Development of the lightweight hydraulic quadruped robot — MiniHyQ

This paper presents the development of the lightweight hydraulic quadruped robot MiniHyQ. To the authors' best knowledge, MiniHyQ is the lightest and smallest hydraulic quadruped robot that has been built so far. MiniHyQ is a fully torque controlled robot. It has reconfigurable leg configurations. It has wide joint range of motion and an onboard compact power pack. The robot has almost the same leg length as the previous robot (HyQ [1], built by our group), but its link segment lengths are 15% less in flex configuration, due to the special isogram knee joint mechanism. Its weight is only 35kg (24kg with an offboard pump unit), which makes it portable by one person. To achieve this lightweight, miniature hydraulic actuators were carefully selected, allowing us to reduce the required pump size inside the torso. By using a hydraulic rotary actuator for the hip and linear actuators with isogram mechanism for the knee joint, a wider range of motion is achieved, allowing a self-righting motion. For the design validation and hardware testing, series of experiments are conducted on MiniHyQ single leg.