Research On Dynamic Characteristic And Structual Parameters Of Performance Optimazation For A Novel 5-DOF Parallel Mechanism

In order to apply the parallel mechanism to the sea level recovery platform of spacecraft,a new five-degree-of-freedom parallel mechanism called 5-PSS/UPU parallel mechanism,which can realize three-shift and two-rotation,is proposed as a flexible adaptive dynamic balancing device.With the closed-chain structure of the parallel mechanism,the dynamic characteristics and control accuracy of the 5-PSS/UPU parallel mechanism are affected by multiple factors such as joint friction,inertia coupling and component deformation under high-speed and heavy-load motion conditions.Therefore,to improve the motion performance of the parallel mechanism and the output precision of the moving platform,a multi-objective performance parameter optimization method based on space models and principal component analysis is proposed and resarch on the dynamic characteristic of the parallel mechanism.(1)Firstly,the freedom of 5-PSS/UPU parallel mechanism is analyzed by the screw theory,and the degree of freedom of the mechanism is further verified by the modified formula.Secondly,the position,velocity and acceleration of the mechanism are derived based on the vector method.Finally,the variation of the length,velocity and acceleration of each drive branch with time is obtained by numerical simulation.(2)On the basis of the kinematics modeling,the position inverse equation,kinematics transmission equations,the screw theory analysis of the single drive branch and several global performance indicators are given.Secondly,spatial model technology is used to reveal the function of each performance evaluation indexes between each structure parameters of this 5-PSS/UPU Parallel Mechanism.Then the principal component analysis(PCA)method is used to study the correlation between the global performance indicators,and get comprehensive performance evaluation index function.(3)The dynamics model of 5-PSS/UPU parallel mechanism is established by Newton-Euler method under the condition of joints friction effect,and carry out the numerical simulation of the mechanism dynamic model.Then,based on dynamic model,analysising coupling characteristic and obtaining the inertia coupling evaluation index in the different poses of this parallel mechanism workspace.(4)Considering the active branhed-chains' elastic deformation,the static stiffness analysis and elastic dynamics modeling were carried out for the 5-PSS/UPU parallel mechanism.Based on this,the stiffness performance evaluation index is given.Secondly the active rod and the screw rod are respectively considered as the equal-section space beam element and the plane beam element model to establish the corresponding elastic dynamic equation is by the lagrange method and finite element method.Finally,establishing the whole machine elasticity to study the dynamic characteristics,and the numerical simulation analysis of the established static stiffness model and elastic dynamic model is carried out.The paper is research on dynamic characteristic optimization and structural parameters of performance optimization for 5-PSS/UPU parallel mechanism,which is significance to improve the kinematics performance and the output accuracy of the platform.And it can also provide important references for the subsequent control strategy research.