Teaching Control Systems Course for Electrical Engineering Students in Cognitive Domain Muhibul Haque Bhuyan Department of Electrical and Electronic Engineering Green University of Bangladesh, Dhaka E-mail: muhibulhb@gmail.com Abstract: Control systems course is a very important core course for the students of undergraduate program of electrical and electronic engineering. All types of industries require control system engineers whose efficient operation and controlling of the machineries produce optimum output. Therefore, Control Systems course has real life applications in the fields of electrical and electronic engineering and hence this course needs to be taught efficiently so that students can apply the knowledge earned from this course in solving their practical problems. Skills in the cognitive domain of Bloom's Taxonomy revolve around knowledge, comprehension, and critical thinking of a particular topic. This makes teaching and learning more effective and efficient. In this paper, the teaching method of Control Systems course for undergraduate electrical and electronic engineering students in the cognitive domain has been described. Index Terms : Control Systems, Teaching Methods, Bloom s Taxonomy, Cognitive Domain. I. INTRODUCTION Engineering is concerned with understanding and controlling the materials and forces of nature for the benefit of humankind. Control system engineers are concerned with understanding and controlling segments of their environment, often called systems, to provide useful economic products for the society. Effective system control requires that the systems be understood and modelled perfectly [1]. Control systems are used to achieve increased productivity and improved performance of a device or system with high precision [2]. All types of industries, such as, automobile [3-4], biomedical [5-7], telecommunication [8], robotics and automation [9], motion control [10] etc. require various types of control operations for optimum production and hence they need Control Systems engineers. Therefore, Control Systems course is a very important and useful course in the curriculum of the undergraduate program of electrical and electronic engineering (EEE). This course always occupies the core position in EEE curriculum. Therefore, this course is designed to teach the students various theories on designing and simulating the various types of Control Systems and also to operate them for uninterrupted output of the industries. So, this course should be designed and taught in such a way so that the students be prepared to master various rules and theories for designing the real-time Control Systems engineering problems [11]. Any engineering program should be mandated by an accreditation agency (such as, in USA it is Engineering Accreditation Commission of the Accreditation Board for Engineering and Technology, EAC/ABET) and the accreditation of an engineering program will be judged with respect to define program outcomes. Each program must have an assessment process for continuous improvement with documented results. Any well thought course required for an engineering degree should be able to contribute towards fulfilling the program educational objectives, which are mandated by the ABET criteria 2000 [12]. Currently, the education system is undergoing rapid changes. Various new methods are introduced and used. Further, it makes teaching more effective and learning is highly significant. An important goal of the undergraduate curriculum in engineering is to develop the integration, design, and evaluation capabilities of the student. As shown in Fig. 1, Bloom in 1956 characterized the six cognitive levels in the hierarchy: Knowledge Comprehension Application Analysis Synthesis Evaluation. The cognitive skills at the highest level are synthesis and evaluation, which rely on comprehension, application, and analysis capabilities in the knowledge domain, and are consequently the most difficult and challenging to teach. However, to prepare undergraduate courses to be effective in designing engineering systems in 64
the industry, it is important to ensure an adequate coverage of these higher-level skills, rather than limiting their education to one based on just knowledge, comprehension, application, and analysis [13]. Fig. 1 Levels in Cognitive Domain Before mentioned that, in engineering education there is a shift in emphasis from professional skills to process skills [14]. These skills include problem analysis and problem solving, project management and leadership, analytical skills and critical thinking, dissemination and communication, interdisciplinary competencies, intercultural communication, innovation and creativity, and social abilities [15]. In this paper, teaching method of the Control Systems course for the undergraduate students of the electrical and electronic engineering program in cognitive domain has been described with an example. II. CONSTRAINTS OF TEACHING CONTROL SYSTEMS Learning is an activity that leads to change and control of what is taught, while teaching is a practical activity or action, be intentional and conscious to assist learning. Teachers should act an essential role as a facilitator in the process of teaching and learning. We, as human beings, are born with certain limitations. Our memory is limited and we forget things very easily. If we learn and know certain things, our memory of those things decays almost exponentially unless the things are repeated. Thus, it does not matter what we teach, students will either forget or the materials will become obsolete, even before they graduate. Therefore, we should teach things in such a way to develop student s certain abilities. For example, we can rate the student s knowledge of the subject materials as zero at the start of the class. On the day of final, students should have the highest knowledge of the subject materials and we can rate the student s knowledge as logic 1 at the start of the exam. But, after one or two years, that knowledge would decay almost to logic 0, the same logic value as the start. The logic knowledge pattern can be described as {0 1 0} [16]. On the other hand, a student who never attended a class and earned no knowledge, his logic states of the knowledge can be described as {0 0 0}. But there is difference between a student who started with 0 knowledge, gained the highest knowledge (logic 1) and then forgot the knowledge (logic 0) and another student who started with 0 knowledge, did not gain any knowledge (logic 0) and no knowledge to forget (logic 0) [16]. Because, students gain some experience through this learning process. Hence teaching and learning process of the Control Systems course should be conducted in such a way so that the students gain some experiences in designing and analyzing the control systems after the end of the course. III. DESIGNING CONTROL SYSTEMS COURSE One of the desired attributes of an engineer [17-19] in the global marketplace in the new knowledge economy is that an engineer should have good understanding of engineering fundamentals and design/manufacturing processes. Therefore, any undergraduate course should be designed in such a way so that the students are able to design the systems both analytically and numerically. Keeping this in mind, Control Systems course is designed in the following way. I. Course Contents This gives the complete description of the course. The course contents should be designed in such a way so that the students get a deep knowledge and develop their skills to apply the knowledge in their fields and course objectives are achieved. Incorporation of too many topics in the course may impede the students learning objectives. So, the optimal contents for Control Systems course are set as follows: 65
Introduction to Control Systems: Definition of control systems, examples of modern control systems, mathematical modelling and control of linear feedback systems: Transfer Functions of Systems with Op-Amps, Electro-mechanical Systems, Modeling of DC Motors, Design of a Speed Control System, Design of a Position Control System, Signal Flow Graphs, Mason's Rule, Stability of Linear Feedback Systems: The Concept of Stability, BIBO Stability, Routh- Hurwitz Stability Criterion, Design of Stable Systems, Performance of Feedback Control Systems: Design Requirements Based on Time- Domain Performance Specifications, The Location of Poles and the Transient Response. The Root- Locus Method: The Rules of the Root-Locus Method, Analysis and Design using the Root- Locus Method, Parameter Design, Sensitivity and Frequency Response. The Nyquist Stability Criterion: Contour Mapping in the s-plane, The Nyquist Criterion. Frequency Response Methods: The Bode Plot, Performance Specifications in the Frequency Domain, Magnitude and Phase Plots, Design of Feedback Systems Using Frequency Response Methods. Introduction to Programmable Logic Controller (PLC). J. Course Objectives Learning objectives or instructional objectives are statements of what students should be able to do if they have acquired the knowledge and skills the course is supposed to teach them. The objectives of Control Systems course have been set as follows: 1. To know the basic features, configurations and application of control systems. 2. To know various terminologies and definitions for the control systems. 3. To learn how to find a mathematical model of electrical, mechanical and electro-mechanical systems 4. To know how to find time response from the transfer function 5. To find the transfer function via Mason s rule 6. To analyze the stability of a system from the transfer function 7. To sketch root locus and extract information from it. K. Course Outcomes Course outcomes or learning outcomes reflect the degree to which the program has met its objectives; outcome indicators, the assessment instruments and procedures that will be used to determine whether the graduates have achieved the outcomes. After successful completion of the Control Systems course with a minimum grade of C+, the students will be able to 1. Know the benefits of using control systems 2. Design and analysis of various control systems 3. Find out the transfer function of electrical circuits, mechanical and electromechanical systems 4. Describe quantitatively the transient response of first and second order systems 5. Find the overall transfer function from the block diagram and signal flow graph 6. Understand and determine the stability using the Routh-Hurwitz technique 7. Use root-locus design to meet stability and to find the transient response 8. Find the digital responses from the transfer function 9. Draw the block diagram from the dynamic equation and represent the time domain system in state-space form. IV. BLOOM S TAXONOMY The idea for this classification system was formed at an informal meeting of college examiners attending the 1948 American Psychological Association Convention in Boston. At this meeting, interest was expressed in a theoretical framework which could be used to facilitate communication among examiners. This group felt that such a framework could do much to promote the exchange of test materials and ideas about testing. In addition, it could be helpful in stimulating research on examining and on the relations between examining and education. After considerable discussion, there was agreement that such a theoretical framework might best be obtained through a system of classifying the goals of the educational process, since educational objectives provide the basis for building curricula 66
and tests and represent the starting point for much of our educational research [20]. Bloom's Taxonomy is a classification of learning objectives within education proposed in 1956 by a committee of educators chaired by Benjamin Bloom. Although named after Bloom, the publication followed a series of conferences from 1949 to 1953, which were designed to improve communication between educators on the design of curricula and examinations [21]. It refers to a classification of the different objectives that educators set for the students, i.e. the learning objectives. Bloom's Taxonomy divides educational objectives into three domains: Cognitive, Affective and Psychomotor (sometimes loosely described as knowing/head, feeling/heart and doing/hands respectively). Within the domains, learning at the higher levels is dependent on having attained prerequisite knowledge and skills at lower levels [22]. A goal of Bloom's Taxonomy is to motivate educators to focus on all three domains, creating a more holistic form of education. A revised version of the taxonomy was created in 2000 [23-25]. Bloom also considered the initial effort to be a starting point, as evidenced in a memorandum from 1971 in which he said, Ideally each major field should have its own taxonomy in its own language - more detailed, closer to the special language and thinking of its experts, reflecting its own appropriate sub-divisions and levels of education, with possible new categories, combinations of categories and omitting categories as appropriate [23]. Skills in the cognitive domain revolve around knowledge, comprehension, and critical thinking of a particular topic. Traditional education tends to emphasize the skills in this domain, particularly the lower-order objectives. There are six levels in the taxonomy, moving through the lowest order processes to the highest. Through these six processes a student gain knowledge and skills and be able to solve real life problems of their fields of interest. Therefore, to teach the Control Systems course for the undergraduate electrical and electronic engineering students, cognitive domain has been selected for teaching and learning process. V. COURSE OUTCOME ACHIEVEMENT IN COGNITIVE DOMAIN To determine the achievement of the course outcomes in the cognitive domain it is first necessary to analyze the educational objectives and corresponding learning abilities of the students at different levels of the cognitive domain. These are given in Table I. To illustrate that these educational objectives have been achieved in the Control Systems course, the turning control system design problem for a tracked vehicle has been selected [26]. This design problem involves the selection of two parameters of the system: one is system gain (K) and the other is the zero of the system (a). The whole system is shown in Fig. 2 (a) and its model is shown in Fig. 2 (b). The two tracks are operated at different speeds in order to turn the vehicle. The objective here is to select the values of K and a so that the system is stable and the steady-state error for a ramp command input is less than or equal to 24% of the magnitude of the command input signal [1]. The characteristics equation of the system is shown in equation (1). 1 G s G s 0 (1) c From the model in Fig. 2 (b), we can write equation (2). K s a 1 0 (2) s s 1 s 2 s 5 Finally, we can rearrange and write equation (3). 4 3 2 s 8s 17s K 10 s Ka 0 (3) TABLE I ACHIEVEMENT OF BLOOM S TAXONOMY OF EDUCATIONAL OBJECTIVES IN COGNITIVE DOMAIN [16] Cognitive Level Educational Objectives 1 Knowledge List, cite Learning Ability 2 Comprehension Explain, paraphrase 3 Application Calculate, solve, determine 4 Analysis 5 Synthesis 6 Evaluation Classify, predict, model, derive, interpret Propose, create, invent, design, improve Judge, select, critique, justify, optimize To determine the stable region of K and a, Routh-Hurwitz stability criteria is used and from 67
the Routhian array the range of K for which the system is stable is found. Then for the ramp input signal, r t At, t 0, the steady-state error (e ss ) was found. Finally, the relationship among e ss, K and a are determined and the stable region is found out by plotting the graph of a versus K. The maximum value of K and a have also been extracted from the graph [1]. Throttle Steering Power Train and Controller Track Torque Right Left Vehicle Y(s) Direction of travel Question: What is the purpose of finding the value of K? M. Comprehension At this level, students demonstrate understanding of terms and concepts and explain the concept in their own words and also interpret the results. Here, students demonstrate the understanding of the facts and ideas by organizing, comparing, translating, interpreting, giving descriptions and stating main ideas and also by extrapolation. Question: Can the students understand which method required to be used to find the value of K? s Difference in track speed Controller G c (s) a R(s) + Y(s) Desired - s 1 s s 2 s 5 direction of turning (b) (a) Power Train and Vehicle, G(s) Fig. 2 (a) Turning control system for a twotrack vehicle; (b) Block diagram with the transfer functions. How the educational objectives are achieved for this particular problem of control system design at six different cognitive levels is assessed in the following sub-sections to demonstrate the student s learning processes and skills upon the course contents. L. Knowledge At this level, students are provided with sufficient knowledge so that they can list or state the problems and also exhibit memory of previously learned materials by recalling facts, terms, basic concepts and answers. Knowledge may be of different categories, such as, Knowledge of specifics- terminology, specific facts Knowledge of ways and means of dealing with specifics- conventions, trends and sequences, classifications and categories, criteria, methodology Knowledge of the universals and abstractions in a field- principles and generalizations, theories and structures K N. Application At this level, students apply the learned information to solve a problem, to calculate or to solve for the required value. The students also solve problems to new situations by applying acquired knowledge, facts, techniques and rules in a different way. Question: What are the signs of the elements of the first column after the computation of the Routhian array? O. Analysis At this level, students break things down into their elements, formulate theoretical explanations or mathematical or logical models for observed phenomena, derive or explain something by identifying motives or causes. They make inferences and find evidence to support generalizations. They also do analysis of elements, analysis of relationships or analysis of organizational principles. Question: How many poles are the in the right half or left half of the s-plane using the Routh- Hurwitz stability criterion? P. Synthesis At this level, students create something combining elements in novel ways; formulate an alternative to the existing design. They also compile information together in a new pattern to produce a unique communication or to propose a set of operations or to derive a set of abstract relations. 68
Question: Can the students find the value of steady-state error, e ss from the value of K? Q. Evaluation At this level, students make and justify the values obtained by judgment or select an appropriate value among the various alternatives and also determine which one is better and explain its reasoning, analyze the values critically for accuracy and precision. They also opine by making judgments about information, validity of ideas or quality of work based on a set of criteria or evidences. Question: Can the students find the region of stability for a given value of e ss? VI. CONCLUSIONS The engineering graduates must be well prepared in the changing global competitive knowledgebased industry. Like all of us in the world, the engineering graduates must have the ability for knowledge management. Therefore, universities are facing challenges as well as opportunities for creating and transferring knowledge to the students in efficient and smart way for their survival. This paper describes the teaching and learning method of Control Systems course for electrical and electronic engineering students in cognitive domain, a critical learning domain that includes the recall of knowledge and cultivation of intellectual skills. Certain cognitive processes, such as, problem solving, critical thinking, reasoning, analysis and evaluations are very important in engineering tasks. Since Control Systems is an important core course in the curriculum of undergraduate electrical and electronic engineering program, therefore, this course must be taught in such a way so that the students are able to develop their knowledge and skills on designing and analysis of various types of control systems in their real life works. REFERENCES [1] R. C. Dorf and R. H. Bishop, Modern Control Systems, Addison-Wesley Longman Inc., USA, 8 th edition, ch. 1, 2005. [2] R. C. Dorf, Robotics and Automated Manufacturing, Reston Publishing, Reston, USA, 1983. [3] J. G. Kassakian, Automotive Electrical Systems circa 2005, IEEE Spectrum, August, 1996, pp. 22-27. [4] R. T. O. Brien, Vertical Lateral Control for Automated Highway Systems, IEEE Transactions on Control Systems Technology, May 1996, pp. 266-273. [5] B. Preising and T. C. Hsia, Robots in Medicine, IEEE Engineering in Medicine and Biology, June 1991, pp. 13-22. [6] S. S. Hacisalihzade, Control Engineering and Therapeutic Drug Delivery, IEEE Control Systems, June 1989, pp. 44-46. [7] J. R. Sankey and H. Kauffman, Robust Considerations of a Drug Infusion System, Proc. of the American Control Conference, SF, USA, June 1993, pp. 1689-1695. [8] H. S. Black, Inventing the Negative Feedback Amplifier, IEEE Spectrum, December 1977, Sect. II-E. [9] S. Pannu and H. Kazerooni, Control for a Walking Robot, IEEE Control Systems, February 1996, pp. 20-25. [10] Y. Y. Tzou, AC Induction Servo Drive for Motion Control, IEEE Trans. on Control Systems Technology, November 1996, pp. 614-625. [11] S. Choi and M. Saeedifard, An Educational Laboratory for Digital Control and Rapid Prototyping of Power Electronic Circuits, IEEE Trans. On Education, vol. 55, no. 2, pp. 263-270, May 2012 [12] Criteria for Accrediting Engineering Programs, Engineering Accreditation Commission of the Accreditation Board for Engineering and Technology (EAC/ABET), 2004. http://www.abet.org/ [13] D. R. Lewin, W. D. Seider and J. D. Seader, Integrated Process Design Instruction, Computers and Chemical Engineering, vol. 26, no. 2, 2002, pp. 295-306. [14] R. M. Felder and R. Brent, The ABC s of Engineering Education: Abet, Bloom s Taxonomy, Cooperative Learning, And So on, Proceedings of the 2004 American Society for Engineering Education Annual Conference & Exposition, American Society for Engineering Education, 2004, pp. 1375-1386. [15] S. Kuru, Problem Based Learning, TREE Teaching and Research in Engineering in Europe: Problem based and project oriented learning, Isik University, 2007, pp. 1-44. [16] M. H. Rashid, Cognitive-Based Teaching of Power Electronics, Proc. of the 5 th International Conference on Electrical and Computer Engineering (ICECE), 20-22 December 2008, Dhaka, Bangladesh, pp. 883-886. [17] M. H. Rashid, Improving Engineering Education, Proc. of the 3 rd International Conference on Electrical and Computer Engineering (ICECE), 28-30 December 2004, Dhaka, Bangladesh, pp. 1-5. [18] J. A. White, Defining the Knowledge Economy, ABET Annual Meeting, Incline Valley, Nevada, November 1, 2001. [19] D. O Swain, Global Corporations Leveraging Knowledge, ABET Annual Meeting, Incline Valley, Nevada, November 1, 2001. [20] B. S. Bloom, M. D. Engelhart, E. J. Furst, W. H. Hill and D. R. Krathwohl, Taxonomy of educational objectives: the classification of educational goals; 69
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