Attitude Estimation Using an Accelerometer and Rate Gyro Based Device

In this paper, a method for estimating aircraft att itude is proposed using an accelerometer based device combined with a gyro based sensors for estimating rotational rates. The device incorporates a series of low-cost accelerometers mounted in a circular arc to determine the local gravitational field vector. Once the local gravitational field vector is determined the orientation of the device can be est imated. However, the attitude estimate occurs at discrete time values and therefore is not a continuous estimate. Rate gyros measurements can be integrated producing continuous attitude estimates. However, the attitude estimates produced by rate gyro integratio n tend to drift over time due to drift and bias inherent to the rate gyro sensor. In this pape r, a method for re-initializing the initial condition of the rate gyro integration estimate is proposed using the discrete attitude estimate found from determining the local gravitati onal field vector. In an addition, the rate gyro biases and drift may be computed with knowledge of attitude at discrete intervals and subtracted from the rate gyro measurements producing a more accurate continuous attitude estimate. For this study, pitch angle estimates are only considered to analyze the feasibility of the proposed method but may be easily extended i ncluding the remaining degrees-offreedom. Simulation results of the proposed device are presented including real-world sensor noise and bias/drift effects analyzing the f easibility of the proposed system. A prototype device has been constructed and is currently being tested in a laboratory environment. Results of the simulation study indica te that accurate attitude estimates can be developed in the presence of large rate gyro drift and bias effects.