2009 International Conference on Engineering Education (lCEED 2009), December 7-8, 2009, Kuala Lumpur, Malaysia

Designing Learning Material for Engineering Course using Practice and Application Oriented

Approach

Azrita bt Alias, Ainain Nur bt Hanafi, Sahazati bt Md. Rozali, Ahmad Ismail bin Man

Faculty of Electrlcal Engineering Universiti Teknikal Malaysia Melaka (UTeM)

Melaka, Malaysia azrita@utem.edu.my, ainain@utem.edu.my, sahazati@utem.edu.my

Abstract -This paper discussed on the design of learning material for engineering course based-on practice and application oriented. The approach requires students to

experience the professional practice of their specialization and then apply their knowledge to solve industrial related problems. The concept is well established abroad in Germany's universities and other universities in Europe and Australia. UTeM is committed towards producing graduates who have scientific and

professional strength in the field of expertise, strength in applying and practicing the knowledge that they have learned and personal competencies in lifelong learning. The program structure, the curriculum and the syllabus need to be revised

from time to time in order to meet the objectives. The paper focused on designing a lab material for subject control systems

engineering. The practice based-learning material is illustrated and discussed on topics of modeling DC motor and designing PI, PD and PID controller. The paper also explained the typical conventional method and the proposed practice based-learning approach that have been introduced to undergraduate engineering students. A significant advantage of this method is

that it offers a deeper understanding and skill for students to integrate between theory and practice.

Keywords-Practice and application oriented; lab design; control systems; modeling DC motor; design controller

I. INTRODUCTION

Together with technological growth, teaching and learning process is a particularly challenging in engineering education field. The main goal of this process is to enhance understanding of a lesson and also to enable students to gain the learning materials efficiently.

Designing teaching and learning materials have been discussed among educators or researchers in response to improve learning and the growing interest in lifelong learning. Early teaching and learning materials used primitive methods to teach student such as drawing on stones and in the sand to share the information and communicate between each other. This method changed considerably as research and development in science and technology progressed. The invention of computer then changed the style of delivering lessons. In engineering education, a lot of researches had been

978-1-4244-4844-9/09/$25.00 ©2009 IEEE 186

done in designing the appropriate learning materials to fulfill the learning needs and met the industry requirements.

The examples of learning materials approach that most popular in engineering courses are practice based learning, problem based learning [1], active learning [2], outcome based learning and etc. This paper focused on practice based learning or also known as practice and application oriented approach, which is using laboratories implementation to model a system and design PID controller which is one of the important topics in engineering courses. A practical implementation for DC motor speed control system will be illustrated and discussed.

Even though the instructional technology [3] had been introduced with the miniaturization of computer technology and the increasing use of wireless technology, where students can access learning materials anywhere and anytime, we cannot deny the important of experience learning or laboratory practice. Laboratory approach is important elements in engineering education [4]. It allows the application and testing of theoretical knowledge in practical learning situations. Active involvement with experiments and problem solving does help students to acquire applicable knowledge that can be used in practical situations. This approach conveys the theoretical knowledge gained in lectures to practice during laboratory's sessions.

II. CONVENTIONAL METHOD APPROACH

In engineering courses, students studied a control system subject which included topics of modeling system, output response characteristics and further on designing appropriate controller such PI, PD and PID controllers. The conventional learning material placed heavy emphasis on text book. This approach had a limitation where students did not experience the real situation such as how to design the hardware of PI, PD and PID controllers.

A. Modeling The System

A mathematical model is a replica of some real-world object or system. It is an attempt to take our understanding of the process (conceptual model) and translate it into

2009 International Conference on Engineering Education (ICEED 2009), December 7-8, 2009, Kuala Lumpur, Malaysia

mathematical terms. The purpose of modeling is to predict and defme the performance of a physical system prior to actually constructing the full-scale system. The modeling concept is vital for control system in order to keep the ensuing model manageable and approximate physical reality. The system that will be discussed in this paper is DC motor.

Students studied how to derive a transfer function of DC motor using the electrical and mechanical equations in order to model DC motor. The transfer equation of DC motor [S] is given by (1),

{s+ J� (Dm + K��b)]

(1)

However the constant values such as Jm, Dm, Kt and Kb are given in the text book. Students just calculate to derive the transfer function or solve a theoretical problem yet not know­how these values are obtained from the real plant.

B. Designing Controller

Another topic that had been taught in control systems is designing the controller. A controller is needed by a system to improve the transient response and eliminate the error to meet the desired performance. The most common algorithm used in process control systems are Proportional, Integral and Derivative algorithms (PI, PD and PID). The PID control algorithm is made of three basic responses; proportional (or gain), integral (or reset), and derivative. In classroom, the method that generally used is the root locus technique. Students will be trained on how PI, PD and PID controllers are designed using this technique and observation on how the transient responses of the system changed when the values of gain Kp, K, and KD are altered. Figure 1 shows the basic block diagram of control system using PID approach.

The limitation of this conventional approach are students only understand the theory that PID controller can improve the system's performance, do a calculation, and draw the root locus to design the controller, yet no experience on the hardware implementation of these contollers.

Figure l.

Plant, G(s)

PID controller.

Output, C(s)

187

III. PRACTICE AND ApPLICATION ORIENTED ApPROACH

The opportunity to model the system and design appropriate controller of actual laboratory in subject control system engineering is a valuable experience that can reinforce important concepts and makes learning process more effective and interesting. Implementation of blended concept between theory and practice offers a precious knowledge and develop technical skills for student in order to produce a good engineer after they complete their undergraduate study.

Practice based learning, a combination of theory (lecture) and practice (lab session), is suitable for technical university especially UTeM which adopts Practice and Application education approach. The academic programmes at UTeM are designed to produce students with good academic foundation and high technical skills that enable them to develop into competent professionals capable of adapting fast evolving technologies [6]. This strategy is also applied in designing learning material for lab session that support lecture's activity to facilitate an effective teaching and learning environment. This paper focused on designing lab material for a topic in control systems engineering subject.. To address the need of more practice based learning experiences in control system course, a lab of control system is created for students and to help them integrate what they have learned in class and relate the theoretical with the hand's on activities.

A. Modeling The System

Student will practice a skill on how to model the plant (DC motor) using experimental data and appropriate equations.

To model a DC Motor, number of specifications needed to be obtained and recognized. The specifications of the DC motor were obtained from experiment, which included the speed, voltage, current, resistance and mechanical time constant. The results can be determined by the following procedure:

1. Measure the value of Ra by connecting an ohm meter to supply terminal of the dc motor. In this case the value of La is ignored because it is very small compared to Ra.

2. Measure the current, Ia. 3. Measure the speed of rotor by attaching the tacho meter

to the shaft. 4. Measure the output of the tacho generator to obtain the

mechanical time constant. S. Increase the supply voltage in step of S to take a few

readings. Repeat step 1 until S to obtain average values.

From the experimental results, the dynamic parameters of DC motor are calculated using formulas below:

di Back emf eb =V-I R -L -a a a dt

Angular velocity

(2)

(3)

2009 International Conference on Engineering Education (ICEED 2009), December 7-8, 2009, Kuala Lumpur, Malaysia

Angular acceleration

V Electromotive Force Constant Ke = Kt =­(0

Damping ratio

Rotor inertia

D = Iaeb

a

J=Dt

(4)

(5)

(6)

(7)

The values of dynamic parameters that obtained in (2) - (7)

are used to model the DC motor in Matlab Simulink. The relationship between electrical and mechanical system is derived using Kirchoff Law and Newton Second Law. In SI unit, Kt is equal to Ke. By considering Ke = Kt ' DC motor can be model as shown in Fig. 2.

Figure 2. A dynamic stucture of DC motor.

The ouput response of DC motor can be determined using Matlab Simulink in order to discover the output response's characteristics such as percent overshoot (%OS), settling time (Ts), rise time (Tr) and steady state error. The modeling process is important to predict and defme the performance of a physical DC motor and will be used to design the controller.

B. Sim ulation Im plem entation

Simulink provides a graphical user interface (GUI) for building models such as block diagrams, using click-and-drag mouse operations. Simulink includes a comprehensive block library of sinks, sources, linear and non-linear components, and connectors. Using scopes and other display blocks, the results can be viewed while the simulation is running. This feature creates a perfect learning environment for students to develop DC motor model using Simulink.

Refer to Figure 3, the model of DC motor is build inside the mask (subsystem block) as show in Figure 2. First, place the step input, scope, slider gain, and summing junction with an in connection subsystem block and an out of connection subsystem block, respectively. After a model has been defmed, it can be simulated and the result of input and output of the system easily displays through the scope as shown in

188

Figure 4. Students can see clearly the differences between output and input responses.

I DC Motor model I

Figure 3. Block diagram of closed loop system.

Figure 4. The scope's display of input and output.

C. Graphical User-Interface Im plem entation

Instead of using Simulink, user-friendly software has been developed to present the output response and the characteristics. A window based Graphical User Interface (GUI) software tool was developed, as shown in Fig. 5 to facilitate the teaching and learning environment on the topic of modeling DC motor and analyze the output response. This software is written in Microsoft Visual Basic 6.0 (VB) because of its' coding environment.

DC MOTOR SPEED CONTROL

Please Enter The Parameter or Motor

N ..... �III p-o--.R.IIII p-(�f_ p-'--[lIaoclk....-u p-O,

t� .... -- p-Tr.IIIII.,flllldMfI

r-.,.r-.. r-

Figure 5. QUI for DC Motor.

2009 International Conference on Engineering Education (lCEED 2009), December 7-8, 2009, Kuala Lumpur, Malaysia

By entering the parameter values of Jm, Dm, Kt and Kb,

the transfer function of 8m(s)/E.(s) will be displayed. The output response of open loop and closed loop can be examined as shown in Fig. 6. The output response's characteristics such as percent overshoot (%OS), settling time (Ts), rise time (Tr) and steady state error automatically calculated using this software.

OM

t.,.'.,.... .... (R) . r-c ... "" • r--

.r-­

.r-­

. r--

Figure 6.

F",,�. '''HL

I( ......... .....,..wyt-) jim �a..tr.I � s.ttIioocT_rr.) � ••• ,. ... T_cr,) I2ps-",,",_OYenIIoMc("..os) · �

� s...,.-S1M.ttn-or .. ) · �

Step response of closed loop system.

D. Hardware Im plem entation

Mill

An analog PID controller is the most popular feedback controller used within the process industries. It has been successfully applied for over 60 years. It is a robust and easily understood algorithm that provides excellent control performance despite the varied dynamic characteristics of process plant [5]. This project comprises an analog integrated circuit to present the closed loop system. The hardware implementation involves the construction of comparator, differentiator, integrator, power amplifier and summer that consist in the block diagram of the closed loop system as shown in Figure 7. The operational amplifier (op-amp) LM 741 was used to build up analog circuit of these elementslblocks. In theoretical, students are not taught that DC motor needs a power amplifier to drive the motor by amplified the current to move the rotor and make motor function.

error OlltPllt

feedback

Figure 7. Block diagram of closed loop system.

By developing the hardware, students will easily understand and relate the theoretical with the real application of PID controller. Summing junction is present using a differential amplifier or known as signal subtraction

189

configuration. Figure 8 shows the signal subtraction circuit that compares the V -set and feedback voltage that present by the output of the plant.

Vsel

Verror Vlacho

1OkO

Figure 8. Differential amplifier configurations.

The three terms of PID controller are realized using proportional amplifier, integrator and differentiator configurations. The formulas below present the representation of the PID controller into the op-amp configuration. Fig. 9

shows the realization of the mathematical equation of these configurations .

(9)

Where

Vo = (!l. + f_l

_ dt + R4C2 "!)Verror (8) R\ R3C\ dt

Proportional term

Integral term

Derivative term

.,

Figure 9. Analog PID controller configurations.

2009 International Conference on Engineering Education (lCEED 2009), December 7-8, 2009, Kuala Lumpur, Malaysia

The summing op-amp configuration is used to cascade the proportional, integrator and differentiator. In the real circuit, the gain of proportional (Kp), integral (KI) and derivative (KD)

can be adjusted by using the potentiometers. Table I presents the characteristics of passive device used for the system to make it operated between under damped and critically damped responses.

TABLE I. THE CHARACTERISTIC EQUATION OF PID CONTROLLER AND RELATION WITHIN PASSIVE DEVICE

Characteristics Equation Variable

Proportional R2 Rl =IKn

Rl R2 =10Kn

I 1 .5MQ> R3 > IMn s + --

Integral R3C1 C1 =lOOOuF

S

1 20Kn > R4 > lOKn

Derivative s + -- C2 =lOuF R4C2

IV. THE BENEFIT OF PRACTICAL ApPLICATION ORIENTED

ApPROACH

Cognitive learning theories see learning as an internal process that involves memory, information, processing and thinking [3]. Cognitive psychologist claim that humans have limited information processing resources in working memory and instruction must be designed to compensate for this limitation.

Practice application oriented approach is a good practice in engineering education. This approach give opportunities for students to experience actively the engineering works in order to develop their technical skills, where they can do a justification of principles used for design and measurement to achieve a deeper understanding of the concept or analysis. A

significant advantage of hands-on problem is that it allows the application and testing of theoretical knowledge in teaching and learning process. Hence, learning activities become more interesting and this practice can motivate students to think creatively in problem solving. The limitations of this approach can be seen in the costs and time. Cost and time require for this approach are higher.

V. CONCLUSION

This paper has looked at the implementation of an analog PID controller for DC motor speed control by using op-amp and power electronics devices. A learning material for lab activities has been proposed in this project including modeling, simulation and controller design. Modeling provides a foundation for designing the controller and gives an

190

expectation by doing a simulation before implement into hardware. The modeling helped immensely in optimizing the performance of system. Simulation is a method to plan the structure of the system and generate expected outcomes of the project design. While designing a controller give an opportunity for students to practice the theory they have learned in the classroom to the real application.

A lot of works needed to improve the learning material to make it more efficiency and appealing. Besides that, educators should identify suitable topics in engineering courses to implement this approach.

REFERENCES

[I] H.S. Barrows, How to Design a Problem-Based Curriculum for the Preclinical Years. New York: Springer, 1985.

[2] R.J. Dufresne,W.J. Gerace,W.J. Leonard, J.P. Mestre, and L.Wenk, "Classtalk: A classroom communication system for active learning," J. Com put. Higher Educ. ,vol. 7, pp. 3-47, Mar. 1996.

[3] Mohamed Ally, Designing Learning Materials for Successful Learning When Using Instructional Technology, Konvesyen Teknologi Pendidikan, K.Terengganu, 2005.

[4] Michael Auer and Dom Ursutiu, Distributed Virtual and Remote Labs in Engineering, IClT 2003 - Maribor, Slovenia, 2003.

[5] Varun Agraval et.al., "A Self Tuning Analog Proportional-Integral-Derivative (PID) Controller", Adaptive Hardware Group Computer Science and Artificial Intelligence Lab Massachusetts Institute of Technology.

[6] Ismail Hassan., Md Razali Ayob, Marizan Sulaiman, Abd Salam Md Tahir and Mohd Ridzuan Nordin, "Practice and Application Oriented Education At KUTKM", Penerbit Universiti KUTKM, 2005.

[7] Clark, R E., A Summary of Disagreements with the "Mere Vehicles" Argument, In RE. Clark (Ed.), Learning from media: Arguments, analysis and evidence (pp. 125-136), Greenwich Connecticut: Information Age Publishing Inc., 2001.

[8] Kozma, R B., Counterpoint theory of "Learning with Media". In RE. Clark (Ed.), Learning from media: Arguments, analysis and evidence (pp. 137-178), Greenwich Connecticut: Information Age Publishing Inc., 2001.

[9] H.V. Bateman, S.R Goldman, J.R Newbrough, and J.D. Bransford, "Students'sense of community in constructivist/collaborative learning environments," in Proc.20th Annu. Meeting Cognitive Science Society. Mahwah, NJ: Erlbaum, 1998, pp. 126-131.

[10] M.S. Donavan, J.D. Bransford, and J.W. Pellegrino, How People Learn By Doing. Washington, D.C.: National Academy Press, 1999.