Design of Dissipative and Stable Assist Robots

This paper presents a methodology for design of dissipative assist robots with proven stability during set-point control. A dissipative assist robot is defined as one where the actuators continuously dissipate energy from the robot until the robot reaches the desired set point. We have discussed in this paper that, under well known control laws, it is hard to characterize dissipativity of a general assist robot. However, by appropriately designing the robot through inertia redistribution, the dynamic equations can be modified so that the control laws can now be proven to be both dissipative and stable under set-point control. The proposed method is demonstrated through simulation of a three-link planar manipulator used as an assist robot to modify human functional movements in a vertical plane.