UNIVERSITY OF NAIROBI

SCHOOL OF ENGINEERING

DEPT. OF ELECTRICAL AND INFORMATION

ENGINEERING

PROJECT REPORT

SPEED CONTROL OF A PERMANENT MAGNET

DC MOTOR USING DSP

PRJ 147

NAME: Kihika Lazarus Waweru

ADM NO: F17/1435/2011

PROJECT SUPERVISOR: MR. AHMED SAYYID

EXAMINER: DR. KAMUCHA

A Project Submitted in Partial Fulfillment of the Requirements for the

Award of the Degree in B.Sc. Electrical and Electronics Engineering

Submitted on: 13th May, 2016

i

Table of Contents Declaration of Originality ............................................................................................................... iii

Dedication ....................................................................................................................................... iv

Acknowledgement ............................................................................................................................ iv

List of Figures ..................................................................................................................................v

List of Tables ................................................................................................................................... vi

List of Abbreviations ....................................................................................................................... vi

Abstract .......................................................................................................................................... vii

CHAPTER ONE: INTRODUCTION ......................................................................................... 1

1.1 Problem Statement ...................................................................................................................1

1.2 Project Objectives .....................................................................................................................1

1.3 Project Scope ............................................................................................................................1

1.4 Project Organization ..................................................................................................................1

CHAPTER TWO: LITERATURE REVIEW ............................................................................ 2

2.10 DC MOTORS ............................................................................................................................2

2.11 PRINCIPLE OF OPERATION OF A PERMANENT MAGNET DC MOTOR ........................................2

2.12 SPEED OF A DC MOTOR ........................................................................................................3

2.13 SPEED CONTROL OF DC MOTOR USING DSP...........................................................................5

2.14 EQUIVALENT CIRCUIT OF A DC MOTOR..................................................................................5

2.15 FOUR QUADRANT OPERATION OF A DC MOTOR ....................................................................6

2.16 ADJUSTABLE SPEED DRIVES ..................................................................................................8

2.17 CONTROL OF ADJUSTABLE SPEED DRIVES ..............................................................................9

2.17 THE TRANSFER FUNCTION OF A PERMANENT MAGNET DC MOTOR ........................................9

2.2 DC – DC CONVERTERS .............................................................................................................. 10

2.21 THE BUCK CONVERTER ....................................................................................................... 11

2.22 CONTINUOUS CONDUCTION MODE .................................................................................... 13

2.3 PULSE WIDTH MODULATION (PWM) ........................................................................................ 14

2.4 DIGITAL SIGNAL PROCESSOR (DSP) ........................................................................................... 16

CHAPTER THREE: DESIGN ................................................................................................... 17

3.1 SPEED DRIVE REQUIREMENTS .................................................................................................. 17

3.2 DIGITAL SIGNAL PROCESSOR .................................................................................................... 17

ii

3.3 PERMANENT MAGNET DC MOTOR ........................................................................................... 20

3.4 MOSFET SWITCH ..................................................................................................................... 20

3.5 GATE DRIVE DESIGN ................................................................................................................ 21

3.6 COMPENSATOR DESIGN........................................................................................................... 22

CHAPTER THREE: SIMULATION ........................................................................................ 26

4.1 OPEN LOOP SIMUL ATION ........................................................................................................ 26

4.2 CLOSED LOOP SIMULATION ..................................................................................................... 26

CHAPTER FIVE: RESULTS & ANALYSIS ........................................................................... 28

5.1: DC MOTOR PRACTICAL RESULTS.............................................................................................. 28

5.2: OPEN LOOP SIMULATION RESULTS .......................................................................................... 29

5.3: CLOSED LOOP SIMULATION RESULTS ....................................................................................... 30

5.4: GATE DRIVE CIRCUIT RESULTS ................................................................................................. 30

CHAPTER SIX: CONCLUSION & RECOMMENDATION ................................................ 31

6.1: CONCLUSIONS........................................................................................................................ 31

6.2: DIFFICULTIES EXPERIENCED..................................................................................................... 31

6.3: RECOMMENDATION ............................................................................................................... 31

REFERENCES ................................................................................................................................... I

APPENDIX ..................................................................................................................................... II

iii

Declaration of Originality Name of Student:

Kihika Lazarus Waweru

Registration Number:

F17/1435/2011

College:

Architecture and Engineering

Faculty/School:

Engineering

Department:

Electrical and Information

Course Name:

Electrical and Electronics

Title of Work:

Speed Control of a Permanent DC Motor using DSP

1. I understand what plagiarism is and I am aware of the university policy in this regard.

2. I declare that this final year project report is my original work and has not been

submitted elsewhere for examination, award of a degree or publication. Where other

people’s work or my own work has been used, this has properly been acknowledged

and referenced in accordance with the University of Nairobi’s requirements.

3. I have not sought or used the services of any professional agencies to produce this work.

4. I have not allowed, and shall not allow anyone to copy my work with the intention of

passing it off as his/her own work.

5. I understand that any false claim in respect of this work shall result in disciplinary action,

in accordance with University anti-plagiarism policy.

SIGNATURE:

………………………………………………………………………………………

DATE: ………………………………………………………………

iv

Dedication I dedicate this project to my dear sister Carol and loving parents Paul and Muthoni Kihika for

their continued support throughout my course. I am forever indebted to you.

Acknowledgement Who can tell all the good things that the Lord has done? Who can praise Him enough? I

thank the Almighty God for His goodness and love. The far I have come and the far I am

to go, I praise Him.

I acknowledge my project supervisor Mr. Ahmed Sayyid. I would like to take this

opportunity to express my sincere gratitude to him for the support and guidance he has

provided during the entire period I have been working on the project. I am grateful for

the patience and zeal he has shown. I am highly indebted to him for giving me a better

understanding of the subject and valuable inputs.

I am grateful to Prof. Ouma A. H., the Chairman to the Department of Electrical and

Information Engineering, University of Nairobi for allowing me access to the

department’s equipment and for enabling me get the necessary components for the

completion of this project.

I would like to thank the Department laboratory assistants particularly Mr. Ng’ang’a and

Mr. Kimani in the Machines and Measurements lab respectively. Their support and

assistance throughout the time I’ve been doing tests for my project are highly

appreciated.

I would like to thank my friends for their support and criticism during my project period.

They have been my consistent anchors during this project.

Lastly, I would like to thank my parents and family members for their support and

encouragement as I carried out the project. They have been there for me and have always

been proud of me.

May the Almighty God bless, reward and be with you all.

v

List of Figures Fig 2.11: Principle of Operation of Permanent Magnet dc motor ……………………………pg 3

Fig 2.12: Dc motor Equivalent Circuit ………………………………………………………pg 6

Fig 2.13: Four Quadrant Operation of Dc motor …………………………………………….pg 7

Fig 2.14: Two Quadrant Converter ……………………….………………………………….pg 8

Fig 2.15: Single Quadrant Converter ………………………………………………………...pg 8

Fig 2.16: Closed loop Operation of Dc motor ……………………………………………….pg 9

Fig 2.17: Dc motor Transfer Function blocks ……………………………………………….pg 10

Fig 2.21: Dc – Dc Regulation Functional blocks ……………………………………………pg 11

Fig 2.22: Basic Dc – Dc Converter ……………………………………………………….....pg 11

Fig 2.23: Basic dc Converter Output ………………………………………………………..pg 12

Fig 2.24: Practical Dc – Dc Converter Circuit ……………………………………………....pg 13

Fig 2.25: Continuous Conduction Mode …………………………………………………….pg 14

Fig 2.31: Pulse Width Modulation signal Waveform ……………………………………….pg 15

Fig 2.32: 25% PWM signal Waveform ……………………………………………………...pg 15

Fig 3.11: Dc motor Speed control using DSP Flowchart ……………………………………pg 17

Fig 3.21: C2000 Piccolo Launchpad TMS320FX28027 ……………………………………pg 20

Fig 3.51: Schematic PCB for Gate Drive Circuit …………………………………………...pg 21

Fig 3.52: Express PCB Diagram for Gate Drive Circuit ……………………………………pg 22

Fig 3.61: Bode plot for Uncompensated motor System .........................................................pg 24

Fig 3.62: Step Response for Uncompensated motor System ……………………………….pg 24

Fig 3.63: Bode plot for the Compensated motor System …………………………………...pg 25

Fig 3.64: Step Response for the Compensated motor System ……………………………...pg 25

Fig 4.11: PSIM Open loop motor Simulation Circuit ……………………………………....pg 26

Fig 4.21: PSIM Closed loop motor Simulation Circuit …………………………………….pg 27

Fig 5.11: Tach-generator Output voltage against Speed graph …………………………….pg 29

Fig 5.41: Auto-coupler Gate Drive input and output waveforms ……………….………….pg 30

vi

List of Tables Table 5.11: Dc Motor Practical Results ……………………..…………….pg 28

Table 5.21: Dc Motor Open Loop Simulation Results …………………….pg 29

Table 5.31: Dc Motor Closed Loop Simulation Results …………………...pg 30

List of Abbreviations DSP Digital Signal Processing

DC Direct Current

AC Alternating Current

PWM Pulse Width Modulation

RPM Revolutions per minute

KVL Kirchoff’s Voltage Law

KCL Kirchorff’s Current Law

ADC Analogue to Digital Converter

GPIO General Purpose Input/Output

vii

Abstract Many industrial applications in the modern world such as conveyor belts, automobiles,

elevators, steel rolling mills, cranes, high precision digital tools, air conditioners and

robotics all involve rotation of dc motors at different speeds. Their simple nature,

precision and wide range speed control characteristics of dc motors make them most

suited in many applications. The subject of speed control in dc motors is hence very

critical for control engineers.

This project is about controlling the speed of a permanent magnet dc motor. A DSP is

used as the digital controller in this case. It generates PWM signals that correspond to the

desired speed. The PWM signals are then used to switch ON and OFF a MOSFET switch

hence controlling the power fed to the motor thus the speed. A closed loop system is to

be built by obtaining the output speed using a tacho-generator as the feedback. A closed

loop transfer function is also obtained for the system.

Simulation is done in both the open loop and closed loop system. Results of the simulations and

the practical results are obtained and compared and analyze

1

CHAPTER ONE: INTRODUCTION 1.1 Problem Statement

Speed control of DC motors is an inevitable topic in millions of industrial of applications. This

project is concerned with application of digital signal processing methods in realizing the speed

control of permanent magnet dc motors.

1.2 Project Objectives

Design of DC-DC converters

Modelling, simulating and construction of the dc motor control system

1.3 Project Scope

Demonstration of speed control of permanent magnet dc motor using a digital signal processor.

1.4 Project Organization Chapter one gives an introduction to the project; stating the project statement, objectives

and scope.

Chapter two gives the literature review of dc motors, dc-dc converters and digital signal

processors.

Chapter three gives the design analysis; looking into the speed drives, permanent magnet

dc motor speed requirements and analysis. The MOSFET switch is also investigated as

well as the gate drive circuit between the MOSFET and the DSP. The chapter is

concluded by the design of the motor controller compensator.

Chapter four gives the simulation of both open and closed loop simulations of the motor

speed control system in PSIM.

Chapter five presents the results for the open and closed loop simulations as well as for

motor practical results.

Chapter six represents a summary of the entire project, gives the conclusion and

recommendations on the same.

2

CHAPTER TWO: LITERATURE REVIEW

2.10 DC MOTORS

DC motors are devices that convert dc electrical energy to mechanical energy. A motor

works on the principle that a current-carrying conductor placed in a magnetic field experiences a

force. This force is due to the interaction between magnetic field due to the current carrying

conductor and the magnetic field that existed. A motor can derive its electrical energy from

either a dc source or from an AC source. They can therefore be referred to as either dc motors or

ac motors. The magnetic field of the motors can be derived from either a permanent magnet or

from an electromagnet.

The three basic types of DC motors are the series motor, the shunt motor, and the

compound motor.

The series motor is designed to move large loads with high starting torque in

applications such as a crane motor or lift hoist.

The shunt motor is designed slightly differently, since it is made for applications

such as pumping fluids, where constant-speed characteristics are important.

The compound motor is designed with some of the series motor's characteristics

and some of the shunt motor's characteristics. This allows the compound motor to

be used in applications where high starting torque and controlled operating speed

are both required.

2.11 PRINCIPLE OF OPERATION OF A PERMANENT MAGNET DC MOTOR A rectangular coil free to rotate about a fixed axis is placed inside a magnetic field produced by a

permanent magnet as shown in figure 1.10 below. A dc current is fed into the coil through

carbon brushes bearing on a commutator, which consists of a metal ring split into two halves

separated by insulation. As current flows through the coil a magnetic field is set up around the

coil which interacts with the magnetic field due to the permanent magnet. This causes a force F

to be exerted on the conductor, whose direction can be determined by the Fleming’s Left hand

rule. This causes a torque and the coil rotates. When the coil has rotated through 900 the negative

and positive terminals of the supply interchange the commutator halves thus, reversing the

current direction. This prevents the coil from rotating in the opposite direction, thus it rotates

continuously in one direction.

3

Fig. 2.11

2.12 SPEED OF A DC MOTOR BACK EMF, Eb.

When the armature of a dc motor rotates under the influence of the driving torque, the

armature conductor moves through the magnetic field due to the permanent magnet, thus an emf

is induced in them as in a generator. The induced emf acts in opposite direction to the direction

of the applied voltage, Vt (Lenz’s Law). The induced emf is known as back emf or counter emf,

Eb. The back emf is given by;

Eb = 𝑃∅𝑍𝑁

60𝐴 (Eqn 2.10).

Where,

P= Number of poles of the permanent magnet,

∅= Flux per pole in Wb,

Z= total number of armature conductors,

N= speed of the motor in rpm

A= number of parallel paths;

(A=2 for simplex wave winding, A=P for simplex lap winding)

The back emf is always smaller than the applied voltage, although the difference is small

when the motor is running under normal conditions.

From the motor equation given by;

Vt = Eb + IaRa (Eqn 2.11).

4

Then the net voltage across the armature circuit is,

Va = Vt − Eb (Eqn 2.12).

And the back emf will be given by;

Eb = Vt − IaRa (Eqn 2.13).

Since Vt and Ra are usually fixed, the value of Eb determines the current Ia drawn by the motor. If

the speed N of the motor is high, then Eb is large from Eqn 2.1 hence the motor draws less

armature current and vice versa.

Thus, from Eqn 1.11 and 1.13 we obtain

𝑃∅𝑍𝑁

60𝐴= 𝑉𝑡 – 𝐼𝑎𝑅𝑎 (Eqn 2.14)

N = (Vt – IaRa) 60A

∅PZ (Eqn 2.15)

N = K (Vt – IaRa)

∅ (Eqn 2.16)

Where

K = 60A

PZ

Armature torque is given by;

𝑇 =𝑍∅𝐼𝑎𝑃

2𝜋𝐴=

𝐼𝑎𝐸𝑏

𝜔𝑎 (Eqn 2.18)

Where 𝜔a = 2𝜋N is the angular velocity of the motor shaft

There are three main methods of controlling the speed of a dc motor, namely:

i. By varying the flux per pole (∅). This is called flux control method.

ii. By varying the resistance in the armature circuit. This is called armature control method

iii. By varying the applied voltage. This is called voltage control method.

But the above methods suffer from several disadvantages, which include:

Low efficiency at low speeds and hence low charge cycle for the battery.

5

Speed can be controlled only below base speed.

Battery voltage variations cannot be compensated.

Limited to brushed DC motors only.

2.13 SPEED CONTROL OF DC MOTOR USING DSP Digital Signal processing technology is enabling cost effective and energy efficient

control system design. The performance of a DSP architecture allows an intelligent approach to

reduce the complete system costs. PWM switching control methods improve speed control and

reduce the power losses in the system, which increases the mean time between charge cycles of

the battery. The reduced losses also help to reduce the weight of the system. In PWM control

methods, appropriate circuit and control methods allow speeds above base speed to be achieved.

Moreover using gate drive IC’s improve the ruggedness and reliability of the system.

2.14 EQUIVALENT CIRCUIT OF A DC MOTOR In a dc motor, the field flux ∅f is established by the stator, either by means of a

permanent magnet where the field flux ∅f remains constant or by means of a field winding where

the field current If controls the flux ∅f. The rotor carries in its slots the armature winding, which

handles the electrical power. The interaction of the field flux ∅f and the armature current Ia

produces the electromagnetic torque;

Tem = kt∅fIa (Eqn 2.20)

Where kt is the torque constant of the motor.

A back emf is produced in the armature circuit by the rotation of the armature conductors of a

speed 𝜔m in the presence of a field flux ∅f:

ea = ke∅f𝜔m

where ke is the voltage constant of the dc motor.

The interaction between Tem with the load torque determines how the motor speed builds up.

𝑇𝑒𝑚 = 𝐽𝑑𝜔𝑚

𝑑𝑡 + 𝐵ωm + Tωl(t) (Eqn 2.21)

6

Where J and B are the total equivalent inertia and the damping respectively, of the motor-load

combination and T𝜔L is the equivalent working torque of the load.

Fig 2.12

A controllable voltage source Vt is applied to the armature terminals to establish Ia. Thus

the armature current is determined by Vt, the induced emf ea, the armature resistance Ra, and the

armature winding inductance La.

Vt = ea + RaIa + La𝑑𝐼𝑎

𝑑𝑡 (Eqn 2.23)

2.15 FOUR QUADRANT OPERATION OF A DC MOTOR DC machines act as generators while braking. To consider braking, it’s assumed that the

flux ∅f is kept constant and the motor is initially driving a load at speed 𝜔m. To reduce speed,

the armature voltage Vt is reduced below ea so that the armature current Ia reverses in direction.

The electromagnetic torque Tem reverses in direction and the kinetic energy associated with the

motor load inertia is converted into electrical energy by the dc machine. This energy must

somehow be absorbed by the source Vt or be dissipated by a resistor.

7

During braking operation, the polarity of ea does not change since the direction of

rotation has not changed. As the rotor slows down, ea decreases in magnitude. The generation

stops when the rotor comes to a standstill and all the inertial energy has been exhausted. The

direction of rotation of the motor is reversed by reversing the polarity of the terminal voltage Vt.

A dc motor can therefore operate in either direction and its electromagnetic torque can be

reversed for braking, as shown by the four quadrants of the torque-speed plane in figure below.

Fig 2.13

In permanent magnet dc motors, permanent magnets on the stator produce a constant field flux

∅f and thus we have;

Tem = kTIa (Eqn 2.30)

Ea = kE𝜔m (Eqn 2.31)

Vt = Ea + RaIa (Eqn 2.32)

The steady state speed can thus be obtained as a function of Tem for a given value of Vt.

𝜔m = 1

kE(𝑉𝑡 −

Ra

kT 𝑇𝑒𝑚) (Eqn 2.33)

8

The speed of a load with an arbitrary torque-speed characteristics can hence be controlled by

controlling Vt in a permanent magnet dc motor.

2.16 ADJUSTABLE SPEED DRIVES A switch mode dc-dc converter can be used to control the speed of a dc motor. Figure 2.14 is a

two quadrant converter which can be used when reversing the direction of the motor rotation is

not needed but braking is required.

Fig 2.14

For a single quadrant operation where speed is to remain unidirectional and there is no need for

braking, the step down converter of figure 2.15 can be used.

Fig 2.15

9

2.17 CONTROL OF ADJUSTABLE SPEED DRIVES Figure 2.16 shows a block diagram of a dc motor operating in closed loop to deliver

controlled speed. The speed transducer converts the mechanical energy (speed) into an electrical

signal. The electrical signal is fed to the controller as a feedback. The controller compares the

feedback signal to the reference signal (speed) and produces a PWM signal of appropriate duty

cycle. The PWM signal is used to control the switch of the power electronics converter. This

controls the terminal voltage Vt and hence, the speed.

Ref speed

Fig 2.16

2.17 THE TRANSFER FUNCTION OF A PERMANENT MAGNET DC MOTOR

The following equations written in terms of small deviations around their steady

state values are used for analyzing small signal performance of the motor-load

combination around a steady state operating point.

Δvt = Δea + RaΔia

Δea = kE Δ𝜔m

ΔTem = kT Δia

ΔTem = ΔTWL

Taking the Laplace transforms of these equations;

Vt(s) = Ea(s) + (Ra + sLa) Ia(s)

Ea(s) = kE𝜔m(s)

Tem(s) = kTIa(s)

Tem(s) = TWL(S) + (B + sJ) 𝜔m(s)

Speed

Controler

Power

Electronics

motor drive

Motor Load

Speed

Transducer Motor speed (Voltage signal)

10

𝜔m(s) = sθm(s)

These equations for the motor-load combination can be represented by the transfer function

blocks as shown in figure 2.7.

Fig 2.17

The inputs to the motor-load combination in the figure are the armature voltage Vt(s) and

the load torque TWL(s). Applying one input at a time and setting the other input to zero,

the superposition principle yields;

This equation results in two closed loop transfer functions:

G1(s)

with Twl(s) = 0 and

G2(s)

with Vt(s) = 0

2.2 DC – DC CONVERTERS DC-DC converters are used to convert unregulated dc input voltage to a controlled dc output

voltage at a desired level.

The unregulated dc input voltage can be obtained by rectifying the line voltage or from a dc

source such as a battery, as shown in figure 2.70.

11

Fig 2.21

AC line voltage

1-phase or 3-phase

There are several types of dc-dc converters. The following are some of the types of dc-dc

converters that exist:

i. Step-down (buck) converter

ii. Step-up (boost) converter

iii. Step-down/step-up converter (buck-boost) converter

iv. Buck converter

v. Full bridge converter

In this project the buck converter is discussed and used.

2.21 THE BUCK CONVERTER The average dc output voltage of a dc-dc converter is controlled to equal a desired level,

even though the input dc voltage and the output load may fluctuate. The average output voltage

is controlled by controlling the switch “on” and “off” durations (ton and toff). Figure 2.8

illustrates a basic dc-dc converter.

Fig 2.22

12

The average value Vo of the output voltage vo depends on ton and toff as shown in figure 2.71

below.

Fig 2.23

The output voltage is controlled by switching at a constant frequency (and hence a constant

switching time period Ts = ton + toff). The duty ratio, D is defined as the ratio of the on duration

to the switching time period. Adjusting the on duration therefore, varies the duty ratio, D.

𝐷 = 𝑡𝑜𝑛

𝑇𝑠 (Eqn 2.70)

The basic circuit of figure 2.70 constitutes a buck converter for purely resistive load. Assuming

an ideal switch, a constant instantaneous input voltage Vd and a purely resistive load, the

instantaneous output voltage waveform is shown in figure 2.71 as a function of the switch

position. The average output voltage can be calculated in terms of the switch duty ratio, D:

(Eqn 2.71)

= 𝑡𝑜𝑛

𝑇𝑠Vd (Eqn 2.72)

= DVd (Eqn 2.73)

Varying the duty ratio, D thus, controls the output voltage Vo.

The circuit of figure 2.70 above has two drawbacks:

i. In practice, the load would be inductive and even with resistive loads there would

always be stray inductance. The switch will thus absorb (or dissipate) the inductive

energy and may be destroyed.

13

ii. The output voltage fluctuates between Vd and zero, which is not acceptable for most

applications.

The circuit of figure 2.24 below is used to overcome these drawbacks.

Fig 2.24

The problem of stored inductive energy is overcome by using a diode as shown in the

figure above. A low pass filter consisting of an inductor and a capacitor is used to diminish the

output voltage fluctuations. The corner frequency of the low pass filter is chosen to much lower

than the switching frequency fs, thus eliminating the switching ripple in the output voltage.

When the switch is on, the diode becomes reversed biased and input provides energy to the load

and the inductor. When the switch is off the inductor current flows through the diode,

transferring some of its stored energy to the load. The average inductor current is equal to the

average output current Io, since the average capacitor current in steady state is zero.

2.22 CONTINUOUS CONDUCTION MODE In continuous conduction of operation, the inductor current flows continuously and does

not fall to zero. The figure below shows the waveforms of continuous conduction mode.

When the switch is on, it conducts the inductor current and the diode becomes reverse biased.

This results in a positive voltage VL = Vd + Vo, across the inductor. This voltage causes linear

increase in inductor current IL. When the switch is turned off, the inductive energy causes IL to

continue flowing. The current now flows through the diode and Vo = -VL.

14

Fig 2.25

Since in steady state operation the waveform must repeat from one time period to the next;

(Eqn 2.74)

Therefore;

(𝑉𝑑 − 𝑉𝑜)𝑡𝑜𝑛 = (𝑇𝑠 − 𝑡𝑜𝑛) (Eqn 2.75)

Or,

(Eqn 2.76)

The output voltage is thus proportional to the value of the duty cycle, D as shown in the equation

above. In discontinuous conduction mode the inductor current goes to zero during the period

when the switch is off and it does not flow until when the switch is turned on again.

2.3 PULSE WIDTH MODULATION (PWM) A Pulse refers to an electromagnetic wave or modulation thereof of brief duration while

Width Modulation is to adjust to proper measure or proportion the width of the pulse with

respect to the frequency of the wave. Pulse Width Modulation (PWM) is therefore a way of

delivering energy through a succession of pulses rather than a continuously varying analog

signal. We consider the waveform in the figure below;

15

Fig 2.31

The signal is a voltage switching between 12V and 0V. A device connected to use the signal will

see the average voltage. Since the time the signal is 12V is equal to the time the signal is 0V in

the figure shown above, an average voltage of 6V will be seen by the device. The positive pulse

lasts for 50% of the total time.

In the figure 1.92 below, the positive pulse only lasts for 25% of the total time. The average

voltage seen by the device in this case is 3V, that is, less than in the first case. The voltage is

equivalent to the product of the positive pulse value and 25%.

Fig 2.32

Varying the time of the positive pulse thus varies the average output voltage. The percentage of

the time of positive pulse compared to the period of the signal is called the duty cycle, D of the

signal. In the figures above the duty cycle, D was therefore, 50% and 25% respectively.

PWM signals have the advantage of high efficiency compared to other signals. They

however, cannot be used by some devices due to their abrupt and periodic changes in magnitude.

Several circuits can be used to generate PWM signals. A digital signal processor (DSP) is

normally programmed to produce PWM signals.

16

APPLICATIONS OF THE PWM

A suitable device has to be used to see the average output voltage, since some devices

don’t work properly with abrupt changing voltages. Pulse width modulated signals are used to

control the speed of a motor, as control voltages for switches, hence greatly used in power

electronics converters among others.

2.4 DIGITAL SIGNAL PROCESSOR (DSP) A digital signal processor (DSP) is a specialized microprocessor, with its architecture

optimized for the operational needs of digital signal processing. The goal of DSPs is usually to

measure, filter and/or compress continuous real-world analog signals. Most general-purpose

microprocessors can also execute digital signal processing algorithms successfully, but dedicated

DSPs usually have better power efficiency. Thus, they are more suitable in portable devices such

as mobile phones because of power consumption constraints. DSPs often use special memory

architectures that are able to fetch multiple data and/or instructions at the same time.

Digital Signal Processing both provides a mathematical description of the systems to be

designed and also implements them (either by software programming or by hardware

embedding) without much dependency on hardware issues, which explains the importance and

success of DSP engineering.

DSP processor ICs are found in every type of modern electronic systems and products

including, SDTV | HDTV sets, radios and mobile communication devices, Hi-Fi audio

equipment, Dolby noise reduction algorithms, GSM mobile phones, mp3 multimedia players,

camcorders and digital cameras, automobile control systems, noise cancelling headphones,

digital spectrum analyzers, intelligent missile guidance, radar, GPS based cruise control systems

and all kinds of image processing, video processing, audio processing and speech processing

systems.

The DSPs have the following advantages when used as controllers over the other

controllers:

Low cost

High performance

Flexibility of quick design modifications

Implementation of more control schemes

Less susceptible to aging, environmental variations & have better noise immunity.

17

CHAPTER THREE: DESIGN

This project requires that the speed of a permanent magnet dc motor is digitally controlled using

a DSP microcontroller. A feedback system for the speed control system is to be provided. A

tacho-generator is to be used as a device that converts the output speed to a voltage signal that is

fed back to the DSP to make a closed loop control system.

3.1 SPEED DRIVE REQUIREMENTS Different components are used in the design of the speed control system. These include a

permanent magnet dc motor, a tacho-generator, DSP, MOSFET switch and its gate drive. The

flow chart of figure 3.11 below shows how the different components interoperated to complete

the project:

Fig 3.11

3.2 DIGITAL SIGNAL PROCESSOR A DSP is used as the digital controller in this project. The controller is to be designed in

analog using MATLAB and implemented using a DSP.

The DSP used is a TMS320F28027 from Texas Instruments. This is a member of the F2802x

Piccolo family of microcontrollers. This family of microcontrollers provides the power of the

18

C28x core coupled with highly integrated control peripherals in low pin-count devices. Features

of the TMS320F28027 are:

High-Efficiency 32-Bit CPU (TMS320C28x)

60 MHz (16.67-ns Cycle Time)

50 MHz (20-ns Cycle Time)

40 MHz (25-ns Cycle Time)

16 x 16 and 32 x 32 MAC Operations

16 x 16 Dual MAC

Harvard Bus Architecture

Atomic Operations

Fast Interrupt Response and Processing

Unified Memory Programming Model

Code-Efficient (in C/C++ and Assembly)

Endianness: Little Endian

Low Cost for Both Device and System:

Single 3.3-V Supply

No Power Sequencing Requirement

Integrated Power-on and Brown-out Resets

Small Packaging, as Low as 38-Pin Available

Low Power

No Analog Support Pins

Clocking:

Two Internal Zero-pin Oscillators

On-Chip Crystal Oscillator/External Clock Input

Dynamic PLL Ratio Changes Supported

Watchdog Timer Module

Missing Clock Detection Circuitry

Up to 22 Individually Programmable, Multiplexed GPIO Pins With Input Filtering

Peripheral Interrupt Expansion (PIE) Block That Supports All Peripheral Interrupts

Three 32-Bit CPU Timers

Independent 16-Bit Timer in Each ePWM Module

19

On-Chip Memory

Flash, SARAM, OTP, Boot ROM Available

Code-Security Module

128-Bit Security Key/Lock

Protects Secure Memory Blocks

Prevents Firmware Reverse Engineering

Serial Port Peripherals

One SCI (UART) Module

One SPI Module

One Inter-Integrated-Circuit (I2C) Bus

Enhanced Control Peripherals

Enhanced Pulse Width Modulator (ePWM)

High-Resolution PWM (HRPWM) Module

Enhanced Capture (eCAP) Module

Analog-to-Digital Converter (ADC)

On-Chip Temperature Sensor

Comparator

Advanced Emulation Features

Analysis and Breakpoint Functions

Real-Time Debug via Hardware

2802x, 2802xx Packages

38-Pin DA Thin Shrink Small-Outline Package (TSSOP)

48-Pin PT Low-Profile Quad Flatpack (LQFP)

The program used was designed on Code Composer Studio IDE and Control Suit both from

the Texas Instruments, which are compatible with the DSP. The figure 2.2 below shows a

photo of the TMS320F28027 C2000 Launchpad.

20

Fig 3.21

3.3 PERMANENT MAGNET DC MOTOR A 220V dc motor was used but operated at a maximum of 120V. The armature resistance was

calculated as the gradient of the graph of armature voltage against armature current. Different

values of armature current were recorded at different armature voltages as shown in table 1. A

graph of Armature voltage against Armature current was then drawn.

3.4 MOSFET SWITCH A MOSFET was used as the switch to the buck converter. The MOSFET used is to be controlled

by the PWM signals from the digital controller-the DSP. The MOSFET does not see the average

voltage of the PWM signal, but it sees HIGH voltages followed by LOW voltages repeatedly just

like the PWM signal appears, and at the same frequency as the frequency of the signal.

The MOSFET switches ON when a HIGH voltage is applied to its gate and OFF when a LOW

voltage is applied to gate. It therefore, switches ON and OFF at the frequency of the PWM

signal.

The MOSFET used had the following properties: 500V and 10A

21

3.5 GATE DRIVE DESIGN The switching time of a transistor needs to be kept as short as possible, to minimize

power losses. However, the switching time is inversely proportional to the amount of current

used to charge the gate. Switching currents are therefore required in terms of several hundreds of

mA or even Amperes.

The switching signal, which is a PWM signal, for the transistor is generated by a DSP. The DSP

provides an output signal that is limited to a few mA of current. Consequently, if the transistor is

directly driven by such a signal, it would switch very slowly, with correspondingly high power

loss. The gate capacitor of the transistor will draw current so quickly, during switching, that it

causes a current overdraw in the DSP, causing overheating which may lead to permanent

damage or even completely destroy DSP. A gate driver is thus provided between the DSP output

signal and the power transistor to prevent this from happening.

The gate drive circuit was realized using an isolated auto-coupler IC HCPL3120 shown

in PCB schematic figure 3.51 below. CN1 is the connector where the PWM signal from the DSP

is fed to the gate drive. CN2 is the connector to which power supply to the motor was fed, this is

the voltage being controlled in order to control the motor speed. Terminal 1 of CN3 was

connected to the gate of the MOSFET while terminal 2 to the source.

To determine the value of R1, the IF of the auto-coupler must be considered. Then R1 is

given by:

Since 7mA < IF < 16mA for HCPL3120

we select IF = 10mA

R1 = Vcc−1.4

I =

5−1.4

10𝑚𝐴 = 360Ω

Fig 3.51

22

Figure 3.52 is the PCB express drawing of the gate drive circuit that was printed, etched and

solder. The output of the gate drive was recorded as shown in the results section 5.4.

Fig 3.52

3.6 COMPENSATOR DESIGN The compensator is designed in frequency domain as follows:

The motor transfer function is given by:

G1(s) = 𝜔

Where KE = 𝐴𝑟𝑚𝑎𝑡𝑢𝑟𝑒 𝑣𝑜𝑙𝑡𝑎𝑔𝑒

𝑆𝑝𝑒𝑒𝑑 𝑖𝑛 𝑅𝑃𝑀

and KT = 𝑇𝑜𝑟𝑞𝑢𝑒

𝑐𝑢𝑟𝑟𝑒𝑛𝑡 =

𝜏

𝜔𝑖

but 𝜏 = 𝑃𝑜𝑤𝑒𝑟

𝜔 =

𝑣𝑖

𝜔

hence KT = 𝑣𝑖

𝜔𝑖 =

𝑣

𝜔

A graph of Armature voltage against speed in RPM was drawn from the values of table 5.11 and

its gradient calculated. This value is equal to Ktach which represents the voltage output of the

tacho-generator for every revolution.

23

Ktach = 0.0194 V/rad/s

KT = 0.84302 V/rad/s

The motor inertia moment is provided in the datasheet and is given as;

J = 0.04 kgm3

B = 0.0019 N/rad/s

The values of Ra and La for the motor were determined by measurement.

Ra = 2.27 Ω

La = 0.018 H

The damping coefficient is so small and can be assumed negligible in the calculations. Hence,

the motor speed transfer equation G1(s) becomes:

G1(s) = 𝜔 = 0.84302

(0.04𝑠+0.0019)(0.018𝑠+2.27)+0.84302𝑥0.84302

= 0.84302

0.00072𝑠∗2+0.09114𝑠+0.71068

= 1170.86

𝑠∗2+126.58𝑠+987.55

= 51.56 5.109

𝑠∗2+1025𝑠+5.109

This transfer function was used to design the compensator in MATLAB as follows:

A new m-file was created and the following code written;

%Practical Motor System Equation

num = [1170.86] denom = [1 126.58 987.55]

Gp = tf(num, denom) bode (Gp) grid on title ('Step Response for Compensated motor') hold on

The bode plot and step response obtained for the uncompensated motor system is shown in the

figure below.

24

Fig 3.61

Fig 3.62

From the bode plot and step response for the motor, it was notes to have a phase margin of 91.10

and a long settling time of approximately 800s. To improve the phase margin and response for

the motor, a compensator was designed.

A PD controller with Kp = 100 and Kd = 5 was noted to improve the motor characteristics to give

a faster time response and a lower phase margin. The bode plot and step response of the

compensated system are shown below.

25

Fig 3.63

Fig 3.64

Below is the code added to the previous in order generate the above bode plot for the

compensated system.

%Compensted System

Kp = 100 Ki = 0 Kd = 5

Gc = pid(Kp, Ki, Kd) H = 1 Mc = feedback(Gp*Gc, H) bode (Mc) grid on

26

CHAPTER THREE: SIMULATION Simulation of the various circuits was done using the PowerSim software as follows in this

chapter sections.

4.1 OPEN LOOP SIMUL ATION The aim of this simulation was to obtain different values of speed at different duty cycles

hence armature voltages. The circuit was connected to match the speed of the practical motor

used at different armature voltages. The speed of the motor was recorded against various duty

cycles of the square wave voltage source driving the MOSFET as shown in table 5.21.

The circuit for the open loop simulation was as shown below:

Fig 4.11

4.2 CLOSED LOOP SIMULATION A feedback system was incorporated with the proportional compensator designed to form

a closed loop system. The compensator replaced the PWM producer in the open loop circuit.

The aim of this simulation was to get different values of speed using different values of the

reference voltage. A voltage of 2.4V was used as the maximum reference voltage and it was

reduced using a voltage divider to give different values for the reference voltage. The speed of

the motor was recorded against various positions of the rheostat. These positions represents the

27

reference speeds input to system. The difference between the reference speed and the actual

speed gives an error signal to the controller that in turn regulates the duty cycle of the signal fed

to the MOSFET. This ensures that the actual speed of the motor follows the reference speed. The

figure below shows the circuit of the closed loop simulation and the results obtained were

recorded as shown in table 5.31.

Fig 4.21

28

CHAPTER FIVE: RESULTS & ANALYSIS

5.1: DC MOTOR PRACTICAL RESULTS To be able to determine the various motor constants required for its modelling in designing the

controller, an experiment was carried out on the motor. The table below shows the parameters

and values obtained. A graph of tachogenerator output voltage against motor speed was then

plotted as shown in fig 4.11 and it’s slope is numerically equal to Ktach = 0.0194.

Table 5.11

Va Ia Vtach N(rpm) 𝜔 = 2𝜋*(rpm)/60 Ktach = Vtach/𝜔 KT = Va/𝜔

15 0.1 0.29 143 14.97 0.01937 1.002

32 0.2 0.7 344 36.02 0.01943 0.8884

37 0.2 0.83 408 42.73 0.01942 0.8805

42 0.2 0.94 459 48.07 0.01955 0.8737

48 0.2 1.03 538 56.34 0.01828 0.8519

59 0.2 1.36 666 69.74 0.0195 0.8460

66 0.2 1.53 753 78.85 0.0194 0.8370

71 0.3 1.66 813 85.14 0.01949 0.8339

81 0.3 1.89 929 97.28 0.0194 0.8326

92 0.3 2.14 1055 110.48 0.01937 0.8327

97 0.3 2.27 1119 117.18 0.01937 0.8277

103 0.3 2.41 1188 124.41 0.01937 0.8279

107 0.3 2.5 1230 128.81 0.01941 0.8307

117 0.3 2.75 1352 141.58 0.01942 0.8264

122 0.3 2.88 1415 148.18 0.01944 0.8233

0.0194 0.84302

29

Fig 5.11

5.2: OPEN LOOP SIMULATION RESULTS The figure 4.11 was created in PSIM with motor characteristics of set to match those of

the practical motor, that is, Ra = 1.2Ω, La = 8.2x10-3H, Nrated = 1200rpm, Ia(rated) = 1.6A and

Va(rated) = 120V. For different duty cycles of the clock, the speed obtained was recorded as shown

in Table 4.21 below;

Table 5.21

Duty cycle Motor speed, N (rpm)

0.05 42

0.15 168

0.25 294

0.35 419

0.45 545

0.50 608

0.65 797

0.75 923

0.85 1049

0.95 1175

0

0.5

1

1.5

2

2.5

3

3.5

0 200 400 600 800 1000 1200 1400 1600

Vta

ch

speed

Graph of Output Voltage aginst Speed in rpm

30

5.3: CLOSED LOOP SIMULATION RESULTS Table 5.31

Rheostat position (Reference

speed)

Armature voltage, Va (V) Motor Speed, N (rpm)

0.1 18 172

0.2 26 228

0.3 35 343

0.4 44 478

0.5 57 596

0.6 63 702

0.7 71 887

0.8 85 950

0.9 98 1076

1.0 114 1194

5.4: GATE DRIVE CIRCUIT RESULTS The input and output of the auto-coupler gate drive circuit was viewed on the oscilloscope screen

and captured as shown in the figure 4.41 below.

Fig 5.41

31

CHAPTER SIX: CONCLUSION & RECOMMENDATION 6.1: CONCLUSIONS The importance of permanent magnet dc motor speed control cannot be overstated. This

project has shown that cheaper and simpler methods can be used to control the speed of a

permanent magnet dc motor efficiently and accurately.

In order for the digital control for the dc motor to be realized in this project, the motor

was first modelled. This involved obtaining its transfer function for the closed loop

system which helped determine the motor characteristics. A compensator that improves

the motor performance to the desired characteristics was then designed. The code was

then written for the DSP controller to effect the digital speed control for the permanent

magnet dc motor. The motor speed was converted to equivalent voltage value through a

tacho-generator. This voltage was fed back to the DSP through an ADC to provide a

feedback for the controller.

The DSP realizes this control through sending PWM signals to the gate of the MOSFET

that would in turn switch the power to the motor ON and OFF at high frequency. The

speed of the motor is hence directly related to the average power delivered to it through

the PWM signal which is dependent the duty cycle. The DSP output PWM signal is

limited to a few mA current. Consequently, if the transistor is directly driven by such a

signal, it would switch very slowly, with correspondingly high power loss. A gate driver

is thus provided between the DSP output signal and the power transistor to prevent this

from happening.

6.2: DIFFICULTIES EXPERIENCED The implementation of the closed loop for the motor was initially a challenge as well as

writing the code for the DSP.

6.3: RECOMMENDATION Designing and implementing the dc motor speed control drive in all the four

quadrants. This will be able to give rotation in either direction and provide

braking for the dc motor.

Using the microprocessor to detect and display the speed of the dc motor on a

screen

I

REFERENCES Power Electronics (Circuits, Devices and Applications), Muhammad H. Rashid

A. E. Fitzgerald, C. K. (2003). Electric Machinery. New York: McGraw-Hill.

Nice N. S. (1996). Control Systems Engineering. John Wiley & Sons Inc

Bishop, R. H. (n.d.). Mordern Control Systems Analysis. ADDISON WESLEY.

Analysis & Design of Analog Integrated Circuits 4ed -Grey, Hurst, Lewis, Meyer

Introduction to Microprocessors and Microcontrollers 2nd Ed.~tqw~_darksiderg

Ned Mohan, T. M. (2003). POWER ELECTRONICS. Jolm Wiley & Sons.

John Bird. (2003). Electrical and Electronic Principles and Technology. Newnes.

Robert W. Erickson. (2001). Fundanentals of Power Electronics. Kluwer Academic Publishers.

www.ti.com

http://www.Analogdevices.com

www.mathworks.com/controltutorials

II

APPENDIX

//----------------------------------------------------------------------------------

// FILE: ProjectName-Main.C

// Description: Sample Template file to edit

// The file drives duty on PWM1A using C28x

// These can be deleted and modifed by the user

// C28x ISR is triggered by the PWM 1 interrupt

// Version: 2.0

// Target: TMS320F2802x(PiccoloA),

// Copyright Texas Instruments © 2004-2010

// October 2010 - Sample template project with DPLib v3 (MB)

// PLEASE READ - Useful notes about this Project

// Although this project is made up of several files, the most important ones are:

// "ProjectName-Main.C" - this file

// - Application Initialization, Peripheral config,

// - Application management

// - Slower background code loops and Task scheduling

// "ProjectName-DevInit_F28xxx.C

// - Device Initialization, e.g. Clock, PLL, WD, GPIO mapping

// - Peripheral clock enables

// - DevInit file will differ per each F28xxx device series, e.g. F280x, F2833x,

// "ProjectName-DPL-ISR.asm

// - Assembly level library Macros and any cycle critical functions are found here

// "ProjectName-DPL-CLA.asm"

// - Init code for DPlib CLA Macros run by C28x

// - CLA Task code

// "ProjectName-Settings.h"

// - Global defines (settings) project selections are found here

III

// - This file is referenced by both C and ASM files.

// "ProjectName-CLAShared.h.h"

// - Variable defines and header includes that are shared b/w CLA and C28x

// Code is made up of sections, e.g. "FUNCTION PROTOTYPES", "VARIABLE

DECLARATIONS" ,..etc

// each section has FRAMEWORK and USER areas.

// FRAMEWORK areas provide useful ready made "infrastructure" code which for the most part

// does not need modification, e.g. Task scheduling, ISR call, GUI interface support,...etc

// USER areas have functional example code which can be modified by USER to fit their appl.

// Code can be compiled with various build options (Incremental Builds IBx), these

// options are selected in file "ProjectName-Settings.h". Note: "Rebuild All" compile

// tool bar button must be used if this file is modified.

//----------------------------------------------------------------------------------

#include "ProjectName-Settings.h"

#include "PeripheralHeaderIncludes.h"

#include "DSP2802x_EPWM_defines.h"

#include "DPlib.h"

#include "IQmathLib.h"

/ FUNCTION PROTOTYPES

// Add protoypes of functions being used in the project here

void DeviceInit(void);

#ifdef FLASH

void InitFlash();

#endif

void MemCopy();

//-------------------------------- DPLIB --------------------------------------------

void PWM_1ch_CNF(int16 n, int16 period, int16 mode, int16 phase);

IV

void ADC_SOC_CNF(int ChSel[], int Trigsel[], int ACQPS[], int IntChSel, int mode);

// -------------------------------- FRAMEWORK --------------------------------------

int16 VTimer0[4]; // Virtual Timers slaved off CPU Timer 0

int16 VTimer1[4]; // Virtual Timers slaved off CPU Timer 1

int16 VTimer2[4]; // Virtual Timers slaved off CPU Timer 2

// Used for running BackGround in flash, and ISR in RAM

extern Uint16 *RamfuncsLoadStart, *RamfuncsLoadEnd, *RamfuncsRunStart;

// Used for ADC Configuration

int ChSel[16] = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;

int TrigSel[16] = 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;

int ACQPS[16] = 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7;

// Used to indirectly access all EPWM modules

volatile struct EPWM_REGS *ePWM[] =

&EPwm1Regs, //intentional: (ePWM[0] not

used)

&EPwm1Regs,

&EPwm2Regs,

&EPwm3Regs,

&EPwm4Regs,

;

// Used to indirectly access all Comparator modules

volatile struct COMP_REGS *Comp[] =

&Comp1Regs, //intentional: (Comp[0] not

used)

&Comp1Regs,

&Comp2Regs,

;

// ---------------------------------- USER -----------------------------------------

// ---------------------------- DPLIB Net Pointers ---------------------------------

V

// Declare net pointers that are used to connect the DP Lib Macros here

// CONTROL_2P2Z - instance #1

extern volatile long *CNTL_2P2Z_Ref1;

extern volatile long *CNTL_2P2Z_Out1;

extern volatile long *CNTL_2P2Z_Fdbk1;

extern volatile long *CNTL_2P2Z_Coef1;

// PWMDRV_1ch

extern volatile long *PWMDRV_1ch_Duty1; // instance #1, EPWM1

extern volatile long PWMDRV_1ch_Period1; // Optional

//ADCDRV_1ch

extern volatile long *ADCDRV_1ch_Rlt1; // instance #1, ADC

// ---------------------------- DPLIB Variables ---------------------------------

// Declare the net variables being used by the DP Lib Macro here

long Ref , Fdbk , Out;

#pragma DATA_SECTION(CNTL_2P2Z_CoefStruct1, "CNTL_2P2Z_Coef");

struct CNTL_2P2Z_CoefStruct CNTL_2P2Z_CoefStruct1;

// MAIN CODE - starts here

void main(void)

// INITIALISATION - General

// The DeviceInit() configures the clocks and pin mux registers

// The function is declared in ProjectName-DevInit_F2803/2x.c,

// Please ensure/edit that all the desired components pin muxes

// are configured properly that clocks for the peripherals used

// are enabled, for example the individual PWM clock must be enabled

// along with the Time Base Clock

DeviceInit(); // Device Life support & GPIO

VI

// INCREMENTAL BUILD OPTIONS - NOTE: selected via ProjectName-Settings.h

// ---------------------------------- USER -----------------------------------------

#if (INCR_BUILD == 1) // Open Loop Two Phase Interleaved PFC PWM Driver

// Configure PWM1 for 200Khz (Period Count= 60Mhz/200Khz = 300)

PWM_1ch_CNF(1, 300,1,0);

// Configure ADC to be triggered from EPWM1 Period event

//Map channel to ADC Pin

ChSel[0]=14; //Map channel 0 to pin ADC-B6

// ChSel[0] = 13; // ADC B5

// ChSel[1] = 3; // ADC A3

// Select Trigger Event for ADC conversion

TrigSel[0]= ADCTRIG_EPWM1_SOCA;

// TrigSel[0]= ADCTRIG_EPWM1_SOCA;

// TrigSel[1]= ADCTRIG_EPWM5_SOCB;

// Configure the ADC with auto interrupt clear mode

// ADC interrupt after EOC of channel 0

ADC_SOC_CNF(ChSel,TrigSel,ACQPS,0,2);

// ADC_SOC_CNF(ChSel,TrigSel,ACQPS,1,0);

// Configure the EPWM1 to issue the SOC

EPwm1Regs.ETSEL.bit.SOCAEN = 1;

EPwm1Regs.ETSEL.bit.SOCASEL = ET_CTR_PRD; // Use PRD event as trigger

for ADC SOC

EPwm1Regs.ETPS.bit.SOCAPRD = ET_1ST; // Generate pulse on every event

// Digital Power CLA(DP) library initialisation

DPL_Init();

// Lib Module connection to "nets"

// Connect the PWM Driver input to an input variable, Open Loop System

// Connect the CNTL_2P2Z block to the variables

CNTL_2P2Z_Fdbk1 = &Fdbk;

VII

CNTL_2P2Z_Out1 = &Out;

CNTL_2P2Z_Ref1 = &Ref;

CNTL_2P2Z_Coef1 = &CNTL_2P2Z_CoefStruct1.b2;

// ADCDRV_1ch block connections

ADCDRV_1ch_Rlt1 = &Fdbk;

// PMWDRV_1ch block connection

PWMDRV_1ch_Duty1 = &Out;

// Initialize the Controller Coefficients

CNTL_2P2Z_CoefStruct1.b2 = _IQ26(0.0);

CNTL_2P2Z_CoefStruct1.b1 = _IQ26(90);

CNTL_2P2Z_CoefStruct1.b0 = _IQ26(110);

CNTL_2P2Z_CoefStruct1.a2 = _IQ26(0.0);

CNTL_2P2Z_CoefStruct1.a1 = _IQ26(1.0);

CNTL_2P2Z_CoefStruct1.max =_IQ24(0.7);

CNTL_2P2Z_CoefStruct1.min =_IQ24(0.0);

// Initialize the net variables/nodes

Ref=_IQ24(0.5);

Fdbk=_IQ24(0.0);

Out=_IQ24(0.0);

// Duty1A =_IQ24(0.4);

// Out=_IQ24(0.0);

#endif // (INCR_BUILD == 1)

//====================================================================

// INTERRUPTS & ISR INITIALIZATION (best to run this section after other initialization)

// Set up C28x Interrupt

//Also Set the appropriate # define's in the ProjectName-Settings.h

//to enable interrupt management in the ISR

EALLOW;

VIII

PieVectTable.EPWM1_INT = &DPL_ISR; // Map Interrupt

PieCtrlRegs.PIEIER3.bit.INTx1 = 1; // PIE level enable, Grp3 / Int1

EPwm1Regs.ETSEL.bit.INTSEL = ET_CTR_PRD; // INT on PRD event

EPwm1Regs.ETSEL.bit.INTEN = 1; // Enable INT

EPwm1Regs.ETPS.bit.INTPRD = ET_1ST; // Generate INT on every event

IER |= M_INT3; // Enable CPU INT3 connected to EPWM1-6 INTs:

EINT; // Enable Global interrupt INTM

ERTM; // Enable Global realtime interrupt DBGM

EDIS;

//====================================================================

// BACKGROUND (BG) LOOP

//--------------------------------- FRAMEWORK -------------------------------------

for(;;) //infinite loop

// State machine entry & exit point

(*Alpha_State_Ptr)(); // jump to an Alpha state (A0,B0,...)

//END MAIN CODE

//====================================================================