Research On A 2R1T Parallel Motion Simulation Platform

In recent years,parallel robot technology and computer technology has developed rapidly.The parallel motion simulator that based on parallel mechanisms(PM)and computer technology is of interest to many countries because of its economy,safety and repeatability.Motion simulators play an increasingly important role in military training and daily life.As a result,a higher demand for the main mechanism of the parallel simulator is proposed.In this paper,a novel class of symmetrical two rotational and one translational(2R1T)degree of freedom(DOF)parallel mechanisms without parasitic motion are proposed.It can mimic all the movements of the vehicle,such as sinking,yawing,pitching.A novel class of symmetrical 2R1 T PM without parasitic motion are proposed.It has the advantages of structural symmetry and easy to realize geometric condition.A special 3-UPU PM with 2R1 T DOFs which has no parasitic motion is analyzed.Its mobility property is studied by using the the screw theory.It turns out that the moving platform can rotate continually about any axis or point on the motion-plane.According to geometric characteristics,inverse kinematics of this mechanism are studied.By using the theory of kinematic influence coefficient,the relationship between the velocity of the moving platform and the driver are obtained.By using the theory of limiting boundary condition,the workspace of this mechanism is drawn out.The dynamic model of the 3-UPU PM is established by virtual work principle.Then,the dynamic model and the control system are established by matrix software,the mechanical system of the mechanism is established by dynamics software,the dynamic model is verified by the co-simulation method.Two numerical examples are given to demonstrate the feasibility and effectiveness of this dynamic model.Especially,the dynamic characteristic of this mechanism during the fixed-axis rotation is analyzed.The error of 3-UPU PM was analyzed in detail.The mapping from the errors of legs and joint-clearances to the accuracy of motion platform was achieved.And the influence rule of the mapping were analyzed using Monte-Carlo method.In the end,the structure design and size optimization of the 3-UPU PM is carried out,then the properties of the mechanism were analyzed and verified through the experiments.