Automatic robotic polishing on titanium alloy parts with compliant force/position control

Abstract

In this article, an automatic robotic polishing technique and system is developed for the polishing of titanium alloy curved parts. By means of a designed compliant end-effector with a force sensor, the robotic polishing system with a positionbased explicit force control architecture is first built to perform the polishing operation. Then, a specially designed multi-axis robotic post-processor based on computer-aided design/computer-aided manufacturing is developed to generate the basic position and posture of the polishing tool without any complicated teaching processes. Subsequently, an adaptive Anti-Saturation Integral Separated Fuzzy PI controller, which is able to imitate the manual polishing operation and prevent undesirable vibrations and mechanical collisions, is designed to control the normal contact force. The basic trajectory is changed each time after the current polishing cycle has been finished by online self-learning, and a new basic trajectory is generated for the next polishing cycle. Finally, the effectiveness of the proposed automatic polishing technique is evaluated by actual polishing experiments on titanium alloy (TC11) parts, and the experimental results show that the proposed automatic robotic polishing technique has a perfect control effect on the contact force and thus can achieve a good and uniform surface quality of the part.

Tuning of Parameters for Robotic Contouring Based on the Evaluation of Force Deviation

“…The response error significantly decreases when the workpiece is close to the robot base and increases when the workpiece is on the edge of the robot workspace. The introduction of a compliant tool [8,21,22,23,24], which was not considered in our paper, could provide us with new insights to be used in our research. In future work, we also plan to conduct a series of measurements by developing and testing a compliant robot tool for exerting a constant normal force.…”

“…Furthermore, we plan to use the design of experiments for the assessment of the relationship between the environmental (damping, stiffness), the controller (impedance parameters), and the response (force deviation) parameters in order to optimize the controller parameters and reduce vibrations and force deviation. Another possible approach which will be taken into consideration is the development of our own controller for contouring applications whose structure and parameters would be known in detail since many studies have shown improved performance by using advanced control algorithms [7,10,11,13,16,17,21]. We also intend to use the results from this research in the development of robotic applications for sensitive bone drilling [27].…”

“…The system is composed of a specially designed end effector, a fuzzy force controller, and a software solution for the correction of polishing trajectory. It uses the force sensor data acquired after every cycle and gives a satisfactory surface quality [21]. In the absence of force and torque sensors, either compliant robot tools [22] or active robot flanges [23] can be used for the compensation of small part irregularities and geometry differences.…”

Towards an Automated Polishing System - Capturing Manual Polishing Operations

“…Researchers in the Singapore Institute of Manufacturing Technology (SIMTech) and Nanyang University have worked on an automated system for grinding and polishing operations for the refurbishment process of turbine blades [8,[19][20][21][22][23][24][25]. The authors developed two solutions, SMART Robotic System and a self-compensated closed loop RealTime Robotic Polishing System (RT-RPS).…”

A Position-Based Explicit Force Control Strategy Based on Online Trajectory Prediction

“…The simulation results show that the milling force can be tracked with zero steady-state error under this control method. Sun [19] implemented the position-based explicit force control architecture to an automatic robotic polishing system, which is aimed at the polishing of titanium alloy curved parts. An anti-saturation integral separated fuzzy proportional-integral (PI) controller is implemented as the force controller.…”