Abstract
This paper mainly focuses on dynamic modelling and real-time control for a parallel manipulator with flexible link. The Lagrange principle and assumed modes method (AMM) substructure technique is presented to formulate the dynamic modelling of a two-degrees-of-freedom (DOF) parallel manipulator with flexible links. Then, the singular perturbation technique (SPT) is used to decompose the nonlinear dynamic system into slow time-scale and fast time-scale subsystems. Furthermore, the SPT is employed to transform the differential algebraic equations (DAEs) for kinematic constraints into explicit ordinary differential equations (ODEs), which makes real-time control possible. In addition, a novel composite control scheme is presented; the computed torque control is applied for a slow subsystem and the H∞ technique for the fast subsystem, taking account of the model uncertainty and outside disturbance. The simulation results show the composite control can effectively achieve fast and accurate tracking control.
Highlights
In modern industry there are increasing demands for high speed, high acceleration and high accuracy manipulators
The assumed modes method (AMM)‐based substructure technique and the Lagrange principle are applied to formulate the dynamic modelling of a 2‐DOF flexible‐link parallel manipulator towards the end of achieving real‐time control; an singular perturbation technique (SPT) form of flexible dynamic modelling is developed to divide the nonlinear dynamic system into two subsystems for the design of a reduced‐order controller
Generalized dynamic modelling has been established for the two‐flexible‐link parallel manipulator by using the Lagrange‐Euler principle, the assumed mode method‐ based substructure technique
Summary
In modern industry there are increasing demands for high speed, high acceleration and high accuracy manipulators. Flexible dynamic modelling and advanced model‐based control of parallel manipulators are essential for high‐ accuracy tracking [1] [2]. Flexible dynamic modelling has been the subject of intense research [4], whereas few papers have been published on parallel mechanisms because of the closed kinematic chains constraints (CKCCs). Effective dynamic modelling is necessary for real‐time control and control scheme design of a flexible parallel manipulator. The AMM‐based substructure technique and the Lagrange principle are applied to formulate the dynamic modelling of a 2‐DOF flexible‐link parallel manipulator towards the end of achieving real‐time control; an SPT form of flexible dynamic modelling is developed to divide the nonlinear dynamic system into two subsystems for the design of a reduced‐order controller. At the end of this paper, numerical simulations are performed to investigate the effectiveness of the novel control scheme
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