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

6 PWMs

channels

3 GPIO

inputs

DSP

Library

Scheduler

LCD Display

AVR32UC3

Rev. 32094B-AVR32-05/09

32-bit

Microcontroller

ApplicationNote

32094B–AVR32–05/09

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

32094B–AVR32–05/09

AVR32710

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

32094B–AVR32–05/09

AVR32710

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.

VL VL

HallA

HallB

HallC

BLDC

Hall Sensors

Vdc

0=++ cnbnan VVV

32094B–AVR32–05/09

AVR32710

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

32094B–AVR32–05/09

AVR32710

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)

V2V3

V5 V6

smseVV =

1Vd x

2Vd y

⎥

⎦

⎤

⎢

⎣

⎡

⎥

⎦

⎤

⎢

⎣

⎡

−

⎥

⎦

⎤

⎢

⎣

⎡

)

cos()

cos(0

)

cos()

cos(1

⎥

⎦

⎤

⎢

⎣

⎡

⎥

⎦

⎤

⎢

⎣

⎡

−

−−

⎥

⎦

⎤

⎢

⎣

⎡

32094B–AVR32–05/09

AVR32710

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 +==

max

)2()sin(

)1()

sin(

−

Ftick

nresolution ××

)(

⎥

⎦

⎤

⎢

⎣

⎡

resolution

Ftick

32094B–AVR32–05/09

AVR32710

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.

32094B–AVR32–05/09

AVR32710

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(

)

sin(

−

2*T

dx dy t0t0

PWM2

PWM1

PWM0

32094B–AVR32–05/09

AVR32710

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

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)

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

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

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

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

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

(

)

axb

TTT

TdT

ddT

−=

−

0π

---[,]

---2π

------[, ]

2π

------ π[,]

π4π

------[, ]

4π

------ 5π

------[,]

5π

------ 2π[,]

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