# Precision Analysis and Error Compensation of a Telescope Truss Structure Based on Robotics
## 5 Conclusions  
In this study, an SM truss structure based on robotics was proposed and analyzed in order to solve the transport-related limitations involving vehicle-mobile telescopes. The misalignment of the secondary mirror was minimized through the IKP method of Jacobian matrix iteration. The finite element analysis method was used to fit the node displacements of the surface under the gravitational field, and a PM surface error model considering the optical axis from the horizontal to the vertical orientations was established. The high-order sensitivity matrix method was used to effectively compensate for the wavefront aberration of a telescope with large misalignment. Verified through experiments and simulations, our results showed that SM adjustments are capable of compensating forthe defocus, astigmatism, and coma; further, the Zernike coefficients could be compensated to within a value of 0.05. Then, we demonstrated the feasibility of robotic SM support structures.  
Due to the limitations of the current experiment conditions, this paper used the Stewart platform instead of the robotic secondary mirror truss to conduct an a priori experiment. The experiment has verified the correctness of the compensation method proposed in this paper, but further work is needed in the analysis and experimental verification of the robotic secondary mirror truss structure. In view of the ideas proposed in this article, we will concentrate on the kinematics and dynamics of the robotic secondary mirror truss. We will build the robotic secondary mirror truss experiment platform for further verification as well.  
Therefore, the vehicle-mobile telescope using the secondary mirror truss in the form of robotics can highly improve the observation performance, more so than the original structure, while ensuring the mobility of transportation. In addition, since the secondary mirror can be moved through the robotic truss, the disassembly and replacement of the secondary mirror becomes more convenient. If the secondary mirror is replaced with a lens group, the telescope can be switched to the main focus system, which provides the possibility to switch between large field of view and high-resolution form.  
Conceptualization, R.W. and F.W.; methodology, R.W.; software, R.W.; validation, R.W., H.W. and X.S.; formal analysis, R.W.; investigation, X.S.; resources, R.W.; data curation, R.W.; writing--original draft preparation, R.W.; writing--review and editing, R.W. and F.L.; visualization, X.S.; supervision, R.W.; project administration, F.W.; funding acquisition, Y.C. All authors have read and agreed to the published version of the manuscript.  
This work is supported by Youth Science Foundation of the Chinese Academy of Sciences (CAS) (No. 11803035), National Key R&D Program of China (2017 YFE0102900), Youth Innovation Promotion Association of the Chinese Academy of Sciences (2016198), National Natural Science Foundation of China (NSFC) (11673080, 11403022), Jilin Science and Technology Development Program (20180520171 JH), the Youth Innovation Promotion Association CAS (No.2020221), and the Norman Bethune Medical engineering and equipment center under Grant BQEGCZX2019042.  
The authors declare no conflict of interest.