Trajectory Generation and Compensation for External Forces with a Leg-wheeled Robot Designed for Human Passengers

Abstract

In this paper, we propose a method to generate a reference trajectory of a center of gravity (COG) and a zero moment point (ZMP) for hybrid locomotion, walking and wheeled locomotion. It extends the method to generate a reference ZMP trajectory with a linear inverted pendulum model (LIPM) for walking. By this method, an integrated stabilizing control for locomotion while switching walking and wheeled locomotion is achieved. It means that walking and wheeled locomotion are treated in a unified manner. It enables to generate hybrid locomotion easily and simply. In order to locomote with a passenger, a robot should be controlled by considering external force from passenger's weight and movement. We present a method to compensate such external forces by using a force/torque sensor between a seat and a robot. With the proposed methods stabilizing and compensating external forces, we verified that the real robot can locomote by a hybrid way, walking and wheeled locomotion, and the robot with a passenger can locomote by wheels.