Caterpillar-inspired crawling robot on a stick using active-release and passive-grip elastic legs

This paper presents a lightweight caterpillar-inspired soft-bodied robot that produces crawling locomotion on a stick. The significant features are passive-grip/active-release opposable legs and dual elastic arch structure to couple the segment contraction and the leg opening. These actuations are driven by a shape memory alloy (SMA) coil attached along the body axis. The mechanical design allows the robot to hold the unstable substrate without energy consumption. We find that adequate activation time lag between the legs/segments exists but the system is not sensitive to the parameter changes thanks to the softness of the body. The robot can build very cheap (less than 30 US dollars) to 3d-print using hard and rubber-like materials together, which doesn't require any assembly labor to build the body.