A novel regional force control strategy based on seven-axis linkage grinding system to improve blade machining accuracy

Abstract

The aero-engine blade has the characteristics of large curvature and uneven allowance distribution, which makes it difficult to ensure its machining accuracy during processing. The existing research mainly realizes the removal of blade allowance through constant contact force control strategy, which is difficult to achieve accurate removal of uneven allowance. This paper proposes a novel regional force control strategy based on seven-axis linkage grinding system. The ideal contact force is obtained according to the curvature and allowance distribution at each cutter-contact (CC) point, and the coefficient kp is calibrated by orthogonal grinding tests considering the initial rapid wear of the hollow ball abrasive belt. The ideal contact force is controlled by the regional force control strategy, which is composed of the regional division and the seventh axis controller. Considering the system response time and the distribution of the ideal contact force, the ideal contact force is divided into several regions through regional division algorithm, and then the actual contact force is controlled in real time during processing by the designed seventh axis controller to ensure the stability of the seventh axis. The force control accuracy with the seventh axis controller has increased by 63.7 % on the whole profile of the blade than that without the controller. The comparative robotic grinding experiment results show that the surface profile accuracy values at the four profile areas are improved by 57.6 %, 59.2 %, 70 % and 61.7 % than that with the passive compliance control (PCC) method, respectively.