EXPERIMENTAL PROCESS CONTROL EDUCATION

EXPERIMENTAL PROCESS CONTROL EDUCATION Rub´en Morales Men´endez, Irma Yolanda S´anchez Ch´avez

ITESM Campus Monterrey, M´exico Center for Innovation in Design and Technology { rmm, isanchez } @itesm.mx

Abstract. The use of educational technology in a process control course for chemical engineering students at ITESM is shown. The topics of the course are determined by the automation needs in the chemical industry. The instructional style is intended to satisfy ABET criteria by active learning activities and the use of software and commercial equipment. The experimental education in this course complements lecture sessions. Experimentation with processes prepares students with valuable experience to handle industrial systems and apply theoretical concepts to real processes. Tests and open questions to start a problem solving process or a cooperative project about different control strategies in experimental stations are suggested. Experimental process control education is based on the premiss that practical experience favors the development of knowledge and professional abilities. Keywords: Process Control, Control Engineering Education, Experimental Education.

1. INTRODUCTION It has been argued that the modern engineer needs teamwork competencies and communication skills in order to apply technical knowledge in various circumstances (de Graaff and Ravesteijn, 2001). When knowledge is insufficient, the engineer must be able to find the information, so learning to learn is one of the most important goals in universities. ITESM 1 formally integrated a professors team for consulting, research and development of industrial projects in the automation area. This experience combined with modern teaching-learning systems has generated an educational technology in the automation field. Based on the engineering criteria of ABET 2 and ITESM mission, we have designed several control engineering courses combining Active Learning tech1

Instituto Tecnol´ogico y de Estudios Superiores de Monterrey, campus Monterrey, http://www.mty.itesm.mx 2 Accreditation Board for Engineering and Technology

niques, software systems and experimental didactic stations. The Chemical Engineering program at ITESM has two specialization fields: Systems (ChES) and Management (ChEM). ChEM students attend a single control engineering course in their last year. Given the relevance of the control engineering field, this course is the only opportunity to give the students a lifelong learning in the automation area. The paper is organized as follows. Section 2 lists the distinctive characteristics of chemical process control. Section 3 presents the bases for our course design. Section 4 describes the general main topics of the course. Section 5 shows experimental sessions that can be implemented in the laboratory. Section 6 shows our teaching-learning system. Finally, Section 7 concludes the paper.

2. CHEMICAL PROCESS CONTROL PRACTICE A chemical process control course differs significantly from the classical control courses for several reasons (Bequette and Ogunnaike, 2001): • Each chemical process is unique, so a new control system development for each process must be considered. Control systems are not as transportable to another similar process as electronic devices. Continuous control techniques are fundamental using PID controllers. • Usually chemical processes are nonlinear, high order and have multiple inputs/outputs. Linearization should be a consequence of a deep understanding of the process. • Chemical processes exhibit dead time, input constraints, and limited number of measured states. Also, some properties are impossible to measure directly or the instrumentation is expensive. • Chemical process are highly integrated systems, because of economical reasons; strong dynamic interactions are very common. • Sometimes there are different operating conditions in the same equipment (heating, cooling, etc.) to be managed with the same control system. Flexibility and robustness are mandatory in this problem. • Large-scale systems with large time constants allow to use advanced control techniques that demand high computing time. • Pharmaceutical, biotechnology and many classical chemical processes demand combinatorial and sequential logic control systems (MoralesMen´endez et al., 2006a). Additionally, • Control engineering depends on interdisciplinary technology. Measurement/actuation technologies are crucial. • Identification of the process is always needed, no matter how well analytical modelling is developed. • Physical changes can have a great impact on the process dynamics. On-line identification or adaptive systems could be mandatory. • Controller tuning is almost an art. Arts demand practice. Having this in mind, special considerations have to be taken for teaching/training CheM students in process control.

ITESM Mission. Based on a wide consultation with industry leaders, students, faculty, ex-alumni in Mexico, the new 2015 mission states several objetives 3 , one of them is to prepare students and transfers knowledge to promote the international competitiveness of business enterprises based on knowledge, innovation, technological development and sustainable development. ABET Engineering criteria. ABET Criteria effective for evaluations during the 2006-2007 accreditation cycle state that engineering programs must demonstrate that their students attain (only related outcomes to this paper are shown): (c) an ability to design a system, component, or process to meet desired needs within realistic constraints related to economy, environment, culture, ethics, health and safety, manufacturability, and sustainability, (e) an ability to identify, formulate, and solve engineering problems, and (k) an ability to use the techniques, skills, and modern engineering tools necessary for engineering practice. The ITESM mission, which follows ABET criteria demands new educational systems that can be implemented within the context of the ordinary engineering classroom and experimental laboratory.

3.2 Active learning techniques. Instruction that involves students actively has consistently been found more effective than straight lecturing in order to help the students to develop their problem-solving and thinking skills. Problem-Based Learning (PBL). Problems whose solutions demand the knowledge and the skills are the key for this technique. Teams of 3-4 students for each session follow this roadmap: • • • • •

The professor plays a consulting role upon demand for specific questions. Students gain better knowledge about problem-solving and lifelong learning skills are developed. Cooperative Learning (CL). We promote the following elements in the working team with this technique: • Each member is obliged to rely on one another. • Every member has accountable activities. • Interaction between members could range from sharing information to teaching and encouraging. • Developing skills such as leadership, decisionmaking, conflict management, etc. • Self-evaluation to improve the performance.

3. FUNDAMENTAL GUIDELINES 3.1 Principles Briefly, we review two basic documents that establish the principles that we follow for the design of all our engineering courses at Monterrey Tech.

Problem identification Task scheduling Solution generation Critical thinking Results evaluation

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http://www.itesm.mx/2015

Students are expected to achieve high-level reasoning and critical thinking skills, deeper understanding, lower level of anxiety and stress, and more positive and supportive relationships with coworkers (Terenzini et al., 2001). 3.3 Software and systems. There are 3 key software products that we exploit in order to be more efficient. We briefly describe each one. BlackBoard Academic. BlackBoard (BB) Academic Suite 4 enables us to embrace the power of the Internet with access to schedule, assignments, papers, examples, exercises, slides, software, videos and manuals at any time from any place. The use of BB is a standard at ITESM for promoting autonomous learning and documenting courses. Matlab software. Simulink and Matlab code have been used for teaching and training students before they start working with practical applications. Abstraction capability is developed with this software.

Figure 1. Temperature monitoring and control station The level is also measured with a differential pressure transmitter (LT100). The actuator is an electropneumatic control valve (FV100). The tank-level station was built using only industrial equipment. The instrumentation has standard analog (4-20 mA) and digital communication with a PID controller. The data acquisition is based on a commercial system, Fig. 3. Students can work locally or remotely for operation and configuration tasks. See (MoralesMen´endez et al., 2006b) for details about this station.

Control Station. Hands-on laboratories are important for learning because students can make the transition from theory to practice. However, sometimes an experiment might take hours to be implemented. This situation is overcome with a balance between laboratory practice and virtual experience, (Cooper et al., 2004). CStation is a training simulator that provides a broad range of engineering scenarios in an efficient, safe and economical fashion. 3.4 Educational Technology ITESM professors have designed educational equipment such as the portable temperature control station and tank-level monitoring and control station. These stations were designed based on three features. First, use of industrial control technology. Second, simulation through pilot processes of control problems associated with these processes. Third, use of industrial interfaces and data communication systems. Temperature control station. An air flow caused by a fan through a duct is heated by an electrical resistance, Fig. 1. The exit air temperature can be controlled by changing the shooting angle. The station includes interface circuits to allow digital communication with a personal computer through a serial port. Tank-level control station. The tank-level control system, Fig. 2, has a tank with uniform crosssectional area open to the atmosphere. There are two flow sensor-transmitter for the input and output flow. The flow measurements are done with orifice meter and differential pressure transmitters (FT101, FT102). 4

http://www.blackboard.com

Figure 2. Tank-level monitoring and control station.

Figure 3. Control systems interface. Through this interface every change is a few mouse clicks away. This interface is showing a cascade control system, left plot represents the dynamic behavior of the system and right plot shows both PID operator interfaces.

4. ACADEMIC PROGRAM The control engineering course for ChEM students is attended in the fourth year. Fig. 4 shows the academic

program. This course covers a broad range of control subjects relevant to industrial problems. Through this syllabus and the associated experimental laboratory, students are exposed to a wide variety of real life control problems such as dead time, model uncertainties, unmeasured disturbances, noise, valve hysteresis, etc. If we want to promote a student-centered learning system, we have to sacrifice some course topics and expect breadth for depth. Deep domain of critical analysis skills is preferred instead of a superficial overview of a large number of topics. Basically, professor gives motivating mini-lectures and a teaching assistant assigns experimental mini-projects to be discussed and solved in the laboratory.

Figure 5. Tank-Level feedback control system and cascade control system. can be altered by changing the V1 and V2 valve positions 5 which represents disturbances. Top plot in Fig. 6 shows the PV and SP variables for the level control system; bottom plot shows the Output (OP). Left section shows a servocontrol approach, where a SP change was implemented in both directions. Then the PID performance for the regulatory approach is shown. A disturbance in the input flow is implemented by changing the V1 valve position. The PID controller can cope with the disturbances, however a transient error (SP-PV) appears. 60

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Figure 4. Control Engineering Academic Program. The course is organized in 2 hr/week of lectures, 2 hr/week of experimental projects and 4 hr/week for complementary activities (reviewing papers, designing experiments, editing reports, etc.). Students form working teams (3 per team). There is one full professor giving the 2 hr/week lecture for every 12 teams and an Instructor of Laboratory (IL) giving support during the 2 hr/week of experimental projects for every 4 teams.

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Figure 6. tank-level feedback control system. A disturbance was implemented by changing the V1 valve position. Cascade control system. Cascade control can be tested with a slave control system (FIC-100) located inside a master control system (LIC-100). Cascade control takes corrective actions in response to disturbances V1 before the PV (LT-100) deviates from SP.

5. EXPERIMENTAL SESSIONS In order to show our ideas about Experimental Control Process Education we will present some examples about what the students can implement using the tanklevel control station for the last two topics (shadow square) of the academic program, Fig. 4. Feedback control system. Two feedback control systems can be configured: input flow (FT-101, PID, FV100) and tank-level (LT-100, PID, FV-100) control systems. The instrumentation diagram of the tanklevel control system is shown in Fig. 5 (left pic), and its performance in Fig. 6. The behavior of this system

6. TEACHING-LEARNING SYSTEM 6.1 Combined approach There are several reasons for using a combined approach. Theoretical approach fails to show students the real-life issues. Simulation-based assignments are used to illustrated problems that cannot be easily studied through lectures or analytical demonstration. 5

Plots in Figures (6-7) were generated from experimental data (Figure 3) and edited with Matlab.

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Figure 7. Tank-level cascade control system. A disturbance was implemented by changing the V1 valve position.

A brief example of how the cascade control system topic is taught based on Kolb’s experiental learning cycle is described:

Hands-on experiments reinforce learning because of practical application of course contents and motivation induced in the students. In order to confront students with real-world issues, the experimental laboratories must be built using industrial control equipment. However, hands-on experiments approach is inadequate since there is not enough time to work with all type of chemical processes.

• Why? stage. Introduction to the topic. Why is cascade control system important? What kind of problems can be solved? Industrial problems are presented to help students to appreciate this control strategy. Active learning environment helps to create motivation. Students are asked for watching some videos. • What? stage. Knowledge. Students must learn the fundamentals of cascade control. Students are asked to test cascade control systems using CStation and Simulink. Discussion is promoted among teammates based on simulation results. • How? stage. Applying the knowledge. After thinking, students are required to act. Students must identify the slave/master processes, potential disturbances, sensors, etc. Also, students must learn from product manuals how they can implement cascade control systems. The IL is responsible for supporting them. • What if? stage. Open-Ended problems. Students must solve real problems. Using the tank-level control station, students must implement a cascade control systems. Using some guidelines and open questions, students must: define the slave/master controllers, configure the cascade strategy, tune the controllers, compare with the servocontrol approach (Fig. 6 and Fig. 7), observe the performance when disturbances appear, explain how the cascade system works better than feedback system for both servocontrol and regulatory approaches. Also economical issues must be considered for comparison. The IL support students only in how to use the industrial equipment.

We found that a combined approach with lectures, simulation-based and experimental laboratories is much better, Fig. 8. We replicate this teaching-learning scheme for every main topic of the academic program. However, every stage changes in intensity and time according the topic.

Figure 8. Teaching-Learning Scheme. After an active learning session, students are asked to complement their knowledge working with software. Finally, a real application of the topic is realized in the experimental session. Everything supported by PBL and CL techniques. 6.2 Kolb’s experiental learning cycle The previous teaching-learning scheme follows the Kolb’s learning cycle, Fig. 9, (Kolb, 1984). This experiential learning cycle describes the steps required for complete learning. This learning theory is expressed as four-stage cycle of learning, in which concrete experiences (CE) provide a basis for observations and reflections (RO). These observations and reflections are converted into abstract concepts (AC) generating new implications for action which can be actively tested (AE)in turn creating new experiences.

6.3 Active-learning environment Every working team has its own personality, (Clough, 1998). Fig. 10 shows the level of interaction that typically working teams exhibit during the experimental sessions. Every square exhibits relative dimensions:

intensity × elapsed time. At the beginning, (stage I) students develop a rapport to work together. After socialization, (stage II) students start reading the problem definition and trying to figure things out such as equipment recognition. Then, (stage III) students start talking about doubts, suggestions, proposals, etc in order to find a solution. Based on their own conclusions, (stage IV) the solution is implemented, tested and evaluated. After completion, (stage V) students interact less only for checking data, results, etc. Finally, (stage VI) socialization starts again for feedback and celebration. The development of any skill is best facilitated by giving students practice and not by simply talking about what to do. The activities in each experimental session encourage two important issues: thinking about and reporting. This active learning environment is crucial for the how? and what if? stages of the Kolb’s learning cycle. The IL must take care of the level and time of interaction for several reasons. The experimental session must be completed in 2 hrs. IL must reduce (no eliminate) socialization stages (I and VI). The stage IV is the main reason of the experimental session, the IL must promote that every student participate actively. The stage III is important because the solution/implementation must be generated here.

Figure 10. Interaction level versus experimental session elapsed time For each problem that the students solve or team activity they accomplish, students are asked to write down reflections on how they approached the activity. There is an special report format that requires this critical thinking. 7. CONCLUSIONS We present how control engineering for chemical engineering and management (ChEM) students is taught at ITESM. The course is based on an experimental didactic stations which are equipped with industrial modern components. Software and systems are also used for achieving the learning objectives. With an emphasis on active learning teachniques, students are given the opportunity to apply theoretical concepts on real industrial processes. Practical experience gives

high motivation for students who consider ”control courses are too abstract and mathematical”. Also, students are encouraged to reflect on the processes through which they obtain that learning. In this way students become independent and able of continuous self-learning. Related work. Excellent works in the chemical engineering field with industrial equipment similar to ours have been contributed by (Clough, 1998), (Bequette and Ogunnaike, 2001) and (Ang and Braatz, 2002). Future work. An excellent reference to us is that many of our students are working in high positions in the automation business; however, we need to develop means of assessing how well the experimental learning objectives are achieved in order to improve our work (Olds et al., 2005). REFERENCES Ang, S. and R. D. Braatz (2002). Experimental projects for the process control laboratory. Chem. Eng. Education 36(3), 182. Bequette, B. W. and B. A. Ogunnaike (2001). Chemical process control education and practice. IEEE Control Systems Magazine pp. 10–17. Clough, D. (1998). Bringing active learning into the traditional classroom: Teaching process control the right way. In: ASEE Annual Conference and Exhibition. pp. 1313–1321. Cooper, D., R. Rice and J. Arbogast (2004). Gain hands-on experience in process control using control station. In: American Control Conference. Boston, Mass. pp. 1301–1306. de Graaff, E. and W. Ravesteijn (2001). Training complete engineers: global enterprise and engineering education. Eur. J. Eng. Ed 26(4), 419–427. Kolb, D. A. (1984). Experimental Learning: Experience as the Source of Learning and Development. Prentice-Hall. Englewood Cliffs, NJ. Morales-Men´endez, R., I. Y. S´anchez Ch´avez , J. Lim´on and R. Ram´ırez (2006a). Incorporating PLCs into a chemical process control course exploiting collaborative active learning. In: to appear in 6th Int. Workshop in Active Learning in Engineering Education. Monterrey NL, M´exico. Morales-Men´endez, R., I. Y. S´anchez Ch´avez , M. Ram´ırez and L. E. Garza (2006b). Control engineering education at Monterrey Tech. In: to appear in American Control Conference. Minneapolis, Minn, USA. Olds, B. M., B. M. Moskal and R. L. Miller (2005). Assessment in engineering education: Evolution, approaches and future collaborations. J. of Eng. Education pp. 13–25. Terenzini, P. T., A. F. Cabrera, C. L. Colbeck, J. M.Parente and S. A. Bjorklund (2001). Collaborative learning vs lecture/discussion : Students’ reported learning gains. J. Eng. Education 90(1), 123–130.