I. Introduction
Electromagnetic tracking (EMT) technology has been widely used in many areas, such as human-machine interaction [1], vehicle guidance [2], robotic surgery [3]–[9], and image guided interventions [10], [11], among others. This method is mainly based on the accurate mapping of the magnetic field generated by magnetic sources [12]. Based on the magnetic sources, there are two types of magnetic tracking: permanent magnet based tracking [13]–[20] and the quasi-static electromagnetic coils based tracking [3], [21]–[29]. Compared with permanent magnet based tracking, the electromagnetic (EM) method has the advantages of anti-interference and a larger working space. Orthogonal coils are the mostly used tools to serve as the transmitting coils and the sensing coils in the EMT methods as shown in Fig. 1. Two different estimation methods can be used in EMT, one of which is direct estimation and the other being rotation based estimation.
Electromagnetic tracking method. A set of triaxial orthogonal transmitting coils is often served as the magnetic field source, which is sensed by a set of triaxial orthogonal sensing coils. The relative position and orientation parameters between the transmitting coils and the sensing coils can be estimated with the sensing signals.