A Practical Servomotor Project- Combining the Web With Simulation

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Electrical and Computer Engineering

6-1-1998

A practical servomotor project: combining theWeb with simulation tools to solidify concepts in

undergraduate control educationM S. ZywnoRyerson University

D C. KennedyRyerson University

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Recommended CitationZywno, M S. and Kennedy, D C., "A practical servomotor project: combining the Web with simulation tools to solidify concepts inundergraduate control education" (1998).Electrical and Computer Engineering Publications and Research. Paper 11.hp://digitalcommons.ryerson.ca/ee/11
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Proceedings of the American Control ConferencePhiladelphia, Pennsylvania June 1998A Practical Servomotor Project: Combining the Web withSimulation Tools to Solidify Concepts in Undergraduate

Control EducationMalgorzata S. Zywno and Diane C. KennedyDepartment of Electrical and Computer Engineering, Ryerson Polytechnic University

350 Victoria Street, Toronto, Ontario, M5B 2K3, CANADAE-mail:[email protected],[email protected]

AbstractCurrent technology enables the lecturer to use com-

puter tools to enhance the conceptualisation of lecturematerial. This can be especially useful in an engineeringcurriculum, as the course material can be rendered lessabstract through visual illustration of difficult mathem-atical concepts.

In this paper, we present an example of a multime-dia enhanced course in linear control theory, taught byauthors at Ryerson Polytechnic University (Toronto,Canada). In our implementation of the course, wecombine software simulations of practical systems to il-lustrate control theory concepts with extensive on-linecourse notes to assist with comprehension.

Followup analysis shows that the use of the WWWand computer tools to enhance the learning processleads to increased enthusiasm, comprehension, and in-formation retention. A review of the process requiredto create the technology enabled learning environmentshows that initially there is a great deal of work in-volved. However, we conclude that the effort is justifiedby allowing a positive qualitative change in the way weeducate engineering students.

Key Words- Control Engineering Educa-tion; Multimedia Applications; World WideWeb.

1. IntroductionOne of the required courses for undergraduate stu-

dents of Electrical and Computer Engineering is the in-troductory course in classic linear control theory, typ-ically taught in the third year of study. Embedded inthis course are mathematical concepts of control theory,which are often difficult to grasp. For example, top-ics such as convolution, contour mapping, r the effectsof poles and zeros on system response are sometimeseasier to understand if we exploit an engineers inher-ent preference to use visualisation rather than to thinkin an abstract fashion. In fact, classical approaches toteaching often include the use of chalkboard diagrams

and graphs in conjunction with lecture notes, to as-sist in explaining the mathematical intricacies of con-tro l theory via visualisation of the concepts. Finally, toimprove comprehension and retention, tutor ials, assign-ments, and associated laboratory experiments round outthe typical course delivery.

In Ryersons curriculum, the laboratory componenttends to be quite demanding. Furthermore, i t is import-ant to note that this is the first time that the studentis required to deal with a more complex experimentthan can be resolved in a single standard three hourlab session. The laboratory experiments are also usedto implicitly provide an additional benefit of laying thefoundation for future pralctice of control engineering inindustry.

In our work, we adopt an approach which combinesmultimedia tools with some of the components of thetraditional course curriculum to yield several improve-ments to the overall course delivery. In order to achievethese improvements, we base a portion of our develop-ment on knowledge gained from the experience of otherresearchers in the area of control education who havelooked at the usefulness of including multimedia toolsto enhance learning. For example, the work of [l ]de-scribes how one may enhance the visualisation processand understanding of the theory of control engineeringthrough provision of variety of online (Matlab) tutori-als/simulations. The work of [2] allows access to avirtual control laboratory to perform a variety of ex-periments which help to develop an awareness of theapplication of the theory to practice. We make use ofideas such as HTML based tutorials and the provisionof software simulations of practical systems to illustratecontrol theory concepts.

Section 2 of this paper describes the lecture compon-ent of the course, showing how the WWW may be ad-vantageously used to disseminate lecture material, tu -torial notes, assignments and course updates. Section3 describes the laboratory component of the course, inwhich a DC servo motor setup is used throughout avariety of experiments over the course of a semester.

Matlab is a registered trademark of The Mathworks, Inc.0-7803-4530-4198 $10.00 0 1998 AACC 1309


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Section 4 focuses on the final course project, and servesto illustrate how combining the Web with simulationtools helps to solidify control engineering design con-cepts. The paper concludes with an evaluation of boththe development and implementation of the course.

2. The Undergraduate Course in LinearProcess ControlThe lecture component of the course deals with the

mathematical modeling, analysis, and design of linear,time-invariant systems and controllers. The curriculumincludes a comprehensive treatment of the basic proper-ties of feedback control, the design of the classic three-term (P ID) controller, controller tuning, stability ana-lysis] and frequency response compensation techniques.

Underpinning these topics are complex mathemat-ical foundations, which we find difficult to communicateproperly to students when one is limited to classic teach-ing methods. Furthermore, teaching the design aspectsof the course inherently requires an iterative processwhich can be greatly enhanced by introducing multime-dia tools to illus trate the results. For example, considerthe topic of pole/zero locations, and their subsequenteffect on system behaviour. At best, using a classicapproach, one is resigned to the tedious task of sketch-ing diagrams of the system response, typically to a stepinput, for various pole locations. Contrast this to themuch more illustrative means provided by [3] in whicha Java applet allows one to place the singularities any-where in the complex plane, and immediately see theresults, or to a Matlab movie, showing a transitionfrom a pole-zero map to a frequency response plot, [4].Both of these visualisations are embedded in the HTMLpages and can be accessed on the World Wide Web withnothing more than a browser as a tool. Another im-provement is to use software with a user friendly inter-face, such as a Matlab GUI applet, or Simulink2 simula-tion, allowing instant modifications (i.e. interactivity)without programming, such as in [5].2.1. Incorporating Multimedia Components inLectures

In the classroom, hyperlinked textual information iscombined with simulations and multimedia componentsprovide a visualisation of the theory, and can illustratereal-life implementations thereof. Online availability ofa complete set of lecture notes, containing embedded ex-amples and tutor ials frees the students to actively parti-cipate in the lecture process. The notes are accessed ata password-protected Web sit e and downloaded throughFTP. We are also investigating the option of providingstudents with a CD-ROM copy of the lectures and tu-torials in the next offering of the course, and with theWWW used to update and add to the information.

including video clips and screen captures, which readily

2Simulink is a registered trademark of The Mathworks, Inc.

The initial big picture lecture, in which we attemptto provide the students with a flavour of the course, is agood example of the effective use of multimedia. In theabsence of any theoretical frame of reference and yetto be defined (jargon, we use video clips embedded inthe HTML lecture notes to provide a visual, intuitiveunderstanding of what is process control. We demon-strate the differences between effective and poor controlwhile illustrating concepts of stability and instability]and transient system behaviour via a practical systemsetup. Using multimedia over a real-life demonstra-tion has the advantage of being portable, faster, andallows us to use a variety of examples. For our coursewe created QuickTime movies of an inverted pendulumsetup and two different servo positioning systems.

Outside of the classroom, implementing interactivitythrough the simulation software is a bit more complic-ated, since students must have access not only to tutori-als through a browser, but they also require the StudentEditions of Matlab and Simulink to be simultaneouslyrunning on their PC. Our current Web-based modulesprovide both lecture and lab tutorials that contain hy-pertext links to Simulink files which can be downloaded,executed and modified as required. Matlab commandsare displayed in HTML documents, and can be cut andpasted into the software command window. Tutorialfiles also include captures of screen activity, and areeffective in illustrating the use of Simulink drag-and-drop icons and in demonstrating simulation results. Tu-torial screen captures, encoded using Lotus Screencam,are converted into animated GIFs to avoid a need forbrowser plug-ins and helper applications.

3. Practical Servomotor Pr o j e c tTheory in the course is reinforced by hands-on exper-

imental work and computer simulations using Matlaband Simulink. Lab projects utilize a positioning servosetup, shown in Figure 1.

: 486AT DSPBoard I IXArmatureControlledMotorI comuter n_.erial 16-bi La+Power: K=2.25

Figure 1: Block Diagram of the Servo Module.The servo implements a high precision geared DC

motor, equipped with an HP incremental optical en-1310


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coder, and a Motorola digital signal processing boardwith 16 bit D/A nd A/D onverters. The servo, witha pointer as its load, is enclosed in a rugged casing.The software, developed in-house, allows students toimplement real-time PID or lead-lag control of the servothrough a simple menu-driven interface. A choice ofthe positioning servo as an example of a process to becontrolled has several advantages. It gives students in-sight into a range of real life phenomena such as sat-uration, gear backlash, and nonlinear friction, whileproviding reliable laboratory setups for students to ob-tain repeatable measurements throughout the semester.The setups are flexible and allow for a future expansionto implement more challenging control problems. Thevisual aspect of a functioning control system should notbe overlooked as well; a servo system, be it a cuttingtool, or an inverted pendulum, is more effective in illus-trat ing basic concepts to novices than say, a temperat-ure control system, even though it may be of the samedifficulty on a conceptual level.

3.1. Lab DescriptionExperiments performed in the lab are tied closely to

the theory covered in lectures and progress from systemidentification, to a simple controller design and imple-mentation, to a 2-dimensional trajectory control prob-lem. The lab format is 3 hours/week over the 13 weekcourse. In the first of three experiments a model of theservo is derived using a classic approach based on stepand frequency response measurements. The final modelincorporates known nonlinearities and is verified usingSimulink. In the second experiment an effective control-ler is designed and verified through simulations, thenimplemented in the physical setup. Unlike in many in-troductory courses in linear control, real life nonlinear-ities and resulting implementation implications are dealtwith. For example , an anti-windup controller scheme isimplemented, counteracting effects of saturation in thecontroller output, resulting from a limited range of theD/A onverter (only f1.4 olts). The final experimentis a Simulink simulation project described in Section 4.

3.2. Incorporating Multimedia Components inLab Instruction

In a lab context, the Web is effectively used to dis-seminate project schedules, PostScript files of lab in-structions, Matlab and Simulink files, and tutorials onsoftware use. Students are introduced to the networkedenvironment (Unix) and to Matlab in earlier coursesin the second year of our curriculum, but are not ini-tially familiar with the Matlab Control Toolbox pack-age. While the purchase of Student Editions of bothMatlab and Simulink software is recommended in theControl course, many students opt to rely exclusivelyon the network version available on campus. Some pur-chase just Matlab, as it is used in other courses. Ineither case, without access to manuals, their ability toattain proficiency in the control aspects of Matlab and in

Simulink is hindered. Since that proficiency is expectedvery early on in the course, online tutorials have the ad-vantage of providing effective asynchronous delivery ofthe basic information and exercise material . Instructorsand teaching assistants are relieved of fielding repetitiveinquiries of the software basics.

Tutorials containing embedded simulations also proveto be an effective tool in delivering information aboutpractical, but unfamiliar aspects of the servo modulethat fall outside the conventional linear control theory,such as how to identify arid deal with DC offsets, D/Aquantization errors and saturation, gear backlash anddeadzone.

4. Servomotor Driven X-Y Cutting ToolSimulation Project

The final project in the course deals with an x-y mo-tion control problem. Currently a computer simulation,this project will eventually have a hardware implement-ation using a multichannel DSP board , two servomech-anisms and an x-y plotter as an analogy to a cuttingtool. Simulink models of the problem is shown in Fig-ures 2 , 3 , and 4.

ermr xr ntrm xII

1nu s velocifl-yControlleranputY+cammml v

Figure 2: Simuiink X-Y Axis Model of Cutting Tool Sim-ulation.

Figure 3: Simulink Model of Motor.1311


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Figure 4: Simulink Model of PID Controller with Anti-windup.

The purpose of the project is to demonstrate the prac-tical applications of control design, beyond meeting a setof specifications for standard inputs such as a step or aramp signal. The project requirements are twofold: toplan a two-axis trajec tory required to obtain a cutout ofa specific shape (a rectangle and a circle), and to designand implement , hrough simulation , an effective controlscheme to meet a set of requirements.

The requirements include restrictions on the max-imum dimensional error of the cutout, on signal sat-uration (no on-off control allowed), and on the order ofthe controller (limited to fifth). Students work in teamsand are allowed to explore any viable control scheme(P I, PID, in combination with lead-lag, feed-forward,velocity feedback, etc.) tha t meets the requirements.4.1. Project Competition

Students engage in a friendly competition, where theobjective is to obtain the fastest cutout time, whilemeeting the control specifications. There is enough flex-ibility built into the implementation to encourage cre-ativity, and to develop a "feel" for the "art of controlengineering", while providing a sound test of skills ac-quired in the course. Interesting dynamics result fromthe fact tha t the course is common for students from twoengineering options: electrical engineering and com-puter engineering. The students are required to sub-mit their simulations electronically to the instructor forverification of results. The final lab sessions are devotedto group presentations. While all groups are requiredto submit a hard copy semi-formal project report, theformat of the presentation is left intentionally open, andmay incorporate overheads, or multimedia presentationof computer simulations. A question and answer periodfollows. This aspect of the project provides the studentswith their first exposure to the rigours of reporting res-ults in a coherent manner, both in a written and verbalform. This proves of value for the 4th year thesis pro-ject.

5. ConclusionsBy introducing multimedia into the classroom, the

normally passive student who habitually sits, listens,

and takes notes can be transformed into an enthusi-astic student who takes an active role in learning. Out-side of the classroom, students can access course ma-terials from anywhere a t anyt ime, both on and off cam-pus. Web-based modules are dynamic , immediate , easyto update and maintain, and easy to access for boththe students and the instructor. The networked en-vironment allows a more effective course managementthrough dissemination of information, on-line counsel-ing, and increased communication. In our course wedecided to forgo the creation of a newsgroup or a real-time chat room in favour of email only communicationswith and between students, in one-to-many and one-to-one modes. We based this decision on the fac t thatemail exchanges tend to be more task oriented, as wellas asynchronous, while the newsgroups and chat roomsare more chaotic, and may lead to unproductive social-izing. Chat rooms also require the synchronization ofschedules, which is difficult to achieve for large groupsof students. This has also been the experience of others

Formal surveys on the impact of Web-based enhance-ments to the delivery of the controls course have not yetbeen applied. Multimedia-enhanced courses at Ryersonare still a relatively new experience, although they in-clude participation in such initiatives as the InteractiveLearning Connection - University Space Network (ILC-USN), a project offering a Spacecraft Systems Designcourse in a collaboration between six universities andactively utilizing Internet and CD-ROM technologies.Ryerson Polytechnic University is well positioned totake leadership among Canadian undergraduate insti-tutions in using new media to create stimulating inter-active learning environments for students.

The vision statement of Ryerson focuses on provid-ing the best possible applied undergraduate educationthrough industry liaisons, an innovative curriculum, aninvestment in new technologies, and a Digital MediaProjects Office [7], [8], dedicated to supporting facultyin the course development. A structured framework fortechnology enabled learning is being established. Its ex-plicit goals are to focus on pedagogical strategies ratherthan specific technologies, to develop a methodology forassessing courseware, to test the framework with tech-nology enabled courses, ,and to publish the results oftesting and technology transfer. The controls coursehas been selected as one of the test beds for the frame-work, which will ensure quality of the development workand the methodologically sound course evaluation.

The anecdotal evidence gathered so far through in-formal discussions with students suggests that their en-thusiasm and interest in the course, as well as the re-tention and comprehension of the concepts, increased.The average grade in the course went from 67% in thetradi tional course delivery in 1996 to 81% in the Web-enhanced delivery in Winter, 1997. Incidentally, thedropout rate decreased to one, out of 97 students en-rolled in the course, although it is premature to make

[61.

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any generalizations without a proper longitudinal studyand prior to full implementation of all multimedia com-ponents of the course.A Faculty Course Survey, which is a standard courseevaluation tool, is applied each semester across the uni-versity to provide faculty with feedback.

Figure 5: Results of Course Evaluations.The 1997 results showed that the students percep-

tion of the difficulty and the amount of course materialdecreased, when compared with the 1996 survey results(from 4.2 to 4.0, out of 5), although there was no sig-nificant change in the actual course difficulty level orrequirements. The overall evaluation of the instructorsand the course increased slightly (from 4.3 to 4.6, out of5), consistent with our observations of increased enthu-siasm and interest in the course. The Faculty CourseSurvey results are shown in Figure 5 , where Question 8was: Rating of amount of course materia l, Ques-tion 10 was: Overall, the faculty member was effect-ive, and Question 11 was: Overall, the course wasworthwhile, with a scale 1 to 5 (Light - Heavy, andDisagree - Agree).

A review of the process required to create a techno-logy enabled course shows that initially there is a greatdeal of work involved. Estimates of the ratio of the re-quired preparation and development time in an initialoffering of the technology enabled course to the con-ventional course are in the range of 20:l [6]. Our ownestimate is more conservative, as we had previously de-veloped the conventional version of the course, and wepossess a good deal of combined expertise both in thesubject of the process control as well as in the area ofmultimedia applications. We further estimate that thisratio for subsequent course offerings should drop, butwe feel that for the primary course developers it willstill be in excess of the time required in the traditionalapproach to delivering the same course. However, therecould be a substantia l preparation time saving for a ju-nior faculty or TA involved in delivering the developedcourse.

In conclusion, we feel that the results are encour-aging, and despite the large outlay of resources, we in-tend to continue with this endeavour. It is our opinionthat technology enabled courses, while not necessarily

providing immediate savings of resources for the uni-versity, allow, when designed properly, a substantial,positive qualitative change in the way we educate en-gineering students.

AcknowledgementsThe authors would like to express their gratitude tothe Department of Electrical and Computer Engineer-

ing, Ryerson Polytechnic University, for their supportof these advanced initiatives in course development. Wewould especially like to thank Mr. Jason Naughton whospent many hours in the design and development of theServo Motor Modules.

References[l] Bill Messner, ~ Carnegie Mellon Uni-versity, Dawn Tilbury, University ofMichigan. Control Tutorials for MATLAB.http://www .engin.umic:h.edu/group/ctm/index.html[2] Control Engineering Laboratory, Ruhr-University Bochum. Virtual Control Lab.http://wvu.esr.ruhr-uni-bochum.de/VCLab/main.html131 Systems Theory Inst itu te, BraumschweigTechnical University. Pole Zero Java Applet.http://www.nst.ing.tu-bs.de/schaukasten/polezero/en-idx.html[4] Jeffrey B. Schodorf, Mark A . Yoder, James H.McClellan, Using Multimedia to Teach the Theory ofDigital Multimedia Signals, IEEE Transactions onEducation, vol. 39, no. 3, pp 336-341, August 1996.http: fwww.ece.gatech.edu research/DSP/courses/ee2200/ee2200cd/ieee1995/Revision/pap296.htm151 Craig Ulmer, Georgia Ins titute of Technology.MATLAB Pole-Zero Graphical User Interface (GUI).http://www.ee.gatech.etlu/research/DSP/courses/ee2200/ee220Ocd/ieee1995/Revision/Demos/Pez/index.htm[6] Carl Cuneo, National Director of the Network forthe Evaluation of Education and Training Technologies,Education and the Internet: A Critical View, InvitedSeminar, Ryerson Polytechnic University, March, 1998.http://socserv:!.mcmaster.ca/srnet/evnet .htm[7] Rogers Communications Centre, Ryerson Poly-technic University. http :/ www .rcc.ryerson ca[8] Digital Media Projects Office, Ryerson Polytech-nic University. http://www.rcc.ryerson.ca/dmp/

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http://www/http://wvu.esr.ruhr-uni-bochum.de/http://www.nst.ing.tu-bs.de/schaukastenhttp://fwww.ece.gatech.edu/http://www.ee.gatech.etlu/research/DSP/courseshttp://www.rcc.ryerson.ca/dmphttp://www.rcc.ryerson.ca/dmphttp://www.ee.gatech.etlu/research/DSP/courseshttp://fwww.ece.gatech.edu/http://www.nst.ing.tu-bs.de/schaukastenhttp://wvu.esr.ruhr-uni-bochum.de/http://www/

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