In the controller (46), the switching term was designed based on the conventional SMC, which provides big chattering. In addition, the sliding gain was selected based on the bounded value , which might not be obtained in advance in practical applications. To eliminate the chattering and to relax the assumption, an adaptive dual-layer supper-twisting algorithm [29], [30] is employed in this paper. Therefore, the switching term in (45) can be re-designed as