June 22, 2008
June 22, 2008
June 25, 2008
Computers in Education
13.45.1 - 13.45.14
A Graphical User Interface (GUI) for a Unified Approach for Continuous-Time Compensator Design
As an alternative to the numerous distinct controller design algorithms in classical control textbooks, a simple unified design approach, which is independent of the form of the linear system information, was developed in previous work for all standard classical compensators. This approach is based on a simple root locus design procedure for a proportional-derivative (PD) compensator. From this procedure, design procedures for unified notation lead, proportional-integral (PI), proportional-integral–derivative (PID), and PI-lead compensator were developed. With this proposed approach, students can concentrate on the larger control system design issues, such as compensator selection and closed-loop performance, rather than the intricacies of a particular design procedure.
Once students learn the unified design process discussed above, it is important that they get an opportunity to apply it to design and laboratory projects. Most real life examples require design iterations. The Graphical User Interface (GUI) developed in this paper not only makes this feasible, but also makes this an excellent learning opportunity. The authors have implemented the unified compensator design procedure as a GUI in MATLAB. The GUI presents the user with both root locus and Bode information. Either domain can be used for design. The effect of the design on both domains can be seen instantaneously. The GUI also provides the user with the closed-loop step and Bode response as well. Design specifications in the time and frequency domain are easily verified.
In controls education today, there seems to be gap between the theory taught in the typical undergraduate classroom and the skills required for practical application of control systems. One obvious reason for this is the lack of undergraduate control system laboratories. The control systems community has recognized this need.1,2 In many departments around the world, undergraduate control system laboratories are being developed.3,4 A less obvious reason for this gap is the “cookbook” approach to compensator design found in typical classical control textbooks.5,6,7 For example, a quick comparison reveals significant differences in the procedures for root locus lead design and root locus Proportional-Integral (PI) design. Even more importantly, there are significant differences in the procedures for lead compensator design using root locus techniques and Bode techniques. Furthermore, for even simple systems, these design procedures may yield poor results.8 Therefore, students end up concentrating on the different “recipes” that may or may not yield satisfactory results, and, consequently, tend to miss the “big picture”.
In previous work, design methods were developed that permit students to apply a simple, unified design approach for six standard compensators (Proportional-Derivative (PD), lead, Proportional-Integral (PI), lag, Proportional-Integral-Derivative (PID), and PI-lead independent of the form of the system information.9,10 In root locus design, the computational procedures are
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