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FIELD OF THE INVENTION 
     The invention relates to a localization system for localizing an underground object for an earth-moving machine. 
     BACKGROUND 
     When carrying out earthworks and especially excavation work, it is necessary to know where underground objects, such as supply lines laid underground, are buried, in order to prevent damage, for example to supply lines and/or to the earth-moving machines used. Often, these objects are incompletely or wrongly documented or not documented at all. Accordingly, the terrain to be worked must be investigated before the beginning of the earthworks with respect to underground objects. The investigation is effected in general on the basis of the detection of electromagnetic fields which can be coordinated with the objects, for example by means of commercially available hand-held locating devices. 
     However, such scanning of terrain is too time-consuming and expensive, in particular for the working of large areas. It is therefore usual to mount localization devices or locating devices, such as cable detectors, directly on the earth-moving machine—for example an excavator—and to detect the buried objects in the course of the ongoing earthworks. In order to be very certain to avoid encountering objects during excavation, locating devices by means of which the depth of the buried objects can also be determined are advantageously used. For this purpose, locating devices are known which have two antennae arranged a distance apart along a perpendicular to the object. The distance from the object to the locating device can be derived from the field conditions detected by means of the antennae and the known fixed spacing of the antennae. Advantageously, the object data are stored and recorded, with the result that terrain documentations, such as maps, can be prepared or supplemented. 
     Earth-moving machines, such as, for example, excavators, are sufficiently well known from the prior art. The invention relates to earth-moving machines having a working part—in particular an excavator arm—which has an earth-moving part, such as an excavator bucket. The earth-moving part is pivotably fastened, for example, to a lower boom component of the working part. In particular, the working part has two or three members as boom components, which can be moved by means of hydraulic adjustment mechanisms. 
     US 2006/0265914 A1 describes a system for monitoring a predetermined limit during earth-moving work which is carried out by an earth-moving machine. For this purpose, signal-transmitting devices which determine the limit or a limit range by their position are arranged in the terrain, in particular underground. By means of a receiver device, the signals emitted by the transmitting devices are received and are transmitted to an evaluation unit, the evaluation unit deriving a position of the signal-transmitting devices from the signals received and deriving information about the limit from said position. It is proposed to fasten the receiver device on the working machine itself or alternatively to position it in a mobile manner in a separate location from the working machine, for example on a further separate vehicle. 
     For use for locating, for example, an underground supply line generating a magnetic field, the system disclosed in US 2006/0265914 A1 is, however, unusable since, for detection of a supply line, requirements differing from a transmitter-receiver system are necessary. 
     U.S. Pat. No. 6,633,163 describes an earth-moving machine having two magnetic field detectors arranged at different heights on the machine. The comparison of the detector measurements provides information about the closeness of a field generator to the earth-moving machine. With the system described, the relative position of the field generator to the earth-moving machine is determined. The determination of the distance from the field generator to the earth-moving machine or the depth of the field generator is not mentioned in said US patent. Furthermore—owing to the arrangement of the detectors directly on the machine—the system is suitable only for earth-moving machines which pull a working part behind them. 
     U.S. Pat. No. 5,592,092 describes two sensors mounted a distance apart on the bucket of an excavator and intended for detecting magnetic fields of underground objects. From the known distance between the sensors, the difference between the detected field magnitudes and the bucket position, the distance from the bucket to the object is derived. Since the sensors are mounted on the excavator bucket, they are, depending on the bucket position, not perpendicularly above the object. The bucket position must therefore be taken into account when determining the distance. Moreover—owing to the fixing directly on the bucket—there is the danger that the sensors would be damaged during the excavation work. 
     summary 
     An object of the invention is to provide an improved damage-stable localization system for an earth-moving machine, by means of which, when carrying out earthworks, underground objects are detectable in the terrain which is or could be worked by the respective instantaneous bearing and position of the earth-moving part. 
     A further object is the provision of a damage-stable localization system for an earth-moving machine, by means of which the distance to underground objects can also be determined. 
     These objects are achieved by the subjects of Claim  1  or of the dependent claims or the achievements are further developed. 
     According to the invention, a localization system for an earth-moving machine has a detector component pointing in the direction of the earth-moving part, such as an excavator bucket, and having a defined detection direction, an arithmetic component and a display component, for example for displaying or forwarding distance information. The detector component is mounted via a fastening component on a lower member of the working part—to which the earth-moving part of the machine is fastened—so that the detection direction of the detector component is aligned substantially parallel to the longitudinal direction of the lower member, which is the lower boom component of the working part. The fastening component is designed for arrangement, in particular detachable fastening, on the lower boom component of the excavator arm of the earth-moving machine. Advantageously, the fastening component can be arranged on the working part in such a way that the detector component is positioned so as to be as safe from damage as possible. As a result of the arrangement of the detector component on the lower member of the arm, the detection axis being aligned parallel to the longitudinal axis of the lower member, it follows that the detection axis and hence the defined detection direction of the detector component point to the earth-moving part and to the terrain to be worked therewith. This arrangement position also ensures that contact and collision with the earth-moving part or with the terrain itself are prevented, which otherwise might lead to damage to the detector. Thus, with an arrangement which is not very complex and is stable to damage, a localization system having a detector component is provided, which detector component detects objects in any terrain which is or could be worked at the instantaneous bearing and position of the earth-moving part by the latter. Scanning of the terrain to be worked as a separate operation before the working of the terrain is not necessary with the use of a localization system according to the invention. 
     An advantageous embodiment of the detector component is an arrangement of two antennae arranged a distance apart on an axis along the longitudinal direction of the lower member of the working part, the detection direction of the detector component being defined in the direction of the axis. Since the antennae are mounted a distance apart on the axis, the detected strengths of the magnetic field emanating from an object are of different magnitudes and different positions along the axis. On the basis of the difference between the magnetic field strengths detected by the two antennae a distance apart and the distance of the antennae relative to one another, the distance from the object to the detector component can be determined. 
     Electromagnetic fields which can be coordinated with the objects are, for example, magnetic fields generated by alternating currents or induced magnetic fields. Thus, supply lines laid underground, such as high-voltage and low-voltage cables, telecommunication cables and water pipes, or alternative underground objects can thus often be located on the basis of time-variable magnetic fields of the lines. The magnetic fields are generated, for example, as a result of current flows through the cables, as in the case of high-voltage or low-voltage cables operated with alternating currents. Alternatively, the fields are fields generated by means of application of electromagnetic signals to the lines or fields reflected by the lines. The application is effected via direct application to current-conducting supply cables or by means of induction of a magnetic field in the cable. A magnetic alternating field of a current-conducting supply cable can also be induced by signals from remote transmitters, such as radio signals from radio transmitters. Moreover, the fields may emanate from transmitters on or in the lines. For example, a conductor is introduced into non-conducting supply lines, such as clay pipes or plastic pipes—or the conductor is led next to the supply lines—and fed with alternating current. 
     The strength of the magnetic field is a measure of the distance of the source—i.e. of the line or of the transmitter—from the measuring location. For a straight conductor through which current flows, the strength of the magnetic field decreases inversely proportionally to the distance d−B≈k/d; in the case of a magnetic dipole field, it decreases inversely proportionally to the third power of the distance d−B≈k/d 3 , where k designates a proportionality constant and B the magnitude of the magnetic field. 
     By means of a detector component having antennae a distance apart, as described above, a magnetic field of a source is detected at two measuring positions a distance apart, i.e. for two distances to the source. Subsequently, the ratio of the measured strengths of the fields can be calculated so that the proportionality constant cancels out. From the measured fields and the known relative distance of the antennae, the distance to the source can then be determined. 
     A detector component of a localization system according to the invention having three—or more—antennae permits the determination of the distance of an object with greater accuracy than a detector component having two antennae. 
     If the detector component has antennae for detecting the field, the antennae may represent uniaxial, biaxial or triaxial antennae, biaxial antennae being designated as x-y antennae. By means of multiaxial antennae, the field can be determined in a plurality of spatial directions so that not only the distance but also a direction vector to an object can be determined and objects can be detected independently of direction. 
     The detector component of the localization system according to the invention may also comprise magnetic field detectors, such as magnetometers or Hall sensors, as an alternative to the antennae. 
     The detector component may also be formed with a transmitter and receiver, in particular for distance measurements. 
     For example, the detector component is a radar, objects being detected by means of radiation emitted by a transmitting unit of the detector component and received by a receiving unit of the detector component. 
     Optionally, the detector component additionally comprises a laser rangefinder, a GPS system or other optical surveying systems in order to measure the distance to the—original or worked—terrain. If the distance to an object can be determined by means of the detector component, the measurement of the position of the detector component or the working part relative to the terrain can be used in order to determine the depth of the object. The working part can then be controlled according to the depth determined. 
     A position determination of the working part can also be carried out by alternative methods customary in machine control. For example, measuring a reflector on the working part is known. A position determination—for example of an excavator arm as the working part—by means of tilt sensors and pressure sensors is likewise known. 
     The localization system according to the invention is in the form of a localization system for an earth-moving machine. The earth-moving machine is in particular an excavator having an excavator arm as a working part. Usually, an excavator arm is formed from a plurality of boom components and an excavator bucket as the earth-moving part, which in each case are vertically adjustable. The boom component on which the earth-moving part is directly fastened is designated as the lower boom component. The fastening component of a localization system according to the invention is preferably mounted on the lower boom component in such a way that it is arranged as close as possible to the bucket but does not come into contact with the bucket in any position of the excavator arm. 
     The fastening component is, for example, in the form of a metal plate and it can be fastened magnetically on the working part. Alternatively, the fastening component may be in the form of a frame-like holder. A fastening component which is integrated in the working part and on which the detector component can be fastened is also possible. In a simple case, the fastening component consists of a rope or of clamps for fastening the detector component on the working part. A formation of the fastening component as a housing is useful, for example, for housing the arithmetic component and housing batteries or tools for mounting the fastening and/or the detector components. Likewise, the fastening component and the detector component can be arranged in a common housing. 
     The localization system according to the invention furthermore comprises a display component for displaying the detection of the detector component. If the detection is only the detection of an electromagnetic field, the display component can generate a warning signal on detection. The warning signal is, for example, an acoustic or optical signal for a user, such as an excavator driver. In addition or alternatively, the warning signal may be a signal for a control device of the earth-moving machine, with the result that, for example, the movement of the machine and/or of the working part thereof is stopped. 
     Optionally, the localization system according to the invention comprises an arithmetic component. By means of the arithmetic component, the detection of the detector component is further processed. For example, the distance to the object is derived from the detection and is optionally stored. The arithmetic component can communicate via appropriate interfaces with the display component, which then displays or forwards the information derived by means of the arithmetic component, such as distance information. 
     For display for a user, the display component is, for example, in the form of a graphic display and is arranged in a driver&#39;s cab. On the display, the detection can be displayed as a warning signal, for example by means of flashing or lit-up lamps. The distance information can be displayed figuratively in a terrain model, by means of indicator lamps or as numerical values. In addition or alternatively, an acoustic alarm can be provided. 
     The arithmetic component is, for example, a microprocessor. Furthermore, a controller may be coordinated with the arithmetic or display component. 
     Detector component, display component and optionally arithmetic component and optionally controller have in each case devices for communication. The devices may be cable connections or wireless interfaces, such as Bluetooth or CANBUS. For example, the components also communicate via radio signals. The communication takes place among the individual components. The communication can furthermore take place to external devices, such as a control system operated by a user, or to control devices of the earth-moving machine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The localization system according to the invention is described or illustrated below, purely by way of example, with reference to working examples shown schematically in the drawings. Specifically, 
         FIG. 1  shows an excavator as an earth-moving machine having a fastening and detector component arranged according to the invention; 
         FIG. 2  shows an excavator arm which is present in a working position, with components of a localization system according to the invention; 
         FIG. 3  shows an excavator arm which is present in a further working position, with components of a localization system according to the invention; 
         FIG. 4  shows a detector component having two x-y antennae arranged along an axis and the detection cone which follows therefrom and within which objects are detected; 
         FIG. 5  shows an excavator having a fastening component, a detector component and a display component of a localization system according to the invention; 
         FIG. 6  shows a further working example of a localization system according to the invention; 
         FIG. 7  shows, in four partial figures, working examples relating to components of a localization system according to the invention; and 
         FIG. 8  shows a working example for a display component of a localization system according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an excavator  2   a  as an earth-moving machine having a localization system according to the invention. The excavator  2   a  travels over a terrain  10  on which excavation work is to be carried out. The excavation work is effected, for example, as part of the construction of a road or the laying of cables or pipes. A supply line  1  has already been laid as an underground object under the terrain to be worked, an electromagnetic field emanating from the supply line  1 . The excavator  2   a  has, as a working part, an excavator arm  3   a  with an upper boom component  11   a , a lower boom component  12   a  and an excavator bucket  13   a , which in each case are vertically adjustable by means of hydraulic cylinders. A fastening component  4   a , which here is in the form of a housing fastened magnetically to the second boom component, and a detector component  5   a  are arranged as components of the localization system according to the invention on the lower boom component  12   a . The detector component  5   a  is arranged on the fastening component  4   a  in such a way that the detection axis and hence the detection direction of the detector component  5   a  are substantially parallel to the longitudinal direction of the lower boom component  12   a . Consequently, the detection direction always points in the direction of the excavator bucket  13   a  and in the direction of the terrain to be worked with the excavator bucket  13   a . The detector component  5   a  is formed for the detection of electromagnetic radiation. As soon as radiation is detected, the distance of the source is calculated by means of the arithmetic component arranged in the fastening component  4   a —in the form of a housing—and the information is forwarded, for example, to the display component—not shown here—or to a control device of the excavator  2   a . The forwarding is effected via radio—e.g. via Bluetooth interfaces. Display component, detector component  5   a  and fastening component  4   a  could also be arranged in a common housing. 
     The diagram in  FIG. 2  shows an excavator arm  3 b in a working position with components of a localization system. The diagram shows that the detector component  5 b of the localization system is arranged in such a way that it is arranged as close as possible to the excavator bucket  13 b but sufficiently far away that it does not come into contact with the bucket. The detection cone  7 b within which objects can be detected is furthermore shown. The terrain which is being worked or could be worked in the instantaneous position of the excavator bucket  13 b is scanned in each case. 
       FIG. 3  shows an excavator arm  3   c  in a further working position with components of the localization system. Furthermore, a reflective element  14  is mounted. The reflective element  14  can be measured by means of a tacheometer and the position of the element thus determined. Further sensors are coordinated with the excavator arm  3   c : in each case pressure sensors  15 ,  15 ′,  15 ″ are coordinated with hydraulic cylinders—not shown—for adjusting the upper boom component  11   c  and the lower boom component  12   c  of the excavator arm  3   c  and the excavator bucket  13   c . Furthermore, in each case a tilt sensor is coordinated with the upper boom component  11   d , the lower boom component  12   d  and the excavator bucket  13   c . The tilt sensors are not shown. By means of the reflective element  14  and the sensors, the position of the lower edge of the bucket can be calculated from the position of the reflective element  14  and the tilt information on the basis of simple geometry. If the distance to an underground object is now determined via the localization system, the depth of the object can be determined with the knowledge of the position of the excavator arm  3   d —and therefore of the detector component  5   c  which has a fixed positional relationship with the excavator arm  3   c.    
       FIG. 4  shows a working example of a detector component  5   d  according to the invention having two x-y antennae  20   a ′ and  20   a ″ arranged a distance apart on an axis, with the result that the detection direction  30  of the detector component  5   d  is defined along the axis, and the detection cone  7   d  within which objects are detected. 
     In  FIG. 5 , an excavation is carried out in a terrain  10 ′ by means of the excavator  2   e . The detector component  5   e  is arranged via the fastening component  4   e  on the excavator arm, on the lower boom component  12   e  which is connected in a rotatable manner to the bucket  13   e . According to the following  FIG. 7C , the detector component  5   e  is provided with antennae and a laser rangefinder. By measuring the distance to the terrain—in this case, for example, to the excavated terrain  10 ″—with the laser rangefinder, the depth of a detected object can also be determined from a distance of the object which is calculated from the detection data of the detector component  5   e . The diagram shows that the arrangement of the detector component  5   e  via the connecting element  7   e  and the fastening component  4   e  on the boom component  12   e  is such that the detector component  5   e  does not come into contact with the bucket  13   e  even in an end position of said bucket—and is therefore protected from damage by the bucket  13   e . During transport of the excavator—when the excavator is therefore not being actively used—the detector component  5   e  and optionally the further components can be simply removed, for example for protection against theft. 
       FIG. 6  shows a working example of a localization system according to the invention having a fastening component in the form of housing  4   f  for the arithmetic component. The detector component  5   f  is arranged on the housing  4   f . According to the preceding Figures, the fastening component is mounted on the lower boom component  12   f  of the excavator  2   f . The housing  4   f  as a fastening component has, on the back of the housing, magnetic strips via which it is fastened magnetically to the front boom component  12   f . The magnetic fastenability permits rapid and easy mounting and removal of the housing  4   f . A display component  6   f  which comprises a graphic display is arranged in the driver&#39;s cab of the excavator  2   f . The display component  6   f  is formed, for example, according to the working examples shown below in  FIG. 8 . 
       FIG. 7A  shows in somewhat more detail an embodiment of the fastening component  4   f  which is in the form of a housing for a battery compartment  16  and an arithmetic component  8   f.    
       FIG. 7B  shows the detector component  5 F which has a first antenna  20   b ′ and a second antenna  20   b ″ which are arranged a known distance d apart in a housing  18 .  FIG. 7C  shows a working example of a detector component which likewise has first and second antennae  20   c ′,  20   c ″, which are arranged a fixed distance apart, and additionally a laser rangefinder  19 . The antennae are designed, for example, in each case with a coil or with a plurality of coils as the uniaxial antenna  20   d , the x-y antenna  20   e  or the triaxial antenna  20   f  from  FIG. 7D . A time-variable magnetic field of an underground conductor induces a voltage between the ends of the coil or of the coils of the antennae, which induced voltage depends on the magnitude of the magnetic field. A distance value of the conductor is derived from the antennae outputs in the arithmetic component  8   f . The derivation may be, for example, simply an assignment of a distance value to the antennae outputs. 
       FIG. 8  shows a working example for a display component  6   g  of a localization system according to the invention. The display component  6   g  has a graphic display  6   g ′ and is in the form of a display and control unit. A multiplicity of LEDs as visual display means and a plurality of push-button switches for selecting settings are formed on the graphic display  6   g ′. Here, the push-button switches comprise a “mute” push-button switch  21  for silencing an acoustic alarm, which is provided in addition to the visual alarm signals. With a further push-button switch  22 , the localization system can be switched to “standby” or “active”. LEDs  23  associated with the push-button switches indicate which setting is active by lighting up. Two further LEDs  24  indicate the battery level of the arithmetic component  8   f  and detector component  5   f  and of the display  6   g ′. The LEDs  25  in the upper region of the display  6   g ′ are a visual display of distance information with regard to an underground object detected. They are divided into three colour sections—green, yellow, red. If the green LEDs  25 ′ light up, an underground object has been detected which, however, is still at a distance of more than 30 cm. The lighting up of the yellow LEDs  25 ″ indicates that the object has now assumed a distance of less than 30 cm. When the red LEDs  25 ′″ light up, the object is less than 10 cm away and the highest alarm level prevails.

Summary:
The invention relates to a localization system for localizing an underground object for an Earthmoving machine comprising a working part. Said localization system comprises a fastening component and a detector component. The fastening component can be arranged on the working part for example by means of magnets. The detector component is adapted to detect the object using an electromagnetic field that can be associated with the object and is arranged on the fastening component so as to swing like a pendulum, thereby effecting an alignment of the detector component under the effect of gravity. Optionally, the localization system comprises an arithmetic component for deriving a distance information of the object from the detected value. The localization system also comprises a display component for displaying and/or forwarding the detected value and/or the distance information.