Sliding-mode position controller for linear permanent magnet brushless DC servo motors

In this paper, we evaluate the performance of a robust sliding mode controller (SMC) for high performance position control of a linear brushless direct current motor (LBLDCM). Conventional SMC with switching control action introduces chattering and hence a boundary layer around the switching surface is introduced to smoothen the switching control effect. To overcome the drawbacks of steady state errors with PD-type of switching surface as well as overshoot in PID-type of switching surface, a modified PID-type of switching surface is proposed. The performance of the proposed controller is evaluated by applying it to drive a 300mm stroke length, DX20-C4 LBLDCM. The controller is implemented on a general-purpose DSP DS1104 controller board from dSPACE. Experimental test results obtained demonstrate the improved performance of the proposed SMC controller.