Abstract
We have been studying an interior permanent magnet linear actuator as an artificial muscle. This actuator has long stroke, high response and large thrust using interior permanent magnets effectively and can emulate the spring-dumper characteristics of a human muscle by quick control of the output force, i.e. impedance control. In this paper, we develop a monopedal robot possessing bi- and mono-articular muscles implemented by electromagnetic linear actuators. Thanks to the biarticular muscle, the stiffness ellipse at the endpoint (foot) of the robot can be changed. The bouncing direction of the robot we developed can be controlled by adjusting the stiffness ellipse when the robot touches down to the ground. We also develop a small size current control circuit for the electromagnetic linear actuator to downsize a control system.