Download presentation
Presentation is loading. Please wait.
1
3-Phase Sensorless BLDC Motor Control Using MC9S08MP16
January 22th, 2010 3-Phase Sensorless BLDC Motor Control Using MC9S08MP16 Presentation Libor Prokop System Application Engineer
2
Presentation Outline BLDC Motor Control Generally
Sensorless BLDC with BEMF Zero Crossing DRM117 Sensorless BLDC Motor Control Application
3
BLDC Motor Control Generally
4
6 - Step Commutation Diagram
Six Step BLDC Motor Control Voltage applied on two phases only It creates 6 flux vectors Phases are power based on rotor position The process is called Commutation A B C 0% 1. 3. 5. 2. 4. 6. BLDC ØA Phases voltage ØC ØB
5
6 step (120 Degree) 3-phase BLDC Motor Control
Stator field is maintained 60° to 120° relative to rotor field Therefore the rotor position must be estimated Right Before Commutation Right After Commutation
6
Power Stage – Motor Topology
3-PHASE POWER STAGE B PWM1 PWM3 PWM5 S S S AT BT CT POWER C SOURCE A DC VOLTAGE PWM2 PWM4 PWM6 S S S AB BT CT 3-PHASE BLDC MOTOR MOSFET/IGBT DRIVERS PWM1 PWM2 PWM3 PWM4 PWM5 PWM6 Controller
7
Quadrants of Operation
Current (Torque) Second Quadrant First Quadrant negative speed-positive torque positive speed-positive torque “reverse-braking” “forward-accelerating” Generating Motoring II I Voltage (Speed) III IV Motoring Generating Third Quadrant Fourth Quadrant negative speed - negative torque Positive speed - negative torque “reverse-accelerating” “forward-braking”
8
Bipolar BLDC Commutation (3 Complementary PWM pairs)
Allows energy recuperation BOTTOM is opposite of TOP Requires sophisticated PWM support commutation commutation commutation commutation commutation 120o 60o SAt A - Off A - Off SAt SBt SCt SAb A - Off A - Off SAb SBb SCb B - Off B - Off SBt SBb B - Off B - Off SCt C - Off C - Off C - Off ØB 3phase Brushless DC motor SCb C - Off C - Off C - Off ØA ØC
9
Bipolar BLDC Commutation (Complementary PWMs) Detail
BOTTOM is opposite of TOP Dead Time Dead Time Dead Time Dead Time Dead Time Dead Time SAt A - Off SAb A - Off SBt B - Off SBb B - Off B - Off C - Off SCt B - Off C - Off SCb Dead Time Dead Time Swap Dead Time Dead Time
10
Unipolar BLDC Commutation (3 Complementary PWM pairs)
Allows energy recuperation BOTTOM is opposite of TOP Requires sophisticated PWM support commutation commutation commutation commutation commutation 120o 60o SAt A - Off A - Off SAt SAt SCt SAb A - Off A - Off SAb SBb SCb SBt B - Off B - Off SBb B - Off B - Off SCt C - Off C - Off C - Off ØB 3phase Brushless DC motor C - Off C - Off C - Off SCb ØA ØC
11
Sensorless BLDC with BEMF Zero Crossing
12
Synchronous PM Motors La Lc Lb
Stator Field needs to be close to orthogonal (90°) to rotor field to get maximal torque and energy efficiency: +Vp (PWM) La Running Direction Motor Torque S N Lc 90` Lb Stator Flux GND (PWM)
13
BLDC Motor Back-EMF Shape
V o l t a g e P h a s e B - C V o l t a g e P h a s e C - A V o l t a g e P h a s e A P h a s e B P h a s e C V A C B H 4
14
BLDC Commutation Specifics
1. 2. 3. 4. 5. 6. A B C 0% BLDC ØA ØB ØC USc = UbackEMFc After the commutatation current transient: Ic = 0 and so UC = BEMFC
15
Sensorless BLDC Motor Control with BEMF Zero-Crossing Detection
Appropriate Phase Comparator Output selected Zero Crossing event detected
16
Sensorless Commutation and BEMF
60 120 180 240 300 360 Rotor Electrical Position (Degrees) Phase R Phase S Phase T Zero crossings PWM 1 PWM 3 PWM 5 PWM 2 PWM 4 PWM 6
17
BLDC Central Point Is Not Accessible
3-phase invertor and DC bus current measurement Inverter Stage Udcbus Not Accessible Rshunt Phase c Idcbus Phase b BLDC Motor Phase a
18
BLDC Motor Voltages at Bipolar Switching Phases
Regeneration I 1 1 2 2 - + - + - + - + -V V Q2 Q1 Q3 Q4 Regeneration - + 3 - + 4 - + 3 - + 4 -I PhC PhB PhA Motor Phase A Voltage VDCB 1 2 3 4 VDCB/2 Motor Central Point Voltage V0 GND 1(4) Top Bottom in diagonal on 2(3) Top Bottom in (inverse) diagonal on
19
BLDC Motor Voltage at Unipolar Switching Phases
- + 1 - + 2 1 Top Bottom in diagonal on One cycle in Quadrant 1 2 Two Bottoms on - + 3 - + 4 One cycle in Quadrant 3 3 Top Bottom in diagonal on 4 Two Bottoms on (inverse current) Motor Phase Voltage PhC PhB PhA VDCB 1 2 3 4 VDCB/2 Motor Central Point Voltage U0 Gnd
20
Zero Crossing Sensing Reference
HB1 + HB1 Udcb HB1 - A HB2 + + B V - A - A + HB2 HB2 B V B V - + + - - + C HB3 HB3 - + + HB3 - C - ½ UDCB reference GND reference Virtual CP reference Udcbus BLDC Motor Central Point is not accessible Rshunt HB1 HB2 A BLDC Motor Idcbus B V HB3 C
21
Bipolar Commutation (Complementary PWMs) Detail
BOTTOM is opposite of TOP Top and Bottom in diagonal on Top and Bottom negative in diagonal on SAt A - Off SAb A - Off SBt B - Off SBb B - Off B - Off C - Off SCt C - Off B - Off SCb Dead Time Dead Time
22
Unipolar Commutation (Complementary PWMs) Detail
BOTTOM is opposite of TOP Top and Bottom in diagonal on Two Bottoms on SAt A - Off SAb A - Off SBt B - Off SBb B - Off B - Off C - Off SCt B - Off C - Off SCb
23
Zero Crossing Detection Measurement Window
BOTTOM is opposite of TOP Top and Bottom in diagonal on Two Bottoms on SAt SAb SBt SBb C - Off SCt C - Off SCb Zero-Crossing Sampling Window
24
Back-EMF Zero Crossing Sensing Circuit
½ UDCB reference Phase Selection According to PWM Sector Phase a Udcb Positive MUX Phase b A B V Cout Sampling + Phase c - C Negative MUX Udcb/2 ZC Sampling Window Ud/2 Sampling Window Generator PWM Sync
25
Back-EMF Detection Window
CMT CMT ZC Zero Crossing Detected BLDC Commutation BLDC Commutation Current Recirculation Zero Crossing Detection Process
26
BLDC Commutation with Back-EMF Zero Crossing Sensing
27
Calculation of the Commutation Timing
28
Sensorless Commutation - Forced PLL 2nd algorithm implemented on 3-phase Sensorless BLDC Motor Control Using MC9S08MP16 Regulator 3-phase Power Stage Motor ZC Detector + -
29
Sensorless Commutation Control States
Sensorless commutation needs three commutation states : Alignment Open-Loop Start Sensorless Run Alignment must be performed before every start. Alignment duration and current is dependent on motor electrical and mechanical time constant. Because after alignment, motor is not spinning, there is state a Open-Loop Start between Alignment and Running, in which no Zero Crosses are detected and commutation must be performed manually.
30
Alignment Vector
31
BLDC Motor Vectors at the Start-up
Starting Mode Open Loop Ramp: no feedback Regular Running Mode – Close Loop: Position estimation fedback q b q b supposed rotor position d d a a
32
Open Loop Start Velocity Open Loop Commutation velocity
Ramp Acceleration OL Velocity Desired Closed Loop Commutation velocity Ramp Acceleration CL Alignment Open Loop Start Run Velocity Threshold OLtoRun real speed time Alignment Period
33
3-ph BLDC Motor Control Idc BLDC Current Control and Limitation
34
Speed Controller with Current Limitation
Current (torque) limitation provided with: “slow current limitation control” - 2 ms sampling Desired DC Bus Current Limit Current Limitation PI Controller + Actual DC Bus Current - Speed PI Controller 1/T Velocity Required + To PWM Period Zero Crossing Filtered/Estimated - Velocity Actual
35
Current Control/Limitation
Technique SW current limitation with slow control loop Issue: Problematic current sensing during commutation transient Controller 3-ph BLDC Motor SW current control ADC HW OVC Idc + -
36
Current Sampling at Back-EMF Zero-crossing
Commutation Transient: Current not sensed during commutation transient Back-EMF Zero-crossing Phase Voltage Phase Current DC Bus Current Envelope DC Bus Shunt Current Current Sampling At Back-EMF Zero Crossing
37
Freescale Reference Design DRM117
3-phase Sensorless BLDC Motor Control
38
Freescale Applications for Sensorless BLDC Motor Control
DRM117: 3-phase Sensorless BLDC Motor Control using MC9S08MP16: Uses MC9S08MP16 MCU device with 8-bit S08 core Some peripheral of the MC9S08MP16 are similar with MCF51AG128 FlexTimer module for 3-phase PWM Application s/w written in C-language with some S08 assembler subroutines Design Reference Manual DRM117 document Modular h/w design: 3-phase BLDC/PMSM Low Voltage Motor Control Drive board – 36V, 4A The MC9S08MP16 daughter board module can be replaced with MCF51AG128 daughter board Application demo available New application - Released November 2009 MCF51AG128 application can be based on existing DRM117
39
3-Phase Sensorless BLDC Motor Control Using MC9S08MP16
Application Usage: Fans Compressors Pumps Industrial drives Appliances Application Features: Targeted at the MC9S08MP16 8-bit microcontroller Sensorless 3-phase trapezoidal BLDC motor control with six-step commutation (60, 120 degree control) Three sensorless synchronized commutation control algorithms incorporating One of unipolar or bipolar PWM commutation techniques possible Back-EMF zero crossing used to synchronize six-step commutation with rotor position Running on a Three-phase low voltage (24V) power board MC9S08MP16 daughter controller board FreeMASTER software control interface and monitor Main application components s/w - written in C-code using some library algorithms - available for the MC9S08MP16 h/w - based on Freescale universal motor control h/w modules documentation - DRM
40
3-Phase Sensorless BLDC
Motor Control Using MC9S08MP16 Design Reference Manual Application Code Control page Demo Hardware
41
Simmilar Peripheral to MCF51AG128
3-Phase BLDC/PMSM Low-Voltage Motor Control Drive 3 Phase Inverter DC Bus Voltage & Current Sensing 24V DC Power Input 3 Phase BLDC Motor 3 Phase Voltages Vdcb, Idcb Vphasea,b,c PWM1..6 Over-current FAULT FTM ADC Module HSCMP2 ZC Comparator FTM2 PWM 3pps Generator Simmilar Peripheral to MCF51AG128 SPI PDB1 Synchronization ADC to PWM PDB2 ZC to PWM Synchronization FTM1 Timer Cmt (and) ZC MC33927 driver Config. Zero Crossing Period & Position Recognition Commutation And PWM Control ADC Sensing I/O Ports GPIO Module Sensorless Commutation PWM Duty cycle Superior System Application Monitoring and Control Zero-crossing Period Application Control 1/T MTIM Time Base Desired speed Actual speed USB to COM Convertor SCI Module - On Board Programming Ramp Generation + Speed PI Controller Required speed Freemaster BDM DC Bus Current Limitations - Torque PI Controller MC9S08MP16 Required torque +
42
S/W - Data Flow
43
S/W - BLDC Control State Diagram
44
S/W – Application Flow chart (1)
45
S/W – Application Flow chart (2)
46
Sensorless BLDC Motor Control Using MC9S08MP16 – HCS08 Core Load (slow speed control loop is not considered) Assumptions: Core speed 20MHz Motor Speed 4000rpm, 8 poles => 625us commutation period sensorless BLDC motor direct commutation using comparators PWM frequency – 20kHz Sensorless Run BLDC Direct Commutation Timer Cmt Commutation Timeout 25us (*) Timer Cmt Current dec Timeout 10us (*) Timer ZC Zero-Crossing Detected 20us (*) 55usec -> 10% (*) 100% 625us Ca 300us 12 bit Analog Variables Sensing and Filtering Service ADC service 14us ADC service 14us ADC service 14us ADC service 14us ADC service 14us ADC service 14us 100% 50us 55usec -> 30% (*) 50us (*) Sensorless BLDC Commutation using HSCMP comparators occupies around 10 % and ADC service occupies around 30 % (*) of HCS08 8bit processor computational power at 4000rpm with 8-pole motor and 50kHz pwm.
47
Thanks for Your Attention
Questions and answers Contact: Libor Prokop Freescale 1.maje Roznov pod Radhostem Czech Republic
48
Back-up slides
49
3-ph BLDC Motor Control Idc BLDC Current Control and Limitation 2
50
SW Current Control Commutation Transient: Phase Voltage Phase Current
Current not sensed during commutation transient Phase Voltage Phase Current DC Bus Current Envelope Current Control Current Sampling Current Control DC Bus Shunt Current Tregulator
51
HW Current Limitation Commutation Transient: Phase Voltage
Problematic current sensing Phase Voltage Phase Current HW Current Limitation DC Bus Current Envelope DC Bus Shunt Current
Similar presentations
