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This paper addresses the problem of rigid-flexible coupling dynamic modeling and active control of a novel flexible parallel manipulator (PM) with multiple actuation modes. Firstly, based on the flexible multi-body dynamics theory, the rigid-flexible coupling dynamic model (RFDM) of system is developed by virtue of the augmented Lagrangian multipliers approach. For completeness, the mathematical models of permanent magnet synchronous motor (PMSM) and piezoelectric transducer (PZT) are further established and integrated with the RFDM of mechanical system to formulate the electromechanical coupling dynamic model (ECDM). To achieve the trajectory tracking and vibration suppression, a hierarchical compound control strategy is presented. Within this control strategy, the proportional-differential (PD) feedback controller is employed to realize the trajectory tracking of end-effector, while the strain and strain rate feedback (SSRF) controller is developed to restrain the vibration of the flexible links using PZT. Furthermore, the stability of the control algorithm is demonstrated based on the Lyapunov stability theory. Finally, two simulation case studies are performed to illustrate the effectiveness of the proposed approach. The results indicate that, under the redundant actuation mode, the hierarchical compound control strategy can guarantee the flexible PM achieves singularity-free motion and vibration attenuation within task workspace simultaneously. The systematic methodology proposed in this study can be conveniently extended for the dynamic modeling and efficient controller design of other flexible PMs, especially the emerging ones with multiple actuation modes. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of large downward force and high stiffness performance for the friction stir welding process, this paper proposes a 5 degree-of-freedom hybrid manipulator as friction stir welding robot. It is composed of a 3 degree-of-freedom redundant parallel module and a 2 degree-of-freedom rotating head. Semi-analytical stiffness model of the hybrid manipulator is firstly established by compliance models of the two substructures. Virtual work principle, deformation superposition principle and twist/wrench mapping model are applied to this compliance modeling process. A novel instantaneous stiffness performance index is then proposed on the basis of instantaneous energy defined by reciprocal product of external payload screw and corresponding deformation screw. It solves the problems of inconsistent physical unit of linear/angular stiffness and is able to evaluate overall and worst-case stiffness performance. Next, stiffness/compliance experiments are carried out to verify the stiffness model and the novel instantaneous stiffness performance index. Finally, stiffness performance of 5 degree-of-freedom hybrid manipulator is thoroughly discussed in terms of engineering requirements, worst-case stiffness performance and stiffness singularities. It can be summarized that the semi-analytical stiffness model and the novel instantaneous stiffness index are effective in analyzing and evaluating stiffness performance of the 5 degree-of-freedom hybrid manipulator. [ABSTRACT FROM AUTHOR]

A systematic dynamic modeling methodology is presented to develop the rigid-flexible coupling dynamic model (RFDM) of an emerging flexible parallel manipulator with multiple actuation modes. By virtue of assumed mode method, the general dynamic model of an arbitrary flexible body with any number of lumped parameters is derived in an explicit closed form, which possesses the modular characteristic. Then the completely dynamic model of system is formulated based on the flexible multi-body dynamics (FMD) theory and the augmented Lagrangian multipliers method. An approach of combining the Udwadia-Kalaba formulation with the hybrid TR-BDF2 numerical algorithm is proposed to address the nonlinear RFDM. Two simulation cases are performed to investigate the dynamic performance of the manipulator with different actuation modes. The results indicate that the redundant actuation modes can effectively attenuate vibration and guarantee higher dynamic performance compared to the traditional non-redundant actuation modes. Finally, a virtual prototype model is developed to demonstrate the validity of the presented RFDM. The systematic methodology proposed in this study can be conveniently extended for the dynamic modeling and controller design of other planar flexible parallel manipulators, especially the emerging ones with multiple actuation modes. [ABSTRACT FROM AUTHOR]

This paper proposes a novel parallel manipulator with 1 translational and 3 rotational degrees of freedom, which may be designed as the docking equipment for large-scale component assemblage in the aircraft industry. First, the mobility and kinematic analysis of the novel manipulator is performed using the screw theory and the closed-loop vector method. To evaluate the kinematic performance of the manipulator, its workspace is calculated, and the dimensional homogeneous Jacobian matrix of this manipulator is deduced. Mainly based on a nonlinear programming approach, the kinematic dimensional synthesis is performed to optimise the dimensional parameters of this novel parallel manipulator in a prescribed workspace. The results of this paper may lay a solid foundation for the prototype design and manufacture of the novel parallel manipulator. [ABSTRACT FROM AUTHOR]

• An efficient formulation for rigid-flexible coupling dynamics is derived for LWPM. • The ECDM is developed by integrating the RFCDM with the dynamics model of PMSM. • Two reduced-order subsystems are decoupled using singular perturbation theory. • A hybrid control is proposed for trajectory tracking and vibration suppression. • The superiority of hybrid control is illustrated by two simulation experiments. In the scenarios of high-speed operation, the bad elastic vibrations of lightweight manipulators readily arise, thus affect the overall motion of system even induce motion instability, which is a critical issue needing to be tackled appropriately. This paper concentrates on the efficient dynamic modeling and tracking/vibration integrated control for a lightweight parallel manipulator (LWPM) including servo motor dynamics. Firstly, a systematic methodology is proposed to establish the rigid-flexible coupling dynamics model (RFDM) of mechanical system possessing a modular feature, which can reduce the modeling effort. To alleviate computational burden, the RFDM is elaborately reduced to a concise model characterized by fewer generalized coordinates of system. Further, by integrating the simplified RFDM with the dynamics model of permanent magnet synchronous motor (PMSM), the electromechanical coupling dynamics model (ECDM) of system is formulated. On this basis, the ECDM is decoupled into two reduced-order subsystems by virtue of singular perturbation theory, and following that, a novel hybrid control strategy is proposed, in which a kind of task space-based proportional-integral robust sliding mode controller is designed for the slow subsystem while an quadratic optimal controller is designed for the fast subsystem. Ultimately, two simulation experiments are implemented to comprehensively investigate the dynamic performance of the presented hybrid control in comparison with the traditional joint-based PD feedback control. The results substantiate that both the excellent trajectory tracking precision of end-effector and vibration suppression can be achieved efficiently by the hybrid control, which lays a sound foundation for the application of the proposed approach in practice. [ABSTRACT FROM AUTHOR]