Sliding‐mode position control of medium‐stroke voice coil motor based on system identification observer

This study presents the performance improvement in the position control of a medium‐stroke voice coil motor (VCM) using a sliding‐mode controller (SMC) with a system identification observer (SIO). The proposed VCM is developed with a full stroke of 24 mm, and its non‐linear electro‐magneto‐mechanical characteristics are analysed by the three‐dimensional finite element method. A least‐squares‐based SIO is introduced into the VCM control system prior to the position regulation of the SMC in order to achieve a shorter rise time of 29 ms and a smaller steady‐state error of <±2 μm under a square‐wave excitation of 20 mm amplitude and 0.5 Hz frequency. An experimental verification between the SMC and a traditional proportion–integral–differential controller is carried out. The results demonstrate improved dynamic and static tracking responses in the SMC under load‐free, frequency‐varying operations.