A Calibration Method for MEMS Inertial Sensors Based on Optical Tracking

A MAG-muIMU which is based on MEMS accelerometers, gyroscopes and magnetometers has been developed for real-time estimation of human hand motions. Appropriate filtering, transformation and sensor fusion techniques are combined in the ubiquitous digital writing instrument (UDWI) to record the handwriting on any surface. However, because of the sensors´ intrinsic biases and random noise such as circuit thermal noise, a calibration system that provides good reference measurement parameters must be used to compare the output of the MAG-muIMU sensors. We propose here a novel idea to calibrate three-dimensional linear accelerations, angular velocities and space attitude through optical tracking techniques. The optical tracking system (OTS) developed by our group consists of two parts: 1) 2D trajectory calibration that is used to obtain linear accelerations of the UDWI in a particular frame defined by us; 2) multiple camera calibration that is used for attitude calibration of the UDWI. An essential relationship to transform reference frames and angular velocities can be guaranteed after real-time attitude calibration. Hence, the entire nine-dimensional output of the MAG-muIMU can be rectified according to these more accurate data obtained from optical tracking.