WO2020026830A1

WO2020026830A1 - Robot hand

Info

Publication number: WO2020026830A1
Application number: PCT/JP2019/028232
Authority: WO
Inventors: 岩下　純久; 石倉　義之; 里奈小笠原; 祐希瀬戸
Original assignee: アズビル株式会社
Priority date: 2018-08-02
Filing date: 2019-07-18
Publication date: 2020-02-06
Also published as: JP2020019110A; JP7113695B2

Abstract

The present invention is provided with: a motor (11); one or more four-piece link mechanisms (12) each having four links including a driving link (121) driven by the motor (11); a displacement sensor (13) that is provided on any of the links of the one or more link mechanisms (12) and detects displacement; and a gripping force detection unit (14) that detects a gripping force from the detection result from the displacement sensor (13).

Description

Robot hand

The present invention relates to a robot hand for holding an object.

把持 One of the functions possessed by the robot hand is the “gripping function”. Grasping is an act of giving a work such as pinching to lift a work when the target object (hereinafter, referred to as a work) is carried using a robot hand, for example. Note that the holding by the robot hand is not limited to the outer diameter holding in which the robot hand holds the work from outside the work, but may be the inner diameter holding in which the robot hand holds the work from the inside of the work (for example, an O-ring).

重要 An important point of the gripping function of the robot hand is “to exert a gripping force for a workpiece (hereinafter, referred to as a gripping force)”. In other words, when the robot hand grips, it is important that a part of the robot hand gripping the work (hereinafter, referred to as a finger) exerts some force on the work. It can be said that managing (detecting, if possible controlling) the magnitude of the force is one of the functions required for the robot hand.

In this robot hand, there has been a method of controlling the gripping force of a finger by controlling the rotational torque of a motor that drives the finger in order to control the gripping force.

However, in this method, when the output shaft of the motor (rotary shaft under torque control) is a transmission mechanism that does not directly drive the finger, it is not possible to accurately control the gripping force due to the influence of friction of the transmission mechanism. Have difficulty. In other words, the torque exerted by the motor is lost due to friction or the like before being transmitted to the fingers, and the loss is not always constant, so that the gripping force actually exerted by the fingers cannot be accurately controlled. The transmission mechanism may be, for example, a transmission such as a gear, a belt, or a feed screw between a motor and a finger, or a mechanism for changing a rotation direction (such as an orthogonal gear). Is present.

For example, in the electric hand disclosed in Patent Literature 1, the motor controls the torque in order to control the gripping force (thrust), but between the motor and the fingers (first and second sets of hand members). A rotation / linear motion conversion mechanism called a cam and a linear guide is provided.

On the other hand, in the robot hand disclosed in Patent Document 2, for example, a force sensor is provided at the base of the finger, and the force sensor detects a reaction force on the finger that is gripping the work, thereby grasping the finger. Detecting force.

JP 2010-94804 A JP-A-2017-164899

On the other hand, in a general force sensor, in order to correctly detect a translational force (hereinafter, referred to as a translational force), an axis of the translational force needs to coincide with a detection portion (detection axis) of the force sensor.
For example, consider a case where a translational force F1 is applied to a finger 102 to which a force sensor 101 is attached as shown in FIG. The axis of F1 coincides with the detection site of the force sensor 101. In this case, the force sensor 101 can correctly detect F1. On the other hand, consider the case where a translational force of F2 is applied to the finger 102. The axis of F2 does not coincide with the detection site of the force sensor 101. In this case, since a moment other than F2 is applied to the detection site of the force sensor 101, the force sensor 101 cannot detect only F2.

When this force sensor is provided at the base of the finger, the value of the force detected by the force sensor changes when the gripping position of the work on the finger changes even if the force applied to the work is constant. That is, in this case, the robot hand cannot obtain an accurate value of the gripping force.

The present invention has been made to solve the above-described problem, and has as its object to provide a robot hand capable of accurately detecting a gripping force regardless of a gripping position of a work.

A robot hand according to the present invention includes a motor and four links including a drive link driven by the motor, and includes one or more four-section link mechanisms and one or more links of the link mechanisms. A displacement sensor is provided at one of the links in the mechanism and detects a displacement, and a gripping force detecting unit that detects a gripping force based on a result detected by the displacement sensor.

According to the present invention, the gripping force can be accurately detected irrespective of the gripping position of the work because the configuration is as described above.

FIG. 1A is a schematic diagram illustrating a configuration example of a robot hand according to Embodiment 1 of the present invention, and FIG. 1B is a diagram illustrating a displacement detected by a displacement sensor in FIG. 1A. FIG. 3 is a perspective view showing a configuration example (only one link mechanism having a displacement sensor) of the robot hand according to the first embodiment of the present invention. 3A and 3B are diagrams illustrating a configuration example (full bridge circuit) and an arrangement example of the displacement sensor according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing a model (only one link mechanism) of a four-bar linkage according to the first embodiment of the present invention. FIG. 5 is a diagram in which a part of the model shown in FIG. 4 is virtually cut. FIG. 6A and FIG. 6B are views showing the divided parts in FIG. FIGS. 7A and 7B are diagrams illustrating an example of a difference in a displacement amount and a stress (simulation result) due to a difference in a position where an external force is applied by the robot hand according to the first embodiment of the present invention. 8A and 8B are diagrams illustrating an example of a difference in sensor output (actual measurement result) due to a difference in a position where an external force is applied by the robot hand according to Embodiment 1 of the present invention. FIG. 9A is a schematic diagram illustrating another configuration example of the robot hand according to Embodiment 1 of the present invention, and FIG. 9B is a diagram illustrating a displacement detected by the displacement sensor in FIG. 9A. FIG. 4 is a schematic diagram showing another configuration example of the robot hand according to Embodiment 1 of the present invention. FIG. 9 is a schematic diagram illustrating a configuration example of a robot hand according to Embodiment 2 of the present invention. It is a figure for explaining an influence on a force sensor by a position to which a translational force is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 and 2 are diagrams showing a configuration example of a robot hand according to Embodiment 1 of the present invention. FIG. 2 shows only one link mechanism 12 having the displacement sensor 13.
The robot hand has a function of holding a work (not shown). As shown in FIGS. 1 and 2, the robot hand includes a motor 11, one or more link mechanisms 12, one or more displacement sensors 13, and a gripping force detector 14 (not shown). In the following, when the same component is present in a plurality of systems, a suffix (-1, -2,...) For each system is added to the code indicating the component, and they are particularly distinguished. If not necessary, the description will be given without suffixes.

The motor 11 is a power source for generating a gripping force on the robot hand. FIG. 1 shows a case where the output shaft 111 of the motor 11 is a dual shaft, and the motor 11 performs rotation output by the output shafts 111-1 and 111-2.

The link mechanism 12 is a four-section link mechanism. FIG. 1 shows a case where the robot hand has two link mechanisms 12-1 and 12-2.
When the robot hand has only one link mechanism 12, the robot hand grips the workpiece using the link mechanism 12 and a fixed member such as a wall.

The link mechanism 12-1 has a drive link 121-1, an angle holding link 122-1 and a driven link 123-1.

One end of the drive link 121-1 is connected to an output shaft 111-1 of the motor 11 via a speed reducer such as the worm 15-1 and the worm wheel 16-1 and a hinge pin (rotary shaft) 124-1a. I have. The drive link 121-1 is driven by the motor 11, and the swing amount (angle, speed, torque, or the like) at one end is controlled according to the rotation of the output shaft 111-1.

One end of the angle holding link 122-1 is rotatably connected to the main body of the robot hand via a hinge pin 124-1b.

In the driven link 123-1, the other end of the drive link 121-1 is rotatably connected via a hinge pin 124-1c, and the other end of the angle holding link 122-1 is rotatably connected via a hinge pin 124-1d. The finger 125-1 is connected to one end. The driven link 123-1 moves integrally with the finger 125-1. In FIG. 1, the angle holding link 122-1 is rotatably connected to one end (finger 125-1 side) of the driven link 123-1 and the drive link 121-1 is rotated to the other end of the driven link 123-1. It is connected freely.

The link mechanism 12-2 has a drive link 121-2, an angle holding link 122-2, and a driven link 123-2.

One end of the drive link 121-2 is connected to an output shaft 111-2 of the motor 11 via a speed reducer such as a worm 15-2 and a worm wheel 16-2 and a hinge pin (rotary shaft) 124-2a. I have. The drive link 121-2 is driven by the motor 11, and the swing amount (angle, speed, torque, or the like) at one end is controlled according to the rotation of the output shaft 111-2.

One end of the angle holding link 122-2 is rotatably connected to the main body of the robot hand via a hinge pin 124-2b.

In the driven link 123-2, the other end of the drive link 121-2 is rotatably connected via a hinge pin 124-2c, and the other end of the angle holding link 122-2 is rotatably connected via a hinge pin 124-2d. The finger 125-2 is connected to one end. The driven link 123-2 moves integrally with the finger 125-2. In FIG. 1, the angle holding link 122-2 is rotatably connected to one end (finger 125-2 side) of the driven link 123-2, and the drive link 121-2 is rotated to the other end of the driven link 123-2. It is connected freely.

The displacement sensor 13 is provided on the drive link 121 of one or more link mechanisms 12 and detects displacement of an attached portion (electrical output according to the displacement (resistance, capacitance, voltage or current, etc.). Output)). In FIG. 1, the displacement sensors 13 are respectively attached to two opposing side surfaces of the drive link 121-1 (two side surfaces in a direction perpendicular to the rotation axis direction of the drive link 121-1), and detect a displacement due to a bending moment. (See FIG. 1B).

Note that the displacement sensor 13 is formed of, for example, a metal strain gauge. Also, for example, as shown in FIG. 3B, four metal strain gauges (R1 to R4) are attached as the displacement sensor 13 to form a full bridge circuit (Wheatstone bridge circuit) as shown in FIG. 3A. In addition, a distortion component other than the bending moment can be removed, temperature compensation can be performed, and high precision can be achieved. In FIG. 3A, E represents an applied voltage, E _o represents the output voltage.
The displacement sensor 13 may be attached to each of two or more side surfaces of the drive link 121-1 for the above-described reason. However, only one displacement sensor may be attached to one side surface. It does not change.

変位 Further, the displacement sensor 13 may be composed of, for example, a semiconductor strain gauge. The semiconductor strain gauge is realized by MEMS (Micro Electro Mechanical Systems).

The gripping force detector 14 detects a gripping force (external force applied to the finger 125) of the robot hand from a detection result (for example, an output voltage, an output current, a change in resistance value or a change in capacitance) of the displacement sensor 13. . The gripping force detection unit 14 is realized by a processing circuit such as a system LSI (Large Scale Integration) or a CPU (Central Processing Unit) that executes a program stored in a memory or the like.

Next, effects of the robot hand shown in FIG. 1 will be described.
As described above, in the method of detecting the gripping force of the robot hand using the force sensor provided at the base of the finger, the gripping force may not be accurately detected, but the following two factors are factors. No.
The first point is that the force sensor is substantially affected by not only the translational force in the gripping direction but also the moment in detecting the gripping force.
The second point is that the moment applied to the root of the finger changes depending on the gripping position (the position where the finger receives an external force).

Therefore, the robot hand shown in FIG. 1 uses a four-node link mechanism 12 having a drive link 121 and a displacement sensor 13 for detecting the displacement of the drive link 121, and based on the detection result of the displacement sensor 13, the gripping force of the robot hand. Has been detected. That is, in the four-link mechanism 12, only the hinge portion (point D shown in FIG. 4) at the other end of the drive link 121 is active driven by the motor 11, and the remaining hinge portion (point A shown in FIG. 4). , B and C) are passive. Therefore, the external force applied to the finger 125 is received at the other end of the drive link 121, and a moment based on the external force and the length of the drive link 121 is applied to the drive link 121. This moment is constant irrespective of the position where the external force is applied, and by detecting the displacement due to this moment with the displacement sensor 13, the robot hand can detect the gripping force. As described above, in the robot hand shown in FIG. 1, the influence of the gripping position can be reduced and the same displacement can be detected regardless of the position of the finger 125 where the finger is gripped, so that the detection accuracy of the gripping force can be ensured. The gripping position may be any position on the gripping surface of the finger 125 (any position in the vertical direction and the depth direction in FIG. 1).

Next, the principle of obtaining the same sensor output in the robot hand shown in FIG. 1 even when the position to which an external force is applied is different will be described.
FIG. 4 is a diagram in which one link mechanism 12 shown in FIG. 1 is modeled, and the links 121 to 123 constitute a parallelogram link mechanism. In FIG. 4, θ represents the swing angle of the link mechanism 12, and Φ represents the joint arrangement angle (the angle formed between the line connecting the one end of the drive link 121 and the one end of the angle holding link 122 and the horizontal direction). L represents the length of the drive link 121 and F represents the external force (translational force) applied to the finger 125.

FIG. 5 is a diagram showing a case where a part of the model shown in FIG. 4 is virtually cut. Specifically, a portion between hinges of the angle holding link 122 and a portion between hinges of the driven link 123 are cut off. . Here, in FIG. 5, since the passive hinges of the

links

122 and 123 are respectively cut, no bending moment is generated at the cut portion, and only a force in the tension direction or the compression direction is generated.

6A, the X-axis direction component (horizontal direction component) is represented by the following equation (1), and the Y-axis direction component (vertical direction component) is represented by the following equation (2). Become like In Equations (1) and (2), N1 represents the force applied to the cut portion of the angle holding link 122, and N2 represents the force applied to the cut portion of the driven link 123.
F−N1 sin θ + N2 cosΦ = 0 (1)
N1cosθ + N2sinΦ = 0 (2)

6B, the component in the X-axis direction is represented by the following expression (3), the component in the Y-axis direction is represented by the following expression (4), and the component around the Z axis is represented by the following expression. The following equation (5) is obtained. In other words, since one end (point D shown in FIG. 6B) of the drive link 121 is a fixed end, the drive link 121 has He, which is a translation force in the X-axis direction, Ve, which is a translation force in the Y-axis direction, and around the Z axis. Of Me.
-N2cosΦ + He = 0 (3)
-N2 sinΦ + Ve = 0 (4)
Me = L · N2 · cos (θ−Φ) (5)

Then, the following expressions (6) and (7) are obtained from the expressions (1) and (2).
N1 = F · (sinφ / cos (θ−φ)) (6)
N2 = −F · (cos θ / cos (θ−Φ)) (7)

Then, the following expression (8) is obtained from the expressions (5) and (7).
Me = LF · cos θ (8)

において In equation (8), L is a constant when the link structure of the robot hand is determined, and is known. Θ can be detected by an encoder (not shown) of the motor 11. From the above, it can be said that Expression (8) does not include an element that depends on the position of the external force, and Me (moment applied to the drive link 121) does not depend on the position of the external force. Therefore, in the robot hand shown in FIG. 1, the same sensor output is obtained even when the position where the external force is applied is different, and the external force (gripping force) can be accurately detected.

Next, FIG. 7 shows a simulation result of verifying a difference in displacement (bending moment) and stress of the drive link 121 due to a difference in a position where an external force is applied. FIG. 7 shows a simulation result in the case where 1N compressive force is applied to different positions P1 and P2 of the finger 125, respectively. It can be seen from FIG. 7 that the displacement amount and the stress of the drive link 121 are almost equal between the position P1 and the position P2.
FIG. 8 shows a result obtained by mounting the displacement sensor 13 on an actual machine and actually measuring a sensor output depending on a difference in a position where an external force is applied. FIG. 8 shows actual measurement results when forces in the directions indicated by arrows are applied to different positions P3 and P4 of the finger 125, respectively. It can be seen from FIG. 8 that the output of the drive link 121 is substantially equal between the position P3 and the position P4.
From these results, it can be seen that in the robot hand shown in FIG. 1, the change in the sensor output due to the difference in the position where the external force is applied is small.

In the above description, the case where the displacement sensor 13 detects the displacement due to the bending moment has been described. However, the invention is not limited thereto, and the displacement sensor 13 may detect a displacement due to a shearing force (see FIG. 9B). In this case, as shown in FIG. 9A, for example, the displacement sensor 13 is attached to each of two opposing side surfaces of the drive link 121-1 (two side surfaces in the rotation axis direction of the drive link 121-1).

In the above description, the case where the drive link 121 is disposed outside the angle holding link 122 has been described. However, the invention is not limited thereto, and the drive link 121 may be disposed inside the angle holding link 122.
In the above description, the case where the output shaft 111 of the motor 11 is a double shaft has been described. However, the invention is not limited thereto, and the output shaft 111 of the motor 11 may be a single shaft.

For example, FIG. 10 shows a case where the drive link 121 is disposed inside the angle maintaining link 122 and the output shaft 111 is a single shaft.
FIG. 10 illustrates a case where the output shaft 111 of the motor 11 is a single shaft, and the motor 11 performs rotation output by the output shaft 111.

The drive link 121-1 shown in FIG. 10 has one end connected to an output shaft 111 of the motor 11 via a speed reducer such as the worm 15 and the worm wheel 16-1 and a hinge pin 124-1a. The drive link 121-1 is driven by the motor 11, and the swing amount (angle, speed, torque, or the like) at one end is controlled according to the rotation of the output shaft 111.
In FIG. 10, the drive link 121-1 is rotatably connected to one end (finger 125-1 side) of the driven link 123-1 and the angle holding link 122-1 is connected to the other end of the driven link 123-1. It is rotatably connected.

Similarly, one end of the drive link 121-2 shown in FIG. 10 is connected to the output shaft 111 of the motor 11 via a speed reducer such as the worm 15 and the worm wheel 16-2 and a hinge pin 124-2a. . The drive link 121-2 is driven by the motor 11, and the swing amount (angle, speed, torque, or the like) at one end is controlled according to the rotation of the output shaft 111.
In FIG. 10, the drive link 121-2 is rotatably connected to one end (the finger 125-2 side) of the driven link 123-2, and the angle holding link 122-2 is connected to the other end of the driven link 123-2. It is rotatably connected.

Other configurations are the same as those of the robot hand shown in FIG. 1, and description thereof will be omitted. The effects and principles of the robot hand shown in FIG. 10 are the same as the effects and principles of the robot hand shown in FIG.
In the robot hand shown in FIG. 10, the case where the displacement sensor 13 detects a displacement due to a bending moment is shown, but the displacement sensor 13 may detect a displacement due to a shear force. In this case, the mounting position of the displacement sensor 13 is the same as that in FIG. 9A.

In the above description, a case has been described in which the output shaft 111 and the rotation axis of the drive link 121 are configured to be orthogonal (including the meaning of substantially orthogonal). However, the invention is not limited thereto, and the output shaft 111 and the rotation axis of the drive link 121 may be configured to be parallel (including substantially parallel) using a spur gear or the like.

In the above description, the case where the displacement sensor 13 is provided on the drive link 121 has been described. However, the invention is not limited thereto, and the displacement sensor 13 may be provided on the angle holding link 122 or the driven link 123.
That is, as shown in FIG. 6A, for example, when an external force is applied to the finger 125, only the force N1 is applied to the angle holding link 122, and only the force N2 is applied to the driven link 123. N1 and N2 are forces that do not depend on the position of the external force, as shown in equations (6) and (7). Therefore, even if the displacement sensor 13 is provided on the angle holding link 122 or the driven link 123 and the displacement sensor 13 detects the displacement due to N1 or N2, the robot hand can also detect the gripping force.

In the above description, the case where the displacement sensor 13 is provided on the link (the drive link 121-1 in FIGS. 1, 9, and 10) of one link mechanism 12 is shown. However, the present invention is not limited to this, and the displacement sensor 13 may be provided on a link in a part or all of the other link mechanisms 12. By providing the displacement sensors 13 in the plurality of link mechanisms 12, the accuracy of detecting the gripping force of the robot hand is improved.

In the above description, the case where the robot hand grips the outer diameter has been described, but the same applies to the case where the robot hand grips the inner diameter.

As described above, according to the first embodiment, the robot hand has the motor 11 and the four links including the drive link 121 driven by the motor 11, and includes four or more sections provided with one or more. A link mechanism 12, a displacement sensor 13 provided at any one of the links in the one or more link mechanisms 12, for detecting displacement, and a gripping force detecting unit 14 for detecting a gripping force from a detection result by the displacement sensor 13. With. Thereby, the robot hand according to the first embodiment can accurately detect the gripping force regardless of the gripping position of the work.

Embodiment 2 FIG.
In the robot hand according to the first embodiment, the case where the four-link mechanism 12 is used has been described. On the other hand, the robot hand may use a link mechanism 12 having five or more nodes. Specifically, for example, as shown in FIG. 11, the angle holding link 122 is composed of a plurality of (M) links (links 1221 and 1222 in FIG. 11) rotatably connected in series, so that (4 + M) The link mechanism 12 of the joint may be configured. In FIG. 11, illustration of the output shaft 111-2, the link mechanism 12-2, the worm 15-2, and the worm wheel 16-2 is omitted. FIG. 11 shows a case where the drive link 121 is disposed inside the angle holding link 122 and the output shaft 111 is a double shaft, but the configuration is not limited to this, as in the first embodiment. It is.
When the angle holding link 122 is composed of a plurality of links, a lock mechanism is provided at a hinge portion of each link to prevent the link from being rotated by an external force when the robot hand grips the work. Need to be done.

If the robot hand has five or more link mechanisms 12, the displacement sensor 13 is provided on the drive link 121 of the one or more link mechanisms 12.

In the robot hands according to the first and second embodiments, the case where the motor 11 performs the rotation output by the output shaft 111 has been described. However, the present invention is not limited to this, and the motor 11 may perform a linear motion output. The power of the motor 11 is not limited to electric power, and may be, for example, an air or hydraulic power.

In the present invention, any combination of the embodiments, a modification of an arbitrary component of each embodiment, or an omission of an arbitrary component in each embodiment is possible within the scope of the invention. .

The robot hand according to the present invention can accurately detect a gripping force irrespective of a gripping position of a work, and is suitable for use in a robot hand gripping an object.

Reference Signs List 11 motor 12 link mechanism 13 displacement sensor 14 gripping force detector 15 worm 16 worm wheel 111 output shaft 121 drive link 122 angle holding link 123 driven link 124 hinge pin 125 finger 1221, 1222 link

Claims

Motor and
A four-link mechanism having four links, including four links including a drive link driven by the motor;
A displacement sensor provided at any one of the links in one or more link mechanisms of the link mechanisms, for detecting displacement;
A gripping force detection unit configured to detect a gripping force from a detection result of the displacement sensor.
The drive link has one end connected to a rotating shaft driven by the output of the motor,
The link mechanism,
An angle holding link one end of which is rotatably connected to the body,
The robot hand according to claim 1, wherein the other end of the drive link and the other end of the angle holding link are rotatably connected, and a driven link having a finger connected to one end.
The robot hand according to claim 2, wherein the output shaft is a single shaft or a double shaft.
The drive link is rotatably connected to the one end side of the driven link,
The robot hand according to claim 2, wherein the angle holding link is rotatably connected to the other end of the driven link.
The angle holding link is rotatably connected to the one end side of the driven link,
The robot hand according to claim 2 or 3, wherein the drive link is rotatably connected to the other end of the driven link.
Motor and
A plurality of links including a drive link driven by the motor, and one or more provided five or more link mechanisms;
A displacement sensor provided on the drive link in one or more of the link mechanisms for detecting displacement;
A gripping force detection unit configured to detect a gripping force from a detection result of the displacement sensor.
The drive link has one end connected to a rotating shaft driven by the output of the motor,
The link mechanism,
An angle holding link composed of a plurality of links rotatably connected in series, one end of which is rotatably connected to the main body,
The robot hand according to claim 6, wherein the other end of the drive link and the other end of the angle holding link are rotatably connected, and a driven link having a finger connected to one end.
The robot hand according to claim 7, wherein the output shaft is a single shaft or a double shaft.
The drive link is rotatably connected to the one end side of the driven link,
The robot hand according to claim 7 or 8, wherein the angle holding link is rotatably connected to the other end of the driven link.
The angle holding link is rotatably connected to the one end side of the driven link,
The robot hand according to claim 7 or 8, wherein the drive link is rotatably connected to the other end of the driven link.