Kinematics And Dynamics Analysis Of A 4-Dof Parallel Mechanism

In this paper,a 2-RPU&2-SPS four-degree-of-freedom spatial parallel mechanism(SPM)is taken as the research object,and the three-dimensional model is established by SolidWorks software.Then analyzed the kinematics of the mechanism by studying schematic model of the 2-RPU&2-SPS SPM,the kinematic analysis including inverse position analysis,forward position analysis,working space,singularity analysis and transmission performance.On this basis,the inverse dynamic analysis of the parallel mechanism is studied and analyzed by newton-euler method,which including the solution of velocity and acceleration of each limb.Then,the inverse dynamic solution equation of the mechanism is established.Finally,Adams software and Matlab software are used to simulate the kinematics and dynamics of the parallel mechanism respectively.The research content of this paper is mainly divided into the following parts:(1)The three-dimensional model of the 2-RPU&2-SPS SPM is established by SolidWorks software.Firstly,the number and property of degrees of freedom(DOF)of the SPM are analyzed by screw theory.There are two rotational and two translational movements(2R2T)of the mechanism that can be achieved.Secondly,the position analyses are researched.For the inverse position analysis,the explicit expression can obtain from the independent motion parameters of the given mechanism,and the forward position problem is solved by calculating a set of non-linear equation system.In order to verify the accuracy of theoretical reasoning,Matlab software was used for simulation.The simulation data and theoretical derivation were compared to verify the correctness of model establishment and accuracy of equation solution.(2)In order to facilitate the better study of the 2-RPU&2-SPS parallel mechanism,the full Jacobian matrix of the mechanism is analyzed.The working space of the SPM is obtained by utilizing the search algorithm combined with the structural characteristics of 2-RPU&2-SPS SPM,and the inverse kinematic solution,and the limitation of the limb length.Then,the singular type of the mechanism is studied.Finally,the force/torque transmission performance of the mechanism is evaluated by the pressure angle.(3)Establishing limb coordinate system on each limb,it is easy to obtain the rotation matrix of the branch coordinate system relative to the reference coordinate system,and then the velocity and acceleration of each limb piston and cylinder can be obtained separately.Based on this,the Newton-euler method is used to establish the limb dynamics equation,and then the dynamic equation of the dynamic platform is established.By solving the equation,the restraining torque and driving force equation of the mechanism can be obtained.Finally,Adams software is used to simulate the dynamics of the mechanism.