Research On Position Actuators In Large-aperture Segmented Mirror Telescope

Astronomical telescopes are an important tool for mankind to expand their field of vision.The method of increasing the aperture of the telescope can increase the observation distance and accuracy of the telescope.However,it is difficult to directly manufacture a mirror with an excessively large aperture,and the overall deformation of the mirror will increase accordingly,which seriously affects the performance of the telescope.The segmented mirror technology uses several small-diameter sub-mirrors to splice into a large-aperture main mirror,and each sub-mirror is supported and adjusted by several micro-position actuators.Currently,there is no domestic manufacturer that specializes in producing micro-position actuators for astronomy.Although foreign micro-position actuators have good performance,they are very expensive when applied to segmented mirror telescopes on a large scale.Therefore,the research goal of this article is to build a complete set of position actuator system for segmented mirror telescopes with high stability and high precision,which can be used in narrow spaces within a certain budget cost.The main work of this article is as follows:(1)According to the principle of ampere force and referring to the design structure of a variety of mature voice coil motors,a new type of high-precision voice coil motor is designed and built.The voice coil motor adopts a symmetrical structure design,and adopts an air-core sliding rod as the coil support,and the magnetic guide rod is inserted into the sliding rod.The overall structure is compact and easy to disassemble;(2)Design and build an active unloading device suitable for segmented mirror telescopes.The device is composed of a stepping device and a compensation device.The stepping device is responsible for the pre-adjustment of the telescope mirror body,and the compensation device is responsible for loading the weight of the mirror body and eliminating wind disturbance,etc.And the active unloading device is coordinated with the voice coil motor system function to ensure the sequence of adjusting the telescope mirror body;(3)Using STM32 single-chip microcomputer system,KEIL5 development platform and pulse-width modulation technology(PWM),design and build a drive control system suitable for large-aperture segmented mirror telescope position actuator,mainly including: position actuator control module,voice coil motor drive module,active unloading device drive module,etc.Realize precise step control of voice coil motor and active unloading device;(4)The laser Doppler measurement system(LDDM)and force sensor are used to measure the position and force value of the voice coil motor system and the active unloading device respectively,and then perform data analysis and error analysis based on the measurement results.The experimental results show that the position actuator system has good linearity,the maximum output error value of the voice coil motor thrust is 6.9825 m N,the maximum output error value of the position is 10.4629?m;the maximum output error value of the thrust of the active unloading device is 58.7484 m N,the maximum error of the position output is 45.5817?m;in addition,this position actuator has good stability,a more compact structure and a simple control method.