Gripping device and picking system

Abstract

To provide a technology for realizing picking which has high versatility, can be introduced at a low cost, and improves gripping reliability.SOLUTION: A picking system 1 is characterized in that a gripping device for gripping an item includes: a gripping device 40 consisting of at least two arms 41 arranged rotationally symmetrically about a central axis and having pads 43 at tips of the arms with a predetermined coefficient of friction for making surface contact with the item; an opening and closing base 42 narrowing and widening the arms themselves symmetrically about the axis center while holding base ends of the arms, where each arm is composed of a link mechanism; and an air cylinder 44 that expands and contracts an inner arm 41a of each link mechanism to change an angle of the pad, where the gripping device is capable of gripping the item by narrowing the arms and changing the angle of the pad.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a picking system (pickup system) used when transferring parts and the like stacked in a container to a conveyor or the like, and a gripping device which is a main component thereof, and more particularly to a picking technology capable of realizing an operation for enhancing gripping reliability after an arm contacts a part.

Background Art

[0002] Conventionally, there has been known a picking robot that takes out the same-shaped parts stacked in large numbers in a container and transfers them to a belt conveyor or the like. Here, since the postures of the parts are not uniform and they are also stacked in the depth direction, the conventional picking robot inputs accurate shape data of the parts, stereo-images the article group with a high-precision vision sensor, collates the data by contour matching or point cloud matching, and determines the gripping position of the article. In other words, all calculations are completed before moving on to the gripping operation, and although each operation is different, the approach to the article and the movement during gripping were determined individually in advance. Therefore, there has been a problem that the vision sensor needs to use a high-performance model such as acquiring information in high definition using a plurality of optical systems, and the introduction cost becomes extremely high. In addition, although CAD data is generally adopted as the accurate shape data of the article, it is necessary to individually input the data every time the target article changes, and in order to collate this with a large amount of information from the vision sensor, a high-performance processing system (PC or the like) is required, and in any case, there has been a problem that it is costly. In addition, the determination of the gripping position requires tuning every time the type of part changes, and there has also been a problem that it takes several months or more in some cases until operation. That is, in the conventional technology, picking is performed by performing high-precision processing in advance, and separate delicate tuning is required, so that the system becomes extremely expensive and operation also takes time.

[0003] In addition, there is a picking device with enhanced versatility like the prior patent technology (Patent Document 1) by the inventor of the present application. However, in the case of two arms that rotate around the base end such that the other end side opens or closes its mouth, as can be understood by considering an example of picking a spherical object, there is a problem that the upper hemisphere is pinched and the gripping reliability is not high. Further, when the gripping unit descends, even if the arm hits a component and a displacement occurs, picking is performed as it is, and there is a problem that the gripping reliability may be impaired including the case where gripping is impossible.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above, and an object thereof is to provide a technology that realizes picking with high versatility, can be introduced at low cost, and enhances gripping reliability.

Means for Solving the Problems

[0006] The gripping device according to claim 1 is a gripping device for gripping an article, comprising a gripping unit consisting of at least two arms having pads at their tips, which are arranged rotationally symmetrically with respect to a central axis and have a predetermined coefficient of friction for making surface contact with the article, a holding opening / closing unit that holds the base ends of the arms and symmetrically narrows and widens the arms themselves with respect to the axis center, and each arm is constituted by a link mechanism, and further comprising expansion / contraction means for changing the angle of the pad by expanding and contracting a corresponding single link of each link mechanism, characterized in that the arms are narrowed and the angle of the pad is changed to enable gripping of the article.

[0007] That is, in the invention according to claim 1, the angle of the pad can be easily changed separately from the narrowing of the arms, whereby it is also possible to grip the article from the side. Also, it is possible to hold the article in a surrounding angle (if the gripping in Document 1 is expressed as a V-shaped grip, it can be a reverse V-shaped grip to enhance the gripping reliability and gripping stability). For example, assuming that a parallel link mechanism is configured as a reference link, the normal direction of the pad does not change regardless of the phase of the link, but by shortening (or lengthening) one link, the normal direction can be easily changed to achieve more appropriate gripping. The design and gripping control also become easier.

[0008] The corresponding link means that since each link mechanism is composed of the same (congruent) links arranged rotationally symmetrically, it means a single link at the same position. Narrowing the arms themselves symmetrically with respect to the axis center means that each arm rotates so that the other ends (the pads) approach each other with the base end as the center. In addition, it can also be in a mode where the base ends themselves approach, or a mode where the entire arms approach. Consisting of at least two arms means that in the case of two arms, they may be arranged facing each other so that the pads face each other, and in the case of three arms, they are arranged and oriented with 120° rotational symmetry, and in the case of four arms, they are arranged and oriented with 90° rotational symmetry. The pad surface is preferably made of a material with a large frictional force such as rubber. The telescoping means can be configured as the air cylinder described in claim 3, or can be a separately provided electric cylinder. In the case of an electric cylinder, it is also possible to use a solenoid to provide a buffering action similar to that of an air cylinder.

[0009] The gripping device according to claim 2 is the gripping device according to claim 1, wherein each pad incorporates a tactile sensor, and based on the output values from the plurality of tactile sensors, the center position or the center of gravity position of the article is estimated to enable gripping of the article.

[0010] That is, the invention according to claim 2 enables more appropriate gripping using a contact sensor. Since it is a tactile sensor, the direction of the center of curvature of the article on the contact surface can be grasped. Depending on the specification mode, it is also possible to follow any deviation such as movement during gripping.

[0011] A tactile sensor refers to a sensor that, in addition to detecting the presence or absence of contact with an object, appropriately quantifies the degree of contact and outputs it. While a pressure sensor outputs a single numerical value at a single point or an average value as one numerical value, a tactile sensor outputs, for example, pressure values at a plurality of locations in a plane generally perpendicular to the direction in which the load is applied, and can evaluate the degree or aspect of contact (such as pinpoint pressure application, contact tilted to the right, pulsation, the direction of the center of curvature of the contact surface, etc.). (In this sense, a pressure sensor can also be used as a tactile sensor by combining a plurality of them within a certain proximity range and using their respective output values.) It is also possible to perform control to monitor the gripping pressure in real time, detect that the article is about to fall, and increase the gripping pressure.

[0012] The gripping device according to claim 3 is the gripping device according to claim 1 or 2, wherein the telescoping means is constituted by an air cylinder.

[0013] That is, the invention according to claim 3 simply realizes a buffering grip without applying excessive pressure.

[0014] The picking system according to claim 4 is a picking system that picks up articles one by one from above the air from a container in which articles of the same shape are randomly stored, and includes a vision sensor that acquires three-dimensional information of the article group in the container, and based on the three-dimensional information of the article group acquired by the vision sensor, collating determination means for forcibly collating the articles with one of a circle, a sphere, an ellipsoid, a square, a rectangle, a cube, a cuboid, and other sample figures to determine the position directly above each article, a gripping unit including at least two arms having pads with a predetermined coefficient of friction for making surface contact with the articles at their tips, arranged rotationally symmetrically with respect to the central axis, a holding opening / closing unit that holds the base ends of the arms and symmetrically narrows and widens the arms themselves with respect to the axis center, each arm is constituted by a link mechanism, and telescopic means for changing the angle of the pad by extending and retracting a corresponding one of the links of each link mechanism, moving means for moving the gripping unit to a position directly above any one of the articles and lowering and raising it, a tactile sensor is built into each pad, and gripping control means for controlling the moving means to lower the gripping unit, controlling the holding opening / closing unit to narrow the arm interval based on the detection of contact with the article by the tactile sensor, controlling the telescopic means to change the angle of the pad, gripping the article, and controlling the moving means to raise the gripping unit.

[0015] That is, the invention according to claim 4 combines rough position grasping of unpacked articles by forced collation and on-site position grasping by a tactile sensor, and further enables more appropriate gripping while searching for articles by simply changing the angle of the pad, without requiring high-spec sensors and processing systems. As a result, a system with high versatility and low cost can be constructed. Since on-site correction or on-site response is performed, time-consuming tuning is not required, rapid operation is also realized, and gripping reliability is improved.

[0016] Note that the initial opening angle of the arm before lowering is set to such an extent that the pad touches the article (not to an opening that is too wide for the pad to be detected). For example, the angle in the central axis direction with respect to the normal direction of the pad surface can be set to 75° to 55°. Either the control to narrow the arm interval or the control to change the angle of the pad may be performed first. The directly above position and the lowering (raising) are in a broad sense, and include not only the up and down on the vertical line, but also the forward and backward modes with an angle from the diagonally upward to the diagonally downward. The three-dimensional information refers to the position information of the surface of the group of articles. That is, it is information including the depth (depth) information. It does not need to be as highly detailed as the high-resolution image information, and it may be three-dimensional information appropriately meshed or dotted so that the shape of the article can be roughly grasped. This reduces the number of data and eliminates the need for a high-spec visual sensor and processing system. Note that the visual sensor may also be referred to as a depth sensor. Also, there is no limitation on the measurement method of the three-dimensional information, and for example, the Active Stereo method, the Time of Flight method, the Coded Light method, etc. can be cited. The sample figure may be set on the user side, or the optimal candidate may be automatically selected based on the three-dimensional information from the visual sensor. A simple sample figure can be adopted to reduce the processing burden. The processing and collation processing of the three-dimensional information may utilize a large-scale point cloud processing library such as the PointCloudLibrary (PCL). Prior to the collation, a pre-processing of enlarging and reducing the set sample figure to approach the article can also be performed. At the time of collation, it may be determined that the overlap between the figure and the contour of the object is the largest, or an example of comparing the degree of coincidence with the normal direction of each surface can be cited. Of course, the figure can be rotated for trial evaluation, and based on the depth direction information, the size of the set figure may be adjusted separately from the above pre-processing. The directly above position calculated by the collation is not only directly above the center of the figure, but depending on the article, it can also be a position shifted according to a predetermined rule. The picking-up order is preferably in the order of the height of the articles based on the three-dimensional data. Grasping the article based on the contact detection of the article by the tactile sensor means that not only simply narrowing after the contact, but also, for example, an operation control such as further lowering the 1 mm grasping unit and then narrowing may be included.

[0017] The picking system according to claim 5 is the picking system according to claim 4, and includes position estimation means for estimating the center position or the center of gravity position of an article based on output values from a plurality of tactile sensors. The gripping control means performs control to release the pad from the article once, and based on the position estimated by the position estimation means, controls the moving means, the holding opening / closing part, and the telescopic means to perform gripping again.

[0018] That is, the invention according to claim 5 can also realize groping article gripping and follow-up gripping when the article moves.

Effect of the Invention

[0019] According to the present invention, it is possible to provide a technology that realizes picking with high versatility, can be introduced at low cost, and enhances gripping reliability.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a pickup example using two arms will be described.

[0022] FIG. 1 is a schematic external view of the picking system of the present invention. For convenience of explanation, the scales of the respective components in each figure are not necessarily the same. The picking system 1 picks up the same-shaped articles stored in a container C one by one and transfers them to a belt conveyor (not shown). Hereinafter, the process up to the main picking operation will be described in detail, and the subsequent transfer operation to the conveyor will be omitted. Transfer control can be easily realized using general-purpose technology.

[0023] Conventional picking systems input the CAD data of articles in advance, perform complete collation based on three-dimensional information (3D data) or depth data photographed with high definition and high resolution, grasp all the positions and postures of the articles, and then precisely determine the gripping operation to pick up the articles. On the other hand, as will be described below, the present invention is significantly different in that it roughly grasps the position and posture of an article and determines the gripping operation on-site. In addition, a crank mechanism is adopted to realize more stable gripping.

[0024] The picking system 1 mainly includes a vision sensor 10, an articulated robot 20, a processing device 30, and a gripping device 40.

[0025] The vision sensor 10 photographs the area including the container C from above the placement surface of the container C and acquires three-dimensional information of the article group. More specifically, it acquires uneven information of the article group including how the articles overlap. The imaging method is not particularly limited, but here, the Coded Light (IR) method is adopted. An example of such a vision sensor can be the Intel RealSense (registered trademark) SR300. It is equipped with an infrared projector, an infrared camera, and an RGB camera, is inexpensive, and can easily acquire three-dimensional information. Figure 2 shows an example of a Stanford Bunny with a height of approximately 77 mm (Figure 2a), a reconstructed image of three-dimensional information obtained by photographing it with a vision sensor (Figure 2b), a recognition image of the actual Stanford Bunny stacked in a container (Figure 2c) described later, and an image showing the state of forced matching with a sphere (Figure 2d). The dot interval of the reconstructed image can be arbitrarily set to be less than or equal to the resolution, but depending on the size and shape of the parts to be handled, it can be set to 1 mm to 5 mm. In other words, in order to reconstruct an article with several hundred to several thousand dots and match it with the graphic for matching described later, neither the vision sensor 10 nor the processing device 30 needs to be high-spec and can be introduced at low cost.

[0026] Due to its structure, the articulated robot 20 can freely move and orient the gripping device 40. Thereby, the gripping device 40 is positioned above the article to be picked up next, and is caused to perform a descending, ascending, and placing operation on the conveyor. In the present embodiment, it is assumed that the approaching operation and the retreating operation are performed on a vertical line, and the orientation direction of the gripping device 40 is also on the vertical line.

[0027] The gripping device 40 is composed of two identical arms 41 and an opening / closing base portion 42 that attaches and opens / closes the arms 41. Figure 3 is a schematic diagram showing the external configuration of the gripping device 40. The two arms 41 are arranged symmetrically with respect to the center line M (line symmetry or 180-degree rotational symmetry in the present embodiment), and are each composed of a four-bar link mechanism that moves symmetrically. Two points of the arm 41 are fixed in position to the opening / closing base portion 42, and the inner arm 41a and the outer arm 41b rotate around the two points respectively. A gripping arm 41c is attached to the other ends of the arm 41a and the arm 41b, one side is extended, and a pad 43 for gripping an article is attached. The pad 43 is substantially rectangular in plan view and has a predetermined thickness, and realizes surface contact following the article surface by sinking in the thickness direction. Further, the surface is covered with a rubber film, and the gripping reliability of the article is enhanced based on its friction coefficient (and surface contact).

[0028] Here, for the sake of convenience of explanation, it is assumed that the above-described four-link mechanism forms a parallel link mechanism except for article gripping, and the pads 43 also face each other in parallel (Fig. 3a). Since it is a parallel link mechanism, the arms 41a and 41b rotate while maintaining a parallel positional relationship, widening or narrowing the interval between the pads 43. At this time, the pads 43 also maintain a relationship of facing each other in parallel. This opening and closing operation is performed by a drive unit (not shown) in the opening and closing base portion 42, and the drive control thereof is performed by the processing device 30. Since a link mechanism is adopted, the locus of the pads 43 during operation can be easily grasped, and the drive design becomes easy.

[0029] However, immediately before gripping an article, the pads 43 are oriented at an angle so as to wrap the article (Fig. 3b). That is, the pads 43 are controlled so that their normal lines swing slightly toward the opening and closing base portion 42 side from being parallel. This is achieved by driving the air cylinder 44 provided in the middle of the inner arm 41a to shorten the arm length. The drive control of the air cylinder 44 is also performed by the processing device 30. Due to the movement of these pads 43, conventionally, when the pads were likely to grip an article in an outwardly open state, it is possible to easily realize gripping with an angle change so as to hold the article. Particularly, in the arrangement relationship between the inner arm a and the outer arm 41b shown in Fig. 3a, if the entire arm 41 is narrowed as it is, the gripping arm 41c will face more outward. However, in the gripping device 40, since the inner arm 41a is contracted by the air cylinder 44, an inwardly closed wrapping is possible. Also, due to the buffering property of the air pressure using the air cylinder 44, it is possible to realize the transfer of soft articles without the gripping strength exceeding a certain level.

[0030] The pad 43 also has a multi-point tactile sensor 45 embedded therein so that it can recognize the shape or shape change of the article on the contact surface. Specifically, it is formed by a displacement sensor group of 4 points × 2 columns, and a least-squares plane is calculated from the measurement data of 8 points so that the change in the center of gravity from the plane during non-contact and the change in the angle of the plane can be calculated. Thereby, the orientation control of the pad 43 is also added, enabling more appropriate gripping of the article. Depending on the specification mode, or when the article moves, dynamic control and follow-up gripping can also be realized. FIG. 4 is an explanatory diagram (FIG. 4a) showing the concept of the center of gravity direction and angle change of the article calculated by the processing device 30 based on the data from the tactile sensor, and an explanatory diagram (FIG. 4b) showing that the center of gravity position can be estimated from two center of gravity directions.

[0031] Next, the processing device 30 will be described. The processing device 30 can use a so-called personal computer, and general-purpose products can be adopted for the CPU, memory, storage, monitor, etc., so the detailed description of the hardware is omitted here. As a specific functional configuration of the processing device 30, it has a three-dimensional information input unit 31, a sample graphic setting unit 32, a collation unit 33, a directly above calculation unit 34, a multi-joint control unit 35, a tactile information input unit 36, a determination unit 37, and an opening / closing / expansion / contraction control unit 38. FIG. 5 is a block diagram showing the functional configuration of the processing device 30. The multi-joint control unit 35 and the opening / closing / expansion / contraction control unit 38 mainly perform the gripping control referred to in the claims. These functional units are realized by the cooperation of software such as a processing program and an OS installed in the processing device 30 and each hardware.

[0032] The three-dimensional information input unit 31 sequentially inputs the three-dimensional information of the article group acquired by the visual sensor 10. Although not shown, the visual sensor 10 may be moved so that the spatial arrangement of the article group can be recognized more accurately. The sample graphic setting unit 32 sets a graphic for collation based on simple graphics such as a circle, a sphere, an ellipsoid, a square, a rectangle, a cube, and a cuboid, and the three-dimensional information input from the three-dimensional information input unit 31. From the three-dimensional information, the surface unevenness of the group of articles can be understood, and based on the information of the parts with a large difference in the depth direction value, the outline of each article in the upper layer can be roughly determined while being randomly arranged (it is particularly suitable to use the outline at a particularly high position). Based on this information, a matching figure is selected. In this embodiment, the matching is performed by a sphere. Also, the sphere used for matching is the one after the radius has been appropriately adjusted. In addition, a spheroid with adjusted three-axis lengths or a rectangular parallelepiped with adjusted three-side lengths can also be used.

[0033] The matching unit 33 forcibly matches the sphere, which is the matching figure, with the article based on the three-dimensional information (Fig. 2d). Since there is almost no discontinuity in the outline of the articles in the upper layer, the ones with a small discontinuity rate are matched (and picked up). The method of matching is not particularly limited, but for example, in maximum likelihood estimation, based on feature quantities such as the surface shape of the target article including the outline and the normal direction of each point, the sphere is moved little by little to calculate the position where the volume overlap rate is the highest, and if it is equal to or greater than a predetermined value, it is determined that the matching has been performed (the two figures match). Note that since the three-dimensional information is input sequentially, after picking up, the three-dimensional information of the article that was originally at the back appears, and this updated three-dimensional information is used for the next matching.

[0034] The directly above calculation unit 34 determines (sets) the position directly above the center or centroid of the sphere that has been matched by the matching unit 33. Also, the directly above calculation unit 34 re-sets the directly above by the matching unit 33 again even when the article shifts after the arm 41 makes contact.

[0035] The multi-joint control unit 35 controls the multi-joint robot 20 to move the gripping device 40 to directly above the center of the article to be gripped that has been set or re-set by the directly above calculation unit 34. At this time, the gripping device 40 is posture-controlled so that its center line M faces vertically downward. Then, the multi-joint control unit 35 lowers the gripping device 40, and after gripping the article, raises it again. Thereafter, the article is appropriately placed on a conveyor or the like, returns above the container C again, and picking is repeated.

[0036] At the time of gripping, when the determination unit 37 detects the contact of the pad 43 with the article, the multi-joint control unit 35 moves the gripping device 40 to the other arm 41 side. Then, when the contact with the pad 43 on the other arm 41 side is detected, the multi-joint control unit 35 moves the gripping device 40 so that the center line M comes to the intermediate position between the two contact positions. In preparation for subsequent gripping (narrowing of the arm 41 and changing the angle of the pad 43), the gripping device 40 is appropriately lowered a predetermined distance deep (i.e., downward).

[0037] The tactile information input unit 36 sequentially inputs pressure values from a total of 16 locations of the two tactile sensors 45.

[0038] The determination unit 37 determines whether either of the tactile sensors 45 has detected contact with the article as the gripping device 40 is lowered by the multi-joint control unit 35. Further, the determination unit 37 determines whether the tactile sensor 45 of the opposite arm 41 has detected contact with the article by the multi-joint control unit 35. Furthermore, the determination unit 37 estimates the center of gravity position of the article based on the pressure values of the two tactile sensors 45 or the transition of the pressure values (Fig. 4). The determination unit 37 re-determines the center position of the article to be gripped on-site, so to speak, causes the arm 41 to enter, and the pad 43 also cooperates, thereby realizing more stable gripping of the article. Also, even if the article is displaced or moves, follow-up gripping can be realized.

[0039] The opening / closing and telescopic control unit 38 narrows the interval between the arms 41 symmetrically with respect to the center line M of the gripping device 40, and also performs control to independently tilt the pad 43 to sandwich the article. Specifically, based on the contact of the two tactile sensors 45, after the multi-joint control unit 35 moves the center line M of the gripping device 40 therebetween, the opening / closing and telescopic control unit 38 drives the air cylinder 44 to narrow the arm 41 to grip the article. The control mode can also be changed according to the shape, surface properties, rigidity, specific gravity, etc. of the article to be gripped. For example, when gripping, after moving to the intermediate position, prior to formal gripping, one-end temporary gripping can be performed, the signals from the tactile sensors 45 can be recalculated, and drive control can be performed so as to achieve more appropriate gripping. This operation may be repeated a plurality of times as necessary. Follow-up gripping is also possible. Note that the spreading interval of the arm 41 before the start of the descent of the gripping device 40 is appropriately set based on the three-dimensional information.

[0040] As described above, the picking system 1 enables introduction of a highly versatile and inexpensive system, does not require tuning or the like by responding to the site, and realizes prompt operation (transfer, etc.).

[0041] Note that the present invention is not limited to the above aspects. For example, when the article is extremely light or has a high elastic modulus, there is a possibility that the article will be repelled at the first contact during normal operation. In such a case, a proximity detection function may be added to the contact sensor, and the contact speed may be made gentle. Alternatively, the gripping unit may be moved so as to determine contact with proximity and search for the second contact (subsequent descent, probing operation, etc. are the same as usual, but it is preferable to reduce the speed of various movements until picking).

[0042] Also, in the above example, the case of a parallel link mechanism has been described, but the lengths of the opposing links may be made different. Even in this case, the length of the inner arm 41a (which may be another arm depending on the specification aspect) is adjusted, and control is performed so that the pad performs more suitable gripping.

Industrial Applicability

[0043] According to the present invention, it is possible to inexpensively realize random picking of a general-purpose industrial robot by vision and touch, and promote system introduction and productivity improvement in small and medium-sized enterprises.

Explanation of Signs

[0044] 1 Picking system 10 Vision sensor 20 Articulated robot 30 Processing device 31 Three-dimensional information input unit 32 Sample figure setting unit 33 Collation unit 34 Directly above calculation unit 35 Articulated control unit 36 Tactile information input unit 37 Judgment unit 38 Opening / closing / expansion / contraction control unit 40 Gripping device 41 Arm (41a: inner arm, 41b: outer arm, 41c: gripping arm) 42 Opening / closing base part 43 Pad 44 Air cylinder 45 Tactile sensor C Container M Center line

Claims

1. A gripping device for gripping an article, comprising a gripping unit consisting of at least two arms having pads at their tips, which are arranged rotationally symmetrically with respect to a central axis and have a predetermined coefficient of friction for making surface contact with the article; a holding opening / closing part that holds the base ends of the arms and symmetrically narrows and widens the arms themselves with respect to the axis center; each arm is constituted by a link mechanism, and a telescoping means for changing the angle of the pad by telescoping a corresponding single link of each link mechanism; and is characterized in that the arms are narrowed and the angle of the pad is changed to enable gripping of the article.

2. Each pad incorporates a tactile sensor, and the gripping device according to claim 1, characterized in that the central position or the center of gravity position of the article is estimated based on output values from a plurality of tactile sensors to enable gripping of the article.

3. The gripping device according to claim 1 or 2, characterized in that the telescoping means is constituted by an air cylinder.

4. A picking system for picking up one by one articles from a container in which articles of the same shape are randomly stored from above, a vision sensor for acquiring three-dimensional information of the article group in the container; collating determination means for forcibly collating the articles based on the three-dimensional information of the article group acquired by the vision sensor and determining the directly above position of each article by one of a circle, a sphere, an ellipsoid, a square, a rectangle, a cube, a cuboid, and other sample figures; a gripping unit consisting of at least two arms having pads at their tips, which are arranged rotationally symmetrically with respect to a central axis and have a predetermined coefficient of friction for making surface contact with the article; a holding opening / closing part that holds the base ends of the arms and symmetrically narrows and widens the arms themselves with respect to the axis center; Each arm is constituted by a link mechanism, and includes a telescopic means for changing the angle of the pad by extending and contracting a corresponding link of each link mechanism, a moving means for moving the gripping unit to a position directly above any article and also for lowering and raising it, each pad incorporates a tactile sensor, and gripping control means for controlling the moving means to lower the gripping unit, controlling the holding opening / closing part to narrow the arm interval based on detection of contact with the article by the tactile sensor, controlling the telescopic means to change the angle of the pad, gripping the article, and controlling the moving means to raise the gripping unit, characterized by comprising the above. A picking system.

5. comprising position estimation means for estimating the center position or the center of gravity position of the article based on output values from a plurality of tactile sensors, The gripping control means performs control to once release the pad from the article, and based on the position estimated by the position estimation means, controls the moving means, the holding opening / closing part, and the telescopic means to perform gripping again. The picking system according to claim 4.

Images