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The motion accuracy of a platform based on two compensated flexible four-bar linkages was researched and three error sources,namely,batten size error,the sphere center distance error of ratio lever and the assembling angle between the inner and external battens were analyzed.A semi-beam model was established to analyze the deformation of the batten and the relationship between working displacement and coupled displacement.The expressions of the platform straightness error and the limiting coupled displacement error which was concerned with the platform displacement and the batten sizes were derived.Finally,an autocollimator and a high precise measuring head were used in the measurements of the platform straightness and the coupled displacement.The experimental results show that the straightness error is smaller than 1.5″and the coupled displacement error is less than 13.7 μ m when the stroke of the displacement platform is no longer than 5mm.It is proved that the platform works with high motion accuracy and the experimental result is consistent with the analysis results.

In order to meet the requirements of a tracking gimbal for the lower cost,shorter manufacture periods and higher interchangeable property,a new way of shaft transformation by using standard-bearings to replace thrust bearings was proposed.The axis error sources of using standard-bearings were explained,then according to the principles and characters of the tracking gimbal,an error eliminating method to make the axis sloshing become parallel moving was given.Finally,an experiment model of horizontal axis was designed,and the error of axis adopting zero level deep groove ball bearings was tested and analyzed by the Fourier harmonic analysis method.The experimental results indicate that the maximum error of shafting sloshing has been reduced from 6.126″ to 2.430″,which proves the the feasibility of the proposed error eliminating method.It concludes that the higher level bearings and right fixing plans can meet the precision requirements of small-scale tracking gimbals.

In order to correct the laser pointing errors caused by the axial errors for a level mounting laser transmitter system,a new laser pointing error correction model was built by using the correction method used in the pointing error correction of a photoelectric theodolite,and the error transfer behavior between shafts and optical path was investigated intensively.Firstly,the opto-mechanical structure and modeling theory were introduced,and the transformation matrixes of mirrors were presented.Then,by constructing two 3D coordinates in which the laser beam was considered as a unit vector,the laser pointing model was established by linear coordinate transformation and linear vector transformation.Furthermore,the undetermined coefficients in the laser pointing model were obtained by least square fitting.Finally,the TV tracking system whose optical axis was actually considered as an ideal one in the laser transmitter system was used to measure the laser pointing error.Experimental results indicate that the laser pointing precision of the level mounting laser transmitter system is up to 3.1″ and 9.7″ in 2 specific orbits and a zenith region,respectively,which satisfies the requirement of the system design for the accuracy.

A total pointing error correction model was built to correct the pointing errors of a level mounting theodolite.Based on the opto-mechanical structure of the level mounting theodolite,a geodetic coordinate system and a pointing coordinate system were built.Then,according to the location relationship between the two coordinate systems,the target coordinate in the geodetic coordinate system was expressed.After a total differential for the target coordinate,an equation was obtained to describe the relation between target coordinate error and longitude latitude errors of the level mounting theodolite.By considering the three shafting errors to be the major ones of the system,5 linear coordinate transformations were performed to deduce a total coordinate error equation for three shafting errors.Combined with the total differential equation,a unitive compensation model of pointing error on the three shafting errors was obtained. By linear superposition with the pointing error caused by encoder errors,the total pointing error of the level mounting theodolite was gained.Finally,46 stars scattered in sky space uniformly were selected to be measured,and the discrete values of the 46 stars' pointing errors were gained in longitude and latitude dimensions,respectively.After least square fitting,the undetermined coefficients in the total pointing error model were obtained.Experimental results indicate that the total pointing accuracy can rise from 40.1″ to 3.4″ after correction,which meets the accuracy request in a general design.