Design of mechanical stiffness switch for hydraulic quadruped robot legs inspired by equine distal forelimb

A new method, inspired by the gait of horses, for regulating the ground reaction force of a quadruped walking robot, is proposed. The method uses the mechanical stiffness switch with a dual-spring structure inspired by an equine distal forelimb. This includes the use of a low-stiffness spring activated at the moment of touchdown and a high-stiffness spring for the support phase. This method has been applied to Jinpoong, a hydraulic quadruped walking robot, and has contributed to the robot´s stable gait on uneven terrain.