AT509118B1 - METHOD AND DEVICE FOR DETECTING THE POSITION OF A VEHICLE IN A DEFINED AREA - Google Patents

Description

Austrian Patent Office AT509 118 B1 2011-12-15

The invention relates to a method for detecting the position of a vehicle in a defined area, wherein an absolute reference position of the vehicle and a relative movement of the vehicle are detected, wherein a digital image of the surroundings of the vehicle is recorded for detecting the absolute reference position, in the digital image at least one visual mark is determined and the reference position of the vehicle is determined with respect to the determined visual mark, and a device for detecting the position of a vehicle in a defined area, wherein at least one sensor device for detecting a reference position of the vehicle and is provided for detecting a relative movement of the vehicle, wherein an imaging sensor device is provided for determining the reference position.

The detection of the current position of a vehicle in a defined area is in a variety of applications of great importance. For example, determining the position of industrial trucks (for example, forklifts) in the field of warehouse logistics (warehouse management) is of great importance, since this enables automatic batch tracking. For this purpose, a variety of methods and devices are known, it is particularly known to detect an absolute reference position of the vehicle as well as the relative movement of the vehicle and thus to determine the current position of the vehicle using a dead reckoning system.

From DE 44 29 016 A1, a navigation system of driverless vehicles, in particular of transport systems in halls, known, which by means of a moving with the vehicle imaging sensor high-contrast objects in the environment, especially ceiling lights record. From the location of these ceiling lights then position and angle of the vehicle are determined. By using the high-contrast ceiling lights for the detection of an absolute reference position, the costs of the navigation system should be kept low.

Apart from the fact that the distinction - usually identical ceiling lights - via an optical sensor, e.g. in a CCD camera or photodiode arrays, actually not or at least only with a high error rate is feasible, a follower wheel is provided for detecting the relative movement of the driverless vehicle, which is connected via a vertical axis and about this rotatably connected to the vehicle. From the angle of rotation of the wheel about its axis and from the angle of rotation of the horizontal offset about the vertical axis, the position of the vehicle is thus to be determined via dead reckoning. In practice, however, such trailing wheels have proved to be extremely inaccurate (in particular due to problems with slippage and drift).

From WO 01/13192 A1 a method and a device for detecting the position of a vehicle is further known in which on the ceiling of a warehouse previously reflective markings must be attached, which can be detected by the vehicle when driving under a marker so that at this time a reference position can be detected and stored. In addition, according to the WO document, a wheel encoder is provided which detects the distance traveled by the vehicle at intervals; Furthermore, the angle of rotation of the vehicle is detected by means of a gyroscope. The current position of the vehicle can then be determined by means of dead reckoning from the reference position and the relative distance determined by means of vector addition. The disadvantage here in particular that the installation of the reflective markers in the ceiling area of a warehouse is very complex and expensive and also the detection of the reference position is not always guaranteed reliable. Further, in the measurement of the relative motion by means of the wheel encoder and a gyroscope, problems of slippage and drift (e.g., wheel spin) of the vehicle arise, so that an incorrect relative distance is often detected.

In order to eliminate these disadvantages in the detection of the relative movement, it is proposed in the 1/10 Austrian Patent Office AT509 118 B1 2011-12-15 EP 1 916 504 A2 to capture digital image data of a reference surface of successive discrete frames, then subdivide the first of two consecutive frames into a plurality of macroblocks to subsequently determine these macroblocks in the second frame, wherein the relative displacement of the vehicle can be determined depending on the displacement vectors of the positions of the macroblocks. In this way, although the measurement inaccuracies that occur when determining the relative movement by means of a wheel encoder and a gyroscope can be eliminated, but it is disadvantageous to a relatively complex image processing method, which is relatively slow and has a high memory requirement. However, it is particularly disadvantageous that, according to EP 1 916 504, the very complex and expensive installation of reflective markings in the ceiling area is still required to detect the absolute reference position.

A similar method or a similar device for detecting a reference position of a vehicle in a warehouse is further known from US 2007/10143006 A1. Here are a variety of transponders attached to the hall floor, with the help then a reference position of the vehicle to be determined. Again, this is a technically very complex system with a large number of sensors, which cause a very high installation and investment costs, especially in large area defined areas.

DE 103 46 596 A1 also proposes the detection of an absolute reference position with the aid of previously installed measuring strips. Furthermore, a relative position determination is carried out with the aid of an incremental-position detection unit by vectorial summation of incremental motion vectors, wherein a parameter for indicating the quality of the detected absolute position is determined. Depending on the quality of this parameter, the position of the vehicle in the predetermined range is output either in absolute mode or in incremental mode, i. Unfortunately, the absolute and relative measurement results are not merged with each other, but the measurement of poorer quality is completely discarded.

From US 2007/0150111 A1, an omnidirectional robot is still known, the bottom side has a so-called "optical flow" sensor, with which the relative movement of the robot is detected. However, the detection of a reference position in a predefined area is not provided here.

From DE 103 23 225 A1 and DE 103 23 418 A1 different methods for detecting placemarks are known by an upward-facing camera. Here, no position determination of a vehicle in a defined area, but it is selectively determined whether shapes of object marks are identical to those of reference marks, whether the distance between the object marks is identical to those between the reference marks, and whether the surrounding image of object marks with identical to the reference marks. In this way - if an object mark is identified as a placemark - the location of a robot cleaning device can be determined at certain points.

From DE 103 42 767 A1 a transponder-assisted positioning system is also known, in which a plurality of distributed disposed, introduced into the bottom of the warehouse transponder devices must be provided. Each transponder device stores information that at least indirectly represents the position of the corresponding transport device within the bearing. This is to a position with the goods within the warehouse can be stored, determined and stored. Since such a system thus requires the introduction of a large number of distributed transponders in a storage floor, such a system is extremely complicated and expensive.

The aim of the present invention is therefore to provide a method and an apparatus of the type mentioned, wherein the installation and investment costs for detecting an absolute reference position can be kept low, but at the same time a 2/10 Austrian Patent Office AT509 118B1 2011 -12-15 accurate positioning of the vehicle is guaranteed in the defined range.

According to the invention this is achieved in the method of the initially mentioned type in that for detecting the relative movement of the vehicle, a first digital image of a section of the defined area is recorded in the environment of the vehicle, determined in the first digital image at least one striking pattern is subsequently recorded a second digital image of a second section in the environment of the vehicle, and in the second digital image, the distinctive pattern is determined, so that determines the relative movement of the vehicle from the displacement of the distinctive pattern between the first and the second image becomes.

By capturing a digital image of the surroundings of the vehicle, i. a local section of the predefined area and the determination of a visual mark in the digital image, wherein the position of this visual mark remains unchanged in the defined range, the position of the vehicle with respect to the detected visual mark can be easily determined and constructive Thus, an absolute reference position of the vehicle can be continuously determined on the known position of the visual marking in the defined area, without the need for special reflective markings, transponders or the like. Must be laid in advance in the defined area. Advantageously, use can be made, for example, of using the method according to the invention in storage logistics of existing visual markings, such as markers already present on the floor in the warehouse (for example storage bin numbering), on the walls or on the ceilings of the store. In this case, no investment is required at all to attach the visual markers.

In addition to the absolute reference position to make a relative position determination in real time in a simple and accurate manner, a first digital image of a portion of the defined area in the environment of the vehicle is recorded for detecting the relative movement of the vehicle, in the first digital image at least determines a distinctive pattern, then a second digital image of a second section taken in the vicinity of the vehicle, and in the second digital image, the distinctive pattern determined so that the displacement of the distinctive pattern between the first and the second image, the relative movement of the vehicle is determined. Of course, at least one distinctive pattern is then also determined in the second digital image, which is subsequently determined in a further digital image at a later time. This method, i. the relative position determination by detecting the relative movement is - as well as that repeated to determine the absolute reference position - running. In principle, such methods for detecting relative movements in image processing or in optical measurement technology are known and are referred to as so-called "optical flow" measuring methods.

Since it can result from the necessary in the relative position determination due to the relative movement integration over time, a continuously increasing deviation, it is advantageous if the relative movement of the vehicle is determined with respect to the last detected absolute reference position and a combination of absolute reference position and relative movement, the position of the vehicle is determined in the defined range. In the event that no absolute reference position can be determined (because in the recorded digital image just no visual mark can be determined), therefore, the determined relative movement and the previously determined absolute reference position is used. By merging the two data streams, a predetermined measurement accuracy is ensured in a simple manner.

In order to be able to access the absolute reference positions predefined by the visual markings in a simple manner, it is favorable if the positions of the visual markings within the defined area are stored in a database.

In order to accelerate the determination of the visual marking in the digital image, it is advantageous if, depending on the determined relative movement, a probable position is predestined and the visual marking associated with this position is searched in the recorded image. Accordingly, the knowledge of the current position of the vehicle from the relative movement can be used for process acceleration. Not only does it speed up the speed of the position sensing process, it also increases the stability of the method. If a visual image can not be clearly identified from a current image, it can still be identified with a very high probability due to the recourse to the determined relative movement, and the vehicle can therefore be assigned an absolute reference position.

If the vehicle whose position is detected by means of the method according to the invention receives a product, it is advantageous if also an identification of the goods received by the vehicle for determining the absolute reference position is detected. Alternatively or additionally, other properties of the picked-up product, such as e.g. Shape, packaging or color of the goods. Thereby, e.g. with the help of a connected warehouse management or stacker control system, which stores the data of the recorded article, are closed to the current position and thus a further conclusion on the absolute position of the vehicle can be achieved, which in turn makes the measurement process plausible.

The device of the type mentioned is characterized in that an imaging sensor device is provided for detecting the relative movement of the vehicle. By providing an imaging sensor device for determining the absolute reference position and an imaging sensor device, in particular a digital camera, for detecting the relative movement of the vehicle, the already explained in connection with the aforementioned method according to the invention advantages, so that in order to avoid repetition of the above References. In particular, it is advantageous in this case if a digital camera is provided as the imaging sensor device. In this case, for example, a model of the model series DMK The Imaging Source can be used, which allows an image resolution of 640 x 480 pixels and a recording of grayscale images (8 bits per pixel). Color images are by no means absolutely necessary, but it would be possible to use a color digital camera to distinguish the visual markings not only by their shape but also by their color. Advantageously, a digital image is taken every 16 ms in order to be able to precisely track the relative movement even at higher speeds.

If the imaging sensor devices for determining the absolute reference position and / or for detecting the relative movement on a bottom surface on which the vehicle is moved, are used, for example, when using the device according to the invention in the field of warehouse management to markings in the ground area As in warehouses usually designations of storage areas or storage areas, eg AB17, are attached to the ground. Of course, however, boundary strips for identifying the routes in the camp can be detected as visual markers; It is also possible to record visual markings on a warehouse or hall ceiling.

The invention will be explained in more detail below with reference to a preferred embodiment illustrated in the drawings, to which, however, it should not be limited.

In the drawings: FIG. 1 is a flowchart of the steps of a method for detecting the position of a vehicle in a defined area; [0024] FIG. Fig. 2 is a view of a forklift with two imaging sensor devices; Fig. 3 shows schematically a perspective view of a forklift including visual

Marks.

In the flowchart of FIG. 1 it can be seen that with a digital camera 1 a 4/10 Austrian Patent Office AT509 118 B1 2011-12-15

Recording T the environment of a vehicle 4 (see Fig. 2 and 3) is made. Subsequently, in a further method step, a visual marking 2 is determined whose absolute position in the defined area is known. Depending on the position of the vehicle 4 to the detected mark then the absolute reference position 3 of the vehicle 4 is determined. This determination of an absolute reference position 3 is repeated continuously.

At the same time with another digital camera 5, a digital recording 5 'at a time t1 and a digital recording 5 " at a time t2 (time t1 is earlier than time t2). In the next step, a distinctive pattern 6 is determined in the digital image 5 'according to the so-called "optical flow" method. Subsequently, this striking pattern detected in the receptacle 5 'in method step 7 in the digital image 5 " determined and in a further step, the relative movement 8 and thus the relative position of the vehicle from the displacement (movement) of the pattern between the image 5 'and the image 5 " determined. In a further method step 9, the absolute reference position and the relative position are merged with one another and thus the position 10 of the vehicle 4 in the defined area is determined.

In Fig. 2 and 3 respectively a vehicle or a forklift 4 is outlined, which is provided with a digital camera 1 for determining its absolute reference position as well as a digital camera 5 for determining the relative movement and thus the relative position of the vehicle 4. The digital camera 1 for determining the reference position is here in the roof area of the vehicle 4, the digital camera 5 for detecting the relative movement in the region of the rear area of the vehicle 4, i. near the ground, arranged (the arrangement of the digital cameras 1, 5 can also be done at other locations of the vehicle 4). The position determination of the vehicle 4 in the defined area, i. for example, a warehouse, is of great importance in warehouse logistics, e.g. to ensure automatic identification of goods in a warehouse and, consequently, automatic batch tracking. As can be seen in FIGS. 2 and 3, the two digital cameras 1, 5 each receive a local section 11, 12 of the defined area, the two digital cameras 1, 5 being directed to the floor 13 in the preferred embodiment. The images taken by the two digital cameras 1, 5 are then transmitted to a data processing system 15, with which subsequently the evaluation of the images T, 5 ', 5 " taken by the digital cameras 1, 5 " takes place, as already described in connection with FIG. 1. The vehicle 4 can in this case receive a product 14, which is also associated with a visual identification 14 '; In addition, other visual properties such as e.g. Form, packaging, color of the goods 14, to be recorded.

As can be seen in Figs. 2 and 3, can be used as visual markings 2 in particular designations of storage areas or storage areas, which can be arranged mainly on the floor 13 or on the (not shown) storage or hall ceiling , As can be seen in FIG. 3, the visual markings 2 can also be arranged on a wall 13 'or a pillar, but here there is a risk that such visual markings are concealed by goods located in the warehouse.

As can be seen in particular in Fig. 3, provided as visual markers 2 in particular by means of a paint application provided numerals (and letters). These numbers (letters) whose position in the defined area, i. in the warehouse, is known and whose coordinates are stored in a database, are advantageously provided with a rectangular border 2 '. The edges of the rectangular border 2 'can hereby be used to determine the relative orientation of the marking to the vehicle 4, the numbers serving to identify the visual marking 2 and to resolve the inherent symmetry of the rectangular border 2'. The identification of a visual mark 2 is made e.g. with known pattern matching techniques (so-called "pattem matching"), or may be due to position relative to other visual markers. The position of the visual markings 2 relative to the vehicle 4 may be due to the geometrical characteristics of the individual mark - e.g. its dominant axis - or by the geometric properties of multiple visual markers 2, i. 5/10 Austrian Patent Office AT509118B1 2011-12-15

Arrangement to each other, to be determined.

The camera 5, however, determined striking pattern 6, which basically occur in any object with a surface structure. The floor 13 of a warehouse usually has such a continuous, changing surface structure, which is extremely well suited as an object for finding distinctive patterns 6. In order to determine the movement and thus the change in position of the vehicle 4 relative to the defined environment, two consecutive digital images 5 ', 5 " -as already described in connection with FIG. from the digital camera 5 and examined for matching prominent patterns. From the movement of these striking patterns and the time passed between the recordings can be closed to the relative movement between the vehicle 4 and the defined environment and thus the relative position of the vehicle 4 can be determined.

If the field of view of the digital camera 5 is large, then not only a shift, but also the orientation change can be determined from successive images, otherwise the rotation of the vehicle 4 either from several sensors, which are mounted at a greater distance from each other on the vehicle 4 , are determined, or derived from the kinematic limitations of the vehicle 4.

The determination of the absolute reference position and the relative movement and, as a result, the relative position of the vehicle is dependent on the properties of the defined area (number and position of the visual markings 2, characteristics of the surface structure of the base 13 for pattern recognition) and the travel paths Accordingly, each position measurements are determined with different frequency and quality. The more visual markings 2 are detected by the absolute measuring method, the more accurate the absolute position of the vehicle 4 can be determined, since not only an averaging of the measurement errors can take place, but also the relative positions of the markers 2 are known to each other. The more continuous and pronounced the surface structure is in the relative position determination by the relative measuring method, the more precisely can the relative movement and thus the relative position of the vehicle 4 be determined. The integration over time, which is necessary in this measurement method, can lead to a possible continuously increasing deviation (integration drift) from the actual position of the vehicle 4 in the case of suboptimal properties of the defined region.

Thus, to achieve a position determination within the defined range with a constant accuracy, as described in connection with Fig. 1, the two measuring methods are combined, i. E. in that, between two points in time at which the absolute reference position determination is carried out by the absolute measuring method, in order to determine the absolute position, in each case the last measured reference position is summed up to the relative movement measured in the meantime. Various methods are known for merging the measurement data, with data with statistical errors frequently using an extended Kalman filter.

With the help of this method can thus be determined without high investment costs in a simple and accurate way, the position of a vehicle in a defined range. 6.10

Claims (8)

Austrian Patent Office AT509 118 B1 2011-12-15 Patentansprüche 1. A method for detecting the position of a vehicle (4) in a defined area, wherein an absolute reference position (3) of the vehicle (4) and a relative movement (8) of the vehicle are detected , wherein for acquiring the absolute reference position (3) a digital image (1 ') of the environment of the vehicle (4) is taken, in the digital image (T) at least one visual mark (2) is determined and the reference position (3) of Vehicle (4) is determined with respect to the determined visual mark (2), characterized in that for detecting the relative movement (8) of the vehicle, a first digital image (5 ') of a section of the defined area in the vicinity of the vehicle (4 ), at least one distinctive pattern (6) is detected in the first digital image (5 '), then a second digital image (5 ") of a second detail in the vicinity of the vehicle 4), and in the second digital image (5 ") the distinctive pattern (6) is detected so that the displacement of the distinctive pattern (6) between the first and second images (5 ', 5 ") the relative movement of the vehicle (4) is determined. 2. The method according to claim 1, characterized in that the relative movement (8) of the vehicle (4) with respect to the last detected reference position (3) is determined and from a combination of absolute reference position (3) and relative movement (8) the position (10) of the vehicle (4) is determined in the defined range. 3. The method according to claim 1 or 2, characterized in that the positions of the visual markings (2) are stored within the defined area in a database. 4. The method according to any one of claims 1 to 3, characterized in that in dependence of the determined relative movement (8) a probable position is predetermined and the position of this associated visual marker (2) in the captured image (11) is sought. 5. The method according to any one of claims 1 to 4, characterized in that a marking (14 ') of one of the vehicle (4) recorded goods (14) for determining the absolute reference position (3) is detected. 6. A device for detecting the position of a vehicle (4) in a defined area, wherein at least one sensor device (1, 5) for detecting a reference position of the vehicle (4) and for detecting a relative movement of the vehicle (4) is provided, wherein a imaging sensor (1) is provided for determining the reference position, characterized in that an imaging sensor device (5) for detecting the relative movement of the vehicle (4) is provided. 7. Apparatus according to claim 6, characterized in that a digital camera is provided as imaging sensor devices (1, 5). 8. Apparatus according to claim 6 or 7, characterized in that the imaging sensor means (1, 5) for determining the reference position and / or for detecting the relative movement on a bottom-side surface (13) on which the vehicle (4) is moved, directed are. 3 sheets of drawings 7/10