Pi Control of a Dc Motor

Topics: Control theory, PID controller, Control engineering Pages: 31 (10558 words) Published: August 27, 2013
Department of Electrical & Computer Engineering
BSc. in Electrical & Computer Engineering

ECNG 2005
Lab and Project Design III

Individual Design Project
PI Control of a DC Motor
Keshan Kevin Babooram
Group F

Course Lecturer: Marcel Byron
Date Submitted: April 20th, 201
This project is based on the PI control of a DC motor with consideration given to a cooling fan application. This design also utilizes microprocessor as the controller. The designed system will have a means of overcurrent protection as a form of motor protection and will also use the rotary method of motor speed sensing. Also motor speed displayed 7 segment displays. Within project there will be algorithms that are to be implemented and the interfacing circuitry that is to be used when interfacing with the microprocessor.

Table of Contents
Background theory7
DC motor7
Control schemes7
Current sensing9
Motor protection10
Implementation of control algorithm11
Motor speed measurement12
Design Brief13
Production Design Specification15
Product life cycle16
Safety and standards17
Conceptual Design17
Control design19
Microprocessor design20
Controller design21
Mathematically modelling the system using the step response21
Determination of suitable performance specs23
Determination of key circuit parameters26
Finding the Armature Resistance26
Finding the Armature Inductance26
Finding the motor torque constant and the back EMF constant27
Finding the Time Constant for the system in the electrical domain28
Finding the Inertia28
Justification of choice of the controller29
Implementation of a PI controller29
Other Design Considerations34
Implementation of Motor Speed input routines34
Implementation of display output routines35
Implementation of Speed output routines36
Improvement of resolution of speed sensors37
Method for current sensing and motor protection37
Justification of choice oscillator38
Justification of component values chosen for driver circuit38
Lab Protocol39
Dress code39
Conduct and behavior39
Industrial standards40
Safety standards40
Component standards41
Codes of Practice42
Risk Assessment44
Presentation of results48
Key system variables and parameters48
Response of the system to PI control49
Accuracy of speed measured50
Test to justify motor protection50
Response to different inputs50
Interpretation of results51
Justification of load and system response51
Demonstration of the achievement52
Shortcomings and errors53

List of Tables
Table 1 showing results of the lock rotor test25
Table 2 showing the results form testing the motor26
Table 3 showing the risk definition43
Table 4 showing Risk assessment matrix44
Table 5 showing the findings of the risk assessment46
Table 6 showing the results obtained47
Table 7 showing the achieved parameters48
Table 8 showing the specifications obtained51

List of Figures
Figure 1showing a block diagram of the system17
Figure 2 showing a block diagram of controls section18
Figure 3 showing the block diagram of the micro-p system20
Figure 4 the output response of the system21
Figure 5 showing the flowchart of the PI algorithm29
Figure 6 showing the setup of the interrupter switch34
Figure 7 showing the setup of the segments35
Figure 8 showing the configuration of the driver circuit36
Figure 9 showing the step response of the system48
Figure 10 showing ramp input49
Figure 11 showing the output of the system50

List of...

References: "DC Motor Protection." Electric Motors and Industrial Electric Motors by OEM. http://www.ohioelectricmotors.com/dc-motor-protection-804 (accessed April 16, 2012).
"DC Motor Theory - Developer Zone - National Instruments." NI Developer Zone. http://zone.ni.com/devzone/cda/ph/p/id/52 (accessed April 16, 2012).
Goodwin, Graham C., Stefan F. Graebe, and Mario E. Salgado. "PID Theory Explained - Developer Zone - National Instruments." NI Developer Zone. http://zone.ni.com/devzone/cda/tut/p/
"Closed Loop Speed and Position Control of DC motors | IKALOGIC."IKALOGIC. IKALOGIC Electronic Solutions, n.d. Web. 10 Apr. 2012. <http://www.ikalogic.com/closed-loop-speed-and-position-control-of-dc-motors/>.
Babooram, Keshan. “Design Project -2004.” 2011.
MicroChip. n.d. http://ww1.microchip.com/downloads/en/devicedoc/41233a.pdf (accessed 4 13, 2012).
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