Stabilization of underactuated four-link gymnast robot using torque-coupled method. (December 2015)

• Record Type: Journal Article
• Authors: Zhang, Ancai; Qiu, Jianlong; Yang, Chengdong; He, Haibo
• Is Part Of: International journal of non-linear mechanics. Volume 77(2015)
• Page Start: 299
• Page End: 306
• Publication Date: 2015-12
• Subjects: Underactuated mechanical systems -- Torque-coupled -- Lyapunov function -- Nonlinear control; Nonlinear mechanics -- Periodicals; Mécanique non linéaire -- Périodiques; Nonlinear mechanics; Periodicals; 531
• DOI: 10.1016/j.ijnonlinmec.2015.09.002
• Languages: English
• ISSNs: 0020-7462

Abstract

Abstract: In this paper, we use an underactuated four-link gymnast robot (UFGR) with a passive first joint to model a gymnast on the bar, and consider the stabilization of the UFGR at the straight-up position. First, we introduce a coupled relationship between control torques for the UFGR. It decouples some state variables of the UFGR from others and changes the nonlinear UFGR system into a cascade-connected system. And then, we use an energy-based method to design a stabilizing controller for the zero dynamics of the cascade-connected system. And the triangle lemma guarantees the control objective of the UFGR to be achieved. The torque-coupled method transforms the stabilization of an underactuated four-link manipulator into that of an underactuated two-link acrobot. This makes the structure of the control system simple. Moreover, our proposed control strategy is easy to extend to the stabilization control of other multi-input nonlinear underactuated systems. Simulation results using the characteristics parameters of a gymnast demonstrate the validity of the proposed method. Abstract : Highlights: A coupled relationship between control toques is constructed for an underactuated four-link gymnast robot (UFGR). It changes the nonlinear UFGR system into a cascade-connected system. We transform the stabilization of the UFGR into that of an underactuated two-link acrobot. An energy-based stabilizing controller is designed for the two-link acrobot. The structure of the proposed control system is simple. And our proposed strategy is easy to extend to the stabilization control of n-DOF ( n > 4 ) underactuated manipulator.