# Surface Texture Measurement on Complex Geometry Using Dual-Scan Positioning Strategy
## 6 Conclusions and Future Work  
In this paper, surface texture measurement methodology based on a dual-scan scanning mechanism has been proposed for surface texture measurement. The motivation for this study was to address the challenges of measuring surfaces with geometric complexity and irregular surface pattern.  
By setting the internal and external scanning in perpendicular directions, the system was able to perform area measurements. Areal parameters to evaluate the surface quality were obtained, including height parameters _Sa_, _Sq_ and _S10z_, statistic parameters _Ssk_ and _Sku_, and surface isotropy parameters _Str_ and _Std_.  
By setting the internal and external scanning in parallel directions, the system was able to perform line measurements over long travels. A misalignment compensation algorithm was developed to reduce the measurement error due to non-parallelism and straightness errors.  
Commercial 3D microscopes (Talysurf CCI and Zeiss Smartproof 5) and a tactile stylus profilometer (Talysurf PGI 800) were employed to evaluate the measurement performance of the proposed methodology. For area measurement in a range of 1 mm by 1 mm, and for line measurement in a scan length up to 100 mm, experimental results showed that the proposed systems were able to achieve comparable accuracy with the commercial systems.  
Future work will focus on further analyzing the effects of robotic vibration and environmental temperature variation and on developing advanced noise filtering and error compensation algorithms. In addition, the developed in situ measuring system will be fully integrated into a robotic polishing cell to conduct in situ measurements as a tool of quality verification.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**PGI 800**} & **Proposed System** & **Absolute Error** & **Relative Error** \\ \hline \multirow{2}{*}{**Zone 1**} & _Ra_ (\(\mu\)m) & \(0.56\pm 0.01\) & \(0.58\pm 0.02\) & 0.02 & 3.6\% \\ \cline{2-5}  & _Rq_ (\(\mu\)m) & \(0.69\pm 0.01\) & \(0.72\pm 0.03\) & 0.03 & 4.3\% \\ \hline \multirow{2}{*}{**Zone 2**} & _Ra_ (\(\mu\)m) & \(0.93\pm 0.02\) & \(0.97\pm 0.05\) & 0.04 & 4.3\% \\ \cline{2-5}  & _Rq_ (\(\mu\)m) & \(1.14\pm 0.02\) & \(1.19\pm 0.07\) & 0.05 & 4.4\% \\ \hline \multirow{2}{*}{**Zone 3**} & _Ra_ (\(\mu\)m) & \(1.36\pm 0.01\) & \(1.42\pm 0.04\) & 0.06 & 4.4\% \\ \cline{2-5}  & _Rq_ (\(\mu\)m) & \(1.70\pm 0.01\) & \(1.78\pm 0.06\) & 0.08 & 4.7\% \\ \hline \hline \end{tabular}
\end{table}
Table 4: Long-travel roughness measurement results.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Taylor Hobson CCI** & **Carl Zeiss Smartproof 5** & **Proposed System** \\ \hline _Sa_ (\(\mu\)m) & \(2.50\pm 0.10\) & \(2.42\pm 0.13\) & \(2.41\pm 0.12\) \\ \hline _Sq_ (\(\mu\)m) & \(3.26\pm 0.16\) & \(3.09\pm 0.19\) & \(3.04\pm 0.17\) \\ \hline _S10z_ (\(\mu\)m) & \(24.95\pm 0.16\) & \(23.02\pm 0.27\) & \(22.09\pm 0.17\) \\ \hline _Ssk_ & \(-0.18\pm 0.01\) & \(-0.14\pm 0.01\) & \(-0.17\pm 0.02\) \\ \hline _Sku_ & \(3.40\pm 0.04\) & \(3.58\pm 0.04\) & \(3.37\pm 0.08\) \\ \hline _Str_ & \(0.19\pm 0.01\) & \(0.21\pm 0.00\) & \(0.18\pm 0.02\) \\ \hline _Std_ (\({}^{\circ}\)) & \(69.97\pm 0.14\) & \(71.04\pm 0.10\) & \(70.58\pm 0.13\) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Measurement results of area scans.  
**Author Contributions:** Conceptualization, F.C. and S.F.; methodology, F.C. and S.F.; software, S.F.; validation, S.F.; formal analysis, S.F.; investigation, S.F.; resources, F.C. and Z.C.; data curation, S.F.; writing--original draft preparation, F.C.; writing--review and editing, F.C. and S.F.; visualization, F.C. and S.F.; supervision, F.C.; project administration, F.C. and S.F.; funding acquisition, Z.C. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was funded by the National Natural Science Foundation of China (Grant No. 51775075, 51935004).  
**Conflicts of Interest:** The authors declare no conflict of interest.