Control Using Sliding Mode of Two Phase Stepper Motor

This paper presents a proposition of sliding mode position controller of stepper motor - two phase are commonly used in low-cost open-loop positioning control systems. However, acceleration and deceleration are limited and operating open-loop can cause the loss of steps and stalling of the motor. To overcome these inherent problems, a low-cost minor closed-loop position control system (SMC) was developed to optimize the torque output, maximize acceleration and deceleration rates and avoid the loss of steps. Two different minor closed-loop position controllers were designed and tested. Both systems employ an optical incremental encoder and both contain two feedback loops: a minor closed-loop (MCL) feeding back a step angle signal and a major closed-loop for position feedback. The first system uses a fixed advance angle MCL control whereas the second uses a fixed advance time MCL control involving a time-based interpolator. Details of these control strategies employed and the results obtained from the prototype systems are presented. The simulation of the dynamic behavior of this non-linear system, achieved under Matlab/Simulink computer package, allows us to examine the performance of this technique: improvement of the stability and the dynamic response.