A new real-time trajectory generation method modifying trajectory based on trajectory error and angular speed for high accuracy and short machining time

A computationally efficient FIR-filtering based tool-path (trajectory) modification method, which simultaneously realizes remarkable trajectory error reduction, vibration avoidance, and short machining time, is presented in this paper. Conventional trajectory generation in NC units causes trajectory error by using smoothing filters for limiting acceleration and avoiding vibration of the machines, and this trajectory error is often too large for practical applications. Therefore, a novel trajectory generation method is presented in this paper to remarkably reduce the trajectory error by modifying the trajectory commanded by G-codes on the basis of the trajectory error and angular speed. In order to realize the trajectory modification method, three key components, (i) p-corresponding method, (ii) omega-smoothing filter, and (iii) modification gain function, are developed in this study. The pcorresponding method is required to stably evaluate the trajectory error, while the other two components are used to compute appropriate modification gains for arbitrary trajectories. The proposed trajectory modification method is completed by integrating the components (i) to (iii), and it is verified utilizing a commercial machine tool. It is confirmed that average trajectory error is reduced remarkably by the proposed method without increasing machining time or sacrificing vibration avoidance by the smoothing filter. In particular, the trajectory errors at circular arcs are eliminated almost completely, e.g., the average trajectory error is reduced significantly by about 80% for a trajectory consisting of several circular arcs and corners.

Automated summary

This paper presents a computationally efficient FIR-filtering based tool-path modification method that achieves significant reduction in trajectory error, vibration avoidance, and machining time. By modifying the trajectory commanded by G-codes based on trajectory error and angular speed, the proposed method greatly reduces trajectory error. The method is validated using a commercial machine tool and it successfully reduces average trajectory error without sacrificing vibration avoidance by the smoothing filter, particularly for circular arcs.