FPGA-based fuzzy sliding-mode control for a linear induction motor drive

A field-programmable gate array (FPGA)-based fuzzy sliding-mode controller, which combines both the merits of fuzzy control and sliding-mode control, is proposed to control the mover position of a linear induction motor (LIM) drive to compensate the uncertainties including the frictional force. First, the dynamic model of an indirect field-oriented LIM drive is derived. Next, a sliding-mode controller with an integral-operation switching surface is designed. The uncertainties are lumped in the sliding-mode controller, and the upper bound of the lumped uncertainty is necessary in the design of the sliding-mode controller. However, the upper bound of the lumped uncertainty is difficult to obtain in advance in practical applications. Therefore, a fuzzy sliding-mode controller is investigated, in which a simple fuzzy inference mechanism is utilised to estimate the upper bound of the lumped uncertainty. With the fuzzy sliding-mode controller, the mover of the LIM drive possesses the advantages of a good transient control performance and robustness to uncertainties in the tracking of periodic reference trajectories. A FPGA chip is adopted to implement the indirect field-oriented mechanism and the developed control algorithms for possible low-cost and high-performance industrial applications. The effectiveness of the proposed control scheme is verified by experimental results.