WO1999005541A1 - Avionic system intended for use in aircrafts and involving use of an on-board radar equipment - Google Patents

Abstract

The invention pertains to an on-board radar equipment as part of the avionic system in an aircraft, said equipment providing a two-dimensional representation of the radar data from an area located upstream relative to the flight direction. The inventive radar equipment is an upstream sighting radar which gives of the radar data a high resolution and map-consistent representation from above in accordance with its basic operating mode resting upon the SAR(synthetic aperture radar)-based processing principle or an equivalent principle. A digital image processor enables a purely geometrical conversion of the map-consistent representation from above provided by said radar equipement into a corresponding image with a centered perspective projection and with a quasi-pilot vision. The invention is used when aircrafts and helicopters fly under bad visibility conditions or with no visibility at all.

Description

 description

Avionics system for aircraft using an on-board radar device

Technical field

The invention relates to an avionics system for aircraft using an entrained radar device with a two-dimensional perspective image of the radar data obtained from a sector area lying ahead in the direction of flight, including objects detectable there, on a viewing device.

State of the art

From US 3,988,731 a radar device with a two-dimensional perspective representation of a sector area lying ahead in the flight direction is known. Here, the respective sector is scanned by means of a fan beam that is very strongly bundled in the horizontal plane by swiveling. The reflected radar signal is displayed on the display device, for which purpose deflection voltages are generated in a horizontal and vertical direction, as in the case of television image generation.

In order that the terrain points and flying objects that are further away during a low flight are not too close to one another and therefore may no longer be resolved, the position of the aircraft carrying the radar is artificially moved to a higher position by changing the deflection voltages, so that the compressed distant terrain points and flying objects are further apart in elevation. The pilot is thus faked at a higher altitude. So there is an analog vertical and horizontal deflection on the screen, whereby a different point of view than the actual one is simulated by changing the deflection voltages. The image is generated based on the real antenna aperture of the mechanically swiveled antenna with strong fan beam bundling in the azimuth plane. The radar resolution in the distance is determined by the radar pulse length.

A forward view radar is known from DE 40 07 611 and DE 40 07 612, in which a flying carrier, for example an aircraft, images two-dimensionally from land or sea surfaces in a sector in front. For this purpose, in the known forward view radar, an antenna rigidly mounted on the carrier is provided, which either consists of a number of individual elements arranged in a straight line in a row (DE 40 07 611) or of a number of individual elements arranged in a straight line and in two rows one above the other ( DE 40 07 612), preferably in the form of horn antennas. With a given aperture length 1 of each individual element and with a given distance of n individual elements, the antenna has an antenna length L = n • 1 (DE 40 07 611) or an antenna length L = n • 1/2 (DE 40 07 612).

In this case, in the first-mentioned case (DE 40 07 611), an individual element transmits incoherently and then receives it simultaneously with the other individual elements. In the embodiment mentioned in the second place (DE 40 07 612), the individual elements are used to send and then receiving one after the other, from the first to the last of the number of individual elements.

To implement a digital coupling of the individual elements, each individual element is separately digitally evaluated, and digital correlation is carried out for each angular range in both cases by correlating a special, predetermined reference function.

With such a forward view radar with a rigidly mounted antenna, numerous advantages can be achieved with a downstream, specially designed processing method:

a) a high swiveling speed of the antenna lobe, since this is not realized mechanically, but electronically with the aid of special data processing;

b) a higher accuracy and therefore a better quality of the image than with all previously available

Devices;

c) independence from the speed of the wearer, and

d) significantly lower maintenance costs.

Such a forward view radar system can also be used in connection with helicopters, for example for search, rescue and environmental tasks, since no forward speed is required to use this forward view radar system and the self-movement of a helicopter, which is to a certain extent at a designated location, is immaterial. For completion, it is pointed out that US Pat. No. 5,053,778 discloses a method for forming a topographic terrain model represented in three-dimensional space, which is created by simultaneously combining an image generated on an airplane according to the SAR (synthetic aperture radar) principle with terrain height information , wherein this height information is obtained either from the aircraft, for example by means of a radar altimeter, or from ground measurements. However, a perspective view of a sector of the site lying in front of the aircraft is not provided in a pilot's view.

Presentation of the invention

The object of the present invention is to provide an avionics system which is suitable both for fixed-wing aircraft and for rotary-wing aircraft and which enables a pilot to precisely target a desired target area even under the most unfavorable visibility conditions or even without any visibility and with the highest accuracy requirements to be able to reliably detect even relatively small obstacles, land safely if necessary or take off without any view.

According to the invention, which relates to an avionics system of the type mentioned at the outset, this object is achieved in that the radar device is a forward view radar which, in accordance with its basic mode of operation, has a high-resolution map-top view image using the SAR (synthetic aperture radar ) Processing principle or a processing principle similar to this received radar data. Furthermore, according to the invention, a digital image processing device is provided, in which the top view image provided by the radar device is converted purely geometrically into a corresponding image with a central perspective projection in quasi-pilot view, which is displayed on the display device.

The radar is no longer resolved by the real aperture of an antenna, but by the correlation of the corresponding reference functions, as set out in the two previously mentioned patents DE 40 07 611 and DE 40 07 612. The top view image is created first.

The conversion to the perspective representation corresponding to a pilot's view relates to purely computational image processing and can only be carried out digitally. This changes the image accordingly so that the perspective is different. Suitable image processing algorithms can be easily created as software.

The image created on the display device by applying the invention is of high quality since the SAR method can provide an image with extremely high resolution. To achieve an accurate and therefore reliable flight orientation of the pilot in poor visibility, the replacement according to the invention of a conventional radar system working with a real antenna aperture by the SAR processing principle, which otherwise only applies to terrain observations from above, is therefore particularly advantageous. These properties of the avionics system according to the invention result in a wide range of applications for the use and use of the forward vision radar system, which ranges, for example, from military reconnaissance and combat helicopters to rescue and offshore helicopters to use in transport and civil aircraft . The image quality achieved with the system according to the invention cannot currently be achieved with any other system.

The avionics system according to the invention thus creates an all-weather sensor that can be used even in the worst visibility conditions or in conditions without any visibility and also during the night. Due to the central perspective projection in a quasi-pilot view according to the invention, a high image repetition rate creates a quasi-optical image with a continuous image display, for example on a high-resolution color monitor.

Advantageous further developments are the subject of subclaims.

Advantageously, height information of the scanned sector area terrain is introduced in a quasi-3D representation in the image shown. For this purpose, the height information can be generated directly according to a particularly advantageous embodiment based on the interferometric principle.

According to an advantageous development of the invention, height information relating to the height above ground of natural and / or artificial obstacles is introduced in quasi-3D representation in the image with a central perspective projection in a quasi-pilot view. Furthermore, in the two Display modes (top view and pilot view) can be color-coded.

An advantageous further development of the avionics system according to the invention consists in that a switchover between a first display mode, in which the sector image is shown in map-like top view on the display device, and a second display mode, in which the sector image in quasi-perspective projection Pilot view is shown on the display device is provided.

In an analogous manner, a radar device in the form of a forward view radar can also be used in shipping, in that the radar data obtained from a sector area lying ahead in the direction of travel of a ship, including objects detectable there, are displayed in a two-dimensional perspective view on a viewing device. Here, in a digital image processing device, a high-resolution top view image is converted purely geometrically into a corresponding image with a central perspective projection into a quasi-control man's view and displayed on the display device. Here, too, height information of the scanned preceding sector area in quasi-3D representation and height information regarding the height of natural and / or artificial obstacles in quasi-3D representation can be introduced into the image with a central perspective projection in the quasi-helmsman view become.

In addition, according to a further advantageous embodiment of the invention, any landing obstacles that protrude above a predetermined height above the ground can be found both in the top view illustration as well as colored in the quasi-pilot view. Furthermore, in the top view illustration as well as in the quasi-pilot view during reconnaissance flights, selected targets, in particular moving targets, can preferably be marked in color.

A particularly useful and advantageous development of the avionics system according to the invention consists in that an artificial horizon is faded into the image.

According to an advantageous embodiment of the invention, the central perspective representation in a quasi-pilot's view with the artificial horizon faded in is retained even when cornering. For example, according to a further development of the invention, it is possible on a highly sensitive color monitor to switch between a map-like top view image and a central perspective representation in a quasi-pilot view, in each case with a fake-in artificial horizon, even when cornering.

Likewise, you can switch between different distance areas in the map-like top view image as well as in the central perspective representation in a quasi-pilot's view with an inserted artificial horizon, so that a foresight mode is guaranteed.

In addition, according to yet another advantageous embodiment of the invention, the forward vision radar system can be switched between different frequency ranges, for example from the L band (1.3 GHz) to the X band (9.6 GHz), depending on the respective field of application ) up to the Ka band, which is around 35 GHz. When switching to the Ka band, the forward view radar system can for example, high-voltage lines or chain-link fences used to delimit areas can be recognized.

According to an advantageous embodiment of the invention, the central perspective representation can be automatically adapted to the flight altitude and the flight speed in a quasi-pilot's view with or without an artificial horizon shown.

Furthermore, as further advantageous developments of the invention, additional data or information can be faded into the central perspective representation in a quasi-pilot view, for example distances to marked targets, the height of marked obstacles or also a marking of moving targets, so that an MTI (moving Target Indication; mode is realized. Moving targets can also be marked.

In addition, it is possible within the scope of the invention to provide the central perspective representation from a quasi-pilot perspective with other operating modes, such as weather radar, surveillance radar and others. to combine.

Due to the high resolution that can be achieved when using the avionics system according to the invention, a device can be triggered or triggered, for example, with the aid of received and specifically selected data, which warns of obstacles. A so-called head-up display is also possible.

According to a further advantageous embodiment of the invention, in addition to the mapping of the earth's surface, information regarding the height above ground is also natural and / or artificial obstacles created in quasi-pilot view.

Due to the high-resolution, pictorial representation of the flight sector in the direction of flight, which can be achieved by using the forward view radar system, it can be used for civil and military flights, so that, for example, autonomous landing approaches, targeted, precise load shedding, etc. are reliably feasible.

Brief description of the drawings

The invention is explained in detail below using various examples with reference to the accompanying drawings. Show it:

Figure 1 is a schematic representation of an antenna made up of a number of individual radiators arranged side by side for use with forward vision radar.

FIG. 2 shows a schematic illustration of a lighting geometry as it results from an aircraft flying in a predetermined flight direction; FIG.

3 shows a plan view, true to the map, of a part of a runway and its immediate surroundings from an altitude of 1000 m;

FIG. 4 shows a central perspective representation corresponding to the representation in FIG. 3 in a quasi-pilot view of the same part of the runway and its immediate surroundings; 5 shows a plan view, true to the map, of a part of a runway from an altitude of 300 m;

6 shows a central perspective representation corresponding to the map of FIG. 3 in a quasi-pilot view, and

FIGS. 7 and 8 each show a top view of a group of trees from a flight height of 100 m, true to the map, areas in FIG. 8 with a certain height above the ground being marked separately.

Embodiments of the invention

In Fig. 1, n individual radiators in the form of horn antennas 10 of an antenna arrangement 1 are schematically arranged side by side in a straight line. As will not be shown in detail, the antenna arrangement 1 is rigidly attached to an aircraft - reproduced in a considerably reduced size - transversely to the direction of flight indicated by an arrow such that the main radiation direction of the horn antennas 10 points in the direction of flight.

According to DE 40 07 611, this is only transmitted by a single radiator, ie only by a horn antenna 10; subsequently, however, all other individual elements in the form of, for example, the horn antennas 10 are received. In contrast, in DE 40 07 612 the n individual radiators are used in succession from the first to the nth element for transmitting and then for receiving. Here, the processing of the raw data can be carried out in a manner similar to the known SAR principle, with a synthetic aperture in DE 40 07 611 by half the distance or in DE 40 07 612 by the distance between the first and the nth Single radiator of the horn antenna arrangement has to be replaced.

During processing, the respective signal is correlated in terms of amplitude and phase as a function of the distance with a complex conjugate reference function which is not specified here in detail. It is crucial, however, that the received signal at each individual element 10 has a different phase to the transmit pulse due to the different location between transmitter and receiver.

This means that in the case of incoherent operation, the phase relationship between the individual elements must be constant and known (DE 40 07 611). Since according to DE 40 07 612 one has to work coherently in the transmitting and receiving branch, the phase relationship of the signals received at different locations must be known to one another in this working method.

If the distance between the n individual radiators 10 is now Δx, this distance can be expressed by

Δx = 1 = λ / Θ in DE 40 07 611 or through

Δx = 1/2 = λ / 2Θ for DE 40 07 612,

where 1 is the aperture length of each individual radiator, λ is the wavelength and Θ is the illumination angle are drawn. The illumination angle Θ is entered in the illumination geometry shown schematically in FIG. 2.

If the distance between a target point T and a single radiator 10 of the respective antenna arrangement is denoted by r, the distance r can be expressed, as can be seen from the schematic illustration in FIG. 2, by:

where a is the distance between the antenna center axis 0 and a point target T, x is the distance between the antenna center axis 0 and a single radiator 10 and R is the distance gate distance, as is likewise the schematic illustration of FIG 2 can be seen.

In Fig. 3 from a flight altitude of 1000 m in the X-band a map-like representation in top view with a relatively short antenna is reproduced, with a part of an airstrip being visible in the middle of the image.

FIG. 4 shows the corresponding central perspective representation in a quasi-pilot view, which has been obtained by correspondingly implementing the map-like representation in a top view of FIG. 3. Part of the runway can be seen in the upper area of FIG. 4 and the area lying in front of the runway in the direction of flight can be seen in the lower area. 4 shows a faded-in artificial horizon along the upper longitudinal edge of the illustration, for example in the form of a black bar. Both in FIG. 3 and in FIG. 4, the illumination angle in the azimuth direction is 60 ° and the depression angle ranges from 14 ° to 60 °. The resolution in the azimuth direction is 10 m in the near range and 35 m in the far range, while the resolution in the elevation direction is 3 m.

5 shows part of the same runway of a map-like representation in plan view, this time from an altitude of 300 m.

6 shows the central perspective representation in a quasi pilot view. A faded-in artificial horizon, for example in the form of a black bar, is shown along the upper longitudinal edge.

FIG. 7 shows a top view of a group of trees and bushes at an X-band frequency of 9.6 GHz and from an altitude of 100 m in a map-true representation.

8 shows the same detail as in FIG. 7. In the practical embodiment, colored markings show areas which are at a height of, for example, more than 3 m above the surrounding area, i.e. 3 m above the floor, protrude upwards.

In FIGS. 7 and 8, as in the illustrations in FIGS. 3 and 4, the illumination angle in the azimuth direction is again 60 ° and the depression angle ranges from 14 ° to 60 °. 7 and 8, the resolution area in the near

2 2 range 0.6 m and in the long range 1.1 m.

Claims

Expectations 1. Avionics system for aircraft using an entrained radar device with a two-dimensional perspective image of the radar data obtained from a sector area lying ahead in the direction of flight, including objects detectable there, on a viewing device, characterized in that the radar device is a forward-looking radar that corresponds to it basic mode of operation provides a high-resolution map-true top view image using the SAR (synthetic aperture radar) processing principle or a processing principle similar to that received radar data, and that a digital image processing device is provided in which the map-true top view image provided by the radar device is purely geometrical a corresponding image with central perspective projection is converted into a quasi-pilot view, which is displayed on the display device. 2. Avionics system according to claim 1, characterized in that a switchover between a first display mode, in which the sector image is shown in map-like top view on the display device, and a second display mode is provided, in which the sector image in the central perspective projection is shown in a quasi-pilot view on the display device. 3. Avionics system according to claim 1 or 2, characterized in that height information of the scanned sector area terrain is introduced in a quasi-3D representation in the image shown. 4. Avionics system according to claim 3, characterized in that the height information is generated directly according to the interferometric principle. 5. Avionics system according to claim 3 or 4, characterized in that height information relating to the height above ground of natural and / or artificial obstacles in a quasi-3D representation is introduced into the image with a central perspective projection in a quasi-pilot view. 6. Avionics system according to claim 4 or 5, characterized in that during landing approaches any obstacles that exceed a predetermined height above the ground are marked in color in the image. 7. Avionics system according to claim 4 or 5, characterized in that selected targets, in particular moving targets, are marked in the image display during reconnaissance flights. 8. Avionics system according to one of claims 1 to 3, characterized in that a color coding is provided in the image display. 9. Avionics system according to claim 1 or 2, characterized in that an artificial horizon is faded into the image. 10. Avionics system according to claim 9, characterized by maintaining the central perspective representation in a quasi-pilot's view with a faded-in artificial horizon even when cornering. 11. Avionics system according to claims 2 and 9, characterized by maintaining the switchability between a map-like top view and a central perspective representation in a quasi-pilot's view, each with an inserted artificial horizon, even when cornering. 12. Avionics system according to one of the preceding claims, characterized in that the central perspective projection in a quasi-pilot's view with a faded-in artificial horizon can be switched between different distance ranges. 13. Avionics system according to one of the preceding claims, characterized in that depending on the respective The frequency range (L-band to Ka-band) of the forward view radar can be switched. 14. Avionics system according to one of the preceding claims, characterized in that the central perspective representation in quasi-pilot's view with the artificial horizon inserted is automatically adapted to the flight altitude and the flight speed. 15. Avionics system according to one of the preceding claims, characterized in that additional data / information are mapped to the central perspective representation in a quasi-pilot view. 16. Avionics system according to one of the preceding claims, characterized in that the central perspective representation in quasi-pilot view with one or more loading operating modes, such as weather radar, surveillance radar and the like. is combined.