Wireless Magnetic Position-Detection System With Four Excitation Coils

For tracking position or motion of objects in small or shielded spaces, our wireless position-detection system using an LC resonant marker is considered to be effective. Generally, detection of the accurate position of the marker is difficult when reduction of the S/N ratio occurs due to the marker posture. To solve this problem, we propose a system with four excitation coils to generate four-directional magnetic fields whose components are different from each other. To evaluate this system, simulations and experiments were conducted for a single excitation coil and for four excitation coils. In the single excitation coil system, position detection was difficult for some postures of the LC marker due to the greatly reduced excitation efficiency of the marker. In contrast, in the four excitation coil system, the excitation strength of the marker was kept for every marker posture, and position detection was performed with high accuracy even when the marker was placed where the excitation was weakest. Therefore, it is possible to detect the position of the marker accurately regardless of its posture by using four excitation coils. By this improvement, our position-detection system is considered to be useful for tracking finger motion in some applications.