Passive local wind estimator

摘要

Local wind fields can be predicted if both the airspeed and the ground speed of the helicopter are known. An aircraft that uses an inertial navigation unit, autopilot and estimator allows a measure of ground speed to be known with good certainty. The embodiments herein extends this system to allow an estimate of the local wind field to be found without actively using an airspeed sensor, but instead combining the measurements of an accelerometer and a drag force model and a model of controlled aerodynamics of the aircraft to estimate the airspeed, which again can be used to estimate the local wind speed.

主权项

1. A method in a device for navigating an aircraft, the device including an accelerometer configured to measure an acceleration aB of the aircraft, the aircraft comprising a mass m, the method comprising:
measuring a ground speed associated with the aircraft; estimating an airspeed of the aircraft based on the acceleration aB of the aircraft and controlled aerodynamic forces applied to the aircraft, estimating the airspeed of the aircraft including:
multiplying the acceleration aB, with a mass m resulting in a required aircraft force for experienced motion ;calculating a controlled aerodynamics A by a model of the controlled aerodynamics A having at least a rotation rate and a control state of the aircraft as input in addition to a current estimate for the airspeed A;subtracting the controlled aerodynamics A from the required aircraft force for experienced motion resulting in a calculated drag force D; andcalculating an unfiltered air speed A from the calculated drag force D by reverse calculation of a model of the drag force D being dependent on the unfiltered air speed A; estimating a wind field experienced by the aircraft based on the ground speed and the airspeed; and navigating the aircraft based on the estimated wind field.