Fuzzy Adaptive PID Speed Control of a Converter Driven DC Motor

DC motors have been widely used in many industrial and commercial applications. Speed control is a common requirement in industrial drives and commercial drives in the presence of different varying operating conditions i.e. load fluctuations, parameter uncertainty etc. Conventional controllers have not been successful for real time applications because of the drift in the plant operating conditions. Adaptive techniques best suited for these situations. The controllers have been considered without modeling of final control element. In practical applications, the effect of dynamics and nonlinearity of final control elements affects the performance of the system, so it is necessary to consider these for a dependable simulation of the drive performance. The overall system becomes non-linear due to the dynamics of converter used as final control element. In this study a new approach is being used, first the transfer function of the buck converter is obtained by considering a small linear region near the operating point, then using overall transfer function of buck converter and dc motor, the PID settings obtained. Fuzzy logic is used to update these settings on-line corresponding to the changes that may occur in system operating conditions. For more close to actual performance evaluation sinusoidal PWM controlled buck converter, used as final control element has been simulated using MATLAB. Here comparative results of PID and fuzzy adaptive PID control strategies implemented, for both types of control situations i.e. tracking speed control and the strength of approach is demonstrated.