Development of attitude reference system using extended Kalman filter based on ARM and 16445 Isensors

Background: Modern micro-electromechanical systems (MEMS) technologies provides the moderate-cost and miniaturized solutions for the development of attitude reference system. Using highly­ integrated inertial measurement units (IMUs) provided by ADI Company, a mini attitude reference system was developed for precise agricultural control and autonomous vehicle.

Methods: The attitude reference system is composed of an ARM processor (STM32F446RC) and ADIS16445 iSensor® which includes triaxial gyroscopes and triaxial accelerometers. The raw sensors data was sampled by STM32F446RC processor through SPI interface. A second order autoregressive (AR) model was developed to model the random draft error of MEMS gyroscopes. By using extended kalman filter (EKF), the sensor fusion algorithm was implemented for the attitude reference system. The AR model was incorporated into the EKF algorithm and the measurement noise covariance was estimated from the AR model, which limited the fine tuning of noise covariance to the process noise covariance only. To verify the performance of the gyroscopes, accelerometers, and the attitude reference system, the tests were carried out on SGT320E three-axis turntable platform and LOVOL TD904 tractor.

Results: Test results showed that the robust performance of gyroscopes and accelerometers could be obtained with stable supply voltage. Typical accuracy of attitude reference system in static was 0.03 degree with max error 0.1 degree, and the typical dynamic accuracy was 0.7 degree with max error 1 degree. The developed mini attitude reference system had good performance on tractor navigation, so as to autonomous vehicle.

Discussions: Environment temperature will affect the performance of micro-electromechanical devices and the zero bias of gyroscopes and accelerometers, which will need to estimate when applying extended kalman filter.

Conclusion: This paper developed a mini attitude reference system with stable performance and high precision which was suitable to applied in precise agricultural machines and its implements.