A Hybrid MEMS-based Navigation System and Its Numerical Analysis

Inertial navigation systems have many potential uses beyond air-and spacecraft applications. The novel aspects of a navigation system based on micro electro-mechanical systems (MEMS) compared to the conventional large-scale system are small size, light-weight, low power consumption, and low cost by the inclusion of silicon microsensors with on-chip functionality such as micromachined rate gyroscopes, accelerometers, and so on. However, the performance associated with these low-cost MEMS sensors is generally not satisfied. Therefore, a conventional strapdown method based on integrating angular rate to get attitude will inevitably induce long-term drift. For eliminating this accumulative error and thus using the navigation system for a long-duration mission, a hybrid configuration by integrating a MEMS-based attitude and heading detector with the conventional navigation system is proposed in this paper. The attitude and heading detector is composed of 3-axis MEMS accelerometers and 3-axis MEMS magnetometers. With an absolute algorithm based on the gravity and the earth magnetic field rather than the integral algorithm, the attitude detector can obtain absolute attitude and heading estimation without drift errors so as to be used to perform adjusting the attitude and orientation of the strapdown system. The computation process of estimating the position and attitude using the hybrid system is depicted in the paper firstly. Then the transformation errors of the computation, such as skew, scale, and drift errors, are analyzed. Finally it is verified by both of formula analysis and test results that the accumulative errors are effectively eliminated via this hybrid scheme.