| Aiming at the demand for grinding maintenance equipment of aircraft composite skin,the flexible error of a new 3-DOF parallel mechanism with asymmetrical architecture(TAM)is studied.In order to improve the working accuracy,a comprehensive elastic dynamics model of TAM with joint clearance is established.The flexible error analysis and compensation are deeply researched.The main research contents of this project are as follows.According to the asymmetrical spatial structure of TAM,the mechanism is divided into three parts: telescopic rod branch chain,parallelogram branch chain and moving platform.Considering the flexibilities of rods and joints,the elastodynamic equations of each branch chain are established by means of finite element method.Based on the elastic deformations coordination condition and the coupling technique of node degrees of freedom,the elastodynamic equation of the system is obtained.The normal distribution is adopted to establish the branch chain model with joint clearance.In order to establish the comprehensive elastic dynamics model of TAM with joint clearance,and obtain the flexible error analysis model,the Lankarani-Nikravesh contact force model and the Coulomb friction model with the dynamic correction coefficient are combined to research the generalized collision force in joint clearance.A virtual prototype platform is built,and the variation rules of flexible error are obtained through numerical calculation and simulation analysis.The compensation method for flexible error in trajectory optimization is researched respectly.The trajectory planning for drive rod in joint space is implemented by cycloid motion.The interpolation method about combined sine motion is used between two adjacent variables of drive rod.The minimum flexible error is treated as the optimization objective function.The trajectory optimization method for drive rod based on the particle swarm optimization is designed to compensate the flexible error of TAM. |
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