Angle detection method and angle detection system

Abstract

To detect the angle of an article put in place on a horizontal surface.SOLUTION: An angle detection method uses a detector 140 acquiring the distance to an article 200 as point data to detect an angle with respect to a prescribed vertical face of a detection face part 201 including a face of the almost rectangular parallelepiped article 200 facing the detector 140, and includes: a point group acquisition step of acquiring point data on a plurality of portions of the detection face part 201 as point groups; a trimming step of extracting a point group within a prescribed height range from the point groups acquired in the point group acquisition step; and an angle detection step of detecting the angle of the detection face part 201 on the basis of the point group extracted in the trimming step.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an angle detection method for detecting the angle of a substantially rectangular parallelepiped-shaped article placed on a horizontal plane, and an angle detection system.

Background Art

[0002] For example, Patent Document 1 describes a technique for acquiring a point cloud indicating the three-dimensional shape of an article and determining the position and orientation of the object based on the point cloud.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional technology, there is a drawback that noise based on the surface shape of the article affects and the angle of the article cannot be accurately detected.

[0005] The present invention has been made in view of the above problems, and provides an angle detection method for accurately detecting the angle of an article placed on a horizontal plane, and an angle detection system.

Means for Solving the Problems

[0006] In order to achieve the above object, an angle detection method according to one aspect of the present invention is an angle detection method for detecting an angle of a detection surface portion including a surface facing a detector of a substantially rectangular parallelepiped-shaped article with respect to a predetermined vertical plane, using a detector that acquires the distance to the article placed on a horizontal plane as a plurality of three-dimensional point data, the method including: a point group acquisition step of acquiring point data at a plurality of locations on the detection surface portion as a point group; a trimming step of extracting a point group within a predetermined height range from the point group acquired in the point group acquisition step; and an angle detection step of detecting the angle of the detection surface portion based on the point group extracted in the trimming step.

[0007] In order to achieve the above object, an angle detection system according to another aspect of the present invention includes: a detector that acquires the distance to an article as a plurality of three-dimensional point data; a rack that stores a plurality of substantially rectangular parallelepiped-shaped articles placed on a horizontal plane; and an angle detection device that detects an angle of a detection surface portion including a surface facing the detector of the article with respect to a predetermined vertical plane. The angle detection device includes: a point group acquisition unit that acquires point data at a plurality of locations on the detection surface portion as a point group; a trimming unit that extracts a point group within a predetermined height range from the point group acquired by the point group acquisition unit; and an angle detection unit that detects the angle of the detection surface portion based on the point group extracted by the trimming unit.

Advantages of the Invention

[0008] According to the present invention, it is possible to suppress the influence of noise caused by the shape of the article and detect the angle of the article with high accuracy.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of an angle detection method and an angle detection system according to the present invention will be described with reference to the drawings. Note that the following embodiments are examples for explaining the present invention and are not intended to limit the present invention. For example, the shapes, structures, materials, components, relative positional relationships, connection states, numerical values, mathematical formulas, the content of each stage in the method, the order of each stage, etc. shown in the following embodiments are examples, and may include content not described below. Also, geometric expressions such as parallel and orthogonal may be used, but these expressions do not indicate mathematical precision and include substantially allowable errors, deviations, etc. Also, expressions such as simultaneous and identical also include a substantially allowable range.

[0011] Also, the drawings are schematic diagrams that have been appropriately emphasized, omitted, or adjusted in ratio for explaining the present invention, and are different from the actual shapes, positional relationships, and ratios.

[0012] Also, in the following, a plurality of inventions may be comprehensively described as one embodiment. Also, a part of the content described below is explained as an arbitrary component related to the present invention.

[0013] FIG. 1 is a perspective view showing an angle detection system. FIG. 2 is a perspective view showing the vicinity of the transfer device of the angle detection system. The angle detection system 100 is a system that detects an angle indicating the posture of an article 200 placed on a rack 110 in a horizontal plane, and includes a detector 140 and an angle detection device 150 (not shown in FIGS. 1 and 2). In the case of the present embodiment, the angle detection system 100 is a device that can automatically convey the loaded article 200, automatically transfer the article 200 to the storage position of the article 200, and convey the article 200 automatically transferred from the storage position, and is incorporated into a so-called automated warehouse including a conveyance device 120 and a transfer device 130.

[0014] The article 200 to be transferred by the angle detection system 100 is not particularly limited as long as it is substantially rectangular parallelepiped. The substantially rectangular parallelepiped shape includes a shape formed by six flat rectangular surfaces, and also includes a shape having ribs, flange-like protrusions, depressions or holes such as handles. Specifically, examples of the article 200 include articles having a flat surface property without an uneven shape on the surface, such as cardboard boxes, paper boxes, and wooden boxes, and articles having a surface property with an uneven shape on the surface, such as containers, trays, and foldable containers.

[0015] The rack 110 is a facility for storing a plurality of substantially rectangular parallelepiped articles 200 arranged side by side so that the detection surface portion 201 of the article 200 facing the area where the conveyance device 120 moves is along a predetermined arrangement direction (X-axis direction in the figure). In the case of the present embodiment, the rack 110 includes a shelf board 111 on which the article 200 is placed in a horizontal plane and a support column 112 that supports the shelf board 111. The shelf board 111 is flat, and the position for storing the article 200 is not particularly limited. The rack 110 may store only articles 200 of the same shape, or may store articles 200 of a plurality of types of shapes in a mixed state. Although the rack 110 is shown on one side when viewed in the moving direction of the conveyance device 120 in the figure, the rack 110 may be arranged on both sides.

[0016] The conveying device 120 is a device that holds and conveys the article 200, and is not particularly limited as long as the detector 140 can be attached thereto. Examples of the conveying device 120 include an untracked automated guided vehicle that holds the article 200 and autonomously travels on the floor surface, and a tracked carriage that holds the article 200 and travels along a predetermined track such as a rail. In the case of the present embodiment, the conveying device 120 is a so-called stacker crane including a rail 121, a carriage 122 that travels on the rail 121, a mast 123 that is attached to the carriage 122 in an upright state and moves together with the carriage 122, and a lifting platform 124 that can hold the article 200 and moves up and down along the mast 123.

[0017] The transfer device 130 is a device that transfers the article 200 between the rack 110 and the lifting platform 124 of the conveying device 120, and transfers the article 200 by moving it in the depth direction (Y-axis direction in the figure) orthogonal to the arrangement direction of the article 200 (X-axis direction in the figure) in the horizontal plane. The type of the transfer device 130 is not particularly limited, and examples thereof include a device that sandwiches both opposing side surfaces of the article 200 for transfer, a device that hooks claws on the back surface, the front surface, etc. of the article 200 and transfers the article 200 while sliding it, and a device that scoops up the article 200 for transfer.

[0018] In the case of the present embodiment, the transfer device 130 is attached to the lifting platform 124 of the conveying device 120 and is configured to be able to transfer the article 200 between the rack 110 and the lifting platform 124. When the racks 110 are arranged on both sides of the conveying device 120, the transfer device 130 is configured to be able to transfer the article 200 to any of the racks 110 on either side.

[0019] The detector 140 is a sensor that acquires, as a plurality of three-dimensional point data, the distances between a plurality of locations on the detection surface portion 201 including the surface of the article 200 facing the detector 140 and the detector 140. The type of the detector 140 is not particularly limited, and examples thereof include three-dimensional ranging sensors such as a LiDAR (Laser Imaging Detection and Ranging) sensor and a TOF (Time of Flight) camera.

[0020] The location where the detector 140 is attached is not particularly limited as long as it is a part of the transfer device 120. For example, if it is attached near the location where the article 200 is transferred, it is preferable because the relative positional relationship between the transfer position and the article 200 can be accurately detected. In the case of the present embodiment, the detector 140 is attached to the lift 124 of the transfer device 120. The number of detectors 140 provided in the angle detection system 100 is not particularly limited, but in the case of the present embodiment, two detectors 140 arranged in the arrangement direction of the articles 200 are provided. The distance between the two detectors 140 is set so as to be able to acquire point data with a predetermined density or more, and to cover the assumed longest width of the article 200 stored in the rack 110 in the arrangement direction and the gaps with the adjacent articles 200 set on both sides thereof at once. In the case of the present embodiment, the detectors 140 are attached to both side portions in the width direction (X-axis direction in the figure) of the lift 124. That is, the detectors 140 are respectively arranged on both sides of the area through which the article 200 transferred by the transfer device 130 passes. Thereby, it becomes possible to accurately detect the positional relationship between the area where the article 200 is transferred and the article 200 stored in the nearby rack 110.

[0021] FIG. 3 is a block diagram showing the functional configuration of the angle detection system. The angle detection device 150 is a device that detects the angle of the detection surface portion 201 including the surface of the article 200 facing the detector 140 with respect to a predetermined vertical plane, and includes, as a processing unit realized by causing a processor to execute a program, a point cloud acquisition unit 151, a trimming unit 171, and an angle detection unit 172.

[0022] The point cloud acquisition unit 151 acquires, as a point cloud, point data at a plurality of locations on the detection surface portion 201 of the article 200 from the detector 140. The data structure of the point data is not particularly limited, but includes, for example, three-dimensional data indicating the relative positional relationship with respect to the transfer device 130. In the case of the present embodiment, it includes data in an orthogonal coordinate system having data in the arrangement direction (X-axis direction in the figure) of the article 200 on the shelf board 111 of the rack 110, the vertical direction (Z-axis direction in the figure) orthogonal to the arrangement direction on the detection surface portion 201, and the depth direction (Y-axis direction in the figure) orthogonal to both the arrangement direction and the vertical direction.

[0023] In the case of the present embodiment, the angle detection system 100 includes a plurality of detectors 140 arranged in the arrangement direction, and the point cloud acquisition unit 151 acquires a point cloud from each of the detectors 140. Note that the point cloud acquisition unit 151 may statistically process the point data included in the overlapping regions of the point clouds acquired from the plurality of detectors 140 and synthesize the point clouds of the plurality of detectors 140 into a single image. Thereby, it becomes possible to process the point data regarding the detection surface portions 201 of the plurality of articles 200 in the arrangement direction as a single image. Note that instead of synthesizing the point clouds of the plurality of detectors 140 into a single image, the processing result may be obtained using the images corresponding to the point clouds of each detector 140 and the results may be synthesized.

[0024] FIG. 4 is a diagram showing the trimming result. The trimming unit 171 executes a trimming process of extracting point groups within a predetermined height range with respect to the plane on which the article 200 is placed from the point groups acquired by the point group acquisition unit 151. Specifically, the trimming unit 171 extracts point data included within a predetermined height range from the point groups acquired from the point group acquisition unit 151. The predetermined height range is not particularly limited, but for example, a strip-shaped region that includes the central position of the minimum height (vertical length) of the article 200 stored in the rack 110 and has a predetermined height can be exemplified. Specifically, point data having a value in the vertical direction (Z-axis direction in the figure) less than the first threshold value is excluded, and point data having a value in the vertical direction (Z-axis direction in the figure) greater than the second threshold value (> the first threshold value) is excluded. That is, point data within the range of the first threshold value or more and the second threshold value or less is extracted. Since the detection of the no-article section is performed using data within a predetermined height range in the trimming process, noise due to the reflection by the shelf board 111 of the rack 110 and the like, and noise due to ribs, flanges, holes, etc. provided on the surface of the article 200 can be suppressed, and accurate point data regarding the angle of the detection surface portion 201 can be provided. Also, the data amount of the point groups can be suppressed to facilitate the processing of the next step.

[0025] The angle detection unit 172 detects the angle of the detection surface portion 201 based on the point groups extracted by the trimming unit 171. FIG. 5 is a flowchart showing the processing flow of the angle detection unit. FIG. 6 is a diagram showing the processing states at each stage of the steps of the angle detection unit.

[0026] The angle detection unit 172 projects the point groups extracted in the trimming process (S101) by the trimming unit 171 in the vertical direction to generate a two-dimensional projection image shown in FIG. 6(a) (S102, projection process). Specifically, a two-dimensional projection image is generated by excluding the data in the vertical direction (Z-axis direction in the figure) from each point data.

[0027] Next, the angle detection unit 172 performs a morphological process on the projected image, complements the space between the point data that existed as rough points, and changes the data so that the portion corresponding to the detection of the article 200 as shown in FIG. 6(b) becomes a single mass (the white portion in the image of FIG. 6) (S103, morphological process). In the case of the present embodiment, the angle detection unit 172 performs a closing process that repeats dilation and contraction as the morphological process.

[0028] Next, the angle detection unit 172 removes noise from the point data subjected to the morphological process (S104, noise removal process). In the case of the present embodiment, the angle detection unit 172 performs a labeling process to mutually distinguish the single mass of point data as shown by the white arrows 0-9 in FIG. 6(c). Then, the single mass of point data having a length equal to or less than a predetermined length threshold is removed as noise. As a result, an image as shown in FIG. 6(d) is obtained.

[0029] Next, as shown by the vertical lines at the tips of the arrows shown in FIG. 6(d), the angle detection unit 172 removes the respective ends of the labeled single mass of point data (S105, cutting process).

[0030] Next, as shown in FIG. 6(e), the angle detection unit 172 performs a linear fitting on each of the single masses of point data whose ends have been cut (S106, fitting process). As described above, it is possible to exclude the arrangement of point data that greatly changes and perform a linear fitting on a stable single mass of point data, and it becomes possible to fit a straight line corresponding to the angle (inclination) of the detection surface portion 201 of the actual article 200.

[0031] Finally, as shown in FIG. 6(f), for the straight lines respectively determined by the fitting process, the respective angles (θ1, θ2, θ3, θ4) with respect to a predetermined vertical plane are detected (S107, angle detection process). The predetermined vertical plane is not particularly limited. For example, a plane parallel to the frontage of the portion where the article 200 is stored in the rack 110 may be set as the predetermined vertical plane. Also, a plane parallel to the imaging surface of the detector 140 may be set as the predetermined vertical plane.

[0032] According to the angle detection system 100 according to the above embodiment, based on the point cloud detected by the detector 140, a point cloud within a predetermined height range from the horizontal plane on which the article 200 is placed is extracted, and based on the extracted point cloud, the angle with respect to a predetermined vertical plane of the detection surface portion 201 is detected, whereby noise caused by the uneven shape existing on the detection surface portion 201 can be suppressed. Therefore, the angle of the surface of the article can be detected with high accuracy.

[0033] Further, by performing linear fitting on the projection image obtained by converting the three-dimensional point data acquired from the detector 140 into two-dimensional data projected in the vertical direction, it becomes possible to accurately detect the angle indicating the posture of the article 200 in the horizontal plane.

[0034] Further, by performing morphological processing, noise processing, etc. on the projection image, the range where the mass of the point data corresponding to the article 200 in the projection image exists can be appropriately imaged, and linear fitting can be performed with high accuracy.

[0035] Note that the present invention is not limited to the above embodiment. For example, another embodiment realized by arbitrarily combining the constituent elements described in this specification and excluding some of the constituent elements may also be an embodiment of the present invention. Further, modification examples obtained by applying various modifications conceivable by those skilled in the art without departing from the gist of the present invention, that is, the meaning indicated by the language described in the claims with respect to the above embodiment are also included in the present invention.

[0036] For example, in the angle detection step, although linear fitting is performed on a mass of point data, an L-shaped template may be fitted to detect the angle of the detection surface portion. Specifically, in the trimming step (S101) of the above embodiment, trimming processing is performed so as to leave the point group in the depth direction, and after processing the point group up to the noise removal step (S104), in the fitting step (S106), as shown in FIG. 7, the corner of the mass of point data (the portion surrounded by the circle in FIG. 7) appearing in the projection image is aligned with the corner of the L-shaped template, and as shown in FIG. 8, the L-shaped template (the black line in FIG. 8) is relatively rotated around the aligned corner at a predetermined angle (for example, 1°) increments to fit with the mass of point data (the white in FIG. 8) respectively, and the angle of the L-shaped template with the highest matching score may be detected as the angle of the detection surface portion 201.

[0037] In addition, although the case where a plurality of detectors 140 are provided is exemplified, the detector 140 may be singular. The angular coverage of one detector 140 may be such that it can detect at once a range obtained by adding the widths of the non-goods sections existing on both sides to the width of the good 200 located at the center of three consecutive goods 200 on the shelf board 111 of the rack 110.

[0038] In addition, although the conveying device 120 that freely conveys the good 200 in the vertical plane is exemplified, the conveying device 120 may be a rail-guided or non-rail-guided conveyance carriage that conveys the good 200 in the horizontal plane.

[0039] In addition, although the rack 110 that can two-dimensionally store the good 200 in the horizontal direction and the vertical direction is exemplified, the rack 110 may store the good 200 one-dimensionally along the traveling direction of the conveyance carriage.

Industrial Applicability

[0040] The present invention is applicable to an automated warehouse that conveys goods by a conveying device and transfers goods between a rack and the conveying device, a logistics base, factory facilities, a robot that stacks boxes, containers, etc.

Description of Symbols

[0041] 100 Angle detection system 110 Rack 111 Shelf board 112 Support pillar 120 Conveyor 121 Rail 122 Cart 123 Mast 124 Lift table 130 Transfer device 140 Detector 151 Point cloud acquisition unit 170 Angle detection device 171 Trimming unit 172 Angle detection unit 200 Article 201 Detection surface

Claims

1. An angle detection method that uses a detector to acquire the distance to an object placed on a horizontal plane as three-dimensional multiple point data, and detects the angle of a detection surface portion including a surface facing the detector of a substantially rectangular parallelepiped object with respect to a predetermined vertical plane, comprising: a point cloud acquisition step of acquiring point data at a plurality of locations on the detection surface portion as a point cloud; a trimming step of extracting a point cloud within a predetermined height range from the point cloud acquired in the point cloud acquisition step; an angle detection step of projecting the point cloud extracted in the trimming step in the vertical direction to generate a projection image, and detecting the inclination of a straight line obtained by fitting to the point data appearing in the projection image as the angle of the detection surface portion; An angle detection method including the above steps.

2. In the angle detection step, perform straight line fitting after removing noise from the projection image. The angle detection method according to Claim 1. The angle detection method according to Claim 1.

3. In the angle detection step, perform straight line fitting after removing the end portions of a mass of point data appearing in the projection image. The angle detection method according to Claim 1 or 2. The angle detection method according to Claim 1 or 2.

4. In the angle detection step, the fitting is fitting by an L-shaped template, and the inclination of the straight line portion of the fitted L-shaped template is detected as the angle of the detection surface portion. The angle detection method according to Claim 1. The angle detection method according to Claim 1.

5. A detector that acquires the distance to an object as three-dimensional multiple point data; a rack for placing and storing a plurality of substantially rectangular parallelepiped objects on a horizontal plane; an angle detection device that detects the angle of a detection surface portion including a surface facing the detector of the object with respect to a predetermined vertical plane, wherein the angle detection device includes: a point cloud acquisition unit that acquires point data at a plurality of locations on the detection surface portion as a point cloud; a trimming unit that extracts a point cloud within a predetermined height range from the point cloud acquired by the point cloud acquisition unit; an angle detection unit that projects the point cloud extracted in the trimming step in the vertical direction to generate a projection image, and detects the inclination of a straight line obtained by fitting to the point data appearing in the projection image as the angle of the detection surface portion. An angle detection system comprising the above components. ​ ​

Images