Research: MEMS IMU carouseling for ground vehicles

Micro-electromechanical system (MEMS) gyroscopes have advantages for orientation sensing and navigation as they are small, low cost and consume little power. However, the significant noise at low frequencies produces large orientation errors as a function of time. Controlled physical rotation of the gyroscope can remove the constant part of the gyro errors and reduce low-frequency noise. As adding motors for this would increase the system cost, it would be advantageous to attach gyros to a rotating platform that is already built in the vehicle. The authors present theory and results for novel navigation systems where an inertial measurement unit (IMU) is attached to the wheel of a ground vehicle. The results show that a low-cost MEMS IMU can provide a very accurate navigation solution using this placement option. It has two clear advantages:

• Wheel motion removes the constant bias of the gyroscopes
• Distance traveled can be estimated from accelerometer data.

For low-dynamic ground vehicles, this approach is superior to conventional dead-reckoning with an odometer when a low-cost MEMS gyro provides the heading information. Test results are obtained using a vehicle driving slowly on a relatively smooth surface, and the use of an accelerometer for wheel phase-angle tracking was fairly accurate for this purpose.

For higher vehicle dynamics and gravel roads, the accelerometer data will be contaminated with significant centripetal and motion-caused accelerations. For that purpose, the use of high-range gyro with the sensitivity axis perpendicular to the wheel plane should be considered to complement the accelerometer-based (bias-free) observations. Applying this method to passenger cars at highway speeds would require an IMU with wide bandwidth, and solving the challenges at high speeds remains a future research topic. In addition, there is a requirement to bring electricity to the wheel and the need for wireless data transfer. As the major error source of MEMS gyros is eliminated, the method opens new applications for inertial navigation systems. In addition, there is a very large potential for wheel-based sensing in general, not restricted to Earth surface or navigation applications.

Published in IEEE Transactions on Vehicular Technology, June 2015.