Multi-finger hand for robot, picking robot and picking device

Abstract

To provide a multi-finger hand for a robot, capable of efficiently performing pickup irrespective of a difference in the size and weight of a picking object.SOLUTION: A multi-finger hand for a robot includes: a plurality of fingers for grabbing a picking object; a drive mechanism for driving the plurality of fingers; a bag body disposed at the tip portion each of the plurality of fingers, and having a hollow place in the inside, and flexibility allowing deformation according to the picking object; an MR fluid enclosed in the hollow place of the bag body; an electric magnet for applying a magnetic field to the MR fluid; and a strain gauge installed in a place not directly abutted on the picking object in the bag body, and measuring an amount of strain of the bag body.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a robot hand, a picking robot, and a picking device that can pick up various objects by deforming according to the object to be picked up and do not become too heavy.

Background Art

[0002] Conventionally, as one form of the hand part of a picking robot, there is a multi-fingered hand for gripping an object to be picked up by a plurality of fingers.

[0003] As a multi-fingered hand, for example, Patent Document 1 has already been proposed. This Patent Document 1 discloses a mechanism of a robot hand with a locking mechanism that can grip an object with a complex shape by a plurality of fingers.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the multi-fingered hand described in Patent Document 1, it is possible to grip an object of an appropriate size well. However, for example, when picking up small bolts, screws, etc., a gap is formed at the tip of the finger, and the bolts and screws often fall out from there. In addition, there is also a multi-fingered hand that employs a mechanism for gripping an object picked up by a reaction force such as a spring. However, when holding a heavy object, the spring often loses and the object slips through the fingertips. That is, there has been a demand for a multi-fingered hand that can efficiently pick up objects regardless of the size and weight of the object to be picked up.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide a multi-fingered hand, a picking robot, and a picking device capable of efficiently picking up regardless of the size and weight of the object to be picked.

Means for Solving the Problems

[0007] The multi-fingered hand for a robot according to the present invention is a multi-fingered hand for a robot to be connected to a picking robot for picking up an object to be picked, and includes a plurality of fingers for grasping the object to be picked, a drive mechanism for driving the plurality of fingers, a flexible bag provided at the tip portion of each of the plurality of fingers, having a hollow portion inside and being deformable following the object to be picked, an MR fluid enclosed in the hollow portion of the bag, an electromagnet for applying a magnetic field to the MR fluid, and a strain gauge installed at a portion of the bag that does not directly contact the object to be picked for measuring the amount of strain of the bag.

[0008] Further, in the multi-fingered hand for a robot according to the present invention, the plurality of fingers are two, each finger has at least one or more joints, the bag has a substantially rectangular parallelepiped shape, and the drive mechanism employs a link mechanism for always maintaining the contact surface of the substantially rectangular parallelepiped-shaped bag at the tip with respect to the object to be picked substantially parallel even when the two fingers are opened and closed.

[0009] The picking robot according to the present invention is characterized by including any one of the above-described multi-fingered hands for a robot.

[0010] The picking device according to the present invention is a picking robot including a hand unit for picking a picking target object, a position specifying means for specifying the position of the picking target object, and a control unit for controlling the picking operation of the picking robot. The hand unit includes a plurality of fingers for gripping the picking target object, a drive mechanism for driving the plurality of fingers, a flexible bag provided at the tip portion of each of the plurality of fingers, having a hollow portion inside and being deformable following the picking target object, an MR fluid enclosed in the hollow portion of the bag, an electromagnet for applying a magnetic field to the MR fluid, and a strain gauge installed at a portion of the bag that does not directly contact the picking target object for measuring the strain amount of the bag. The control unit has a function of executing a position specifying procedure for specifying the position of the picking target object based on the position specifying means, a gripping procedure for gripping the specified picking target object with the plurality of fingers of the hand unit, a gripping strength adjustment procedure for adjusting the gripping strength based on the strain amount of the bag measured by the strain gauge, a curing procedure for applying a magnetic field to the MR fluid by the electromagnet to cure it, and a moving procedure for moving the picking target object to a target position.

Effect of the Invention

[0011] According to the present invention, the MR fluid is enclosed inside the bag provided at the tip of each of the plurality of fingers. When the picking target object is gripped with the plurality of fingers, since the magnetic field is not applied to the MR fluid before that, the bag can be deformed flexibly following the picking target object to create a state of being in close contact with various objects. Also, by measuring the strain amount of the bag with the strain gauge installed on the bag, the gripping strength can be estimated and adjusted to an appropriate gripping strength for the picking target object. When a magnetic field is applied to the MR fluid after the gripping strength is adjusted, the MR fluid cures in a state where the bag is in close contact with the picking target object and the close contact state is maintained. As a result, it becomes possible to appropriately grip various objects regardless of the difference in size and weight by the bag deforming following the picking target object, and it also becomes possible to appropriately set the gripping strength.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0013] Hereinafter, with reference to the drawings, an example of the picking device according to the embodiment of the present invention will be described.

[0014] FIG. 1 is an explanatory diagram for explaining the overall configuration of the picking device corresponding to the embodiment of the present invention. As shown in FIG. 1, the picking device 100 includes a picking robot 10, a hand part (including the case where it is expressed as a multi-fingered hand for a robot) 20, a position specifying means 30, and a control unit 40. Further, in this example, a situation where the picking object 50 is picked by the picking robot 10 is assumed.

[0015] The picking robot 10 is a robot equipped with a hand unit 20 that picks up the object to be picked 50. In this example, the picking robot 10 equipped with a multi-fingered hand unit 20 that grips the object to be picked 50 with a plurality of fingers will be described. The operation of this picking robot 10 is controlled by a control unit 40 described later. Also, in this example, as an example of a multi-fingered hand for a robot, a two-fingered hand will be described.

[0016] The position specifying means 30 is a configuration for specifying the position of the object to be picked 50. The position specifying means 30 may be any means as long as it can specify the position of the object to be picked 50. When the purpose is to specify the position of the object to be picked 50 in a two-dimensional plane (the position in the plane where the object to be picked 50 is placed), the position specifying means 30 may be, for example, a two-dimensional camera. Various arrangements can be adopted for the installation location of the two-dimensional camera. For example, it can be considered to be provided near the hand unit 20 of the picking robot 10. As long as the object to be picked can be photographed, the photographing angle can be set in various ways. However, when the purpose is to specify the position in a two-dimensional plane, it is preferable to install the two-dimensional camera so as to photograph the object to be picked 50 from above. The execution of photographing by this two-dimensional camera is controlled by a control unit 40 described later.

[0017] Also, when the position specifying means 30 is intended to specify the position (3D coordinate information of each point of the picking object 50) including the distance information to each point of the picking object 50, the position specifying means 30 can, for example, acquire the distance information using a stereo camera. Additionally, other configurations such as using a TOF camera (Time-of-Flight Camera) or LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) to acquire the distance information may also be possible. The distance information is acquired as 3D point cloud information. The acquisition of the distance information in this position specifying means 30 is controlled by the control unit 40 described later. The device for acquiring this distance information can have various shooting angles as long as it can shoot the picking object 50, but it is preferably installed so as to shoot the picking object 50 from above. When a stereo camera is adopted as the position specifying means 30, one piece of the captured image data by the stereo camera can be treated as the captured image data by a 2D camera, and the distance information can be acquired using two pieces of the captured image data by the stereo camera.

[0018] The control unit 40 is configured to control the positioning of the picking target object 50 by the positioning means 30 and the picking operation by the picking robot 10. The control unit 40 may be configured by any means as long as it can execute the control described later. For example, it may be realized by a computer, a microcomputer, a PLC (Programmable Logic Controller), or a combination thereof. Among these, a computer includes a CPU (Central Processing Unit), a memory, and a storage such as a hard disk drive or an SSD, and also includes an input device such as a mouse and a keyboard, an output device such as a display and a printer, and a communication device for connecting to a communication network, and these may be configured to be connected via a bus. The processing in each part of the control unit 40 is realized by reading a program for executing the processing in each part from the memory and executing it in a CPU, a GPU, or an FPGA (Field Programmable Gate Array) that functions as a control circuit (Processing circuit, Processing circuitry). In other words, by executing the program, the processor (processing circuit) is configured to be able to execute each process of each device. Also, a configuration is conceivable in which the processing up to the acquisition of the information on the recommended picking position of the picking target object 50 is executed by a computer, and the operation control of the picking robot 10 using the information on the recommended picking position is realized using a PLC. Needless to say, various data used in the control unit 40 and various data obtained as a result of the processing by the control unit 40 are appropriately stored in the storage unit.

[0019] In addition, in FIG. 1, the control unit 40 is described as being provided outside the picking robot 10, but it is not limited to this, and a configuration in which a control unit corresponding to the control unit 40 is provided inside the picking robot 10 may also be possible.

[0020] FIG. 2 is a perspective view showing an example of the configuration of the hand portion of the picking robot corresponding to the embodiment of the present invention. As shown in FIG. 2, in this example, the hand portion 20 attached to the picking robot 10 is a two-finger hand having two fingers 21. A bag body 22 is provided at the tip portion of each of the two fingers 21. This bag body 22 has a hollow portion inside and has flexibility that can be deformed following the picking object 50. As long as it can be deformed following the picking object 50, various materials can be applied to the bag body 22. For example, silicone rubber, resin sheet, rubber sheet, etc. can be considered.

[0021] Further, MR fluid (Magneto Rheological Fluid, also referred to as magnetorheological fluid or magnetic fluid) is enclosed in the hollow portion inside the bag body 22. The MR fluid may be any fluid as long as it can achieve a predetermined hardness that can hold the shape following the picking object 50 when a magnetic field is applied, and it is not required to have a specific composition. An electromagnet (not shown) for applying a magnetic field to this MR fluid is provided in the hand portion 20.

[0022] The bag body 22 can adopt various shapes as long as it can be deformed following the picking object. In the example of FIG. 2, the bag body 22 has a substantially rectangular parallelepiped shape. As another example, it can be configured to have a substantially cylindrical shape and bring the surface corresponding to the bottom surface of the cylinder into contact with the picking object 50.

[0023] In addition, a strain gauge 23 is provided on the bag body 22. The strain gauge 23 is preferably installed at a location on the bag body 22 that does not directly contact the picking object. In the example of FIG. 2, the strain gauge 23 is provided on a side surface different from the surface that contacts the picking object in the substantially rectangular parallelepiped-shaped bag body 22. Note that a wiring cable 25 is connected near the tip of the finger 21 in order to pass an electric current through the electromagnet and measure the amount of strain in the strain gauge 23 by the change amount of the voltage value.

[0024] The hand unit 20 may adopt any driving mechanism as long as it can execute an operation of gripping an object to be picked up by a plurality of fingers. In the example of FIG. 2, an electric cylinder 24 is adopted as the driving mechanism, and a driving mechanism is provided in which two fingers 21 open and close in conjunction with the extension and contraction of the electric cylinder 24.

[0025] FIG. 3 is a perspective view showing an example of another configuration of the hand unit of the picking robot corresponding to the embodiment of the present invention. This FIG. 3 shows a state in which a camera device 30 as a position specifying means 30 is installed with respect to the hand unit 20 shown in FIG. 2. In the example of FIG. 3, the camera device 30 is installed near the base of the finger 21 and at the end of the electric cylinder. By installing the camera device 30 at this position, if the object 50 to be picked up can be placed within the imaging range of the camera device 30, it is possible to always maintain the state in which the object 50 to be picked up is within the imaging range even during subsequent picking control. Therefore, it becomes possible to always grasp the positional relationship between the finger 21 of the hand unit 20 and the object 50 to be picked up. The camera device 30 may be a 2D camera, a 3D camera, or a TOF camera. Further, as shown in FIG. 3, the position specifying means 30 may be provided in the vicinity of the hand unit 20, or the position specifying means 30 may be provided at a position independent of the hand unit 20 as in the example shown in FIG. 1, or these may be used in combination.

[0026] FIG. 4 is an explanatory diagram for explaining the gripping operation of the hand part of the picking robot corresponding to the embodiment of the present invention. As shown in this FIG. 4, the hand part 20 in this example is provided with an L-shaped part 26 that functions like a joint that can move within a certain range at the tip of the finger 21. A box body for storing an electromagnet, a wiring cable, etc. is connected to this L-shaped part 26. Further, a bag body 22 that functions as the tip of the finger 21 is provided on one surface of the box body. In addition, a U-shaped part 27 for controlling the movement of the L-shaped part 26 as a joint is provided at the joint portion where the L-shaped part 26 is connected. This FIG. 4 shows a state where the two fingers 21 of the hand part 20 are open. Regarding the movement of opening this finger, when the electric cylinder descends, the base portion of the finger 21 is pushed downward. At that time, by connecting a fulcrum part 28 to a portion in the middle of the finger 21 and fixing it at a position not affected by the vertical movement of the electric cylinder, since the fulcrum part 28 becomes a fulcrum, the tip portion of the finger 21 is pushed upward.

[0027] FIG. 5 is an explanatory diagram for explaining the gripping operation of the hand part of the picking robot corresponding to the embodiment of the present invention. In this example, a link mechanism is adopted so that the contact surface of the bag body 22 having a substantially rectangular parallelepiped shape at the tip with respect to the picking object 50 is always maintained substantially parallel. Specifically, the other end of the U-shaped part 27 is connected to the intersection point of the turning radius A of the U-shaped part 27 and the turning radius B of the L-shaped part 26. By adopting such a configuration, even if the two fingers 21 are closed, the posture of the bag body 22 having a substantially rectangular parallelepiped shape can be always maintained in the same state. That is, it becomes possible to always maintain the contact surface of the bag body 22 with respect to the picking object 50 substantially parallel.

[0028] Note that by setting the state where two fingers are completely closed as shown in Fig. 5 as the position of 0 in the control range of the electric cylinder, if something is pinched, a displacement will appear by the amount of deformation, and it becomes possible to detect it. More specifically, when the shape and size of the picking object 50 are determined, it is also conceivable to set how much the picking object 50 is to be bitten into and control the gripping operation. For example, in a situation where the outer dimension L of the picking object 50 is known, if it is desired to control the movement to the position of the work dimension L-α (α is the amount of biting in) considering the allowance, the amount of biting into each of the two bag bodies 22 is α / 2. Control may be performed based on the amount of biting in estimated from the observation by the captured image, the amount of strain measured by the strain gauge 23, etc. Further, even in a situation where the shape and size of the picking object 50 cannot be grasped in advance, it is also possible to estimate the shape and size L and the center of gravity position of the picking object 50 from the captured image, set L-α as the target distance for control, and execute the gripping operation. When it is desired to perform control based on the distance during gripping, an electric cylinder for which the zero position can be easily set is suitable.

[0029] Fig. 6 is an explanatory diagram for explaining an outline of measurement of the amount of strain using a strain gauge in a picking device corresponding to an embodiment of the present invention. In this example, the case where a strain gauge 23 that detects the generated strain as a change in resistance value is adopted is described as an example. In order to detect the change in resistance value generated by the strain gauge 23 with high sensitivity, as shown in Fig. 6, it is preferable to detect it as a change in voltage value by a Wheatstone bridge circuit. As shown in Fig. 6, the strain ε generated in the strain gauge 23 appears as a displacement ΔL of the length L of the internal resistance, and this can be detected as a change amount ΔR of the gauge resistance R. If the gauge factor of the strain gauge 23 is K, the strain ε = ΔL / L = (ΔR / R) / K can be expressed. In the Wheatstone bridge circuit, the output voltage e, the input voltage E, the resistance value R of the strain gauge 23 1 , the resistance value R of the fixed resistance 2 ~R 4 are used, then e = {(R 1 R 2 -R 3R 4 )×E} / {(R 1 +R 2 )×(R 3 +R 4 )} can be expressed as follows. That is, the change amount of R can be calculated from the change amount of the output voltage e, and the strain amount ε can be measured from the change amount of R. 1 The strain amount measured by the strain gauge 23 can be used to estimate the gripping strength when gripping the picking object 50. If an appropriate gripping strength is set for each picking object 50, corresponding control can be performed. Also, the strain amount measured by the strain gauge 23 can be used to determine whether the picking object 50 is being properly gripped. When the picking object 50 is being properly gripped, strain can always be detected, but when the picking object 50 is missed, strain cannot be detected. Utilizing this, when strain cannot be detected despite performing the gripping operation, it may be determined that the attempt to grip the picking object 50 has failed, and a re-gripping operation may be executed. 1

[0030]

[0031] FIG. 7 is a flowchart showing the flow of the picking process executed in the control unit of the picking device corresponding to the embodiment of the present invention. As shown in this FIG. 7, the picking process is started in the control unit 40 by specifying the position of the object to be picked 50 (step S101). Next, the control unit 40 controls the picking robot 10 so as to execute an operation of gripping the object to be picked 50 with a plurality of fingers 21 of the hand unit 20 (step S102). When gripping, the gripping operation is executed so that the bag body 22 at the tip of the finger 21 abuts against the object to be picked 50. Next, the control unit 40 adjusts the gripping strength based on the amount of strain measured by the strain gauge 23 installed in the bag body 22 (step S103). Also, when the amount of strain is measured to be only below a predetermined threshold value, it may be determined that the object to be picked 50 is not grasped well, and the gripping operation may be executed again. Next, the control unit 40 applies a magnetic field to the MR fluid inside the bag body 22 to cure the MR fluid (step S104). Then, the control unit 40 performs control to move the object to be picked 50 while gripping the object to be picked 50 (step S105), and ends the picking process. Note that this flowchart is merely an example of control and is not limited to the processing of FIG. 4.

[0032] As described above, according to the multi-fingered hand for a robot according to the present invention, there are provided a plurality of fingers for grasping an object to be picked, a drive mechanism for driving the plurality of fingers, a bag provided at the tip portion of each of the plurality of fingers, having a hollow portion inside and having flexibility that can be deformed following the object to be picked, an MR fluid enclosed in the hollow portion of the bag, an electromagnet for applying a magnetic field to the MR fluid, and a strain gauge installed at a location on the bag that does not directly contact the object to be picked and for measuring the amount of strain of the bag. Therefore, when grasping the object to be picked with the plurality of fingers, since a magnetic field is not applied to the MR fluid before that, the bag deforms flexibly following the object to be picked, creating a state of close contact with various objects. Also, by measuring the amount of strain of the bag with the strain gauge installed on the bag, the grasping strength can be estimated and adjusted to an appropriate grasping strength for the object to be picked. When a magnetic field is applied to the MR fluid after adjusting the grasping strength, the MR fluid hardens while the bag is in close contact with the object to be picked, and the close contact state is maintained. As a result, by the bag deforming following the object to be picked, it becomes possible to appropriately grasp various objects regardless of differences in size or weight, and it also becomes possible to provide a multi-fingered hand for a robot capable of appropriately setting the grasping strength.

Explanation of Signs

[0033] 100 Picking device 10 Picking robot 20 Hand part 21 Finger 22 Bag 23 Strain gauge 24 Electric cylinder (drive mechanism) 25 Wiring cable 26 L-shaped part 27 U-shaped part 28 Fulcrum part 30 Position specifying means 40 Control unit 50 Object to be picked

Claims

1. A multi-fingered hand for a robot, which is connected to and used with a picking robot for picking a picking object, a plurality of fingers for grasping the picking object, a drive mechanism for driving the plurality of fingers, a flexible bag provided at the tip portion of each of the plurality of fingers, having a hollow portion inside and being deformable following the picking object, MR fluid enclosed in the hollow portion of the bag, an electromagnet for applying a magnetic field to the MR fluid, a strain gauge installed at a location on the bag that does not directly contact the picking object, for measuring the strain amount of the bag and comprising a multi-fingered hand for a robot.

2. The plurality of fingers are two, and each finger has at least one or more joints, the bag is generally rectangular parallelepiped in shape, the drive mechanism employs a link mechanism for always maintaining the contact surface of the generally rectangular parallelepiped-shaped bag at the tip with respect to the picking object in a generally parallel manner even when the two fingers are opened and closed The multi-fingered hand for a robot according to Claim 1.

3. A picking robot comprising the multi-fingered hand for a robot according to Claim 1 or Claim 2.

4. A picking device comprising a picking robot having a hand portion for picking a picking object, a position specifying means for specifying the position of the picking object, and a control unit for controlling the picking operation of the picking robot, wherein the hand portion comprises a plurality of fingers for grasping the picking object, a drive mechanism for driving the plurality of fingers, a flexible bag provided at the tip portion of each of the plurality of fingers, having a hollow portion inside and being deformable following the picking object, MR fluid enclosed in the hollow portion of the bag, an electromagnet for applying a magnetic field to the MR fluid, a strain gauge installed at a location on the bag that does not directly contact the picking object, for measuring the strain amount of the bag and comprising, wherein the control unit has a position specifying procedure for specifying the position of the picking object based on the position specifying means, a grasping procedure for grasping the specified picking object with the plurality of fingers of the hand portion, a grasping strength adjustment procedure for adjusting the grasping strength based on the strain amount of the bag measured by the strain gauge, and a curing procedure for applying a magnetic field to the MR fluid by the electromagnet to cure it A moving procedure for moving the object to be picked to a target position and A function for executing A picking device characterized by this.

Images