Speed and Acceleration Control for a Two Wheel-Leg Robot Based on Distributed Dynamic Model and Whole-Body Control

Abstract

The control technique for generating whole body motions on wheel-leg robot for dynamic locomotion and balance is a challenging topic. In this paper, a whole body dynamic model is built. It consisted by the torso dynamic model, the wheel-leg dynamic model and the contact force constraint between the wheels and the ground. A whole body control frame is proposed which composed by a torso motion controller, two torque solvers, a slippage predictor and an online trajectory generator. The torso controller plans the coupling wrenches between wheel-legs and torso. The torque solvers for every wheel-leg compute joint torques based on the coupling wrenches computed from the torso controller synchronously. The contact forces can be calculated by the slippage predictor based on the joint torques, then a boolean signal will be transmitted to the online trajectories generator to indicate whether the friction cone constraint will be broken. The online trajectory generator can plan reasonable acceleration trajectory with different boolean signals. The efficiency of this control frame is illustrated by several simulations in virtual simulation environment.