finger F1 in Table 8 Using Equation 6 the forward kinematics were determined to be 84 CaS ab A3C4Cqy T S4 4 S484 AR 8 4C gn D3 S48 ay 4 54 484 Dy T Sab 0
23. cleared When the firmware has been cleared it will need to be reinstalled The download process takes only a few minutes as follows Verify BarrettHand is plugged into the Power Supply Verify the host computer is plugged into the Power Supply Verify the Power Supply is attached to a power source and turned on Run the BHControl Interface program BHControl exe Initialize the software by pressing the nitialize Library button Press the Start Download button Open the appropriate file according to Table 1 QUUM de uper The code generated by the Control Interface requires the C Function Library to compile Barrett Technology Inc BH8 255 User Manual version 1 0 8 Press Reset on the Power Supply 9 After downloading the file the BarrettHand is ready for operation Table 1 Firmware File List BarrettHand Firmware v3_0 S19 Version 3 0 Firmware BarrettHand Firmware 4 02 519 Version 4 02 Firmware with RealTime mode capabilities 20 Barrett Technology Inc BH8 255 User Manual version 1 0 21 4 BarrettHand Operation 4 1 Power Up Sequence Once the steps in Section 3 are complete your BH8 255 System is ready for use Power up the system according to the instructions below 1 Turn on the host computer Verify the serial cable is plugged into the desired communications port and into the 9 pin connector on the back of the Power Supply 3 Verify the BarrettHand Cable is plugged into the 15 pin conne
24. mechanism for accessing the serial port which allows both synchronous and asynchronous access to the low level thread and ensures that all serial communications are executed with high priority The low level thread manages all input and output buffers and makes controlling the BarrettHand easy 1 2 3 Strain gage Joint Torque Sensors Barrett Technology offers a factory installed torque sensor for the BH8 255 System This option uses strain gages to measures the differential tension in the tendon running through each finger to the second joint The information is processed in additional onboard circuitry and can be accessed by requesting the present strain gage parameter The strain gage parameter represents the amount strain on the strain gage sensors The strain gage values need to be calibrated by the customer to relate strain to joint torque The joint torque for the second finger joint is over a 1 0 N m range approximately 0 1 N m resolution See Section 7 4 for more detailed information on how the sensor works 1 2 4 Control Software Firmware Upgrades Barrett Technology makes software and firmware upgrades periodically Upgrades are available for purchase or free of charge for customers of Barrett s subscription service Refer to Barrett s enclosed Warranty and Subscription Service Policy for more information 14 Barrett Technology Inc BH8 255 User Manual version 1 0 2 Safety and Cautions PLEASE READ THIS SECTION IN ITS ENT
25. outer link Consider all loading situations including accelerated loads cantilever loads from long objects robot collisions active loads etc A portion of the onboard control electronics is exposed through the base of the BarrettHand Before installing to a robot arm take necessary precautions to protect the electronics from impact contaminants and static discharge Do not rest the BarrettHand unit directly on its base Use the included lab bench stand during standalone operation Remove the fingers only as instructed in Section 5 3 Barrett Technology Inc BH8 255 User Manual version 1 0 Monitor the operating temperature of the BarrettHand so that it does not exceed 65 C The BarrettHand was designed with non backdrivable finger joints to take advantage of the motors peak operating performance in short bursts The spread however is backdrivable to aid in target independent grasping see Section 7 3 2 and requires constant motor current to actively hold position Idling the spread motor when possible will help keep the temperature lower Barrett Technology Inc BH8 255 User Manual version 1 0 3 System Setup 31 Mounting Requirements 3 1 1 Lab Bench Stand When writing custom programs for the BarrettHand or using the unit without a host robot arm Barrett Technology recommends using the lab bench stand included and all its wire management clips as shown in Figure 5 These clips prevent the cable from pulling out of the B
26. strain gage value will never stop the motors P This parameter specifies the present motor position 0 20000 encoder counts N A This parameter can not be set This section lists all of the firmware parameters and their values for BarrettHand Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes S This parameter defines the current state of the motor 0 motor found and initialized or 1 motor not initialized N A This parameter can not be set SG This parameter specifies the current strain gage value 0 255 N A This parameter can not be set Barrett Technology Inc 27 BH8 255 User Manual version 1 0 Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes SGFLIP Specifies if the reported strain should be 255 actual strain TRUE reported strain 255 actual strain FALSE reported strain actual strain Grasp FALSE Spread N A Setting this value will inverse the direction of the change in strain for a given torque TEMP Returns the present temperature on the CPU board in tenths of degrees Celsius 550 to 1250 N A The value returned is in tenths of degrees To determine the actual temperature divide the value by 10 TSTOP Time in milliseconds before the motor is considered stopped 0 32767 Grasp 30 Spread 30 None Barre
27. tbe d e iet tu ete teste des 60 61 Peak torque tete tec ten e rei tet rs t er e deed 59 NEE 59 INTE 59 Proportional etre t t d RR 59 Sample time os ba re e t o e p nm e ted 60 Trapezoidal Profile controlzs ue En red de 60 VT n UV 59 78 Velocity eto mcns eet WE 59 60 Velocity conversion siete tun ate tem e e ee M Rs 59 Velocity If Ot sc tectum eheu teo tenti Ime 59 Montee ste eee ue 9 11 13 17 O itus cM otii AEEA Le Ser lebt 13 79 P aep 78 Position Sensini 5 i 78 Ne Dea exes cava 78 Power Supply ete ee eee ee EED Hic Re ded ede elated 10 Ne EE 10 Reset switch ee A Se EE es Hes hese 10 20 Power p sequence EE 21 Pre tensiOn i S ettet ee E e 41 51 52 55 56 83 ladder EE 58 R RAM ERE 58 Real Time conttol iiu cosets reet eerte eer ere stes evenisse tee 33 38 83 Real Time control usce reet oae torpet Ute OE SEO EG a RR
28. then will return to its original value See Figure 32 for a graph of the velocity during TorqueSwitch activation Torque Switch Analysis 12 10 Velocity Cts ms ON RO or O N _ 150 Time Slice 3ms Figure 32 TorqueSwitch Activation Graph For more questions please contact Barrett Technology Customer Service at 617 252 9000 GLOSSARY API An acronym for Application Program Interface the set of commands that an application uses to request and carry out lower level services performed by a computer s operating system Backdrivability Backdrivability is the measure of how accurately a force or motion that is applied at the output end of a mechanical transmission is reproduced at the input end In a mechanical robot like linkage good backdrivablility means that a person can grab the enditp of the linkage and move it around effortlessly BarrettHand The 1 1 kilogram dexterous robotic grasper as described Section 1 1 2 BarrettHand System The entire system received from Barrett Technology Inc Includes all components as listed in Section 1 1 plus any additional options as described in Section 1 2 Belleville Spring Washer A conical washer that has geometry specifically formed to produce a desirable spring constant Cycle Finger The equivalent to closing and opening the finger completely once
29. 000 The program is terminated after six seconds MIMMLMBMlMMMMMMPMlMIIEITT TT T T T T P P P P P T I I I I I I I I P P P P P P P P PIT P Pp P TTT TTT Automatically Generated C Cod BHand Control Center Version 1 0 d RealTime Mode include lt stdio h gt include lt stdlib h gt include lt math h gt include lt conio h gt include BHand h BHand bh Handles all hand communication int value Hand parameter obtained with Get int result Return value error of all BHand calls Error Handler called whenever result 0 void Error void printf ERROR d n s n result bh ErrorMessage result exit 0 TATA P P P P P P P TTT TT TTT UIT I Initialize hand set timeouts and baud rate void Initialize void if result bh InitSoftware 1 THREAD PRIORITY TIME CRITICAL Error if result bh ComSetTimeouts 0 100 15000 100 5000 if result bh Baud 9600 Error if result bh InitHand Error VALLALLA ALNA ILALA AAA LLALA ll ll I I I P P P TTT IP IP P PP TTT TTT Set parameters allocate data buffers load files 38 Barrett Technology Inc BH8 255 User Manual version 1 0 39 void 11
30. 35000 encoder counts Spread The equivalent to closing and opening the spread completely 6200 encoder counts Firmware Software that is embedded in a hardware device that allows reading and executing the software but does not allow modification e g writing or deleting data by an end user Grasp n The state in which an object has been firmly contained and secured by the BarrettHand v1 The method by which the BarrettHand closes its fingers around an object in order to secure it v2 The collective term for fingers one two and three as defined in the BarrettHand control software Graspcenter The center of an object being grasped by the BarrettHand Hysteresis The dependence of the state of a system on its previous history Idler Pulley A fixed or adjustable disc support for a drive cable or belt It is used in the BarrettHand for strain gage beam deflection Industrial Gripper These grippers have only one degree of motion freedom and can only execute an open close motion Because of the simple kinematics the gripper fingers often must be specifically designed for the parts that have to be grasped Product changes often require changes to the gripper assortment increasing the product change over time Furthermore an increase of the number of required grippers increases the number of required gripper changes during assembly Kinematics The science of motion which treats motion without regard to the forces wh
31. 5mm Max Figure 11 Removing the Fingers for Maintenance 6 Make note of the relative position of the fingertip and inner finger link since removing the finger will disengage the coupling between them Should either link or the spur gears to which they are attached move after the finger has been removed the fingertip position must be reset Use a 2 mm hex wrench to manually rotate the Joint 2 drive 6 1 2 revolutions from the position where both links are inline and horizontal Joint 2 Drive Access Joint 1 Drive Access T 45 00 Note that the threaded Correct fingertip angle set by spur gear is tight against rotating Joint 2 drive 6 1 2 turns the spring washers Figure 12 Resetting the Fingertip Position after Finger Removal Barrett Technology Inc BH8 255 User Manual version 1 0 46 7 Using the Mobil 1 Synthetic Grease syringe supplied with your maintenance kit apply a generous amount of lubricant around the motor pinion cavity of the motor Cover all gear teeth with a thick bead of grease See Figure 9 for lubrication points 8 Reset the fingertip position see Step 5 3 and replace the finger onto its motor according to Figure 13 again taking great care not to damage the gold contacts when seating the alignment teeth The teeth must be fully seated into the alignment slots to ensure proper operation of the BarrettHand Bring Finger toward Motor Face Create gap th
32. BarrettHand BH8 255 User Manual e Barrett Technology Inc TABLE CONTENTS LI SYSTEM DESCRIPTIQN ioi isses eei a s sees co iod ees so eee ue ease pa To aee cesa gae eo 8 1 1 STANDARD 8 255 8 2 2 eee 8 LAS SYSTEM PERATURES 8 1 1 2 DOCUMENTATION EE 8 1 S3BARRBERPEIANDA iet terr ete e tee erii vt 9 1 154 POWER SUPPLY E Ec 10 1 15 LAB BENCH EE 11 1156 ELECTRICA e EE 11 1 1 7 CONTROL SOFTWARE AND FIRMWARE 11 1 1 MAINTENANCE e EE 12 1 2 SYSTEM OPTIONS 13 BEE 13 1 2 2 BE 13 1 2 3 STRAIN GAGE JOINT TORQUE Srwsops 1111111 n eene 14 1 2 4 CONTROL SOFTWARE FIRMWARE 0 eene nme nennt 14 2 8 200 0 15 3 SYSTEMLSE PUP Si vo Ue Uo a VV E Uu n 17 3 1 MOUNTING REQUIREMENTS c soo oot o raa eeu nasa go pane uaa ea ea eoe oon e eie osos ds aeo 17 CAB BENCH S FAND Eta oet tern etuer etre 17 3 1 2 OPTIONAL ARM AnpaprtER aa 17 3 2 ELECTRICAL CONNECTIONS vssvescesssosssscscocesesenassessosedesease
33. Fastener Check All screw fasteners in the BarrettHand have been installed with a thread locker which should prevent loosening over the life of the product However after prolonged use Barrett Technology recommends that you conduct a precautionary inspection to ensure all external fasteners are in place and tight Ideally this inspection should occur monthly under heavy use conditions Should any fasteners have become dislodged during operation contact Barrett Technology for replacements or replacement specifications Do not replace fasteners without contacting Barrett Technology as many fasteners have strict length specifications Figure 8 shows some important fastener locations for inspection Palm Plate Screws Figure 8 Important Fastener Locations Barrett Technology Inc 42 BH8 255 User Manual version 1 0 5 3 Lubrication Each BarrettHand unit has been lubricated and tested prior to shipping Periodically lubrication must be reapplied to areas with high probability of lubricant flow Use the grease syringe to apply Mobil 1 Synthetic Grease both included with the maintenance kit to all exposed gear teeth at the application points according to Figure 9 and the schedule in Table 5 Table 5 Lubrication Schedule Barrett Technology Inc BH8 255 User Manual version 1 0 43 5000 cycles Finger Spur Gears 5000 cycles Finger Motor Spur Gears 5000 cycles Palm Spur Gears 5000 cycles Motor Spur Gear Lube oi
34. IGURE 3 LAB BENCH STAND eere eene en nennen sonans enata asa ennus 11 FIGURE 4 ARM ADAPTER eere eene enne annes nasa enne na aeenus 13 FIGURE 5 LAB BENCH STAND WITH WIRE STRAIN 17 FIGURE 6 INSTALLING AN ARM ADAPTER eren een eene 18 FIGURE 7 PRETENSIONING THE TENDON CABLE eren eene 41 FIGURE 8 IMPORTANT FASTENER LOCATIONS eere 42 FIGURE 9 LUBRICANT APPLICATION POINTSS eeeee eene eene 44 FIGURE 10 FINGER ATTACHMENT SCREW LOCATION eere 45 FIGURE 11 REMOVING THE FINGERS FOR 46 FIGURE 12 RESETTING THE FINGERTIP POSITION AFTER FINGER REMOVAL cscsssssssssssssessrsssrsssssssresssssssssessssssrssssesessssssssessrsssssssssssaserssesecssssessesssesees 46 Barrett Technology Inc BH8 255 User Manual version 1 0 FIGURE 13 REATTACHING FINGERS AFTER 47 FIGURE 14 SHROUD REMOVAL ssssscsssssssssssesssesscssrssssesssssssesascssssesssssessees 48 FIGURE 15 BALANCING POTENTIOMETER e eere enean 48 FIGURE 16 FACTORY SET DIP SWITCHES eere eene 50 FIGURE 17 CABLE AND
35. IRETY BEFORE USING YOUR BARRETTHAND Following these safety instructions will help prevent user injury and equipment damage As with any piece of robotic equipment it is ultimately up to you to be aware of your surroundings during robot operation The workspace of the BarrettHand whether attached to a robot arm or its lab bench stand should be clearly marked to prevent persons or objects from inadvertently entering the equipment s reach Before attaching the BarrettHand test host robot trajectories to confirm that it will not inadvertently collide with other objects in the workspace NEVER connect or disconnect any electrical cables while the Power Supply is turned on Failure to follow this instruction could impart irreparable damage to the onboard electronics or put you at risk of electrical shock Always plug the Power Supply into a properly grounded wall source Failure to do so could damage the BarrettHand electronics and put you at risk of electrical shock Do not place any part of your body or delicate objects within the grasp of the BarrettHand without first verifying control of the unit and confirming appropriate force levels Do not allow the BarrettHand to be exposed to liquids that may cause electrical short circuits and put you at the risk of electrical shock Keep dirt away from the exposed gear and cable drives located at the joints Do not exceed the load limit of the fingers 2 kg per finger at any point along the
36. Manual version 1 0 1 System Description 1 1 Standard BH8 255 System Components 1 1 1 System Features Thank you for selecting the most versatile robotic hand ever made The BarrettHand is designed as an affordable practical compromise between inflexible industrial grippers and highly dexterous but bulky and expensive research hands The BarrettHand is lightweight and self contained like a gripper but programmable like a dexterous research hand The BarrettHand is multi fingered grasper with the dexterity to secure target objects of different sizes shapes and orientations Even with its low weight 1 18kg and compact form it is totally self contained Integration with any arm is fast and simple by using industry standard serial communications The BarrettHand is ideal for mounting on almost any robot arm due to its compact and lightweight construction Its low mass and short base to graspcenter distance minimize joint loading on the host robot and reduce extraneous arm movements during object reorientation The custom control electronics package is contained entirely within the palm shell reducing electrical wiring to a single cable carrying all communications and motor power 1 1 2 Documentation Barrett Technology provides two different manuals to assist you in learning about the BarrettHand The first manual is the BH8 255 User Manual and contains information about e System components and options e System setup and operation
37. Where MC is the motor command output K is the proportional gain stored in the variable FPG Xn is the position at time n A is the digital filter zero stored in the variable FDZ Xa is the position at time n 1 B is the digital filter pole stored in the variable FIP is the motor command at time n 1 The trapezoidal profile is determined by the acceleration and the maximum velocity set for the motor Each motor has a corresponding acceleration stored in the variable ACCEL 8 bits integer and 8 bits fraction Use the same method for determining the actual acceleration as shown for the command velocity The acceleration variable determines the rate of change of velocity until the maximum Barrett Technology Inc 60 BH8 255 User Manual version 1 0 velocity is reached default value for ACCEL is 1 0 0039 quadrature counts sample time The following equation can be used to determine the actual acceleration A An N t Equation 4 Motor Acceleration Where A is the acceleration in quadrature counts sample time Ag is the acceleration in revolutions second N is 4 Number of lines in the encoder 360 t is the sample time on the hand electronics 2 23E 4 seconds sample time The maximum velocity in quadrature counts sample time is determined by using part of the variables MCV and MOV which are 12 bits integer and 4 bits fraction The maximum velocity is set to the lower 8 bits of the
38. ain LFV Loop Feedback Flag If True RealTime 1 signed byte Velocity feedback block will contain feedback velocit Loop Feedback Variable Actual velocity is divided N A Velocity integer by LFVC to get LFV Coefficient LFS Loop Feedback Flag If True RealTime 1 unsigned Strain feedback block will contain byte strain information Loop Feedback If True RealTime 2 unsigned Absolute Position feedback block will contain bytes absolute position LFDP Loop Feedback Flag If True RealTime 1 signed byte Delta Position feedback block will contain delta position Loop Feedback Variable The actual delta position is N A Delta Position integer divided by this to get Coefficient LFDP Now that all of the flags and variables have been set it is time to begin RealTime control Send the command lt Motors gt LOOP to enter RealTime mode At this point the BarrettHand will respond with a to acknowledge the start of RealTime control It is now up to the host computer to build control blocks and send them to the BarrettHand Example This application uses fingers F1 and F2 and the spread The fingers will receive velocity control information and report strain and delta position The spread will just report delta position relevant coefficients will be set to 1 Set the RealTime flags and variables by using the following commands I2FSET LCV 1 LCVC 1 LCPG 0 LFVOLFS 1 LFAP 0 LFDP 1 LFDPC 1 4FSET LCV 0 LCVC 1 LCPG 0 LFV 0 LFS 0
39. are The BH8 255 System control software consists of the BHControl Interface Application and Manual BH8 255 User Manual latest firmware version and example programs The BHControl Interface is a Windows application that allows you to control the BarrettHand quickly and easily The BHControl Interface can be used to test Supervisory and RealTime control sequences measure communication loop rates demonstrate functionality learn how to write Barrett Technology Inc BH8 255 User Manual version 1 0 and automatically generate code independently based tested algorithms See Section 4 2 for more information on Supervisory and RealTime control and the BHControl Interface Manual for more information on the BHControl Interface The BarrettHand has firmware that resides on the control electronics The firmware requires only ASCII characters sent over a standard serial port You build the character strings to create the desired commands The firmware then interprets the commands sent and controls the motors sets and retrieves parameters or reads and writes to the EEPROM See Section 4 2 for more information on firmware commands and parameters 1 1 8 Maintenance Kit Included in each BarrettHand package is a maintenance kit Use the maintenance kit in accordance with the instructions in Section 5 The maintenance kit includes the following 1 0 mm Hex wrench 27 mm Hex wrench 2 0 mm Hex wrench 2 5 mm Hex wrench Mob
40. arrettHand while the Power Supply is turned on Under no circumstances should the BarrettHand be operated while resting unsecured on a tabletop or any other surface Figure 5 Lab Bench Stand with Wire Strain Relief To secure the BarrettHand to the lab bench stand flip the stand upside down Pass the base ring of the BarrettHand up through the center hole of the stand and retain it with the threaded locking ring provided with your system see Figure 5 Note the alignment of the BarrettHand relative to the wire strain relief clips to ease connection of the BarrettHand Cable Make sure the Power Supply is turned OFF route the BarrettHand Cable through all three cable clips on the lab bench stand and plug it into the BarrettHand Tighten the cable clips to hold the cable in place 3 1 2 Optional Arm Adapter Like the lab bench stand the arm adapter is made to retain the BarrettHand in place and to handle wiring from the hand see Figure 6 The arm adapter however can be designed for mounting on your specific robot arm To mount your BarrettHand on a robot bolt the arm adapter onto the end effector bolt circle Insert the threaded base of the BarrettHand through the hole in the arm adapter shown in Figure 6 paying attention to the indexing tabs in the arm adapter These tabs fit into the mating slots on the base of the BarrettHand Barrett Technology Inc BH8 255 User Manual version 1 0 Secure the BarrettHand by threading the lock
41. ase Decoder 1 1 1 1 1 1 1 1 Figure 20 BarrettHand Controller Block Diagram Barrett Technology Inc 58 BH8 255 User Manual version 1 0 Brushless Motors The BarrettHand utilizes one of the smallest DC brushless servo motors in the world for their torque range Because the motors have no brushes and thus less inherent friction they achieve a better torque mass ratio than typical brushed servos There is also no need to replace worn brushes after the motors have been in service over a period of time Table 6 shows BarrettHand motor properties Table 6 BarrettHand Motor Properties NumberofPoles Peak Torque 5 N cm 8 oz in Motor Constant cm oz in Position Feedback 360 counts rev incremental optical encoder 7 2 Motor Control Two different types of methods are used for controlling individual motors in Supervisory mode Velocity Control and Trapezoidal Profile Control The Velocity Control is used during close and open commands C and O These commands use proportional gain and velocity error to control motors The control velocity in quadrature counts per sample time is 12 bits integer and 4 bits fraction For example Integer Fraction 100 Control Velocity 0000 0000 0110 0100 Binary Integer 0000 0000 0110 6 Fraction 0100 4 16 0 25 100 Control Velocity 6 25 quadrature counts sample time Use the following equation to determine ve
42. cks fully closed Possible Solution 1 Verify there are no objects or other fingers blocking the finger from opening completely 2 The open velocity is too slow Try increasing the open velocity to greater than or equal to 40 and opening the finger 3 Verify the parameter MSG Maximum Strain Gage is greater than the strain gage value SG If the strain gages are not installed set MSG to 256 4 The pretension in the cable is too high Refer to Section 5 1 to set the finger cable pretension properly 5 Set the open velocity greater than or equal to 40 and then initialize the finger 6 Ifthe problem persists contact Barrett Technology 52 Barrett Technology Inc BH8 255 User Manual version 1 0 53 Symptom Finger sticks open Possible Solution 1 2 3 Verify there are no objects or other fingers blocking the finger from closing The close velocity is to slow Try increasing the close velocity to greater than or equal to 40 and closing the finger When the finger is moving the strain gage values exhibit noise that may be greater than the parameter MSG Verify the parameter MSG Maximum Strain Gage is at least 50 greater than the strain gage value SG If the strain gages are not installed set MSG to 256 Set the close velocity to greater than or equal to 40 and then initialize the finger If the problem persists contact Barrett Technology Symptom Finger moves in opposite direction of commanded motion P
43. cs are determined using the following equation Equation 6 Forward Kinematics from Fingertip to World Table 7 is a list of the parameters used to determine the kinematics for each of the fingers These parameters are found in each of the forward kinematics equations Table 7 D H Parameter Values for all Fingers D 25mm To calculate the joint angle before the TorqueSwitch has been activated based on the motor angle use Equation 7 Barrett Technology Inc 67 BH8 255 User Manual version 1 0 8 008 0 0 0 0027 0 0 0 o 0 008 0 0 _ 9 007 0 0 0 0 008 0 o 0 0 0027 0 19 0 0 0 0 0571 0 0 0 0571 Equation 7 Motor to Joint Angle Transform before TorqueSwitch Activation After the TorqueSwitch has been activated the inner link stops moving and all the joint torque is applied to the outer link The joint angle after the TorqueSwitch has been activated based the motor angle can be determined using Equation 8 See 7 6 for information on how to detect TorqueSwitch activation 0 0 0 0 0107 0 0 0 ER 0 0 0 0 0 0 007 0 0 6 0 0 0 0 0 om 0 0 0 0 0 0571 Om 0 0 0 0571 Equation 8 Motor to Joint Angle Transform after TorqueSwitch Activation Equation 8 is only valid for the continuous movement through TorqueSwitch activation Once the finger stops the end tip position cannot be
44. ctor on the back of the Power Supply and into the bottom of the BarrettHand 4 Verify the AC line cord is plugged into a valid power source see 7 6 and into the power outlet on the back of the Power Supply 5 Turn on the Power Supply The main power switch is located on the back panel 6 The BarrettHand is now ready for operation 42 BarrettHand Control This section will explain the command structure to communicate with the BarrettHand The BarrettHand C Function Library incorporates functions that build and send these commands for you However if you choose not to use the C Function Library the BarrettHand expects commands in the following format 4 2 1 Supervisory Control The BarrettHand can be used in either a high level Supervisory mode or a low level RealTime mode Supervisory mode allows you to command individual or multiple motors to close open and move to specific positions You also have access to all of the parameters which are listed in Section 4 2 3 This set of commands is commonly used for most grasping situations If real time control of the motor position velocity or strain is needed use the RealTime control described in Section 4 2 5 Supervisory mode accepts commands from the user program and will not return control of the BarrettHand until the command is finished being processed The BarrettHand expects valid commands and will return a status code for an invalid command or if another problem occurs See Sectio
45. dseieseseseacesessesssesescodscguntencesessedensess 18 3 3 HOSE COMPUTER 19 3 4 INSTALLING BH 8 255 CONTROL SOFTWARE eee eee eee eee eee eese eee eese esee esee esee ases assess eaa 19 3 5 DOWNLOAD FIRMWARE seco o ve ee eins een ese eon ao ee etae e eene ee eee aa bo see ee eese ea Eo E 19 4 BARRETTHAND OPERATION cccsssssssssssssssssccscsssssssccscessssscccscessssssccsscsssssssss 21 4 1 POWER UP SEQUENCE EEN 21 4 2 CONTROL 21 4 21 SUPERVISORY CONTROL EE 21 4 2 22 terree bri ete E ee eise EE YS 22 4 2 3 FIRMWARE 8 1 e ais seen 23 4 2 4 FIRMWARE COMMANDS eene een enne sehen eterna nnne ne teen esser 29 2 2 5 REALTIME We 33 72 6 STATUS CODES S os HERR EEG E ER Re ER E Ve Us 35 4 3 EXAMPLE PROGRAMS istessssesesesocsscsscestuvsessevecssedecnsvesetececessesesesebacesocssecseddenssecoossescesssosses 36 4 3 1 SUPERVISORY MODE EXAMPLE PROGRAM eee eene 36 Barrett Technology Inc BH8 255 User Manual version 1 0 4 3 2 REALTIME EXAMPLE PpoopaM 38 5 MAINTENANC Eivcdsssssccccscssstactitesscaseeticedecacsesscctescssssdcedessssecsecdesieacascsocdesseisccctecveseeecees 41 5 1 FINGER CABLE PRETENSION 41 5 2 FASTENER CHECK
46. e tete ie ta tenta de OE NUS 14 42 AFirmware sas nnna cie ettet ite dvo esee EES 29 ERR uti abus 29 Geeta 29 PE D 29 BUTS TA eats uL 29 BLISTAY ce rate Ee ait ie e Gat HO ee ae Ata reed 29 FLOA D oreren ehana n eae dee As in Bl eat 30 e aad 30 Aas tee ein aia 30 0 30 1031 LOOP WDR eee en eb i EE pa dees te 3 31 31 PGEL e Reihe die ae ache 31 eee tenet eme e E ene a eddies 3 T 31 VERS da et tds d tL e 32 C32 7 32 4 2 3Pirmware parameters sse dee ener irte ie REPRE 23 ACCEDI yb ete eer ee e bre E DE te er ee De 23 61 BAW Diese os e eL T Oe 23 al 23 A ois eae n do Co 23 kregen ete 23 hes ox io eid etu oboe 24 60 iem
47. en clamp finger down Figure 13 Reattaching Fingers after Maintenance 9 Insert and tighten the finger attachment shoulder screw to retain the finger in place as shown in Figure 10 Check the connection to the motor housing to be sure all gaps are closed 5 4 Strain Gages Due to variations in materials manufacturing and external forces the strain gage values may change These changes will affect the zero force reading for each beam differently To maintain consistent results the zero force reading needs to remain constant Each strain gage is equipped with a balancing potentiometer Adjusting the balancing potentiometer will change the strain gage output for that finger Adjust the balancing potentiometer until the no load value is between 100 and 140 Use the following steps to zero the strain gages 1 Initialize the BarrettHand Terminate the spread motor so it can be moved around the palm Issue the T command 3 Remove the Shroud Cover screws shown in Figure 14 Some models of the BarrettHand will have four Shroud Cover screws Remove the Shroud from the finger link Barrett Technology Inc 47 BH8 255 User Manual version 1 0 Shroud Cover Screws Shroud Cover Figure 14 Shroud Removal Run the program Monitor Strain exe This program will continuously sample the strain gage values and print them to the screen Adjust the balancing potentiometer using a small flat head screwdriver until the desired value is
48. es 53 Fin Ger s Mak e tole A 53 Ai ettet equ he ae 52 56 Firmware downlo d 4e a ER ORB E 50 Spread ee EU EE 55 Spread positiOnez oe NAT eet e ER P EHE 57 Strain Gases edicit st ht rente e te eee 51 32 Threaded locking ring ee deg 56 T rgd eSwiteh M ele cee A ese Ee 54 VE 55 V inte edet hd e PE D D ERR eA b 10 W MAE EP 14 Weight ette tutu tente rettet ter ate m nl dette 8 78 AN GHEET ber e eet e hist e rer deeg eed rd tdeo en heed 44 84 Z
49. ich cause it specifically all the geometrical and time based properties of position Lexan A water clear high impact resistant polycarbonate used to make the BarrettHand lab bench stand Pretension The process of adding additional tension to a cable during the assembly process RealTime Mode A control mode of the BarrettHand which allows you to control the motors in real time This mode allows you to monitor position velocity and strain gage values during motion and control the motors during motion RS 232 RS 232 defines the specifications for encoding transmitting receiving and decoding characters RS 232C is the most recent version of the EIA Electronics Industry Association standard for low speed serial communication It defines a number of parameters concerning voltage levels loading characteristics and timing relationships Shoulder Screw A fastener having a boss with a set diameter usually for alignment purposes Spread The patented motion of fingers F1 and F2 about the palm This motion allows the fingers to be positioned around the palm for the best grasp Spur Gears A gear having straight parallel teeth that are perpendicular to the gear s face Supervisory Mode A control mode of the BarrettHand which allows you to issue high level commands to control motion and change parameters The BarrettHand does not accept a new command until the previous command is finished Threaded Locking Ring The
50. ightened with the same amount of torque Excessive torque may cause spread friction 3 Ifthe problem persists contact Barrett Technology 55 Barrett Technology Inc BH8 255 User Manual version 1 0 Symptom threaded locking ring does not fit on the threaded base of the BarrettHand Possible Solution 1 The threaded locking ring has been damaged or is warped Contact Barrett Technology for a replacement part 2 The threads on the base of the BarrettHand have been damaged Contact Barrett Technology for service Symptom fingertip is easy to move and folds backwards Possible Solution 1 The pretension in the cable is too low Refer to Section 5 1 to set the finger cable pretension properly If the problem persists contact Barrett Technology 2 The finger cable is broken Verify this by removing the Shroud Cover see Figure 19 and inspecting the cable The cable should be intact and not broken If the cable is broken contact Barrett Technology Note Some BarrettHand models may have 4 Shroud Cover Screws Shroud Cover Screws Shroud Cover Figure 19 Shroud Cover Removal 56 Barrett Technology Inc BH8 255 User Manual version 1 0 57 Symptom spread fingers and F2 are at different angles around the palm Possible Solution 1 An internal spread gear is damaged and will need to be replaced Contact Barrett Technology Barrett Technology Inc BH8 255 User Manual version 1 0
51. igure 25 Depending on the position of the spread joint and the objects in the grasp the maximum joint motion limits for the finger links may vary The inner link has a maximum joint motion limit of 140 with no object blocking movement and in the full close or open position The outer link O55 has a maximum joint motion limit of 45 when is fully open or closed and there is no object in the grasp as shown in Figure 29 When the spread is in any position other than full open or close the fingers may not have the full range of motion due to interference with other fingers Figure 29 Finger Joint motion limit Range The spread joint has a maximum joint motion limit of 180 with no object blocking movement and all fingers in the full open position If the fingers are partially closed or there is an object in the grasp O4 may not close completely due to finger interference See Figure 30 Figure 30 Spread Joint motion limit Range Appendix Technical Specifications Kinematics Qty Total fingers Fingers which spread Joints per finger Motors per finger Axes of spread motion Motors for spread motion Total axes Total motors Range of Motion Finger base joint 140 Fingertip 45 Finger spread 180 Finger Speed Finger fully open to fully closed 1 0 sec Full 180 finger spread 0 3 sec Position Sensing Type optical i
52. il 1 Lubricant in syringe e Lubricant applicators e Torque wrench 2 0 mm Hex adapter for Torque wrench 12 Barrett Technology Inc BH8 255 User Manual version 1 0 1 2 System Options 1 2 1 Arm adapter Barrett Technology can provide an arm adapter for any make or model robot This lightweight arm adapter is made to work with the end effector bolt pattern on your robot allowing quick easy mounting and wire management for a BH8 255 System The arm adapter is bolted to the end of the robot arm and the BarrettHand is secured to the arm adapter with its standard threaded locking ring see Figure 4 The arm adapter is also equipped with an anti rotation feature to prevent rotation during operation Figure 4 Arm adapter 1 2 2 Library BarrettHand C Function Library is a helpful tool for programming the BarrettHand using the C language on IBM compatible PC s without having to manage serial communication and timing issues The library contains easy to use functions that permit the use of Supervisory and RealTime commands in software routines developed by the end user All of the functions are available when the library is linked to the program The C Function Library also includes a manual that describes all of the functions in detail and gives examples Barrett Technology Inc BH8 255 User Manual version 1 0 one object and use it for all communications The library uses a sophisticated multithreaded
53. in materials 140 120 100 80 High Limit Low Limit 60 Example Strain Gage 40 20 Delta Strain Gage Values 0 0 245 0 49 0 735 0 98 Torque About Joint 2 N m Figure 24 Strain Gage Torque Curves Note Barrett Technology uses a digital force gage to apply the force perpendicular to the fingertip The force is then converted to a torque 7 5 Kinematics The kinematics for the BarrettHand were determined using the Denavit Hartenberg notation described in Introduction to Robotics Mechanics and Control 2 Edition John J Craig Each finger is considered its own manipulator and is referenced to a world coordinate frame in the center of the palm Use the forward kinematics calculated in this section to determine fingertip position and orientation with respect to the palm The following homogeneous transform equation is used to determine the transforms between axes k and k 1 Barrett Technology Inc 66 BH8 255 User Manual version 1 0 SsO 0 ak S CO COCA 50 e S D I e 0 0 0 1 Equation 5 Homogeneous Transform Between k 1 and kj Where distance from 2 to Zk measured along 04 1 angle between Zx to Zk measured about dk distance from to xi measured along zi angle between to xy measured about Zk 0 50 sin O The forward kinemati
54. ing ring included with your system onto the base of the BarrettHand The BarrettHand Cable is extremely flexible and should be routed close to the center of each revolute joint and along the axis of travel for prismatic joints Mount the cable clips to a flat dry and clean surface Clean cable clip attachment areas with alcohol before attaching Verify the Power Supply is turned OFF then route the BarrettHand Cable through the cable retaining clips on the robot and the arm adapter and plug into the BarrettHand and the Power Supply Tighten the cable clips to hold the cable in place Figure 6 Installing an Arm Adapter 3 2 Electrical Connections After mounting the BarrettHand according to Section 3 1 you should connect the electrical cables required for operation Check the Power Supply to confirm that it is turned OFF e Verify the Power Supply is on a flat stable surface e Plug the free end of the BarrettHand Cable into the female 15 pin D sub connector on the back of the Power Supply Plug the serial cable into computer s serial port usually COMI 18 Barrett Technology Inc BH8 255 User Manual version 1 0 e Plug the other end of the serial cable into the female 9 pin D sub connector on the back of the Power Supply Barrett Technology supplies a standard 3 meter straight through serial cable but you may purchase a longer cable if desired Connect the AC line cord to the socket on the back panel
55. led to the geared servo motor pinion In this state the ratios of motor position to joint position for the 1 and 2 finger joints are 93 75 1 and 125 1 respectively When a finger opens against its motion stop the threaded spur gear is tightened against the Belleville spring washers with a known motor torque thereby setting the threshold torque for disengaging the spur gear If the inner finger link while closing contacts a target object of sufficient stiffness to increase the torque in the gear train above the threshold torque the clutch will disengage from the Belleville spring washers Barrett Technology Inc 62 BH8 255 User Manual version 1 0 When the clutch is disengaged the threaded spur gear free wheels on the threaded shaft allowing the motor pinion to turn without inducing motion in the inner link Instead only the smaller spur gear solidly fixed to its shaft is driven This fixed spur gear actuates the worm gear drive for the fingertip Thus when the clutch is disengaged the inner finger link remains motionless while the fingertip continues to move allowing the fingers to form fit around any shape The minimum finger open velocity needed to reset the TorqueSwitch is 40 Barrett Technology does not guarantee proper operation of the TorqueSwitch unless the open velocity is at least 40 If a slower velocity is used the finger may exhibit premature breakaway characterized by only the fingertip closing during a
56. lem persists contact Barrett Technology Symptom Firmware will not download onto BarrettHand Possible Solution 1 2 2 50 Verify all connections secure to the Power Supply BarrettHand and computer Verify the Power Supply is turned on Reset the BarrettHand by pressing the red Reset switch on the back of the Power Supply and open a new session of the BHControl Interface Verify the dip switch on the BarrettHand CPU board shown in Figure 16 are all set in the OFF position The dip switch bank is located on the exposed circuit board under the threaded base ring of the BarrettHand These switches are preset to the correct positions by the factory but should be verified If the problem persists contact Barrett Technology 7 wun E77 fe Figure 16 Factory Set Dip Switches Barrett Technology Inc BH8 255 User Manual version 1 0 Symptom Initial strain gage values do not fall within specified range Possible Solution 1 The finger cable pretension is not adjusted properly Refer to Section 5 1 for instructions on how to adjust 2 The strain gage balancing potentiometer needs to be readjusted Refer to Section 5 4 for instructions on how to adjust 3 Verify the cable is riding on the idler pulley see Figure 17 4 Verify idler pulley rotates freely on the shoulder screw The shoulder screw should not be tightened against the idler pulley If so contact Bar
57. locity in revolutions per second V N t Equation 1 Velocity Conversion 2 Encoder feedback from two channels allows four times the number of motor positions to actual lines on the encoder Barrett Technology Inc 59 BH8 255 User Manual version 1 0 Where V is the velocity in quadrature counts sample time is the velocity in revolutions second N is 4 Number of lines in the encoder 360 quadrature counts revolution t is the sample time on the hand electronics 2 23E 4 seconds sample time Velocity Control uses proportional gain and velocity error to control the motor command described in Equation 2 When the joint links contact an object or joint stop and have no movement for a pre specified amount of time stored in the TSTOP parameter the motors will stop commanding a velocity MC 5 Y 4 Equation 2 Velocity Control Where is the motor command output K is the proportional gain stored in the variable FPG Y is Command Velocity Actual Velocity The second method of control is called Trapezoidal Profile Control and is used during move position commands IO IC and M This mode moves the motor to the desired position and returns an error if the motor does not reach the position within the number of encoder counts stored in the parameter MPE The following equation is used to determine the motor command Equation 3 Trapezoidal Profile Control
58. me feedback block contains feedback velocity FALSE does not contain TRUE does contain TRUE The size of the feedback velocity should be signed byte The actual velocity is LFC LFVC LFVC Actual velocity is divided by feedback velocity coefficient LF VC to determine LFV 0 255 1 Notes On the host computer the actual velocity of the motors is equal to LFV Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes LFVC MCV This parameter defines the maximum close velocity 0 255 35 Spread 65 Fingers See Section 7 2 for more information on velocity MOV This parameter defines the maximum open velocity 0 255 35 Spread 55 Fingers The minimum velocity required to reset the TorqueSwitch and open and close the fingers is 40 See Section 7 2 for more information on velocity Barrett Technology Inc 26 BH8 255 User Manual version 1 0 Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes MPE Maximum position error allowed for a commanded position 0 30 000 Grasp 25 Spread 25 If the final position 15 not within MPE encoder counts of the desired position then the hand will return an error MSG This parameter defines the maximum strain gage value before the motor is stopped 0 256 256 Setting the value to 256 indicates that the
59. n FALSE does not contain TRUE does contain TRUE Notes The size of the feedback absolute position should be an unsigned 2 byte Parameter Purpose Values Default word LFDP This flag specifies if the RealTime feedback block contains the feedback delta position FALSE does not contain TRUE does contain FALSE Notes The size of the feedback delta position should be signed byte Parameter Purpose Values Default LFDPC The actual change in position is divided by feedback delta position coefficient LFDPC to determine LFDP 0 255 1 Notes Delta position is the change in position from the last reported position and is limited to one signed byte The current position is read and compared to the last reported position The difference is divided by the RealTime variable LFDPC clipped to a single signed byte and then sent to the host The value sent to the host should be multiplied by LFDPC and then added to the last reported position Barrett Technology Inc 25 BH8 255 User Manual version 1 0 Parameter Purpose Values Default LFS This specifies if the RealTime feedback block contains the feedback strain gage value FALSE does not contain TRUE does contain TRUE Notes The size of the feedback strain gage value should be 1 unsigned byte Parameter Purpose Values Default Notes Parameter Purpose Values Default LFV This specifies if the RealTi
60. n 4 2 6 for more detailed information on status codes When the command is finished being executed all status codes and requested information have been sent the hand will return the command prompt gt At this point you can send another command Barrett Technology Inc BH8 255 User Manual version 1 0 4 2 2 Structure Firmware resides on the BarrettHand and interprets the commands it receives This command structure allows you to build the desired command easily The format is as follows lt Motor gt lt Command gt lt Parameter gt lt Value gt Following is a list of the lt Motor gt prefixes Table 2 Motor Prefixes No Motor Specified gt Finger Finger F2 Finger Spread see the Firmware Parameter EN in Section 4 2 3 Note Any combination of motor prefixes can be used together to produce the desired result Example 12 lt Command gt lt Parameter gt lt Value gt will activate Fingers F1 and F2 See Sections 4 2 3 and 4 2 4 for parameter value and command information 22 Barrett Technology Inc BH8 255 User Manual version 1 0 4 2 3 Firmware Parameters Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes ACCEL Acceleration value for position control 0 32767 Grasp 1
61. ncremental encoder Resolution 0 008 at the finger base joint 17 500 encoder counts full finger open to full close Weight BarrettHand 1 18 kg 2 60 Ib Optional Arm Adapter 0133 0 2 kg 0 4 Ib additional Payload 2 0 kg 4 4 Ib per finger at tip Motor Type Samarium Cobalt brushless DC servo motors Mechanisms Worm drives integrated with patented cable drive and TorqueSwitch Power Requirements Single phase AC electrical outlet with ground Load 500 W Phases Single Voltage 120 240 10 VAC Frequency 50 60 Hz Power Supply Location dry stationary surface Size H W D 200 x 200 x 300 mm 7 5 x 7 5 x 12 in Weight 5 kg 11 Ib Cables 3 meter continuous flex cable 8mm diameter BarrettHand Cable 3meter serial cable AC line cord Dimensions 12501 ke 317 52 3 898 E 3 359 85 31 5197 132 307 3 386 M86 1 25 thd 7 80 Barrett Technology amp Inc Figure 31 BarrettHand Dimensions Available Options B029A Strain gage Fingertip Torque Sensors for all three fingers B0133 Arm Adapter with custom bolt circle B0111 C Function Library B01C3 Subscription Service US Patents 5501498 5388480 4957320 Appendix B FAQ QI Al 02 2 What type of finger motions are possible with the BarrettHand and what servos and mechanisms are used to co
62. nsion applied through Barrett Technology s patented cable tensioning mechanism When the pretension becomes too loose the fingertip will not be able to hold a secure position relative to its finger link This looseness in cable tension allows movement of the fingertip with no movement of the motor The torque sensor if installed will also exhibit hysteresis and will not follow the desired torque curves if the pretension is too low When the pretension becomes too loose you should apply additional pretension by turning the tensioner screw located on the back of each Joint 2 housing clockwise with a 2 mm hex driver as shown in Figure 7 Joint 2 Tensioner Wrench Figure 7 Pretensioning the Tendon Cable To increase the cable to the proper pretension turn the 2 mm hex wrench clockwise until the applied torque reaches 15 in oz Barrett Technology suggests Barrett Technology Inc 41 BH8 255 User Manual version 1 0 using the supplied torque wrench with an adapter for the 2 mm hex wrench to assure proper pretension The tendon is properly tensioned when all loose slack has been removed and you can feel the direct connection of the fingertip to its drive gears DO NOT OVER TIGHTEN THE TENDON The pretensioning mechanism is stronger than the tendon and is capable of snapping it if over tightened Excessive pretension will change the frictional properties in the finger drives and may reduce the finger s range of motion 5 2
63. ntrol filter 0 255 Grasp 200 Spread 100 Notes See Section 7 2 for more detailed description of how FPG affects motion Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes HOLD Specifies if a motor should hold position when idled TRUE hold position FALSE do not hold position Grasp FALSE Spread TRUE Because the fingers are not backdrivable when the motors are idled they will not be able to move freely However because the spread is backdrivable it requires this parameter be TRUE to hold its position when idled LCPG This flag specifies if the RealTime control block contains control proportional gain FALSE does not contain TRUE does contain FALSE Motor command LCPG 4 Control Velocity Actual Velocity Barrett Technology Inc 24 BH8 255 User Manual version 1 0 Parameter Purpose Values Default Notes Parameter Purpose Values Default Notes Parameter Purpose Values Default LCV This flag specifies if the RealTime control block contains control velocity FALSE does not contain TRUE does contain TRUE The size of the control velocity should be 1 signed byte LCVC LCV is multiplied by the control velocity coefficient LCVC to determine the control velocity 0 255 1 Control velocity LCV LCVC LFAP This specifies if the RealTime feedback block contains the feedback absolute positio
64. ntrol them The BarrettHand has 3 identical curling 2 joint fingers each with its own built in independent high performance brushless motor drive A patented TorqueSwitch mechanism then channels torque from the motor to the two joints depending on 1 TorqueSwitch level set for that particular grasp and 2 The joint torque status In its full open state each finger s inner link surface is almost parallel with the palm plate while the outer finger link is curled inward by 45 degrees When a finger is commanded to close under velocity or position control the links move according to the transforms in Equation 7 the resulting motion will be curling to promote form closure before a grasp contact is initiated If the outer fingertip makes first contact with an object it develops full force against the object until no motion is detected at which point the motor current may be removed since the finger joints become mechanically locked However if the inner finger link makes first contact the motor applies the torque to both links until the TorqueSwitch level is reached At this instant the inner link is locked into position mechanically and all motor torque is shunted to the outer link which stops only at motor stall torque The net result is highly effective grasping The patented finger spread motion has two opposable fingers and one fixed finger To minimize the number of motors and thereby the weight bulk heat power
65. nts oe Palm Spur Gear Lube points Finger Worm Gear Lube Points Finger Spur Gear Lube Points Figure 9 Lubricant Application Points Lubricating the finger spur gears requires caution because you must remove each finger from the palm assembly to access this application point Read all steps below before conducting this maintenance It is best to lubricate only one finger at a time 1 Open all fingers on the BarrettHand completely Barrett Technology Inc 44 BH8 255 User Manual version 1 0 2 Shutdown the Power Supply disconnect the BarrettHand Cable from the BarrettHand 3 Locate and remove the finger attachment shoulder screw that holds the finger to its motor housing The screw location is shown in Figure 10 Figure 10 Finger Attachment Screw Location 4 Gently tilt the finger slightly forward and lift the alignment teeth out of their slots as shown in Figure 11 If joint torque sensor option is installed BE CAREFUL not to damage the gold plated electrical contact pins when disengaging the teeth 5 Once the teeth are disengaged move the finger away from its motor along a straight line perpendicular to the motor s face Do not twist or rock the finger when removing or attaching it Barrett Technology Inc 45 BH8 255 User Manual version 1 0 Pull Finger Away from Motor Face Lift Alignment Teeth out of Slots Open a Small Gap 0
66. on 1 0 close 00 0 00 close 00 0 00 bh RTSetVelocity 3 value the time is greater than 6 seconds then stop controlling hand in RealTime terminate 0 lt int var 0 1 gt 6000 00 Increment iterations Nt Send all updated control parameters to the hand bh RTUpdate Exit RealTime mode bh RTAbort if _kbhit getch return 1 else return 0 Main function initialize execute void main void printt Initialization ast Initialize printf Done n PrepareRealTime printf RealTime Loop if RunRealTime printf Interrupted n return printf Done without interruption n 40 Barrett Technology BH8 255 User Manual version 1 0 5 Maintenance 5 1 Finger Cable Pretension The second joint in each finger is driven by a brushless servo motor through a stainless steel cable that acts like a tendon transmitting torque from a pulley at the base of the finger out to a pulley at the second joint If you have purchased the joint torque sensor option the tension in the tendon is used to determine the torque at the second joint Because low backlash and accurate torque measurements are desirable you should periodically check that each tendon has the proper amount of prete
67. ossible Solution l There is an encoder feedback problem Reinitializing the finger should solve the immediate problem It is likely this behavior will repeat in the future contact Barrett Technology Barrett Technology Inc BH8 255 User Manual version 1 0 Symptom TorqueSwitch does not activate properly prohibiting the fingertip from forming a complete grasp around an object Possible Solution 1 The close velocity is too slow Increase the close velocity greater than or equal to 40 2 Reinitialize the finger this may reset the TorqueSwitch M 3 Ifthe BarrettHand has been inactive for an extended period the TorqueSwitchTM may need to be manually activated Hold the inner link such that it will not move Insert a 2 mm hex wrench into the Joint 2 Drive Access hole seen in Figure 18 and turn clockwise Continue to drive Joint 2 until the fingertip is moving and the inner link is stationary Remove the 2 mm hex wrench and reinitialize the finger 4 Ifthe problem persists contact Barrett Technology Joint 2 Drive Access Joint 1 Drive Access Figure 18 Manual TorqueSwitch Activation 54 Barrett Technology Inc BH8 255 User Manual version 1 0 Symptom actual velocities of the fingers are different although commanded velocities are the same Possible Solution 1 Verify all of the finger velocity and filter parameters are the same MCV MOV FPG FDZ FIP ACCEL 2 Each finger ha
68. parameter DS Barrett Technology Inc BH8 255 User Manual version 1 0 31 Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes IO Incremental open of specified motors N A The increment size is defined in the parameter DS LOOP Enters RealTime mode for the specified motors N A See Section 4 2 5 for more information on how the RealTime mode functions M Move the specified motors to specified position Motor position 0 20000 If no position is given it will move to the value stored in DP O Opens specified motors N A None PGET Gets the parameter specified TMP Does not take motor prefixes RESET Resets the BarrettHand and loads all of the saved parameters from EEPROM N A Does not take motor prefixes The motors need to be reinitialized before commanding motion after using this command See the command FSAVE for parameter information T Stops actuating the motors N A None Barrett Technology Inc BH8 255 User Manual version 1 0 Command VERS Function Greeting message shows the version number and the company contact information Parameters Notes None Command lt Command gt Function
69. pped with a threaded base for easy mounting The threaded base is fully compatible with the BarrettArm and with the optional arm adapter can be mounted on virtually any robot This allows for easy installation and maintenance of the BarrettHand F2 2 around the Palm Threaded Ring for Quick Connection TorqueSwitch Shifts Torque to Appropriate Finger Joint Onboard Control Electronics Package in Palm Shell F3 Figure 1 BarrettHand Barrett Technology Inc BH8 255 User Manual version 1 0 1 1 4 Power Supply The Power Supply shown in Figure 2 provides all DC motor bus voltage electronic component logic voltage and passes RS 232 commands from the host computer to the control electronics in the BarrettHand palm shell This Power Supply auto switches for international voltage standards and contains built in surge protection shielding an attached BarrettHand from surges in the AC line voltage The three connections to the Power Supply are the AC line voltage RS 232 connection from the host computer and a connection for carrying signal and power to and from the BarrettHand The Power Supply is also equipped with a button to reset the BarrettHand and two LED s indicating the presence of proper voltage levels The red LED when illuminated indicates valid 36 V motor power The green LED when illuminated indicates valid 5 V logic power Refer to Figure 2 for a detailed picture of
70. r if result bh Baud 9600 Error if result bh InitHand Error dddddddddddddddddddddddddddddddddddddddddddddddddddddddddd Execute commands return 1 if interrupted with a key Barrett Technology Inc 36 BH8 255 User Manual version 1 0 int Execute void printf Press Any Key to Abort Initializes all motors if result bh InitHand 1235 Error if _kbhit getch return 1 Closes fingers Fl F2 and if result bh Close 123 Error if _kbhit getch return 1 Opens fingers Fl F2 and if result bh Open 123 Error if _kbhit getch return 1 return 0 Main function initialize execute void main void printf Initialization Initialize printf Done n printf Executing Execute p Barrett Technology Inc BH8 255 User Manual version 1 0 rintf Done without interruption n 37 4 3 2 RealTime Mode Example Program The following program is an example that shows how to program the hand in RealTime mode using the C Function Library The code was generated using the BHControl Interface and compiled using Microsoft Visual C v6 0 This program will close finger one and starts closing finger two when finger one reaches position 5000 Finger three starts closing when finger two reaches position 5
71. reached The balancing potentiometer requires very small adjustments due its sensitivity Apply as little pressure as possible on the balancing potentiometer during adjustment See Figure 15 Strain Gage Beam Balancing Potentiometer Figure 15 Balancing Potentiometer Barrett Technology Inc 48 BH8 255 User Manual version 1 0 6 After balancing the strain gage exit the Monitor Strain exe program put the shroud and shroud cover back on and secure the screws Be careful not to touch the strain gage or damage any of the electrical wiring when replacing the shroud Barrett Technology Inc BH8 255 User Manual version 1 0 49 6 Troubleshooting Symptom host computer will not communicate with the BarrettHand Possible Solution 1 2 3 Verify all connections secure to the Power Supply BarrettHand and computer Verify the Power Supply is turned on Firmware may no longer be valid Try downloading the firmware according to Section 3 5 Host computer baud rate and BarrettHand baud rate may be set to different rates Close the BHControl Interface and reset the BarrettHand by pressing the red Reset button on the back of the Power Supply Restart the BHControl Interface and try initializing again The communications port selected is being used by another program Close all other programs that use the selected communications port Reset the BarrettHand and restart the BHControl Interface If the prob
72. removable circular ring at the base of the BarrettHand that is used to mount the hand such as the Lexan test stand or the arm adaptor TorqueSwitch The patented coupling between the fingers two joints This coupling allows the use of one motor to control two joints When the inner link encounters an object with sufficient force it will stop while the outer link continues to close around an object See Section 7 3 1for more information on the theory of operation Worm Gears A long cylindrical gear with skewed teeth making it capable of driving other gears INDEX A 13 17 78 19 82 EE e EE 14 RC 16 24 65 80 82 EE 33 ERR EE 23 33 50 58 EIER EA 61 62 82 BHControl Interface 11 19 36 38 BHControl Interface Initialize eu beweege ee MAER E Es 19 Start Download 19 C Functiomn Eibraty 5 eR UR Seed 13 21 36 38 iss et Ne cie Net eto dii hee be 62 Command struct re 3515 3 S RH ON ENT e d Ns 22 Communications s ecrit ege 14 21 58 Sous PE 19 Disk Spaces cos e ete Re aeg tette n Ree deed 19
73. rett Technology 5 Ifthe problem persists contact Barrett Technology Top Cable Foil Strain Idler Pulley Gages Bottom Idler Pulley Cable Shoulder Screw Figure 17 Cable and Idler Pulley 51 Barrett Technology Inc BH8 255 User Manual version 1 0 Symptom strain gage values do not follow the expected strain gage curves shown in Figure 24 while grasping Possible Solution 1 The finger cable pretension is not adjusted properly Refer to Section 5 1 for instructions on how to adjust 2 The strain gage balancing potentiometer needs to be readjusted Refer to Section 5 4 for instructions on how to adjust 3 Verify the cable is riding on the idler pulley see Figure 17 4 Verify idler pulley rotates freely on the shoulder screw The shoulder screw should not be tightened against the idler pulley If so loosen shoulder screw shown in Figure 17 so the idler pulley will move with cable motion 5 Ifthe problem persists contact Barrett Technology Symptom Only the fingertip closes when the entire finger should close Premature Breakaway Possible Solution 1 Verify there is no object blocking the inner link from moving 2 The finger was not opened with the minimum opening velocity of 40 Set the open velocity greater than or equal to 40 Initialize the finger having the problem The finger should now close properly 3 Ifthe problem persists contact Barrett Technology Symptom Finger sti
74. s an optional Joint Torque sensor for each finger The Joint Torque sensor measures the torque about the outer joint on each finger see Figure 23 The Joint Torque sensor is comprised of a flexible beam with four foil strain gages applied and wired in a Wheatstone Bridge configuration When a force is applied to the fingertip Force A the torque is measured by the amount of deflection in the beam The beam deflection is proportional to the difference in cable tension which translates to a force on the pulley attached to the flexible beam Force B The flexing in the beam creates a measurable voltage change in the Wheatstone Bridge This difference in voltage is conditioned amplified converted and available to you in digital form Force A N Foil Strain Gages Top Cable Bottom Cable Force B Figure 23 Strain Gage Joint Torque Sensor The gages are adjusted before leaving the factory and should exhibit a no load value between 100 and 140 Ifthe gage values do not fall within the specified range see Section 5 4 Barrett Technology Inc 65 BH8 255 User Manual version 1 0 Applying a force at a distance perpendicular to the fingertip will produce a torque about Joint 2 see Figure 23 Use the BHControl Interface to determine digital torque values If the torque curve measured does not approximate the torque curve shown in Figure 24 see Section 6 The torque curves for each finger will be different due to the variations
75. s slightly different friction due to manufacturing tolerances resulting in different actual velocities for the same commanded velocity Lubricating the high friction fingers will help reduce the friction and increase the velocity See Section 5 3 for lubrication instructions 3 The control algorithm used on the BarrettHand does not force the fingers to move at the same velocity see Section 7 2 It is possible to move fingers at the same velocity however it will require a more sophisticated control algorithm implemented in RealTime mode 4 Ifthe problem persists contact Barrett Technology Symptom Fingers will not close completely Possible Solution 1 Verify there are no objects or other fingers blocking the finger from closing completely 2 Verify the parameter MSG Maximum Strain Gage is greater than the strain gage value SG If the strain gages are not installed set MSG to 256 3 The pretension in the cable is too high Refer to Section 5 1 to set the finger cable pretension properly 4 Ifthe fingers were removed the finger angle may be set incorrectly Verify finger angle is correct by following the directions on disconnecting and reattaching fingers in Section 5 3 5 Ifthe problem persists contact Barrett Technology Symptom spread motion has excessive friction Possible Solution 1 Lubricate the spread motor gears as shown in Section 5 3 2 Ifthe palm screws have been reinstalled verify all screws are t
76. the Power Supply 1 Red LED 36 V monitor 2 Green LED 5 V monitor 3 AC line cord connector 4 Power Switch 5 Reset Switch 6 15 pin female BarrettHand Cable connector 7 9 pin female Serial Cable connector Figure 2 BarrettHand Power Supply 10 Barrett Technology Inc BH8 255 User Manual version 1 0 1 1 5 Lab Bench Stand The bench mount stand for the BarrettHand shown in Figure 3 is ideal for use in a laboratory environment The durable Lexan stand comes complete with cable management clips and mounting feature to hold your BarrettHand unit securely on any flat surface Non slip rubber feet keep the stand from sliding during testing and programming Figure 3 Lab Bench Stand 1 1 6 Electrical Cables All necessary electrical cables are included in the basic BH8 255 System An AC line cord connects the Power Supply to a wall source 120 240 10 VAC A serial cable connects the Power Supply and the host computer to establish the RS 232 communication link The BarrettHand Cable connects the Power Supply to the BarrettHand supplying communications logic power and motor power This cable is extremely flexible allowing the BarrettHand to be used on any robot with minimal effect on robot performance Use the included set of twelve adhesive guide clips for cable management Since the control hardware resides inside the BarrettHand itself no other electrical cabling is required 1 1 7 Control Software and Firmw
77. tt Technology Inc BH8 255 User Manual version 1 0 28 29 4 2 4 Firmware Commands Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Command Function Parameters Notes Closes specified motors N A None ERR Returns a description of the status code specified Status code numbers Does not take motor prefixes See Section 4 2 6 for more information on status codes FDEF Loads the factory default values of the parameters from EEPROM into memory N A This command loads the following parameters MCV MOV DS MSG DP FPG FIP FDZ EN SGFLIP ACCEL MPG TSTOP HOLD LCV LCVC LCPG LFV LFVC LFS LFAP LFAP LFDPC See Section 4 2 3 for the default parameter values FGET Gets the specified parameters MOV MCV MSG DS DP LCV LCVC LCPG LFV LFVC LFS LFAP LFDP LFDPC FPG FIP FDZ ACCEL MPE TSTOP HOLD SGFLIP EN BAUD S P SG See Section 4 2 3 for more information on firmware parameters FLISTA Lists all of parameters and their read write status N A Does not take motor prefixes FLISTAV Lists all of the present parameter values N A The parameters are listed in the same order they are displayed by the command FLISTA This command does not take motor prefixes Barrett Technology Inc
78. ual version 1 0 4 3 Programs 4 3 1 Supervisory Mode Example Program The following program is an example that shows how to program the BarrettHand in Supervisory mode using the C Function Library The code was generated using the BHControl Interface and compiled using Microsoft Visual C v6 0 This program initializes the BarrettHand and then opens and closes the grasp LALALA AAAI Automatically Generated C Cod BHand Control Center Version 1 0 Supervisory Mode include lt stdio h gt include lt stdlib h gt include lt math h gt include lt conio h gt include BHand h BHand bh Handles all hand communication int value Hand parameter obtained with Get command int result Return value error of all BHand calls P TTT PPP P PP TTT TTT TTT TATA ATT Error Handler called whenever result 0 void Error void printf ERROR d n s n result bh ErrorMessage result exit 0 Initialize hand set timeouts and baud rate void Initialize void if result bh InitSoftware 1 THREAD PRIORITY TIME CRITICAL if result bh ComSetTimeouts 0 100 15000 100 5000 Erro

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