Swing-Down Control of a Rings Gymnastic Robot

In this paper, we study the swing-down control of a rings gymnastic robot, which is a 3-link planar robot moving in a vertical plane with only the last joint being actuated. The control objective is to swing the rings gymnastic robot from the DUU (Down–Up–Up) equilibrium point to the DDD (Down–Down– Down) equilibrium point and stabilize it around the latter. We present an SD (sinusoidal-derivative) controller, which is linear feedback of sinusoidal function of the angle of the actuated joint and linear feedback of its angular velocity. We analyze globally the motion of the rings gymnastic robot under the proposed controller, and provide a sufficient condition for achieving the control goal. We study how to find control gains to achieve an exerllent control performance, and verify the effectiveness of the proposed control via simulation.