Force Control in Locomotion of Legged Vehicles over Rigid and Soft Surfaces

Abstract

The control system of the hexapod walking vehicle, designed at the Institute for Mechanics at Moscow State University and at the Institute for Problems of Information Transmis sion at the USSR Academy of Sciences, is extended to effect the control of foot-contact forces and locomotion in soft soil. The previously developed positional control system enables the computation of commanded motion of the vehicle legs and positional feedback to track this commanded motion. Force feedback is added to the control system, in addition to computation of commanded forces and leg position correc tions for leg sinkage during soft soil locomotion. Such an elaborate control system has made it possible to solve the problems of controlling the distribution of vertical foot force components in locomotion over a rigid surface and of foot-force vectors in locomotion between planes forming a dihedral angle. A number of algorithms are proposed to control vertical force components (loads on legs) and leg sink age in locomotion in elastic and consolidating soils. In the latter case, which corresponds to most natural soils, the bear ing properties of the surface are considered a priori unknown. The results of the experimental implementation of the algorithms are presented.