A New Technique for Controlling Hybrid Stepper Motor through Modified Pid Controller

Due to the development of digital control systems, hybrid stepper motors became more attractive to be used in robotics and computer numerical control machines where they have to perform high-precision positioning operations without any feedback sensor. However, at open loop control (especially at higher stepping rate), the speed response of the stepper motor suffer from large overshoot, oscillatory response and long settling time. Therefore, a closed loop control system essentially required for a good precise operation performance. However, due to the non-linear characteristics and the resonance problem of the hybrid stepper motor, it is difficult to settle the classical control systems with this type of motor. Moreover, the use of discrete pulses to drive the hybrid stepper motor in half stepping mode leads to jerky and noisy movements at high and low stepping rate respectively. The objective of the present paper is to use the PID control system to enhance the performance of the open loop control system to control the speed of the hybrid stepper motor for a given reference input. Also, a microstepping technique, which consists of sine and cosine waveforms, is also used to drive the hybrid stepper motor instead of discrete pulses. Therefore, a simulation program is constructed using MATLAB software version 7.7 to simulate the hybrid stepper motor performance in open loop, classical PID and modified PID control systems. Results show that the open loop control system suffers from oscillatory response at half stepping mode and form from large overshoot and long settling time at microstepping mode. Also, the classical PID control system didn’t give consistent results. And, the proposed control algorithm gives a better performance than that of the open loop even when the system is subjected to a sudden load disturbance up to 41% and working at high motor speed. Index Term-Hybrid stepper motor, Microstepping, Half stepping, Open loop, PID, Phase plane.