Modeling of Vibroimpact Processes which Occurs in Feet Changing of the Walking Units at Viscoelastic Grounds

At research of planets walking machines could be more effective than wheeled and tracked ones. They have higher ground and shape passableness. Walking machines traction properties, in execution of ground works for example, are also higher. It is especially important in traction weight deficit, characterized by weakened gravity. In the paper executed mathematical modeling of vibro-impact processes, which appears during feet changing, and investigated influence on walking unit dynamic in weakened gravity. During modeling on feet changing walking unit has been investigated as system of bodies - frame and weightless movers (feet). As design scheme was accepted the two-feet one with vertical translational motion of frame and antiphase leg motion. The frame movement is executed by the impact of kinematic impulses created by the movers, their character determined by relative contact points motion of walking mechanisms in contact phase with ground. Modes with periodical feet motion have been modelled. Time dependencies of relative vertical motions of walking mechanisms contact points was approximated by trigonometric polynomial. In mathematical describing of grounds was used the viscoelastic model with different relations of viscous and elastic properties. Elastic force, which proportional to the ground deformation and unidirectional viscous friction force, which proportional to deformation speed, were introduced. The modeling results have shown, in feet changing occurs their oscillations at the ground. The oscillations are accompanied by support reactions alteration and their maximum values could be bigger than static by few times. The effect occurs at different grounds. This property can be used for implementation of increased traction forces in individual cycle phases. At increasing of movement speed the amplitude of support reactions changing is rising. In weakened gravity conditions that could result in transformation of static stable walking to running already at low velocities. The results can be demand in walking robots development, designed to planet surface investigation.