Atmel AT32UC3 Series Installation and operating instructions

AVR32710: Space Vector Modulation using AVR32 UC3
Microcontroller
Features
•Brushless DC Motor
•Space Vector Pulse Width Modulation using 6 PWM channels
•Source Code for GCC compiler
•Use AVR®32 Digital Signal Processing library (DSPLib)
1. Introduction
This application note outlines a demonstration using a stand-alone application on an
AVR32 target. It is a real-time system that computes Space Vector Modulation on a
Brushless DC Motor.
The Space Vector Modulation technique is described in application note AVR435
available on www.atmel.com.
This application is designed to work with the EVK1100 evaluation kit, therefore all the
following information is specific to this board and this specific microcontroller
(AVR32UC3A). Additionally, this application can be easily used by the EVK1101 eval-
uation kit and the specific microcontroller (AVR32UC3B).
Figure 1-1. Block Diagram
HallA
HallB
HallC
BLDC
Motor
Hall Sensors
U
V
W
Vn
6 PWMs
channels
3 GPIO
inputs
DSP
Library
Scheduler
LCD Display
AVR32UC3
Rev. 32094B-AVR32-05/09
32-bit
Microcontroller
ApplicationNote

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AVR32710
2. Related Parts
This document applies to the following AT32UC3 parts:
• AT32UC3A0512
• AT32UC3A0256
• AT32UC3A0128
• AT32UC3A1512
• AT32UC3A1256
•AT32UC3A1128
• AT32UC3B0256
• AT32UC3B0128
• AT32UC3B064
• AT32UC3B1256
•AT32UC3B1128
• AT32UC3B164
3. Related Items
The software provided with this application note requires several components:
–AVR32 GNU Toolchain: AVR32 GNU Toolchain is a set of standalone command line
programs used to create applications for AVR32 microcontrollers (compiler,
assembler, linker, debugger).
http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4118
•or
–IAR Embedded Workbench®for Atmel AVR32: IAR Embedded Workbench
provides a suite of AVR32 development tools for embedded systems (compiler,
assembler, linker, debugger). http://www.iar.com/
•EVK1100: The EVK1100 is an evaluation kit and development system for the AVR32
AT32UC3A microcontroller.
http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4114
•EVK1101: The EVK1101 is an evaluation kit and development system for the AVR32
AT32UC3B microcontroller.
http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4175
•AVR32 UC3 Software Framework: This framework provides software drivers and libraries
to build any application for AVR32 UC3. This is where the DSPLib is located.
http://www.atmel.com/dyn/products/tools_card.asp?tool_id=4192
•AT32UC3A0512 Datasheet:
http://www.atmel.com/dyn/products/product_card.asp?part_id=4117
•AT32UC3B0256 Datasheet:
http://www.atmel.com/dyn/products/product_card.asp?part_id=4174
•Space Vector PWM Software Package: avr32710.zip

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4. Abbreviations
•BLDC: Brushless Direct Current
•SVPWM : Space Vector Pulse Width Modulation
•CW : Clockwise direction / CCW : Counter Clockwise direction
•FCPU : CPU frequency
•FPBA : Peripheral Bus A frequency

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5. Motor Control Theory
5.1 Introduction
The most common method used to control DC motors is to modulate the voltage and especially
the duty cycle. This is called the Space Vector Pulse Width Modulation (S.V.P.W.M).
At first, this application note describes the S.V.P.W.M technique and then how to implement
BLDC motor control algorithm on AVR32 UC3 devices.
5.2 Space Vector Pulse Width Modulation Principle
5.2.1 Phase Switching
Figure 5-1. Typical structure of the application
Figure 5-1 shows the typical structure of a BLDC motor connected to a Voltage Source Inverter.
Since the motor is considered as a balanced load with an unconnected neutral,
then
For this three phase power inverter, there are eight possible switching states.
UH
UL
VH
VL VL
WH
HallA
HallB
HallC
BLDC
Hall Sensors
U
V
W
Vn
Vdc
0=++ cnbnan VVV

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Figure 5-2. Possible switching configurations of a 3-phase inverter
These combinations generates eight 3-phases voltages combinations
Table 5-1. Switching configurations and output voltages of a 3-phase inverter
WH VH UH Van Vbn Vcn
0 0 00 0 0
0 0 1 -Vdc/3 -Vdc/3 +2Vdc/3
0 1 0 -Vdc/3 +2Vdc/3 -Vdc/3
0 1 1 -2Vdc/3 -Vdc/3 -Vdc/3
1 0 0 +2Vdc/3 -Vdc/3 -Vdc/3
1 0 1 Vdc/3 -2Vdc/3 Vdc/3
1 1 0 Vdc/3 Vdc/3 -2Vdc/3
1 1 10 0 0
Possible Switching Configuration of a 3-phase inverter

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5.2.2 New Space Vectors using Clarke Transformation
Figure 5-3. Basic Space Vectors
These 3-phases voltage combinations are converted by Clarke transformation and could be
expressed in complex form.
In sector (1), for example,
So,
(1)
(2)
(3)
(4)
(5)
(6)
d
q
V1
V2V3
V4
V5 V6
θ j
smseVV =
*
θ
1Vd x
2Vd y
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
⎥
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎢
⎣
⎡
Π
−
Π
+
Π
−
Π
−
=
⎥
⎦
⎤
⎢
⎣
⎡
cn
bn
an
qs
ds
V
V
V
K
V
V.
)
6
cos()
6
cos(0
)
3
cos()
3
cos(1
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
⎥
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎢
⎣
⎡
−
−−
=
⎥
⎦
⎤
⎢
⎣
⎡
cn
bn
an
qs
ds
V
V
V
V
V
2
3
2
3
0
2
1
2
1
1
3
2

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It implies as well that switching configuration tables could be expressed in (d-q) format
Each space vector corresponding to WH,VH and UH could be expressed as a combination of
Vds and Vqs (vector list in Figure 5-2). This mean for example (WH,VH,UH)=(1,0,0)=V5
5.2.3 Stepping increment and sampling frequency
In this case, it is possible to define any stator voltage as:
With
As shown in Figure 5-3, the angle decomposes every step of Space Vector computation algo-
rithm. As the expression of stator voltage is identical in all the 6 sectors, it is possible to only
compute equation (1) and (2).
But, every step in computation is given for a angular frequency (in cycles/sec) :
The Ftick is defined as the sampling frequency or the basic frequency of the application. n is the
angle stepping increment from the range
For example, with a frequence of tick equal to 20KHz and a resolution up to 8 bits,it is possible
to define a step range from [0;78] thus an angle precision of 0.77 degree.
As the UC3 family has DSP instructions support, the sinus and cosinus computation will be done
in software for SVPWM and not with a lookup table. Thus, it is possible to define a specific reso-
lution for an application.
Table 5-2. Switching configurations and output voltages of a 3-phase in (d-q) format
WH VH UH Vds Vqs Vector Sector
0 0 1 2Vdc/3 0 V1 (1)
1 1 0+Vdc/3 +Vdc/3 V2 (2)
0 1 0-Vdc/3 +Vdc/3 V3 (3)
1 1 0 -2Vdc/3 0 V4 (4)
1 0 0 -Vdc/3 -Vdc/3 V5 (5)
1 0 1 Vdc/3 -Vdc/3 V6 (6)
yyxs UddxUeVV +==
θ
max
)2()sin(
)1()
3
sin(
θ
θ
=
−
Π
=
dy
dx
n
Ftick
nresolution ××
Π
=2
3
)( θ
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
resolution
Ftick
2
;0

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6. Motor Control Processing computations
6.1 Flow Chart Diagram
From the SVPWM technique, it is possible to distinguish several actions:
• Sector Determination
•PICorrector
• Space Vector Computation
Before starting application development, it could be interesting to consider clock source
reference:
• Sector Determination: at every hall sensors interrupt a new sector position is reached. So
that means that this interrupt should trigger a task that compute Sector Determination
Algorithm (electrical position of stator).
• Space Vector Computation
Here is the flow chart diagram for the process in this application.
Figure 6-1. Flow chart diagram
Task #1
Every ‘Period regulation’ period the corrector (Proportionnal and Integer: P.I) is executed and
updates amplitude factor used by the S.V.P.M.
Task #2
Every ‘tick’ period in the Space Vector calculation is computed.

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6.2 Space Vector Modulation
For an efficient implementation of SV-PWM, we use DSP library for cosinus and sinus
computation.
Once dx and dy are calulated, a set of 3 compare values Ta,Tb and Tc need to be calculated
every PWM period to generate this pattern.
Figure 6-2. PWM output switching pattern case in Sector 1
)sin(
)
3
sin(
θ
θ
=
−
Π
=
dy
dx
2*T
T
dx dy t0t0
PWM2
PWM1
PWM0
Tc
Tb
Ta

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We can say that for this sector 0:
The Table 6-1 shows all duty cycle values for each sector number. For a sector number the duty
cycle for the six half bridge is expressed by:
UH = PWM0 and UL = T-(PWM0)
VH = PWM1 and VL = T-(PWM1)
WH = PWM2 and WL = T-(PWM2)
The two rotating directions are described. In case of CCW direction, that means the rotor follows
the sequence Sector number = {6,5,4,3,2,1} and in case of CW direction, the sequence
{1,2,3,4,5,6}.
Table 6-1. PWM duty cycle results with SVPWM computation
Sector
Number q direction = CCW direction = CW
1
PWM0 = (T - dx -dy)/2
PWM1 = (T + dx -dy)/2
PWM2 = (T + dx + dy)/2
PWM0 = (T + dx + dy)
PWM1 =( T - dx - dy)
PWM2 = (T - dx + dy)
2
PWM0 = (T - dx + dy)/2
PWM1 =( T - dx - dy)/2
PWM2 = (T + dx + dy)/2
PWM0 = (T + dx + dy)/2
PWM1 = (T + dx - dy)/2
PWM2 =( T - dx - dy)/2
3
PWM0 = (T + dx + dy)/2
PWM1 = (T - dx - dy)/2
PWM2 = (T + dx - dy)/2
PWM0 = (T - dx + dy)/2
PWM1 = (T + dx + dy)/2
PWM2 = (T - dx - dy)/2
4
PWM0 = (T + dx + dy)/2
PWM1 = (T -dx + dy)/2
PWM2 = (T - dx + dy)/2
PWM0 = (T - dx -dy)/2
PWM1 = (T + dx + dy)/2
PWM2 = (T + dx - dy)/2
5
PWM0 = (T + dx - dy)/2
PWM1 = (T + dx + dy)/2
PWM2 = (T - dx - dy)/2
PWM0 = (T - dx - dy)/2
PWM1 = (T - dx + dy)/2
PWM2 = (T + dx + dy)/2
6
PWM0 = (T - dx - dy)/2
PWM1 = (T + dx + dy)/2
PWM2 = (T - dx + dy)/2
PWM0 =( T + dx -dy)/2
PWM1 = (T - dx -dy)/2
PWM2 = (T + dx + dy)/2
(
)
ac
axb
yx
a
TTT
TdT
ddT
T
−=
+=
−
−
=2
0π
3
---[,]
π
3
---2π
3
------[, ]
2π
3
------ π[,]
π4π
3
------[, ]
4π
3
------ 5π
3
------[,]
5π
3
------ 2π[,]