A Discrete-Time Design of Time Delay Control Focus on Control Experimentations of Coordinated Motion Control of Hydraulic Excavator

In this paper a discrete-time design of continuous-time delay (TDC) is presented. The main goals are: (i) to eliminate the TDC assumption of accessibility to all the delayed derivative of the plant state variables, and (ii) to design discrete-time controllers based on approximate discrete-time models. Simulations results are given, for an articulated arm actuated with linear hydraulic motors with variable payloads, to illustrate the robustness of the proposed control design. The new proposed controller has similar results as that obtained by TDC without the use of a delay element which has become a time constant. Moreover, there is no need of measuring the joints jerk. The controller robustness is guaranteed despite the uncertainties in dynamic model caused by payload variation, imprecise modeling, etc. Other uncertainties such as friction and external disturbances are rejected in the controller automatically. Real time experimentations, with a small scale Liebherr excavator, of coordinated motion control of implements are presented.