Automatic Polishing On Titanium Alloy Parts Based On The Force/position Control Method

Titanium alloys have wide applications in many vital fields such as aeronautics and astronautics for their excellent characteristics. Both the shape accuracy and surface quality of the high-quality titanium alloy parts have direct effects on the key performance indicators of the devices. Currently, the polishing of the titanium alloy parts is mainly done by skilled workers using manual tools. However, manual polishing is extremely time-consuming and of rugged environment, and the consistency of the manual polished surface is bad. Moreover, polishing by hands is easy to cause over polishing of the part. In this case, the technical research on the high-efficiency automatic robotic polishing of titanium alloy parts based on the force/position control method is put forward to improve the finishing efficiency, the surface quality as well as the surface consistency of the free-form titanium alloy parts.The main contents of this paper include:(1) A new robotic end-effector is developed to fulfill the polishing task. An automatic robotic polishing system, which uses the computer as the core, is established to fulfill the compliant polishing task on titanium alloy parts. The Ethernet communication is used in the system to realize the real-time transmission of data.(2) An algorithm of generating both the basic position and posture of the robotic polishing tool is proposed based on CAD/CAM, it can automatically translate the multi-axis cuter location data into the robot language to control the position and posture of the polishing tool without any complicated teaching processes. The theoretical research on the material removal properties of the titanium alloy parts is conducted based on the known tool posture. A pressure distribution model is built by using the finite element contact analysis method, and then the material removal model for titanium alloy part is established. What’s more, the theoretical analysis is also performed for the row space optimization based on the proposed material removal model.(3) The conversion algorithm from the measured force value to the normal contact force is proposed based on the force analysis of the polishing tool considering gravity compensation. An adaptive Anti-Saturation Integral Separated Fuzzy PI controller, which is based on the manual experiences to control the real-time normal contact force, is designed under the position-based explicit force control architecture, and an anti-saturation unit is added to prevent the undesirable instability caused by the large adjustment values of the position. Moreover, an online self-learning method for the basic trajectory is put forward to acquire a more precise desired trajectory in order to achieve a better force control effect.(4) The feasibility and effectiveness of the proposed high-efficiency automatic polishing technique based on the force/position control method are evaluated by actual polishing experiments on both a TC11planar part and a typical TC11curved part.