LOCAL REFLEX GENERATION FOR OBSTACLE NEGOTIATION IN QUADRUPEDAL LOCOMOTION

Legged robots that dynamically locomote through rough terrain need to constantly handle unpredicted collisions (e.g. foot stumbling due to an obstacle) due to the unstructured nature of the environment. If these disturbances are strong enough they can cause errors in the robot’s trunk that are difficult to control with a common feedback-based controller, imposing a serious risk to the overall system stability. The impulsive nature of such disturbances demands a very short reaction time, especially in case of dynamic gaits (trot, gallop, etc.). A quick reaction becomes increasingly crucial when the robot is deprived of reliable visual feedback (e.g. smoky areas or thick vegetation) or when an accurate map of the environment is not available. In this paper we propose a local elevator reflex which enables the robot to reactively overcome high obstacles. The reflex is implemented and experimentally evaluated on the hydraulic quadruped HyQ. We demonstrate the feasibility and effectiveness of our approach showing that the robot is able to step over a platform of 11cm height (14% of the leg length) without prior knowledge of the terrain.