Posture Control of A 3-link Acrobot By Angular Velocity Input: Control Strategy Based On Constraint of Joint Angles

This paper deals with an aerial posture control problem of a 3-link free-flying robot with nonzero initial angular momentum. First, the law of conservation of angular momentum is shown, and a state equation based on two angular velocity inputs is derived for a 3-link free-flying robot. Next, the control strategy which consists of two steps is proposed. The first step of the strategy is to control two joint angles and the second step of the strategy is to control three angles by feedback controller under the inphase constraint of the joint angles. In particular, the feedback control law of the second step is derived by the backstepping technique which guarantees Lyapunov stability by time-varying gains. Finally, simulation results are presented to show validity of the proposed control strategy.