An optional passive/active transformable wheel-legged mobility concept for search and rescue robots

A novel transformable wheel-legged robot, namely Land Devil Ray (LDR), is proposed for search and rescue mission in complex terrains. Inspired from spatial folding mechanism and metamorphic mechanism, a multi-four-bar linkage transformable wheel-legged locomotion mechanism is proposed for LDR, which can transform from circle-wheeled mobility to wheel-legged mobility, or vice versa, for adaptability of different terrains. Aimed to minimize the robot actuators, the wheel-legged transformation is designed to be triggered passively when contacting the obstacles, or be actively driven without extra actuator by active triggering mechanism. The parameters of wheel-legged structure are optimized as well for an optimal transformation success rate and better obstacle-negotiation capability. A prototype of LDR robot is conducted, and its experiment results show that the proposed robot integrates the advantages of both wheeled and legged mobility, and has excellent performance in maneuverability, stability, maximum obstacle-negotiation height and mode switch process, such as transformation ratio as 1.88, transformation success rate as 100%, and ability to over obstacles 2.8 times as tall as its wheel radius. Lessons learned from the proposed robotic mobility and its results have general applicability to search / rescue robots, and other types of mobile robots as well.