Motion control of instantaneous force for an artificial muscle manipulator with variable rheological joint

Highly rigid actuators such as a geared motor or hydraulic actuator 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 with instantaneous force-as in a jump or throw-via variable rheological characteristics. We developed a one-degree-of-freedom manipulator with a variable rheological joint using a straight-fiber-type artificial muscle and a magnetorheological (MR) brake. Then, we created a nonlinear dynamic characteristics model of this manipulator and proposed a method for generating instantaneous force. Furthermore, we validated the proposed method by experiment and simulation. The model reproduced the manipulator system characteristics, and the dead and rise times decreased compared with the conventional method. Furthermore, we controlled the manipulator arm motion by controlling the MR brake both experimentally and via simulation. The results were quite satisfactory.