Research On Design,Multibody Dynamics And Control Of Redundant Parallel Robot With Multiple Actuation Modes

With the rapid development of advanced manufacturing industry,parallel robots are being applied increasingly widely in the high-end technology field.This brings a significant challenge to the design and control of parallel robots.In order to conquer the singularities within workspace of parallel robots and then improve the dynamic performance,a redundant parallel robot with multiple actuation modes is taken as the analysis object.On this basis,the issues of conceptual design,rigid-body dynamic analysis and dimensional synthesis,flexible multibody dynamic modeling,dynamic characteristic analysis as well as active control strategies design are systematically investigated.The main contributions are as follows.(1)Some innovative designs are performed based on the traditional planar 5R parallel robot,and a novel redundant parallel robot(RAParM-I)is proposed,which can realize multiple actuation modes.The singularity analysis results suggest that,the redundant actuation modes can conquer completely the Type II singularities within the workspace of traditional planar 5R parallel robot.(2)On the basis of kinematic analysis,the rigid-body dynamic model of system is developed using the Lagrangian formulation.Based on the uniformly inverse dynamic model under multiple actuation modes,two global dynamic performance indices are proposed by taking into accounts both inertia and centrifugal/Coriolis effects,which can comprehensively describe the dynamic performance of system.On this basis,the dynamic dimensional synthesis is performed subject to geometric constraints and some kinematic performance constraints.Thus,a set of optimal dimensional parameters with consideration of multiple actuation modes can be obtained.(3)One kind of planar beam element with lumped parameters at both ends is proposed and a corresponding dynamic model is deduced based on the finite element method(FEM)and Lagrangian formulation.Furthermore,the dynamic model of arbitrary flexible body is derived in an explicit form,which possesses a good modular characteristic.On this basis,the flexible multibody dynamic model of system is established by virtue of the augmented Lagrangian multipliers approach,which incorporates both the generalized rigid-body and flexible coordinates of system and is a set of differential and algebraic equations.(4)Based upon both the rigid and flexible multibody dynamic models of system,the system dynamic performance is investigated.The results of natural frequency analysis reveal that,the lumped parameters have a softening effect on the whole system and must be taken into account during modeling.To balance the solving efficiency and precision,a hybrid numerical algorithm is proposed.On this basis,a dynamic simulation flow is formulated to perform the dynamic simulation under different actuation modes.Then the dynamic performance of RAParM-I under different actuation modes are investigated thoroughly in terms of time domain dynamic response,trajectory tracking errors and system dynamic stress.Finally,a virtual prototype model is developed to demonstrate the validity of the theoretical model.(5)To cater for the requirement of dynamic control,the nonlinear rigid-flexible coupling dynamic model of system is developed based on the assumed mode method(AMM)and recursive kinematics.On this basis,the dynamic simulation is performed by means of modal truncation method.The results indicate that the computational efficiency can be improved significantly through selecting only the first order mode.This lays an important theoretical foundation for active control.(6)To address the problem of trajectory tracking and synchronous vibration suppression of flexible parallel robots,three types of active control approaches are proposed.Firstly,the Udwadia-Kalaba theory is extended to the flexible multibody dynamic control field for the first time,and then an open-loop control strategy based on servo constraint is proposed.Secondly,by integrating the rigid-flexible coupling dynamic model of mechanical system and the dynamic model of electrical system together,the electromechanical coupled dynamic model(ECDM)is formulated.On this basis,a hierarchical compound control strategy is proposed.Finally,the nonlinear ECDM is further decomposed into two subsystems in different timescales.On this basis,a nonlinear hybrid control(NHC)approach is proposed.The aforementioned control approaches are verified by corresponding simulation examples.The outcomes of this dissertation will have important theoretical and engineering significance to the development of traditional parallel mechanism theory.Meanwhile,they also may provide some beneficial reference for the development of emerging redundant parallel robots.