Variable impedance control with an artificial muscle manipulator using instantaneous force and MR brake

Highly rigid actuators such as geared motors or hydraulic actuators are widely used in industrial robots. To obtain high-speed motion, it is necessary to increase the actuator output as the robot weight increases. In contrast, humans perform motions using instantaneous force, such as jumping or throwing, via variable stiffness characteristics. We have developed a one-degree-of-freedom manipulator with a variable rheological joint using a straight-fiber-type artificial muscle and a magnetorheological (MR) brake. With the generation of instantaneous force, the dead and rise times decreased compared to the conventional method. After the generation of an arbitrary instantaneous force, we were able to control the robot's arm position by applying an equilibrium force on the joint. Furthermore, we were able to control the vibrations of the arm by controlling the MR brake using an evaluation function.