Research On Kinematic Statics And Singularity Of Redundant Drive 2SPR-2RPU Parallel Mechanism

Aiming at the welding application requirements in the field of aerospace,automotive and other aluminum alloy parts manufacturing,this paper proposes a new redundant drive 2SPR-2RPU parallel mechanism as the main feed mechanism of friction stir welding robot.The degrees of freedom of the mechanism were calculated using the method of the spiral theory,and the inverse position solution and velocity Jacobian matrix were solved.Considering the gravity factor of the parallel mechanism,a static model of the 2SPR-2RPU parallel mechanism was established.Because the number of degrees of freedom of the mechanism is less than the number of drives,its driving force has multiple distribution methods.In view of the redundancy of mechanism driving,the Lagrange multiplier method is used to distribute the driving force.The singularity of the 2SPR-2RPU parallel mechanism was analyzed based on the speed Jacobian matrix,and its singularity was avoided by reasonable design of the size of the mechanism rods.The main contents of this article include:(1)This paper proposes a new type of redundant drive 2SPR-2RPU parallel mechanism for the application needs in the aerospace and automotive aluminum alloy parts.Describes the configuration of the parallel mechanism.(2)The degrees of freedom of the 2SPR-2RPU parallel mechanism were calculated using the method of the spiral theory,the position solution was solved using the vector method,and the working space of the mechanism was established.The kinematic Jacobian matrix of the redundantly driven 2SPR-2RPU parallel mechanism was obtained,and based on the Jacobian matrix,the kinematic performance evaluation indexes of the mechanism such as singularity,bearing capacity and dexterity were established.(3)A mathematical model of the stress on the welding process of automotive thin-plate parts with a dual-axle shoulder friction stir welding head was established.Static analysis was performed on the parallel robot using the dismantling method.Because the number of degrees of freedom of the mechanism is less than the number of drives,the driving force has multiple methods of distribution.Therefore,the Lagrange multiplier method is used for the characteristics of mechanism drive redundancy.The objective function is introduced,and the driving force of the parallel mechanism isdistributed and solved.Based on the static mechanical force model obtained from the analysis,the strength of important components of the 2SPR-2RPU friction stir welding parallel robot was checked using finite element analysis software based on specific examples.The prototype platform of the 2SPR-2RPU parallel mechanism was set up,and the hardware selection of the prototype control system and the method of establishing its communication were briefly introduced.(4)The Lagrangian method was used to establish the dynamics equations for the redundantly driven 2SPR-2RPU parallel mechanism,and the Lagrange multiplier method was used to allocate the driving force to the mechanism.The redundant drives were calculated and plotted using Matlab software.The driving force of the2SPR-2RPU parallel mechanism under a fixed trajectory laid the foundation for the solution of the dynamics of the parallel mechanism for the later research on the control of the redundantly driven 2SPR-2RPU parallel mechanism.