An image-based algorithm for generating smooth and interference-free five-axis sweep scanning path

Abstract

Five-axis continuous scanning inspection is an emerging technology in measuring free-form surfaces. Compared to the traditional three-axis scanning inspection, the five-axis continuous surface scanning tremendously boosts the inspection efficiency and suffers from less dynamic error due to adopting a special sweep scanning working mode, which lets the super-light and high-speed rotary two-axis probe head take over the majority of the inspection work. However, there has not been any efficient method to generate sweep scanning path for a free-form surface with external obstacle. The major problem is how to guarantee the non-interference condition during the scanning process. In this paper, a two-step algorithm for generating smooth and interference-free sweep scanning path is proposed. First, an image-based algorithm is proposed to incrementally calculate the admissible area of the stylus along the scanning path. Then an optimized B-spline fitting algorithm is proposed to find the optimal probe head trajectory within the admissible area, which simultaneously guarantees the smoothness and non-interference of the trajectory. In the real experiment, the average tangential velocity and acceleration of the machine's translational axes with the proposed five-axis sweep scanning path are only 16.45% and 17.19% of those with three-axis zigzag scanning path respectively. When inspecting a high-accuracy cylindrical surface with high scanning velocity, the root mean square of the surface profile error is 0.002 mm and 0.004 mm in five-axis scanning and three-axis scanning respectively. The experimental result manifests that the sweep scanning path tremendously helps to reduce the kinematic loads and the dynamic errors of the inspection machine.