Posture Control of A 3-link Acrobat Robot By Torque Input

The Realization of An Out-of-Phase Motion by Using A Backstepping Method

Abstract

In this paper, we discuss an aerial posture control problem of a 3-link horizontal bar robot with nonzero initial angular momentum. Two joints of the robot can be controlled under the in-phase or out-of-phase constraint. We alrady succeeded in realizing 3-link aerial robot control under the in-phase constraint by using anglular velocity in our previous study. In this paper, we show a way to control the robot under the in-phase and out-of-phase constraint by using torque input. First, the law of conservation of angular momentum is shown and an error equation is derived for a 3-link aerial robot. Next, the necessary condition which assures the existence of the control low under the out-of-phase constraint is derived. A feedback control law is derived by the backstepping technique which guarantees Lyapunov stability of the error system. The feedback control input is calculated numerically by solving a fourth order equation. The problem of un-uniquencess of the solution is avoided by a simple condition. Finally, simulation results are presented to show validity of the proposed control strategy.