Abstract
In this paper, we first derive a dynamical model of a power shovel which consists of a boom, an arm, and a backet, each controlled by a hydraulic cylinder. One of the important task of the power shovel is to dig a sloped ground in such a way that the surface of the slope is as flat as possible in spite of the unknown force disturbance from the slope. If working conditions (angle of the slope, length of the slope, speed of the backet, etc.) are given, the rotation angles and the angular velocities of the boom, the arm, and the backet and the oil flow to each hydraulic cylinder can be calculated on the basis of the dynamical model.
Our control scheme is as follows: the calculated input oil flow signal to each hydraulic cylinder is given in the feedforward form, and the actual rotation angles and the angular velocities of the boom, the arm, and the backet are compared to the calculated values. The differences of the angles and the angular velocities are controlled by PID controllers in the feedback form.
Some simulation results are presented, which prove that our feedforward plus PID feedback control scheme works well in spite of the force disturbance from the slope.
