Proceedings of 2005 CACS Automatic Control ConferenceTainan, Taiwan, Nov 18-19, 2005<strong>digital</strong> feedback <strong>control</strong>ler is given to students suchthat they can modify the <strong>control</strong>ler parameters andeven the <strong>control</strong>ler structure [6] to see if the responsescoincide <strong>with</strong> the theoretical predictions. If not,double check of the software codes and theories canmake them more familiar <strong>with</strong> problem-solvingtechniques. Experimental results which compare theperformances of the servo <strong>control</strong> of dc motors <strong>with</strong>and <strong>with</strong>out the anti-windup function are shown infigure 5. The robustness of the <strong>digital</strong> temperature<strong>control</strong>ler is shown via experimental results in figure 6by changing the amount of water in the water tank.Figure 5. The experimental results of <strong>digital</strong> servo<strong>control</strong> of DC motors <strong>with</strong> and <strong>with</strong>out anti-windupfunction4. ConclusionsA <strong>low</strong> <strong>cost</strong> <strong>educational</strong> <strong>platform</strong> is devised in thispaper. It can be constructed for servo <strong>control</strong> of dcmotors and temperature <strong>control</strong> of a water tank forless than USD$ 50. Two experiments are devised tohelp students become familiar <strong>with</strong> the necessary<strong>control</strong> theories and the corresponding softwareimplementation for the servo <strong>control</strong> of a dc motorand temperature <strong>control</strong> of a water tank. This canhelp encourage students to make their own<strong>educational</strong> <strong>platform</strong> and learn to solve by themselvesmore practical <strong>digital</strong> <strong>control</strong> problems. To make the<strong>educational</strong> <strong>platform</strong> more versatile, the USB portshould be used to increase the communication speedbetween the <strong>educational</strong> <strong>platform</strong> and the personalcomputer. This may be done <strong>with</strong> the help of theUSB interface device [11]. Moreover, the <strong>digital</strong>signal <strong>control</strong>ler (dsPIC) provided by the MicrochipTechnology Inc. is another affordable choice ofmicro-<strong>control</strong>ler for its fast computational speed andversatility. It is also easy to setup the developmentenvironment for the <strong>digital</strong> signal <strong>control</strong>ler (dsPIC)<strong>with</strong>out too much money.Figure 6. Robustness analysis of the <strong>digital</strong> PIDtemperature <strong>control</strong>ler <strong>with</strong> and <strong>with</strong>out anti-windupfunctionSince tuning of PID <strong>control</strong>ler parameters may betedious in practice, techniques in auto-tuning of<strong>control</strong>ler parameters [2, 4] are introduced to studentsafter they successfully apply theories to design PID<strong>control</strong>lers in both the problems. Because of thecomputational complexity, the self-tuning adaptivefeedback <strong>control</strong>ler for servo <strong>control</strong> of dc motors byusing recursive least square (RLS) estimation can onlybe demonstrated in our dSPACE real time <strong>control</strong>environment if the order of the reference model isgreater than or equal to 2. The student can stillimplement a convergent RLS algorithm on the<strong>educational</strong> <strong>platform</strong> if the sampling frequency is nottoo high and a reference model of order 1 is used.Figure 7 shows the experimental results of asuccessful self-tuning adaptive feedback <strong>control</strong>ler,whose reference model is of order 1. On the otherhand, the algorithm described in [5] for on-lineidentification of system parameters and auto-tuning ofPID <strong>control</strong>ler parameters can be successfullyimplemented in the <strong>educational</strong> <strong>platform</strong>, because thedynamics for heat transfer in the temperature <strong>control</strong>of a water tank is s<strong>low</strong>.Figure 7. The experimental results of a successfulself-tuning adaptive feedback <strong>control</strong>ler, whosereference model is of order 15. References[1] D. S. Bernstein, “Enhancing undergraduate<strong>control</strong> education,” IEEE Control SystemsMagazine, pp. 40-43, October 1999.[2] Y.-C. Chen and J. M. Naughton, “Anundergraduate laboratory <strong>platform</strong> for <strong>control</strong>system design, simulation, and implementation,”IEEE Control Systems Magazine, pp. 12-20,June 2000.[3] G. F. Franklin, J. D. Powell, and A.Mami-Naeini, Feedback <strong>control</strong> of Dynamic<strong>systems</strong>, 4 th edition, , chapter 2, Prentice-Hall,Inc., 2002.
[4] K. J. Åström and B. Wittenmark,Computer-Controlled Systems: Theory andDesign, 3 rd edition, Prentice-Hall, Inc., 1997.[5] K. J. Åström and T. Hägglund, ”Automatictuning of simple regulators <strong>with</strong> specificationson phase and amplitude margins,” Automatica,Vol. 20, No. 5, pp. 645-651, 1984.[6] R. Kelly and J. Moreno, “<strong>Learning</strong> PIDstructures in an introductory course of automatic<strong>control</strong>,” IEEE Transactions on Edcuation, Vol.44, No. 4, pp. 373-376, November 2001.[7] C. Bohn and D. P. Atherton, “An analysispackage comparing PID anti-windup strategies”IEEE Control Systems Magazine, pp. 34-40,April 1995.[8] E. Eitelberg, “A regulating and tracking PI(D)<strong>control</strong>ler,” International Journal of Control,Vol. 45, No. 1, pp. 91-95, 1987.[9] J. C. Basilio and M. V. Moreira, “State-spaceparameter identification in a second <strong>control</strong>laboratory,” IEEE Transactions on Edcuation,Vol. 47, No. 2, pp. 204-210, May 2004.[10] Microchip Technology, Inc., “Servo Control of aDC-Brush Motor,” application note AN532,1997.[11] Royal Philips Electronics, PDIUSBD12: USBinterface device <strong>with</strong> parallel bus,www.semiconductors.philips.com/pip/PDIUSBD12D.html.AcknowledgementsThe authors would like to thank National ScienceCouncil for its financial support under grantNSC-94-2613-E262-004.Proceedings of 2005 CACS Automatic Control ConferenceTainan, Taiwan, Nov 18-19, 2005
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