DC-motor speed control by PIC-based digital PID-controller

Abstract DC motor speed control was carried out by preparing a PIC based PID controller. The H-bridge motor driver was driven by the sign/magnitude PWM signal at frequency of 240Hz. The step responses of the motor speed (ω) were systematically measured to obtain optimum PID parameters. Practical steps to determine the parameters were, first to estimate the values by the Ziegler-Nichols method in medium speed region and second to tune the values in detail step by step. The PID controller exhibited notable improvements of the time constant at rising edge (e.g. 0.5 to 0.2 s) and excellent control performance to minimize the steady-state error (e.g. between −0.5 and 0.2%) even the ω vs duty cycle curve was strongly nonlinear in discontinuous conduction mode of PWM at 240Hz.