The Research Of High-precision Thermal Error Compensation Based On Radio Telescope Actuators Cluster

Xinjiang Qitai 110 m omnidirectional movable radio telescope will become the world’s largest omnidirectional movable radio telescope.Xinjiang 110 m radio telescope needs to install more than two thousand actuators on the active main reflecting surface.As a high-precision displacement device,the actuator is an important device to maintain the shape and accuracy of the active main reflecting surface of the radio telescope.The actuators to be used in Xinjiang 110 m radio telescope need to meet the accuracy requirements of ±15μm in the temperature range of-40°C to 60°C.Therefore,it is necessary to establish a thermal error model for the actuator to predict the change of the actuator displacement,and on this basis,perform active displacement control compensation to ensure that the actuator can meet the positioning accuracy requirements.First,select a single actuator to perform thermal error compensation control for single position and full temperature range.The actuator model is simulated to understand the approximate range of the actuator’s thermal error under steady-state and transient-state,and use this to guide the actuator’s thermal error compensation experimental program.It is necessary to combine the basic requirements of the model and the significance test,and select the most suitable point from the 16 temperature measurement points on the actuator;then use the gray prediction theory to establish the thermal error model of the actuator;The actual situation is to modify the model.Experiments show that for the single-stroke position,the established thermal error model can guide the active displacement control compensation of the actuator,so that the actuator can achieve a positioning accuracy of±4μm within the required temperature range of-40°C to 60°C.Furthermore,it is necessary to perform thermal error compensation control for the full stroke and full temperature range of the actuator.The thermal error compensation model is verified and revised for all stroke points of the actuator,and cubic spline interpolation is used to obtain a complete thermal error compensation control model,and make the whole achieve a positioning accuracy of ±5μm.Finally,it is necessary to perform thermal error compensation control for all the actuators of the Xinjiang 110 m radio telescope.First,the concept of actuator clusters is established,and based on the experimental thermal error compensation model,a thermal error compensation model with full stroke and full temperature range guided by key factors is proposed.After theoretical analysis,the parameters are identified through experiments,and the thermal error compensation model of the radio telescope actuator cluster is obtained.On the basis of the model,fuzzy control is used to fine-tune the error.After that,a new actuator was used for verification,and the new actuator reached a positioning accuracy of ±10μm over the entire range.