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Calibration-by-Pivoting: A Simple and Accurate Calibration Method for Magnetic Tracking System

Calibrating the magnetic sensor array is an inevitable but troublesome process before using it for tracking intra-body objects such as wireless capsule endoscope (WCE). Existing calibration methods generally require many samples with prior known pose information of the magnetic target, and then the unknown parameters can be estimated by minimizing the pose error. Aiming to simplify the calibration process, we propose a calibration-by-pivoting (CbP) method which does not require any predefined poses of the magnetic target. After mounting a magnet on the top of a pointed tool, the CbP method only requires the tool pivot at an arbitrary position within the measurable range of the array. Using the measured magnetic field data from the pivoting process, the proposed algorithm iteratively updates the unknown parameters by utilizing the constraint of the sphere determined by the calibration tool. Experimental results have shown that the magnetic sensor array can achieve good positioning and orientation accuracy after applied the proposed calibration method.