Dynamic Analysis Of 4-UPS-RPS Spatial Parallel Mechanism With Clearance

In the practical application of parallel mechanism,there is a certain clearance between the motion pairs. Clearance is the necessary condition to ensure the mechanical assembly and normal operation, but also can reduce the operation precision of the mechanism, cause vibration, deteriorate the dynamic performance and reduce the service life of the mechanism. Therefore, the influence of kinematic pair clearance cannot be ignored in the dynamic analysis of parallel mechanism. The main study contents were as follows:Firstly, dynamic statics model of parallel mechanism was established according to d'Alambert principle. The driving force of the driving chain and the constraint force of the spherical pair on the moving platform were derived based on that.Matlab was used to calculate the driving force of the driving chain and the constraint force of the spherical surface. At the same time, ADAMS was used to carry out virtual prototype simulation of the parallel mechanism. The correctness of the dynamic static model of the parallel mechanism was verified by comparing results of the two softwares.Then, the clearance was regarded as a rigid massless rod in the continuous contact model, based on which the spherical clearance model was established. The kinematics and dynamics model of parallel mechanism considering the clearance of spherical pair was deduced. The trajectory of the moving platform was planned to solve the displacement, velocity, acceleration, driving force and constraint reaction of the driving chain 1 by using Matlab. Compared with the ideal state, the kinematic and dynamic errors of the driving chain 1 of the parallel mechanism under different clearances are analyzed.Finally, based on the continuous contact model, the model of the spherical clearance was established, and the displacement, velocity, acceleration, driving force and constraint reaction of the parallel mechanism was derived. The model was solved by Matlab, and the kinematics and driving force of the drive chain were analyzed.The influence of multi clearance states on the kinematics and dynamics performance of parallel mechanism were compared and analysised under different trajectories.