AN1916 Application Note
Contents
1. SwitchState STARTAND u_dc_bus gt MIN DC BUS VOLTAGE Figure 6 4 Drive State Machine Transitions 6 4 9 1 Init State After RESET the application state of the machine goes directly to Init State The omega_required_mech and omega_desired_mech are set to zero If the START STOP switch is in START position the machine state remains in Init State till the START STOP switch is switched to STOP position Then the machine state continues to be Stopped State O MOTOROLA 3 Phase BLDC Motor Control with Hall Sensors 15 Software Design 6 4 9 2 Stopped State The omega_required_mech and omega_desired_mech are set to zero The drive is stopped If the START STOP switch is switched to START position and DC Bus Voltage U_DC_BUS is greater or equal to min_DC_bus_voltage the machine state goes to Running State 6 4 9 3 Running State The drive is running The omega_required_mech is set by UP DOWN push buttons or by PC Master If required speed is less than speed_400rpm the omega_required_mech is set to zero If START STOP switch is switched to STOP position or the DC bus voltage is less than min_DC_bus_voltage the machine state goes to Stopped State Each calling of the machine state enables or disables PWM outputs according to variable omega_required_mech 6 4 10 Initialize void The function is called directly after RESET only The function initializes the following blocks of the DSP e ADC initialization e System Timer for LED initi2. 852 26668334 Technical Information Center 1 800 521 6274 HOME PAGE http motorola com semiconductors dsp MOTOROLA HOME PAGE hittp motorola com semiconductors M MOTOROLA Set AN1916 D
3. Sensors to obtain the rotor position The Hall sensors outputs are connected to Quadrature decoder input pins The input pins go through the digital filter to three quadrature timers The timers are set to catch each edge of input signals and call interrupt routine which provide commutation algorithm The Hall Sensor consists of three sensors Sensor A Sensor B Sensor C These sensors comprise six states 001 010 011 100 101 110 Each state determines which phases should be powered by the 3 phase inverter The interrupt routine reads the state of Hall Sensors from Input Monitor Register IMR of quadrature decoder This value is used as pointer to the commutation table Table 4 1 Table 4 2 which includes information about masking and swapping of power transistors The resultant voltage applied to BLDC motor per one electrical revolution is shown on Figure 4 2 6 3 Phase BLDC Motor Control with Hall Sensors MOTOROLA System Concept Table 4 1 Commutation Sequence for Clockwise Rotation Hall Sensor A Hall Sensor B Hall Sensor C Phase A Phase B Phase C O0 0 0 Start of New Edge Interrupt Read new state of Hall Sensors Y Look up new swap and mask values in the table Y Put new value to PWM module Y a Figure 4 3 Commutation Algorithm for Hall Sensors O MOTOROLA 3 Phase BLDC Motor Control with Hall Sensors 7 S
4. cable 12 GND Controller Board DSP56F80xEVM Evaluation Motor Board 12VDC Hall Sensor Conn Table Controller DSP56F803 DSP56F805 DSP56F807 Controller DSP56F803 Hall Sensors Cable DSP56F805 DSP56F807 1B23810 Figure 5 1 Low Voltage Evaluation Motor HW System Configuration The detailed setup including jumper settings can be found in the document Embedded SDK Software Development Kit Targeting Motorola DSP5680X Platform where X means 3 or 5 All the system parts are supplied and documented according the following references e M1 IB23810 Motor supplied in kit ECMTREVAL Evaluation Motor Board Kit e U2EVM Motor Board supplied in kit with IB23810 Motor ECMTREVAL Evaluation Motor Board Kit described in Evaluation Motor Board User s Manual e Ul CONTROLLER BOARD for DSP56F805 supplied as DSP56805EVM described in DSP Evaluation Module Hardware User s Manual e or Ul CONTROLLER BOARD for DSP56F803 supplied as DSP56803EVM described in DSP Evaluation Module Hardware User s Manual The detailed description of individual boards can be found in comprehensive User s Manuals belonging to each board or on http mot sps com motor devtools index himl The user s manual incorporates the schematic of the board descriptions of individual function blocks and bill of materials The individual boards can be ordered from Motorola as a standard product O MOT
5. pins Timer C with 2 pins and Timer D with 4 pins CAN 2 0 A B Module with 2 pin ports used to transmit and receive Two Serial Communication Interfaces SCIO amp SCI1 each with two pins or four additional GPIO lines Serial Peripheral Interface SPI with configurable 4 pin port or four additional GPIO lines Computer Operating Properly COP timer Two dedicated external interrupt pins Fourteen dedicated General Purpose I O GPIO pins 18 multiplexed GPIO pins External reset pin for hardware reset JTAG On Chip Emulation OnCE Software programmable Phase Lock Loop based frequency synthesizer for the DSP core clock Table 2 1 Memory Configuration DSP56F801 DSP56F803 DSP56F805 DSP56F807 Program Flash 8188 x 16 bit 32252 x 16 bit 32252 x 16 bit 61436 x 16 bit Data Flash 2K x 16 bit 4K x 16 bit 4K x 16 bit 8K x 16 bit Program RAM 1K x 16 bit 512 x 16 bit 512 x 16 bit 2K x 16 bit Data RAM 1K x 16 bit 2K x 16 bit 2K x 16 bit 4K x 16 bit Boot Flash 2K x 16 bit 2K x 16 bit 2K x16 bit 2K x 16 bit Other than the fast Analog to Digital converter and the 16 bit Quadrature Timers the most interesting peripheral from the BLDC motor control point of view is the Pulse Width Modulation PWM module Its configuration provides the freedom to efficiently control the BLDC motor The PWM has the following features Three complementary PWM signal pairs or six independent PWM signals Features of comp
6. target development board The PC Master application is part of the Motorola Embedded SDK and may be selectively installed during SDK installation To enable the PC Master operation on the target board application the following lines must be added to the appconfig h file define INCLUDE_SCI SCI support define INCLUDE_PCMASTER PC Master support It can be seen in the chapter Software Design It automatically includes the SCI driver and installs all necessary services The baud rate of the SCI communication is 9600Bd It is set automatically by PC Master driver The detailed PC Master description is provided by the PC Master User s Manual It is stored in the SDK directory help docs pcmasternuser_manual in HTML format DSP Usage Table 8 1 shows how much memory is needed to run the 3 phase BLDC drive in a speed closed loop using Hall Sensors A part of the DSP memory is still available for other tasks Table 8 1 RAM and FLASH Memory Usage for SDK2 3 and CW 4 0 Memory Available Used Used in 16 bit Words DSP56F803 Application Stack Application without DSP56F805 PC Master SCI Program FLASH 32K 9152 5466 Data RAM 2K 964 352 stack 632 352 stack 3 Phase BLDC Motor Control with Hall Sensors O MOTOROLA References 9 References Brushless DC Motor Control using the MC68HC708MC4 John Deatherage and Jeff Hunsinger AN1702 D Motorola Design of Brushless Permanent ma
7. MOTOROLA Order by AN1916 D Semiconductor Application Note Motorola Order Number E Rev 0 6 01 3 Phase BLDC Motor Contents Control with Hall Sensors 1 Introduction of Application Using DSP56F80x Benefit 1 2 Motorola DSP Advantages and Design of Motor Control Application Based on FGature ssc sssfi sscetesscesssssvstheesisees 1 Motorola Software Development Kit 3 Target Motor Theory 3 Pavel Grasblum 4 System Concept eee eee 4 A i i 4 1 Control Technique 6 1 Introduction of Application 5 Hardware Design eee eee 9 Benefit This Application Note describes a design of a 3 phase BLDC Gy SOT ATS DEEN eenden 10 6 1 Data FloW 10 Brushless DC motor drive based on Motorola s DSPS6F80x 6 2 Application State Diagram ll dedicated motor control device The software design takes 6 3 Drive State Machine 13 advantage of the SDK Software Development Kit 6 4 Routines Description 13 developed by Motorola 6 5 Implementation Notes 0 0 0 17 ae 6 6 Communication with PC Master 17 The concept of the application is a speed closed loop BLDC drive using a position Hall Sensor It serves as an example of TPC MASter ninine n ao 18 a BLDC motor control system design using a Motorola DSP with SDK support It also illustrates the usage of dedicated 8 DSP Usage voices 18 motor control libraries that are included in the SDK 9 References rssi 19 This A
8. OROLA 3 Phase BLDC Motor Control with Hall Sensors 9 Software Design 6 Software Design This section describes the design of the software blocks of the drive The software will be described in terms of e Control Algorithm Data Flow e State Transition 6 1 Data Flow The control algorithm of a close loop BLDC drive is described in Figure 6 1 It consists of processes described in the following sections SCI Communication POSITION SENSOR SPEED Hall Sensors SETTING by BUTTONS ee ae Latest Position omega_required_mech Period a Measuring Capture omega_desired_mech MeasuredTime v DirectionSpinning EncoderState Velocity an Calculation Speed Controller PI Controller omega_actual_mech DC_Bus Voltage A D Converter Mask and Swap Calculation u_dc_bus DesVoltage PWMState Y PWM Generation Software Block Hardware Block Figure 6 1 Main Data Flow 3 0 3 10 3 Phase BLDC Motor Control with Hall Sensors Software Design 6 1 1 Processes Latest Position Capture Period Measuring and Velocity Calculation The Latest Position Capture Period Measuring and Velocity Calculation processes relate to the inputs of the Hall Sensors The sensors generate streams of pulses that are captured separately for each sensor by the Input Capture IC function The process Latest Position Capture captures the latest state of Hall Sensors The processes Pe
9. alization e PWM initialization e IRQA and IRQB interrupt initialization e Quadrature timers AO Al A2 and their interrupts initialization e Quadrature decoder initialization e Setting of initial motor position e Setting of PI controller parameters e Quadrature timer A3 and its interrupt initialization for speed measuring 6 4 11 Main void The function calls the Initialize function and then ApplicationStateMachine inside an endless loop 6 4 12 StartMeasure 16 Parameters unsigned long mksPeriodRange Input max measured period in us const char timer_device_name Input pointer to timer name qt_eSecondaryInputSource secondaryInputSource Input secondary input source for timer 3 Phase BLDC Motor Control with Hall Sensors O MOTOROLA Software Design int decoderMode not used The function is called during initialization The function configures the timer for measuring speed The signal source for measuring speed is one of the Hall Sensors 6 4 13 CallbackOnIndexEdge qt_eCallbackType CallbackType void pParam The interrupt function is called each new coming edge of Hall Sensors The function calculates the period between two adjacent edges 6 4 14 CallbackOnEndMeasure qt_eCallbackType CallbackType void pParam The interrupt function is called on each overload of the timer It counts the number of overloads 6 5 Implementation Notes Any noteworthy pieces of information related to the final im
10. bus voltage System Timer Interrupt Handler UP DOWN buttons filter LED blinking and lighting DC bus voltage measuring Speed calculation Speed PI controller calculation setting of new duty cycle to PWM IRQA Interrupt Handler decrement required speed IRQB Interrupt Handler increment required speed IC Input Capture Interrupt Handler QTimers AO A1 A2 reading of encoder state spin direction calculation mask and swap of PWM transistors calculation setting of new mask and swap to PWM Timer Overflow Interrupt Handler QTimer A3 for speed measuring Increment overload counter IC Input Capture Interrupt Handler QTimer A3 for speed measuring calculation of non scaled period of one Hall Sensor channel SCI Serial Communication Interface Communication with PC Master 3 Phase BLDC Motor Control with Hall Sensors O MOTOROLA Software Design 6 3 Drive State Machine The drive can be in one of the following states as shown in Figure 6 3 which also shows transition conditions among the drive states Reset SwitchState START SwitchState STOP SwitchState STOP OR u_dc_bus lt MIN DC BUS VOLTAGE Stopped State Running State SwitchState START AND u_dc_bus gt MIN DC BUS VOLTAGE Figure 6 3 Drive State Machine Transitions 6 4 Routines Description 6 4 1 LedISR void This interrupt routine is called periodically by timer which is set by functi
11. gnet Motors J R Hendershot JR and T J E Miller Magna Physics Publishing and Clarendon Press 1994 DSP Evaluation Module Hardware User s Manual DSP56F805EVMUM D Motorola DSP Evaluation Module Hardware User s Manual DSP56F803EVMUM D Motorola DSP56F800 16 bit Digital Signal Processor Family Manual DSP56F800FM D Motorola DSP56F80x 16 bit Digital Signal Processor User s Manual DSP56F801 7UM D Motorola Evaluation Motor Board User s Manual MEMCEVMBUM D Motorola Web page motorola com semiconductors motor Motorola Software Development Kit SDK O MOTOROLA 3 Phase BLDC Motor Control with Hall Sensors 19 OnCE is a registered trademark of Motorola Inc Motorola reserves the right to make changes without further notice to any products herein Motorola makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does Motorola 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 incidental damages Typical parameters which may be provided in Motorola 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 Motorola does not convey any license unde
12. lementary channel operation Deadtime insertion Separate top and bottom pulse width correction via current status inputs or software Separate top and bottom polarity control Edge aligned or center aligned PWM signals 15 bits of resolution Half cycle reload capability 3 Phase BLDC Motor Control with Hall Sensors O MOTOROLA Target Motor Theory e Integral reload rates from one to 16 e Individual software controlled PWM outputs e Mask and Swap of PWM outputs e Programmable fault protection e Polarity control e 20 mA current sink capability on PWM pins e Write protectable registers The BLDC motor control utilizes the PWM block set in the complementary PWM mode to generate control signals for all switches of the power stage with deadtime generation The PWM outputs can be controlled separately by software which can set the control signal to logical 0 or 1 One feature which is very useful for BLDC motor control is the channel swap function The state of the control signals can be changed immediately when required by the motor position phase commutation without changing the content of the PWM value registers These changes can be accomplished asynchronously to the PWM duty cycle update 3 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 rotor has surface mounted permanent magnets see Figure 3 1 Stator Stat
13. nals it generates 3 phase PWM output signals for the motor inverter 4 3 Phase BLDC Motor Control with Hall Sensors O MOTOROLA System Concept A standard system concept is chosen for the drive see Figure 4 1 The system incorporates the following hardware boards e Power Supply 12V DC 4Amps e EVM Motor Board e BLDC Motor IB23810 e Evaluation Board DSP56F803 or DSP56F805 DSP56F80x EVM DSP56F80x PC Master PI Speed Controller Calculation Commutation START STOP UP Figure 4 1 System Concept The control process is as follows The state of the inputs is periodically scanned while the speed of the motor is measured on each new coming edge from Hall Sensors According to the state of the control signals Start Stop switch speed up down buttons the speed command is calculated The comparison between the actual speed command and the measured speed generates a speed error The speed error is brought to the speed PI controller that generates a new corrected applied voltage The Hall Sensor signals are scanned independently on speed control Each new coming edge of any Hall Sensor signal calls the interrupt routine which calculates new voltage shape applied to the BLDC motor This process is called commutation The PWM transistors work in complementary mode Undervoltage protection of the DC Bus is measured during the control process and is performed by software O MOTOROLA 3 Phase BLDC Motor Control with Hall Se
14. nsors 5 System Concept 4 1 Control Technique The brushless DC motor BLDC motor is also known as an electronically commuted motor There are no brushes on the rotor and the commutation is performed electronically at certain rotor positions The three phase voltage system see Figure 4 2 with a rectangular shape is used to create a rotational torque This easily created shape of applied voltage ensures the simplicity of control of drive The rotor position must be known in order to align energized phases with the rotor s permanent magnetic field The alignment is very important because it results in proper commutation in the PWM inverter where the voltage level is reduced by chopping In this condition the motor behaves as a DC motor and runs at the best working point The simplicity of control and good performance makes this motor a natural choice for low cost and high efficiency applications There are many methods how to provide alignment between back EMF and commutation events The presented application use Hall Sensors to sense the commutation events Voltage A 120 lt Phase A Phase B a aa lo ay H i PhaseC ss electrical 30 90 150 210 270 330 angle Y Figure 4 2 Three phase voltage system applied to BLDC motor 4 1 1 Commutation Algorithm The commutation algorithm provides the generation of a rotational field according to rotor position This algorithm uses the Hall
15. on LedInit This routine executes following functions e LED blinking according to application mode START STOP The period of blinking is given by LED_ISR_COUNT_VALUE x timer period 20 ms e Reading of new sample of DC Bus Voltage and starting of new conversion e Scaling of measured period of one Hall Sensor channel e Speed calculation O MOTOROLA 3 Phase BLDC Motor Control with Hall Sensors 13 Software Design The constant OMEGA_ACTUAL_MECH_CONST is given by following equations position difference 1 4 rev given by each edge of one Hall Sensor phase and two pole pairs motor max period time 0 2 s chosen according to required min speed Vmin 00 position difference max period time 75 rpm Vmax 20 V min 1500 rpm chosen according to required max speed OMEGA_ACTUAL_MECH_CONST 32767 V nin Vmax 1638 e Calculation of new duty cycle by PI controller e Setting of new duty cycle 6 4 2 ISRQTimer void This interrupt routine is called on each edge which is captured on the timers input The timers AO A1 A2 call the same interrupt routine This routine executes following functions e Reading of new Hall Sensors state e Calculation of spin direction e Calculation of transistors mask and swap e Set of transistors mask and swap 6 4 3 Word 16 DirectionCalculation Word16 EncoderState Word16 NextEncoderState Parameters Word16 EncoderState Input Actual state of Hall sensors Word16 Nex
16. or winding in slots Shaft Rotor Air gap Permanent magnets Figure 3 1 BLDC Motor Cross Section In this respect the BLDC motor is equivalent to an inverted DC commutator motor in that the magnet rotates while the conductors remain stationary In the DC commutator motor the current polarity is reversed by the commutator and brushes but in the brushless DC motor the polarity reversal is performed by a power transistor which must be switched in synchronization with the rotor position Therefore the BLDC motor often has either internal or external position sensors to sense actual rotor position O MOTOROLA 3 Phase BLDC Motor Control with Hall Sensors 3 System Concept The presented application uses three Hall Sensors to sense actual position The Hall Sensors signals together give the six output values These outputs are read by DSP and the corresponding output voltage is generated by PWM outputs see Figure 3 2 Phase Back EMF a aes aie Lestat esac E PHASE Rese cauGisty E oll ieee aed Figure 3 2 BLDC Motor Back EMF and Mag Flux Hall Sensor Outputs 4 System Concept The system is designed to drive a 3 phase BLDC motor The DSP runs the main control algorithm According to the user interface input and feedback sig
17. plementation of the preceding design are described here Noted here are the actual design files used any deviations from the design requirements special tricks used in the coding optimizations performed etc 6 5 1 Analogue Value Scaling 6 5 1 1 DC Bus Voltage Scaling The DC_Bus voltage sense is defined by following equation V u_dc_bus 6 32767 Vmax Where u_dc_bus variable of DC Bus voltage Vpc gus measured DC Bus voltage V yax max measurable DC Bus voltage Vmax 16V for EVM Motor Board 6 5 2 PI Controller Parameters The P constant was chosen as 0 122207 32000 218 and I constant was chosen as 0 095367 25000 x18 The controller parameters were experimentally tuned 6 5 3 Velocity Calculation See Section 6 4 1 6 6 Communication with PC Master SCI communication protocol with 9 6kBaud is used for communication with PC The slave communication SW merged into 3 phase BLDC motor control SW is described in the SDK directory Vhelp docs pcmaster commlib in HTML format PC Master controls and senses the status of the BLDC motor application by directly reading and writing of values to the corresponding registers O MOTOROLA 3 Phase BLDC Motor Control with Hall Sensors 17 PC Master 1 8 18 PC Master PC Master was designed to provide the debugging diagnostic and demonstration tool for development of algorithms and application It consists of components running on PC and part running on the
18. pplication Note includes the basic motor theory system design concept hardware implementation and software design including the PC Master visualization tool 2 Motorola DSP Advantages and Features The Motorola DSP56F80x family is well suited for digital motor control combining the DSP s calculation capability with the MCU s controller features on a single chip These DSPs offer many dedicated peripherals like Pulse Width Modulation PWM module Analog to Digital Converter ADC Timers communication peripherals SCI SPI CAN on board Flash and RAM Generally all family members are well suited for various motor controls Cc oO Og OD oc As Jas Oc or 7p nS pl an E 99 The typical member of the family the DSP56F805 provides the following peripheral blocks avy AA MOTOROLA Motorola Inc 2001 Met Motorola DSP Advantages and Features Two Pulse Width Modulator modules PWMA amp PWMB each with six PWM outputs three Current Sense inputs and four Fault inputs fault tolerant design with deadtime insertion supporting both Center and Edge aligned modes Twelve bit Analog to Digital Convertors ADCs supporting two simultaneous conversions with dual 4 pin multiplexed inputs ADC can be synchronized by PWM modules Two Quadrature Decoders Quad DecO amp Quad Dec1 each with four inputs or two additional Quad Timers A amp B Two dedicated General Purpose Quad Timers totaling 6
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20. riod Measuring and Velocity Calculation read the time between the adjacent rising edges of Hall sensor output and calculates the actual motor speed omega_actual_mech 6 1 2 Process Speed Controller The process calculates the duty cycle of the PWM based on the output of the speed controller the PI controller 6 1 3 Process Mask and Swap Calculation The process calculates which PWM channel is enabled for PWM generation and which phase is swapped 6 2 Application State Diagram Reset Initialization Main loop State Machine Figure 6 2 Application State Diagram As Figure 6 2 shows the application state consists of the initialization routine followed by main loop with background tasks The time critical functions are calculated by the interrupt routines O MOTOROLA 3 Phase BLDC Motor Control with Hall Sensors 11 Software Design 12 The brief description of the 3 ph BLDC motor control follows Initialization Routine entered after RESET ADC initialization System Timer for LED initialization PWM initialization IRQA and IRQB interrupt initialization Quadrature timers AO Al A2 and their interrupt initialization Quadrature decoder initialization getting of initial motor position setting of PI controller parameters quadrature timer A3 initialization for speed measuring Main Loop Application state machine check of START STOP switch state check of DC
21. tEncoderState Input Output pointer to expected state of Hall Sensors The function returns a value of 1 or 1 according to spin direction 6 4 4 LedInit void This function is called during initialization only and sets system timer with period 20 ms The system timer calls an interrupt routine named LedISR 6 4 5 IncrementVariable int Variable int Increment int Limit The function increments the variable pointed to by VARIABLE by Increment up to Limit 6 4 6 DecrementVariable int Variable int Decrement int Limit The function decrements the variable pointed to by VARIABLE 14 3 Phase BLDC Motor Control with Hall Sensors O MOTOROLA Software Design 6 4 7 UpButtonISR void The interrupt function is called when the UP push button is pushed The function increments variable omega_required_mech by speed_increment up to speed_up_limit If omega_required_mech is equal to zero the omega_required_mech is directly set to minimal speed speed_400rpm 6 4 8 DownButtonISR void The interrupt function is called when the DOWN push button is pushed The function decrements variable omega_required_mech by speed_increment up to speed_down_limit If omega_required_mech is equal to zero the omega_required_mech is directly set to minimal speed speed_400rpm 6 4 9 ApplicationStateMachine void Reset SwitchState START SwitchState STOP SwitchState STOP OR Stopped u_dc_bus lt MIN DC BUS VOLTAGE State Running State
22. ystem Concept The generation of the PWM voltage waveforms is done by using of masking and swapping without changing of the PWM Value Register duty cycle This method allows independence of commutation and speed control Figure 4 4 shows the generated voltage waveforms for Hall Sensors state A 0 B 1 C 0 at clockwise direction The phase A is masked disabled The voltage polarity of phase C is changed by swapping of upper and bottom transistor The resulting voltage applied on the motor is Ugc The Value Registers of all PWM outputs remain unchanged Figure 4 4 Voltage Waveforms for the Hall Sensors State A 0 B 1 C 0 Clockwise Direction Warning For the 56F80x revision B the mask feature works properly in the independent mode Therefore it is necessary to use software control to implement the mask feature in the complementary mode 4 1 2 Speed Control The speed of BLDC motor is controlled by amplitude of applied voltage The amplitude of applied voltage is regulated by pulse width modulation PWM The main advantage of the described application is the independence of the commutation algorithm and the speed control algorithm 8 3 Phase BLDC Motor Control with Hall Sensors O MOTOROLA Hardware Design 5 Hardware Design The motor control system is designed to drive the 3 phase BLDC motor in a speed closed loop on EVM Motor Board ECMTREVAL The system configuration is shown in Figure 5 1 40w flat U2 ribbon U1
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