Throwing motion with instantaneous force using a variable viscoelastic joint manipulator

This article focuses on developing a pneumatic artificial muscle as a variable elastic device and a magnetorheological fluid brake as a variable viscosity device and a variable friction device. We executed a throwing motion using a 2-degree-of-freedom manipulator as a case study of the control of dynamic motion. To investigate the throwing motion, we proposed the spring model of the manipulator, which includes a variable viscoelastic joint. Next, the manipulator and the spring model were extended to 2 degrees of freedom. In addition, the spring model was verified by comparing the simulation and experimental results. The simulation results reproduced the experimental results. Furthermore, we maximized the velocity of the end effector during the throwing motion by searching for adequate drive timing of the second joint in the simulation. In the simulation, hand speed was improved by releasing the second joint on the basis of the angular acceleration of the first joint. Finally, the simulation results were reproduced experimentally under the same conditions.