School of Electronic Information and Electrical Engineering, Huizhou University, Huizhou 516007, China.
Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051, China.
Sensors (Basel). 2018 Nov 27;18(12):4157. doi: 10.3390/s18124157.
Attitude measurement is an essential technology in projectile trajectory correction. Magnetometers have been used for projectile attitude measurement systems as they are small in size, lightweight, and low cost. However, magnetometers are seriously disturbed by the artillery magnetic field during launch. Moreover, the error parameters of the magnetometers, which are calibrated in advance, usually change after extended storage. The changed parameters have negative effects on attitude estimation of the projectile. To improve the accuracy of attitude estimation, the magnetometers should be calibrated again before launch or during flight. This paper presents a fast calibration method specific for a spinning projectile. At the launch site, the tri-axial magnetometer is calibrated, the parameters of magnetometer are quickly obtained by optimal ellipsoid fitting based on a least squares criterion. Then, the calibration parameters are used to compensate for magnetometer outputs during flight. The numerical simulation results show that the proposed calibration method can effectively determine zero bias, scale factors, and alignment angle errors. Finally, a semi-physical experimental system was designed to further verify the performance of the calibration method. The results show that pitch angle error reduces from 3.52° to 0.58° after calibration. The roll angle error is reduced from 2.59° to 0.65°. Simulations and experimental results indicate that the accuracy of magnetometer in strap-down spinning projectile has been greatly enhanced, and the attitude estimation errors are reduced after calibration.
姿态测量是弹丸弹道修正的关键技术。由于磁强计具有体积小、重量轻、成本低等优点，因此被用于弹丸姿态测量系统。然而，在发射过程中，磁强计会受到火炮磁场的严重干扰。此外，经过长时间储存后，磁强计预先校准的误差参数通常会发生变化。这些变化的参数会对弹丸的姿态估计产生负面影响。为了提高姿态估计的精度，在发射前或飞行过程中应对磁强计进行重新校准。本文提出了一种针对旋转弹丸的快速校准方法。在发射现场，通过三轴磁强计进行校准，基于最小二乘准则的最优椭圆拟合快速获取磁强计的参数。然后，使用校准参数来补偿飞行过程中的磁强计输出。数值仿真结果表明，所提出的校准方法可以有效地确定零偏、标度因数和对准角误差。最后，设计了一个半物理实验系统，进一步验证了校准方法的性能。结果表明，校准后俯仰角误差从 3.52°降低到 0.58°，滚转角误差从 2.59°降低到 0.65°。仿真和实验结果表明，磁强计在捷联式旋转弹丸中的精度得到了显著提高，校准后姿态估计误差降低。
