Optimal Design Method Of Six-Cable Driven Parallel Mechanism

With the advantages of small mass,large span and strong carrying capacity,etc.Cable-driven parallel mechanism has received widespread attention in engineering applications.This article takes a six-cable driven parallel mechanism as the research object,and focuses on the analysis of its kinematics,workspace,dynamic load capacity and multi-objective structure optimization design methods.The specific content is as follows:According to the vector theory,a kinematic model of the mechanism is established,the non-linear relationship between the end effector and the cable is deduced.Then the motion trajectory is planned,and the kinematics simulation is performed on this basis to verify the accuracy of the model.From the perspective of qualitative analysis and quantitative analysis,based on the closed conditions of wrench-closure,and regard gravity as a pull-down cable,the position of the end effector of the mechanism satisfies the boundary determination conditions and analytical expression of the wrench-closure workspace are analyzed.Its sufficient and necessary is proved.Secondly,based on the theory of matrix zero space,a numerical solution method of closed workspace of force and rotation suitable for six-cable driven parallel mechanism is given.Finally,calculate the ideal volume and shape of the workspace,and optimize the volume and shape of the working volume of force and volume by changing its size and structure.The dynamic load carrying capacity of the six-cable driven parallel mechanism is analyzed,and the dynamic equation of the drive unit is considered.Based on this,the dynamic load carrying capacity index is defined.Considering the effects of gravity and inertial force,the concept of equivalent pulling force is proposed,and the maximum and minimum values of the maximum external load including the equivalent pulling force are calculated using the explicit solution method and the Lagrangian-based proportional method,respectively.When the pose and speed of the end effector are different,the dynamic changes of the dynamic load capacity and dynamic load capacity of the six-cable driven parallel mechanism are analyzed.Taking aircraft fading and painting maintenance as the application scenario,an optimization rule is proposed for the six-cable driven parallel mechanism,the static stiffness of the mechanism is analyzed.Taking the minimum workspace volume of the mechanism,the global mean index of stiffness,the global fluctuation index of stiffness and the index of dynamic load capacity as the optimization goals,the radius ratio of the static platform to the dynamic platform,the corresponding angle of the short side,and the combined mass of the end effector and load are used.The design variables are used to establish a mathematical optimization model,and an improved NSGA-II algorithm based on Pareto’s optimization is used for multi-objective optimization.