Dynamic attitude measurement method and apparatus
A method and system senses the attitude of an accelerating object by measuring acceleration with accelerometers in three orthogonal axes and measuring angular rate with angular rate sensors disposed about each such axis to compute attitude of the object accurately relative to a vertical axis. A processor updates a quaternion representation of attitude based upon the angular rate of the object, and a corrective rate signal is determined from level frame acceleration as a reference for a Kalman filter in calculating the attitude of the object. When velocity or airspeed is available from an external source, an aiding algorithm is employed to provide accurate attitude representations throughout all flight regimes.
1. A method for correcting a predicted attitude of an accelerating object, the method comprising:
receiving external aiding data;
calculating an inertial speed from the external aiding data;
adjusting a sensor correction factor in response to the inertial speed; and,
correcting the predicted attitude of the accelerating object in response to the adjusted sensor correction factor.
2. The method of correcting the predicted attitude of claim 1 , wherein receiving external aiding data comprises:
receiving a calculated velocity measurement.
3. The method of correcting the predicted attitude of claim 1 , wherein receiving external aiding data comprises:
receiving an airspeed measurement.
4. The method of correcting the predicted attitude of claim 1 , wherein adjusting the sensor correction factor in response to the inertial speed comprises scaling a pitch measurement residual gain in response to the inertial speed.
5. The method of correcting the predicted attitude of claim 1 , wherein adjusting the sensor correction factor in response to the inertial speed comprises scaling a roll bias in response to the inertial speed.
6. The method of correcting the predicted attitude of claim 1 , wherein adjusting the sensor correction factor in response to the inertial speed comprises scaling a pitch bias in response to the inertial speed.
7. A system for correcting a predicted attitude of an accelerating object, comprising:
a processor for receiving external aiding data and computing an inertial velocity; and,
an adaptive filter, coupled to the processor, comprising a sensor correction factor adjusted in response to the inertial velocity, for predicting the attitude of the accelerating object.
8. A system for correcting the predicted attitude of claim 7 , wherein the external aiding data is a velocity measurement.
9. A system for correcting the predicted attitude of claim 7 , wherein the external aiding data is an airspeed measurement.
10. A system for correcting the predicted attitude of claim 7 , wherein the adaptive filter is a Kalman filter.
11. A system for correcting the predicted attitude of claim 7 , wherein the sensor correction factor is a pitch measurement residual gain.
12. A system for correcting the predicted attitude of claim 7 , wherein the sensor correction factor is a roll bias.
13. A system for correcting the predicted attitude of claim 7 , wherein the sensor correction factor is a pitch bias.