JPH11208895A - Relative position measuring device for continuous unloader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple relative position measuring device for a continuous unloader, for accurately measuring the relative positions of a perpendicular arm of the continuous unloader and a hold hatch opening. SOLUTION: Two wide angle scanning-type distance meters 12 are attached on the tip of an unloader boom so that the scanning directions may be perpendicular to each other, and a two-axle inclinometers 14 is attached. The scanning surfaces of the distance meters 12 are so arranged as to include the edge of a hatch, the edge position of a hatch opening is found from a three-dimensional coordinate of a target point found by correcting the outputs of the distance meters 12 by the output of the inclinometer 14, and the relative positions of a perpendicular arm and the hatch opening is calculated. An image obtaining means 13 is provided on the tip of the unloader boom, the obtained image is processed, the edge part of the hatch is extracted and displayed with the image to a monitor device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a relative position between a vertical column of a continuous unloader and a hatch opening of a work vessel to ensure safe operation of the continuous unloader.

[0002]

2. Description of the Related Art As an unloader for unloading bulk cargo loaded in bulk in a ship's hold, a rotating boom is provided on a frame running parallel to the quay, and a vertical end such as a bucket elevator is provided at the tip of the unloader boom. It is known to provide a vertical arm containing a mold conveyor, and to provide a scraping device at the lower end of the vertical boom. This continuous unloader vertically inserts a vertical arm from the hatch opening of the hold, and moves the scraping device so that it reaches every corner of the hold, continuously scraping loose items and loading it into the receiving part of the vertical conveyor. When dropped, the conveyor transports the loose objects vertically, and then unloads them via a horizontal conveyor provided in the unloader boom.

[0003] Since the shape of the interior of the hold is different in each hold, it is necessary to operate the unloader in accordance with the individual hold in order for the scraping device to reach every corner and unload the loose items in the hold. Need to do. Therefore, for the automatic operation of the continuous unloader, a playback control is selected in which the apparatus stores the trajectory when the operator operates one cycle by manual operation via the teaching box and then automatically reproduces the operation. Often.

In the above-described automatic operation, the relative position between the scraping device and the hold must be the same between the time of teaching operation and the time of playback operation. However, in practice, the position and attitude of the ship are constantly changing due to the difference in the loading capacity, the change in the load due to unloading, the ebb and flow of the tide, the pitching and rolling of the hull by the action of waves, and the like. For this reason, not only can not be efficiently discharged, but also there is a danger that the scraping device will collide with the inner wall of the hold, and it has been difficult to automatically operate the continuous unloader. Therefore, in order to succeed in the automatic operation of the continuous unloader, it is necessary to accurately measure and compensate for the relative relationship between the ship's hold and the unloader, whose position and attitude change every moment.

[0005] Japanese Patent Application Laid-Open No. Hei 5-301641 discloses that in order to perform such a measurement, a scanning type optical distance meter is attached to the tip of the unloader boom, and the distance to each side of the hatch opening and its scanning angle are measured. An apparatus is disclosed that calculates a relative position between a vertical arm and a hatch, controls the relative distance so as not to be smaller than a predetermined value, thereby preventing danger and performing a cargo handling sequence based on the measured value.

However, since the unloader boom is long, the tip of the boom twists due to the unloading load. For this reason, the scanning surface of the distance meter tilts forward, backward, left, and right in accordance with the load that changes during unloading, causing a deviation in the measurement of the distance and the scanning angle. The device disclosed in the above publication has an error due to the twist, and it is difficult to maintain high measurement accuracy. Also, processing a radial distance data sequence centered on the instrument position obtained from the scanning rangefinder to determine the position at which symmetrical data is obtained as the center of the hatch opening, but the shape of the hatch combing is not the same. In some cases, the edge position cannot be specified. Even when an obstacle is present at the edge portion, there is a possibility that the position of the hatch edge is erroneously recognized by measuring as it is.

Japanese Patent Application Laid-Open No. Hei 9-14920 discloses that
An apparatus is disclosed in which an edge of a hatch opening is captured using a single imaging device, and a relative position of the hatch with respect to a vertical arm is measured by trigonometry. This method requires a large number of imaging devices and advanced image processing and accurate camera pointing devices, and is expensive as a whole.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a simpler continuous unloader relative position measurement having means for accurately measuring the relative position between the vertical arm of the continuous unloader and the hatch opening of the hold. It is an object of the present invention to provide a continuous unloader relative position measuring device which recognizes an obstacle at an edge of a hatch and issues an alarm.

[0009]

In order to solve the above-mentioned problems, a relative position measuring device for a continuous unloader according to the present invention has two wide-angle scanning distance meters attached to the end of an unloader boom so that the scanning directions cross each other. Attach the inclinometer, arrange the scanning line of the rangefinder so as to include the edge of the hold hatch, and measure the distance to the point on the target surface that intersects the scanning line and the scanning angle when measuring that point and the rangefinder. The three-dimensional coordinates of these points are obtained from the inclination angle, and the three-dimensional coordinates of the center position of the hatch opening and the surface direction of the surface including the hatch opening are calculated from the three-dimensional coordinates.

When the measuring device of the present invention is set on the hatch opening of the hold, a load is applied to the continuous unloader and the torsion is generated. Even if there is a deviation from the bottom, the relative position of the hatch opening is accurately measured by correctly correcting the measurement result of detecting the edge part of the hold hatch for each side using the output of the inclinometer be able to. Therefore, by transmitting the position of the hatch opening obtained by the present measuring device to the control system, the position of the unloader can be controlled so that the vertical arm or the scraping device does not collide with the hatch edge or the inner wall of the hatch.

The two wide-angle scanning rangefinders may each have a built-in inclinometer. Since the two wide-angle scanning rangefinders are both mounted on the upper end of the vertical arm through a single-axis head, the measurement output of the rangefinder can be corrected if the tilt of the vertical arm can be measured. It is difficult to make an installation adjustment to accurately grasp the positional relationship between the individual rangefinders, and it is difficult to correct when the positions of the two are out of order. Therefore, by attaching an inclinometer to each rangefinder and directly measuring the tilt of the uniaxial head itself on which the rangefinder is mounted, adjustment between the wide-angle scanning rangefinder and the inclinometer can be performed. There is an advantage that the adjustment can be performed in advance, the adjustment when attaching to the vertical arm is easy, and the correction of the measurement result is also easy.

[0012] Further, there is provided an image acquiring means at the tip of the unloader boom, an image processing means for processing an image acquired by the image acquiring means to extract an edge of the hatch, and a monitor for drawing the extracted edge. A situation where the relative position of the mouth is measured may be monitored. When the edge part is extracted from the image of the part measured by the range finder and displayed on the monitor device, the observer visually observes the state of the edge part and confirms the reliability of the measurement output of the range finder. Can be. If there is an obstacle to the measurement, such as the body of a field worker on the measurement part, remove the obstacle or change the measurement position, and then perform the measurement again. Is obtained.

The frame indicating the end position of the hatch opening obtained from the distance meter may be displayed on the monitor device in an overlapping manner. By observing the hatch opening position independently obtained by the two means on the same monitor screen, the reliability of the measurement is greatly improved. When the difference between the two is large, an alarm signal may be generated to alert the observer.

In order to solve the above-mentioned problem, a second continuous unloader relative position measuring device according to the present invention has two wide-angle scanning rangefinders attached to the end of the unloader boom so that the scanning directions cross each other, and the image acquisition means is provided. Attach and arrange so that the scanning line of the distance meter includes the edge of the hold hatch, and determine these points from the distance from the attachment position obtained by the distance meter to the point on the surface that intersects the scanning line and the scanning angle at the time of measurement. Are calculated from the three-dimensional coordinates, the three-dimensional coordinates of the center position of the hatch opening and the plane direction of the plane including the hatch opening are calculated from the three-dimensional coordinates, and the image obtained by the image obtaining means is processed to determine the edge of the hatch. An image processing means for extracting and a monitor device for drawing the extracted edge portion are provided, and the end portion of the hatch opening obtained from the distance meter is displayed on the monitor device in a superimposed manner.

Further, an alarm signal may be output when the edge portion extracted by the image processing means does not match the edge portion of the hatch obtained from the distance meter. Because it can be judged mechanically, regardless of the quality of the guards,
It is easy to ensure the reliability of the measurement. Note that these relative position measuring devices may be mounted on a head mounted on the tip of the unloader boom, which has a substantially vertical axis and rotates in conjunction with the rotation of the unloader boom. preferable. If the direction of the pan head is linked to the rotation of the unloader boom, the direction of the scanning surface of the scanning rangefinder will maintain the initially set direction even when the direction of the vertical arm changes due to momentary control. For example, if the direction of the scanning surface is determined to be perpendicular to the side of the hatch opening, the minimum distance will be measured while maintaining the perpendicular to the end.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on embodiments with reference to the drawings. FIG. 1 is a perspective view showing a use state of the continuous unloader relative position measuring device of the present invention. A continuous unloader (CSU) 1 runs on a quay rail 2 and stops adjacent to a berthing ship 3, extends an unloader boom 4 onto the ship's hold 5, and mounts a vertical arm 6 provided at the tip. It is inserted into the hatch opening 7 of the hold, and the internal bulk goods are collected by the scraping device 8 attached to the lower end.
It is transported to a stockyard on land by a vertical arm 6 and a conveyor in the unloader boom 4. Two sensor heads are attached to the tip of the unloader boom 4 and the upper end of the vertical arm 6. Each of the sensor heads incorporates a wide-angle scanning distance meter, and the two sensor heads 9 are arranged so that the scanning surfaces of the wide-angle scanning distance meter are perpendicular to each other vertically downward. An electric room 10 in which a control panel and the like are installed is mounted on the main body of the continuous unloader straddling the rail 2.

FIG. 2 is an enlarged perspective view showing a sensor head portion of the continuous unloader relative position measuring device of the present invention. The sensor head 9 includes a uniaxial head 11, a wide-angle scanning rangefinder or scanning laser range finder (LRF) 12 fixed thereto, and CCD cameras 13 provided on both sides of the finder 12. And an inclinometer 14 fixed to the camera platform. The scan-type laser range finder 12 scans a laser beam within a predetermined angle range, and measures a distance to the object based on a phase of the laser beam reflected on the object and returned. The position of the object to be measured can be known at, for example, 0.1 degree intervals using polar coordinates having the origin of the laser radiation position. Therefore, by developing the measurement data obtained from the scanning laser range finder 12 into a two-dimensional space, the profile of the object can be known.

The single-axis head 11 is a continuous unloader (CSU)
The shaft of the rotating shaft 15 is attached at a tip of the head 1 so that the shaft of the rotating shaft 15 is oriented vertically, and rotates in conjunction with the turning of the unloader boom 4 of the continuous unloader (CSU) 1 to rotate and rotate the head. It is controlled to keep the orientation in the initial direction. The CCD camera 13 is attached to the one-axis head 11 via an elevation angle control head 16 that controls the line of sight of the camera. The CCD camera 13 aims at the edge position of the hatch by an operation of the operator, and acquires an image in which the edge portion of the hatch captured by the scanning laser range finder 12 is included in the field of view.

The measuring device extracts an edge from the image obtained by the CCD camera 13 and checks the output data of the scanning type distance meter to specify an edge position to be measured. By superimposing and displaying the distance data graph obtained from the scanning type distance meter on the image displayed on the monitor device, it becomes possible to initialize the position of the edge of the tracking target and monitor the edge being tracked. In addition, based on the characteristics of the extracted edge image, the position of the edge in the image is updated while automatically tracking the edge by automatically manipulating the CCD camera by pattern matching, and matching with the data of the scanning distance meter does not match. At times, an alarm can be issued to alert the operator.

In addition, a foreign object on the edge is detected by using an image processing device while automatically tracking the CCD camera, and an alarm is issued before the range finder performs erroneous measurement with the foreign object, thereby removing the foreign object, changing the measurement position, and so on. Measures such as ignoring measurement results can be encouraged. The inclinometer 14 is a two-axis inclinometer for measuring the inclination of the one-axis head 11, and the measurement result indicates the inclination of the scan-type laser range finder 12.

FIG. 3 is a perspective view showing a sensor head according to another embodiment. The CCD camera 1 does not use an elevation control pan head.
3 is directly fixed to the one-axis head 11. If the field of view of the CCD camera is large to some extent, the state of the hatch opening can be sufficiently observed without aiming the camera at the edge of the hatch accurately. Depending on the required resolution, it may be sufficient to fix only one CCD camera.

FIG. 4 is a plan view showing the relationship between the sensor head 9 and the hatch opening. When the vertical arm 6 at the tip of the unloader boom 4 is inserted into the hatch opening 7, the scanning surfaces of the laser range finder 12 mounted on the two sensor heads 9 are adjusted so as to vertically intersect the edges of the hatch 7. Is done. Thus, by measuring the distance and direction to the four sides of the hatch edge, the center position of the hatch opening and the direction of the hatch opening surface can be grasped, and the relative position between the vertical arm 6 and the hatch opening is measured. When the relative position is changed in accordance with the progress of the unloading operation or when the unloading boom 4 is moved to a desired relative position based on the measurement result, the position is adjusted. At this time, the two sensor heads 9 attached to the upper end of the vertical arm 6 hold the direction of the scanning surface in the initial state orthogonal to the hatch edge in conjunction with the turning of the unloader boom 4 to measure the relative position. Ensure accuracy.

FIG. 5 is a block diagram of a continuous unloader control device using a sensor head, and FIG. 6 is a flowchart showing a measuring operation of the present embodiment. FIG. 7 shows distance measurement data as polar coordinates, and FIG. 8 shows distance measurement data converted into rectangular coordinates. The sensor head 9 includes a scanning LRF 12, a two-axis inclinometer 14 for measuring the inclination of the scanning LRF 12, a CCD camera 13, and a one-axis head 11 that enables rotation of the sensor head. Although only one sensor head is shown in the figure, at least another sensor head having the same configuration is provided. The part that exchanges signals with the sensor head 9 to control the continuous unloader is installed in an electric room, and includes a camera control device 17, an image processing device 18, a display device 19, a data processing device 20, a pan head control device 21, and a manual operation box. 22, and a CSU control device 23.

Based on the continuous unloader rotation axis control signal of the CSU controller 23, the pan head controller 21
The uniaxial head 11 is controlled such that the laser scanning surface of F12 is always parallel or perpendicular to the edge of the hatch opening (S
1). The one-axis pan head 11 can be controlled by a manual operation of an operator via a manual operation box 22. The operator adjusts the target area of the scanning distance meter by looking at the image acquired by the CCD camera.

The CCD camera 13 obtains an image by adjusting the image by the camera controller 17 (S2). The video output is transmitted to the image processing device 18 via the camera control device 17. The image processing device 18 extracts an edge portion from the image by using a feature such as a region where the edge portion in the image has almost the same brightness and is thin and linearly continuous (S3). The position of the edge extracted by the image processing device 18 is displayed on the display device 19 together with the video.

The scanning LRF 12 and the two-axis inclinometer 14
Is input to the data processing device 20 and is used to detect the position of the hatch edge. The scanning rangefinder 12 emits a measuring laser and knows the distance to the object from the phase difference of the laser reflected back to the object, but at this time, the measuring laser is scanned radially in a plane. The measurement is performed, and the scanning angle and the distance to the object are output as a measurement result (S4).

However, when the load is changed during unloading and the vertical arm is twisted or the unloader boom is bent, the sensor head mounting surface at the end of the unloader boom deviates from the horizontal plane, and the attitude of the scanning LRF 12 changes.
The measurement output value of the scanning LRF 12 in such a state includes an error corresponding to the inclination of the scanning surface of the measurement laser beam. Therefore, the inclinometer 14 detects the inclination of the LRF 12 in the biaxial directions (S5), and uses the measurement result of the inclinometer 14 to take into account the inclination of the LRF for each of the component parallel to and perpendicular to the scanning plane. Then, the output of the rangefinder is corrected and converted into polar coordinate values projected on the vertical plane (S6).

FIG. 7 is a diagram showing the concept of correcting the deviation of the center line in the scanning plane of the measuring laser beam, and FIG. 8 is a diagram showing the concept of correcting the inclination of the scanning surface. Scan type L
The scanning angle θi in the measurement result (Ri, θi) that the RF 12 measures and outputs a target point such as the hatch edge 24 is
It is determined based on the center line 25 of the laser scanning range. Since the inclination between the center line 25 and the vertical line 26 represented by the one-dot chain line is detected by the inclinometer 14, the deviation is compensated for as shown in FIG. Can be requested.

When the laser scanning surface is inclined as shown in FIG. 8, the distance Ri to the hatch edge measured by the scanning LRF 12 is longer than the actual distance, that is, the distance Ri 'in the vertical plane. The actual distance Ri ′ can be obtained by multiplying the distance measurement value by the cosine value of the scanning plane inclination φ obtained by the two-axis inclinometer. In this manner, a correct polar coordinate value (Ri ′, θi ′) of a target point such as the hatch edge 24 can be obtained by compensating for the measurement error based on the fluctuation of the unloading load.

Further, as shown in FIG. 9, by using the result obtained by compensating for the error, the position of the reflector 27 within the scanning range is determined for each fixed angle with the center 28 of the radiation as the origin. Obtain distance measurement data represented as discrete polar coordinate values 29. However, it is difficult to directly know the position of the hatch edge represented by the dotted line 30 from this data. As shown in FIG. 10, the data processing device 20 converts the output of the distance meter from polar coordinates to rectangular coordinates, connects the measurement points with straight lines, and
The hatch edge 24 is specified by plotting while leaving the maximum value of the Y coordinate for each coordinate, and finding a point where the Y coordinate value jumps on the graph (S7). In this way, hatch edges can be detected extremely easily.

The contour position of the hatch edge obtained by the data processing device 20 is displayed so as to be superimposed on the edge portion extracted from the output image of the CCD camera 13 by the image processing device 18 so that the operator can easily make a comparison. Can be. Further, the position of the edge based on the scanning LRF 12 is compared with the position of the edge based on the CCD camera 13 (S8). If a difference between the two is larger than the allowable value, a warning is issued to warn the operator (S9).

When a foreign substance is present near the edge of the hatch opening, an alarm may be issued by automatically detecting the foreign matter. Further, the head control device 21 may be directly controlled to avoid an obstacle. The change in the attitude of the one-axis head 11 is transmitted to the data processing device 20 via the head controller 21 and is used to correct the measurement result. FIG. 11 is a diagram showing a state around the hatch opening photographed by the CCD camera, and FIG. 12 is a diagram showing a rangefinder output state when there is a foreign matter near the hatch. When the foreign matter 31 exists near the hatch opening edge 24, the operator can detect the foreign matter 31 with the monitor device 19 and take appropriate measures.

However, at this time, when the trajectory of the measuring laser beam shown by the dotted line in the figure passes over the foreign matter, the output of the scanning type distance meter 12 becomes as shown by the dotted circle in FIG. Since the measurement outputs near the hatch opening edges on both sides lose symmetry, the presence of foreign matter can be determined. If the hatch edge model registered in advance does not match the measured cross-sectional data, it may be determined that some foreign matter exists. Alternatively, an image difference may be observed for an image signal near a hatch edge in an image, and when there is a difference from a previously acquired signal, the presence of a foreign substance may be estimated. If the two hatch positions obtained independently match and there is no problem, the hatch position is displayed on the monitor device 19 (S10).

When the continuous unloader is automatically operated, the hatch edge position information detected by the data processor 20 is transmitted to the CSU controller 23 and used for vertical arm control. In the above embodiment, CC is used as an image acquisition unit.
Although the D camera is used, it goes without saying that a camera having another principle can also be used.

[0035]

As described above, the relative position measuring device for a continuous unloader according to the present invention does not deteriorate the measurement accuracy due to a change in the scraping load. Further, even when the shape of hatch combing is special and an edge cannot be specified from the cross-sectional shape acquired by the scanning distance meter, it is possible to judge and teach from the image acquired by the CCD camera, and the operability is good. Further, since the image is acquired and displayed together with the distance measurement, the tracking state and the measurement state can be monitored by the image. Furthermore, since the edge detection result by the image processing and the edge tracking detection result by the scanning distance meter can be comprehensively evaluated, robust measurement can be performed. In addition, an alarm can be automatically issued when the two data do not match, thereby increasing the safety of the continuous unloader operation. When an obstacle is present on the edge, the obstacle is detected via the image and an alarm is issued, so that accurate measurement is possible and the safety of the worker can be secured.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a use state of a continuous unloader relative position measuring device of the present invention.

FIG. 2 is an enlarged perspective view showing a part of a sensor head used in the continuous unloader relative position measuring device according to one embodiment of the present invention.

FIG. 3 is an enlarged perspective view showing a part of a sensor head according to another embodiment.

FIG. 4 is a plan view showing a relationship between a sensor head and a hatch opening in the present embodiment.

FIG. 5 is a block diagram of a continuous unloader control device of the present embodiment.

FIG. 6 is a flowchart illustrating a measurement operation of the continuous unloader control device of the present embodiment.

FIG. 7 is a diagram illustrating a situation in which the inclination of the rangefinder in the scanning plane is corrected in the embodiment.

FIG. 8 is a diagram showing a situation in which a tilt in a direction perpendicular to a scanning surface of the rangefinder is corrected in the embodiment.

FIG. 9 is a cross-sectional view showing measurement data of the distance meter in the present embodiment.

FIG. 10 is a cross-sectional view showing a hatch edge detection state in the present embodiment.

FIG. 11 is a plan view illustrating a field of view of the imaging apparatus according to the present embodiment.

FIG. 12 is a cross-sectional view showing measurement data when an obstacle is present at a hatch edge in the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous unloader (CSU) 2 Rail 3 Ship 4 Unloader boom 5 Hold 6 Vertical arm 7 Hatch opening 8 Scraper 9 Sensor head 10 Electric room 11 1 axis head 12 Scan type laser range finder 13 CCD camera 14 Inclinometer 15 rotation Axis 16 Elevation control pan head 17 Camera control unit 18 Image processing unit 19 Display unit 20 Data processing unit 21 Pan head control unit 22 Manual operation box 23 Continuous unloader (CSU) control unit 24 Hatch edge 25 Center line of laser scanning range 26 Vertical Line 27 Reflecting object 28 Laser emission center 29 Discrete polar coordinate measurement value 30 Hatch edge position 31 Foreign matter

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[Procedure amendment]

[Submission date] December 3, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 5

[Correction method] Change

[Correction contents]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Masayuki Enomoto, 118 Futatsuka, Noda-shi, Chiba Kawasaki Heavy Industries Noda Plant (72) Inventor Yugo Nakagami 1-1-3, Higashi-Kawasaki-cho, Chuo-ku, Kobe, Hyogo Prefecture Kawasaki Heavy Industries, Ltd.Kobe Head Office

Claims (7)

[Claims] 1. Two wide-angle scanning rangefinders are attached to the end of an unloader boom so that the scanning directions intersect, and an inclinometer is mounted. The scanning line of the rangefinder is arranged so as to include the edge of the hold hatch. The three-dimensional coordinates of these points are obtained from the distance from the mounting position obtained by the distance meter to a point on the surface intersecting the scanning line, the scanning angle at the time of measurement, and the inclination angle of the distance meter obtained by the inclinometer. A relative position measuring device for a continuous unloader, which calculates three-dimensional coordinates of a center position of a hatch opening and a surface direction of a surface including the hatch opening from the three-dimensional coordinates. 2. The relative position measuring device for a continuous unloader according to claim 1, wherein said inclinometer is built in each wide-angle scanning distance meter. 3. An unloading boom has an image obtaining means at the tip thereof, an image processing means for processing an image obtained by the image obtaining means to extract an edge portion of the hatch, and a monitor device for drawing the extracted edge portion. 3. The relative position measuring device for a continuous unloader according to claim 1, wherein a condition of measuring the hatch opening can be monitored. 4. The relative position measuring device for a continuous unloader according to claim 3, wherein an end of the hatch opening obtained from the distance meter is displayed on the monitor device in an overlapping manner. 5. Attachment of two wide-angle scanning rangefinders to the tip of the unloader boom so that the scanning directions intersect with each other, and image acquisition means, and the scanning lines of the rangefinders are arranged so as to include the edge of the hold hatch. Then, the three-dimensional coordinates of these points are obtained from the distance from the mounting position obtained by the distance meter to a point on the surface intersecting the scanning line and the scanning angle at the time of measurement, and the center position of the hatch opening is obtained from the three-dimensional coordinates. Image processing means for calculating the three-dimensional coordinates and the plane direction of the plane including the hatch opening, further processing the image obtained by the image obtaining means to extract the edge part of the hatch, and a monitor device for drawing the extracted edge part A relative position measuring device for a continuous unloader, wherein an end of a hatch opening obtained from the distance meter is displayed on the monitor device in an overlapping manner. 6. The unloader according to claim 3, wherein an alarm signal is output when the edge portion extracted by the image processing means does not match the edge portion of the hatch obtained from the range finder. Relative position measuring device. 7. A single-axis pan head having a substantially vertical axis at the tip of the unloader boom and rotating in conjunction with rotation of the unloader boom, wherein the wide-angle scanning rangefinder is mounted on the single-axis pan head. The relative position measuring device for a continuous unloader according to any one of claims 1 to 6, wherein: