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BLDC Motor with Speed Closed Loop and DC-Bus

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1. 4000 commutations per second Situation Average Time Load PWM Period 2 Motor Speed 300 RPM 31 9 45 4 120 commutations per second Motor Speed 10000 RPM 33 5 45 4 7 Summary and Conclusions This application note provides the user with a description of the demo application 3 phase BLDC motor with speed closed loop The application also demonstrates usage of the eTPU module on the PowerPC MPC5554 which results in a CPU independent motor drive Lastly the demo application is targeted at the MPC5554 family of devices but it could be easily reused with any device that has an eTPU 8 References Table 5 References MPC5554 Reference Manual MPC5554RM MPC5554DEMO User s Manual MPC5554DEMO EVBUM MPC5550 Quick Start User s Manual P T 33395 Evaluation Motor Board Designer Reference Manual DRM33395 D Nn Interface Board with UNI 3 User s Manual Pittman s Motors web http www pittmannet com FreeMASTER web page http www freescale com search keyword FreeMASTER 8 Enhanced Time Processing Unit Reference Manual ETPURM 9 Using the Hall Decoder HD eTPU Function AN2841 10 Using the Speed Controller SC eTPU Function AN2843 11 Using the DC Motor Control PWM eTPU Functions AN2480 12 Using the Break Controller BC eTPU Function AN2845 BLDC Motor with Speed Closed Loop and DC Bus Break
2. 1 omega actual _ __ _ revolution_period scaling factor where omega_actual fract24 is the actual angular speed as a fraction of the maximum speed range 1 is expressed as fractional value 0x7FFFFF revolution_period number of TCR ticks is the period of one electrical revolution scaling factor is pre calculated using the following equation scaling factor __ 60 etpu_ter_freq x omega max pole pairs where etpu_tcr_freq Hz is a frequency of the internal eTPU timer TCR2 used omega max RPM is a maximal speed range pole _pairs is a number of motor pole pairs The internal eTPU timer TCR2 frequency must be set so that the calculation of omega _actual both fits into the 24 bits arithmetic and its resolution is sufficient 5 3 Definition of Commutation Tables The PWM phases are commuted on each of the Hall signal transitions This is internally done by applying two commutation commands that are associated with the particular Hall signal transition The first command turns a phase off and the second turns another phase on Such pairs of commutation commands must be defined for each Hall signal transition low high and high low on each phase and for both motor directions These definitions are located in etpu_app_ bldcmhs11 c file Each commutation command is a 32 bit word that consists of the following 8 bit parts e Channel number of the PWM phase base channel e New base channel commutati
3. eTPU controls a speed closed loop The actual motor speed is calculated based on the revolution period and compared with the required speed provided by the CPU and passed through a ramp The speed PI control algorithm processes the error between the required and actual speed The PI controller output is passed to the PWM generator as a newly corrected value of the applied motor voltage BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor System Concept Figure 10 The Application and FreeMASTER Screen 3 2 1 User Interface The application is interfaced by the following e ON OFF switch on the interface board with UNI 3 e Up down buttons on the interface board with UNI 3 or FreeMASTER running on a PC connected to the MPC5554DEMO via an RS232 serial cable The ON OFF switch affects the application state and enables and disables the PWM phases When the switch is in the off position no voltage is applied to the motor windings When the ON OFF switch is in BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 11 System Concept the on position the motor speed can be controlled either by the up and down buttons on the interface board or by the FreeMASTER on the PC The FreeMASTER also displays a control page real time values of application variables and their time behav
4. According to Reference 13 the ASDC maximum eTPU load takes 42 80 eTPU cycles both the first and then the second edge processing is performed The ASDC function processing is executed every PWM period According to Reference 12 the BC maximum eTPU load per one update in slave PWM switching mode is 64 eTPU cycles and the BC maximum eTPU load per one PWM edge is 20 eTPU cycles The BC update is performed every 16 PWM periods PWM frequency of the DC bus break control signal is 5 kHz which means that the BC PWM update is performed every 4 PWM periods The values of eTPU load by each of the functions are influenced by compiler efficiency The above numbers are given for guidance only and are subject to change For up to date information refer to the information provided in the latest release available from Freescale The peak of the eTPU time load occurs when both the speed controller calculation and a Hall signal transition are processed within one PWM period This peak value must be kept below 100 which ensures that all processing fits into the PWM period no service latency is longer than the PWM period and thus the generated PWM signals are not affected BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 47 Summary and Conclusions Table 4 shows the eTPU module time load in several typical situations Table 4 eTPU Time Load Peak Time Load Within
5. 16 ES_ETPU_PWMMDC_DUTY_NEG lt lt 24 phaseA_commut_cmds lh_d_l PWM_phaseB_channelt EFS_ETPU_PWMMDC_ON_ACTIVE_HIGH lt lt 8 EFS_ETPU_PWMMDC_ON_ACTIVE_LOW lt lt 16 FS_ETPU_PWMMDC_DUTY_POS lt lt 24 This way all commutation commands can be defined BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 46 Freescale Semiconductor 6 Microprocessor Usage Microprocessor Usage Table 3 shows how much memory is needed to run the application Table 3 Memory Usage in Bytes Memory Available Used FLASH external 2M 29 324 RAM 64K 3 096 eTPU code RAM 16K 4920 eTPU data RAM 3K 680 The eTPU module usage in terms of time load can be easily determined based on the following facts According to Reference 14 the maximum eTPU load produced by PWM generation is 946 eTPU cycles per one PWM period The PWM frequency is set to 20 kHz thus the PWM period is 3200 eTPU cycles eTPU module clock is 64 MHz half of the 128 MHz CPU clock According to Reference 8 the speed controller calculation takes 244 eTPU cycles The calculation is performed every second PWM period According to Reference 9 the processing of one Hall signal transition including the commutation takes 308 eTPU cycles The Hall signal transitions come asynchronously to the PWM periods Six transitions are processed per one electrical motor revolution
6. designed for timing control I O handling serial communications motor control and engine control applications It operates in parallel with the host CPU The eTPU processes instructions and real time input events performs output waveform generation and accesses shared data without the host CPU s intervention Consequently the host CPU setup and service times for each timer event are minimized or eliminated The eTPU on the MCP5554 microcontroller has two engines with up to 32 timer channels for each In addition it has 16 Kbytes of code memory and 3 Kbytes of data memory that stores software modules downloaded at boot time and that can be mixed and matched as required for any specific application The eTPU provides more specialized timer processing than the host CPU can achieve This is partially due to the eTPU implementation which includes specific instructions for handling and processing time events In addition channel conditions are available for use by the eTPU processor thus eliminating many branches The eTPU creates no host CPU overhead for servicing timing events For more information refer to Reference 8 BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 3 Target Motor Theory 2 Target Motor Theory A brushless DC BLDC motor is a rotating electric machine where the stator is a classic three phase stator like that of an induction motor and the
7. encoder feedback and back EMF electromotive force signals for sensors control Input connections are made via connectors on the bottom side of the board and headers on theMPC5554DEMO board Output connections are made via 40 pin UNI 3 connector and expansion headers Power requirements are met by input connectors pecciah or aig Are Paginii v E a so s u gt 0 ae ts Le x sha encsne evpu_La Heapen c eyed se disgiaa m am Boe adon kos Kap oe x wee Cyaan Figure 14 Interface Board with UNI 3 For more information refer to Reference 5 BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 15 System Concept 3 3 4 Setting Overcurrent Level The over current fault signal is connected to the eMIOS output disable input pin eMIOS 10 that enables together with a proper eTPU configuration handling the fault by eTPU hardware This connection is part of the MPC5554 In order to enable handling the fault also by a software the fault signal available on eMIOS 10 pin generates interrupt request to the CPU in case of a fault The over current level is set by the trimmer R24 I_ SEN on the interface board with UNI 3 see Figure 15 Reference 5 describes what voltage must the trimmer define for the over current comparator Perform the following steps in order to set up the over current level properly without measuring the
8. moved OFF APP_STATE_STOP APP_STATE_DISABLE ON OFF switch moved OFF over current APP_STATE RUN fault interrupt Figure 19 Application State Diagram ON OFF switch moved ON APP_STATE_ENABLE The following paragraphs describe the processing in each of the application states 4 2 1 APP_STATE_INIT This state is passed through only It is entered either after a reset or after the APP STATE GLOBAL FAULT The following actions are performed in order to initialize re initialize the application e Callmy_system_etpu_init routine for eTPU module initialization e Get eTPU functions DATA RAM addresses for FreeMASTER e Get the addresses of channel configuration registers for FreeMASTER e Initialize the UART for FreeMASTER e Initialize FreeMASTER e Callmy_system_etpu_start routine for eTPU start At this point the CPU and the eTPU run in parallel BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 23 Software Design e Depending on the ON OFF switch position enter APP_ STATE STOP or APP STATE MOTOR FAULT 4 2 1 1 Initialization and Start of eTPU Module The eTPU module is initialized using the my_system_etpu_init function Later after initialization of all other peripherals the eTPU is started by my_system_etpu_start These functions use the general eTPU utilities and eTPU function API routines Both the my
9. real time control BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 2 Freescale Semiconductor PowerPC MPC5554 and eTPU Advantages and Features This 32 bit device is based on the PowerPC operating at a core frequency up to 132 MHz On chip modules include the following e High performance 32 bit PowerPC Book E compliant core e Memory management unit MMU with 24 entry fully associative translation look aside buffer TLB e 2MB of embedded Flash memory with error correction coding ECC e 64 KB on chip L2 static RAM with ECC e 32 KB of cache that can be configured as additional RAM e nexus IEEE ISTO 5001 class multicore debug capabilities e Two enhanced time processor units eTPUs e 64 channel enhanced direct memory access CDMA controller e Interrupt controller INTC capable of handling 286 satiable priority interrupt sources e Frequency modulated phase locked loop FMPLL to assist in electromagnetic interference EMI management e Enhanced queued analog to digital converter EQADC e Four deserial serial peripheral interface DSPI modules e Three controller area network FlexCAN modules e Two enhanced serial communication interface eSCI modules e Eighty eight channels of timed I O e Crossbar switch XBAR e Enhanced modular I O system eMIOS For more information refer to Reference 1 1 2 eTPU Module The eTPU is an intelligent semi autonomous co processor
10. sensing All the analog signals are adapted to be directly sampled by the A D converter This single board power stage contains an analog bridge gate driver integrated circuitry sensing and control circuitry power N MOSFET transistors DC bus brake chopper as well as various interface connectors for the supply and the motor lt i Q MOTOROLA Ja 0 g ma f tah pa AE TO 0 0 4 Ge S 24 04 2002 Figure 16 33395 Evaluation Motor Board For more information refer to Reference 4 3 3 6 BLDC Motor with Hall Sensors The enclosed motor is a low voltage Pittman BLDC motor N2311 The motor is capable of being controlled by Hall sensor techniques BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 17 Software Design The motor characteristics in Table 2 apply to operation at 25 C Table 2 Pittman BLDC Motor N2311 Motor Characteristics Characteristic Symbol Min Type Max Units Reference Winding Voltage Vi 9 6 V Speed V 12000 RPM Torque Constant Ki 0 007 Nm A Ki 1 082 _ oz in A Voltage Constant Ke 0 8 V KRPM Terminal Resistance Ri 0 13 0 18 W Winding Inductance L mH Continuous Current les 9 96 No Load Current V lps 1 20 Number of Poles Jm 8 E Temperature Rating 10 80 14 176 Figure 33 depicts the motor timing F
11. voltage 1 Connect all system parts according to Figure 11 2 Download and start the application 3 Turn ON OFF switch ON Using up and down buttons set the required speed to the maximum 4 Adjust the R24 trimmer You can find a level from which the red LED starts to light and the motor speed starts to be limited Set the trimmer level somewhat higher so that the motor can run at the maximum speed Turn the ON OFF switch OFF 6 Turn ON OFF switch ON Using up and down buttons set the required speed to the maximum 7 Ifthe application goes to the fault state during the acceleration adjust the R24 trimmer level somewhat higher so that the motor can get to the maximum speed Nn Figure 15 Overcurrent Level Trimmer on Interface Board with UNI 3 R24 3 3 5 33395 Evaluation Board The 33395 evaluation motor board is a 12 volt 8 amp power stage which is supplied with a 40 pin ribbon cable In combination with the MPC5554EVB and interface board with UNI 3 it provides an out of the box software development platform for small brushless DC motors The power stage enables BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 16 Freescale Semiconductor System Concept sensing a variety of feedback signals suitable for different motor control techniques It measures all the three phase currents reconstructs DC bus current from them DC bus voltage back EMF voltages with zero cross
12. 0 to 120 The commutation process is repeated per each 60 electrical degrees and is critical to maintain its angular time accuracy Any deviation causes torque ripples resulting in speed variation BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 6 Freescale Semiconductor Target Motor Theory VCC Phase A Phase C Phase B a VCC Actual flux vector Figure 6 Situation Right Before Commutation Counter clockwise Motion VCC J Phase A Phase C Phase B x VCC New flux vector Figure 7 Situation Right After Commutation 2 1 2 Speed Control Commutation ensures the proper rotor rotation of the BLDC motor while the motor speed only depends on the amplitude of the applied voltage The amplitude of the applied voltage is adjusted using the PWM technique The required speed is controlled by a speed controller which is implemented as a conventional proportional integral PI controller The difference between the actual and required speeds is input to the PI controller which then based on this difference controls the duty cycle of the PWM pulses which correspond to the voltage amplitude required to maintain the desired speed BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 7 System Concept Power Stage De re eA Pg a ay Piao tee tg eae Te RAR RL Pe gets Ee eo eee PE
13. CIE CDTRE ODIS API Clock Source intemat eTPU clock divided by 8 7 fie MHz 20 TCR2 Frequency eoo kHz T Angle Mode In Angle Mode a special hardware is enabled that works in combination with the TCRCLK signal TCR2 counter and microcode processing at Channel 0 to generate angle information on the TCR2 bus BLDC Motor with Hall Sensors Prescaler PNP oe Nig PGA Edit eTPU Function Digital filter is quaranteed to Detect pulses from width 750 ns Filter pulses up to width 500 ns C API to be used s_etpu_app_bldemhs 2_init 7 Channel Name Number PwM_master 7 PwM_phase _base_channel 8 PwM_phase _compl_channel 9 PwM_phaseB_base_channel 10 PwM_phaseB_compl_channel PwM_phaseC_base_channel FPwM_phaseC_compl_channel HD_phased 1 HD_phaseB nhacar Done BLDC Motor with Hall Sensors BLDC Motor with Hall Sensors BLDC Motor with Hall Sensors BLDC Motor with Hall Sensors BLDC Motor with Hall Sensors M Channel Input Digital Filter m TCRCLK Digil i 9 BLDC Motor with Hall Sensors Channel input signals are filtered by a digital filter TCRCLK s 10 BLDC Motor with Hall Sensors fx mpre vea nora Herta extemaly lt 41 BLDC Motor with Hall Sensors gota ier 12 BLDC Motor with Hall S w Digital filter sample rate TPUCLK 732 4 MHz ae otor with Fall Sensors Digital filter 13 BLDC Motor with Hall Se
14. CMHSLZx_PWM_PHASEC_BASE_CHANNEL APP_BLDCMHSLZx_HD_PHASEA APP_BLDCMHSLZx_HD_PHASEB APP_BLDCMHSLZx_HD_PHASEC uint8_t uint32_t int32_t int22 engine A Liat 4 4s ar 4t er engine A engine A engine Figure 20 eTPU Configuration Using the eTPU Graphical Configuration Tool 4 2 1 2 Initialization of FreeMASTER Communication Prior to the FreeMASTER initialization it is necessary to set pointers to the eTPU functions DATA RAM bases and configuration register bases Based on these pointers which are read by FreeMASTER during the initialization the locations of all eTPU function parameters and configuration registers are defined This is essential for correct Free MASTER operation BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 26 Freescale Semiconductor Software Design FreeMASTER consists of software running on a PC and on the microprocessor connected via an RS 232 serial port A small program resident in the microprocessor communicates with the FreeMASTER on the PC in order to return status information to the PC and processes control information from the PC The microprocessor part of the FreeMASTER is initialized by two functions iniFmasterUart and fmasterInit Both functions are included in fmaster c which automatically initializes the UART driver and installs all necessary services 4 2 1 3 Initialization of Necess
15. Controller Driven by eTPU on MPC5554 Rev 0 48 Freescale Semiconductor Table 5 References continued 13 Using the Analog Sensing for DC Motors ASDC eTPU Function AN2846 14 Using the DC Motor Control eTPU Function Set set3 AN2958 15 eTPU Graphical Configuration Tool http www freescale com search keyword ETPUGCT 16 DSP56F80x MC PWM Module in Motor Control Applications AN1927 References BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 49 THIS PAGE INTENTIONALLY LEFT BLANK BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 50 Freescale Semiconductor THIS PAGE INTENTIONALLY LEFT BLANK BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 51 How to Reach Us Home Page www freescale com E mail support freescale com USA Europe or Locations Not Listed Freescale Semiconductor Technical Information Center CH370 1300 N Alma School Road Chandler Arizona 85224 1 800 521 6274 or 1 480 768 2130 support freescale com Europe Middle East and Africa Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen Germany 44 1296 380 456 English 46 8 52200080 English 49 89 92103 559 Ge
16. FAULT MICROCODE GE FAULT ILLEGAL INSTR or FAULT MISC 4 2 Application State Diagram The application state diagram consists of seven states see Figure 19 After reset the application goes firstly to APP_STATE_ INIT Where the ON OFF switch is in the OFF position the APP_STATE STOP follows otherwise the APP_STATE MOTOR FAULT is entered and the ON OFF switch must be turned OFF to get from APP_ STATE MOTOR FAULT to APP_STATE_ STOP Then the cycle between APP STATE STOP APP STATE ENABLE APP STATE RUN and APP STATE DISABLE can be repeated depending on the ON OFF switch position APP_STATE ENABLE and APP STATE DISABLE states are introduced in order to ensure the safe transitions between the APP STATE STOP and APP_ STATE RUN states Where the over current fault interrupt is raised see BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 22 Freescale Semiconductor Software Design red line on Figure 19 the APP_ STATE MOTOR FAULT is entered This fault is cleared by moving the ON OFF switch to the OFF position and thus entering the APP_STATE STOP Where the eTPU global exception interrupt is raised see gray line on Figure 19 the APP_ STATE GLOBAL FAULT is entered The global fault is cleared by moving the ON OFF switch to the OFF position and thus entering the APP_STATE_INIT reset ON OFF switch moved OFF APP_STATE_INIT APP_STATE_ APP_STATE_ GENERAL_FAULT ON OFF switch MOTOR_FAULT
17. Freescale Semiconductor Application Note AN3007 Rev 0 08 2005 BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Covers MPC5554 and all ef PU equipped Devices by Milan Brejl amp Michal Princ amp Pavel Sustek System Application Engineers Roznov Czech System Center This application note describes the design of a 3 phase brushless DC BLDC motor drive based on Freescale s PowerPC MPC5554 microcontroller The application design takes advantage of the enhanced time processing unit eTPU module which is used as a motor control co processor The eTPU completely handles the motor control processing eliminating the microprocessor overhead for other duties BLDC motors are very popular in a wide array of applications Compared to a DC motor the BLDC motor uses an electric commutator replacing the mechanical commutator and making it more reliable than the DC motor In BLDC motors rotor magnets generate the rotor s magnetic flux allowing BLDC motors to achieve higher efficiency Therefore BLDC motors may be used in high end white goods refrigerators washing machines dishwashers etc high end pumps fans and other appliances that require high reliability and efficiency The concept of the application is to create a speed closed loop BLDC driver using a Hall position sensor It serves as an example of a BLDC motor control system design using a Freescale microprocessor with the e
18. I eliminates the need to initialize each eTPU function separately and to handle all eTPU function initialization settings and so ensures the correct cooperation of eTPU functions BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 19 Software Design Software Level Source Code Files Origin User Application the only code Run Time Run Time Initialization Methods written by Methods Methods my system_etpu_init the user a O my _system_etpu_start User eTPU z TE generated A i lt user app gt etpu gct c by eTPU Initialization es ed SERES ae Code l I AN2892 AoolicHi apes etpu_app lt app name gt c h AN2954 pplication p tH 57SW i AN2940 Ba etpu lt func gt c h A Ta AF _ Standard eTPU z z mies etpu util c h 7 Utilities pe 7 etpu_struct h Z Code Generated F l etpu lt func gt auto h by eTPU pu etpu_set3 h Compiler Ph et lt func gt c ks ay etpuc set3 c CPU Code Freescale supplied code eTPU Code Generated code ByteCraft supplied code Figure 17 eTPU Project Structure BLDC Motor w
19. P bee Ee Cd usar ks peer Gang ae 1 PWM Output Q Duty Cycle z SON Speed aes PWM Controller Generator i gt A Commutation Odesired Hall Sensors Figure 8 Speed Controller The speed controller calculates the PI algorithm given in the equation below u t KJ e s ih zf eod After transforming the equation into a discrete time domain using an integral approximation with the Backward Euler method we get the following equations for the numerical PI controller calculation u k up k u k up k K e k u k u k 1 K e k CT where e k Input error in step k w k Desired value in step k m k Measured value in step k u k Controller output in step k Up k Proportional output portion in step k uj k Integral output portion in step k uj k 1 Integral output portion in step k 1 T Integral time constant T Sampling time Ko Controller gain 3 System Concept 3 1 System Outline The system is designed to drive a 3 phase BLDC motor The application meets the following performance specifications e Voltage control of a BLDC motor using Hall sensors e Targeted at PowerPC MPC5554DEMO evaluation board MPC554DEMO interface board with UNI 3 33395 evaluation motor board and Pittman BLDC motor N2311 BLDC Motor with Speed Closed Loop and DC Bus Break Coniroller Driven by eTPU on MPC5554 Rev 0 8 Freescale Semiconductor System Concept Co
20. T ER Chi Freq 12 50kHz Low resolution 4 i I ARE E Geet tis age Md re a cata atte Geetha dee ee eaetn ace A dee i J a r a Soe iene Ge e a a a a a a a i I 4 broo a o 5 00 V asi pte a 5 sy 8 Mar 2005 m gt 47 0000ms 09 41 23 Figure 28 Oscilloscope Screen shot Showing Functionality of the Break Controller Tek PreVu M4 00ms A 0 00 100mY A 40 0ms 34 3ms Ch1 Freq 3 672kHz2 Low signal amplitude chil S00 ib S00 V SECTS A chi 7 2320 8 Mar 2005 m 2 78400ms 09 32 35 Figure 29 Oscilloscope Screen shot showing Functionality of the Break Controller in Detail Zoom of DC bus Break Control Signal For more details about the BC eTPU function refer to Reference 12 BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 38 Freescale Semiconductor Software Design 4 4 5 Analog Sensing for DC Motors ASDC The analog sensing for DC motors eTPU function ASDC is useful for preprocessing analog values that are measured by the AD converter and transferred to the eTPU data memory by DMA transfer The ASDC function is also useful for triggering the AD converter and synchronizing other eTPU functions All the above mentioned ASDC features are utilized in the application The ASDC is initialized to run in PWM synchronized mode e g the first ASDC edge is synchronized with the beginning of the PWM period Simultaneously the ASDC manages to synchron
21. TPU It also Freescale Semiconductor Inc 2005 All rights reserved k ANOaKRWNDY Table of Contents PowerPC MPC5554 and eTPU Advantages and FANN Siraan aS 2 Target Motor THEORY scere 4 System CONCE a r 8 Software Desig eisena eisian RAAS 18 Implementation Notes cccesceesererseeees 43 Microprocessor Usage cseceeseeeeeeeceees 47 Summary and Conclusions ccesseeeeees 48 FAB IG ME E Saroa e a mageuntartsd 48 4 freescale semiconductor PowerPC MPC5554 and eTPU Advantages and Features illustrates the usage of dedicated motor control eTPU functions that are included in the DC motor control eTPU function set This application note also includes basic motor theory system design concept hardware implementation and microprocessor and eTPU software design including the FreeMASTER visualization tool Figure 1 Using MPC5554DEMO 33395 Evaluation Motor Board and Pittman BLDC Motor 1 PowerPC MPC5554 and eTPU Advantages and Features 1 1 PowerPC MPC5554 Microcontroller The MPC5554 microcontroller is a family of next generation powertrain microcontrollers based on the PowerPC Book E architecture Featuring two 32 channels eTPU engines 32 Kbytes of cache 64 Kbytes of internal SRAM 2 Mbytes of internal Flash memory a 64 channel eDMA controller 3 FlexCAN modules 3 UARTs and four DSPI modules the MPC5554 family has been designed for applications that require complex
22. _system_etpu_init and my _system_etpu_start functions included in bldcmhs1l1_etpu_gct c file are generated by eTPU graphical configuration tool The eTPU graphical configuration tool can be downloaded from http www freescale com webapp sps site prod_summary jsp code eTPU For more information refer to Reference 15 The my_system_etpu_init function first configures the eTPU module and motor settings Some of these settings include the following e Channel filter mode three sample mode e Channel filter clock etpuclk div 32 The input signals from Hall sensors are filtered by channel filters The filter settings guarantee filtering all noise pulses up to a width of 500ns and pass pulses from a width of 750ns at 128 MHz system clock e TCRI1 source etpuclk div 2 e TCRI1 prescaler 1 The TCR1 internal eTPU clock is set to its maximum rate of 64 MHz at 128 MHz system clock corresponding to the 16ns resolution of generated PWM signals e TCR2 source etpuclk div 8 e TCR2 prescaler 20 The TCR2 internal eTPU clock is set to a rate of 800 kHz at 128 MHz system clock The TCR2 clock settings are optimized for motor speed calculation precision After configuring the module and engine settings the my_system_etpu_init function initializes the eTPU channels e Channel 1 Hall decoder HD phase A Channel 2 Hall decoder HD phase B Channel 3 Hall decoder HD phase C Channel 5 speed controller SC Channel 7 PWM ma
23. al damages Typical parameters that may be provided in Freescale Semiconductor data sheets and or specifications can and do vary in different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each customer application by customer s technical experts Freescale Semiconductor does not convey any license under its patent rights nor the rights of others Freescale Semiconductor products are not designed intended or authorized for use as components in systems intended for surgical implant into the body or other applications intended to support or sustain life or for any other application in which the failure of the Freescale Semiconductor product could create a situation where personal injury or death may occur Should Buyer purchase or use Freescale Semiconductor products for any such unintended or unauthorized application Buyer shall indemnify and hold Freescale Semiconductor and its officers employees subsidiaries affiliates and distributors harmless against all claims costs damages and expenses and reasonable attorney fees arising out of directly or indirectly any claim of personal injury or death associated with such unintended or unauthorized use even if such claim alleges that Freescale Semiconductor was negligent regarding the design or manufacture of the part e a oe 2 freescale semiconductor Freescale and the Freescale logo are tradem
24. arks of Freescale Semiconductor Inc All other product or service names are the property of their respective owners Freescale Semiconductor Inc 2004 All rights reserved AN3007 Rev 0 08 2005
25. ary Peripheral Modules Several peripheral modules needed for DC bus voltage measurement processing must be initialized e An internal analog to digital converter is used for sampling the DC bus voltage analog value Initialization of the AD converter module is done by the quick start configuration tool e Three DMA channels are used to periodically transfer data from ADC to the eTPU data memory Initialization of the DMA module is done by the quick start configuration tool For a detailed description of quick start configuration tool refer to Reference 3 For a detailed description of DC bus voltage measurement and data transfer processing see 4 4 5 4 2 2 APP_STATE_STOP In this state the PWM signals are disabled and the motor is off The motor shaft can be rotated by hand which enables the user to explore the functionality of the Hall decoder HD eTPU function to watch variables produced by the HD and to see Hall sensor signals in FreeMASTER When the ON OFF switch is turned on the application goes through APP_STATE_ ENABLE to APP STATE RUN 4 2 3 APP_STATE_ENABLE This state is passed through only The following actions are performed in order to switch the motor drive on e Reset the required speed e Enable the generation of PWM signals If the PWM phases were successfully enabled the eMIOS channel 10 is configured as input interrupt on falling edge and APP_STATE RUN is entered Where the PWM phases were not successfully ena
26. bldcmhs12_instance uint8_t configuration BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 29 Software Design int32_t fs_etpu_app_bldcmhs12_disable bldcemhs12_instance_t bldcmhs1l2_instance fs_etpu_app_bldcmhs12_set_speed_required bldcemhs12_instance_t bldcmhs12_instance int32_t speed_required_rpm Value return functions fs_etpu_app_bldcmhs12_get_data bldcemhs12_instance_t bldcmhs12_instance bldemhs12_data_t bldcmhs12_data 4 3 1 int32_t fs_etpu_app_bldcmhsl2_init This routine is used to initialize the eTPU channels for the BLDC motor with speed closed loop and DC bus break controller application This function has the following parameters bldcmhsl2_instance bldcmhsl2_instance_t This is a pointer to bldcmhs12_instance_t structure which is filled by s_etpu_app bldcmhs12_ init This structure must be declared in the user application Where there are more instances of the application running simultaneously there must be a separate bldcmhsl2_instance_t structure for each one PWM_ master_channel uint8_t This is the PWM master channel number 0 31 for ETPU_A and 64 95 for ETPU_B PWM_phaseA_channel uint8_t This is the PWM phase A channel number 0 31 for ETPU_A and 64 95 for ETPU_B In the case of complementary signal generation PWM_phases_type FS_ETPU_APP_ BLDCMHSL2_ COMPL PAIRS the comp
27. bled the application state does not change 4 2 4 APP_STATE_RUN In this state the PWM signals are enabled and the motor is on The required motor speed can be set using the up and down buttons on the interface or by using FreeMASTER The latest value is periodically written to the eTPU When the ON OFF switch is turned off the application goes through APP_STATE_ DISABLE to APP STATE STOP BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 27 Software Design 4 2 5 APP_STATE_DISABLE This state is passed through only The following actions are performed in order to switch the motor drive off e Reset the required speed e Disable the generation of PWM signals If PWM phases were successfully disabled APP_ STATE STOP is entered Where PWM phases were not successfully disabled the application state remains the same 4 2 6 APP_STATE_MOTOR_FAULT This state is entered after the over current fault interrupt service routine The application waits until the ON OFF switch is turned off This clears the fault and the application enters the APP_STATE_ STOP 4 2 7 APP_STATE_GLOBAL_FAULT This state is entered after the eTPU global exception interrupt service routine The application waits until the ON OFF switch is turned off This clears the fault and the application enters the APP_STATE_INIT 4 3 eTPU Application API The eTPU application API encapsulates seve
28. earlier for proper operation of a BLDC motor it is necessary to keep the angle between the stator and rotor flux as close to 90 as possible We get a total of six possible stator flux vectors with a six step control The stator flux vector must be changed at specific rotor positions which are usually sensed by the Hall sensors The Hall sensors generate three signals that also consist of six states Each of the Hall sensors states correspond to a certain stator flux vector All of the Hall sensors states with corresponding stator flux vectors are illustrated in Figure 5 ABC 01 0 _ Phase B Phase C ABC 100 ABC 001 ABC 101 ABC Hall Sensors Output Figure 5 Stator Flux Vectors at Six Step Control The next two figures depict the commutation process The actual rotor position in Figure 6 corresponds to the Hall sensors state ABC 110 see Figure 5 Phase A is connected to the positive DC bus voltage by the transistor Q1 phase C is connected to the ground by transistor Q6 and phase B is unpowered As soon as the rotor reaches a certain position see Figure 7 the Hall sensors state changes its value from ABC 110 to ABC 100 A new voltage pattern is selected and applied to the BLDC motor As shown below when using the six step control technique it is difficult to keep the angle between the rotor flux and the stator flux precisely at 90 in a six step control technique The actual angle varies from 6
29. equired speed ramp time in ms A step change of the required speed from 0 to speed_range rpm is slowed down by the ramp to take the defined time e BC_mode uint8_t This is the function mode This parameter should be assigned a value of FS ETPU_APP_ BLDCMHSL2_ BC MODE ON OFF or FS ETPU_APP BLDCMHSL2 BC MODE PWM e BC_polarity uint8_t This is the BC output polarity This parameter should be assigned a value of FS ETPU_APP_BLDCMHSL2 BC ON HIGH or FS_ETPU APP BLDCMHSL2 BC ON LOW BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 31 Software Design e BC_u_de_bus ON perc uint8 t This is the proportion between U_DC_BUS above which the BC output is ON and the nominal U DC _ BUS expressed in percentage usually about 130 e BC_u_de_bus OFF perc uint8_t This is the proportion between U_DC_BUS below which the BC output is OFF and the nominal U_DC_BUS expressed in percentage usually about 110 e ASDC_polarity uint8_t This is the polarity to assign to the ASDC function This parameter should be assigned a value of FS ETPU_APP_ BLDCMHSL2_ ASDC PULSE HIGH or FS_ETPU APP BLDCMHSL2 ASDC PULSE LOW e ASDC_measure_time_us uint24 t Time from the first triggering edge to the second edge at which the result queue is supposed to be ready in the DATA_RAM in us This value depends on the A D conversion time and DMA transfer time e ASDC_result_
30. er to check channel latencies using an oscilloscope and eliminates the necessity of theoretical WCL calculations As mentioned earlier some eTPU functions are not intended to process any input or output signals for driving the motor These functions turn the output pin high and low so that the high time identifies the period of time in which the function execution is active An oscilloscope can be used to determine how much the channel activity pulse varies in time which indicates the channel service latency range For example when the oscilloscope time base is synchronized with the PWM periods the behavior of a tested channel activity pulse can be described by one of the following cases e The pulse is asynchronous with the PWM periods This means that the tested channel activity is not synchronized with the PWM periods e The pulse is synchronous with the PWM periods and stable This means that the tested channel activity is synchronous with the PWM periods and is not delayed by any service latency e The pulse is synchronous with the PWM periods but its position varies in time This means that the tested channel activity is synchronous with the PWM periods and the service latency varies in this time range BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 40 Freescale Semiconductor Software Design aas OMS a cht so m 0 000005 PWM periods Figure 31 Oscil
31. ess spaces are 256 Kbytes and high address spaces are 1 5 Mbyte in size This gives a total memory space of 2Mbytes For more information refer to Reference 2 Table 1 lists all MPC5554DEMO jumper settings used in the application BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 12 Freescale Semiconductor System Concept Fi Pee rrereege Ad A tu OLL Figure 11 Connection of Application Parts Table 1 MPC5554DEMO Jumper Settings Jumper Setting CAN_SEL Setting CONFIG SWITCH Setting JP1 1 1 2 1 12 1 ON JP1 2 1 2 2 12 2 OFF JP2 1 23 3 12 3 ON JP3 1 2 4 12 4 OFF JP4 1 23 5 12 5 ON JP5 1 2 6 12 6 OFF VRH_EN 1 2 SRAM_SEL 1 23 VSTBY_SWITCH ON 3 3 2 Flashing the MPC5554DEMO The eSys Flasher utility can be used for programming code into the FLASH memory on the MPC5554DEMO Check for correct setting of switches and jumpers The flashing procedure is as follows 1 Run Metrowerks MPC55xx V1 5b2 and open the project Choose the Intflash target and compile the application A file simple_eflash elf S19 which will be loaded into FLASH memory is created in the project directory bin BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 13 System Concept 2 Run the eSysFlasher application In the Target Configuration window select the type of the BDM Communicati
32. igure 26 When the DC bus voltage is lower than u_dc_bus_OFF the control signal is turned off Between the u_dc_bus_ OFF and u_dc_bus_ON thresholds a PWM signal with a duty cycle linearly increasing from 0 to 100 is generated Above the u_dc_bus_ON threshold the control signal is turned on The functionality of the BC is shown in figures Figure 27 Figure 28 Figure 29 Signal 1 dark blue BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 36 Freescale Semiconductor Software Design line represents the DC bus voltage signal 2 light blue line reflects the DC bus break control signal generated by the BC a Duty_cycle 100 0 gt U_dc_bus_OFF U dc bus U_dc_bus_ ON Figure 26 PWM Mode of the Break Controller Function Tek PreVu gang lA 1 60 3 56V EERE AA E cen seven ee wane Guay OOE AREN ariel EE E ENEE oat A 70 4ms 19 0ms Chi Freq spl Rico ttl ead Scape dls cools p d H2 i No period found 2 00 V 40 0ms A Chl f 2 12 V 4 Mar 2005 m gt 47 0000ms 17 34 48 Figure 27 Oscilloscope Screen shot Showing DC bus Voltage Course when a Motor Reaches to Generating Mode Without Action of Break Controller BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 37 Software Design Tek cstan Y EE EN AA a gt ab asi ou oo lt lt EEE TEY E AN
33. ior using scopes FreeMASTER software was designed to provide an application debugging diagnostic and demonstration tool for the development of algorithms and applications It runs on a PC connected to the MPC5554DEMO via an RS232 serial cable A small program resident in the microprocessor communicates with the FreeMASTER software to return status information to the PC and process control information from the PC FreeMASTER software executing on a PC uses part of Microsoft Internet Explorer as the user interface Note that FreeMASTER version 1 2 31 1 or higher is required The FreeMASTER application can be downloaded from http www freescale com For more information about FreeMASTER refer to Reference 7 3 3 Hardware Implementation and Application Setup As previously stated the application runs on the MPC5554 family of PowerPC microprocessors using the following e MPCS5554DEMO e Interface board with UNI 3 e 33395 evaluation motor board e Pittman N2311 3 phase BLDC motor e Power supply 12V DC minimum 2 7 Amps Figure 11 shows the connection of these parts All system parts are supplied by Freescale and documented according to references 3 3 1 PowerPC MPC5554 Evaluation Board MPC5554DEMO This board is not intended to be a full evaluation board for the MPC5554 but shows a minimal system for learning about the new MPC5500 family of product The FLASH memory placed on the MPC5554 has three address spaces Low and mid addr
34. ith Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 20 Freescale Semiconductor Software Design 4 1 CPU Software Flowchart Timer 3 Interrupt Read ON OFF switch status Handle application state machine Initialize interrupts and pins Service Up Down buttons and Status LED Read application data structure Re initialize all DMA BCRx registers FreeMaster Timer Interrupt Fault Interrupt FreeMaster Dispatcher Handle overcurrent fault eTPU Channel Interrupt eTPU Global Exception Interrupt FreeMaster Recorder Handle eTPU global exception Figure 18 CPU Software Flowchart After reset the CPU software initializes interrupts and pins The following CPU processing is incorporated in two periodic timer interrupts one periodical eTPU channel interrupt and two fault interrupts 4 1 1 Timer Interrupt Service Routine The timer interrupt is handled by the timer_isr function The following actions are performed periodically in timer_isr e Read the ON OFF switch status e Handle the application state machine The application state diagram is described in detail below e Service the up and down buttons and the status LED by the ApplicationButtonsAndStatusLed function e Read the data structure through the eTPU application API routine fs _ etpu app bldcmhsll1_ get data see 4 3 4 1 2 FreeMASTER Interrupt Service Routine The FreeMASTER interrupt service routine is ca
35. ize the BC function by generating the link to the BC channel every 16th ASDC period The ASDC function preprocesses the DC bus voltage analog value and passes the adjusted value as an input to the BC function Processing of the DC bus voltage analog value includes bit shifting and filtering ADC result queue DMA Al B lt anster AD converter bit shift bit shift offset offset filter filter sign sign Switch switch ASDC CI C Pre processed analog values ADC trigger ADC trigger Li J Bb __ l link to outer link to inner link to inner loop controller loop controller loop controller Figure 30 Functionality of ASDC In order to ensure periodic sampling of the DC bus voltage and the quick transfer of the measured data from the AD converter to the ETPU DATA RAM several peripheral modules are used e An internal analog to digital converter is used for sampling of the DC bus voltage analog value e 3 direct memory access DMA channels are used as follows DMA channel 0 is used for the transfer of the configuration word 0x80000000 from the eqadcCQueue0 to the CFPR CFIFO push register of the eQADCmodule This operation triggers the eQADC converter sampling The DMA channel 0 transfer is initiated by a DMA request generated by DMAchannel 30 DMA channel 1 is used for the transfer of the result from the RFPR result FIFO
36. k Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 9 errr System Concept ON OFF gt Application uP t State Machine PWM ___ 3 Phase o Power Stage DOWN L Signals O gt E gt FreeMaster Remote Control Hall Sensor Signals Fault LED Hardware 9 12V DC Status LED Fault Signal DC bus break control Figure 9 System Concept The system processing is distributed between the CPU and the eTPU which both run in parallel The CPU performs the following tasks Periodically scans the user interface ON OFF switch up and down buttons FreeMASTER Based on the user input it handles the application state machine and calculates the required speeds which is passed to the eTPU Periodically reads application data from eTPU DATA RAM in order to monitor application variables In the event of an overcurrent fault the PWM outputs are immediately temporarily disabled by the eTPU hardware Then after an interrupt latency the CPU disables the PWM outputs permanently and displays the fault state The eTPU performs the following tasks Six eTPU channels PWMC are used to generate PWM output signals Three eTPU channels HD are used to process Hall sensor signals On each incoming edge a revolution period is calculated and the PWM output signals are commuted One eTPU channel BC is used for controlling the DC bus break
37. lementary channel is one channel higher PWM_ phaseB_channel uint8_t This is the PWM phase B channel number 0 31 for ETPU_A and 64 95 for ETPU_B In the case of complementary signal generation PWM _phases_type FS_ETPU_APP_ BLDCMHSL2_ COMPL PAIRS the complementary channel is one channel higher PWM_phaseC_channel uint8_t This is the PWM phase C channel number 0 31 for ETPU_A and 64 95 for ETPU_B In the case of complementary signal generation PWM_phases_type FS_ETPU_APP_ BLDCMHSL2_ COMPL PAIRS the complementary channel is one channel higher HD_phaseA_channel uint8_t This is the Hall decoder phase A channel number 0 31 for ETPU_A and 64 95 for ETPU_B HD_phaseB_channel uint8_t This is the Hall decoder phase B channel number 0 31 for ETPU_A and 64 95 for ETPU_B HD_phaseC_channel uint8_t This is the Hall decoder phase C channel number 0 31 for ETPU_A and 64 95 for ETPU_B SC_channel uint8_t This is the speed controller channel number 0 31 for ETPU_A and 64 95 for ETPU_B BLDC Motor with Speed Closed Loop and DC Bus Break Coniroller Driven by eTPU on MPC5554 Rev 0 30 Freescale Semiconductor Software Design e BC_ channel uint8_t This is the break controller channel number 0 31 for ETPU_A and 64 95 for ETPU_B e ASDC _channel uint8_t This is the analog sensing for DC motors ASDC channel number 0 31 for ETPU_A and 64 95 for ETPU_B e PWM_phases_type uint8_t This pa
38. lled fmasterDispatcher This function is implemented in fmaster c BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 21 Software Design 4 1 3 eTPU Channel Interrupt Service Routine This interrupt which is raised every PWM period by the PWMMDC eTPU function running on eTPU channel 7 is handled by the etpu_ch7_isr function This function calls fmasterRecorder implemented in fmaster c enabling the configuration of application variable time courses with a PWM period time resolution 4 1 4 Fault Interrupt Service Routine The over current fault interrupt which is raised by eMIOS input function running on eMIOS channel 10 is handled by the emios_isr function The following actions are performed in order to switch the motor off e Reset the required speed e Disable the generation of PWM signals e Switch the fault LED on e Enter APP_STATE MOTOR FAULT e Set FAULT _OVERCURRENT 4 1 5 eTPU Global Exception Interrupt Service Routine The global exception interrupt is handled by the etpu_globalexception_isr function Assertion of the following can cause this interrupt assertion e Microcode global exception e Illegal instruction flag e SCM MISC flag The following actions are performed in order to switch the motor off e Reset the required speed e Disable the generation of PWM signals e Enter APP STATE GLOBAL FAULT e Based on the eTPU global exception source set
39. loscope Screen shot and Explanation of eTPU Timing Figure 31 explains the application eTPU timing The oscilloscope screen shot depicts a typical situation described below A live view on the oscilloscope screen enables the user to see the variation of SC and PWMMDC activity pulses which determines the channel service latency ranges In Figure 31 signals 3 pink and 4 green are PWM signals of one phase It is a complementary pair of center aligned PWM signals The base channel 3 is of active high polarity while the complementary channel 4 is active low The PWM phase commutation is recognizable on the screen The PWM period is 50us which corresponds to a PWM frequency of 20 kHz Signal blue is generated by the speed controller SC eTPU function Its pulses determine the activity of the SC The pulse width determines the time necessary to calculate the motor speed from a revolution period measured by the Hall decoder HD calculate the required speed ramp and apply the PI controller algorithm This output is the new value of applied motor voltage This calculation is performed periodically at a 10 kHz rate which is every second PWM period Signal 2 cyan is generated by the PWM master for DC motors PWMMDC eTPU function Its pulses determine the activity of the PWMMDC Immediately after each SC pulse a very narrow PWMMDC pulse occurs These pulses determine the service time of an SC request to update the new value of applied motor
40. ls commutation on Hall signal transitions and to stop the speed controller This function has the following parameter BLDC Motor with Speed Closed Loop and DC Bus Break Coniroller Driven by eTPU on MPC5554 Rev 0 32 Freescale Semiconductor Software Design e bldemhsl2_instance bldemhsl2_instance_t This is a pointer to bldcmhsl2_instance_t structure which is filled by fs _etpu_app_bldcmhs12_ init 4 3 4 fs_etpu_app_bldcmhsl2_set_speed_required This routine is used to set the required motor speed This function has the following parameters e bldcemhsl2_instance bldecmhsl2_instance_t This is a pointer to bldecmhs 2_instance_t structure which is filled by fs_etpu_app_bldcmhs12_ init e speed_required_rpm int32_t This is the required motor speed in rpm 4 3 5 fs_etpu_app_bldcmhsl2_get_data This routine is used to get the application state data This function has the following parameters e bldcemhsl2_instance bldcmhsl2_instance_t This is a pointer to bldecmhs12_instance_t structure which is filled by fs _etpu_app_bldcmhs12_ init e bldemhsl2_data bldcmhsl2_data_t This is a pointer to bldcmhsl2_data_t structure of application state data which is updated 4 4 eTPU Block Diagram The eTPU functions used to drive the BLDC motor with speed closed loop and DC bus break controller are located in the motor control set of eTPU functions set3 DC motors The eTPU functions within the se
41. neral PID controller algorithm The controller calculates its output based on two inputs a measured value and a required value The measured value the actual motor speed is calculated based on inputs provided by the HD function The required BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 35 Software Design value is an output of the speed ramp whose input is a SC function parameter and can be provided by the CPU or another eTPU function In the motor control eTPU function set this function mostly provides the speed outer loop omega_actual applied_voltage a PI controller requested_value time Figure 24 Functionality of SC revolution_period sector_period scaling factor period omega_desired For more details about the SC eTPU function refer to Reference 10 4 4 4 Break Controller BC The purpose of the break controller BC eTPU function is to eliminate DC bus overvoltage when a motor is driven in the generating mode The BC function generates the DC bus break control signal see Figure 25 based on the actual DC bus voltage AC DC H BRIDGE DC bus DC bus break control signal Figure 25 Functionality of BC The described application uses the PWM mode of the BC function In this mode the BC function switches softly using a PWM signal The u_dc_bus ON and u_dc_bus_ OFF thresholds define a ramp see F
42. nominal DC bus voltage ASDC function triggers A D converter on high low edge DC bus voltage measurement time including A D conversion time and DMA transfer time is llus p_ASDC result_queue pointer contains the address of the measured sample of DC bus voltage Measured sample of DC bus voltage is shifted left by 8 bits DC bus voltage sample offset within ASDC_result_queue is 0 ASDC EWMaA filter time constant is 450 us The my_system_etpu_start function first applies the settings for the channel interrupt enable and channel output disable options then enables the eTPU timers thus starting the eTPU BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 25 Software Design eTPU Graphical ConfigurationTool bldcmhsi2_etpu_gect c File Edit View eTPU Help O ai Processor Function Set Engine A Engine A Channels Engine B Engine B Channel Unchatien Blac J Engine Disabled low power mode clocks stopped 4 eTPU Graphical ConfigurationTool bldcmhsi2_etpu_gct c E Holki File Edit View eTPU Help m TCR1 Clock Ds H amp wee Clock Source intemal eTPU clock divided by 2 z Jes MHz Processor Function Set Engine A Engine A Channels Verbatim Block less aM TORI Frequency 64 MHz Add Application _AddFunction Edt Remove TCR2 Clock Ch Function Name Channel Name Prio
43. ns added to the BLDCMHSL2 application API The routines can be found in the BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 28 Freescale Semiconductor Software Design etpu_app_bldcmhs12 c h files All BLDCMHSL2 application API routines will be described in order and are listed below Initialization function int32_t fs_etpu_app_bldcmhs12_init bldcmhs12_instance_t bldcmhs1l2_instance uint8_t PWM_master_channel uint8_t PWM_phaseA_channel uint8_t PWM_phaseB_channel uint8_t PWM_phaseC_channel uint8_t HD_phaseA_channel uint8_t HD_phaseB_channel uint8_t HD_phaseC_channel uint8_t SC_channel uint8_t BC_channel uint8_t ASDC_channel uint8_t PWM_phases_type uint32_t PWM_freq_hz uint32_t PWM_dead_time_ns int32_t speed_range_rpm int32_t speed_min_rpm int32_t dc_bus_voltage_mv uint8_t pole_pairs uints_t period_measured uint32_t SC_freq_hz int32_t SC_P_gain int32_t SC_I_gain uint32_t SC_ramp_time_ms uint8_t BC_mode uint8_t BC_polarity uint8_t BC_u_dc_bus_ON_perc uint8_t BC_u_dc_bus_OFF_perc uint8_t ASDC_polarity uint24_t AS uint32_t AS uint8_t AS uint32_t AS Change operation functions DC_measure_time_us DC_result_queue uint8_t ASDC_bit_shift DC_queue_offset DC_filter_time_constant_us int32_t fs_etpu_app_bldcmhs12_enable bldemhs12_instance_t
44. nsors Digital filter mode Three Sample Mode x G TPI 14 RI DF Motor with Hall Sensnre HD_phase HD_phaseB HD_phaseC sc PWM_master PWM_phaseA_base_channel P WM_phaseA_compl_channel P WM_phaseB_base_channel P WM_phaseB_compl_channel PwM_phaseC_base_channel PWM_phaseC_compl_channel ASD eTPU Function Jetoc Motor with Hall Sensors Speed Closed Loop and DC E z Channels PwM_phases_type FS_ETPU_APP_BL Parameter Values Parameter Name D Parameter Description This is the number of motor pole pairs f bus_voltage_myv 3000 High High Low Middle Middle Middle Middle Middle Middle Middle Middle cen The eTPU function provides one or more C language API calls which define how many channels and what parameters are used by the eTPU function IV Show parameter tips n fo fom fm fon fo fon Aco fn fo 07079 0 O oi Crt c ves Oft v Yes off v Yes Off Off Off Off Low Low Low Low Low Low ni lt gm00 0000000000 REEERE uint32_t uint32_t int32_t int32_t int32_t 4 pole_pairs period_measured SC_freq_hz SC_P_gain asin 10000 0x004000 nnnm bldc_instance revolution period BLDC Motor with Hall Sensors Speed Closed Loc bldemhsl2_instance bldc_ APP_BLDCMHSLZx_PWM_MASTER APP_BLDCMHSLZx_PWM_PHASEA_BASE_CHANNEL APP_BLDCMHSLZx_PWM_PHASEB_BASE_ CHANNEL APP_BLD
45. ntrol technique incorporates Voltage BLDC motor control with speed closed loop Both directions of rotation 4 quadrant operation Start from any motor position without rotor alignment Minimum speed of 300 RPM Maximum speed of 10000 RPM limited by power supply Manual interface start stop switch up down push button control LED indication FreeMASTER control interface speed set up speed loop close open choice FreeMASTER monitor FreeMASTER graphical control page required speed actual motor speed start stop status fault status FreeMASTER speed control scope observes required ramp and actual speeds applied voltage Detail description of all eTPU functions used in the application monitoring of channel registers and all function parameters in real time DC bus over current fault protection 3 2 Application Description A standard system concept is chosen for the motor control function see Figure 9 The system incorporates the following hardware Evaluation board MPC5554DEMO Interface board with UNI 3 33395 evaluation motor board Pittman BLDC motor N2311 with Hall sensors Power supply 12V DC 2 7 Amps The eTPU module runs the main control algorithm The 3 phase PWM output signals for a 3 phase inverter are generated according to feedback signals from Hall sensors and the input variable values provided by the microprocessor CPU BLDC Motor with Speed Closed Loop and DC Bus Brea
46. od When the break controller channel receives the link the updated value of DC bus voltage is compared with the defined over voltage thresholds and according to this comparison it generates the PWM based break control signal signal 1 blue in Figure 32 The period of this signal is 200us which corresponds to the frequency of 5 kHz 5 Implementation Notes 5 1 Scaling of Quantities The BLDC motor control algorithm running on eTPU uses a 24 bit fractional representation for all real quantities except time The 24 bit signed fractional format is represented using 1 23 format 1 sign bit 23 fractional bits The most negative number that can be represented is 1 0 whose internal representation is 0x800000 The most positive number is Ox7FFFFF or 1 0 ga The following equation shows the relationship between real and fractional representations Real Value Fractional Value RT Ouatity Range ractional Value Real Quatity Range where Fractional value is a fractional representation of the real value fract24 Real value is the real value of the quantity V A RPM etc Real quantity range is the maximal range of the quantity defined in the application V RPM etc 5 1 1 Pl Controller Parameters The PI controller parameters are set in a 32 bit extended fractional format 9 23 This format enables the user to set values in the range of 256 0 to 256 0 2 Internally the parameter value is transformed into one of two 24 bit fo
47. on as P amp E Wiggler Click OK to close the window 3 Go to the Program section by clicking the Program Flash button see Figure 12 Select the Binary Image set Address as 0x0 and check the Verify after program option see Figure 13 Press the Program and select intflash bin file Finally press Open button at the bottom of the window to start loading the code into the FLASH memory ess Flasher e MCU MPC5554 Program Flash Fill Part ID Ox0800001D Verify Flash Erase Flash Upload Flash Memory Window Reset CPU jE E Te Clear Screen Save Screen ff Version 1 0 Figure 12 eSysFlasher Target Configuration Window 4 Ifthe code has been programmed correctly remove the BDM interface and push the RESET button on the MPC5554Demo The application should now run from the FLASH The eSYS Flasher application can be downloaded from http www freescale com BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 14 Freescale Semiconductor System Concept Program S File Type S record Address ox 0 IV Verify after program Close Figure 13 eSys Flasher Program Window 3 3 3 Interface Board with UNI 3 This board enables to connect the power stage with a motor to the MPC5554DEMO board and can be used by software and hardware developers to test programs and tools It supports algorithms that use Hall sensors LEM sensors
48. on state ON ACTIVE HIGH ON ACTIVE LOW OFF LOW OFF HIGH BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 44 Freescale Semiconductor Implementation Notes e New complementary channel commutation state ON_ACTIVE_ HIGH ON ACTIVE LOW OFF LOW OFF _ HIGH e New phase options DUTY POS DUTY NEG For a full description of all commutation command options refer to Reference 14 Figure 33 depicts the Pittman BLDC motor N2311 motor timing diagram The following example describes how to define several of the commutation commands based on this timing diagram A Hall signal phase A low high transition comes at 300 electrical degrees blue dotted line The PWM phase B is turned off with the pin in low state and phase A on with active high polarity on the base channel and active low polarity on the complementary channel on this transition Furthermore the PWM phase B option is set to not change the calculated duty cycle value and the phase A option is set to negate the signed duty cycle value which generates a negative voltage On phase A this applies immediately while on phase B this will apply 60 degrees later when the phase is commuted on again So the commutation commands associated with the phase A low high transition in an incremental motor direction are defined using predefined macros as follows phaseA_commut_cmds lh_i_0O PWM_pha
49. or more motor specifications refer to Reference 6 3 3 7 Power Supply The power supply 12V 2 7A is also used to power the 3 phase micro power stage The application is scaled for this 12V power supply 4 Software Design This section describes the software design of the BLDC motor drive application The system processing is distributed between the CPU and the eTPU which run in parallel The CPU and eTPU tasks are described in terms of the following e CPU Software flowchart Application state diagram eTPU application API e eTPU eTPU block diagram eTPU timing BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 18 Freescale Semiconductor Software Design The CPU software uses several ready to use Freescale software drivers The communication between the microprocessor and the FreeMASTER on a PC is handled by software included in fmaster c h files The eTPU module uses the general eTPU utilities eTPU function interface routines eTPU function API and eTPU application interface routines eTPU application API The general utilities included in the etpu_util c h files are used for initialization of global eTPU module and engine settings The eTPU function API routines are used for initialization of the eTPU channels and interfacing each eTPU function during run time An eTPU application API encapsulates several eTPU function APIs The use of an eTPU application AP
50. pop register to the eTPU memory where points p ASDC _result_queue pointer The DMA channel 30 transfer is initiated by a DMA request generated by QADC module after the conversion is finished BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 39 Software Design DMA channel 30 is used for the transfer of the configuration word 0x0410 to the CFCR command FIFO control register This set the start bit and the QADC single scan mode The DMA channel 30 transfer is initiated by a DMA request generated by eTPU_A channel 14 When the transfer is complete the link to DMA channel 0 is made All setting is made using the quick start configuration tool refer to Reference 3 4 5 eTPU Timing eTPU processing is event driven Once an event service begins its execution cannot be interrupted by another event service The other event services have to wait which causes a service request latency The maximum service request latency or worst case latency WCL differs for each eTPU channel The WCL is affected by the channel priority and activity on other channels The WCL of each channel must be kept below a required limit For example the WCL of the PWMC channels must be lower than the PWM period A theoretical calculation of WCLs for a given eTPU configuration is not a trivial task The motor control eTPU functions introduce a debugging feature that enables the us
51. queue uint32_t Pointer to the result queue Result queue is an array of 16 bit words that contains the measured values e ASDC_bit_shift uint8_t This parameter defines how to align data from the result queue into fract24 or int24 This parameter should be assigned a values of FS ETPU_APP BLDCMHSL2 ASDC SHIFT LEFT BY 8 FS ETPU_APP BLDCMHSL2 ASDC SHIFT LEFT BY 10 FS ETPU_APP BLDCMHSL2 ASDC SHIFT LEFT BY 12 or FS ETPU_APP BLDCMHSL2 ASDC SHIFT LEFT BY 16 e ASDC_queue_ offset uint8_t Position of the U DC BUS sample in the result queue Offset is defined in bytes e ASDC _filter_time_constant_us uint32_t This the time constant of the filter which applies when processing the U_DC_BUS samples in us 4 3 2 int32_tfs_etpu_app_bldcmhsl2_enable This routine is used to enable the generation of PWM signals commutations on Hall signal transitions and to start the speed controller This function has the following parameters e bldemhsl2_instance bldemhsl2_instance_t This is a pointer to bldcmhsl2_instance_t structure which is filled by s_ etpu_app bldcmhs1l2_ init e configuration uint8_t This is the required configuration of the SC This parameter should be assigned a value of FS_ETPU APP BLDCMHSL2 SPEED LOOP OPENED or FS_ETPU APP BLDCMHSL2 SPEED LOOP CLOSED 4 3 3 int32_t fs_etpu_app_bldcmhsl2_disable bldcmhsl2_instance_t bldcmhsl2_instance This routine is used to disable the generation of PWM signa
52. ral eTPU function APIs The eTPU application API includes CPU methods which enable initialization control and monitoring of an eTPU application The use of eTPU application API functions eliminates the need to initialize and set each eTPU function separately ensuring correct cooperation of the eTPU functions The eTPU application API is device independent and handles only the eTPU tasks In order to shorten the eTPU application names abbreviated application names are introduced The abbreviations include the following e Motor type DCM DC motor BLDCM brushless DC motor PMSM permanent magnet synchronous motor ACIM AC induction motor SRM switched reluctance motor SM stepper motor e Sensor type H Hall sensors E shaft encoder R resolver S sincos X sensorless e Control type OL open loop PL position loop SL speed loop CL current loop SVC speed vector control TVC torque vector control Based on these definitions the BLDCMHSL2 is an abbreviation for BLDC motor with Hall Sensors and speed closed loop eTPU motor control application As there are several BLDC motor applications with Hall sensors and speed closed loop the number 2 denotes the second such application in order This second application moreover demonstrates the break controller eTPU function usage for DC bus over voltage protection The BLDCMHSL2 eTPU application API is described in the following paragraphs There are 5 basic functio
53. rame The SC activity precedes the PWMMDC activity so that the worst case SC latency does not affect the PWMMDC latency Tek Prevu T xO rN Chi F Eoo 7 Chil 10 0 V Ch3 10 0 V chal 10 9 PWM periods ae 64 0000us Figure 32 Oscilloscope Screen shot and Explanation of ASDC and BC Timing BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 42 Freescale Semiconductor Implementation Notes Figure 32 explains the timing of ASDC and BC eTPU functions Signals 3 pink and 4 green are PWM signals of one phase as in Figure 31 Signal 2 cyan is generated by the ASDC eTPU function The ASDC function triggers the AD converter by generating a DMA request on a high low edge active low polarity of ASDC and simultaneously sending the link to the BC channel every 16th ASDC period see Figure 32 The position of the ASDC first edge is synchronized with the beginning of the PWM period The time between the PWM period beginning and the ASDC first edge equals to one quarter of the PWM period The ASDC pulse width determines the time necessary to sample the DC bus voltage and to transfer this sampled value to the eTPU data memory ASDC starts measured sample preprocessing at the time of the second edge when a sample is supposed to be ready in the eTPU data memory The break controller eTPU function responds to the link generated by the ASDC function every 16th ASDC peri
54. rameter determines the type of all PWM phases This parameter should be assigned a value of FS_ETPU APP BLDCMHSL2_ SINGLE CHANNELS or FS_ETPU APP BLDCMHSL2 COMPL PAIRS e PWM_freq_hz uint32_t This is the PWM frequency in Hz e PWM_dead_time_ns uint32_t This is the PWM dead time in ns e speed_range rpm int32_t This is the maximum motor speed in rpm e speed_min_rpm int32_t This is the minimum measurable motor speed in rpm e dc_bus_ voltage mv int32_t This is the DC bus voltage in mV e pole _ pairs uint8 t This is the number of motor pole pairs e period_measured uint8 t This option defines the type of period measurement for speed calculation This parameter should be assigned a value of FS_ETPU APP BLDCMHSL2 REV PERIOD or FS_ETPU APP BLDCMHSL2 SECTOR PERIOD e SC_freq_hz uint32_t This is the speed controller update frequency in Hz The assigned value must be equal to the PWM_freq_hz divided by 1 2 3 4 5 e SC_P gain fract24 t This is the speed controller P gain in 24 bit signed fractional format 9 15 0x008000 corresponds to 1 0 0x000001 corresponds to 0 0000305 30 5 10 0x7FFFFF corresponds to 255 9999695 e SC_I gain fract24 t This is the speed controller I gain in 24 bit signed fractional format 9 15 0x008000 corresponds to 1 0 0x000001 corresponds to 0 0000305 30 5 10 0x7FFFFF corresponds to 255 9999695 e SC_ramp_time_ms uint32_t This parameter defines the r
55. rman 33 1 69 35 48 48 French support freescale com Japan Freescale Semiconductor Japan Ltd Headquarters ARCO Tower 15F 1 8 1 Shimo Meguro Meguro ku Tokyo 153 0064 Japan 0120 191014 or 81 3 5437 9125 support japan freescale com Asia Pacific Freescale Semiconductor Hong Kong Ltd Technical Information Center 2 Dai King Street Tai Po Industrial Estate Tai Po N T Hong Kong 800 2666 8080 support asia freescale com For Literature Requests Only Freescale Semiconductor Literature Distribution Center P O Box 5405 Denver Colorado 80217 1 800 441 2447 or 303 675 2140 Fax 303 675 2150 LDCForFreescaleSemiconductor hibbertgroup com Information in this document is provided solely to enable system and software implementers to use Freescale Semiconductor products There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document Freescale Semiconductor reserves the right to make changes without further notice to any products herein Freescale Semiconductor makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does Freescale Semiconductor assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability including without limitation consequential or incident
56. rmats either 9 15 or 1 23 based on the value 5 2 Speed Calculation The speed controller SC eTPU function calculates the angular motor speed using a revolution period measured by the Hall decoder HD eTPU function Optionally the speed controller can use the sector period instead of the revolution period The sector period is the time between two consecutive Hall signal BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 43 Implementation Notes transitions A sum of six sector periods equals one revolution period At a constant speed each of the six sector periods may have a slightly different value caused by an angular error in the Hall sensor positions This error affects the PI controller behavior in a negative way The revolution period is not affected by this error because the period is measured from a particular Hall signal transition to the same transition one revolution later The revolution period is updated on each transition six times per period The revolution period measured by the HD is the period of one electrical revolution The electrical revolution is related to the mechanical revolution via the number of motor pole pairs The Pittman BLDC motor N2311 is a 4 pole pair motor Hence the mechanical revolution period is a period of four electrical revolutions The speed controller calculates the angular motor speed using the following equation
57. rotor has surface mounted permanent magnets see Figure 2 Stator Stator winding in slots Shaft Rotor Air gap Permanent magnets Figure 2 BLDC Motor Cross Section In this respect the BLDC motor is equivalent to a reversed DC commutator motor in which the magnet rotates while the conductors remain stationary In the DC commutator motor the current polarity is altered by the commutator and brushes Unlike the brushless DC motor the polarity reversal is performed by power transistors switching in synchronization with the rotor position Therefore BLDC motors often incorporate either internal or external position sensors to sense the actual rotor position or the position can be detected without sensors 2 1 Digital Control of a BLDC Motor The BLDC motor is driven by rectangular voltage strokes coupled with the given rotor position see Figure 3 The generated stator flux interacts with the rotor flux which is generated by a rotor magnet and defines the torque and thus the speed of the motor The voltage strokes must be properly applied to two phases of the three phase winding system so that the angle between the stator flux and the rotor flux is kept as close to 90 as possible to get the maximum generated torque Therefore the motor requires electronic control for proper operation BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 4 Freescale Semiconductor Target Mo
58. s The PWMMDC function controls three PWMC functions three PWM phases and does not generate any drive signal The PWMMDC can be executed even on an eTPU channel not connected to an output pin channels 16 to 32 new input values new input values period update dat update dat date applied_voltage p no update p no update up rps polarity active high OR active low center aligned OR edge aligned single channel OR complementary pair ee ee ee ee S P OU U L CUCL OLS PWMC variable PWM periods LI LI LI H L a E E SO T ey E S G Figure 22 Functionality of PWMMDC PWMC PWMC For more details about the PWMMDC PWMF and PWMC eTPU functions refer to Reference 11 4 4 2 Hall Decoder HD The Hall decoder eTPU function is intended to process signals generated by Hall sensors in motion control systems The HD function uses three adjacent eTPU channels configured as inputs The HD function calculates the following parameters for the CPU BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 34 Freescale Semiconductor Software Design Sector Determines the position of the motion system in one of the sectors Direction Determines the direction of the motion system A direction value 0 means a positive incremental direction other values mean a negative decremental direction Revolution counter Determines the number of motion
59. seB_channel EFS_ETPU_PWMMDC_OFF_LOW lt lt 8 ES_ETPU_PWMMDC_OFF_LOW lt lt 16 ES_ETPU_PWMMDC_DUTY_POS lt lt 24 phaseA_commut_cmds lh_i_l PWM_phaseA_channelt EFS_ETPU_PWMMDC_ON_ACTIVE_HIGH lt lt 8 ES_ETPU_PWMMDC_ON_ACTIVE_LOW lt lt 16 FS_ETPU_PWMMDC_DUTY_NEG lt lt 24 BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 45 Implementation Notes 0 60 120 180 240 300 360 Hall signal Phase A Hall signal Phase B Hall signal Phase C voltage Phase A voltage Phase B voltage N Phase C Figure 33 Pittman BLDC Motor N2311 Timing Diagram For decremental direction read the motor timing diagram from right to left The Hall signal phase A low high transition comes at 120 electrical degrees red dotted line The PWM phase A is turned off and phase B on during this transition The PWM phase A option is set to negate the duty cycle in order to generate negative phase voltage and the phase B option not to negate in order to generate positive voltage So the commutation commands associated with the phase A low high transition in a decremental motor direction are as follows phaseA_commut_cmds lh_d_0O PWM_phaseA_channel ES_ETPU_PWMMDC_OFF_LOW lt lt 8 ES_ETPU_PWMMDC_OFF_LOW lt lt
60. ster for DC motors PWMMDC Channel 8 PWM commuted PWMC phase A base channel Channel 10 PWM commuted PWMC phase B base channel Channel 12 PWM commuted PWMC phase C base channel Channel 14 analog sensing for DC motors ASDC Channel 15 break controller BC BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 24 Freescale Semiconductor Software Design These eTPU channels are initialized by the fs_etpu_app_bldcmhs1l2_ init eTPU application API function see 4 3 The application settings are as follows PWM phases type is commuted complementary pairs PWM frequency 20kHz PWM dead time 1us Motor speed range 14 000 RPM Motor speed minimum 300 RPM DC bus voltage 9V Number of motor pole pairs 4 Motor speed calculated using HD revolution period Speed controller update frequency 10kHz PI controller parameters P gain is 0 5 0x004000 2715 and I gain is 0 0078125 0x000100 2715 The controller parameters were experimentally tuned Ramp parameters 900ms to ramp up from zero to the maximum speed 900ms to ramp down from the maximum speed to zero Break controller mode PWM based breaking signal is generated in case of over voltage Break control signal polarity is active high DC bus voltage level at which break control signal is ON is 110 of the nominal DC bus voltage DC bus voltage level at which break control signal is OFF is 105 of the
61. system electrical revolutions The revolution counter is incremented or decremented on each revolution based on the current direction Revolution period Determines the TCR time of the last revolution The parameter value is updated each time the sector is changed The revolution period is measured from the last edge of a similar type low high high low on the same channel to the current edge Sector period Determines the TCR time between the last two changes of the sector The parameter value is updated each time the sector is changed The sector period is measured from the last edge to the current edge Last edge time Stores the TCR time of the last incoming edge The HD function also performs commutations of PWMC phases sector PLATE gt To n ARE gt AAA PWMC 2 ANNI id commutation of PWM phases P direction 4 revolution_period sector_period A revolution _counter Sector period pe sector period 4 sector period Figure 23 Functionality of HD For more details about the HD eTPU function refer to Reference 9 4 4 3 Speed Controller SC The speed controller eTPU function is not intended to process input or output signals Its purpose is to control another eTPU function s input parameter The SC function can be executed even on an eTPU channel not connected to an output pin The SC function includes a ge
62. t serve as building blocks for various motor control applications The following paragraphs describe the functionality of each block CPU eTPU Hardware BC gt AILSA gt DC Bus DC bus Break voltage ASDC pannnannnnonn gt ADC Trigger Fault fault interrupt gt LUNN OUST gt applied UU UU UU LUIN gt voltage gt N gt Motor gt EN UUU UU gt Inverter gt Muu UU tL __JL gt NANNAN Me commutation required eo C oe speed E Hall revolution period ro Figure 21 Block Diagram of eTPU Processing m e Sensors BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 33 Software Design 4 4 1 PWM Generator PWMMDC PWMC The generation of PWM signals for motor control applications with eTPU is provided by three eTPU functions e PWM master for DC motors PWMMDC e PWM full range PWMF PWM commuted PWMC The PWM Master for DC motors PWMMDC function calculates a PWM duty cycle and updates the three PWM phases The phases may be driven either by the PWM full range PWMF function which enables a full 0 to 100 duty cycle range or by the PWM commuted PWMC function which enables switching the phase ON and OFF The PWMC function is used in the described application The PWMC function generates the PWM signal
63. tor Theory Voltage U sos Phase A Unc Uncs Phase B Uses Uncs Phase C Ubos 30 60 90 120 150 180 210 240 270 300 330 Electrical angle Figure 3 Voltage Strokes Applied to the 3 Phase BLDC Motor For the common 3 phase BLDC motor a standard 3 phase power stage is used see Figure 4 The power stage utilizes six power transistors that operate in either an independent or complementary mode In both modes the 3 phase power stage energizes two motor phases concurrently The third phase is unpowered see Figure 3 Thus we get six possible voltage vectors that are applied to the BLDC motor using a pulse width modulation PWM technique see Figure 5 There are two basic types of power transistor switching schemes independent and complementary Both switching modes are able to work in bipolar or unipolar mode The presented application utilizes the complementary bipolar PWM mode For more information about PWM techniques refer to Reference 16 gt o U DCB Q1 PWM_Q1 gt PWM_Q3 AP PWM_Q5 gt Cll Q2 Q4 PWM_Q2 gt PWM_Q4 AF PWM_Q6 gt GND Phase_A Phase_B Phase_C Q3 Q5 Q6 Figure 4 3 Phase BLDC Power Stage BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 5 Target Motor Theory 2 1 1 Commutation Commutation provides the creation of a rotational field As mentioned
64. voltage Apart from these pulses for every PWM period a pulse will appear which signals a PWM update The PWM update activity pulse is sometimes narrow and sometimes wide The pulse is wide when BLDC Motor with Speed Closed Loop and DC Bus Break Controller Driven by eTPU on MPC5554 Rev 0 Freescale Semiconductor 41 Software Design anew value of applied motor voltage has been processed it is narrow when no new value has been processed and the PWM duty cycles are not updated The live view on the oscilloscope screen shows that the range of the SC and PWMMDC channel service latencies are very low The only noticeable latency is caused by Hall decoder HD activity The HD eTPU function processes the Hall signals transitions and commutes the PWM phases The Hall signals transitions come asynchronously with the PWM periods The fs_etpu_pwmmdc_init_3ph function parameter update_time enables the user to adjust the position of the PWMMDC activity pulse relative to the PWM period frame The activity pulse has a scheduled update_time prior to the end of the period frame so that the update is finished by the end of the period frame even in the worst case latency Reference 11 describes how to set the update_time value The difference between the values of the fs _etpu_pwmmdc_init_3ph function parameter start_offset and the fs_etpu_sc_init function parameter start_offset determines the position of the SC activity pulse relative to the PWM period f

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