DE102009060901A1 - Landing aid device for vertical landing aircrafts, particularly helicopter, has image capturing unit for optical acquisition of spaces directly below a vertical landing aircraft, and evaluation unit - Google Patents

Abstract

The landing aid device has an image capturing unit (1-a,1-b) for optical acquisition of spaces directly below a vertical landing aircraft (L), and an evaluation unit (2). The evaluation unit is equipped for determining the drift rate of the aircraft from a consequence of images of the spaces by feature comparison of image contents under consideration of actual rotary rate of the aircraft.

Description

The invention relates to a landing aid for vertically landing aircraft, in particular helicopters, with at least one image recording unit for optical detection of the space directly below an aircraft designed for vertical landing and with an evaluation unit.

At each landing of a vertically landing aircraft, in particular helicopters, the pilot must ensure by appropriate control inputs that in particular the lateral drift of the helicopter does not exceed a certain size immediately before touchdown. Failure to observe this maximum allowable lateral drift may result in a dangerous rolling moment after first touching the Landing Gear or Landing Gear with the ground, which can eventually lead to a lateral rollover of the helicopter. In order for the pilot to assess the lateral drift at the moment of touchdown and to compensate for the control inputs, it is necessary to have as complete an unobstructed visual survey of the immediate surroundings of the helicopter as possible. In landings where the detection of the surroundings is restricted by the movement of sand, dust or snow, dangerous situations and even accidents occur again and again. These situations are also referred to as "brown-out" for sand and dust hard landings or "white-out" for snow-threatened landings. The swirling up of dust, sand or snow particles on the ground is caused by the own rotor downwind. The strength of this effect increases with decreasing altitude. As long as the trajectory of the helicopter has a forward movement develops first a so-called dust roller behind the helicopter, which finally assumes a toroidal shape with decreasing altitude and speed. Shortly after the horizontal movement of the helicopter comes to a standstill, this "dust torus" finally encloses the entire external field of vision and the visual position detection and assessment of the lateral drift is no longer possible for the pilot.

In assisting the guidance of aircraft, the use of image sensors is known. So describes z. B. DE 694 26 738 T2 a navigation system with a passive image sensor, in which the images of a camera available onboard are used to calculate navigation data. The data from the image sensors may be combined with data from a secondary sensor aboard the aircraft to provide e.g. B. to determine a velocity vector of the aircraft.

DE 10 2007 019 808 A1 discloses a landing aid system for vertically-launching and vertically-landing aircraft with downward-facing cameras. these are, in particular, distance-imaging cameras, so-called PMD cameras (photon mixing detector), with which information about the height of the aircraft over ground is determined.

In DE 10 2007 019 806 A1 a device and a method for the precise determination of the horizontal movement state of a helicopter in restricted visibility conditions is described. A ground marking device is provided in order to provide a predetermined floor area with a mark which can be distinguished from its surroundings and is immovable relative to the predetermined floor area. With a ground detection device, the predetermined ground area is detected. This is also possible in brown-out and white-out situations, as the area just below the helicopter is essentially particle-free and can be detected by image sensors.

DE 103 06 417 A1 discloses a method and an apparatus for optical scanning in a relative movement between a sensor and an object located in the measuring space of the sensor. The functional principle of the motion sensor corresponds to an optical mouse. The method is used to detect the presence of objects or to measure the movement or the lateral distance.

DE 102 54 545 A1 discloses a stabilization system for missiles with an imaging optics attached to the missile for detecting the ground image. The movement and / or position of the missile is determined by detecting structures of the ground images and determining shifts of a sequence of ground images based on the detected structures. The optically obtained measured value can be corrected for the influences resulting from rotational movements (rolling, pitching, yawing) of the missile by calculating or mixing an independent rotational signal with the optical measured value. In particular, unmanned small helicopters can be stabilized and automated with the help of the system.

In US Pat. No. 7,106,217 B2 A method is described for assisting the flight under restricted vision. The pilot is assisted by a display attached to the pilot's head to display an external view. The external view shown is generated from a data fusion of a plurality of sensor data. The external situation is detected via digital map data, satellite-based position information, air data and image data, preferably in the infrared range.

US 2006/0087452 A1 describes a method of assisting the pilot in landing a helicopter in brown-out or white-out conditions in visual flight. Before the visibility restriction occurs, a three-dimensional model of the landing site is generated from sensor data. After the visibility restriction occurs, the pilot is presented with a synthetic view of the previously generated three-dimensional model.

The landing of helicopters under reduced visibility, especially with dust, sand or snow whirled up, is still a problem despite these aids.

The known auxiliary equipment for dust landings require complex additional installations with a complex integration into the existing helicopter avionics. These concepts are usually based on the use of expensive sensors that are not easy to attach to the helicopter. In addition, there are a large number of helicopters worldwide which offer no avionics interface for data and displays at all.

The object of the present invention is therefore to provide an improved landing aid for vertically landing aircraft.

The object is achieved with the landing aid of the type mentioned above in that the evaluation unit for determining the drift rate of the aircraft from a sequence of images of the space is set directly below the aircraft by means of feature comparison of image content, taking into account the current rate of rotation of the aircraft.

The landing aid makes use of the fact that the space directly underneath the aircraft, in particular a helicopter, which is designed for vertical landing, is largely particle-free, even when particles are fluidized, and can be observed with the aid of optical image recording units. During the hovering flight, a dust-free region remains behind the helicopter, at least for a certain time after standstill, through which the ground remains visible.

However, it is not enough, the pilot the picture of the landing field under his helicopter directly z. B. display via a display, since only with reference to this image information, the longitudinal or lateral drift of the helicopter can not be detected. The lateral displacement of the entire image is caused not only by the transverse and longitudinal drift, but also by rotations about the transverse and longitudinal axis substantially.

According to the teachings of the present invention, therefore, the drift rate is determined not only from a sequence of images of the space directly below the aircraft by feature comparison of image contents, but also taking into account the current rate of rotation of the aircraft.

The drift rate thus refers to the lateral and / or longitudinal drift, while the rate of rotation describes the rotation of the helicopter and thus of the camera about its longitudinal and transverse axis. With the aid of the automatically operating evaluation unit, it is thus possible to determine the transverse and / or longitudinal drift of the helicopter from the image data taking into account the rotation rates and finally display these on a suitable display or in an (automatic) control / regulation system for attributed to the helicopter.

The at least one image recording unit is z. B. in the form of a camera easily and inexpensively. For this purpose, the at least one image recording unit must be arranged only below the helicopter so that it looks directly downwards.

Preferably, with at least one yaw rate sensor which can be connected to the evaluation unit, relative drift rates can then be calculated from the space directly below the aircraft by means of a fully automatic, automatic, step-by-step evaluation of the recorded images. The calculation then takes place in the evaluation unit, which can be a suitably programmed evaluation computer.

It is advantageous if absolute drift rates from the relative drift rates are determined as a function of a current altitude of the aircraft over ground. This can be achieved, for example, by arranging the evaluation unit for determining the current height of the aircraft over ground by image evaluation of at least two images recorded simultaneously with at least two image recording units. By such a multi-image analysis, in particular a stereo image analysis, can in a conventional manner from the known mounting positions of the image recording unit z. B. be determined by triangulation from features of the simultaneously recorded images, the current altitude of the aircraft over ground.

By referencing the relative drift rate to the current altitude, the absolute drift rate results.

However, the evaluation unit can also have an input for a height signal, which represents the current height of the aircraft over ground. This altitude signal may consist of an already integrated in the aircraft altitude sensor, such. B. one Radar altimeter, come, so that can be dispensed with another image acquisition unit for height determination over the landing field.

It is also conceivable that the evaluation unit has an input for yaw rate signals of yaw rate sensors of the aircraft already installed in the aircraft. Then the yaw rates of the existing reference and position measuring devices of the helicopter z. B. using a digital avionics interface can be used.

Regardless of the availability of an avionics interface, the landing aid can be easily integrated into the helicopter with little effort.

As yaw rate sensors yaw rate sensors are preferably utilized for detecting the current pitching motion of the aircraft about a pitch axis and the current rolling motion of the aircraft about a roll axis.

It is particularly advantageous if the evaluation unit is also set up to determine an inclination angle of the landing area by comparing features from two or more images recorded simultaneously with several image recording elements.

The invention will now be described by way of example with reference to the accompanying drawings.

Show it:

1 - Sketch of a helicopter landing in a swirling dust cloud;

2 Block diagram of an embodiment of a landing aid with two imaging units and a rotation rate sensor;

3 Block diagram of another embodiment of the landing aid with an image pickup unit and interface for an external rotation rate sensor signal;

4 - Another embodiment of a landing aid with an image pickup unit and external display unit;

5 Block diagram of an embodiment of a landing aid with processing stages in the evaluation unit.

1 shows a sketch of a vertical landing trained aircraft L in the form of a helicopter, on the underside of two image recording units 1-a and 1-b are arranged. The image acquisition units 1-a and 1-b are aligned with their optics for detecting the space directly below the helicopter L and with an evaluation unit 2 connected.

When landing the helicopter L, the problem of whirling up of dust, sand or snow S. arises While the dust cloud S develops approximately in the form of a torus, remains directly below the helicopter L a certain area low dust, through which the camera system with the image recording units 1-a and 1-b can watch the ground. The automatic evaluation of the image acquisition units 1-a and 1-b captured images on board the aircraft L through the evaluation unit 2 performed. Here, a drift rate is determined as described below, which can be displayed with a display unit to the pilot.

With the aid of at least one image acquisition unit rigidly connected to the helicopter cell 1-a and or 1-b (Camera), whose optical axis is oriented approximately parallel to the Z-axis of the aircraft L, the area lying under the aircraft L is detected. The images taken from the space below the aircraft L are fed with a time stamp for the recording time t in the form of a two-dimensional digital color and / or black and white image in the further processing chain.

Furthermore, with the help of at least one in the 2 sketched rotation rate sensor 3 the actual rate of rotation about the pitch and roll axis recorded at the recording times t and together with the recorded images in the evaluation 2 transferred.

The evaluation unit 2 has a drift rate determination unit 4 that z. B. can be designed as a suitable programmable computer.

The evaluation unit 2 is z. B. by programming the Driftratenermittlungseinheit 4 for the evaluation of the images so arranged that with a feature extraction unit from each of the acquired digital images a feature list is generated which describes the image content at the recording time t in a symbolic way. With the help of a feature list comparison unit is then z. B. determined by statistical analysis of the feature lists a mean shift Δ (separated in x and y direction) of all features in the entire image field. By reference to the recording times t or the preceding exception times t-1 of the current or previously recorded image, the speed of displacement of all features in the image coordination system is calculated. The Shifting speed is z. B. captured in image pixels per second.

By referring to the measured rotation rates about the pitch and roll axis of the aircraft L, the drift rate of the aircraft L in the transverse and longitudinal directions can then be calculated with knowledge of the optical coverage angle of the camera used. The drift rate is preferably given in% per second.

The drift rates in the longitudinal and transverse directions can then be displayed on a suitable display unit 5 being represented. This display unit 5 can be an integral part of the evaluation unit 2 be. It is also conceivable, however, that the evaluation unit 2 has an interface for an external display unit.

Since the values for the drift rates in the transverse and longitudinal directions of the aircraft L calculated automatically as described above are relative quantities which relate to the width or height of the image field and z. B. measured in% per second, may require a conversion of the relative drift rate in an absolute drift rate. To calculate such an absolute drift rate, measured in meters per second, the height of the aircraft L above the landing field must be known.

3 shows an embodiment of a landing aid as a block diagram with only one image pickup unit and without integrated rate of rotation sensor. The rotation rate is via a preferably digital interface 6 read out from an already existing in the aircraft L digital position reference system. The height of the aircraft L over ground is via a preferably digital interface 7 z. B. read from a radar altimeter of the aircraft L.

4 shows another embodiment of the landing aid without its own display unit. The in the drift rate determination unit 4 the evaluation unit 2 calculated drift data are transmitted via a preferably digital interface 8th to a z. B. in the aircraft L already available data acquisition and display unit and transmitted to an existing display unit 9 shown.

5 shows a block diagram of a landing aid, wherein the individual processing stages within the evaluation unit 2 are recognizable.

It is clear that the at the time of recording t of the image recording units 1-a and 1-b taken pictures of an image capture 10 be supplied. The through the image capture 10 captured image data are by a feature extraction 11 evaluated so that feature lists are calculated. In this case, a feature list is generated from each of the acquired digital images, which describes the image content at the respective recording time in a symbolic manner.

The feature lists correspond to a compact, symbolic description of recorded image contents and form the starting point for further processing. In the subsequent displacement calculation 12 First, the shifts are determined by the image characteristics of the two images recorded simultaneously in the feature lists in order to calculate the height of the aircraft L above ground. This is done with the help of well-known image evaluation.

In addition, in the shift calculation 12 From the displacements of the features at successive times t and t-1, the speed of movement of features in image coordinate systems is calculated. It is thus checked to what extent an image feature of a picked-up image at the time t-1 in the later image at the time of acquisition t, that of the same image acquisition unit 1 . 1-a or 1-b was recorded, has moved in the two-dimensional image plane.

In conjunction with that of a rotation rate sensor 3 Detected rotation rate about the pitch and roll axis and the already determined height above ground then from this the longitudinal and lateral drift of the aircraft L is determined. This is quite easily possible taking into account the geometric wheel conditions and the rotation rate-influenced tilting of the image acquisition unit with respect to a landing plane.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 69426738 T2 [0003]
• DE 102007019808 A1 [0004]
• DE 102007019806 A1 [0005]
• DE 10306417 A1 [0006]
• DE 10254545 A1 [0007]
• US 7106217 B2 [0008]
• US 2006/0087452 Al [0009]

Claims (9)

Landing aid for vertically landing aircraft (L) with at least one image acquisition unit ( 1 . 1-a . 1-b ) for the optical detection of the space directly below an aircraft designed for vertical landing (L) and with an evaluation unit ( 2 ), characterized in that the evaluation unit ( 2 ) for determining the drift rate of the aircraft (L) from a sequence of images of the space directly below the aircraft (L) by means of feature comparison of image contents, taking into account the current rate of rotation of the aircraft (L) is established. Landing aid according to claim 1, characterized in that the evaluation unit has an input for rotation rate signals of rotation rate sensors of the aircraft (L). Landing aid according to one of the preceding claims, characterized in that the landing aid gyroscope sensors for detecting the current pitching motion of the aircraft (L) about a pitch axis and the current rolling motion of the aircraft (L) has a roll axis. Landing aid according to claim 3, characterized in that the rotation rate sensors with the at least one image recording unit ( 1 . 1-a . 1-b ) are connected. Landing aid according to one of the preceding claims, characterized in that the evaluation unit ( 2 ) for determining the current height of the aircraft (L) over ground by image evaluation of at least two simultaneously with at least two image recording units ( 1 . 1-a . 1-b ) and to determine the absolute drift rate as a function of the determined current altitude. Landing aid according to one of the preceding claims, characterized in that the evaluation unit ( 2 ) has an input for a height signal representative of the current altitude of the aircraft (L) above ground and arranged to determine the absolute drift rate in response to the current altitude represented by the altitude signal. Landing aid according to one of the preceding claims, characterized in that the evaluation unit ( 2 ) with a display unit ( 5 . 9 ) is connectable to the display of the current drift rate. Landing aid according to one of the preceding claims, characterized in that the evaluation unit ( 2 ) is connectable to a control unit of the aircraft (L) for controlling the landing process as a function of the determined drift rate. Landing aid according to one of the preceding claims, characterized in that the evaluation unit ( 2 ) for determining an inclination angle of the landing surface by comparing features of two or more simultaneously with at least two image recording units ( 1 . 1-a . 1-b ) is set up.

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