Permanent magnet (PM) motors find many industrial control applications because of their merits of high efficiency, simple mechanism and low cost. In most of the cases, the plant model is either inaccurately defined or the parameters are prone to variations. The proposed work deals with the speed control of PMDC motor using a classical PID controller. The problem of variation in motor parameters and their effect on the closed loop performance is discussed. The controller must adapt to the motor parameter variations and maintain the performance over the operational life of the motor. Also the controller must provide robustness against the external disturbances. A classical PID controller design lacks the robustness requirements and hence, this paper presents an H∞ optimization approach towards the selection of PID controller gains to provide the desired performance. Different performance goals are selected for the closed loop system. A tuneable PID controller is selected for the control loop and its gain parameters are tuned to minimize the performance costs. The performance goals are transformed into minimization functions and H∞ norm of each of these functions is minimized to achieve the final result. A commercial motor Maxon RE 35 is selected and its parameters are used for the modeling and simulations. The behavior of the H∞ norm minimized PID controller is analyzed for different input commands and tracking performance also studied.
Volume 11 | Issue 5