Position control method and position control device

Abstract

This position control method is for controlling the position of a suction pad and comprises: recognizing a workpiece to be suctioned; detecting the position of the workpiece; controlling the suction pad so as to approach the workpiece at a prescribed velocity; and controlling the suction pad, which is in contact with the workpiece, so as to be separated from the position of the workpiece at a separation velocity, on the basis of a result of recognition of the workpiece. The separation velocity is slower than the prescribed velocity.

Description

Position control method and position control device

[0001] The present disclosure relates to a position control method and a position control device for controlling the position of a suction pad.

[0002] Conventionally, there has been known a suction cup for suction-conveying an article, characterized in that the suction cup is configured by providing a small suction cup that opens around the lower end of the intake pipe and is fixed thereto, and a large suction cup that surrounds the small suction cup and opens concentrically with the small suction cup and is fixed thereto (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2003-225880

[0004] The present disclosure provides a position control method and a position control device that can improve the success rate of suction of a workpiece to be sucked by a suction pad.

[0005] One aspect of the present disclosure is a position control method for controlling the position of a suction pad, which recognizes a workpiece to be sucked, detects the position of the workpiece, controls the suction pad to approach the workpiece at a predetermined speed, and based on the result of the workpiece recognition, controls the suction pad that has come into contact with the workpiece to move away from the position of the workpiece at a removal speed, where the removal speed is slower than the predetermined speed.

[0006] One aspect of the present disclosure is a position control device that includes a processor and controls the position of an adsorption pad, wherein the processor recognizes a workpiece to be adsorbed, detects the position of the workpiece, controls the adsorption pad to approach the workpiece at a predetermined speed, and based on the results of the recognition of the workpiece, controls the adsorption pad that has come into contact with the workpiece to move away from the position of the workpiece at a release speed, wherein the release speed is slower than the predetermined speed.

[0007] According to the present disclosure, the success rate of suction of a workpiece to be sucked by a suction pad can be improved.

[0008] FIG. 14 is a diagram showing an example of the configuration of a picking system according to a first embodiment; FIG. 15 is a perspective view of the appearance of a robot device equipped with a suction pad on a suction hand; FIG. 16 is a side view of a suction pad; FIG. 17 is a perspective view of a suction pad viewed from diagonally below; FIG. 18 is a diagram for explaining the contact state between a suction pad and a workpiece; FIG. 19 is a diagram showing a first example of the relationship between differences in workpiece hardness and deformation amount; FIG. 20 is a diagram showing a second example of the relationship between differences in workpiece hardness and deformation amount; FIG. 21 is a diagram showing an example of work information; FIG. 22 is a diagram showing an example of picking setting information; FIG. 23 is a diagram showing an example of an update of picking setting information; FIG. 24 is a diagram showing an example of the positional relationship between a suction hand and a workpiece during a picking operation;

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0010] (Background to the development of the first embodiment) The suction pad of Patent Document 1 is used in a picking system or the like that picks up a workpiece to be picked up. In the picking system, a suction hand equipped with a suction pad descends toward the workpiece, picks up (grabs) the workpiece, and then rises while holding the workpiece in suction, performing a picking operation. In this case, the position of the workpiece is recognized and the suction hand descends toward the workpiece, but the accuracy of the recognized position of the workpiece may be low.

[0011] FIG. 18 is a diagram illustrating the detection accuracy required for detecting the position of an object. Referring to FIG. 18 , it can be seen that the detection accuracy required for workpieces to be picked up, such as small boxes and plastic bottles, is stricter than that required for depalletizing (sorting boxes), food distribution robots, or berth management. For example, when picking, a detection accuracy of several millimeters or around 1 mm is required to detect the position of workpieces such as plastic bottles and small boxes (piece picking of small objects). For example, when detecting the position using a known sensor, an error of about ±5 mm occurs.

[0012] Furthermore, when detecting the position of the workpiece by capturing images with a stereo camera in the direction of descent of the suction hand, the position of the workpiece relative to the suction hand is in the depth direction of the captured image, which further reduces detection accuracy. As a result, the suction hand is likely to descend excessively toward the workpiece. In this case, the lower end of the suction pad is likely to curl up, which can lead to failure in suction of the workpiece by the suction pad.

[0013] Furthermore, if the suction pad is flexible enough to hold bags such as plastic bags and has ribs, the suction pad's flexibility and ribs enable it to adsorb the workpiece, but when the suction pad is pressed against the workpiece to make it adhere closely to the workpiece, the suction pad is likely to curl up, with the ribs acting as a fulcrum. Excessive contact between the workpiece and the suction pad also makes the flange more likely to curl up. If the bottom end of the suction pad curls up, a gap forms between the suction pad and the workpiece, allowing air to flow in and resulting in a failure to adsorb the workpiece.

[0014] In the following embodiments, a position control method and a position control device that can improve the success rate of gripping a workpiece with a suction pad will be described.

[0015] 1 is a diagram showing an example of the configuration of a picking system 5 according to a first embodiment. The picking system 5 includes a robot device 10, a robot control device 100, and a work information server 200.

[0016] <Configuration of Robot Device> The robot device 10 is a picking robot that performs picking operations. In response to instructions from the robot control device 100, the robot device 10 picks up various workpieces (objects) to be picked up that are stored in a storage container, and moves them to an outgoing container for placement (storage). The robot device 10 has a robot arm and a suction hand. The robot arm moves the suction hand to any position in three-dimensional space. The suction hand is equipped with a suction pad. The suction pad picks up the workpiece. The robot device 10 may be any type of picking robot, and may be, for example, an orthogonal pickup robot, an orthogonal two-finger robot, or an articulated robot. Although the robot device 10 shown in FIG. 2 below is used as an example of the robot device 10, the configuration of the robot device 10 is not limited to this.

[0017] 2 is a perspective view of the appearance of a robot device 10 equipped with a suction pad 11 on a suction hand 13. In the diagram with arrows indicating directions, the X axis indicates the front-to-rear direction, the Y axis indicates the left-to-right direction, and the Z axis indicates the up-to-down direction. The X axis and Y axis are orthogonal to each other and are included in a horizontal plane. The Z axis is included in a longitudinal plane.

[0018] Containers 31, cardboard boxes, and the like that transport workpieces 29 can freely enter and exit the robot device 10. For example, the robot device 10 can transfer the workpieces 29 from a container 31 (e.g., a storage container) to another container (e.g., an outgoing container), and can perform a job of repacking the workpieces 29 between containers. A platform for the containers, etc., serves as a stage 27 for sorting.

[0019] A pair of columns 33, spaced apart in the X direction (front and back), are fixed to each of the left and right base beams 17 and stand upright in the Z direction. The upper ends of the four columns 33 support the four corners of a rectangular base frame 35 that surrounds a horizontal plane. A Y-axis rail 37 extending in the Y direction is supported on the base frame 35. An X-axis rail 39 extending in the X direction is supported on the Y-axis rail 37. A Z-axis rail 41 extending in the Z direction is supported on the X-axis rail 39.

[0020] A movable body 43 is provided on the Z-axis rail 41 so as to be movable up and down (Z direction). The Z-axis rail 41 moves in parallel along the X-axis rail 39 in the front-to-rear direction (X direction) perpendicular to the Z-axis rail 41. The X-axis rail 39 moves in parallel along the Y-axis rail 37 in the left-to-right direction (Y direction) perpendicular to the X-axis rail 39 and the Z-axis rail 41. Therefore, the movable body 43 is movable up and down (Z direction), front-to-rear (X direction), and left-to-right (Y direction) relative to the stage 27.

[0021] The Z-axis rail 41 that moves the moving body 43, the X-axis rail 39 that moves the Z-axis rail 41 in a direction perpendicular to the Z-axis rail 41, and the Y-axis rail 37 that moves the X-axis rail 39 in a direction perpendicular to the X-axis rail 39 and the Z-axis rail 41 constitute a robot arm 12 (see FIG. 1 ). The robot device 10 is configured by providing a suction hand 13 for the robot arm 12. In other words, the robot arm 12 holds the suction hand 13 so that it can move freely in three mutually perpendicular directions. The robot device 10 also has a motor or the like that supplies driving force to move the rails of each axis.

[0022] A vacuum generator 47 is provided above the movable body 43. A support pipe 49 extending in the Z direction is fixed to the lower side of the movable body 43. The upper end of the support pipe 49 is fixed to the movable body 43 by a mounting piece (not shown). The vacuum generator 47 is connected to the upper end of the support pipe 49 by a connecting tube (not shown). In other words, the inner diameter side of the support pipe 49 forms a vacuum path communicating with the negative pressure port and the atmospheric release port (not shown) of the vacuum generator 47. A suction pad 11 is fixed to the lower end of this pipe. The suction pad 11 is a bellows type formed in a bellows shape.

[0023] Fig. 3 is a side view of the suction pad 11. Fig. 4 is a perspective view of the suction pad 11 shown in Fig. 3 as seen obliquely from below.

[0024] The suction pad 11 is fixed to the lower end of the support pipe 49. The suction pad 11 includes a pad main body 55 whose diameter expands downward with an axis 53 aligned along the vertical axis, and a bellows tube 61 interposed between the pad main body 55 and the support pipe 49. In the suction pad 11, the pad main body 55 and the bellows tube 61 are arranged coaxially with the axis 53 as the center. The pad main body 55 has, on its lower surface, ribs 69 arranged in radial directions around the axis 53. The insides of the pad main body 55 and the bellows tube 61 form a vacuum path 51, which is connected to the vacuum path of the support pipe 49 and leads to the negative pressure port and the atmospheric release port of the vacuum generator 47.

[0025] The pad main body 55 has a diameter that expands toward its lower end along the axis 53. The pad main body 55 has a trumpet-shaped outer surface with a conical slope that expands downward. The pad main body 55 alone, or the pad main body 55 and the bellows tube 61, are formed, for example, from soft resin or rubber. When the pad main body 55 is formed, for example, from rubber, it has a predetermined rubber hardness. The rubber hardness decreases as the numerical value decreases, and increases as the numerical value decreases, indicating a hardness. For example, the hardness is approximately 10° for human skin and 60° or more for an automobile tire. The rubber hardness employed for the pad main body 55 of this embodiment is preferably, for example, approximately 20° to 45°. Furthermore, the thickness of the tip of the pad main body 55 is preferably 0.3 to 0.5 mm. By having a predetermined rubber hardness, the pad main body 55 provides adhesion and shape stability to the workpiece 29, such as a packaged product.

[0026] Although the suction pad 11 has been described here as being flexible enough to hold a bag, this is not limiting. The pad body 55 of the suction pad 11 may not have the flexibility to hold a bag. The suction pad 11 can be restored to its original shape even if it is deformed.

[0027] Returning to FIG. 1, the robot device 10 includes a robot arm 12, a suction hand 13, a vacuum generator 47, an overhead camera CA1, and a distance camera CA2.

[0028] The overhead camera CA1 is used, for example, to capture an image of the inside of the container 31 from above and recognize the state inside the container 31 and the state of the workpieces 29 inside the container 31. For example, the workpieces 29 can be recognized (detected) based on the image captured by the overhead camera CA1. The overhead camera CA1 may be installed, for example, at any position on the robot arm 12 of the suction hand 13, or may be installed at another position in the robot device 10.

[0029] The distance camera CA2 is, for example, a stereo camera, and can measure (detect, recognize) the distance from the distance camera CA2 to the workpiece 29 based on the captured image. Therefore, the height (e.g., z coordinate) of the workpiece 29 in three-dimensional space can be measured based on this captured image. Note that instead of measuring the distance using the distance camera CA2, the distance may be measured using another distance sensor. The distance camera CA2 may be installed, for example, at any position on the suction hand 13, or at another position on the robot device 10. Note that the overhead camera CA1 and the distance camera CA2 may also be configured as a single unit.

[0030] <Configuration of Robot Control Device> The robot control device 100 controls the robot device 10 in real time to perform a desired picking operation. The robot control device 100 monitors the operation of the robot device 10 in real time and can send predetermined instruction information to the robot control device 100.

[0031] The robot controller 100 includes a processor 110 , a memory 120 , an input device 130 , and a communication device 140 .

[0032] The processor 110 may be configured using, for example, a central processing unit (CPU) or a digital signal processor (DSP). The processor 110 may be configured using various integrated circuits (for example, a large scale integration (LSI) or a field programmable gate array (FPGA)). The processor 110 realizes various functions by executing programs stored in the memory 120. The processor 110 comprehensively controls each unit of the robot control device 100 and performs various processes.

[0033] The processor 110 controls the operation of the robot device 10 via the communication device 140. For example, the processor 110 may control the operation of the robot arm 12 and the suction hand 13 of the robot device 10 to control the picking operation of the robot device 10. The processor 110 may instruct the overhead camera CA1 to take an image and cause it to take an image. The processor 110 may instruct the distance camera CA2 to take an image and cause it to take an image. The processor 110 may control the operation (on / off, start and stop) of the vacuum generator 47 of the robot device 10.

[0034] The processor 110 acquires various types of information via the input device 130 or the communication device 140. For example, the processor 110 acquires captured images captured by the overhead camera CA1, captured images captured by the distance camera CA2, and detection information detected by a sensor. The processor 110 may detect various events based on the acquired captured images or detection information. For example, the processor 110 may detect (recognize) information about the workpieces stored inside the container 31 (e.g., the presence or absence, shape, weight, material, size, position, and distance to the workpieces 29 of the workpieces 29).

[0035] The memory 120 includes a primary storage device (e.g., Random Access Memory (RAM) or Read Only Memory (ROM)). The memory 120 may include a secondary storage device (e.g., a Hard Disk Drive (HDD) or a Solid State Drive (SSD)) or a tertiary storage device (e.g., an optical disk or an SD card). The memory 120 may also be an external storage medium, or may be detachable from the robot control device 100. The memory 120 stores various types of data, information, programs, etc.

[0036] The input device 130 may include various buttons, keys, a keyboard, a touch panel, a microphone, a sensor, or other input devices. The input device 130 accepts input of various data, information, and the like. The input device 130 may be operated, for example, by an administrator or an operator who manages the robot control device 100. A sensor may be provided, for example, inside or around each robot device 10. The sensor may include, for example, a vacuum sensor (e.g., a pressure sensor) that measures the degree of vacuum.

[0037] The communication device 140 communicates various data or information according to a wired or wireless communication method. The communication method used by the communication device 140 may include a local area network (LAN), a wide area network (WAN), a mobile phone network, power line communication, etc. The communication device 140 is connected to the robotic device 10, the work information server 200, etc., via a wired or wireless connection so as to be able to communicate with them.

[0038] For example, the communication device 140 sends an image capture instruction for the overhead camera CA1 to the robot device 10 and acquires the image captured by the overhead camera CA1 from the robot device 10. The communication device 140 sends an image capture instruction for the distance camera CA2 to the robot device 10 and acquires the image captured by the distance camera CA2 from the robot device 10. The communication device 140 sends an operation instruction to the robot device 10 for operating the robot arm 12, the suction hand 13, etc. The communication device 140 acquires information such as the position, angle, or posture of the robot arm 12, the suction hand 13, etc. from the robot device 10. The communication device 140 sends an instruction to measure the degree of vacuum in the suction hand 13 to the robot device 10 and acquires the vacuum degree measurement result from the robot device 10.

[0039] It should be noted that only one robot control device 100 may be provided for a plurality of robot devices 10, or one may be provided for each robot device 10.

[0040] <Configuration of Work Information Server> The work information server 200 is a database server that stores information related to workpieces (for example, workpiece information I1 (see FIG. 8)). The work information server 200 includes at least a processor, a memory, and a communication device. In FIG. 1, the work information server 200 is configured as a separate entity from the robot control device 100, but this is not limited to this. The memory 120 of the robot control device 100 may store the workpiece information I1. Details of the workpiece information I1 will be described later.

[0041] <Contact State Between Suction Pad and Workpiece> Next, the contact state between the suction pad 11 and the workpiece 29 will be described.

[0042] FIG. 5 is a diagram for explaining the contact state between the suction pad 11 and the workpiece 29. As shown in FIG.

[0043] The robot device 10 causes the suction hand 13 to perform a picking operation. The picking operation includes the suction hand 13 approaching (descending) toward the detection position (x, y, z) of the workpiece 29, the suction pad 11 contacting and suctioning the workpiece 29, and then moving away (rising) from the detection position of the workpiece 29. The detection position (x, y, z) of the workpiece 29 is the target descent position (x, y, z) (also referred to as the target descent position) for the suction hand 13 (specifically, the suction pad 11) to pick up the workpiece 29. Therefore, when controlling the picking operation, the processor 110 of the robot control device 100 controls the suction pad 11 to approach the workpiece 29 and to suck the inside of the suction hand 13, and, based on the recognition result of the workpiece 29, controls the suction pad 11, which has contacted the workpiece 29, to move away from the position of the workpiece 29.

[0044] Ideally, the contact state between the suction pad 11 located at the lower end of the suction hand 13 and the workpiece 29 is such that the end of the suction pad 11 on the workpiece 29 side (i.e., the lower surface of the pad body 55 of the suction pad 11) and the end (upper surface) of the workpiece 29 on the suction pad 11 side are flush with each other. In this case, the pad body 55 of the suction pad 11 is hardly deformed.

[0045] On the other hand, in reality, an error in the detection position of the workpiece 29 often causes the suction hand 13 to descend a large distance, causing the suction pads 11 to come into excessive contact with the workpiece 29 and deforming the workpiece 29 by the deformation amount D. Even in this case, the robot control device 100 can ensure time and space for the deformed workpiece 29 to restore itself by slowly raising the suction hand 13 at a separation speed that corresponds to the restoration time of the workpiece 29. The restoration time is the time required for the workpiece 29 to restore its shape after being deformed due to contact with the suction pads 11, etc. The separation speed is the moving speed of the suction hand 13 when it separates from the detection position of the workpiece 29.

[0046] Furthermore, the pad body 55 is often deformed due to excessive contact with the workpiece 29. The time required for the deformed pad body 55 to return to its original shape is shorter than the time required for the deformed workpiece 29 to return to its original shape. Therefore, the robot control device 100 can ensure the time and space required for the deformed workpiece 29 to return to its original shape by ensuring the time and space required for the deformed workpiece 29 to return to its original shape. In this way, by restoring both the workpiece 29 and the pad body 55, the lower surface of the suction pad 11 and the upper surface of the workpiece 29 can become flush with each other.

[0047] In this way, the robot control device 100 can ensure that the deformation of the workpiece 29 and the pad body 55 is restored at the right timing when the suction hand 13 rises after the suction pad 11 comes into contact with the workpiece 29. Therefore, the workpiece 29 and the pad body 55 become flush with each other when they come into contact with each other. Therefore, the robot control device 100 can ensure that the pad body 55 is in reliable contact with the workpiece 29, improve adhesion performance, and suppress air leakage.

[0048] <Hardness of Workpiece and Amount of Deformation> Next, the relationship between the difference in hardness of the workpiece 29 and the amount of deformation will be described.

[0049] 6 and 7 are diagrams showing an example of the relationship between the hardness of the workpiece 29 and the amount of deformation.

[0050] 6, the softer the work 29, the greater the deformation amount D of the work 29 and the easier it is to deform, so it is assumed that the work 29 is easier to restore and takes a longer time to restore. Examples of soft work 29 include work 29 with a fill top surface, work 29 packed in a pouch, work 29 packed in cardboard, and work 29 with a boiled water bag.

[0051] 7, it is presumed that the harder the workpiece 29, the smaller the deformation amount D of the workpiece 29 and the harder it is to deform, so it is harder to restore its original shape and the restoration time is shorter. In this case, even if the suction pad 11 comes into excessive contact with the workpiece 29, the workpiece 29 may not deform. Possible examples of a hard workpiece 29 include a workpiece 29 packed in cardboard, a workpiece 29 housed in a can or metal, etc.

[0052] <Restoration Time of Workpiece> Next, the restoration time of the workpiece 29 and the suction pad 11 will be considered.

[0053] When the suction hand 13 comes into contact with the workpiece 29, a restoring force acts on the workpiece 29 to return it to its original shape, depending on the characteristics of the workpiece 29. A predetermined time (restoration time TF) is required for the deformed workpiece 29 to return to its original shape (restore). In other words, the restoration time TF is the time required for the deformed workpiece 29 to restore its original shape. The restoration time TF differs for each workpiece 29 and for each packaging form into which the workpiece 29 is sorted.

[0054] The processor 110 of the robot control device 100 acquires information about the restoration time TF. For example, an administrator or the like may input the information about the restoration time via the input device 130, taking into account the characteristics of the workpiece 29 (e.g., the packaging form of the workpiece 29 or the contents of the workpiece 29), so that the processor 110 acquires the information about the restoration time TF. The processor 110 may also access an external server via the communication device 140 to acquire information about the restoration time derived according to the characteristics of the workpiece 29.

[0055] The processor 110 determines the detachment speed (particularly the detachment speed in the initial stage of detachment) (also referred to as the restoration speed) of the suction hand 13 (i.e., the suction pad 11) when it is detached, in accordance with the restoration time TF of the workpiece 29. For example, the processor 110 determines the restoration speed VF according to the following (Equation 1).

[0056] Restoration speed VF = constant K × (1 / restoration time TF) ... (Equation 1) For each work 29, the processor 110 transmits the identification information of the work 29, information on the characteristics of the work 29 (for example, information on the packaging form and contents of the work 29), information on the restoration time, and information on the restoration speed VF to the work information server 200 via the communication device 140, and stores the information in the work information server 200.

[0057] Although the example described here is one in which the robot control device 100 determines the restoration speed VF based on the restoration time TF, the present invention is not limited to this. For example, the picking system 5 may include an arbitrary information processing device such as a personal computer (PC), and the information processing device may determine the restoration speed VF based on the restoration time TF. The information processing device may then transmit the restoration speed VF and the like to the work information server 200, which may store them.

[0058] Furthermore, the ease with which the pad body 55 of the suction pad 11 turns over when it comes into contact with the workpiece 29 varies depending on the type of suction pad 11. Therefore, the processor 110 may determine the restoration speed VF based on the type of suction pad 11. In this case, the robot control device 100 can determine an appropriate restoration speed VF that is also suited to the type of suction pad 11.

[0059] <Details of Work Information> Fig. 8 is a diagram showing an example of work information I1. The work information I1 is stored in the work information server 200. The work information I1 includes, for example, at least the following information: identification information of the work 29, characteristics of the work 29 (e.g., the packaging form of the work 29 and characteristics of the contents), and restoration speed VF. The work information I1 may also include information on restoration time TF. The work information server 200 may store the work information I1, for example, by associating each piece of information included in the work information I1 for each work 29.

[0060] The restoration speed VF derived (for example, calculated) based on the restoration time is an upper limit value of the speed, and the robot controller 100 does not necessarily have to release the suction hand 13 at this speed. The robot controller 100 may release the suction hand 13 at a speed slower than the derived restoration speed VF.

[0061] <Details of Picking Setting Information> Next, picking setting information I2 related to the picking operation will be described.

[0062] FIG. 9 is a diagram showing an example of the picking setting information I2.

[0063] In the robot control device 100, the memory 120 stores picking setting information I2. The picking setting information I2 includes, for example, identification information of the workpiece 29 to be picked, the restoration speed VF of the workpiece 29, i.e., the ascent speed when the suction hand 13 is released, and the target descent position of the suction hand 13. Note that the detected position of the workpiece 29 may contain an error. During a picking operation, when the processor 110 detects a workpiece 29 to be picked up, the processor 110 generates picking setting information I2 for each recognized workpiece and stores it in the memory 120.

[0064] The processor 110 of the robot control device 100 causes the suction hand 13 to perform a picking operation based on the picking setting information I2. The processor 110 may cause the picking operation to be repeatedly performed, and may cause the picking operation to be performed again if, for example, the first picking operation fails to pick up an item. When causing the processor 110 to re-perform the picking operation, the processor 110 may change the picking conditions for the suction hand 13 to perform the picking operation, that is, may set retry conditions. When retry conditions are set, the processor 110 updates the picking setting information I2 based on the settings of the retry conditions and stores the updated information in the memory 120.

[0065] FIG. 10 is a diagram showing an example of updating the picking setting information I2.

[0066] Here, picking setting information I2 for adhesive bandages, instant curry, and boiled bamboo shoots is shown. In FIG. 10 , the retry condition is set to reduce the restoration speed VF to 80% for the second picking operation compared to the first picking operation. For the third picking operation, the retry condition is set to change the target descent position (x, y, z) of the suction hand 13 by one step. Even if the retry condition is set and the picking setting information I2 is updated, the processor 110 can appropriately retry (re-execute) the picking operation based on the updated picking setting information I2. Furthermore, the retry condition setting changes only the horizontal position (x, y) of the suction hand 13 at the target descent position by one step, and the vertical position (z) of the suction hand 13 at the target descent position (i.e., the target descent height) does not need to be changed. Furthermore, when setting the retry conditions, only the vertical position (z) (i.e., the target descent height) of the suction hand 13 at the target descent position is changed by one step, and the horizontal position (x, y) of the suction hand 13 at the target descent position does not need to be changed.

[0067] <Lifting Speed ​​of Suction Hand> Next, the lifting speed of the suction hand 13 during the picking operation will be described.

[0068] In the picking operation, the suction hand 13 descends toward the detection position (target descending position) of the workpiece 29, causing the suction pad 11 to approach the workpiece 29. In addition, the suction hand 13 ascends in the opposite direction to the workpiece 29, so that if suction is successful, the suction hand 13 will suck and grip the workpiece 29, and if suction is unsuccessful, the suction hand 13 will move away from the target descending position without gripping the workpiece 29. The movement, position, and speed of the suction hand 13 during the picking operation are controlled by the processor 110 of the robot control device 100.

[0069] <First Example of Picking Operation> Fig. 11 is a diagram showing an example of the positional relationship between the suction hand 13 and the workpiece 29 during a picking operation. Fig. 12 is a diagram showing a first example of a time-series change in the lifting speed of the suction hand 13.

[0070] 11, the movement speed (approach speed) when the suction hand 13 approaches the workpiece 29 is shown as a negative speed, and the movement speed (removal speed) when the suction hand 13 leaves the position of the workpiece 29 is shown as a positive speed. These negative and positive speeds are applied to FIG. 12 and FIG. 13, which will be described later.

[0071] 12 , when the picking operation is started at time t0, the suction hand 13 descends from the initial position of the picking operation (three-dimensional coordinates (x, y, 0)) to a predetermined position (for example, 10 mm in front) in front of the workpiece 29 at a constant approach speed VA. At this point (time t11), the pad body 55 of the suction pad 11 has not yet come into contact with the workpiece 29. The approach speed VA may be, for example, the maximum speed at which the suction hand 13 moves.

[0072] Next, at time t11, the suction hand 13 slowly descends (approaches) to the workpiece 29 from the previous predetermined position while decelerating the approach speed VA. When the suction hand 13 reaches the target descending position (three-dimensional coordinates (x, y, z + error)) at time t12, the lifting and lowering speed of the suction hand 13 becomes 0 (zero). At time t12, the suction pad 11 is in contact with the workpiece 29, but there is a possibility that the suction pad 11 may be in excessive contact with the workpiece 29 due to an error in detecting the position of the workpiece 29. Even in this case, the robot control device 100 can prevent damage to the workpiece 29 by approaching the suction hand 13 to the workpiece 29 while decelerating the speed.

[0073] Furthermore, at time t12, the processor 110 starts the vacuum generator 47, and starts suction of the workpiece 29 by the suction pad 11. The processor 110 may start the vacuum generator 47 when the suction hand 13 approaches.

[0074] Next, at time t12, the suction hand 13 slowly rises (detaches) from the target descent position. At this time, the suction hand 13 rises at a restoration speed VF to a predetermined detachment position (e.g., a position 2 to 3 mm above the descent point). As described above, the restoration speed VF varies depending on the workpiece 29 and the packaging form of the workpiece. While FIG. 12 shows the restoration speed VF gradually increasing, it may also be a constant speed. By slowly raising the suction hand 13 at the restoration speed VF until time t13, the robot control device 100 can ensure time and space for the deformed workpiece 29 and pad body 55 to restore their original shape. Therefore, the pad body 55 of the suction pad 11 of the suction hand 13 can adsorb the workpiece 29 in a flush state.

[0075] The suction hand 13 rises at the restoration speed VF from time t12 to time t13, and then accelerates and rises at an acceleration speed that has a speed increase rate greater than the restoration speed VF until time t13. At time t14, the suction hand 13 returns to the initial position of the picking operation (three-dimensional coordinates (x, y, 0)). After time t14, the suction hand 13 transports the picked-up workpiece 29, for example, toward another container, at a predetermined transport speed VB (cruising speed).

[0076] When the processor 110 of the robot control device 100 starts the vacuum generator 47, that is, when it starts controlling the suction inside the suction hand 13, it monitors the degree of vacuum (pressure) inside the suction hand 13 (specifically, the inside of the support pipe 49 and the suction pad 11, the vacuum path 65, etc.) and monitors whether a vacuum state is maintained inside the suction hand 13 by suctioning a suitable workpiece 29. For example, if the degree of vacuum is greater than a predetermined threshold, the processor 110 can determine that the pressure inside the suction hand 13 has been sufficiently reduced, and therefore suction has been successful. If the degree of vacuum is equal to or less than the predetermined threshold, the processor 110 can determine that the pressure inside the suction hand 13 has not been sufficiently reduced, and therefore suction has failed.

[0077] According to this first example of the picking operation, the robot controller 100 can ensure time and space for the workpiece 29 and suction pad 11 to restore while separating at the restoration speed VF. Furthermore, the robot controller 100 can determine the degree of vacuum within the suction hand 13 while separating the suction hand 13 from the workpiece 29, and can therefore confirm the timing of successful suction during separation at the restoration speed VF. If the processor 110 determines that suction was successful during separation at the restoration speed DF, it may begin the subsequent operation of separation at an accelerated ascending speed early, without waiting for the completion of the restoration time. This allows the robot controller 100 to quickly complete the picking operation of the workpiece 29.

[0078] <Second Example of Picking Operation> Fig. 13 is a diagram showing a second example of the time series change in the lifting and lowering speed of the suction hand 13. In Fig. 13, differences from the first example shown in Fig. 12 will be mainly described.

[0079] As shown in Fig. 13, first, when the suction hand 13 descends (approaches) from time t0 to t22, the time series change of the suction hand 13 is the same as the first example of the picking operation shown in Fig. 12. Time t21 corresponds to time t11, and time t22 corresponds to time t12.

[0080] Next, at time t22, the suction hand 13 rises (detaches) at high speed from the target lowering position to a predetermined detachment position that is above the target lowering position by a distance (for example, 2 to 3 mm) smaller than the thickness M of the workpiece 29. Also, at time t22, the processor 110 has not yet started the vacuum generator 47, and has not yet started suction of the workpiece 29 by the suction pad 11. In other words, the robot control device 100 ensures a space for the workpiece 29 and the pad body 55 to return to their original position without suctioning the workpiece 29.

[0081] When the suction hand 13 reaches the release position at time t23, the processor 110 starts the vacuum generator 47, and the suction pad 11 begins suctioning the workpiece 29. Also, at time t23, the suction hand 13 again reduces its rising speed and slowly rises (releases) at a constant restoration speed VF. At this time, the suction hand 13 may rise at the restoration speed VF, which gradually increases the speed, as in FIG. 12 . By raising the suction hand 13 at the slow restoration speed VF until time t24, the robot control device 100 can ensure that the deformed workpiece 29 and pad body 55 have time to restore their original shape. Therefore, the pad body 55 of the suction pad 11 of the suction hand 13 can suction the workpiece 29 in a flush state.

[0082] The suction hand 13 rises at the restoration speed from time t23 to time t24, and then accelerates and rises at an acceleration speed whose rate of increase is greater than the restoration speed VF until time t25. At time t25, the suction hand 13 returns to the initial position (three-dimensional coordinates (x, y, 0)) of the picking operation. After time t25, the suction hand 13 transports the picked-up workpiece 29, for example, toward another container, at a predetermined transport speed VB.

[0083] According to this second example of the picking operation, the robot control device 100 can ensure space for rapid restoration by quickly releasing the suction hand 13 to the release position after contacting the workpiece 29. This makes it easier for the workpiece 29 and the pad body 55 to be quickly restored.

[0084] 14 and 15 are flowcharts showing an example of the operation of the picking system 5. Here, it is assumed that the approximate position where the workpiece 29 to be picked up is placed is determined in advance by the mechanical design of the robot device 10. It is assumed that, at the start of the processing in FIG. 14 , the container 31 storing the workpiece 29 has arrived at and been placed at the specified position.

[0085] The processor 110 of the robot control device 100 moves the suction hand 13 to a position directly above the container 31 in which the object to be picked (object to be picked up) is stored (S11).

[0086] The processor 110 recognizes the workpiece 29 to be picked up based on the image captured by the overhead camera CA1. The processor 110 detects the position of the workpiece 29 based on at least one of the image captured by the overhead camera CA1 and the images captured by both the overhead camera CA1 and the distance camera CA2 (S12). The position of the workpiece 29 is expressed, for example, by three-dimensional coordinates (x, y, z).

[0087] The processor 110 moves the suction hand 13 to a position directly above the detected position (i.e., the target lowering position) of the workpiece 29 (S13). The position directly above the workpiece 29 is expressed by, for example, three-dimensional coordinates (x, y, 0).

[0088] The processor 110 lowers the suction hand 13 (specifically, the suction pad 11) toward the target lowering position (S14). The target lowering position is expressed, for example, by three-dimensional coordinates (x, y, z + error).

[0089] The processor 110 starts the vacuum generator 47 (S15). The processor 110 accesses the workpiece information server 200 via the communication device 140, refers to the workpiece information I1, and reads and acquires the restoration speed VF corresponding to the recognized workpiece 29 (S16). As a result, the processor 110 determines the restoration speed VF according to the workpiece 29 to be sucked.

[0090] The processor 110 raises the suction hand 13 at the acquired restoration speed VF (S17). In this case, the suction hand 13 is raised slowly, taking into account the restoration time required for the deformed workpiece 29.

[0091] The processor 110 sequentially acquires measured values ​​(degree of vacuum) from a vacuum sensor (for example, a pressure sensor) that measures the degree of vacuum, and monitors the degree of vacuum in the space inside the suction hand 13 using the vacuum generator 47 (S18).

[0092] The processor 110 determines whether the acquired degree of vacuum is greater than or equal to a threshold value th1 (e.g., 750 mbar) (S19). If it is determined that the acquired degree of vacuum is greater than or equal to the threshold value th1 (Yes in step S19), the processor 110 determines that the suction of the workpiece 29 has been successful and raises the suction hand 13 at an acceleration speed corresponding to the weight of the workpiece 29 (S20). In this case, the processor 110, for example, decreases the acceleration speed as the weight of the workpiece 29 increases, and increases the acceleration speed as the weight of the workpiece 29 decreases. The acceleration speed is a speed for preventing the suction pad 11 from coming off the workpiece 29 after suction of the workpiece 29. The position of the suction hand 13 after raising is, for example, three-dimensional coordinates (x, y, 0), similar to step S13. The processor 110 moves the suction hand 13 toward the outgoing container at the transport speed VB (S21).

[0093] In step S19, if it is determined that the degree of vacuum (first degree of vacuum) is equal to or less than threshold value th1 (No in step S19), the processor 110 determines that suction of the workpiece 29 has failed. Then, the processor 110 determines whether the number of times the degree of vacuum has been checked (i.e., the number of times the determination has been made in step S19) is less than threshold value th2 (S22). If the number of times the degree of vacuum has been checked is less than threshold value th2 (Yes in step S22), the processor 110 proceeds to step S19 and repeatedly determines the degree of vacuum during detachment.

[0094] If the number of times the degree of vacuum has been checked is equal to or greater than the threshold value th2 (Yes in step S22), the processor 110 sets a retry condition for retrying (re-executing) the picking operation (S23).

[0095] The retry conditions include, for example, a position condition regarding the horizontal position of the suction hand 13 and a speed condition regarding the restoration speed VF. The horizontal position is expressed, for example, by two-dimensional coordinates (x, y). When setting the retry conditions, these position conditions and speed conditions are adjusted. In other words, the processor 110 determines the details of the picking operation retry by controlling the three parameters x, y, and VF in the retry conditions.

[0096] As a first example of setting a retry condition, it is conceivable to retry the picking operation by changing the restoration speed VF. In this case, the processor 110 sets the retry condition by changing only the speed condition.

[0097] As a second example of setting a retry condition, it is possible to retry the picking operation by changing the horizontal position of the suction hand 13. In this case, the processor 110 sets the retry condition by changing only the position condition (i.e., only the two-dimensional coordinates (x, y)). When changing the position condition, the processor 110, as an example, searches the vicinity of the detected position (target drop position) of the workpiece 29 that failed to be picked up, and changes the horizontal position of the suction hand 13 to a position that is either 4 or 8 steps away from the suction hand 13.

[0098] As a variation of the second example of setting the retry condition, it is possible to retry the picking operation by changing the height position of the suction hand 13. In this case, the processor 110 sets the retry condition by changing only the height condition (i.e., only the z coordinate) among the position conditions. When changing the position condition, the processor 110, as one example, searches for an area near the detection height (target drop height) of the workpiece 29 that failed to be picked up, and changes the height position of the suction hand 13 to any nearby position by shifting it by the step distance.

[0099] As a third example of setting the retry condition, it is possible to retry the picking operation by changing both the restoration speed VF and the horizontal position of the suction hand 13. In this case, the processor 110 sets the retry condition by changing the speed condition and the position condition.

[0100] The processor 110 raises the suction hand 13 to the retry position (S24). The retry position is the initial position of the suction hand 13 for retrying the picking operation. If the position condition of the retry condition is not changed, the horizontal position of the suction hand 13 is not changed. Furthermore, the height direction (vertical direction) of the retry position is somewhere between the height of the initial position (0) of the picking operation and the height of the predetermined release position. Note that the retry position when setting the position condition may be set to a higher position than the retry position when setting the speed condition. This is because it is easier to ensure safety during the picking operation.

[0101] After the suction hand 13 is placed at the retry position in step S24, the process proceeds to step S17. That is, the processor 110 re-executes the picking operation starting from the retry position. Specifically, the processor 110 lowers the suction hand 13 from the retry position to the target lowering position (x, y, z + error), the suction hand 13 contacts the workpiece 29, and then raises the suction hand 13 again at the restoration speed VF. Note that the horizontal position (x, y) of this target lowering position may have been changed by the retry condition setting. Also, the restoration speed VF may have been changed by the retry condition setting.

[0102] Therefore, when a speed condition is set as a retry condition, the processor 110 performs the following process: That is, the processor 110 acquires information about the degree of vacuum in the suction hand 13 that has left the detection position of the workpiece 29 at the initially determined restoration speed VF, and if the degree of vacuum is equal to or lower than the threshold value th1, reduces the determined restoration speed VF and re-executes the picking operation.

[0103] Furthermore, if a picking operation according to a retry condition in which a speed condition is set fails and a position condition is also set as a retry condition, the processor 110 performs the following processing. That is, the processor 110 may acquire information about the degree of vacuum inside the suction hand 13 that has left the detection position of the workpiece 29 at the reduced restoration speed VF. If the degree of vacuum is equal to or lower than the threshold value th1, the processor 110 may change the target descent position (detection position of the workpiece 29) to a position a predetermined distance away from the target descent position in a direction perpendicular to the direction in which the suction hand 13 approaches and leaves (for example, the horizontal direction), and re-execute the picking operation.

[0104] The processor 110 may repeatedly retry the picking operation, i.e., repeat the processing of steps S17 to S24. Assume that in the first round, a retry condition for the speed condition of the first example is set in step S23, and a retry of the picking operation with this setting fails. Assume that in the second round, a retry condition for the position condition of the second example is set in step S25, and a retry of the picking operation with this setting also fails. In this case, the processor 110 may output warning information. The output of the warning information may be notified to various output devices (e.g., speakers, displays) in the warehouse or factory where the picking operation is being performed, and the output device may present the warning information (e.g., display, sound output).

[0105] 16 is a diagram showing an example of a target descent position when retrying a picking operation. Here, it is assumed that the position condition is changed and the retry condition is repeatedly set each time pickup fails.

[0106] During the first picking operation, position P1 relative to the workpiece 29 is the target lowering position of the suction hand 13. During the second picking operation (first retry), position P2 relative to the workpiece 29 is the target lowering position of the suction hand 13. During the third picking operation (second retry), position P3 relative to the workpiece 29 is the target lowering position of the suction hand 13. During the fourth picking operation (third retry), position P4 relative to the workpiece 29 is the target lowering position of the suction hand 13. In this way, the processor 110 can determine a different horizontal position as the target lowering position each time the picking operation is retried, which is expected to increase the success rate of suction.

[0107] In addition, when the processor 110 of the robot control device 100 succeeds in adsorption by retrying the picking operation, the robot control device 100 may update the picking setting information I2 by associating the identification information of the workpiece 29 that was successfully adsorbed with at least one of the restoration speed VF and the target descent position at the time of successful adsorption, and store the information in the memory 120. The target descent position information stored here may be only the horizontal position (x, y), only the vertical position (z) (i.e., the target descent height), or both (i.e., three-dimensional position (x, y, z). For example, when the processor 110 is successful in suction by retrying the picking operation with the speed conditions set, the processor 110 may store information on the identification information of the workpiece 29 and the lowered restoration speed VF in the memory 120, and may also store information on the target descent position. For example, when the processor 110 is successful in suction by retrying the picking operation with the position conditions set, the processor 110 may store information on the identification information of the workpiece 29 and the changed target descent position in the memory 120, and may also store information on the restoration speed VF. The target descent position information stored here may be only the horizontal position (x, y), only the vertical position (z) (i.e., the target descent height), or both (i.e., three-dimensional position (x, y, z). For example, when the processor 110 is successful in suction by retrying the picking operation with the speed conditions set, the processor 110 may store information on the identification information of the workpiece 29 and the lowered target descent position in the memory 120, and may also store information on the restoration speed VF. If the target descent position is a horizontal position, only the horizontal position (x, y) may be stored. If the changed target descent position is a vertical position (target descent height), only the vertical position (z) (target descent height) may be stored. Furthermore, if the changed target descent position is a three-dimensional position, the target descent position may be a three-dimensional position. This allows the robot control device 100 to increase the likelihood of successful suction on the first try by performing the picking operation based on the picking setting information I2 containing information on successful suction. As described above, if the degree of vacuum (second vacuum) in the suction hand 13 after a retry of the picking operation is greater than the threshold value th1, the above information may be stored in the memory 120.

[0108] As described above, the picking system 5 of this embodiment determines the restoration speed VF based on the ease of restoration of the workpiece 29 (e.g., restoration time) and controls the movement speed when the workpiece 29 is released from the picking operation. The distance (approach distance) to the workpiece 29 when the suction hand 13 approaches the workpiece 29 may be detected with low accuracy, resulting in an error. In this case, the robot control device 100 lowers the suction hand 13 to the maximum extent possible within the error range, thereby approaching and contacting the workpiece 29 and deforming the workpiece 29. Even in this case, the robot control device 100 reduces the restoration speed VF when the suction hand 13 is raised, i.e., when the suction hand 13 is released, ensuring time and space for the deformed portion of the workpiece 29 to fully restore itself, thereby improving the success rate of suction.

[0109] In the present embodiment, the direction in which the suction hand 13 approaches and leaves the workpiece 29 is a direction along the vertical direction, but this is not limited to this. For example, when suctioning the workpiece 29 placed on a shelf, the direction in which the suction hand 13 approaches and leaves the workpiece 29 may be a direction along the horizontal direction, or may be any direction other than the vertical and horizontal directions.

[0110] In the present embodiment, the work information server 200 is provided independently, but this is not limiting. The picking system 5 may not include the work information server 200, and may instead store information stored by the work information server 200 (e.g., work information I1) in the memory 120 of the robot control device 100.

[0111] In the above embodiment, the restoration speed VF is derived mainly based on the ease of restoration of the workpiece 29. However, this is not limiting. The processor 110 may derive (e.g., calculate) the restoration speed VF according to a characteristic of the workpiece 29 (e.g., weight, material) other than the ease of restoration.

[0112] Next, the relationship between the weight of the workpiece 29 and the restoring speed VF will be considered.

[0113] When the suction hand 13 suctions the workpiece 29, friction occurs between the pad body 55 of the suction pad 11 and the workpiece 29. The friction force (friction coefficient) is determined based on the normal force of the workpiece 29 and the static or kinetic friction force of the workpiece 29. The normal force of the workpiece 29 is proportional to the weight of the workpiece 29. Therefore, the heavier the workpiece 29, the greater the friction force, making it less likely that the pad body 55 will turn over. This reduces the likelihood of a gap occurring between the suction pad 11 and the workpiece 29, suppressing air leakage and improving the success rate of suction. On the other hand, the lighter the workpiece 29, the smaller the friction force, making it more likely that the pad body 55 will turn over. This increases the likelihood of a gap occurring between the suction pad 11 and the workpiece 29, making suction more likely to fail. Therefore, the processor 110 of the robot control device 100 may determine the restoration speed VF based on the weight of the workpiece 29. For example, the heavier the workpiece 29 is, the faster the restoration speed VF may be, and the lighter the weight of the workpiece 29 is, the slower the restoration speed VF may be. Furthermore, regarding the relationship between weight and acceleration speed, the processor 110 may, for example, as described above, slow the acceleration speed as the weight is heavier, and fast the acceleration speed as the weight is lighter.

[0114] Furthermore, when the suction surface of the workpiece 29 and the suction pad are in close contact with each other, the pad body 55 is less likely to peel off. On the other hand, when the suction surface of the workpiece 29 and the suction pad are not in close contact with each other, the pad body 55 is more likely to peel off. Therefore, the processor 110 may determine the acceleration speed according to the material of the workpiece 29. For example, the acceleration speed may be set higher if the suction surface of the workpiece 29 is smoother, such as a coated gift box, and lower if the suction surface of the workpiece 29 is rougher, such as cardboard.

[0115] The processor 110 may transmit, for each work 29, the identification information of the work 29, information regarding the characteristics of the work 29 (e.g., the weight and material of the work 29), and information regarding the acceleration speed to the work information server 200 via the communication device 140, and store the information in the work information server 200.

[0116] 17 is a diagram showing an example of workpiece information I1A. The workpiece information I1A is held in the workpiece information server 200. The workpiece information I1A includes, for example, at least the following information: identification information of the workpiece 29, characteristics of the workpiece 29 (e.g., the weight and material of the workpiece 29), and acceleration speed. The method of using the workpiece information I1A is the same as the workpiece information I1 in the above embodiment.

[0117] (Summary of the embodiment) As described above, the present disclosure describes at least the following matters. Note that, in parentheses, examples of components corresponding to the above-described embodiment are shown, but the present disclosure is not limited to these.

[0118] (Item 1) A position control method for controlling the position of a suction pad (suction pad 11), comprising: recognizing a workpiece (workpiece 29) to be sucked; detecting the position of the workpiece; controlling the suction pad to approach the workpiece at a predetermined speed; and controlling the suction pad that has come into contact with the workpiece to move away from the position of the workpiece based on the workpiece recognition result; and a movement speed (restoration speed VF) during the movement when moving away is slower than the predetermined speed.

[0119] As a result, the position control method moves the suction pad at a separation speed (a moving speed when separating that is slower than the speed when approaching) when separating from the position of the workpiece, which makes it easier to ensure time and space for the workpiece and suction pad to return to their original position. Therefore, the position control method makes it easier for the suction pad to be flush with the workpiece, improving the success rate of suction.

[0120] (Item 2) The position control method according to Item 1, wherein the moving speed during the separation is a speed based on a restoration time (restoration time TF) required for the workpiece to restore from a deformed state.

[0121] As a result, the position control method moves the suction pad at a separation speed that takes into account the recovery time when the suction pad separates from the position of the workpiece, thereby ensuring time and space for the workpiece and suction pad to recover. Therefore, the position control method makes the suction pad flush with the workpiece, improving the success rate of suction.

[0122] (Item 3) The position control method according to Item 2, wherein the restoration time is determined based on the workpiece.

[0123] As a result, the restoration time differs depending on the characteristics of the workpiece, but the position control method can determine a release speed that is suitable for the characteristics of the workpiece.

[0124] (Item 4) The position control method according to Item 3, wherein the restoration time is determined based on a packaging form of the workpiece.

[0125] As a result, although the ease of suction by the suction pad varies depending on the packaging form of the workpiece, the position control method can determine a removal speed that is suitable for the characteristics of the packaging form.

[0126] (Item 5) The position control method according to any one of Items 1 to 4, wherein the movement speed during the detachment is a speed based on the type of the suction pad.

[0127] As a result, the likelihood of the suction pad turning over when it comes into contact with a workpiece differs depending on the type of suction pad, but the position control method can determine a release speed that is appropriate for the type of suction pad.

[0128] (Item 6) A position control method according to any one of items 1 to 5, comprising: acquiring information on the degree of vacuum within a suction hand (suction hand 13) equipped with the suction pad that has been detached from the position of the workpiece at the movement speed during the detachment; and, if the degree of vacuum is equal to or less than a threshold, reducing the movement speed during the detachment to control the suction pad to approach the workpiece, controlling the suction pad to suck inside the suction hand, and controlling the suction pad to detach from the position of the workpiece.

[0129] As a result, the position control method can increase the success rate of suction by slowing down the removal speed and ensuring sufficient time for restoration before retrying the picking operation.

[0130] (Item 7) A position control method according to Item 6, wherein information on the degree of vacuum within the suction hand that has left the position of the workpiece at the reduced movement speed during the removal is acquired, and when the degree of vacuum is greater than the threshold value, the workpiece identification information and the reduced movement speed during the removal are stored in a memory.

[0131] This allows the position control method to record a method for improving the release speed when pickup has failed once. Therefore, if the recognized workpiece matches the workpiece stored in memory after recording in memory, the position control method sets the release speed at which pickup was successful as the initial speed, thereby increasing the possibility of successful pickup from the start and shortening the time until pickup is completed.

[0132] (Item 8) A position control method according to any one of items 1 to 7, comprising: acquiring information on the degree of vacuum within a suction hand equipped with the suction pad that has separated from the position of the workpiece at the movement speed during the separation; and, if the degree of vacuum is equal to or less than a threshold value, changing the detected position of the workpiece to a position a predetermined distance away from the position of the workpiece in a direction perpendicular to the direction in which the suction hand approaches and separates, thereby controlling the suction pad to approach the workpiece, controlling the suction pad to suck inside the suction hand, and controlling the suction pad to separate from the position of the workpiece.

[0133] This allows the position control method to fine-tune the target lowering position of the suction pad by changing the detected position of the workpiece, which is expected to increase the success rate of suction.

[0134] (Item 9) A position control method according to Item 8, further comprising: acquiring information on the degree of vacuum within the suction hand that has been removed from the changed position of the workpiece; and, if the degree of vacuum is greater than a threshold, storing in memory information on the workpiece's identification information, the changed position of the workpiece, and the removal speed.

[0135] This allows the position control method to record how to improve the detected position of a workpiece that has previously failed to be picked up (the target approach position of the suction pad). Therefore, if the recognized workpiece matches the workpiece stored in memory after recording in memory, the position control method sets the workpiece position that was successfully picked up (e.g., the horizontal position) as the target initial position (e.g., the horizontal position) of the suction pad, thereby increasing the likelihood of successful suction from the start and shortening the time until suction is completed.

[0136] (Item 10) A position control method according to any one of items 1 to 9, wherein the detected position includes a height of the workpiece, and the position control method acquires information about the degree of vacuum within a suction hand equipped with the suction pad that has departed from the position of the workpiece at the moving speed at the time of the detachment, and if the degree of vacuum is equal to or less than the threshold value, changes the detected height of the workpiece, controls the suction pad to approach the workpiece, controls the suction pad to suck inside the suction hand, and controls the suction pad to depart from the position of the workpiece.

[0137] This allows the position control method to fine-tune the target lowering height of the suction pad by changing the detected workpiece height, which is expected to increase the suction success rate.

[0138] (Item 11) A position control method according to Item 10, further comprising: acquiring information on the degree of vacuum within the suction hand that has been removed from the changed height of the workpiece; and, if the degree of vacuum is greater than the threshold value, storing in memory information on the workpiece identification information and the changed height of the workpiece.

[0139] This allows the position control method to record a method for improving the detected height (target approach height of the suction pad) of a workpiece that has previously failed to be picked up. Therefore, if the recognized workpiece matches the workpiece stored in memory after recording in memory, the position control method sets the height of the workpiece that was successfully picked up as the target initial height of the suction pad, thereby increasing the likelihood of successful suction from the start and shortening the time until suction is completed.

[0140] (Item 12) A position control device (robot control device 100) that includes a processor (processor 110) and controls the position of a suction pad, wherein the processor: recognizes a workpiece to be picked up; detects the position of the workpiece; controls the suction pad to approach the workpiece at a predetermined speed; and, based on the workpiece recognition result, controls the suction pad that has come into contact with the workpiece to move away from the position of the workpiece; and the moving speed during the movement when moving away is slower than the predetermined speed.

[0141] This allows the position control device to obtain the same effect as in item 1.

[0142] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0143] In addition, the above embodiment may also be applicable to a program that realizes the functions of the position control method, which is supplied to a computer (e.g., the robot control device 100) via a network or various storage media, and which is read and executed by the processor of this computer, as well as to a storage medium on which this program is stored.

[0144] The present disclosure is useful for a position control method and a position control device that can improve the success rate of suction of a workpiece by a suction pad.

[0145] 5 Picking system 10 Robot device 11 Suction pad 12 Robot arm 13 Suction hand 29 Workpiece 47 Vacuum generator 55 Pad body 100 Robot control device 110 Processor 120 Memory 130 Input device 140 Communication device CA1 Bird's-eye view camera CA2 Distance camera

Claims

1. A position control method for controlling the position of a suction pad, comprising: recognizing a workpiece to be sucked; detecting the position of the workpiece; controlling the suction pad to approach the workpiece at a predetermined speed; and, based on the result of the workpiece recognition, controlling the suction pad that has come into contact with the workpiece to move away from the position of the workpiece at a release speed, wherein the release speed is slower than the predetermined speed.

2. The position control method according to claim 1, wherein the removal speed is a speed based on the restoration time required for the workpiece to restore its original shape from a deformed state.

3. The position control method according to claim 2, wherein the restoration time is determined based on the workpiece.

4. The position control method according to claim 3, wherein the restoration time is determined based on the packaging form of the workpiece.

5. The position control method according to claim 1 or 2, wherein the removal speed is a speed based on the type of the suction pad.

6. A position control method as described in claim 1 or 2, which acquires information on a first degree of vacuum within a suction hand equipped with the suction pad that has been removed from the position of the workpiece at the removal speed, and if the first degree of vacuum is equal to or less than a threshold value, reduces the removal speed, controls the suction pad to approach the workpiece, controls the suction hand to suck, and controls the suction pad to remove from the position of the workpiece.

7. A position control method as described in claim 6, further comprising: acquiring information on a second degree of vacuum within the suction hand that has been removed from the position of the workpiece at the reduced removal speed; and, if the second degree of vacuum is greater than the threshold value, storing in memory information on the workpiece's identification information and the reduced removal speed.

8. A position control method as described in claim 1 or 2, which includes acquiring information about a first degree of vacuum within a suction hand equipped with the suction pad that has departed from the position of the workpiece at the removal speed, and if the first degree of vacuum is equal to or less than a threshold value, changing the position of the detected workpiece to a position a predetermined distance away from the position of the workpiece in a direction perpendicular to the direction in which the suction hand approaches and departs, controlling the suction pad to approach the workpiece, controlling it to suck inside the suction hand, and controlling the suction pad to depart from the position of the workpiece.

9. A position control method as described in claim 8, further comprising: acquiring information on a second degree of vacuum within the suction hand that has moved away from the changed position of the workpiece; and, if the second degree of vacuum is greater than the threshold value, storing in memory information on the workpiece's identification information and the changed position of the workpiece.

10. A position control method as described in claim 1 or 2, wherein the detected position includes the height of the workpiece, and the position control method acquires information on a first degree of vacuum within a suction hand equipped with the suction pad that has departed from the position of the workpiece at the depart speed, and if the first degree of vacuum is equal to or less than a threshold value, changes the detected height of the workpiece, controls the suction pad to approach the workpiece, controls the suction pad to suck inside the suction hand, and controls the suction pad to depart from the position of the workpiece.

11. A position control method as described in claim 10, further comprising: acquiring information on a second degree of vacuum within the suction hand that has moved away from the changed height of the workpiece; and, if the second degree of vacuum is greater than the threshold value, storing in memory information on the workpiece's identification information and the changed height of the workpiece.

12. A position control device having a processor that controls the position of a suction pad, wherein the processor recognizes a workpiece to be picked up, detects the position of the workpiece, controls the suction pad to approach the workpiece at a predetermined speed, and based on the result of the recognition of the workpiece, controls the suction pad that has come into contact with the workpiece to move away from the position of the workpiece at a release speed, and the release speed is slower than the predetermined speed.

Images