MEMS-IMU for Personal Positioning in a Vehicle - A Gyro-Free Approach

Up to now, personal self-contained sensor research has concentrated on navigation systems that include a gyro triad. Due to the challenges associated with microminiaturization of gyroscopes, it is unlikely that inexpensive gyroscopes suitable for handheld applications will be available in the near future. In this paper the potential use of a gyro-free system for personal navigation is discussed. The system analyzed herein consists of an off-the-self 3D magnetometer, a 3D accelerometer and a barometric altimeter. The application of the proposed sensor system to personal navigation for use in a vehicle is discussed. One plausible scenario would be to use GPS intermittently to conserve power, which is an important issue for handheld devices. Between updates, the sensor-based solution would maintain position and draw little power. As the unit must portable, the system must function independently of the odometer and other vehicle sensors. This is a clear drawback, since an odometer would provide better velocity information than acceleration integration. The sensor setup was tested in a variety of conditions with known reference trajectories provided by GPS. The errors due to insufficient attitude information were found to be large, but the sensor-based solution was better than the linear estimation of tracks between GPS data points. From the test results, it can be concluded that in this environment, the system can provide a position solution when GPS is turned off for short time intervals. However, during periods without GPS, orientation of the system must be maintained. Below a certain level of vehicle dynamics, it was found that gyro-free navigation fails.