Research On Nut Tightening Mechanical Arm Applying Large Torque In Restricted Space

This paper shows that bolt connection is the connection method for important parts of aero-engine,and the quality of the nut directly affects the performance of the entire engine.The aerospace engine has a small inner cavity space,which limits the movement space of the assembly tool.Compared with traditional tightening tools,the robot arm has higher control precision,better rigidity and strength.Therefore,it is of great theoretical significance and engineering value to study nut-tightening mechanical arms with high torque output in confined spaces.Aiming at the problem of the automatic tightening of nuts in key parts of aero engine,this paper establishes and analyzes the static,kinematic and dynamic models of the four-degree-of-freedom nut tightening manipulator.Torque nuts were used to tighten the mechanical arm engineering prototype,which was experimentally verified.The main research work of this article includes the following aspects:1.Analyzed the related research work of domestic and foreign robotic arms and the nut tightening torque curve.Aiming at the research on the restricted space work and high torque output of nut tightening robotic arms,a new robotic arm configuration was proposed and the robotic arm was designed.The structure was analyzed statically on the nut-tightened mechanical arm,and the system and key parts were simulated and verified by finite elements,which verified that the mechanical arm has sufficient strength and stiffness.2.Determine the DH parameters of the four-degree-of-freedom nut tightening manipulator,derive the pose matrix of the manipulator,construct the kinematic model of the manipulator,and analyze the forward solution,inverse solution,Jacobian matrix,and working space of the manipulator.Based on the characteristics,the point-to-point trajectory planning and simulation of the manipulator was performed,and the feasibility of the manipulator’s movement in the restricted space was analyzed,which laid the foundation for the dynamic analysis.3.Based on the analysis of statics and kinematics,the dynamic equations of the nut-tightened mechanical arm are analyzed and derived.The dynamic model of the nut-tightened mechanical arm is established.The joint angular displacement,angular velocityand drive during the movement of the mechanical arm are studied.The value and changing trend of the torque prove the rationality of the selection of the robotic joint motor and reducer.4.Based on Beckhoff ’s software and hardware development platform,design and develop a nut tightening robot arm control system based on industrial PC and fieldbus,simulate and implement a polynomial trajectory planning algorithm in real time,simulate and verify the torque control PID method,and set the PID Parameter,experimentally determined and analyzed the nut tightening curve,and verified the performance change law of the nut under the action of large torque.