Attitude measurement of driver's head based on accelerometer and magnetoresistive sensor

A head attitudes measurement system based on 3-axis micro-accelerometer and 3-axis micro-magnetoresistive sensor is designed and developed using for thermal imager setup of night-driving vehicle. The three attitude angles, i.e. pitch, roll and yaw, of driver's head are estimated relative to the driving vehicle in real time. In this system, the 3-axis micro-accelerometer detects the gravity field and the 3-axis micro-magnetoresistive sensor detects magnetic field. Euler orientation cosines matrix conversion theory and the relative algorithm are applied to the attitude calculation. Different from the conventional measurement to the earth, the reference coordinate system is mobile vehicle here. For this system, the geomagnetic field will be a disturbance, thus the oriented uniform magnetic field is built by permanent magnets and activity mechanical arms to eliminate the negative effect of the geomagnetic field. Moreover, the kinematical accelerations induced by the vehicle's accelerating, decelerating or vibrating are considered as disturbances, and a dual-layer filter is designed to deal with them. Finally, the experiments on vehicle are carried out, and the three-dimensional attitude angles of the driver's head relative to the driving vehicle are measured. Results prove that this measuring system not only has small size and low cost, but also has quick response and high reliability.