High Stiffness 6-DOF Dual-Arm Cooperative Robot and Its Application in Blade Polishing

To overcome the issue of poor absolute positioning accuracy owing to the low stiffness of serial robot arms, this study proposed a new dual-arm robot (DAR) through the optimisation of the configuration of traditional robots. The DAR adopts a novel kinematic structure comprising a pair of 3-degree of freedom (DOF) robots: the workpiece and tool arms. A kinematic modelling method based on a closed-loop virtual kinematic chain was proposed to solve the problem of synchronous control of both arms via one controller. The workspace of the DAR was calculated, and the singularity was analysed. Furthermore, the stiffness was evaluated through finite element analysis. The results demonstrate that the DAR exhibits significantly higher stiffness, thus enabling considerably better positioning accuracy. To verify the superiority of the proposed DAR, a machining platform was developed based on the DAR for grinding and polishing an aero-engine blade. Compared to a traditional serial 6-DOF robot, the proposed DAR significantly improved the contour accuracy, with a surface roughness Ra 0.3 v.s. 0.4 $\mu $ m. Furthermore, the profile deviation of the blade body and edge were $+$ 0.05 mm, -0.07 mm v.s. $+$ 0.075 mm, -0.07 mm, and $+$ 0.05 mm, -0.03 mm v.s. $+$ 0.05 mm, -0.05 mm, respectively. Note to Practitioners —This study aimed to enhance the machining accuracy of industrial robotic machining. A novel dual-arm robot with superior stiffness was designed and compared with a conventional serial 6-DOF robot. A prototyping DAR was developed as the foundation for a grinding platform's subsequent design and construction. The platform was utilised in aero-engine blade grinding and polishing. The contour accuracy of the processed blade drastically improved compared with that of the traditional serial 6-DOF robot system. Experiments verified the proposed robot's feasibility and superiority in improving the robotic machining accuracy. Furthermore, the proposed DAR exhibited good potential for application in other robotic machining scenarios, such as assembly, carving, etc.