Structure Design and Global Stiffness Prediction Method of a NovelIndustrial Robot

A novel non-backlash industrial robot with 5 degrees of freedom is designed, and the truss structure that has a parallelogram frame and an electric cylinder driven in the diagonal direction is adopted for robotic arms, which is beneficial to improve the comprehensive stiffness of the robot. In addition, the master-slave anti-backlash control method is applied to the waist and the wrist in order to eliminate the transmission backlash, and the double nuts with preload are used in the electric cylinders for the both arms in order to eliminate the reverse backlash, which makes the robot achieve non-backlash driving. A stiffness prediction model is established according to the external load and the deformations calculated based on the strain energy to estimate the robot stiffness in the global workspace, and the effectiveness of the prediction model is verified through the integral stiffness results calculated by the finite element analysis and the experiment results of the robot prototype. Finally, the stiffness distribution characteristics of the robot are analyzed, and the rigidity advantage of the robot is demonstrated by comparing the stiffness with the Fanuc S900iB/400 industrial robot.