Simulation And Error Analysis Of Six Degrees Of Freedom Adjustment Mechanism Of Optical Telescope Secondary Mirror

In order to improve the imaging quality of optical telescopes,the adjustment and correction of the position errors between the optical axes of the primary and secondary mirrors are supposed to make.The secondary mirror adjustment mechanism are required to have five degrees of freedom except its own rotation,and the accuracy of the adjustment mechanism are supposed to reach the order of magnitude of micrometers and angular seconds.Since the position error is in mm and minitue of arc,the adjustable range of the mechanism is required to reach mm and minitue of arc level,and the structure of the adjustment mechanism should be as compact as possible.This paper applied in telescope mirror the six degrees of freedom of adjustment mechanism,the six degrees of freedom Stewart platform is put forward with universal hinges between the platforms and the actuators which can be seen as the UCU type.The complete analysis of the kinematics of the mechanism is completed through vector analysis and Newton iteration,and the work space of platform under a given posture is achieved by polar coordinate method.In order to verify the analysis of kinematics of the mechanism,the program of analysis of the kinematics was written in MATLAB,and the verification was established by ADAMS,in which the dynamic simulation was carried out by spline curve method.A complete simulation model based on Newton iteration method is established through the interface between ADAMS and MATLAB.In order to study the influence factors of the position error and the initial distribution of the position error during the preliminary design,the position error of the platform with six degrees of freedom was analyzed theoretically first,and then the error model was verified by the forward kinematics.The monte carlo simulation method was used for the analysis of the structure parameter error of secondary adjustment mechanism,and according to the analysis of the sensitivity of the parameter error of each structure,the optimization design was completed to reduce the influence to the position error of the structure paremeter error.The error distribution was accompulished to ensure the position accuracy for a given maximum allowable position.The actuator of the secondary mirror adjustment mechanism of six degrees of freedom was designed.The model of the actuator was built in the laboratory environment,and its positioning accuracy was tested,which verified the feasibility of realizing the positioning accuracy requirements.