Design And Performance Analysis Of A Three Degree Of Freedom Planar Compliant Parallel Mechanism

Compliant mechanism can provide motions of high precision and resolution with no mechanical clearance,low friction,and becoming important in the fields of precision manufacturing.With the rapid development of precision manufacturing technology,how to design a compliant mechanism with large stroke,fast response and high positioning accuracy has become a key issue for research.Therefore,based on the beam-based flexible hinge,a three-degree-of-freedom compliant parallel mechanism for high-precision positioning is designed.The kinetostatic and dynamics model of the mechanism is established.Combined with nonlinear FEA simulation and experiment,the kinematics and motion characteristics of the mechanism are tested.The main findings and conclusions of this paper are as follows:Considering the parasitic motion caused by the deformation of the large-stroke leaf-type flexure,two compliant translational hinges and a compliant rotating hinge are presented based on the compliant parallelogram mechanism.A compliant parallel mechanism which can realize 3-PPR large range is designed by using the rigid body replacement method.Through the sensitivity analysis,the optimization variables and range of parameters are determined,the boundary constraints are set,and then the genetic algorithm is used to optimize the off-axis stiffness ratio and input stiffness of the compliant parallel mechanism.The optimized mechanism can achieve a planar motion of ±3 mm × ± 3 mm × ± 3 °,and the off-axis stiffness ratio is increased by 5.6 times.The compliance matrix method is utilized to obtain the output stiffness,input compliance and input coupling compliance of the compliant parallel mechanism.The inevitable impact caused by the coupling relationship among the kinematic branches is considered and establish the accurate kinetostatic model is conducted based on the superposition principle.Based on the second-order Lagrange equation,the dynamics of the compliant parallel mechanism is modeled.The first three natural resonance frequencies of the mechanism are obtained from the dynamic equations.The accuracy of the established models are verified by nonlinear finite element simulation and experiments.Using the voice coil motor to drive the compliant parallel mechanism,the experimental motion platform is built.The PID closed-loop control is used to drive by voice coil motors,and the motion performances of the mechanism are tested.Experimental results show that the compliant parallel mechanism can realize the planar three-degree-of-freedom motion,and the motion accuracy can be improved by the closed-loop control in the Cartesian space.The factors causing the experimental error were analyzed.