# Selection of Optimal Path Control Algorithms for Probe Heads Used on Five-Axis Measuring Systems
## 1 Introduction  
### State of Art in Modern Coordinate Measurement Metrology  
Changes that can be observed in industry over the last years are commonly termed as a fourth industrial revolution. They are aimed at tightening the connection between individual components of the production process in order to reduce the manufacturing time and improve the quality of produced goods [1; 2]. This trend is present in all industry branches connected with the production process, including quality control, especially coordinate metrology. Currently, the efforts of producers of measuring systems are focused mainly on the development of contactless techniques such as computed tomography (CT) or 3D scanners, often combined with industrial robots [3; 4; 5]. Their advantages are well known, most of all their high measurement speed and, in case of CT, their possibility of part interior inspection. However, the accuracy of mentioned systems still cannot be compared to classic tactile coordinate measuring machines (CMMs), which for decades have been the key element of modern, automated quality control. Classic CMMs are still developed and enriched with solutions that improve their accuracy and efficiency. Utilization of the articulating probing systems that have the ability of continuous indexation (described in details in sub Section 1.2) fits in with this trend. A machine equipped with such a device becomes the five-axis system, capable of carrying out measurements with rotational movements of the probing system. In case of measurements of rotational features, it may cause a significant reduction of measurement duration and, for some measuring tasks, even accuracy improvement. Figure 1 shows results of the experiment that involved reference ring measurements performed in two different modes on the same five-axis measuring system; once using only transitional moves of a CMM during probing, and once utilizing only the rotational movements of a articulating probing system. In both cases the applied measurement strategy was the same: The ring was measured in 32 points, distributed evenly across half of the reference ring's height, and, for both tested modes, measurements were performed 10 times. As can be seen, measurements performed with the rotation of the probing system reduced values of errors of form deviation measurements by nearly half, in relation to traditional three-axis measurements, and also contributed to the improvement in measurement repeatability. Additionally, it should be mentioned that the time needed to perform measurements with rotations of the probing system was two times shorter than in the case of the three-axis measurement. That results show that articulating probing systems are an interesting addendum to the possibilities of classic CMMs and they should be developed in the future. However, there are still many questions arising around this subject, with questions about articulating probing systems' accuracy and factors that may affect such probing systems' performance, being the most important ones. The software path control method, software correction, and algorithms used during measurement points determination are crucial for the proper operation of such measuring systems. This paper focuses on the first of mentioned factors, whereby we show the changes in measurement results depending on chosen path control method, and present how proper measurement strategy selection can contribute to the improvement of performance of the five-axis measuring system. Considerations presented in this paper are topically related to the research on computer-aided inspection planning and the optimization of measurement strategy. There are a lot of papers focused on the optimization of the strategy of measurements performed on CMMs that use indexing probe  
Figure 1: The results of the experiment showing the difference between measurements done using only the classic, three-axis coordinate measuring machine (CMM) and measurements done using measuring head movements. Error bars present the range of individual measurement results.