A low-cost motion tracker and its error analysis

This paper develops a physical model of an inertial/magnetic measurement unit by effectively integrating an accelerometer, a magnetometer, and two gyroscopes for lowg motion tracking applications. The proposed model breaks down the errors contributed by individual components, then determines error elimination methods based on sensor behavior and characteristics, and finally constructs a feedback loop for continuous self-calibration. Measurement errors are reduced by adopting a systematic design methodology: 1) tilt errors are minimized through a careful selection of A/D convertor resolution and by making compensation on sensor bias and scale factor; 2) heading errors are reduced by cancelling out nearby ferrous distortions and making tilt-compensation on the magnetometer; 3) errors from gyroscope measurements are eliminated via the least squares algorithm and continuous corrections using orientation data at the steady-state position. Preliminary tests for low-g motion sensing show that the motion tracker can achieve less than ±0.5º accuracy in tilt and less than ±1º accuracy in yaw angle measurement with above-mentioned methods.