Research On Performance Analysis And Design Method Of A Novel Four DOF Parallel Mechanism

Combine the parallel mechanism’s merits of strong bearing capacity, stiffness and highprecision movement with further research on lower-mobility parallel mechanism in recent years,this paper proposes a new four DOF parallel mechanism, that is, the2RRS-2RUS parallelmechanism and mainly analyzes forward and inverse solution, work space, motion performanceand dimension synthesis, transmission performance and singular configuration and inversedynamics, which provide theoretical guidance for further design and research of this mechanism.1) The kinematic model of2RRS-2RUS parallel mechanism is built by the help of closedloop loss method and the equation of inverse solutions for this mechanism’s position areobtained. Due to the hemihedrism of mechanism, half of mechanism is analyzed in forwardsolution modeling and forward closed-form solutions were obtained by using slverster resultantmatrix，with numerical examples and corresponding orientation model diagram presented.2) Use single opened chain method to analyze the workspace of branched chain movementand calculate position and orientation workspace through workspace intersection obtained bysingle chain movement. Then we obtain the reachable workspace of this mechanism throughboundary search method and analyze the impact of pose parameters on this workspace. Besides,utilize the constraint condition where the complete Jacobi matrix determinant is zero to figureout the boundary making workspace singular.3) With the establishment of dimensionless homogeneous Jacobian matrix, conditionnumber’s variety law in the workspace was obtained with condition number of homogeneousJacobian matrix as specification for motion performance.4) Establish motion/force mapping model by the screw calculus. By using the method ofvirtual coefficient,we get the conditions of satisfaction of two types of singularity occurring.Propose transmission performance indicators of three kinds of2RRS-2RUS parallel mechanismand numerical examples is given by normalized virtual coefficient.5) Establish the first and second order influence coefficient of2RRS-2RUS parallelmechanism based on influence coefficient method.and derive velocity and accelerationexpressions of each pole and joint. The moving platform and the branched inverse dynamicequations were built by using the Newton-Euler method6) Get variation of speed and acceleration of joints and links. And driving moments andconstraint forces calculated by giving numerical examples and defining motion path. Finally, the estimated motor parameters, determining motor selection is correct.