电磁跟踪系统磁场畸变规律数值模拟及校正方法

电磁跟踪系统参数定位精度易受工作环境中金属物体的影响。为了研究由于金属干扰导致电磁跟踪系统空间磁场的畸变规律，采用基于消息传递模式的网络并行计算系统和区域分割技术实现了并行时域有限差分算法。引入快速傅里叶变换算法，克服了系统激励源频率较低难以模拟的困难。通过对磁场畸变规律的研究，引入误差校正矩阵，通过修正发射矩阵进而校正磁场畸变引起的目标参数定位误差。采用正交多项式拟合的算法求解误差校正矩阵，数值模拟结果验证了校正方法的正确性，可以明显提高磁场畸变时系统参数的定位精度。磁场畸变规律的数值模拟，降低了系统实时数据采集的工作量，提高了系统校正方法检验的快速性。

Numerical simulation and calibration of electromagnetic tracking system magnetic field distortion

The accuracy of electromagnetic tracking system is impaired seriously by distortions of magnetic fields caused by metals which are omnipresent at real sites. To study the rules of magnetic distortion, the parallel finite difference in time domain (FDTD) algorithm is presented on a distributed network. The message passing module and space decomposition technique are introduced. In FDTD application，simulation of low frequency exciting source is very difficult. The fast Fourier transform (FFT) algorithm is introduced to analyze the magnetic field characteristic in some special frequency. Calibration arithmetic is proposed by modifying the transmitting matrix based on the concept of error calibration matrix. This matrix is calculated by the method of orthogonal polynomial fitting. The simulation results validate the correction of the calibration arithmetic, which improves the accuracy of the electromagnetic tracking system. The efficiency of calibration validation is improved by decreasing the work of data collection, which is based on the results of numerical simulation.