CN1670479A - Method for measuring aircraft flight elevation based on video images - Google Patents

Abstract

This invention discloses one aviation altitude measurement method based on images, which comprises the following steps: a, setting one shooting device on the aviator, distributed to shoot the vertical earth images parallel to the aviator, wherein the device comprises one image forming lens; b, shooting the first image at first time when in aviation and shooting the second image at second time later; c, setting one earth reference points, wherein the first and second images comprise reference points; d, separately measuring the said reference points the positions of first and second images to compute its displacement; e, finally computing the aviation altitude.

Description

Measure the method for aircraft altitude based on video image

Technical field

The present invention relates to the aircraft field, in particular, the present invention relates to the method that a kind of video image of taking with aircraft is measured aircraft altitude.

Background technology

The autonomous flight of minute vehicle (MAV) is to improve an important factors of minute vehicle performance and task scope.Therefore, the research to minute vehicle flight control method is the important step of minute vehicle research.When being carried out flight control, minute vehicle need obtain its flight parameter, for example the attitude angle of aircraft and height etc.

The flying height of aircraft is to determine an important parameter of aircraft flight state, provides an important indicator to flight control system, directly influences the flight condition of aircraft.Existing aircraft obtains flying height with altitude gauge usually, because minute vehicle all has certain restriction to weight, volume, the power consumption of load, being equipped with altitude gauge aboard certainly will will increase the load of aircraft, and it is not the best way that the method for therefore utilizing altitude gauge to obtain flying height is come institute to minute vehicle.Therefore needing to seek more simple and effective approach provides flight control needed flying height.

The vital task of MAV is scouted exactly, so camera system is its indispensable load.Video image information is abundant, and extracting useful flight information from video information is a very promising job.Therefore just need a kind of method and can utilize the flying height of the Image Acquisition aircraft that MAV takes photo by plane.

Summary of the invention

The object of the present invention is to provide a kind of measuring method of aircraft altitude, this method is applicable to minute vehicle; The present invention also aims to provide a kind of measuring method of aircraft altitude, this method utilizes the video image of taking photo by plane of aircraft to extract the flying height of aircraft.

To achieve these goals, the invention provides a kind of method, comprise step based on video image measurement aircraft altitude:

1) camera head is set on described aircraft, this camera head is arranged to when described aircraft horizontal flight described camera head can vertically take ground; This camera head comprises an imaging len, and its focal length is f;

When 2) aircraft was with speed v, roll angle θ and angle of pitch Φ flight, described camera head was at first first image of taking ground constantly, and described camera head is taken second image on ground in first second moment after constantly; The mistiming of described first moment with second moment is Δ t;

3) set a ground reference point; Described first image and second image comprise this reference point;

4) measure the position of described reference point respectively, calculate its displacement variable Δ s at described first image and second image;

5) according to the flying height H of described focal distance f, speed v, roll angle θ, angle of pitch Φ, mistiming Δ t and displacement variable Δ s calculating aircraft.

The flying height H=v Δ tfcos Φ cos θ/Δ s of described aircraft.When the aircraft horizontal flight, the flying height H=v Δ tf/ Δ s of described aircraft.

The method that the present invention utilizes video image to obtain flying height does not need extra sensor, can effectively reduce the weight and volume of load, and the flight parameter that passes through to be obtained helps aircraft and carries out Autonomous Control flight.

Description of drawings

Height measurement principle figure when Fig. 1 is the aircraft horizontal flight;

Fig. 2 is aircraft height correction schematic diagram when having the angle of pitch.

Embodiment

Below in conjunction with the drawings and specific embodiments the present invention is described in further detail.

The method of measurement aircraft altitude of the present invention is to obtain according to the ground image that aircraft is taken in flight course.When aircraft flight, different ground image of taking constantly can change, and that is to say, ground same reference point can change the position on image during the moment in difference.The present invention finds that the change in location of reference point in the ground image that difference is taken constantly directly reflected the flying height of aircraft.

For clearer explanation the present invention, at first extract the method for flying height with state description the present invention of aircraft horizontal flight.Carry-on camera head in other words camera be fixed on aircraft under, make camera when horizontal flight, can take ground image vertically downward.

High computational schematic diagram as shown in Figure 1 (is called first moment t hereinafter in a certain moment of aircraft flight ₁), the imaging len of camera is positioned at primary importance imaging len 5 places, since ground level 4 apart from the position of primary importance imaging len 5 can be approximated to be the infinite distance under, therefore ground level 4 is in the focussing plane place imaging of primary importance imaging len 5, the distance that this focussing plane is called first imaging plane, 1, the first imaging plane 1 and primary importance imaging len 5 is the focal distance f of lens.First imaging plane 1 is parallel to ground level 4.

Next moment in aircraft flight (is called second moment t hereinafter ₂), the imaging len of camera is positioned at second place imaging len 6 places, since ground level 4 apart from the position of second place imaging len 6 can be approximated to be the infinite distance under, therefore ground level 4 is in the focussing plane place imaging of second place imaging len 6, the distance that this focussing plane is called second imaging plane, 2, the second imaging planes 2 and second place imaging len 6 is the focal distance f of lens.Second imaging plane 2 is parallel to ground level 4.

Two single shaft coordinate systems of definition on Fig. 1.One is the aircraft coordinate system, the center of camera imaging plane is defined as the true origin of aircraft coordinate system; Another is an earth axes, with camera imaging plane center corresponding to the point on the ground level 4 as its true origin.For example, at first moment t ₁, the true origin of aircraft coordinate system is the center O of first imaging plane 1 _S1At second moment t ₂, the true origin of aircraft coordinate system moves to the center O of second imaging plane 2 _S2The place.For earth axes, at first moment t ₁, O _S1O on the corresponding ground _G1Point, O _G1Be exactly first moment t ₁The time earth axes initial point; At second moment t ₂, O _S2O on the corresponding ground _G2Point, O _G2Be exactly second moment t ₂The time earth axes initial point.The positive dirction of these two coordinate systems all is defined as the direction of aircraft flight speed as shown in arrow 3.

At first moment t ₁, ground reference point A _gA at first imaging plane 1 ₁Place's imaging, it is with respect to the center O of first imaging plane 1 _S1Displacement be S ₁At second moment t ₂, ground reference point A _gA at second imaging plane 2 ₂Place's imaging, it is with respect to the center O of second imaging plane 2 _S2Displacement be S ₂Be noted that owing to defined positive dirction as shown in arrow 3 at the aircraft coordinate system, so S ₁And S ₂Be vector with direction, S ₁Be from O _S1Be oriented to picture point A ₁, and S ₂Be from O _S2Be oriented to picture point A ₂

At first moment t ₁, ground reference point A _gWith respect to O _G1The displacement of point is x ₁At second moment t ₂, ground reference point A _gWith respect to O _G2The displacement of point is x ₂Owing to defined positive dirction as shown in arrow 3, so x at earth axes ₁And x ₂Be vector with direction, x ₁Be from O _G1Point to reference point A _g, and x ₂Be from O _G2Point to reference point A _g

Can draw from Fig. 1 according to geometric theory and optical theory:

$\frac{{-S}_1}{x_1}=\frac{f}{H_0},\frac{S_2}{{-x}_2}=\frac{f}{H_0}---\left(1\right)$

Height H when obtaining the aircraft horizontal flight according to formula (1) ₀=Δ xf/ Δ s, wherein Δ s=S ₂-S ₁, Δ x=x ₁-x ₂And Δ x=v Δ t, wherein v is the flying speed of aircraft; Δ t=t ₂-t ₁Obtain at last:

H ₀＝vΔt·f/Δs (2)

Like this, according to formula (2), the camera of aircraft is taken the ground image in two moment that obtain being spaced apart Δ t, measure the change in displacement Δ s of a reference point in two images then, last according to the speed v of aircraft and the focal distance f of camera, and obtain the height H of aircraft in conjunction with formula (2) ₀Wherein, the focal distance f of camera can be measured in advance, and the speed v of aircraft can by carry-on other sensor for example GPS obtain.

The above-mentioned method of utilizing the flying height of image calculation minute vehicle only is applicable to the situation of minute vehicle horizontal flight.Because camera is bonded on the fuselage, when minute vehicle is not horizontal flight, camera will be taken no longer vertically downward, and the height that calculate this moment is not the current true altitude of aircraft, but a pseudo-height.

In the minute vehicle system, these two degree of freedom of angle of pitch Φ and roll angle θ have caused utilizing the error of video image measuring height information.Be that example illustrates it is how to influence high computational, has provided the compensation method of high computational simultaneously now with the angle of pitch.

Fig. 2 is the schematic diagram of altitude correction method.Among Fig. 2, H _ΦBe the flying height of aircraft after utilizing angle of pitch Φ to revise, H ₀It is the height that utilizes formula (2) to calculate.

H _ΦCan obtain by following formula,

H _Φ＝H ₀cosΦ (3)

In like manner, when the aircraft roll angle is θ, utilize roll angle information to H _ΦDo further correction, can obtain the Live Flying height of aircraft when having angle of pitch Φ and roll angle θ, be shown below:

H＝H _Φ·cosθ＝H ₀·cosΦ·cosθ＝v(t ₂-t ₁)·f·cosΦ·cosθ/Δs (4)

When practical application, can obtain angle of pitch Φ and roll angle θ information with carry-on sensor, thereby the flying height of aircraft is made correction.

Claims (3)

1, a kind of method based on video image measurement aircraft altitude comprises step:

1) camera head is set on described aircraft, this camera head is arranged to when described aircraft horizontal flight described camera head can vertically take ground; This camera head comprises an imaging len, and its focal length is f;

When 2) aircraft was with speed v, roll angle θ and angle of pitch Φ flight, described camera head was at first first image of taking ground constantly, and described camera head is taken second image on ground in first second moment after constantly; The mistiming of described first moment with second moment is Δ t;

3) set a ground reference point; Described first image and second image comprise this reference point;

4) measure the position of described reference point respectively, calculate its displacement variable Δ s at described first image and second image;

5) according to the flying height H of described focal distance f, speed v, roll angle θ, angle of pitch Φ, mistiming Δ t and displacement variable Δ s calculating aircraft.

2, the method based on video image measurement aircraft altitude according to claim 1 is characterized in that the flying height H=v Δ tfcos Φ cos θ/Δ s of described aircraft.

3, the method based on video image measurement aircraft altitude according to claim 2 is characterized in that, when the aircraft horizontal flight, and the flying height H=v Δ tf/ Δ s of described aircraft.

Images