High performance swing velocity tracking control of hydraulic excavators

The objective of the swing motion control of an industrial hydraulic excavator is to regulate the supplied flow rate to hydraulic swing motors such that the excavator follows the swing velocity command given by the human driver with a smooth acceleration/deceleration in spite of various uncertainties. Difficulties in the design of a high performance controller are: (i) the swing inertia is time-varying and unknown due to the movement of the linkage and the unknown payload in the bucket; (ii) hydraulic parameters such as bulk modulus exhibits large variations during actual operation; (iii) the system is subjected to a mild extent of uncertain nonlinearities (e.g., leakage flows of swing motors) during normal operations on a flat ground; and (iv) the system may experience a large extent of uncertain nonlinearities when operating on an uneven ground; the swing torque due to gravity forces on a slope surface is usually very large and changes quite rapidly. All these difficulties are addressed in the paper and a high performance adaptive robust control algorithm that can deliver the required performance is presented. Simulation results are presented to illustrate the proposed method.