Accuracy Enhancement and Determination of Nonlinear Coefficients of MEMS Accelerometer Using Centrifuge Test

In order to increase the accuracy of inertial navigation system and improve its performance, it is necessary to calibrate the inertial measurement unit (IMU). Under high acceleration levels, where acceleration is greater than linear operation area of accelerometer, input-output relationship of accelerometer is deviated from its linear form determined in the earth’s gravitational field (1g). In other words, there are nonlinear terms in input-output relationship of the accelerometer in each axis which account a large portion of accelerometer’s output under high acceleration levels. Main purpose of this paper is to estimate the coefficients of these nonlinear terms so that the input of the accelerometer compensated using these coefficients and the output of accelerometer get close to real input as much as possible. A centrifuge is used to produce high acceleration levels (greater than 1g) and these accelerations are used as reference in accelerometer calibration. In this paper, linear and nonlinear coefficients of an accelerometer(x axis) of a low cost MEMS triad accelerometer are estimated. The linear coefficients are estimated using continuous calibration method in the earth s gravitational field (1g) and the nonlinear coefficients are estimated using centrifuge test for accelerations between 0 and 16g. Also the adequacy of the nonlinear model is evaluated. The errors of linear and nonlinear models are compared together using Mean Square Error (MSE) criterion to evaluate accuracy of two models. Results show that the nonlinear model improves measurement accuracy by 11.7%.

کلیدواژه ها:

Accelerometer calibration ، nonlinear coefficients ، high-g acceleration ، least squares ، kalman filter