Stiffness Performance Optimization And Dynamics Modeling Method Of 6-6 Cable-driven Parallel Robot

The Cable-driven parallel robots is one of the most active robot research fields in recent years.Because of the traditional rigid connecting rod is replaced by flexible cable,make it have broad application prospects and important development value.Considering the requirements of freedom and reducing interference,this paper chooses the 6-6(6 cables with 6-dof)cable-driven parallel robot as the research object.The results are summarized as follows:Based on vector theory,the inverse position solution,inverse velocity solution and inverse acceleration solution of kinematics of the robot are analyzed,and the corresponding kinematic equations are obtained.Kinematics simulation is carried out under the circular trajectory of the end effector.The cable length,cable speed and cable acceleration were obtained with time,and the correctness of the kinematics equation was verified.The existence condition of the workspace of the cable-driven parallel robots is analyzed by the vector closure principle.The force Jacobian matrix of the robot is obtained based on the static equilibrium equation.Define two design variables,the influences of the size and structure of the 6-6 cable-driven parallel robot on the volume and shape of the workspace are analyzed for different posture of the end effector,which provides a systematic reference for the design of the robot.Based on the line vector and differential transformation formula,the complete stiffness model of the cable-driven parallel robots is derived,and the stiffness performance of the robot in the whole workspace is evaluated by defining the global mean and global volatility of the robot stiffness.The stiffness model of the robot is used to study the influence of the change of the structure of the robot on the global mean of the stiffness and the global volatility of the stiffness.Taking the workspace volume of the robot,the global mean of the stiffness and the global volatility of the stiffness as the optimization objectives,the ideal point method is used to optimize the multi-objectives of the robot,and the optimal structural parameters are obtained.Based on the obtained optimal configuration,the distribution of stiffness in all directions in the workspace is analyzed.The Newton-Euler method is used to derive the dynamic equation of the 6-6 cable-driven parallel robots.The mathematical model of the two types of pulley friction is established by using the Coulomb friction model and the Dahl friction model.The dynamic equation of the cable-driven parallel robots considering the friction between the cable and the pulley is derived.According to the Coulomb friction model and the Dahl friction model,the influence of various parameters on the cable tension and Coulomb friction is analyzed.Comparing the two friction models,it is proved that the Dahl friction model can make a smooth transition when the end effector is in the low speed state or the speed direction changes.Compared with the Coulomb friction model,the Dahl friction model can better describe the actual change of friction.