Authors: Grasso, Guardo Brushless motors (BLDC) becoming widely u

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Authors: Grasso, Guardo Brushless motors (BLDC) becoming widely u

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Brushless Motor Fuzzy Control using ST52x301
Authors: Grasso, Guardo
Brushless motors (BLDC) becoming widely used field control motors. These kind synchronous motors used servo drives applications such computer peripherals equipment, robotics, adjustable-speed drives load-proportional capacity-modulated heat pumps, large fans compressors Brushless motors referred many aliases brushless permanent magnet, permanent magnet motors, permanent magnet synchronous motors, etc. confusion arises because brushless motor does directly operate voltage source. generally driven (supplied) from inverter which converts constant voltage 3-phase voltage with frequency corresponding instantaneously rotor speed. advantages BLDC motor sparks absence. brushes motor have several problems regards brushes' life dust residues, maximum speed electrical noise. BLDC motors potentially cleaner, faster, more efficient, less noisy more reliable. However, BLDC motors require more complex electronic control. This application note will show this complexity reduced using ST52x301 Fuzzy controller.
OUTLINE BRUSHLESS MOTORS
Brushless motor physical appearance 3-phase permanent magnet synchronous machine. brushes commutator have been eliminated windings connected control electronics. Electronics replaces function commutator energizes proper winding. energized stator winding leads rotor magnet switches just rotor aligns with stator. synchronous motor drives, stator supplied with balanced three-phase currents, whose frequency number poles motor, then:
where (rad/s) flux synchronous speed that same, rotor speed. This equation links rotor speed phases switching frequency electronic drive. above currents produce constant amplitude flux gap, which rotates synchronous speed Since flux amplitude proportional current amplitude, enough manage winding current level control rotor torque. From Brushless theory [3-4] possible demonstrate that
()(2)
where constant, field-flux, called torque angle. represents angle between phase linked flux fph1 relative stator current Iph1.
January 1999
1/18
AN1113 APPLICATION NOTE
Now, electronic controller able supply phase order maintain =90° equation above simplified Is(3) where called motor torque constant amplitude stator phase currents. From previous considerations clear reason BLDC motor needs always position sensors know exactly rotor position. Fig. shows transversal section typical three phase brushless motor. Figure Three-phase brushless motor
diagram, three position sensors (Hall sensors) placed around rotor order detect shaft position. Fig. reports motor data sheet supplied motor builder. Figure Motor Data Sheet
Linked Voltage Counterclockwise direction
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Brushless Motor Fuzzy Control using ST52x301
observing motor data sheet, these concepts become clear. fact, possible relation between shaft position, hall sensors response voltage profile supplied. This supply stator phases very complex because necessary produce sine wave with proper period delay with respect sensors information. will show later simpler method possible.
INVERTER DRIVER TOPOLOGY
stator brushless motor generally supplied inverter which converts voltage 3-phase voltage whose frequency related speed rotor. Speed control achieved Pulse Width Modulation (PWM) phases voltage accomplished periodically switching phase voltage zero. widely used driver perform this switching six-step inverter where each phase driven means couple transistors. Fig.3 shows basic operating principle this drive. name "six-steps" arises from finite time-steps which whole period shared. During each time step, current direction does change whereas current amplitude increase decrease coil. better explain this operating principle, consider action (phase) inverter, such example Transistor turned 90°and turned =90° while turned =90°. When
Figure Inverter driver operating principle 0/23/2=t
turned off, current carrying immediately diverted diode parallel with This diode re-circulates instantaneous current winding until decreases zero. Once phase current reverses direction carried term voltage easy draw phases voltages conceiving transistors switches. triangular connection phases, each phase voltage depends status legs bridge. Figure shows real phase star voltage phase current. voltage steps evident look like sine wave. same happens other legs bridge different times. This topology drives windings whole period, avoiding phase "floating" (Six-Steps Continuous Mode Inverter).
FUZZY CONTROLLER
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AN1113 APPLICATION NOTE
Figure Phase voltage current
control maintain desired Speed regardless applied load shaft. When resistance torque applied shaft, reduction speed takes place. This implies increment wave period Hall sensors signals then decrement sine frequency phases, follow sensors information. this case, only lead rotor previous speed increase winding current order balance load torque. Fuzzy Controller, fig. performs this task. ST52x301 reads speed
Figure Control topology
Speed_Ref
Error
FUZZY CONTROLLER
MOTOR DRIVER
Speed
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Brushless Motor Fuzzy Control using ST52x301
"Ref" value from Channel0 instantaneous Hall signal period means digital port. software task performs "error" calculation
error VREF speed. variable "Error" also forms Fuzzy Input "Fuzzy Controller" block. Fuzzy algorithm uses three rules compute fuzzy-out, achieving incremental variable drive inverter real-time mode. This incremental method allows manage speed closed loop real-time control, since software task time very short. first rule fully activated when "error" value "neg", i.e. when Vref <<speed. This implies that actual speed shaft higher than "Ref". Then action carry reduce phase current
Figure Fuzzy algorithm
achieve this, necessary decrease duty-cycle. displayed value "-10" good compromise between system stability step response system. This value assigned after some trials using only human reasoning. Instead, duty step higher, example "-20", system will sooner reach "Speed_Ref" overshoot step response could lead instability. above explanation similar other rules. implemented 3-rules fuzzy algorithm simplest control speed. more accurate control could done using first derivative speed improve action strenght means other rules.
HARDWARE DESCRIPTION
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AN1113 APPLICATION NOTE
real implemented system shown schematic below. ST52x301, integrated full-bridge dual drive three AND's enough control BLDC motor. basic idea used this implementation employs Hall sensors direct way. Hall signals "AND-ed" directly with wave produced ST52x301 order supply proper winding. Figure Electrical schematic
Speed Torque
Isense
22pF 20MHz
TRES TCTRL TCLK
OSCOUT OSCIN
AVDD AVSS
MODE TEST RESET TIMEROUT
TRIACOUT
AIN0 AIN1 AIN2 AIN3 READY
MAIN2 MAIN1
ST52x301
Isense
22pF
Brushless Motor
2.2uF
Vpow
74LS00
74LS00
74LS00
L298
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Brushless Motor Fuzzy Control using ST52x301
fact, high frequency wave produces, coil, voltage whose amplitude value mean value square wave. motor data sheet displayed fig. clearly shows that "U-W" phase must supplied positive when sensor "H1" high, "W-V" when sensor "H2" high This true because triangular connection preferred coils arrangement. output then, Pulse train whose duration same Hall signal. This pulses train used drive each bridge L298. L298 monolithic dual full-bridge driver designed accept standard logic levels drive inductive loads such relays, solenoids, stepping motors. Enable input signals available allow software protection. Internal circuitry provides appropriate dead-time order avoid "cross-conduction" along leg. ST52x301 provides, means internal peripheral, wave that varied software. ST52x301 frequency chosen compromise between acoustic noise motor losses power stages bridge. wave frequency used implemented application.
SOFTWARE DESCRIPTION
Before discuss about ST52x301 software configuration, important note some connections schematic. (pin parallel port used enable power stage only after power-on reset, then parallel port must configured mode. analog input AIN0 (pin used read voltage reference. voltage between present this pin, converted range 255. External INTerrupt (27) used read Hall sensor signal period order calculate instantaneous speed. This digital input will configured both negative positive edge trigger produce internal software interrupt. Fig. displays configure peripheral with inputs, TRIAC peripheral mode KHz, used global variables. following figure reports main program term graphical programming. appendix Figure Peripheral configuration
7/18
AN1113 APPLICATION NOTE
this application note contains whole assembler code generated compiler. discuss about main program. "Int_AD_on" "init" blocks fig. used initialize global variables interrupts mask (only enabled). following blocks start converter wait results conversion. After that, converter values stored variable called "speed, "torque", "current" Interrupt mask enabled (only Int). Block "V200_duty" loads Triac counter with default value block "PWM_start" allows TriFigure Main view
peripheral run. this time already possible wave ST52x301. Since reads time period related speed necessary perform mathematical inversion achieve frequency. Just simplify, complementation period byte will made instead inversion. this way, error will introduced spin frequency calculation. more accurate precision requested, alternative method implement inversion fuzzy implementation function 1/T. block "L298_EN_on" enables bridge driver. Block "complemnt" performs above task. Following loop, value speed "torque_ref" "current" read. block "max_research" catches maximum value current during turn shaft. This loop performed until condition "tmp>=2" false. Variable used create time inertia fuzzy control. "Tmp" incremented each time Ext-Interrupt routine executed (each turn shaft) this implies real time control about turn shaft. Block "calc_err" performs error calculation error speed speed error variable sent fuzzy input, Fuzzy block "fuzzy controller" produces incremental value "delta_DC". Next figure shows content mathematics blocks. second, "delta_DC" added subtract, negative) current duty-cycle before refresh Triac counter. operators then introduced avoid overflow underflow counter registers during control. point program Ext_Int routine (fig. 11). This task performs period measurement
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Brushless Motor Fuzzy Control using ST52x301
Figure Arithmetic blocks
square wave supplied Hall sensor. period measured counting time between positive edge following negative edge sensor signal. flag used select edge. coming edge positive, Timer peripheral will started. negative, current Timer counter value will read Timer stopped. Before escape from Ext_Int routine assembler blocks will edge select mask order sense proper next edge. Figure External Interrupt Routine
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AN1113 APPLICATION NOTE
CONCLUSIONS RESULTS
using ST52x301 Fuzzy Controller easy implement real time control with components.The brushless motor control described this application note represents good compromise between system costs motor performances. graphical programming environment reduces development time also expert programmers. Fig. displays phase current star voltage Vu-o. square wave filtered oscilloscope. From this picture possible observe steps current wave that yields distortion theoretical sine wave. higher speed rates distortion becomes lower, although speed, motor performance does degrade. evaluate acceleration characteristics control goodness, some trials were made during softwa-
Figure Phase current
development. Fig. shows free acceleration characteristics starting from given speed shaft reach double speed changing suddenly speed_Ref. dynamic performances this system were compared, term speed load response, with traditional controller with steps drive. substantial differences were issued dynamic performances, costs traditional system higher.
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Brushless Motor Fuzzy Control using ST52x301
Figure
Dynamical performances
Speed_Ref Motor Speed
REFERENCES
Paul Krause "Analysis Electric Machinery" McGraw-Hill "Power Products- Application Manual", STMicroelectronics Mohan, Undeland, Robbins "Power Electronics: Converters, Applications Design" John Wiley Sons Yasuhiko Dote, Sakan Kinoshita "Brushless Servomotors Fundamentals Applications" Oxford Science Publications FUZZYSTUDIO3.0 User Manual, STMicroelectronics, 1998
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AN1113 APPLICATION NOTE
APPENDIX: ST52X301 ASSEMBLER CODE
Source file: C:\TEMP\BLDC_CL.wcl Compile time:Mon 11:01:26 1998 Device type: ST52x301 Compiler version: 01.00 (02.06.98) Timer_Interrupt Triac_Interrupt AD_Interrupt SCI_Interrupt External_Interrupt
data data data stop stop @WCLStart@@: ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf ldcf Start: Int_AD_on: ldcf init: ldrc ldrc ldrc ldrc
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Brushless Motor Fuzzy Control using ST52x301
ldrc ldrc AD_start: ldcf Wait0: waiti Rd_speed: ldri rd_torque: ldri Rd_sense: ldri stopAD: ldcf EXT_on: ldcf restart_ad: ldcf V200_to_duty: mdgi ldrc ldpr megi PWM_start: ldcf ldcf L298_EN_on: mdgi ldrc ldpr megi complemnt: mdgi ldrc megi RD_spee: ldri RD_torq: ldri Rd_Isense: ldri
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AN1113 APPLICATION NOTE
max_reserch: mdgi ldrr megi @00001: ldrr @00000: @00002: tmp_3: mdgi ldrc megi jpns @00004: @00003: @00005: calc_err: mdgi ldrc megi @00007: ldrc @00006: @00008: mdgi ldrc megi jpns @00010: ldrc @00009: complemnt calc_err @@00005
@@00000
@@00004 @@00003
@@00006
@@00010 @@00009
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Brushless Motor Fuzzy Control using ST52x301
@00011: ldrc mdgi ldrr subo megi controller: ldrr stop fzand fzand fzand stop ldri Torque_limit: mdgi ldrr megi @00013: ldrc @00012: @00014: ldrc incr_duty: mdgi ldrc megi mdgi
@@00012
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AN1113 APPLICATION NOTE
ldrc megi jpns @00016: ldrc @00015: @00017: mdgi ldrc megi @00019: ldrc @00018: @00020: new_duty: ldpr External_Interrupt: inv_flag: mdgi ldrc megi mdgi ldrc megi jpns @00022: ldrc @00021: @00023: mdgi ldrc megi flag_is1:
@@00016 @@00015
@@00018
PWM_start
@@00022 @@00021
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Brushless Motor Fuzzy Control using ST52x301
mdgi ldrc megi jpns @00025: @00024: @00026: get_rpm: ldri stop_tim: ldcf on_rise: rint ldcf rint IRET0: reti set_tim: mdgi ldrc ldpr megi start_tim: ldcf ldcf on_fall: rint ldcf rint AD_Interrupt: IRET2: reti SCI_Interrupt: IRET1: reti Timer_Interrupt:
@@00025 @@00024 set_tim @@00026 get_rpm
IRET0
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AN1113 APPLICATION NOTE
IRET4: reti Triac_Interrupt: IRET3: reti stop
Information furnished believed accurate reliable. However, STMicroelectronics assumes responsibility consequences such information infringement patents other rights third parties which result from use. license granted implication otherwise under patent patent rights STMicroelectronics. Specification mentioned this publication subject change without notice. This publication supersedes replaces information previously supplied. STMicroelectronics products authorized critical components life support devices systems without express written approval STMicroelectronics. logo registered trademark STMicroelectronics 1999 STMicroelectronics Printed Italy Rights Reserved STMicroelectronics GROUP COMPANIES
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Authors: Grasso, Guardo Brushless motors (BLDC) becoming widely u

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