DESIGNING “PROBLEMS” IN A COURSE ON CONTROL SYSTEMS TO BE OFFERED THROUGH THE INSTRUCTION METHODOLOGY OF PROBLEM BASED L

1. DESIGNING “PROBLEMS” IN A COURSE ON CONTROL SYSTEMS TO BE OFFERED THROUGH THE INSTRUCTION METHODOLOGY OF PROBLEM BASED LEARNING C. B. Bhatt N. J. Rao

2. ABET Criteria 3: (Program outcome) • An ability to apply knowledge of mathematics, science and engineering • An ability to design and conduct experiments, as well as to analyze and interpret data. • An ability to design a system, component, or process to meet desired needs • An ability to function on multi-disciplinary teams • An ability to identify, formulate, and solve engineering problems • An understanding of professional and ethical responsibility • An ability to communicate effectively • The broad education necessary to understand the impact of engineering solutions in a global and societal context • A recognition of the need for, and an ability to engage in life-long learning • A knowledge of contemporary issues • An ability to use the techniques, skills, and modern engineering tools necessary for engineering practice.

3. Problem Based Learning • PBL is an instructional method based on the principle of using problems as vehicles for the acquisition and integration of new knowledge (Barrows 1982, Archibald). • There are many form of PBL, e.g. case study, guided design, research problem etc. • Problem can be run through course or module/s depending on nature of course.

4. Nature of PBL Problem • Open-ended • Real life • Apply multiple concepts • Require higher order thinking

5. Present Control System Courses • One course dealing with analysis and modeling, second one dealing in design • No common problem between analysis, modeling and design • Commercial hardware is not part of course

6. Bloom’s Taxonomy • Bloom and his team has developed a classification of levels of intellectual behavior in learning. • Three overlapping domain • Cognitive (mental skill) • Recall, Comprehension, Application, Analysis, Synthesis, Evaluation • Affective (emotion, feelings) • Receiving, Responding, Valuing, Organization, Characterization • Psychomotor (physical skill)

7. Vincenti Categories of Engineering Knowledge • W. G. Vincenti has identified six categories of engineering knowledge • Fundamental Design Concepts • Criteria and Specification • Theoretical tools • Quantitative data • Practical consideration • Design instrumentalities

8. Frame Work to design problem The framework that facilitates the design of problems is characterized by the following stages • Select a sub-set of criteria 3a – 3k • Identify learning objective in Bloom – Vincenti context • Design course content in detail by identifying modules and topics in module • Identify learning objectives of each module • Select specific PBL approach • Design “problems” in the context of selected 3a – 3k, LO and selected PBL • Identify and generate the learning material

9. Stage 1: Selection of subset of 3a – 3k • 3a (An ability to apply knowledge of mathematics, science and engineering) is chosen as every course will contribute to this outcome. • 3b (An ability to design and conduct experiments, as well as to analyze and interpret data) is addressed through problems which require mathematical modeling, simulation, interpretation of simulation data, select and installation, if possible, commercially available controller, and justify selection and setting of controller parameters. • 3c (An ability to design a system, component, or process to meet desired needs) is chosen, as it constitutes the main aim of the course. • 3d (An ability to function on multi-disciplinary teams) is not addressed in the course, as it is impractical to create multidisciplinary teams for a first level course in the Indian context.

10. Stage 1 (Continue) • 3e (An ability to identify, formulate, and solve engineering problems) is chosen, as it constitutes the central theme of a PBL approach. • 3f (An understanding of professional and ethical responsibility) is selected, as some of the control problems need to address quality, environment protection, safety, energy saving issues. • 3g (An ability to communicate effectively) is met as the PBL exercises are group exercises, and they require report preparation and oral presentations to the group members and to the class. • 3h (The broad education necessary to understand the impact of engineering solutions in a global and societal context) is not chosen.

11. Stage 1 (Continue) • 3i (A recognition of the need for, and an ability to engage in life-long learning) is addressed by posing open-ended real life problems. • 3j (A knowledge of contemporary issues) is not addressed in the course. • 3k (An ability to use the techniques, skills, and modern engineering tools necessary for engineering practice) is addressed through the use of modern engineering tools like MATLAB and selecting the commercially available controllers

12. Stage 2: Learning Objectives at Course level • After completing the course student will acquire the ability to analyze, design and evaluate SISO control systems of concern to electromechanical and chemical processes using MATLAB tools. • Define the terminology related to system, controller and control loop. (R, V1) • Explain in depth the design considerations for a control system. (C, V1, V2, V5) • Develop the mathematical model of a system. (AP, V1, V3, V4, V5) • Determine the performance of controllers and systems. (AP, V1, V3, V4) • Analyze the performance of a given SISO control system. (AN, V1, V2, V3, V4) • Design a controller for a given system for a set of specified performance requirements. (S, V1, V2, V3, V4, V5, V6) • Evaluate the performance of a given set of controllers. (E, V1, V2, V3, V4, V5)

13. Stage 3: Course content • Module 1: Introduction to Control Systems • Module 2: Modeling of Dynamic Systems • Module 3: Analysis of Control Systems • Module 4: Output Feedback Control Systems • Module 5: Controller Implementation Issues • Module 6: Nonlinearities in Control Systems • Identify list of topics in each module

14. Stage 4: LO at module level • Write LO for each module in Bloom-Vincenti Context

15. Stage 5: Selection of PBL approach • Two problems, one from electromechanical and another from chemical process control, will be used through the course to present all the concepts of course (as case study) • Open ended problems (include concepts not included in case study) will be given as group exercise and students will be guided to approach solution. (guided design) • Lectures will be conducted to reinforce the concepts and introduce concepts not included in case study problems.

16. Stage 6: Design of Problem (A real-life problem from chemical process industry is presented) Chemical reactors are widely used in industries like pharmaceutical, fertilizers, petrochemicals etc. Chemical reactor needs different types of controls like concentration of output product in spite of the concentration change in input feed. Many reactors need control of operating conditions for safe operation and quality output product. Operating temperature and pressure control is very crucial in many chemical reactors for safety and quality output.

17. Problem The schematic diagram of an isothermal CSTR reactor in a pharmaceutical plant is given in figure. A First order reaction takes place as A → B. A plant manager wants to sell a reactor exit stream with a concentration of Cb = 9 g/L. A steady state concentration of A, in feed is 10g/L, but it experiences disturbances. In spite of disturbance in concentration of A in feed it is required to maintain the concentration of B. (Concentration in B must not deviate from its desired value for a long time to minimize the waste and eventually the financial loss). Design Controller to maintain concentration of B.

18. Module 1 • Why do we need control in this reactor? • What are the controlled variables, manipulated variables and disturbance (load) variables? • How many ways can you control output concentration? Give an outline of your scheme. • Identify and explain function of each element in your control schemes. • Explain pros and cons of different schemes you have suggested.

19. Module 2 and Module 3 • How is the controlled variable related with manipulated variable and disturbance variables? • If the concentration of input stream A is changed by 1% how much change will there be in concentration of output stream B? • If flow rate of A is increased by 5% in what way it affects output stream concentration? • Write differential equations to describe the system behavior? Is the resultant equation linear? • What do you propose to do with any nonlinearities present? • Identify state variables of the system • Prepare state space model for the system.

20. Module 2 and Module 3 (Continue) • Using MATLAB find out the responses of controlled variable for change in manipulated variable and disturbance variables. And find out how much, and how fast? • If disturbance is constant for a long time, what type of response you wish to measure to analyze the effects of such a disturbance? What information will you get from that response? • If the disturbance is for a very short time what type of response you wish to measure the effects of such a disturbance? What is the nature of information you get from that response? Etc…..

21. Module – 4 • You need to improve system performance by designing a controller. Specify performance requirement considering the situation that if concentration of B is deviated much beyond certain limit customer will not accept that part of product and if the deviation stays for long time there will be more rejection of the product. • Identify the structure of the controller to be used to meet specified performance. Justify your decision. • Design three different controllers that meet the specified performance requirements. • If you have been given a more than one controller that meet performance criteria, then what criteria will you use to select one of the controllers?

22. Module 5 As a control engineer you are responsible to procure a commercially available controller, install it and tune it to meet the performance requirements • Prepare a list of commercially available controllers and their features. • Prepare selection criteria to select the controller. • Simulate the system with all it nonlinearities with the selected controller. • What additional hardware would be needed with the controller for the system to be complete?

23. Module 6 • Find out the source of nonlinearities in a given process or control loop? • What nonlinearities are added if the control valve used is of equal percentage type? How does it affect the system performance? What action will you take to compensate for the nonlinearity?

24. Conclusion Here a framework to design problems to implement PBL is presented in the context of ABET criteria, Blooms taxonomy, and categories of engineering knowledge identified by Vincenti. An example of such a problem is presented for the first level course in control system design at under graduate level that meets all the criteria identified.

25. Thanks