AN OPTIMAL PROPORTIONAL PLUS INTEGRAL SET-POINT CONTROLLER FOR A PERMANENT-MAGNET DC MOTOR

The aim of this paper is to design a controller for a permanent magnet de (pmdc) motor with a nonlinear load. The speed of the motor is required to vary from one set point to another. The control structure consists of a proportional type controller for inner current limiting and a proportional plus integral type controller used for outer speed regulation. Two cases are considered. The first is when the motor has a pre-specified duty cycle and in this case variable gains are calculated off-line as the solution of a constrained optimal parameter selection problem. The second case is when the required operating speeds are not pre-specified and can be changed on-line. Then, simple approximating functions are used to provide on-line estimates of these gains. A design which uses fixed gains throughout the duty cycle is also discussed. The two controller designs are tested and compared through digital computer simulation studies.