Résumé
This paper deals with the development of a new time-varying adaptive feedforward sliding mode control (SMC). The proposed controller is designed based on the original SMC by adding a feedforward term, which can be adaptive, in order to estimate the dynamic parameters. The main contribution of this study is a time-varying adaptation gain, which is proposed to efficiently identify these parameters. The objective is then to outperform the original SMC scheme. The proposed controller has been designed and applied to parallel kinematic manipulators (PKMs). It is validated through numerical simulation for different operating conditions on the VELOCE PKM. The obtained simulation results show the efficiency of the proposed controller in terms of tracking performances and robustness, with improvements up to 55% with respect to another adaptive controller (Adaptive Feedforward PD: AFFPD).