An adaptable cat-inspired leg design with frequency-amplitude coupling

In this work, a novel, adaptable robotic leg design capable of varying stride length w.r.t. frequency of motion is presented. The leg model which is inspired from domestic cats, is comprised of a four bar linkage mechanism with an actuator at hip joint rotating in only one direction. Furthermore, it consists of an elastic link attached to the motor that moves at a controlled uniform speed. This link has a direct effect on the foot curve and responds to the changes of velocity autonomously; the faster the speed, the longer the link gets. This property in turn imparts adaptability to the leg. The adaptability of the leg along with the architecture and actuation method can facilitate the control problem and the development of energy efficient and fast running robots. In this paper, the leg mechanism is described and a prototype of a single leg has been developed. The results of running and experiments validate the effectiveness of the mechanism. As results of the experiments, running at a wide range of speeds and autonomously changing stride length w.r.t. running velocity are realized by the proposed leg.