Terrain mapping with a pan and tilt stereo camera for locomotion on a quadruped robot

Legged robots are expected to have superior mobility on rough terrain than wheeled robots. The main reason is that legged locomotion is more adaptable to a wide range of terrain types as the robot can decompose its path into a sequence of footholds and can use different locomotion strategies. In order to accomplish most of the locomotion tasks the robot requires high level control (i.e., to adjust the locomotion parameters and to choose optimal footholds) which depends on real-time localization and accurate terrain mapping. In this paper, we propose a SLAM solution using a pan and tilt stereo camera mounted on an hydraulically actuated quadruped robot that builds a map and keeps track of the robot’s position. Since the computation needs to be carried out on board and the robot is subject to considerable motion during its locomotion (regular vibrations, impacts or slippages), we developed a dedicated implementation based on fast stereo depth computation, GPU based map building and mechanical motion compensation. Combined with a foothold planning framework presented in our previous work [1], this localization and mapping ability allows to perform locomotion in a fully planned manner. Successful results of foothold planning with our quadruped robot show the effectiveness of our method.