A practical coordinate unification method for integrated tactile–optical measuring system

• A new method is developed to perform the unification of tactile and optical sensors.
• This approach is flexible and effective for the integration of CMM with optical sensors.
• Different measuring devices do not need to be placed in the same workplace.
• It is carried out only once before a series of measurements.
• The method of using three centroids is superior to simply taking additional points on more spheres.

To meet the requirement of both high speed and high accuracy 3D measurements for dimensional metrology, multi-sensor measuring systems have been developed to measure, analyse and reverse engineer the geometry of objects. This paper presents a new development in coordinate unification called the “centroid of spherical centres” method, which can be used instead of the traditional method which uses three datum-points to perform the geometric transformation and unification of tactile and optical sensors. The benefits of the proposed method are improved accuracy in coordinate unification and the method is used to integrate a coordinate measuring machine (CMM) and optical sensors (structured light scanning system and FaroArm laser line probe). A sphere-plate artefact is developed for data fusion of the multi-sensor system and experimental results validate the accuracy and effectiveness of this method.