Control method and control device for gripping device

Abstract

Provided is a control method for a gripping device which is equipped with a gripping part for gripping an object to be gripped, using at least two gripping surfaces. The control method includes: a first step for changing the gap between the at least two gripping surfaces on the basis of the width of the object to be gripped; a second step for bringing the gripping part closer to the object to be gripped while maintaining the gap between the at least two gripping surfaces; and a third step for driving a belt that includes at least one gripping surface from between the at least two gripping surfaces.

Description

Grip device control method and control device

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

[0002] In recent years, automation of manufacturing processes has been required in various fields. To automate manufacturing processes, tools for holding objects such as parts used in the manufacturing process are required.

[0003] Patent Document 1 discloses a gripping device including a drive means, a base, and a finger mechanism. The finger mechanism includes a drive wheel, a driven wheel, and an endless belt. When an object is sandwiched between the multiple finger mechanisms, the drive wheel rotates, and the endless belt also rotates, so that the object is pulled between the multiple finger mechanisms.

[0004] JP 2016-30316 A

[0005] However, with the technology of Patent Document 1, when the objects to be grasped are crowded and close together, the objects to be grasped and the tip of the grasping device interfere with each other, making it difficult for the grasping device to grasp the objects to be grasped.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a control method and a control device for a gripping device that can easily grip objects even when the objects are densely packed together.

[0007] For this reason, one aspect of the method for controlling a gripping device according to the present disclosure is a method for controlling a gripping device having a gripping unit that grips an object with at least two gripping surfaces, and includes a first step of changing the spacing between the at least two gripping surfaces based on the width of the object, a second step of bringing the gripping unit closer to the object while maintaining the spacing between the at least two gripping surfaces, and a third step of driving a belt having at least one of the at least two gripping surfaces.

[0008] Furthermore, one aspect of the control device according to the present disclosure includes a gripping unit that grips an object with at least two gripping surfaces, and a control unit that changes the spacing between the at least two gripping surfaces based on the width of the object, brings the gripping unit closer to the object while maintaining the spacing between the at least two gripping surfaces, and drives a belt having at least one of the at least two gripping surfaces.

[0009] According to the present disclosure, objects to be held can be easily held even when the objects are crowded together.

[0010] It is a figure which shows an example of a gripping device. It is a figure which shows an example of a control part of the gripping device. It is a figure which shows an example of an operation of the gripping device. It is a figure which shows another operation of the gripping device.

[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 and connection of each component, and each step and the order of each step 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 an example of a gripping device 1. The gripping device 1 includes a gripping unit 2, an opening / closing unit 3, and a holding unit 4.

[0014] The gripping unit 2 shown in Fig. 1 has two fingers. Each finger includes a plate-like member 11, a belt 13 that covers the plate-like member 11 and whose outer surface serves as a gripping surface 12 for gripping an object, a belt drive unit 14 that rotates the belt 13, and a force detection unit 15 that detects the force applied to the gripping surface 12. Note that although the present embodiment discloses a case in which there are two fingers, there may be three or more fingers.

[0015] The belt driving unit 14 includes a motor and a reducer for driving the belt 13, and an encoder for detecting the rotation angle of the motor.

[0016] The opening / closing unit 3 controls the distance between the gripping surfaces 12 of the two fingers. The opening / closing unit 3 includes a motor 21, a reducer, an encoder that detects the motor rotation angle, and a translation mechanism 22 driven by the motor 21.

[0017] The translation mechanism 22 includes force transmission parts such as a trapezoidal screw, a sliding screw, a timing belt, a worm gear, etc., and linear motion parts such as a slider rail, etc. Note that the translation mechanism 22 is not limited to these parts, and may also be a mechanism using a link, a cam, a gear, a belt, etc.

[0018] The gripping device 1 can pinch and grip an object by narrowing the distance between two or more gripping surfaces 12. Furthermore, the gripping device 1 can move the position of the object by rotating the belt 13 while the object is pinched.

[0019] The force detection unit 15 is a film-like pressure-sensitive sensor and is provided on the surface of the plate-like member 11. Note that the force detection unit 15 may be a sensor that detects a force other than a pressure-sensitive sensor. For example, the force detection unit 15 may be a sensor that detects a force such as a strain sensor or a distance measurement sensor. Furthermore, the force detection unit 15 may be a sensor that detects a force applied to the grip surface 12 by detecting a current flowing through a motor 21 provided in the opening / closing unit 3.

[0020] The gripping device 1 has a holding part 4 on the upper surface of the opening / closing part 3, and is attached to a robot arm or the like via the holding part 4. The position and posture of the gripping device 1 are changed by the operation of the robot arm or the like.

[0021] The gripping device 1 also has a control unit 41, which will be described later, and controls the driving of the motors of the opening / closing unit 3 and the belt drive unit 14 based on control commands from outside, input signals from the encoders of the opening / closing unit 3 and the belt drive unit 14, and input signals from the force detection unit 15.

[0022] 2 is a diagram showing an example of the control unit 41 of the gripping device 1. The control unit 41 is connected to the motors 21 and 45, the encoders 44 and 46, and the force detection unit 15. Here, the motor 21 and the encoder 44 are provided in the opening / closing unit 3, and the motor 45 and the encoder 46 are provided in the belt driving unit 14. The encoders 44 and 46 detect the rotation angles of the motors 21 and 45.

[0023] The control unit 41 includes a control calculation unit 42 and a motor control unit 43. The control calculation unit 42 outputs a motor control signal to the motor control unit 43 based on a control command input from the outside, input signals from the encoders 44 and 46, and an input signal from the force detection unit 15.

[0024] The motor control unit 43 outputs a motor drive current to the motors 21 and 45 based on the motor control signal.

[0025] For example, the control calculation unit 42 sets a target gripping force based on a control command input from an external device. The target gripping force is set in advance depending on the hardness and weight of the object to be gripped. The control calculation unit 42 calculates the difference between the target gripping force and the current gripping force, and outputs a motor control signal to the motor control unit 43 to make the difference zero.

[0026] The control calculation unit 42 performs the above calculations using the control law of PID control. The motor control signal includes information such as the motor speed, torque, and rotation angle. The motor control unit 43 receives the motor control signal and drives the motor 21 of the opening / closing unit 3 by outputting a motor drive current to the motor 21.

[0027] Next, a description will be given of a method for controlling the gripping device 1. FIG.

[0028] First, the control unit 41 of the gripping device 1 changes the distance between the two gripping surfaces 12 to a distance based on the widths of the objects 31, 32. Information about the widths of the objects 31, 32 may be stored in advance in the storage unit, or the gripping device 1 may receive input of this information from the user.

[0029] For example, the distance between the two gripping surfaces 12 is equal to the width of the objects 31 and 32 to be gripped, or is smaller than the width of the objects 31 and 32. Note that this distance may also be slightly larger than the width of the objects 31 and 32 to be gripped.

[0030] Next, the control unit 41 controls the gripping unit 2 to move the gripping unit 2 closer to the object 31 while maintaining the distance between the two gripping surfaces 12 .

[0031] In this way, by changing the distance between the two gripping surfaces 12 based on the width of the object 31 and then bringing the gripping portion 2 closer to the object 31, the object 31 can be easily gripped even when the objects 31 are crowded together.

[0032] Here, the control unit 41 drives the belt 13 to rotate when the object 31 comes into contact with the belt 13 having at least one of the two gripping surfaces 12, as shown by the arrow in Figure 3.

[0033] Alternatively, the control unit 41 may rotate the belt 13 having at least one of the two gripping surfaces 12 before the object 31 comes into contact with the belt 13 .

[0034] At this time, the control unit 41 can move the object to be held 31 into the inside of the holding unit 2 by rotating the belt 13 in a direction in which the object to be held 31 moves between the two opposing holding surfaces 12, and the holding device 1 can easily hold the object to be held 31.

[0035] As described above, while gripping the object 31, the force detection unit 15 detects the force applied to at least one gripping surface 12. The control unit 41 then controls the distance between the two gripping surfaces 12 so that the detected force becomes the target gripping force. This allows the object 31 to be moved stably by the belt 13.

[0036] Here, the force detection unit 15 is configured to detect a force applied to at least one gripping surface 12, but it may also detect other forces applied to the gripping unit 2, such as a resistance force applied to the belt moving unit 14.

[0037] In addition, the force detection unit 15 may always detect the force applied to the gripping unit 2, but it may also start detecting the force applied to the gripping unit 2 when the gripped object 31 comes into contact with at least one gripping surface 12, thereby avoiding unnecessary detection.

[0038] Here, if the size of the object 31 to be gripped is constant, the object 31 can be moved by the belt 13 simply by adjusting the gap between the two gripping surfaces 12 to fit the object 31 and rotating the belt 13. In this case, the control unit 41 drives the motor 45 of the belt drive unit 14, and the encoder 46 detects the motor rotation angle.

[0039] However, if there is variation in the size of the object 31 to be gripped, simply adjusting the distance between the two gripping surfaces 12 to fit the object 31 and rotating the belt 13 may result in the distance being too small or too large for the object 31, making it impossible to move the object 31 stably.

[0040] Even in such a case, the control unit 41 controls the gripping force to a constant value as described above, thereby appropriately adjusting the distance between the two gripping surfaces 12, and the object 31 can be moved stably by the belt 13.

[0041] Although at least the tip of the material constituting the plate-shaped member 11 may be made of a metal material such as aluminum, a flexible and deformable material such as resin is more preferable. For example, a fiber-reinforced engineering plastic (POM, PPS, etc.) is suitable for this material. Alternatively, this material may be a resin-metal composite material.

[0042] The objects 31 to be grasped may include objects whose placement position or size differs from what was expected. For example, if the size of the object 31 is larger than expected, even if an attempt is made to grasp the object using the above-described operation of the grasping device 1, the gap between the two grasping surfaces 12 is small, and therefore grasping may fail.

[0043] However, in the case of a flexible plate-like member 11, when the gripping portion 2 is pressed against the object to be gripped 31 and the belt 13 is rotated, the plate-like member 11 and the belt 13 are deformed, so that the object to be gripped 31 can be accommodated in the area between the two gripping surfaces 12.

[0044] Furthermore, the control unit 41 controls the gripping force to be constant, so that the distance between the two gripping surfaces 12 is adapted to the size of the object 31 to be gripped, and the object 31 can be moved by the belt 13 .

[0045] 4 is a diagram showing the operation of the gripping device 1 in this case. First, the gripping device 1 brings the gripping unit 2 close to the object 51. In this example, the size of the object 51 is larger than expected, and the distance between the two gripping surfaces 12 does not match the size of the object 51.

[0046] In the example of FIG. 4, the object 51 comes into contact with two belts 13 at almost the same time, and the control unit 41 rotates the two belts 13 that are in contact with the object 51 .

[0047] Since not only the belt 13 but also the plate-shaped member 11 is made of a flexible material, when the gripping portion 2 is pressed against the object to be gripped 51, the rotation of the belt 13 causes the plate-shaped member 11 and the belt 13 to deform, and the object to be gripped 51 can be accommodated in the area between the two gripping surfaces 12.

[0048] Furthermore, since the control unit 41 controls the gripping force of the gripping unit 2 to be constant, the distance between the two gripping surfaces 12 can be adapted to the size of the object 51 to be gripped.

[0049] In the above-described embodiments, 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.

[0050] 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.

[0051] The present disclosure can be used in a gripping device that changes the posture of a gripped object.

[0052] REFERENCE SIGNS LIST 1 gripping device 2 gripping section 3 opening / closing section 4 holding section 11 plate-like member 12 gripping surface 13 belt 14 belt driving section 15 force detection section 21 motor 22 translation mechanism 31 gripped object 41 control section 42 control calculation section 43 motor control section 44 encoder

Claims

1. A method for controlling a gripping device equipped with a gripping unit that grips an object with at least two gripping surfaces, the method comprising: a first step of changing the distance between the at least two gripping surfaces based on the width of the object; a second step of moving the gripping unit toward the object while maintaining the distance between the at least two gripping surfaces; and a third step of driving a belt having at least one of the at least two gripping surfaces.

2. A method for controlling a gripping device as described in claim 1, wherein in the third step, the belt having at least one gripping surface of the at least two gripping surfaces is driven when the object to be gripped comes into contact with the belt having the at least one gripping surface.

3. A method for controlling a gripping device as described in claim 1, wherein in the third step, a belt having at least one gripping surface of the at least two gripping surfaces is driven before the object to be gripped comes into contact with the belt having the at least one gripping surface.

4. A method for controlling a gripping device according to claim 1, wherein in the first step, the interval is changed to an interval equal to the width of the object to be gripped.

5. A method for controlling a gripping device according to claim 1, wherein in the first step, the interval is changed to an interval smaller than the width of the object to be gripped.

6. The method for controlling a gripping device according to claim 1, wherein in the third step, the belt is driven in a direction in which the object to be gripped moves between the at least two gripping surfaces.

7. A method for controlling a gripping device as described in claim 1, further comprising a fourth step of detecting a force applied to the gripping portion and controlling the distance between the at least two gripping surfaces so that the detected force becomes a predetermined force.

8. The method for controlling a gripping device according to claim 7, wherein the force applied to the gripping portion is a force applied to the at least one gripping surface.

9. A method for controlling a gripping device as described in claim 7, wherein in the fourth step, detection of the force applied to the gripping portion is started at the timing when the object to be gripped comes into contact with at least one of the gripping surfaces.

10. A method for controlling a gripping device according to claim 1, wherein the tip of the gripping part that comes into contact with the object to be gripped is deformable.

11. A control device comprising: a gripping unit that grips an object with at least two gripping surfaces; and a control unit that changes the distance between the at least two gripping surfaces based on the width of the object, moves the gripping unit closer to the object while maintaining the distance between the at least two gripping surfaces, and drives a belt having at least one of the at least two gripping surfaces.

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