Energy Decoupling Control Strategy for Three-link Underactuated Manipulator
欠驱动三连杆机械臂能量解耦控制策略

An energy decoupling control strategy is presented for the underactuated three-link manipulator with a passive second joint. Firstly, the motion space is divided into swing-up area and balance area, furthermore, the former is divided into swing-up subspace 1 and swing-up subspace 2 so as to swing up control rapidly. Secondly, a control law based on Lyapunov function is employed to make the third link stretch in a natural way, that is, the angle and angular velocity of the third link converge to zero, which can decouple the energy and the states of the third link in the swing up process. Next, another control law is designed to increase the energy in the swing-up subspace 2 to make the system swing up to the balance area. Then, a balancing control law based on linear quadratic regulator (LQR) stabilizes the system at the upright equilibrium. Finally, some simulation results demonstrate the validity of this method.