Today’s Heading Reference System: AHRS
Friday, May 16th, 2008Everyday, universal heading reference systems are continually developed to meet new and existing requirements, having an all weather capability. Attitude and heading reference systems are for military and commercial aircrafts. These systems provide an accurate determination of aircraft heading relative to true north. The goal is achieved by the use of a fluxgate magnetometers and/or a angular rate gyros. Depending on the region of operation, these devices as well as MEMS accelerometers are used by engineers and other personnel, engaged in testing and evaluating aircraft systems.
The system works simultaniously with other parts of the aircraft. When the aircraft is stationary, the light beams going in each direction a given ring gyroscope have exactly the same path length. Where they meet after a circuit of the instrument, they have a particular phase difference. I’m not certain that the instrument is tweaked to have it be zero, but without loss of generality, let’s say that it is zero. The beams are perfectly in phase.
Working from these principles, consider what happens to the gyro in the horizontal plane, when the aircraft turns to the left. The gyro has turned around so as to reduce the path for the light beam going clockwise. The light going counterclockwise has had its path increased and it doesn’t get a push from the turning motion. So the light beams will meet out of phase. Just as your VOR instrument works out what radial you are on by the phase difference between the two signals received, the computers associated with the ring laser gyro works out how much you turned, by the phase difference between the two beams.