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 low-g 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 ±0.5° accuracy in tilt and less than ±1° accuracy in yaw angle measurement with above-mentioned methods.