Model Test Study Of FAST Feed Support Cabin Cable System

This paper is based on the Five-hundred-meter Aperture Spherical Telescope(FAST) project as its application background. Several key mechanical problems of the feed support system are reviewed and discussed, which is one of the key technologies of the FAST. The main contents are included below as the three parts:In the first part, the risk of overturning of the focus cabin of FAST telescope is discussed. First cabin overturning is theoretically analyzed and then its result is verified via experiments on a 3m down-scaled model of the cabin-cable system. To solve the critical angle of cabin overturning, an object function of the cabin tilt is established, based on the static equilibrium equations, the limits to cable tension and cabin orientation as the constraint conditions. Newton iteration Method is employed to obtain such an optimal solutions of overturning angle. Meanwhile the effect of the center of gravity(COG) of the cabin on critical overturning angle is also considered and tested. Test results show good consistency with the theoretical analysis. Finally the critical overturning angle of cabin is calculated for the prototype and its distribution is obtained on the whole focal surface. The result shows the normal cabin tilt is much less than its critical overturning angle, so it is safe.In the second part consists of two parts: 3m down-scaled model experiments are conducted in order to study the damping characteristic of the cable driven parallel mechanism. The effects of different connection styles between the cabin and cables on the system damping, the counterweight of cable, the balance weight of six parallel flexible steel cables are compared; Based on this conclusion, a method to improve the dampers between the cabin and the cables is advanced.The third part focuses on the cable drive system of the feed supporting system, control principle and implementation method of the rope driving control system is introduced, and tests were carried out on the 3m down-scaled model, through the analysis of process control data, the control accuracy under different working conditions is obtained, which prove the reliability of the existing control system.The main innovations are followed as below: 1) the critical overturning angle of cabin is calculated for the prototype and its distribution is obtained on the whole focal surface, which offers a reference for engineering of FAST.. 2) A design to increase the damping of the FAST cable driven parallel mechanism is put forward. 3) The control precision of the cable driving control system was verified, proves that the control precision meets the requirements of FAST.