Robust Control of Robot Manipulators Using Inclusive and Enhanced Time Delay Control

Thanks to its simplicity and robustness, time delay control (TDC) has been recognized as a simple and yet effective alternative to robot model-based controls and/or intelligent controls. An inclusive and enhanced formulation of TDC for robust control of robot manipulators is presented in this paper. The proposed formulation consists of three intuitive terms: 1) time delay estimation (TDE), inherited from the original TDC, for cancellation of mostly continuous nonlinearities; 2) nonlinear desired error dynamics (DED) (i.e., a "mass"-"nonlinear damper"-"nonlinear spring" system) injection term; and 3) a TDE error correction term based on a nonlinear sliding surface. The proposed TDC formulation has an inclusive structure. Depending on the gain/parameter set chosen, the proposed formulation can become Hsia's formulation, Jin's formulations including a type of terminal sliding mode control (SMC), an SMC with a switching signum function, or a novel enhanced formulation. Experimental comparisons were made using a programmable universal manipulator for assembly-type robot manipulator with various parameter sets for the proposed control. Among them, the highest position tracking accuracy was obtained by using a terminal sliding DED with a terminal sliding correction term.