An on-line contour error estimation and compensation strategy for five-axis local smoothed trajectory under motion time synchronization

The accurate estimation and effective compensation of contour error are beneficial to the realization of high-speed and high-precision five-axis machining. And the movements of the five-axis trajectory can be synchronized by either curve parameter or motion time. This paper focuses on developing an on-line contour error estimation and compensation strategy for the five-axis local smoothed trajectory under motion time synchronization. First, to perform an on-line contour error estimation, the algorithms to find the contouring cutter location are proposed. Here, the contouring cutter location consists of the tool tip contouring point and tool orientation contouring vector. Without the construction of any frame, the segment of the smoothed trajectory where the tool tip contouring point is located is found by comparing the length of the projection of the tool tip actual point on the linear path. Then, depending on the type of this segment, two different ways to fine locate the tool tip contouring point are shown. In the meantime, the corresponding tool orientation contouring vector under motion time synchronization is obtained in the interpolation segment by the proposed rough and fine matching method. Second, as to the on-line contour error compensation, three compensators are designed to send the decoupled contour error estimation values back to the position loop, velocity loop, and current loop of each servo controller. Finally, simulation and experiment show that the proposed method can achieve high-precision on-line estimation and effective on-line compensation of contour errors for the trajectories under both curve parameter synchronization and time synchronization compared with the existing method.