Multi-objective pose optimal distribution method for the feed support system of Five-hundred-meter Aperture Spherical radio Telescope

The Five-hundred-meter Aperture Spherical radio Telescope is the world’s largest single-dish radio telescope and is located in the southwest of China. The cable-driven parallel robot and A-B rotator of the feed support system in Five-hundred-meter Aperture Spherical radio Telescope are designed to realize the theoretical position and attitude of the receiver. The feed support system is a pose-redundant and rigid–flexible coupling system; thus, the method of pose distribution between the A-B rotator and the cable-driven parallel robot impacts on the cable tension distribution and stiffness of the feed support system, which are crucial to the feed support system stability. The main purpose of this study is to examine the pose optimal distribution method for the feed support system. First, a mechanical model of the feed support system, which considers the time-varying barycenter of the feed cabin and the back-illuminated strategy of the receiver, is established. Then, a pose distribution method that ensures the position and attitude accuracy of the receiver is proposed for the feed support system. Considering the performance indices of the variance of cable tensions and the stiffness of the cable-driven parallel robot, an optimization of the rotation angles of the A-B rotator with multiple objectives is implemented using a genetic algorithm. Finally, simulations are conducted to demonstrate the effectiveness of the proposed method compared with others. Results show that the proposed approach not only ensures the attitude accuracy of the receiver but also maintains the lower variance of cable tensions and higher stiffness of the feed support system.

Pose Planning for the Feed Support System of FAST

A six-cable driven parallel manipulator and an A-B rotator in the feed support system of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) are adopted for realizing the position and pose of nine feeds. The six-cable driven parallel manipulator is a flexible mechanism, which may not be stably controlled due to a small cable tension. The A-B rotator is a rigid mechanism, and its stability and accuracy can be improved by small pose angle. Based on the different characteristics, a pose planning function is presented. The optimization target of the pose planning function is to get the smallest pose angle of the A-B rotator, and the constraint condition can reflect the controllability of the six-cable driven parallel manipulator. Then, the pose planning realization process of the feed support system is proposed. Based on the pose planning method, optimized pose angles of the feed support system for the nine feeds are obtained, which suggests that the pose angle of the six-cable driven parallel manipulator changes from 0° to 14° and the pose angle of the A-B rotator changes from 0° to 26.4°.

Dimension Optimization Design of the Stewart Platform in FAST

China is now building the largest single dish radio telescope in the world in Guizhou province, which is called Five-hundred meter Aperture Spherical radio Telescope (FAST). A Stewart platform is introduced in FAST as an accuracy adjustable mechanism for feed receivers. The main purpose of this paper is to discuss dimension optimization design method of the Stewart platform based on three optimization objective functions. The optimization objective functions can reflect the operability and accuracy of the Stewart platform, and optimization design flow is presented according to the important degree of the three optimization objectives. Finally, a set of optimized parameters is obtained, and the study in this paper provides a basis for the coming optimization the feed support system for FAST in the next step.