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 threedimensional 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. & The Institution of Engineering and Technology 2015.