GB2276734A

GB2276734A - A method and system of image-assisted position recognition

Info

Publication number: GB2276734A
Application number: GB9405169A
Authority: GB
Inventors: Ernst Lill
Original assignee: Deutsche Aerospace AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1993-03-19
Filing date: 1994-03-16
Publication date: 1994-10-05
Also published as: FR2702856A1; GB9405169D0; DE4308753C1

Description

2276734 1 A method and system of Imaqe-Assisted Position Recoqnition The

invention relates to a method, which permits the orientation of an object-related coordinate system relative to a fixed coordinate system to be determined and to be evaluated for correction of a target direction (advance working direction).

In the general prior art, determination of an objectrelated coordinate system, which is not fixed in its spatial position, has been achieved in relation to a fixed coordinate system. An example of this is controlling advance working in tunnelling excavation. In this case in - a planned linear advance, a precisely aligned laser beam fixes the desired direction of advance. In this so- called beam guidance process, the deviation of reference points applied to the rear of an advance working machine, which are predominantly optical detecting elements with an electronic plotter, is measured relative to the target direction determined by the laser beam. However, this method does not directly measure rolling, pitch and yaw movements, but only detects them indirectly and, moreover, with a certain delay because of the resulting course of travel. The result of this is that the advance working machine does not advance in a straight line as desired. In reality, 2 its course varies three-dimensionally around the laser beam.

A further disadvantage of this method is that a "visual connectioril between the laser and the optical sensor elements attached to the rear of the advance working machine is necessary. If this is not ensured, for example, because of a bend in the course of travel, then the laser must be repositioned involving time-consuming measurement and beam adjustment.

Moreover, the use of laser units is strictly regulated on the basis of the "eye safety" involved and therefore may often not be used. The abovementioned disadvantages could be avoided by using triaxial gyro systems. However, this is not expedient in most practical applications because of rough environmental conditions, because of the requirement for periodic coordinate checks and corrections and, not least, for reasons of cost.

The object of the invention is to provide a method and system for achieving the desired determination and evaluation in which the axis orientation of a manoeuvrable object, e.g. a tunnelling machine, to a fixed coordinate system of an observer is determined substantially continuously, practically without effort 3 but also with relatively high precision.

This object is achieved in that the orientation of a coordinate system related to an object which is to be controlled in its movement is determined relative to a fixed coordinate system and evaluated for correction of a target direction (advance working direction), wherein the object to be controlled is rigidly connected to a three-dimensional body which is provided with optical elements as optical reference points and the position of the optical elements is determined with high precision by means of an image recording unit arranged in visual connection therewith at a defined distance from said body, and, in a following image processing unit, values are determined from axis orientations of the coordinate system of the object to be controlled relative to the coordinate system of the image recording unit and these values are input into a control unit to control the movement of said object.

Specific embodiments, developments and examples are 20 explained in the following description and are sketched in the figures of the drawings, in which:

Figure 1 is a block diagram showing a basic representation of an advance working machine and an image recording unit with its connections and system of 4 coordinates; and Figure 2 shows three examples (2a - 2c) of the orientation of the optical norm on the rear of the advance working machine.

The basic concept of the invention is to identify a three-dimensional body with a form adapted to its bearer, in this case a tunnelling machine VM, by means of optically prominent elements such as light-emitting diodes etc., and thus produce a so-called optical norm.

This norm is then observed continuously during advance working by means of an image recording unit BAE and thus information concerning its respective axis orientations (coordinate system KONK) relative to the coordinate system of the observer (coordinate system Kl,.) is constantly received and input into a control unit SE to correct the target tracking.

In this case, orientation of the coordinate system of the unit VM, whose movements are to be controlled and which is equipped with the abovementioned optical norm ONK, is determined simply and with high precision by optically detecting the latter by means of the image recording unit BAE and the following image processing unit BV.

Since the imaging data of the recording unit BAE and the r 1 geometric design of the ONK are known, the distance between the object and the recording unit is calculated, in addition to the axis orientation, directly from the Image data. The values thus obtained are used in an advantageous manner for high-precision control of the movement cycles. The above-described process is versatile in use and application. An embodiment is described below and the invention explained on the basis of a tunnelling machine.

The embodiment is sketched in Figure 1. The optical norm ONK already explained above is firmly secured to the rear of the advance working machine M The structure of this optical norm ONK is such that its axes may be clearly coordinated or assigned. A sphere-like structure, for example, would be completely unsuitable because of its high degree of symmetry. In this case, it is in the form of a pyramid, as may be seen from Figures 2a to 2c.

The position of the optical norm ONK relative to the advance working machine VM as well as that of the optical reference points LQ1 to LQ5 relative to one another is precisely measured and stored in the image processing unit. Light sources LQ1 to LQ5, the emission behaviour of which is interpreted in a spectrally and temporally defined manner for clear, individual identification, are arranged at the corner points, which at the same time 6 represent the aforementioned reference points for the measurement process. The emission behaviour of each individual light source is purposely activated where needed by the control unit.

The image recording unit BAE equipped with a variable focal length is located at a distance, fixed according to application, of 50m, for example. The magnification factor (zoom) of the optical system is exactly determined by a tap element and passed on to a system computer SR.

The location and direction of observation of the image recording unit BAE are determined exactly by fixing the coordinate system KBmE. The imaging of the optical norm ONK will generally fill the entire image format, because the optical system of the image recording unit BAE has a variable focal length.

If the direction of observation is perpendicular to the base surface of the optical norm ONK, which is pyramidshaped in this case (see Figure 2a), then the reference point LQ5 is shown in the centre of the image, as in Figure 2b. Every change in position and direction of the ONK and therefore of the advance working machine VM relative to the BAE unequivocally changes the position of all imaged reference points LQ1 to LQ5. For example, if the longitudinal axis of the advance working machine VM relative to the direction of observation is tipped 1 7 downwards, then the resulting position of the reference points is as shown in Figure 2c. This is def ined with known algorithms, and from the data thus obtained the system computer SR determines the exact distance and axis orientation of the optical norm ONK relative to the reference coordinate system of the image recording unit BAE.

If planning data concerning the target course of the advance working are stored in the system, then these can be compared with the actual data, and if there are deviations, correction signals are passed to the control device of the advance working machine M This also ensures automatic advance working with optimised plan data accuracy.

In a second embodiment, the image recording unit BAE with defined axis direction is rigidly mounted on the moving object - in this case, the advance working machine VM and the reference points to be measured LQ1 to LQ5 are fixedly arranged in their spatial position. The measurement process etc. is identical to that described above.

In a special alternative embodiment, where the course of advance working is curved but there is a guaranteed visual connection, the axis of the image recording unit 8 BAE is tracked manually or automatically. Changes in the direction of observation are exactly determined in each case and transmitted as updated data to the system computer for evaluation of the new configuration. If quick movement cycles are to be evaluated, a target tracking program operating either according to the correlation method or according to the intensity method ensures constantly optimised, reliable tracking of the image recording unit BAE. The algorithms suitable for this belong to the prior art.

These measures cause the imaging of the optical norm ONK to fill the entire image format. In this way, the resolution given, for example by the number of pixels of the CCD element, is used for maximum measurement accuracy.

The system can have many different forms. Hence, for determining the position of the optical norm ONK, the projection of the reference surfaces fixed by reference points LQ1-LQ5 may be brought closer to the image plane of the image recording unit BAE, and these reference surfaces can be individualised, e.g. by coloration or emission behaviour, in such a way that they can be recognised quickly and unequivocally on the basis of these characteristics by the image processing.

9 A high degree of measurement accuracy with respect to axis orientations and distance is ensured by adapting the optical imaging of the optical norm ONK to the sensor element of the image recording unit, e.g. a CCD. The distance between the optical norm ONK and the image recording unit BAE is determined by defining and allowing for the imaging parameters of the image recording unit BAE, this being tracked manually or automatically in such a way that the norm is optimally imaged, the changes in angle precisely defined and these data - as already mentioned - are allowed for in the control of the advancing movement of the object.

If the image recording unit is mounted on the moving object, then in a further alternative embodiment of the invention the reference points naturally present after initial determination of the position of the norm or those reference points created during the advancing movement of the VM are measured first in their position relative to the norm. This produces a first set of optical support points. In the course of further advancing movement further sets of reference points are collected and measured relative to the location coordinates of their immediate predecessors. With this procedure, a succession of support points in space is obtained for the image-assisted position recognition, which then permits the advance working machine to be manoeuvred even when the original visual connection between the image recording unit BAE and the optical norm ONK has been broken.

t 11

Claims

Claims:

1 A method by which the orientation of a coordinate system related to an object which is to be controlled in its movement is determined relative to a fixed coordinate system and evaluated for correction of a target direction (advance working direction), wherein the object to be controlled is rigidly connected to a three-dimensional body which is provided with optical elements as optical reference points and the position of the optical elements is determined with high precision by means of an image recording unit arranged in visual connection therewith at- a defined distance from said body, and, in a following image processing unit, values are determined from axis orientations of the coordinate system of the object to be controlled relative to the coordinate system of the image recording unit and these values are input into a control unit to control the movement of said object.

2. A method according to Claim 1 wherein the threedimensional body provided with the optical elements is constructed in such a way as to ensure clear coordination of its axes.

A method according to Claim 1 or 2 wherein the position 12 of the body relative to the object to be controlled and the position of the optical reference points relative to one another are precisely measured and the values obtained are stored in a memory of a system computer.

4. A method according to Claim 1, 2 or 3 wherein the image recording unit has a sensor axis which may be tracked manually or automatically.

5.

A method according to Claim 3 wherein optimised tracking of the image recording unit is conducted continuously by means of a target tracking program in the system computer according to a correlation method or according to an intensity method.

6. A method according to any of claims 1 to 5 wherein the object to be controlled is an advance working machine, and the image recording unit is mounted on the rear of said machine, and wherein the optical reference points already present in the surrounding area of the advance working machine or those created artificially and captured by the image recording unit are measured firstly in their position relative to the body, depending on the speed of advancing movement and course of travel, and measured in relation to one another in further travel to ensure that the position of the machine is determined even when the direct visual 13 connection between the image recording unit and the body has been broken.

A system for implementing the method according to Claim 1 wherein a threedimensional body is rigidly secured to the rear of an advance working machine, at the corner points of which light sources are arranged, the emission behaviour of which is interpreted in a spectrally and temporally defined manner for clear, individual identification, and at a defined distance from the advance working machine an image recording unit equipped with a variable focal length is provided.

8. A system according to Claim 7 wherein the body is provided in the geometrical form of a pyramid, at the corners of which the light sources are arranged.

9. A system for implementing the method according to Claim 1 wherein the image recording unit is equipped with a variable focal length defined in its axis orientation and is mounted on the rear of an advance working machine, and the light sources to be measured are arranged as reference points fixed in their spatial position.

10. A system according to any of Claims 7 to 9 wherein the emission behaviour of the individual light sources is 14 purposely activated by a control unit.

11. A system according to any of Claims 7 to 10 wherein the magnification factor of the optical system of the image recording unit is determined by a tap element and input into a system computer SR.

12. A method of image-assisted position recognition substantially as hereinbefore described with reference to the accompanying drawings.

13. A system of image-assisted position recognition substantially as hereinbefore described with reference to the accompanying drawings.

p