Calibration and Compensation of Inner Lever Arm for Accelerometer
Pan Jiang, Wei Gao, Guochen Wang, Qian Li, Ya Zhang, Harbin Institute of Technology, China
Alternate Number 2
In the study of many strapdown inertial navigation problems, the SINS measurement module (SIMU) is treated as a "point" measurement component, but in reality the SIMU is, of course, a certain size. If the SIMU is regarded as rigid, the angular velocity of each point above the SIMU angular motion is the same, so theoretically the three angular velocity measurement sensors in the SIMU - the mounting position and orientation of the gyro can be arbitrary. Their sensitive axes are not parallel to each other, after calibration can be achieved SIMU space three-dimensional angular velocity measurement. However, in the case of angular motion, the acceleration at each point on the SIMU is generally different from each other, that is, due to the physical dimensions of the three accelerometers and the actual mounting position, they are measured at different points on the SIMU acceleration, if these accelerations are considered as inertial navigation from the output of the ideal "point" measurement component, will cause the navigation error in principle. Therefore, it is very important to study the calibration and compensation of the error of the arm of the accelerometer to improve the dynamic performance of the inertial navigation system.
The effect of the inner lever arm (in some literature called the Dimension Effect). The main contents of this paper are the analysis of the causes and laws of the inner lever arm effect, and put forward the corresponding compensation measures. The effect of the inner lever arm is due to the virtual normal acceleration integral and virtual tangential acceleration integral can not be completely offset. The drift rate of the inner lever arm is independent of the angular vibration center and is proportional to the length of the inner lever arm and is proportional to the square of the vibration frequency. The method of compensating the lever arm effect is to convert the acceleration measurements at the sensitive point of the accelerometer to their sensitive axis. If the SIMU's accelerometer sensitive axes are not perpendicular to each other or do not intersect at one point, the analysis and compensation process of the internal arm effect is complicated, but this problem is unavoidable in SIMUs with multiple accelerometers redundant configurations. This article also made a more in-depth analysis of this situation
We first analyze the causes of the error of the inner lever arm, and then establish the calibration model of the error of the inner lever arm. It is found that the parameters of the inner lever arm can be identified by the navigation speed error. The six internal arm error parameters (assuming one of the accelerometers is the origin of the body coordinate system, so the arm error in both directions is 0) are added to the system-level calibration state variable. We found that through the sixteen-position rotation program can be completed lever arm error calibration. After completing the calibration and compensation of the arm error in the accelerometer, we carried out the high dynamic experiment(angular acceleration is relatively large).The experimental results show that the speed error of the navigation system has been improved remarkably, and the validity of the calibration method of the internal arm error parameters and the compensation method are verified.