DE3000654A1 - SYSTEM FOR REPRESENTING THE MOVEMENT OF A VEHICLE RELATIVE TO A SURFACE - Google Patents

Description

30ÜUb5A

Dipl.-Ing.

Rolf Charter " ³ "

Patent attorney

Rehlingenstrasse 8 ■ P.O. Box 260

D-8900 Augsburg 31

Telephone 08 21/3 6015 +3 6016

Telex 53 3 275

Post check account: Munich No. 1547 89-801

8066/103 / Ch / Gr Augsburg, January 8, 1980

Smiths Industries Limited Cricklewood Works
GB-London NW2 6JN

System for displaying the movement of a vehicle relative to a surface

The invention relates to a system for displaying the movement of a vehicle relative to a surface.

Such a system is particularly suitable for measuring the speed or distance of a moving missile relative to the ground, for example a heliocopter or an airplane.

While the speed of a missile relative to the air in which it is moving can be measured relatively easily, for example Using a dynamic pressure gauge, it is difficult to make such airspeed measurements accurately in the aircraft itself relative to the reason.

Some planes today are equipped with television cameras or other electro-optical Equipped sensors, which are directed to the ground below the aircraft and which for monitoring and observation serve the reason. The output signals of these cameras are fed to a television screen or a recording device,

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which is located inside the aircraft or at a ground station is.

The task is the movement of a vehicle relative to a surface with the help of such electro-optical Measure sensors accurately.

This object is achieved with the features of claim 1. Advantageous Refinements can be found in the subclaims.

One embodiment of a system for measuring speed and the direction of an aircraft relative to the ground is explained in more detail below with reference to the drawings. Show it:

1 shows a schematic representation of an aircraft which is flying over the ground;

2, 3 and 5 fields of view of a television camera arranged in the aircraft at different times and

Figure 4 is a schematic diagram of the system.

FIG. 1 shows an unmanned missile 1 which flies over ground 3 in the direction of arrow 2. There's one on the plane Platform 5, a television camera 4 mounted, which is stabilized in terms of azimuth and attitude, so that the camera always is directed vertically downwards onto the floor 3. This means that the edges of the field of view of the camera are always in the in the same direction, regardless of the movements of the aircraft. The camera 4 supplies signals via a radio data link unit 6 (Fig.4) to a television screen 7 of a ground station. The field of view during a raster scan of the Camera 4 is shown in FIG. The field of view of the camera during the subsequent raster scan at time t later, after the aircraft 1 has traveled a distance d relative to the ground 3

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is shown in Figure 3. The system identifies an area Aq on the ground within the field of view during one raster scan and then locates the same area A _Q during the subsequent raster scan. The system now measures how far the area Aq has shifted within the field of view, the system knowing the altitude h at which the aircraft 1 is flying above ground 3. A display of the distance covered is derived from this. The speed of the aircraft relative to the ground 3 can then be derived on the basis of the time interval st between successive raster scans.

The system will now be described in detail with reference to FIG. The television camera 4 sees the ground 3 below the aircraft 1 and supplies video signals along the line 8 to a data connection unit 6 and a computing unit 10 in the form of a microprocessor. The video signals are in analog form and provide information about the brightness level, including the usual line and frame synchronization pulses. The computing unit 10 comprises a video processor unit 11 which converts those video signals within a small area B into digital form. This area B lies in the field of view of the camera 4, as shown in FIGS. 2, 3 and 5. The computer unit 10 transmits these digital signals to first storage locations 12. The area B is fixed within the field of view of the television camera 4 and corresponds to the area A _{0 of} the floor 3 during the first raster scan, as FIG. 2 shows, where the areas B and Aq overlap each other.

Every horizontal line of the television camera grid can be viewed are divided into a number of small elements, the brightness of which can be defined by a digital number, which is derived from the video processor 11 in accordance with the video signals. The area B in this example has the Shape of a narrow vertical stripe, the width of which corresponds to a few picture elements along a raster line. Üie

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The length of the area B is less than the field of view. However, the surface B can and can have various shapes and sizes oriented at any angle to the direction of flight of the aircraft be. The area B can, for example, have the shape of a vertical line which contains a picture element or raster point is thick or can also have the shape of a cross. Alternatively, it is possible that different discrete areas distributed across the field of view.

After the subsequent image scanning after time t, the video signals, which are representative of the same area B within the field of view, are fed to a second set of storage locations 13 within the computer unit 10. Since the aircraft 1 has moved between these successive image scans by the distance d, the area B within the field of view of the camera 4 now corresponds to another area A, the ground, while the original area A _Q has now shifted within the field of view, such as this is shown in FIG. The area Aq of the ground now corresponds to the area C in the field of view of the camera 4. To identify the position of this area C, the video signals of this second image scan are compared with the stored signals which are representative of the area B of the first image scan. This comparison is carried out according to FIG. 4 in a comparison unit within the computer unit 10. In practice, this comparison is not carried out by a discrete unit, but rather is achieved by suitable programming of the computer unit 10. The comparison is described in detail later.

If a match or largely the best match has been determined, then the coordinates of area C used in a computing process to guide the distance S between the two areas B and C within the field of view. the Coordinates are derived from the line and image synchronization pulses. Together with the distance S is derived

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the direction in which face C is displaced relative to face B. According to FIG. 4, this calculation is carried out by a separate arithmetic unit 15. In practice, this calculation is of course carried out by a programmed operation of the arithmetic unit 10. The arithmetic unit 10 also receives signals via the line 20 from a radar altimeter 21 of the aircraft, these signals being representative of the flight altitude h of the aircraft over the ground. Since both the distance S and the height h are now known, it is possible to calculate the distance d that the aircraft 1 has covered between successive image scans. Since the time interval t between successive image scans is known, it is now possible _{to calculate the longitudinal and lateral components Vq and V a of} the speed of the aircraft relative to ground 3. Signals which are representative of the speed components V _n and V are now transmitted via a line 30 υ a

an on-board device 31 supplied, this being a

Navigation or flight control system. These signals can

can also be fed to a ground station via a radio data line.

After the comparison of the signals from the television camera with those stored in the first memory locations 12 has ended a further comparison can be made. The subsequent comparison is made between the signals from the television camera 4 after a period of time 2 after the first image scan with the signals which are stored in the second memory sections 13 after the point in time t. So this means that signals from Video processor 11 during successive scans after time intervals of t seconds alternately the first and the second storage locations 12 and 13 are supplied, each the previous content of the memory locations is deleted.

In order to reduce the period of time which is required for the comparison to identify the area C, the search can only be limited to the area H in which the area L.

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likely to occur. The area H is larger than the areas B and C and the position of the area H within the field of view is determined in accordance with a rough measurement of the speed of the aircraft and the direction of flight, which can be derived from previous image scans or by other methods. In addition, signals V can be fed via a line 40 from an accelerometer 41 to the computing unit 10 in order to improve the position of the area H by compensating for changes in the speed of the aircraft between successive image scans. Signals 0 can also be fed to the arithmetic unit, which are representative of the heading of the aircraft and which are derived from an aircraft compass 51 via line 50.

The comparison with which the area c within the area H is identified can be carried out in various ways. In one embodiment, a number of areas B ¹ within area H of the same size and shape as area B can be compared with the signals from storage locations 12. Here, the brightness of each pixel along each raster line is compared with the stored brightness values of corresponding pixels of the area B. A number which is representative of the degree of correspondence between the brightness of each of the corresponding pixels is fed to an accumulator. The accumulator adds these numbers and gives an overall representation of the degree of correspondence between the area B ¹ and the area B. Corresponding total values are calculated for each of the areas B ¹ . The face with the highest degree of correspondence is considered face C.

There are several ways to do this correlation. For example, it is also possible to group individual pixels of area B in order to form a number of groups, each of which has different pixels, each pixel being assigned a brightness value. The values of this

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The values of these groups can then be compared with the values of corresponding groups within the area B ^{1 of} the area H. The degree of correlation for each area B ¹ is then derived accordingly. The degree of brightness on which the correlation is based can be simplified by using only two degrees of brightness, ie in light and dark, on the basis of a multi-level gray scale.

In an alternative correlation method, the system for identifying the area C corresponding to the original area B initially operates as described above. In a subsequent image scanning according to FIG. 5 after the period of time 2 t after the original image scanning, the correlation is expanded by also identifying the area D in the field of view corresponding to the original area A _{Q of} the ground. This identification takes place in addition to the identification of the area in the field of view corresponding to the area A _t . This comparison can be repeated for any number of time intervals t during which the area Aq remains within the field of view.

Television cameras for distant viewing are usually used sampled several times per second. In the present case, however, it is not necessary to read the information every time the image is scanned to use unless exceptional circumstances exist. It can happen that the aircraft 1 in less Height above ground 3 flies at high speed, and the field of view and the scanning speed of the camera 4 is such that the area Aq is only in the field of view during an image scan is located. In this case, the previously described measuring method is no longer possible. In such a case it is therefore advantageous to to align the camera 4 forwards, backwards or sideways, with suitable corrections when calculating the speed of the aircraft are required. The camera 4 does not necessarily need to be attached to a stabilized platform. It is also possible to supply the computing unit 10 with information relating to the pitch, roll and walker axes in order to compensate

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of attitude changes.

In the application described above, the unmanned aircraft controlled by radio control at a remote ground station, for example. The system according to the present invention can also be used to automatically control the navigation if the radio connection with the ground station fails.

Problems can arise if the system starts working when the aircraft is already in flight, as then the system is normally has no information on airspeed and direction of flight that would enable area H to be entered locate. In such a case, the system can be ordered to initially the correlation is carried out over the entire field of view, or it is also possible to use speed information from other sensors, such as an integrated accelerometer or a dynamic pressure gauge.

In the previous embodiment, a television camera 4 was used, which responds to visible wavelengths. However, it is also possible to use an infrared camera or an image intensifier use. It is also possible to use an alternative imaging system using a scanned beam, for example an optical laser beam or an X-ray beam or an acoustic sonar beam, in which case a sensor is then provided that receives the radiation reflected from the ground.

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Claims (9)

Dipl.-ing. RolfCharrier patent attorney Rehlingenstrasse 8 · P.O. Box 260 D-8900 Augsburg 31 Telephone 08 21/3 6015 +3 6016 Telex 53 3 275 postal check account; Munich No. 1547 89-801 8066/103 / Ch / Gr Augsburg, January 8, 1980 Note: Smiths Industries Limited patent claims 1. ιSystem illustrating the movement of a vehicle relative s \ to a surface, characterized in that an image pickup means (4) generates signals which are representative of an image of a part (A _Q) of the surface (3), a computer (10 ) is provided, which calculates a measure for the displacement relative to the field of view of at least part of the image as a result of the movement of the vehicle (1) relative to the surface (3) and which provides a representation of the movement of the vehicle (1) relative to the surface (3 ) in accordance with the displacement of the image and the distance of the vehicle (1) from the surface. 2. System according to claim 1, characterized in that the image recording means (4) are arranged on a platform (5) which is stabilized in azimuth. 3. System according to claim 1 or 2, characterized in that that the image recording means (4) on a platform (5) is arranged, which is stabilized in the flight position. 4. System according to one of claims 1 to 3, characterized in that the image recording means (4) is a television camera is. 030030/0713
BATH ORIGINAL 30Q065A 8066/103 / Ch / Gr - 2 - January 8, 1980 5. System according to claim 4, characterized in that that the system offset at least a portion of the image between repetitive image scans of the camera (4) measures. 6. System according to claim 4 or 5, characterized in that that the part of the field of view is a strip (B) which is substantially at right angles to the raster lines of the TV camera (4) extends and the strip (B) is shorter than the field of view of the camera (4). 7. System according to one of claims 1 to 6, characterized in that the system has a first Memory (12) which stores signals representative of at least part of the image, and that a comparison unit (14) is provided which compares the signals stored in the memory (12) with those Signals of the image recording means (4) which are generated at a later point in time. 8. System according to claim 7, characterized in that the comparison unit (14) the signals in the memory (12) essentially compares with those signals from the image recording means (4) which are representative of an area of the surface (3) selected in accordance with with the movement of the vehicle (1). 9. System according to claim 7 or 8, characterized in that the comparison unit (14) is repetitive Compare the signals stored in the memory (12) with signals from the image recording means (4) in successive Points in time as long as the part (Aq) of the surface (3) is within the field of view of the image Is (4) is located in the middle of the take. 0 30030/0713 BATH ORIGINAL