Passive local wind estimator
First Claim
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; and
calculating 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.
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Accused Products
Abstract
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.
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Citations
22 Claims
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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:
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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; and calculating 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A device adjusted to navigate an aircraft having a mass m, the device comprising:
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at least one of an inertial navigation unit, a Global Positioning System (GPS) unit, and an autopilot programmed to measure a ground speed associated with the aircraft; an accelerator configured to measure an acceleration aB of the aircraft; a multiplier adjusted to multiply the acceleration aB with the mass m resulting in a required aircraft force for experienced motion ; at least one processor for 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; a subtractor adjusted to subtract the controlled aerodynamics A from the required aircraft force for experienced motion resulting in a calculated drag force D; at least one processor for calculating an unfiltered airspeed A from the calculated drag force D by reverse calculation of a model of the drag force D being dependent on the unfiltered airspeed A; at least one processor programmed to estimate an airspeed of the aircraft based on the acceleration aB of the aircraft and controlled aerodynamic forces applied to the aircraft; at least one processor programmed to estimate a wind field experienced by the aircraft based on the ground speed and the airspeed; and at least one processor being programmed to navigate the aircraft based on the estimated wind field. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification