The direct drive motor is directly coupled by load. So it is directly affected by load and disturbances. To control the direct drive motor, a robust controller is needed.
The main feature of Variable Structure System(VSS) is that system trajectories are robust and insensitive to parameter variations and disturbances in the sliding mode. In the conventional VSS, the trajectories may have steady state error due to finite sampling time and reaching phase that system trajectories are sensitive to disturbances and parameter variations. To eliminate steady state error, an integral augmented VSS is introduced. It can be made steady state error to zero, but overshoot is inevitable and has reaching phase. In this paper, Integral augmented optimal VSS is presented to eliminate steady state error and reaching phase. The chattering input can give large noise and vibration to motor. Using saturation function, Chattering input can be made continuous to reduce noise and vibration.
