Orientation Precision Monitoring and Homing Strategy of the Subreflector Adjusting System for 65 Meters Radio Telescope

The subreflector's adjusting mechanism of the 65 meters radio telescope in Shanghai observatory is a Stewart parallel robot. In order to find out the problems of this robot's precision decline in time, caused by mechanical wear or error accumulation, inclinometers are used to measure the orientation of the mobile robot platform. Comparing the RMS (root mean square) error of the measured platform orientation with the expected orientation precision, thereby the user can judge whether maintenance or homing is required. For improving the easy maintenance of the parallel robot, two ways of homing are set up, by using photoelectric sensor and magnetic linearity displacement transducer (MLDT) respectively. The principles of the two ways of homing are analyzed, particularly that of calibrating the precision of the photoelectric sensor and the MLDT by using the homing operation. What's more, different conditions under which the parallel robot needs homing operation are summarized, and the corresponding homing control strategies are proposed. Test shows that the homing strategy proposed is an effective tool to solve homing problem of the parallel robot.