Sensorless Vector Control and Implementation: Why · PDF fileChallenges in implementing...
Transcript of Sensorless Vector Control and Implementation: Why · PDF fileChallenges in implementing...
Renesas Electronics America Inc. © 2012 Renesas Electronics America Inc. All rights reserved.
Sensorless Vector Control and Implementation: Why and How Shalabh Goyal, Marketing Manager
© 2012 Renesas Electronics America Inc. All rights reserved. 2
Shalabh Goyal
Focus : Motor control and Appliances
Title: Sr. Marketing Manager, Renesas
Experience: Mixed-signal electronics and microcontrollers for consumer and industrial markets.
Education: Ph.D. degree in EE from Georgia Institute of Technology (2002-2006)
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Renesas Technology & Solution Portfolio
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Microcontroller and Microprocessor Line-up
Wide Format LCDs Industrial & Automotive, 130nm
350µA/MHz, 1µA standby
44 DMIPS, True Low Power
Embedded Security, ASSP
165 DMIPS, FPU, DSC
1200 DMIPS, Performance 1200 DMIPS, Superscalar
500 DMIPS, Low Power
165 DMIPS, FPU, DSC
25 DMIPS, Low Power
10 DMIPS, Capacitive Touch
Industrial & Automotive, 150nm
190µA/MHz, 0.3µA standby
Industrial, 90nm
242µA/MHz, 0.2µA standby
Automotive & Industrial, 90nm
600µA/MHz, 1.5µA standby
Automotive & Industrial, 65nm
600µA/MHz, 1.5µA standby Automotive, 40nm
500µA/MHz, 35µA deep standby
Industrial, 40nm
242µA/MHz, 0.2µA standby
Industrial, 90nm
1mA/MHz, 100µA standby
Industrial & Automotive, 130nm
144µA/MHz, 0.2µA standby
2010 2013
32
-bit
8
/1
6-b
it
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Challenge: Sensorless vector control increases the energy efficiency of motor control systems that drive the smart society. However, understanding and implementing sensorless vector control is a herculean task.
Solution:
This class will help you understand key challenges associated with sensorless vector control and how to implement it using Renesas microcontrollers
‘Enabling The Smart Society’
MCU
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Agenda
Need for vector control
Theory behind vector control
Challenges in implementing sensorless vector control
RX62T MCU family for sensorless vector control
Renesas motor control solutions
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Macro Factors Driving Need for Energy Efficiency
Global Environmental Concerns
Energy Efficiency Policies
New Initiatives
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Realizing Energy Efficiency in Motor Control
Industrial 44% Residential 26% Others 30%
Energy Efficient Motors
Electronic Control
Variable speed drives
Vector control
Direct torque control
Power factor correction
Motor Design
Motor Type
Up to ~30% savings
15% 20%
Motors (45%)
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Sensorless Vector Control Theory
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Permanent Magnet AC Motor
Complex Control
Sinusoidal stator current produces rotating field
Rotor mounted magnetic field is rotating
Maintain stator field orthogonal to rotor field
rsk .
X
A
A’
X B
B’ C’
X C
A B C
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Vector Control Challenge
Maintain orthogonality
Error correction feedback loop
– In-phase current = 0
– Orthogonal current set per torque requirements
What parameters to adjust
Voltage magnitude (PWM duty cycle)
Need to transform current vectors to rotor frame
Rotor Field
Stator Field
900
ωr
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Reference Frame Transformation
Vector control advantages
Maximizing torque (efficiency)
Independent control of flux and torque
Snappy torque control for load variation
Mapping
qi
di
2-phase Rotor Frame Three-phase Stator
u i
w i
v i
0 120
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Current Transformation to 2-ph Rotor Frame
Step 1 : 3-ph to 2-ph conversion
c
b
a
i
i
i
i
i
2
3
2
30
2
1
2
11
i
i
I
I
q
d
cosθsinθ
sinθcosθ
u i
w i v i
F
Clarke Transformation
w
uvw
stationary frame
i
i
F w
αβ
stationary frame
d I
q I F q -
axis
d - axis
Park Transformation
w
dq
rotatory frame
Step 2 : 2-ph stationary frame to 2-ph rotor frame (rotating)
Rotor position (θ) needed
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Sensorless Vector Control
Lower cost but more complex implementation
Current and motor parameters to estimate rotor position
Increased reliability
Reduced cost of sensor ($3-$20)
Less physical space needed
Need to estimate θ without sensors
Speed
/position
sensor
Speed
Calculation
Motor
PWM
Generation PI
Controller
PI
Controller
ω*
ω
i* i
θ
Position
Estimation
i
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dt
diRv s
Lirm cos
Lirm sin
Lirm cos Lirm sin
is the rotor flux linked m
is the rotor position r
Flux Linkage Voltage Equation
=0 =0
Motor Model in Frame
dt
diRv s
Potential Inaccuracy: If full load or large motor
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Rotor Position and Speed Estimation
rm cos rm sin
)arctan(
r
dt
dw
Bottleneck: arctan implementation takes several CPU cycles
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Renesas Flux Observer Model
dtiRv s
t
)(0
0
dt
diRv s
,
,,
e
Potential inaccuracy: Noise in measuring current and voltage
Potential inaccuracy: Effect of temperature on resistance
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,e
nnn d )1(,)(,1024
1023 1 nnn yyd
Low pass filter
yn
Derivative
dn
dt
d
Low pass filter
,11024
1023eyy nn
)(, n
Cascaded low pass filters rather than direct integration
First low pass filter
Derivative
Second low pass filter
Negate the effect of DC offset in measured current/voltage
Flux Observer Implementation
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Sensorless Vector Control Loop
abc to αβ
ia
ib
dq To αβ
vα
vβ
αβ to
abc
Speed Estimation
θ
ωr
ω*r
id Regulator id*=0
id iq
iq Regulator
Speed Regulator
Iq*
3-ph Inverter
6 Sine PWM
DC
BUS
αβ to dq
iα
iβ
θ
Flux and Position Observer
Clarke Park
Park-1 Clarke-1
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Implementation Challenges
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High performance CPU, FPU
Implementation Challenges
1. Computation intensive routines
12Bit Simultaneous Sampling ADC
2. Multiple current/voltage measurement
Noise immunity, PWM shut off
3. Robust performance
On-chip analog, data flash, dual motor
4. Cost effective design
Requirements MCU Considerations
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1. Computation Intensive
High-performance RX600 Core
100MHz CPU
1-cycle flash access
32x32 H/W multiplier
32/32 H/W divider
32bit Barrel Shifter
Floating point unit
• Clarke/Park Transformations
• Flux Estimation
• Rotor position and speed
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Floating Point Unit Advantages
Performance
Wide range and high resolution
No scaling, overflow or saturation
Reduced code size
Ease of Use
Ease of coding, reading, debugging
Compatible with the C/Matlab simulation code
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Floating Point : Range and Resolution
-210
-103
+210
+103
Range
Resolution 2-21
10-7
..0..
Fixed Point Q11.21 Single Precision
Floating Point
..0..
-1038 +1038 Range
Resolution 10-39
∫ or ∑
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Fixed-point Calculations Requires Scaling
X(n) = X(n-1) + A1 * E(n)
(16b, Q12.4) (16b, Q8.8) (32b,Q14.18)
(32b,Q20.12)
(32b,Q14.18)
MULT
SHIFT
(32b,Q14.18)
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No Scaling Needed
FPU Implementation Fixed-Point Implementation
SHIFT
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No Saturation Check
Fixed-Point Implementation
Check for
Saturation
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Reduced Code Size
FPU Implementation Fixed-Point Implementation
FPU instructions make code and the execution time smaller
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Readability
Fixed-Point Implementation FPU Implementation
Parameters Parameters
Park Transformation Code Park Transformation Code
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FPU Brings Ease of Simulation
•Portable to FPU
•Bidirectional
•Time-consuming
•Unidirectional
Simulation Platform
Inherently
floating point
Floating Point Algorithm
Fixed Point CPU
Fixed Point Algorithm
Floating Point CPU
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FPU Implementations
No Load/Store Instructions
Renesas RX FPU
Floating-Point Unit
Dedicated Data Registers
General Registers
Traditional FPU
Load/Store
General Registers
Floating-Point Unit
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2. Accurate Analog Signal Measurement
Simultaneous sampling ADC
Oversampling current waveform
Filtering to mitigate noise
Dual registers for 1-shunt
U
V
W
50us
5us
4 ADC Samples
• Estimates based on current and voltage
• Integration for flux estimation
• Multiple simultaneous measurements
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Current Measurement Techniques
3-shunt
U
V
W
IW IW+IV
1-Shunt Advantages
Cost reduction (Res, PGA)
No need for 3-ph calibration
Reliability
1-shunt Challenges
ADC samples twice quickly
Reconstruction of current
1-shunt
IW,V,U
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Support for 3-shunt and 1-shunt Detection
AN0
AN1
AN2
Mul
tipl
exer
ADC Set 1
A/D
Register 2
Register CH1
Register CH2
Register CH3
ch0
PGA S/H
S/H
S/H S/H
External Reference
3 S/H for 3 shunt current detection
AN03/CVref L
Register 1
Double register for 1-shunt
12-bit ADCs with 1us conversion time
Double register for 2 samples
3S/H for one-shot sampling of three phase currents
Self-diagnostic capability for UL/IEC safety requirements
PGA
PGA
Window Comparators
CPU Interrupt
PWM Shut off (POE)
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3. Robust Performance
Noise immune MCU design
Careful power/ground layout
Pin noise filtering
5V option
On-chip hardware
POE circuit
Fast window comparators
• Susceptibility to noise
• Hardware shut off
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4. Cost Effectiveness
Complete solution for driving two 3-ph
motors
6 programmable gain amplifiers
6 window comparators
2 x 3ph cPWM timers
2 x quadrature encoder inputs
Data flash
Scalability
RX6xT – package, ROM
RX200 - performance
• On-chip integration
• Scalability
48-144 pins
32-512KB
63TL
62T
63TH
Scalability
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Implementing Sensorless Vector Control Using RX62T
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RX62T Motor Timer Set (MTU3)
100MHz, 16bit Timers
Protection Features PWM shut down (Ext, Comparator,
Clock)
Mode registers inaccessible during operation
ch0
ch1
ch2
ch3
ch4
ch5
MTU3
3-phase cPWM O/P U,V,W
ch6
ch7
3 Input Captures
3-phase cPWM O/P U,V,W
Quadrature Encoder1 A,B,Z
Quadrature Encoder2 A,B,Z
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Hardware Implementation
Motor
Current
6
PWM Generation
PWM Shut Off
PGA S/H
12-bit ADC
Analog Unit 0
RX62T
RX600 CORE
x3 Comparator 3
3-phase inverter
Gate Driver
MTU CH3/4
3
3-phase BLDC
Motor
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Software Implementation
Initialization
PWM Interrupt
Current Reconstruction
Speed PI Last ω &
Reference ω
V(u,v,w) -> PWM Duty
New θ Estimation
New Speed Estimation
Current PI
Voltage (d,q)
VBUS/Current Measurement
(u,v,w) -> (α,β) ->(d,q)
Last θ
Reference
Current
Actual
Current
(d,q) -> (α,β) (u,v,w) <-
Last θ
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Fixed point vs. FPU Comparison
Algorithm: Sensor less Vector Control with 1-Shunt Current Detection
PWM Carrier Frequency: 20kHz
Current Loop: 10kHz
Renesas
Inverter Board
RX62T
Starter Kit
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CPU Bandwidth Usage
0% 5% 10% 15% 20% 25% 30% 35% 40%
Sine,Cosine,Atan Functions
Look-up Table
Floating Point
Fixed point
CPU BW
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CPU Bandwidth Usage
0 10 20 30 40
PI Loop
Clarke and Park
Position Estimation
Current Measurement
Overall
Floating Point
Fixed point
us
Floating-point code 40% faster
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Code Size
0 50 100 150 200 250
PI Loop
Clarke and Park
Position Estimation
Current Measurement
Floating Point
Fixed point
Floating-point code size is 45% lower
B
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Driving Two 3-Phase BLDC Motors
RX600 Motor Kit External Inverter
www.renesas.com/rxmotorkit
Motor #2 Motor #1
Sensorless Vector Control
Floating point math
CPU BW used <50%
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Implementation for Two Motor Control
Control
Loop 1
Control
Loop 2
CPU Available
MTU.CH3/4
10KHz
MTU.CH6/7
10KHz
Software Implementation
Control loop executed at Timer underflow interrupt
Both interrupts at same priority level
Alternate Implementations
Control loops at different rates
Interrupt at overflow/underflow
MTU.CH3/4
10KHz
MTU.CH6/7
20KHz
Control
Loop 2
Control
Loop 1
© 2012 Renesas Electronics America Inc. All rights reserved. 47
Software Implementation
Initialization
PWM Interrupt
Current Reconstruction
Speed PI Last ω &
Reference ω
V(u,v,w) -> PWM Duty
New θ Estimation
New Speed Estimation
Current PI
Voltage (d,q)
VBUS/Current Measurement
(u,v,w) -> (α,β) ->(d,q)
Last θ
Reference
Current
Actual
Current
(d,q) -> (α,β) (u,v,w) <-
Last θ
PWM Interrupt2
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Performance Comparison with a High-end DSP
RX62T offers tremendous value
Comparable performance
Significantly lower cost
Loop execution
Code size
System Cost
High-end DSP
RX62T
16us
18us
+50%
7.8KB
7.4KB
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Response to Step Change in Load
950
960
970
980
990
1000
1010
1020
1030
1040
1050
0.265 6.343 22.906
Sp
ee
d (
rpm
)
time
High-end DSP
RX62T
© 2012 Renesas Electronics America Inc. All rights reserved. 50
Renesas Motor Control Solutions
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Motor Control MCUs
RX600 Family
-Dual motor vector control
-Floating point
-RX600 Motor Kit RX62T 100MHz, 165DMIPs
64KB – 256KB
RX220 32MHz,50DMIPs
32KB-256KB
RX200 Family
-Single motor vector control
-Entry level RX core
Timeline
Performance
RL78/G14 32MHz, 44DMIPs
32KB – 256KB
RL78/G14
-Scalar control (low-end
vector control)
-RL78 Motor Kit
RX Core
RX63TL 100MHz, 165DMIPs
32KB – 64KB
RX63TH 100MHz, 165DMIPs
256KB – 512KB
R8C/3xM 20MHz
8KB – 128KB Oct.2012
© 2012 Renesas Electronics America Inc. All rights reserved. 52
Evaluation Kits for Vector Control
Extensive Code Support
Flexibility to Evaluate and Develop
GUI
External Inverter Connector
RX600 Motor Kit RL78 Motor Kit
© 2012 Renesas Electronics America Inc. All rights reserved. 53
High Voltage Demo Platform (2KW)
IGBTs RJH60D5DPQ-A0
Interleaved PFC
AC to DC rectifier
Line AC
85-265V
CPU Board
Gate
D
river
PWM
Hall and Encoder
Current Sense
In-circuit Scope
LCD
Potentiometer and
Push Buttons
Set RPM RPM Is Iq Vdc
© 2012 Renesas Electronics America Inc. All rights reserved. 54
2KW Inverter Platform
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Summary
Sensorless vector control improves the motor system efficiency
Implementing sensorless vector control requires careful selection of MCU
Renesas provides several motor control MCUs depending on the application requirements
RX600 and RL78 motor control kits are available for an easy evaluation of Renesas solutions
High voltage platforms are also available
© 2012 Renesas Electronics America Inc. All rights reserved. 56
Questions?
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Challenge: Sensorless vector control increases the energy efficiency of motor control systems that drive the smart society. However, understanding and implementing sensorless vector control is a herculean task
We discussed key challenges associated with sensorless vector control and how to implement it using Renesas microcontrollers
Do you agree that we accomplished the above statement?
‘Enabling The Smart Society’
MCU
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