UNIVERSITI TUNKU ABDUL RAHMAN

Faculty : Engineering & Science Unit Code : UEEA2663Course / Session

: 3E / 201401 Unit Title : Electrical Drives

Year/ Semester

: Tutorial group

:

Student’s Name

: Student’s ID

UEEA2663: ELECTRICAL DRIVES

Lab - 1

Design and Evaluation of DC Motor Speed Control Methods using MATLAB / SIMULINK

Student’s acknowledgement:

Date Signature Marks awarded

Submitted on

Received the marked report

UNIVERSITI TUNKU ABDUL RAHMAN

Design and Evaluation of DC Motor Speed Control Methods using MATLAB / SIMULINK

AimThe aim of this simulation is to design and evaluate the various DC motor speed control methods using MATLAB / SIMULINK.

ObjectiveThe objective of this experiment is to design and evaluate the simulation models of DC motor speed control methods. These models include Simulink models of three most common speed control methods, namely field resistance, armature voltage, and armature resistance control methods, and feedback control system for DC motor drives.

IntroductionThe speed of a DC motor can be varied by controlling the field flux, the armature resistance or the terminal voltage applied to the armature circuit. The three most common speed control methods are field resistance control, armature voltage control, and armature resistance control. In this section, Simulink models of these three methods and feedback control method for DC motor drives for dynamic analysis are presented. In the field resistance control method (Fig.1), a series resistance is inserted in the shunt-field circuit of the motor in order to change the flux by controlling the field current. It is theoretically expected that an increase in the field resistance will result in an increase in the no-load speed of the motor and in the slope of the torque-speed curve.

In the armature voltage control method, the voltage applied to the armature circuit, Va is varied without changing the voltage applied to the field circuit of the motor. Therefore, the motor must be separately excited to use armature voltage control. When the armature voltage is increased, the no-load speed of the motor increases while the slope of the torque-speed curve remains unchanged since the flux is kept constant.

Fig:1 Fig.2

2

UNIVERSITI TUNKU ABDUL RAHMAN

In the feedback speed control system (Fig.3) for DC motor drives, the control objective is to make the motor speed follow the reference input speed change by designing an appropriate controller. The proportional-integral (PI) controller is used to reduce or eliminate the steady state error between the measured motor speed (ω) and the reference speed (ωref) to be tracked. The transfer function of PI controller is given by

where Kp and KI are the proportional and integral gains. In the feedback control system, the dynamics of the DC motor can be described either by a transfer function or by the following state-space equations:

where x1 = ia, x2 = ωm are the armature current and motor speed in rad/s, respectively; u is the voltage input applied to armature circuit, Tl is the load torque, J is the combined moment of inertia of the load and the rotor; B is the equivalent viscous friction constant of the load and the motor, and K is the design constant depending on the construction of the motor.

Fig.3: Block diagram of the feedback control system for DC motor speed control

Reference Saffet Ayasun, Gultekin Karbeyaz, “DC motor speed control methods using

MATLAB/SIMULINK and their integration into undergraduate electric machinery courses”, Computer Applications in Engineering Education, Volume 15, Issue 4, pages 347–354, 2007

Methodology1. Consider a DC shunt motor of any suitable rating and suitable parameters.2. Tabulate the ratings and the parameters of the motor.3. Create the SIMULINK model of the motor considered in methodology 1 for the

following three cases: Field control of DC shunt motor Armature control of DC shunt motor Feedback speed control of DC shunt motor

4. Evaluate the SIMULINK model for the field control of DC shunt motor Choose the nominal value of the field resistance.

3

UNIVERSITI TUNKU ABDUL RAHMAN

Run the simulations for a wide range of load torque. Obtain the steady-state value of speed at each load level and tabulate the

readings. Increase the field resistance and repeat the simulation for the same load

levels. Obtain the steady-state value of speed at each load level and tabulate the readings.

Plot the torque-speed curves for both resistance values and investigate the effect of an increase in the field resistance on the torque-speed characteristics.

5. Evaluate the SIMULINK model for the armature control of DC shunt motor Choose three different values of the armature voltage (while the field

circuit is kept constant at its nominal voltage) Run the simulations for a wide range of load torque. Obtain the steady-state value of speed at each load level and tabulate the

readings. Plot the torque-speed curves for all the armature voltages and investigate

the effect of the armature voltage on the torque-speed characteristics. Choose three different values of the armature resistance. Run the simulations for a wide range of load torque. Obtain the steady-state value of speed at each load level and tabulate the

readings. Plot the torque-speed curves for all the armature resistance values and

investigate the effect of the armature resistance on the shape of the torque-speed characteristics.

6. Evaluate the SIMULINK model for the feedback speed control of DC shunt motor (Steady-state and transient behaviour of the DC motor)

Apply a step increase in the reference speed for different values of the proportional gain (Kp) while the integral gain (Ki) is kept constant.

Obtain the values of the motor speed as a function of time and tabulate the readings

Plot the motor speed (rad/s) as a function of time for different values of Kp

and investigate the effect of the gain on the motor speed. Repeat the above simulation (methodology 6) with different values of the

integral gain (Ki) while maintaining the proportional gain (Kp). Plot the motor speed (rad/s) as a function of time for different values of Ki

and investigate the effect of the gain on the motor speed.7. Discussion and conclusion

Discuss the effect of the field resistance on the torque-speed characteristics.

Discuss the effect of the armature resistance on the torque-speed characteristics.

Discuss the effect of the armature voltage on the torque-speed characteristics.

Discuss the effect of the proportional gain on the motor speed. Discuss the effect of the integral gain on the motor speed. Discuss briefly what you have learnt from this simulation assessment.

4

UNIVERSITI TUNKU ABDUL RAHMAN

General instructions & instructions on report writing1. Students are advised to read through the lab instructions and collect the required

information for completing the simulation, before coming to the laboratory.

2. Ensure appropriate attires: no slippers, sandals or open-toe footwear are allowed.

3. The students should attend the lab only on the day assigned to them. Free jumping to alternate days is not allowed.

4. On-the-spot evaluation may be carried out during or at the end of the lab session.

5. Student’s performance, teamwork effort (if applicable), and learning attitude will count towards the lab marks.

6. The lab report must be submitted within two weeks of the completion of the lab work. A penalty applies for late submission.

7. Presentation of Report: Structure of report (Title, introduction, main body, conclusion and

references) Aims and objectives are clearly stated Theory and procedures are explained clearly Good use of diagrams, tables and pictures Readability, logical flow Well written discussion and conclusion Free from spelling and grammatical errors Neatness of the report

5