Touch Trigger Probe-Based Interference-Free Inspection Path Planning for Free-Form Surfaces by Optimizing the Probe Posture

Abstract

Free-form surface inspection is a challenging task due to its complex geometry. Coordinate measurement machine (CMM) and on-machine measurement (OMM) equipped with the touch-trigger probe are commonly used for their high accuracy and ease to operate. Path planning plays a pivotal role in measuring free-form surfaces with accuracy and efficiency, which considers accessibility and stability of probe movement, as well as the total inspection time (IT). In this article, an integrated path planning method is proposed for free-form surface inspection by the touch-trigger probe. The accessibility cone is defined to describe the interference-free probe pole directions for gauging an inspection point. A graphic process unit (GPU)-based algorithm that accelerates the computation of accessibility cone is developed. Then, the inspection points are divided into several clusters by a classification algorithm. In each cluster, the inspection points can be detected in the same probe pole direction. Finally, the inspection points in each cluster are sorted according to the spatial location to shorten the total path length, and the global interference-free inspection path is generated. Experimental study is conducted by applying the proposed method and an existing method to an impeller blade, respectively. The variation of probe posture and total IT is estimated and measured. Compared with the existing method, the proposed method prominently reduces motion of rotation axes, resulting in distinct decrease of total measuring time.