The tertiary mirror positioned assembly (M3PA) of the thirty meters telescope (TMT) is the largest tertiary mirror pointing system in the world. The tracking and pointing performance of M3PA is better than any other telescopes which have been built, and the working condition is even worse, so the designers face an enormous challenge. The tracking system includes the bottom rotator shaft and the tilt shaft. The study of this paper focuses on the tilt shaft. There are mainly three forms. The first form is one end fixed with the other unrestrained in axial direction. The second form uses two pairs of angular contact ball bearing. The last form lays two tape roller bearings. All of them can meet the requirements when the M3PA is vertical. But the first one becomes invalid when the M3PA is horizontal. We pay our attention on the study for the second arrangement method.. This bearing arrangement can produce a good stiffness, and increase the first modal frequency to 15.1Hz. In addition, some analysis were down to study the load applied on the balls. The results show that the maximum load is up to 5000N with the stress of 2300MPa.
TMT Tertiary Mirror System (M3S) is required to be able to track and point. It should rotate with the observing object. In this article, the schemes of Tertiary Mirror supporting assembly and position assembly are introduced. Then, the static and dynamic performance of Tertiary Mirror System has been analyzed. It is shown that, the maximum deflection is 1.024 mm, the maximum stress is 138.91MPa when gravity is affecting. The security of M3S can be assured when telescope is working at all required positions. The first nature frequency is 15.39Hz, the requirement 15 Hz has been satisfied. In addition, the response to earthquake has been estimated primarily. Results shows that when earthquake with mean return time 200 year happens in three directions simultaneous, or earthquake with mean return time 1000 years happens, the lateral support will be destroyed. Protection measures should be considered. Conclusions in this article are useful guides for the M3S design.
In order to analyze the tracking performance and design the controllers for TMT-M3 control system in the design stage. This paper presents the development of the analytical model of the gear driven large telescope using the lumped mass modeling method. The analytical model includes the telescope structure, its drives, the velocity loop and position loop. First, the modal model of a flexible structure is analyzed based on the finite-element data. And the modal model is transferred into the state-space model, in continuous-time. Next, the drive model is derived, and combined into the velocity loop and position loop. Finally, the impact of the error sources on the control loop properties is simulated. According to the simulation accuracy of the analytical modeling, the analytical model can be used in implementation, such as the model-based controllers.
With the development of infrared technology and material, infrared zoom system is playing an important role in the field of photoelectric observation, the demand of infrared systems is increasing rapidly. In order to satisfy the requirement of infrared tracking imaging requirements of a car optoelectronic devices, different kinds of mechanical structure has been discussed, finally, according to the character of the optical design result, cam mechanism is adopted in zoom mechanism design, ball screw has been used in focusing mechanism design. As is known to all, cam is the key part in zoom system, the static, dynamic and thermal characteristics of the cam make great effect on the system performance because of the greater impact of the car’s shaking and a larger range of temperature changes, as a result, the FEM analysis is necessary. The static performance is all right obtained by the finite element analysis results, the cam’s first -order natural frequency is 97.56 Hz by modal analysis, the deformation of cam in the temperature difference of 80 °C is no more than 0. 003 mm by thermal analysis, which means the mechanical performance of the cam is fine. at last, the focusing mechanism has been designed, and analysis of focusing mechanism precision and encoder theoretical resolving power has been done, this mechanism has the advantages of simple transmission chain and low friction, as well as reducing the transmission error, an absolute encoder is chosen to detect the displacement of the focusing mechanism, the focusing precision is 5μm, the encoder theoretical resolving power is 0.015μm. In addition, the measurements on how to suppress stray radiation have been put forward. The experiment afterward showed that the infrared zoom system performs well, which provides lot of experience in infrared zoom system design and adjustment.