Analysis, Design, and Testing of a Position Servo Utilizing a Stepper Motor

The development of a position control system using a stepper or incremental motor is described. The advantages of this type of prime mover are discussed, and a technique of integrating the stepper motor into the system is analyzed. The output signal from the error detector used in the system comes from a sampler and zero-order hold circuit. This signal controls a gate which either allows or inhibits a pulse train to drive the stepper motor. The load on the motor is an underdamped second-order system. The stepper motor output position and the reference input determine the error. The analysis includes a stability investigation using the describing-function method and a computer simulation to determine the dynamic performance of the system. The effects of noise in the system are also investigated on the computer. The equipment used to mechanize the control system is described, and results of experimentol work to determine the actual performance of the system are given.