This document describes the microcontroller-based digital control of a DC motor. It includes: 1) Modeling of the separately excited DC motor and determining its electrical and mechanical specifications. 2) Designing a current controller and speed controller in the frequency domain and simulating their performance. 3) The physical implementation of the hardware including a general block diagram and descriptions of the hardware design, firmware design, and software design. 4) An overall design of the system operation and a graph showing the motor speed tracking the set point speed over time.

1. Microcontroller – Based digitalMicrocontroller – Based digital
control of DC - motorcontrol of DC - motor
University of GaryounisUniversity of Garyounis
Faculty of EngineeringFaculty of Engineering
Electrical and Electronic Engineering DepartmentElectrical and Electronic Engineering Department

2. Project objectivesProject objectives
Modeling of separately excited DC motorModeling of separately excited DC motor
Control design and simulationControl design and simulation
Physical implementationPhysical implementation

3. Modeling of separately excited DC motorModeling of separately excited DC motor
Determination of electrical specificationsDetermination of electrical specifications
A
-
+
12
1 O h m
21
V 8
D C = 5 V
T o O s c i l l o s c o p e
RRaa = 3.1 ohm L= 3.1 ohm Laa = 0.822 Henry= 0.822 Henry

4. Determination of Mechanical specificationsDetermination of Mechanical specifications
Rotor moment of inertiaRotor moment of inertia
Viscous frictionViscous friction
Tm(S)Ia(S)
1/ (LaS + Ra) 1/ (JmS + Bm)
Kb
Kt
-TL(S)
Ω m(S)Ea(s)
-Eb(s)
++
JJmm= 0.04307 kg.m2 B= 0.04307 kg.m2 Bmm = 7.868 x 10-4 N.m/(rad/sec)= 7.868 x 10-4 N.m/(rad/sec)
KKbb= 0.46 Volt/(rad/sec)= 0.46 Volt/(rad/sec) KKtt= 0.46 N.m/A.Wb= 0.46 N.m/A.Wb

5. Project objectivesProject objectives
Modeling of separately excited DC motorModeling of separately excited DC motor
Control design and simulationControl design and simulation

6. Control design and simulationControl design and simulation
Current controller designCurrent controller design
Speed controller designSpeed controller design

7. Current Controller DesignCurrent Controller Design
Freq domain specificationsFreq domain specifications
Gain crossover freq = 10 rad/sec Phase margin = 60 degGain crossover freq = 10 rad/sec Phase margin = 60 deg
-40
-35
-30
-25
-20
-15
-10
-5
0
Magnitude(dB)
10
-1
10
0
10
1
10
2
-90
-45
0
Phase(deg)
Frequency (rad/sec)
UncompensatedSystemUncompensatedSystem
Corner frequency 1 Rad/SecCorner frequency 1 Rad/Sec

8. CompensatedSystemCompensatedSystem
Current Controller DesignCurrent Controller Design
Frequency (rad/sec)
-50
0
50
Magnitude(dB)
10
-1
10
0
10
1
10
2
10
3
-130
-120
-110
-100
-90
Phase(deg)
Corner frequency 10 Rad/SecCorner frequency 10 Rad/Sec
Phase Margin = 60 degreePhase Margin = 60 degree

9. Current Controller DesignCurrent Controller Design
Step response of current controllerStep response of current controller
0 0.2 0.4 0.6 0.8 1 1.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Time (sec)
Amplitude

10. Control design and simulationControl design and simulation
Current controller designCurrent controller design
Speed controller designSpeed controller design

11. -60
-40
-20
0
20
40
Magnitude(dB)
10
0
10
1
10
2
-225
-180
-135
-90
Phase(deg)
Bode Diagram
Frequency (rad/sec)
Speed Controller DesignSpeed Controller Design
Corner frequency 10 Rad/SecCorner frequency 10 Rad/Sec
UncompensatedSystemUncompensatedSystem
Gain Margin = 17.5 dBGain Margin = 17.5 dB
Phase Margin = 27.5 degreePhase Margin = 27.5 degree
Freq domain specificationsFreq domain specifications
Gain crossover freq = 4 rad/sec Phase margin = 60 degGain crossover freq = 4 rad/sec Phase margin = 60 deg

12. Bode Diagram
Frequency (rad/sec)10
-2
10
-1
10
0
10
1
10
2
-225
-180
-135
-90
Phase(deg)
-100
-50
0
50
100Magnitude(dB)
Speed Controller DesignSpeed Controller Design
Corner frequency 4 Rad/SecCorner frequency 4 Rad/Sec
CompensatedSystemCompensatedSystem
Phase Margin = 70 degreePhase Margin = 70 degree

13. Speed Controller DesignSpeed Controller Design

14. Project objectivesProject objectives
Modeling of separately excited DC motorModeling of separately excited DC motor
Control design and simulationControl design and simulation
Physical implementationPhysical implementation

15. Physical implementation: Hardware DesignPhysical implementation: Hardware Design
General Block Diagram of Hardware DesignGeneral Block Diagram of Hardware Design
DC SourceDC SourceDC SourceDC Source
InterfaceInterfaceInterfaceInterface DC ChopperDC ChopperDC ChopperDC Chopper DC MotorDC MotorDC MotorDC MotorDPWMDPWMDPWMDPWM
MeasurementsMeasurementsMeasurementsMeasurements

16. Firmware DesignFirmware Design
Start up & Initialize PeripheralsStart up & Initialize Peripherals
PWMPWM
Soft UARTSoft UART
A / DA / D
Start up & Initialize PeripheralsStart up & Initialize Peripherals
PWMPWM
Soft UARTSoft UART
A / DA / D
Wait the HostWait the Host
CommandCommand
Wait the HostWait the Host
CommandCommand
General block diagramGeneral block diagram

17. Main control programMain control program
Change Reference SpeedChange Reference Speed
Change Reference SpeedChange Reference Speed
PI-Speed ControllerPI-Speed Controller
PI-Speed ControllerPI-Speed Controller
PI-Current ControllerPI-Current Controller
PI-Current ControllerPI-Current Controller
Digital PW-ModulatorDigital PW-Modulator
Digital PW-ModulatorDigital PW-Modulator
RS-232 CommunicationRS-232 Communication
RS-232 CommunicationRS-232 Communication
Ref ChangeRef Change
Ref ChangeRef Change
NONONONO
STARTSTART
STARTSTART
YESYES
YESYES
Firmware flow chartFirmware flow chart

18. Software Design
Start MotorStart Motor
STARTSTART
Do EventsDo Events
Packet ReceivedPacket Received
Packet ProcessPacket Process
PacketPacket
TypeType
speedspeed
CurrentCurrent
Display currentDisplay current
signal on Excel sheetsignal on Excel sheet
Display speed signalDisplay speed signal
on Excel sheeton Excel sheet
Wait on next packetWait on next packet

19. Overall Design & System Operation
DC supplyDC supply
DC MotorDC Motor
Power MOSSFETPower MOSSFET
FreeFree
WheelingWheeling
DiodeDiode
Current TransducerCurrent TransducerSpeed Signal conditioningSpeed Signal conditioning
Current Signal conditioningCurrent Signal conditioning
PIC16F877APIC16F877A
RS232RS232
DutyDuty
InterfaceInterface
FloatingFloating
SupplySupply
VVgsgs

20. -20
0
20
40
60
80
100
0 2 4 6 8 10
Time (sec)
Speed(Rad/Sec)
Motor Speed
Set Point

21. Video 1Video 1
Video 2Video 2

22. BACKUPBACKUP