J Intell Robot Syst (2007) 48:333–356 DOI 10.1007/s10846-006-9084-y Trajectory Tracking with Parallel Robots Using Low Chattering, Fuzzy Sliding Mode Controller Zhen Qi · John E. McInroy · Farhad Jafari Received: 26 June 2006 / Accepted: 29 September 2006 / Published online: 8 December 2006 © Springer Science + Business Media B.V. 2006 Abstract This paper proposes a trajectory tracking scheme which belongs to the sliding mode control (SMC) for the 4-degree-of-freedom (DOF) parallel robots. Two fuzzy logic systems (FLS) are first put forward to replace the constant switching control gain and the width of the boundary layer. The fuzzy adaptive supervisory controller (FASC) is combined with the fuzzy sliding mode control (FSMC) to further reduce the chattering. The design is simple and less fuzzy rules are required. The simulation results demonstrate that the chattering of the SMC is reduced greatly and the parallel robot realizes the trajectory tracking with very good robustness to the parameter uncertainties and external disturbances. Key words external disturbance · fuzzy adaptive supervisory controller · fuzzy logic systems · parallel robot · sliding mode control · trajectory tracking 1 Introduction Trajectory tracking with parallel robots has been an important research topic, and many control approaches have been proposed. In [1–3], predictive functional control, Z. Qi · J. E. McInroy (B ) Department of Electrical and Computer Engineering, University of Wyoming, Laramie, WY 82071, USA e-mail: mcinroy@uwyo.edu Z. Qi e-mail: swamqi@uwyo.edu F. Jafari Department of Mathematics, University of Wyoming, Laramie, WY 82071, USA e-mail: fjafari@uwyo.edu