The use of fuzzy logic for closed loop control is compared to the more traditional approaches of zero-pole placement in the z-plane and the choice of PID (proportional, integral, differential) parameters. A common type of positioning system is used as an example to illustrate these different approaches and to allow practical comparisons. Results of a simulation study of the model system, using specific implementations of the three control techniques, show that fuzzy logic can be used to achieve a degree of compensation that is nearly as good as that achieved by more conventional techniques. The fuzzy logic approach requires more code, hence, more power on the part of the microcontroller, but it does not require that the designer have a knowledge of feedback control theory. Because fuzzy logic is a straightforward approach, based upon practical knowledge of the system to be controlled, its use has some advantages over the other approaches if an analytic model of the system is difficult to construct. Certain demands are placed upon the microcontroller in all three cases, and these are discussed here in some detail. Two popular microcontrollers, the MC68HC16 and MC68332, are examined to explore their individually unique features that make them particularly suitable for one or the other of the control schemes studied.
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