Gripping device and gripping method

Abstract

This gripping device comprises: a gripping part having at least two gripping surfaces for gripping a grip object, the gripping part moving the gripping surfaces relative to each other to change the orientation of the grip object; and a holding part that holds the gripping part and changes the orientation of the gripping part. The gripping part changes the orientation of the grip object in a gripping orientation in which the gripping surfaces are present vertically below at least one point of a contact location where the grip object comes into contact with the gripping surfaces.

Description

Gripping device and gripping method

[0001] The present disclosure relates to a gripping device and a gripping method.

[0002] In recent years, automation of manufacturing processes has been required in various fields. To automate a manufacturing process, it is necessary to change the posture of an object, such as a part, used in the manufacturing process to a desired posture.

[0003] Patent Document 1 discloses a technique for changing the posture of a workpiece to be handled by using an auxiliary device that bears the load resulting from the weight of the workpiece.

[0004] Patent No. 3830477

[0005] However, the technique of Patent Document 1 has a problem in that it requires an auxiliary device to change the posture of the workpiece.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a gripping device that can easily change the posture of an object to be gripped.

[0007] For this purpose, one aspect of the gripping device according to the present disclosure comprises a gripping unit having at least two gripping surfaces for gripping an object to be gripped, and changing the posture of the object to be gripped by moving the gripping surfaces relative to each other, and a holding unit that holds the gripping unit and changes the posture of the gripping unit, wherein the gripping unit changes the posture of the object to be gripped in a gripping posture in which the gripping surface is located vertically below at least one contact point where the object to be gripped comes into contact with the gripping surface.

[0008] Furthermore, one aspect of the gripping method according to the present disclosure includes a first step in which a holding unit holds a gripping unit having at least two gripping surfaces for gripping an object to be gripped, and changes the posture of the gripping unit; and a second step in which the gripping unit changes the posture of the object to be gripped by moving the gripping surfaces relative to each other, wherein in the second step, the gripping unit changes the posture of the object to a gripping posture in which the gripping surface is located vertically below at least one contact point where the object comes into contact with the gripping surface.

[0009] According to the present disclosure, the posture of an object to be held can be easily changed.

[0010] 1 is a diagram showing a gripping device; FIG. 2 is an enlarged view showing a gripping section; FIG. 3 is a diagram showing the operation of the gripping device; FIG. 4 is a diagram showing the operation of the gripping device; FIG. 5 is a diagram showing a gripping device equipped with a detection section; FIG. 6 is a diagram showing the operation of the gripping device; and FIG. 7 is an enlarged view showing the operation of the gripping section.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the components, the arrangement positions and connection forms of the components, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims will be described as optional components.

[0012] Furthermore, each drawing is a schematic diagram and is not necessarily an exact illustration. In each drawing, substantially the same components are denoted by the same reference numerals, and redundant explanations will be omitted or simplified.

[0013] 1 is a diagram showing a gripping device 1. The gripping device 1 includes a gripping portion 2, a flange portion 3, and a holding portion 4. The holding portion 4 includes a main body 5, links 6a to 6c, and joint shaft motors 7a and 7b.

[0014] 2 is an enlarged view showing the gripping unit 2. The gripping unit 2 includes gripping fingers 11, a belt 12, a belt drive motor 13, and gripping surfaces 14a and 14b. The spacing between the gripping fingers 11 is controlled by an opening / closing unit.

[0015] The opening / closing section includes a guide rail 15, an opening / closing motor 16, an encoder, and a reducer. The driving force of the opening / closing motor 16 moves the gripping fingers 11 between the guide rails 15 via a timing belt, pulleys, etc.

[0016] A belt 12 is installed along the surface of the gripping fingers 11, and gripping surfaces 14a and 14b that grip an object are the outer surfaces of the belt. By rotating a belt drive motor 13, the belt 12 can move along the surface of the gripping fingers 11 via a reducer, a timing belt, pulleys, etc. A belt drive motor 13 is provided for each gripping finger 11, and by independently controlling each belt 12, the gripping surfaces 11 can move relative to each other.

[0017] The holding unit 4 holds the gripping unit 2 and fixes it in a predetermined position and posture. Like a robot arm, the holding unit 4 has a link structure with multiple joints, and joint shaft motors 7a, 7b are installed in each of the links 6a to 6c. By rotating these joint shaft motors 7a, 7b, the gripping device 1 can control the position and posture of the tip of the link 6. The gripping unit 2 is attached to a flange portion 3 at the tip of the link 6a. By using a structure with six or more axes, the holding unit 4 can hold the gripping unit 2 in any position and posture.

[0018] The control unit is installed inside the main body 5 and is configured with a microcomputer or a PC. Note that the control unit is not limited to being installed in the main body 5, and may be installed inside the links 6a to 6c.

[0019] The gripping unit 2 controls the distance between the gripping surfaces 14a, 14b and the relative positions of the gripping surfaces 14a, 14b by the opening / closing motor 16 and the belt drive motor 13. By controlling the gripping unit 2 in this way, the following operations can be performed.

[0020] 1. The gripping fingers 11 are opened and closed by the opening / closing motor 16, allowing the gripping unit 2 to grip and release an object.

[0021] 2. With an object being gripped, by rotating one of the belts 12 in the opposite direction to the other (the gripping surfaces 14a, 14b move in the same direction relative to each other), the position of the gripped object within the hand, which has two gripping fingers 11, can be moved.

[0022] 3. With an object being gripped, by rotating only one of the belts 12, or by rotating one of the belts 12 in the same direction as the other (the gripping surfaces 14a, 14b move in opposite directions relative to each other), the gripped object can be rotated within the hand and its posture can be changed.

[0023] During the above operations 2 and 3, the control unit can control the amount of movement and rotation based on the value of the encoder connected to the belt drive motor 13.

[0024] For the holding unit 4, the control unit controls each of the joint axis motors 7a, 7b to set the position and orientation of the gripping unit 2 installed at the tip to a predetermined state. The position and orientation of the tip of the link 6a can be determined by forward kinematics from the length of each of the links 6a to 6c and the angle of each axis (values ​​of the encoders connected to each of the joint axis motors 7a, 7b). Furthermore, the angle of each axis that results in the position and orientation of the tip of a predetermined link 6a to 6c can be calculated by inverse kinematics.

[0025] Next, a description will be given of the operation of the gripping device 1. Fig. 3 is a diagram showing the operation of the gripping device 1. First, the gripping device 1 grips the object 21 with the gripping section 2.

[0026] Next, the holding unit 4 tilts the gripping unit 2 at a predetermined angle (for example, 45 degrees relative to the horizontal plane). This angle may be any angle that allows the gripping surfaces 14 a, 14 b to be located vertically below at least one point where the object 21 comes into contact with the gripping surfaces 14 a, 14 b.

[0027] For example, in the left diagram of Fig. 3, the gripping surfaces 14a and 14b are not located vertically below the contact points where the object 21 contacts the gripping surfaces 14a and 14b, but in the center diagram of Fig. 3, the gripping surface 14b is located vertically below at least one point where the object 21 contacts the gripping surfaces 14b. Therefore, the control unit of the gripping device 1 tilts the gripping unit 2 to the angle shown in the center diagram.

[0028] Here, the control unit may control the angle at which the gripping unit 2 is tilted based on the values ​​of the encoders connected to each joint axis motor 7a, 7b, or may control the angle at which the gripping unit 2 is tilted by determining whether the above-mentioned angle has been reached from an image taken by an external camera that observes the gripping state.

[0029] Thereafter, the control unit rotates the belts 12 of the two gripping units 2 in relatively opposite directions so that the gripped object 21 assumes the desired posture. The amount of rotation of the belts 12 required to assume the desired posture of the gripped object 21 is determined in advance by an experiment or the like.

[0030] As shown in the central diagram of Figure 3, if the gripping surface 14b is present vertically below at least one point of contact where the object to be gripped 21 comes into contact with the gripping surface 14b, the frictional force that the object to be gripped 21 receives from the gripping surface 14b will prevent the object to be gripped 21 from falling off the gripping portion 2, or will make it less likely to fall off.

[0031] If the object 21 to be held does not fall from the holding parts 2, the position of the object 21 to be held can be easily changed by rotating the belts 12 while the object 21 is held between the belts 12 of the two holding parts 2.

[0032] Furthermore, even if the object 21 slides down the belt 12 toward the tip of the gripping fingers 11 of the gripping unit 2, the speed at which the object slides down is small due to frictional force, so the posture of the object 21 can be easily changed before the object 21 falls from the gripping unit 2.

[0033] In this way, with this gripping device 1, the posture of the object to be gripped 21 can be easily changed without using an auxiliary device for changing the posture of the workpiece.

[0034] (Embodiment 2) Next, the operation of the gripping device 1 according to embodiment 2 will be described. Fig. 4 is a diagram showing the operation of the gripping device 1. First, the gripping device 1 grips the object 21 with the gripping unit 2. Then, the holding unit 4 tilts the gripping unit 2 at a predetermined angle. In the example of Fig. 4, the gripping unit 2 is tilted 45 degrees, and the object 21 is gripped by the tips of the gripping fingers 11.

[0035] Next, the control unit controls the gripping surfaces 14a, 14b to move relatively in the same direction (towards the bases of the gripping fingers 11), thereby moving the position of the object 21 within the hand having the two gripping fingers 11 by a predetermined amount. This amount of movement may be any amount that allows the gripping surfaces 14a, 14b to be located vertically below at least one point of contact between the object 21 and the gripping surfaces 14a, 14b.

[0036] This amount of movement may be a preset amount to achieve this state, or the control unit may control the amount of movement by determining whether the above-mentioned state has been achieved from images taken by an external camera observing the gripping state.

[0037] Thereafter, the control unit rotates the belt 12 of the gripping unit 2 in the relatively opposite direction so that the gripped object 21 assumes the desired position. The amount of rotation of the belt 12 required to assume the desired position of the gripped object 21 is determined in advance through experiments, etc. By changing the position after the gripped object 21 has been sufficiently pulled into the hand, a stable position change can be achieved without the risk of the gripped object 21 dropping.

[0038] (Embodiment 3) Next, the operation of the gripping device 1 according to embodiment 3 will be described. First, the gripping device 1 grips the object 21 with the gripping unit 2. Then, the holding unit 4 tilts the gripping unit 2 at a predetermined angle. For example, the gripping unit 2 is tilted 45 degrees, and the object 21 is gripped by the tips of the gripping fingers 11.

[0039] Next, the control unit controls the gripping surfaces 14a and 14b to move relatively in the same direction (towards the base of the gripping fingers 11), thereby moving the gripped object 21 until the gripping surfaces 14a and 14b are located vertically below the center of gravity of the gripped object 21.

[0040] This amount of movement may be a preset amount to achieve this state, or the control unit may control the amount of movement by determining whether the above-mentioned state has been achieved from images taken by an external camera observing the gripping state.

[0041] Thereafter, the control unit rotates the belt 12 of the gripping unit 2 in the relatively reverse direction so that the gripped object 21 assumes the desired posture. The amount of rotation of the belt 12 required to assume the desired posture of the gripped object 21 is determined in advance by an experiment or the like.

[0042] If the gripping surfaces 14a and 14b are present vertically below the center of gravity of the object 21, the object 21 is less likely to fall from the gripping unit 2. Therefore, the position of the object 21 can be changed more stably.

[0043] (Embodiment 4) Next, an operation of the gripping device 1 according to embodiment 4 will be described. Fig. 5 is a diagram showing the gripping device 1 equipped with a detection unit 31. Embodiment 4 differs from embodiment 1 in that the detection unit 31 is installed in the gripping device 1.

[0044] The detection unit 31 is installed between the gripping unit 2 and the holding unit 4, and measures the weight of the gripping unit 2 and the gripped object 21 using a load cell. The detection unit 31 can measure the weight of the gripped object 21 by subtracting the weight of the gripping unit 2 from the measured weight. The weight data measured by the detection unit 31 is sent to the control unit.

[0045] In this case, first, the gripping device 1 grips the object 21 with the gripping portion 2 .

[0046] Next, the detection unit 31 detects the weight of the gripping unit 2 and the object 21 to be gripped, and measures the weight of the object 21 to be gripped by subtracting the weight of the gripping unit 2 from the detected weight.

[0047] Thereafter, the holding unit 4 tilts the gripping unit 2 based on the weight of the object 21. The angle at which the gripping unit 2 is tilted is the angle at which the gripping surfaces 14a, 14b are located vertically below at least one point of contact between the object 21 and the gripping surfaces 14a, 14b, and the heavier the object 21 is, the larger the angle at which the gripping unit 2 is tilted.

[0048] The control unit determines the tilt angle of the gripping unit 2 by referring to a correspondence table in which appropriate tilt angles of the gripping unit 2 for the weight of the object to be gripped 21 are registered. The appropriate angle varies depending on factors such as the coefficient of friction between the belt 12 and the object to be gripped 21, so the correspondence table is created in advance through experiments, etc.

[0049] Thereafter, the control unit rotates the belt 12 of the gripping unit 2 in the relatively opposite direction so that the gripped object 21 assumes the desired position. The amount of rotation of the belt 12 required to assume the desired position of the gripped object 21 is determined in advance through experiments, etc. This allows the position of the gripping object 21 to be changed to an appropriate position for the gripping unit 2 according to the weight of the gripped object 21.

[0050] (Embodiment 5) Next, the operation of the gripping device 1 according to embodiment 5 will be described. First, the gripping device 1 grips the object 21 with the gripping unit 2. Then, the holding unit 4 tilts the gripping unit 2 at a predetermined angle. For example, the gripping unit 2 is tilted 45 degrees, and the object 21 is gripped by the tips of the gripping fingers 11.

[0051] Next, the detection unit 31 detects the weight of the gripping unit 2 and the object 21 to be gripped, and measures the weight of the object 21 to be gripped by subtracting the weight of the gripping unit 2 from the detected weight.

[0052] The control unit then controls the gripping surfaces 14a and 14b to move relatively in the same direction (towards the base of the gripping fingers 11), thereby moving the position of the gripped object 21 within the hand equipped with the two gripping fingers 11 by a predetermined amount.

[0053] This amount of movement may be any amount that results in the gripping surfaces 14a, 14b being located vertically below at least one point of contact where the gripped object 21 comes into contact with the gripping surfaces 14a, 14b, and is set so that the amount of movement increases as the weight of the gripped object 21 increases.

[0054] In this case, the control unit determines the amount of movement of the object 21 by referring to a correspondence table in which appropriate amounts of movement of the object 21 relative to the weight of the object 21 are registered. Since the appropriate position of the object changes depending on factors such as the coefficient of friction between the belt 12 and the object 21, the correspondence table is created in advance through experiments, etc.

[0055] Thereafter, the control unit rotates the belt 12 of the gripping unit 2 in the relatively reverse direction so that the gripped object 21 assumes the desired posture. The amount of rotation of the belt 12 required to assume the desired posture of the gripped object 21 is determined in advance by an experiment or the like.

[0056] The heavier the object 21 is, the more likely it is that the object 21 will slide down the belt 12 toward the tip of the gripping fingers 11 of the gripping unit 2. However, the heavier the object 21 is, the more likely it is that the object 21 will be moved toward the base of the gripping fingers 11 before the position of the object 21 is changed, thereby making it possible to change the position of the object 21 before it falls from the gripping unit 2.

[0057] (Embodiment 6) Next, the operation of the gripping device 1 according to embodiment 6 will be described. Embodiment 6 differs from embodiment 1 in that a memory unit is installed in the gripping device 1. The memory unit stores the weight of each object 21 to be gripped. For example, the memory unit is a memory installed in the control unit, and data can be referenced from the control unit.

[0058] First, the gripping device 1 grips the object 21 with the gripping unit 2. Next, the control unit reads data on the weight of the object 21 from the memory unit. Thereafter, the holding unit 4 tilts the gripping unit 2 based on the weight of the object 21.

[0059] The angle at which the gripping portion 2 is tilted is the angle at which the gripping surfaces 14a, 14b are located vertically below at least one point of contact where the object to be gripped 21 comes into contact with the gripping surfaces 14a, 14b, and the heavier the object to be gripped 21 is, the larger the angle at which the gripping portion 2 is tilted.

[0060] The control unit determines the tilt angle of the gripping unit 2 by referring to a correspondence table in which appropriate tilt angles of the gripping unit 2 for the weight of the object to be gripped 21 are registered. The appropriate angle varies depending on factors such as the coefficient of friction between the belt 12 and the object to be gripped 21, so the correspondence table is created in advance through experiments, etc.

[0061] Thereafter, the control unit rotates the belt 12 of the gripping unit 2 in the relatively opposite direction so that the gripped object 21 assumes the desired position. The amount of rotation of the belt 12 required to assume the desired position of the gripped object 21 is determined in advance through experiments, etc. This allows the position of the gripping object 21 to be changed to an appropriate position for the gripping unit 2 according to the weight of the gripped object 21.

[0062] (Embodiment 7) Next, the operation of the gripping device 1 according to embodiment 7 will be described. First, the gripping device 1 grips the object 21 with the gripping unit 2. Then, the holding unit 4 tilts the gripping unit 2 at a predetermined angle. For example, the gripping unit 2 is tilted 45 degrees, and the object 21 is gripped by the tips of the gripping fingers 11.

[0063] Next, the control unit reads data on the weight of the object 21 from the memory unit. The memory unit stores the weight of each object 21. For example, the memory unit is a memory mounted in the control unit, and the data can be referenced from the control unit.

[0064] The control unit then controls the gripping surfaces 14a and 14b to move relatively in the same direction (towards the base of the gripping fingers 11), thereby moving the position of the gripped object 21 within the hand equipped with the two gripping fingers 11 by a predetermined amount.

[0065] This amount of movement may be any amount that results in the gripping surfaces 14a, 14b being located vertically below at least one point of contact where the gripped object 21 comes into contact with the gripping surfaces 14a, 14b, and is set so that the amount of movement increases as the weight of the gripped object 21 increases.

[0066] In this case, the control unit determines the amount of movement of the object 21 by referring to a correspondence table in which appropriate amounts of movement of the object 21 relative to the weight of the object 21 are registered. Since the appropriate position of the object changes depending on factors such as the coefficient of friction between the belt 12 and the object 21, the correspondence table is created in advance through experiments, etc.

[0067] Thereafter, the control unit rotates the belt 12 of the gripping unit 2 in the relative opposite direction so that the gripped object 21 assumes the desired position. The amount of rotation of the belt 12 required to assume the desired position of the gripped object 21 is determined in advance through experiments, etc. This allows the position of the gripped object 21 to be changed at an appropriate position of the gripping unit 2 according to the weight of the gripped object.

[0068] (Embodiment 8) Next, the operation of the gripping device 1 according to embodiment 8 will be described. Fig. 6 is a diagram showing the operation of the gripping device 1. Fig. 7 is an enlarged view showing the operation of the gripping unit 2. First, the gripping device 1 grips the object 21 with the gripping unit 2.

[0069] Next, the holding unit 4 tilts the gripping unit 2 at a predetermined angle (for example, 45 degrees relative to the horizontal plane). This angle may be any angle that allows the gripping surfaces 14 a, 14 b to be located vertically below at least one point where the object 21 comes into contact with the gripping surfaces 14 a, 14 b.

[0070] Here, the control unit may control the angle at which the gripping unit 2 is tilted based on the values ​​of the encoders connected to each joint axis motor 7a, 7b, or may control the angle at which the gripping unit 2 is tilted by determining whether the above-mentioned angle has been reached from an image taken by an external camera that observes the gripping state.

[0071] Thereafter, the control unit controls the holding unit 4 to linearly move the object 21 to an even higher position, while rotating the belt 12 of the holding unit 2 in the relatively opposite direction so that the object 21 assumes the desired position. The amount of rotation of the belt 12 required to position the object 21 in the desired position is determined by a value previously determined through an experiment or the like.

[0072] This causes the object 21 to be pressed against the gripping surface 14b, increasing the frictional force that the object 21 receives from the gripping surface 14b, making it more difficult for the object 21 to fall off the gripping unit 2. As a result, the position of the object 21 can be easily changed.

[0073] In the above-described embodiment, the functions of the control unit may be realized by executing a software program, i.e., the functions of the control unit may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0074] In addition, this disclosure also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art would think of, or forms realized by arbitrarily combining the components and functions of each embodiment within the scope that does not deviate from the intent of this disclosure.

[0075] The present disclosure can be used in a gripping device that changes the posture of a gripped object.

[0076] REFERENCE SIGNS LIST 1 Grip device 2 Grip portion 3 Flange portion 4 Holding portion 5 Main body 6 Link 7 Joint shaft motor 11 Grip finger 12 Belt 13 Belt drive motor 14 Grip surface 15 Guide rail 16 Opening / closing motor 21 Gripped object 31 Detection portion

Claims

1. A gripping device comprising: a gripping unit having at least two gripping surfaces for gripping an object to be gripped, and changing the posture of the object to be gripped by moving the gripping surfaces relative to each other; and a holding unit that holds the gripping unit and changes the posture of the gripping unit, wherein the gripping unit changes the posture of the object to be gripped in a gripping posture in which the gripping surface is located vertically below at least one contact point where the object to be gripped comes into contact with the gripping surface.

2. The gripping device according to claim 1, wherein the at least two gripping surfaces are surfaces of a moving belt, and the gripping unit moves the belt to move the gripping surfaces relative to each other.

3. The gripping device according to claim 2, wherein the gripping section changes the position of the object by rotating one of the at least two gripping surfaces that sandwich the object in a direction opposite to that of the other gripping surface.

4. The gripping device according to claim 2, wherein the gripping section changes the posture of the object by rotating one of the at least two gripping surfaces that sandwich the object, or by rotating one of the gripping surfaces in the same rotational direction as the other.

5. The gripping device according to claim 1, wherein the holding unit changes the posture of the gripping unit to the gripping posture, and the gripping unit changes the posture of the object being gripped after the posture of the gripping unit has become the gripping posture.

6. The gripping device according to claim 1, wherein the gripping unit changes the position of the object to assume the gripping posture, and after changing the position of the object, changes the posture of the object.

7. The gripping device according to claim 1, wherein the gripping unit changes the posture of the object to be gripped while the gripping surface is positioned vertically below the center of gravity of the object to be gripped.

8. The gripping device according to claim 1, further comprising a detection unit that detects the weight of the object to be gripped.

9. The gripping device according to claim 8, wherein the holding unit changes the attitude of the gripping unit based on the weight.

10. The gripping device according to claim 8, wherein the gripping unit changes the position of the object to be gripped based on the weight, and after changing the position of the object to be gripped, changes the attitude of the object to be gripped.

11. The gripping device according to claim 1, further comprising a storage unit for storing information on the weight of the object to be gripped in advance.

12. The gripping device according to claim 11, wherein the holding unit changes the attitude of the gripping unit based on the weight stored in the memory unit.

13. The gripping device according to claim 11, wherein the gripping unit changes the position of the gripped object based on the weight stored in the memory unit, and after changing the position of the gripped object, changes the attitude of the gripped object.

14. The gripping device according to claim 1, wherein the holding unit linearly moves the object gripped by the gripping unit from a first position to a second position higher than the first position.

15. The gripping device according to claim 14, wherein the gripping unit changes the posture of the object while linearly moving the object from the first position to the second position.

16. A gripping method comprising: a first step in which a holding unit holds a gripping unit having at least two gripping surfaces for gripping an object to be gripped, and changes the posture of the gripping unit; and a second step in which the gripping unit changes the posture of the object to be gripped by moving the gripping surfaces relatively to each other, wherein in the second step, the gripping unit changes the posture of the object to be gripped in a gripping posture in which the gripping surface is located vertically below at least one contact point where the object comes into contact with the gripping surface.

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