| Three-axis accelerometers are widely used in the inertial navigation,space exploration and geophysics.As the requirement for acceleration detection accuracy continues to increase,the role of accelerometers for high-precision detection has become increasingly prominent.Based on the gravity field indexing device,this paper studies the corresponding test methods for three-axis accelerometers with different precisions,and analyzes the interference factors in the calibration process.Subsequently,the accelerometer’s basic performance indicators such as the scale factor,the bias and the orientation are obtained,through the experiments.At first,the test methods of the three-axis accelerometer with an input range from 1 g to tens of g are investigated and analyzed.The test method based on the two-axis indexing head is selected in this paper.The accelerometer is performed by multi-position rotation in different tilt planes,whose tilt angles range from 0° to 90°.By analyzing the installation errors of the indexing head and the accelerometer,the calibration model equation of the accelerometer is determined,and the bias,the scale factor and the non-orthogonal angle between the three axes are separated according to the harmonic analysis method.Our homemade inertial navigation three-axis accelerometer is used in the test.The results show that the uncertainty of bias is 0.8 mg,the uncertainty of scale factor is 0.08 m V/g and the uncertainty of non-orthogonal angle is 1 mrad.On this basis,for the self-developed three-axis high-precision accelerometer used in the microgravity environment,a method for calibration on the ground has been developed.The input range of this type of accelerometer is about mg,much less than 1 g.This paper uses the method of multi-position rotation at a small tilt angle to test the basic parameters of the accelerometer.During the test,there are challenges solved as follow: accelerometers for the three axes cannot work at the same time in the ground gravity field;the slight deviation of the zero reference surface of the turntable from the horizontal plane will have adverse influences on the measurement when the rotating surface is inclined at a very small angle;the misalignment angle of the sensitive axis deviating from the rotating surface is difficult to measure;the accelerometer responds to high-order error terms that have a great influence on the results.These challenges are solved respectively by using the scheme as below:each axis is tested independently with different attitudes,and then combined to obtain a unified spatial relationship;the zero reference surface is accurately measured by the method of multi-position rotation of the level meter;the misalignment angle of the accelerometer is obtained by tilting the dual-axis turntable around the trunnion to multi positions,and uses this misalignment angle to correct the bias;high-order terms is added into the model equation to reduce the error.Taking a commercial three-axis accelerometer with input range>1 g as a test object,the results of the conventional 90°gravity field tumble method and multi-position tilt method and the small-angle tilt plan rotation method were compared through experiments,and the feasibility of the proposed method was verified.Based on the validation,the basic performance parameters of our home-made high-precision accelerometer were tested,and the uncertainty of bias is 0.2 mg,the uncertainty of scale factor is 0.1 m V/g and the uncertainty of misalignment is 0.2 mrad.Using the spatial relationship between the shell and the fixture,measured with the coordinate measuring machine,the spatial relationship of each axis of the three-axis accelerometer relative to the shell is obtained through coordinate transformation.In summary,this paper develops a test plan of high precision three-axis accelerometer based on the test of the three-axis accelerometer with a large input range,and successfully verified it. |
