An Improved 6-D Pose Detection Method Based on Opposing-Magnet Pair System and Constraint Multiple Magnets Tracking Algorithm

Magnetic tracking method is mainly based on sensing of the magnetic field generated by the magnetic source. Usually a small permanent magnet is used as the magnetic source, and magnetic dipole model is used to estimate the magnetic field. The disadvantage of this approach is that only 5-D pose information can be estimated, but the spin rotation with respect to the direction of magnetic moment cannot be detected. In our previous work, we proposed a novel 6-D (3-D position and 3-D orientation) pose detection method, which was based on an opposing-magnet pair system. The disadvantage is that different rotational parameters may lead to the same pose result due to the symmetric structure of object magnets. In order to solve this problem, we propose an improved 6-D pose detection method in this paper, which is based on a novel constraint multiple magnets tracking algorithm. Two magnets of different sizes with opposite magnetic directions have been combined together to serve as the tracking target. By applying the constraint multimagnet tracking algorithm, 5-D pose of each magnet can be obtained. Therefore, we can estimate the missing spin rotational information according to the relative movement between these two magnets. Experimental results verified the feasibility of the proposed method. The average position error is 2.3 mm and the orientation error is 4.36 degrees, when the volume ratio between these two magnets is 1:1.5.