Improvements to magnetic tracking system for Virtual Reality

摘要

Magnetic tracking system is widely used in a Virtual or Augmented Reality system to track the orientation and position of an object in space. When being applied in medical applications such as surgical navigation or medical image registration, accurate 6 DOF (Degree-of-Freedom) tracking is especially important. In order to compensate the influence of metal object and magnetic fields in the surrounding environments on the accuracy of the measurements, an AC magnetic tracking system whose orientation is obtained with the output of 3-axis orthogonal magnetic sensors and 2-axis accelerometers is designed. On the basis of analyzing the influence of environmental magnetic fields on the measurement accuracy of heading, a compensation algorithm is presented, which fits the outputs of the magnetic sensors to an ellipse with the principle of least square and rotation invariant and calibrates the heading with the parameters of the ellipse to rotate and scale the measurement results. Compared with the existing approach, the proposed method can effectively compensate the influence of environmental interference when the magnetic tracking system moves in horizontal plane and can also be applied in the applications with continuous movements. Experimental results show that the proposed method can effectively compensate environmental interference and improve the tracking accuracy.