## 5 Conclusions  
In this paper, based on the theory of rigid body motion, the tracking error model of an SDC system considering the tilt error of azimuth axis is established. The influence of radial angle and tangential angle of azimuth axis on the tracking performance of an SDC system is studied in detail. Under the influence of azimuth axis tilt error, the variation law of tracking performance of an SDC system in initial tracking position, operation area, and the whole year operation period are analyzed. The main conclusions are as follows:  
(1) Under the influence of azimuth axis tilt error, the deviation of the initial tracking position of an SDC system in the horizontal or vertical plane will reduce its tracking performance and tracking performance stability compared with the initial tracking position being due east. Therefore, controlling the initial tracking position of an SDC system is one of the factors to ensure its tracking performance. (2) Latitude is the main factor that determines the tracking performance and tracking performance stability of an SDC system in different regions, and longitude is a secondary factor. Under the influence of azimuth axis tilt error, an SDC system's tracking performance and its tracking performance stability are better in areas with a relatively lower latitude. The SDC system's tracking performance and its stability are better in different regions close to latitude and with a lower longitude. This has guiding significance for the site selection of large-scale dish power stations. (3) During a whole year operation period, when the azimuth axis tangential angle \(\phi_{1}\) = 0\({}^{\circ}\) (due south), the tracking performance and tracking performance stability of an SDC system can be guaranteed at the same time. The tracking performance of an SDC system in the first quarter and the fourth quarter is relatively better, and the tracking performance stability in June and July is relatively better. Conceptualization, Y.P. ; methodology, Y.L. ; software, J.Y. ; validation, Y.L. ; investigation, Y.L. ; writing--original draft preparation, Y.L. ; visualization, Y.L. ; supervision, Y.P. and \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & & & & & & & & & & & \\ \cline{2-11}  & **0** & **15** & **30** & **45** & **60** & **75** & **90** & **105** & **120** & **135** & **150** & **165** \\ \hline Date & 06/21 & 12/12 & 12/10 & 12/05 & 11/27 & 11/01 & 05/01 & 06/01 & 06/19 & 06/16 & 06/19 \\ \(\sigma_{\text{min}}\) & 0.646 & 0.592 & 0.524 & 0.480 & 0.467 & 0.481 & 0.507 & 0.513 & 0.529 & 0.555 & 0.588 & 0.621 \\ \hline Date & 02/05 & 08/01 & 07/01 & 07/01 & 07/01 & 07/01 & 02/01 & 01/01 & 01/01 & 01/01 & 01/01 & 01/01 \\ \(\sigma_{\text{max}}\) & 0.705 & 0.654 & 0.613 & 0.577 & 0.545 & 0.528 & 0.553 & 0.616 & 0.678 & 0.728 & 0.761 & 0.757 \\ \hline \hline \end{tabular}
\end{table} 
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