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A b s t r a c tIn this paper we propose a new digital controller for a position servo system. 'The controller is an observerbased controller which takes advantage of the twotime-scale structure of the motor. Only some knowledge, of the mechanical and electrical time constants, and not a detailed mathematical model or exact parameter values, are required t o implement the controller and that the closed loop system performance specifications can be met reasonably well under the lack of detailed modeling. The transient mismatch phenomenon which occurs for this class of designs is fully discussed and a sufficient condition is obtained to guarantee that such a mismatch will not occur. 1NTR.ODUCTIONPosition servo systems have been used extensively throughout the industry [l], [2]. A position servo system is a feedback system whose primary objective is to keep the angular displacement of the shaft, or more often a mechanical load driven by the motor, within an acceptable range of a given set point. PI, PD, and PID controllers have been the most popular controllers for this class of applications. Simplicity of the hardware and the tuning procedures have been among the key factors for making these controllers popular.To cope with the problem of parameter variation and model uncertainty, several authors have proposed fuzzy logic controllers for the position servo systems and have drawn comparison between the performance of these controllers and the more traditional PI, PD, and PID controllers [3],[4]. It has been claimed that a fuzzy controller can out-perform a digitally tuned PID controller [4].In this paper we propose yet another controller for the position servo system. The proposed controller is a 'Department of Engineering t Department of Electrical Engineering Technology two-timescale observer based controller and is based on the theory of singular perturbation [5]. In comparison to the PID and fuzzy controllers, we believe that the new controller is advantageous with respect to the following considerations.1. The proposed controller operates on the basis of the full state variables and not just the position measurements as is the case for the PID and fuzzy controllers. However, only one additional potentiometer is needed to acquire the armature current. Since state variables are reconstructed by the use of the observer, accuracy of these measurements are not as crucial in comparison to other design methods. Reconstructing the full set of the states provides additional flexibility in monitoring armature current and angular velocity without requiring a tachometer.2. The problem of high dimensionality associated with the use of the observer is resolved by incorporating the two-timescale structure that is inherited in the system. That is, while the use of the observer increases the dimension of the system from three to six, exploiting the two-timescale structure of the system allows the system to be separated into two lower dimensional subsystems, one with the dimension of four and one with the dimension of two. Thus, ...

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This paper describes a PC-based universal fuzzy logic control (FLC) and development system. Programs are designed using a C/C++ development environment to enable FLC control engineers to tackle various phases of the FLC control system design cycle. Major software and hardware components of the systems are described A case study describing the developmelit of a FLC-based dc motor speed controller is presented. Experimental results are discussed.