Adaptive Gait for Large Rough Terrain of a Leg-wheel Robot (2nd Report, Gait for an Upward Step)

Abstract

A leg-wheel robot has mechanically separated four legs and two wheels, and it performs high mobility and stability on rough terrains. The adaptive gait for large rough terrains of the leg-wheel robot is composed of three gait strategies. In this paper, the gait for an upward step, which is one part of the adaptive gait, is described. The proposed method is evaluated by simulations and experiments. The point of the flow of the gait for an upward step is described. When the robot reaches an upward step, it does not come to advance easily because it can not go up the upward step by the normal gait. At this time, the difference between actual wheel angles and desired wheel angles grows. Starting point of the step is detected by using this information. The system stops the body, and prepares for going up the step. In the preparation, the robot changes footsteps in order to set all legs to starting points of their work space. After that, the robot can raise the body on the step supported by all legs and wheels. The purpose of supporting using all legs and wheels is to enhance stability and to reduce energy. To raise the body, the following items are needed : I. Acquisition of target rise height of the body. 2. Correspondence to difference between target and actual height.