JP2018030184A - Movement assisting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a movement assisting device capable of reducing a load to a user due to mass of an actuator.SOLUTION: A movement assisting device includes: a mounting fixture attached to a human body of a user, and having a joint part for connecting a first member and a second member in a relatively rotatable manner; an actuator for relatively rotating the first member and the second member; a control device for performing drive control of the actuator; and a battery device for charging electric power to be supplied to the actuator. The actuator is disposed at a front surface part disposed at a front surface of a user in the mounting fixture. The battery device is disposed at a back surface part disposed at a back surface of the user in the mounting fixture.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an operation assisting device used by being worn on a human body.

  2. Description of the Related Art In recent years, a human-mounted robot is known as an operation assisting device that assists or assists a normal person or a disabled person. The human body-mounted robot includes, for example, a joint part to be worn by a user, a sensor for detecting the user's intention or state, or a surrounding situation, an actuator that applies rotational torque to the joint part, and driving of the actuator And a control device that performs control. In general, an actuator includes a motor and a transmission that converts high-speed rotation of the motor into low-speed rotation suitable for human movement. The transmission transmits the rotation of the motor to the joint at a gear ratio of 1/50 to 1/200, for example. The actuator is configured by combining, for example, a harmonic drive (registered trademark) or a worm gear and a DC motor.

  In many existing human body-mounted robots, the actuator is mounted directly on the joint of the human body or at a position close to the joint of the human body. In such a configuration, the user needs to perform an operation against the mass and inertial force of the actuator. On the other hand, in general, when an object with a large mass or a bulky object is installed on the front side of the user's torso or on a special device such as a wheelbarrow separated from the body, the mass of the actuator is Can be avoided.

  For example, Patent Literature 1 discloses an operation assisting device in which a pneumatic actuator including a tube is used and several electric devices such as an air tank and a battery are held in a backpack unit. According to such a motion assisting device, the components around the user's lower leg are not bulky, and the design is flat and lightweight.

US Patent Application Publication No. 2015/173993

  However, if a heavy and bulky backpack is on the back, daily life such as sitting on a chair may be inconvenient. In addition, the user must always carry a heavy backpack and cannot remove the backpack from the user's body while using the motion assist device. In particular, for elderly people, if they continue to carry heavy backpacks, they will soon get tired.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved motion assist device that can reduce the load on the user due to the mass of the component parts. It is in.

  In order to solve the above-described problem, according to an aspect of the present invention, there is provided a wearing tool that has a joint part that is attached to a human body of a user and that connects the first member and the second member so as to be relatively rotatable. An actuator that relatively rotates the second member and the second member, a control device that performs drive control of the actuator, and a battery device that stores electric power supplied to the actuator. There is provided an operation assisting device that is disposed on a front surface portion that is disposed on a front surface, and in which a battery device is disposed on a back surface portion that is disposed on a back surface of a user among wearing devices.

  According to the motion assisting device of the present invention, since the actuator is disposed on the front side of the mounting tool and the battery device is disposed on the back side of the mounting tool, the position of the center of gravity of the user wearing the motion assisting device in the front-rear direction is determined. , Can be maintained near the front-rear position of the center of gravity of the body. Therefore, the load on the user due to the mass of the actuator is reduced.

  A control device that performs drive control of the actuator may be further provided, and the control device may be disposed on the back surface of the wearing tool.

  The actuator may be disposed on the front surface of the waist mounting portion of the mounting tool, and the battery device may be disposed on the back surface of the waist mounting portion.

  The actuator may be disposed on the front surface of the vest of the wearing tool, and the battery device may be disposed on the back surface of the vest.

  As described above, according to the present invention, the load on the user due to the mass of the component can be reduced.

It is a front view of the movement auxiliary device concerning an embodiment of the invention. It is a rear view of the movement auxiliary device concerning the embodiment. It is a side view of the movement auxiliary device concerning the embodiment. It is a system configuration figure of a movement auxiliary device concerning the embodiment. It is a front view of the movement auxiliary device concerning a modification. It is a rear view of the movement auxiliary device concerning a modification. It is a side view of the movement auxiliary device concerning a modification.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(1. Basic configuration of motion assist device)
With reference to FIGS. 1-3, the example of whole structure of the operation assistance apparatus 1 which concerns on this embodiment is demonstrated. 1 to 3 are a front view, a rear view, and a side view, respectively, showing a state in which the user wears the motion assisting device 1.

  The motion assisting device 1 according to the present embodiment is a device for assisting the movement of the left and right legs such as a walking motion or a stair climbing motion by assisting the movement of the user's hip joint. be called. The motion assisting device 1 includes a mounting tool, actuators 20a and 20b, a battery unit (battery device) 23, and a control unit (control device) 25.

  In the motion assisting apparatus 1 according to the present embodiment, the wearing tool includes the waist mounting portion 15, the waist fixing belt 13, the first arm portions 31a and 31b, the second arm portions 33a and 33b, and the thigh. Mounting portions 37a and 37b and thigh fixing belts 39a and 39b are provided. Among the mounting tools, the first arm portions 31a and 31b and the second arm portions 33a and 33b can be constituted by, for example, a molded body formed of a resin material, and achieve a certain degree of rigidity and weight reduction. Is done. Therefore, the first arm portions 31a and 31b and the second arm portions 33a and 33b have resistance to bending and cracking. On the other hand, the waist mounting portion 15, the waist fixing belt 13, the thigh mounting portions 37a and 37b, and the thigh fixing belts 39a and 39b are, for example, woven fabrics and knitted fabrics so as to be able to cope with the differences in physique for each user. Can be configured.

  The waist mounting portion 15 is wound around the user's waist and is fixed to the waist using the waist fixing belt 13. The waist fixing belt 13 includes, for example, a connecting tool 11 such as a buckle or a hook-and-loop fastener. By connecting the connecting tool 11, the left and right waist fixing belts 13 are connected, and the waist mounting part 15 is fixed to the waist. The connecting tool 11 or the waist fixing belt 13 may include a length adjusting portion whose length can be adjusted by folding the belt or the like.

  The first arm portions 31a and 31b are fixed to a portion of the waist mounting portion 15 located on the side of the body. The first arm portions 31 a and 31 b are provided to extend downward from the waist mounting portion 15. Second arm portions 33a and 33b are connected to the first arm portions 31a and 31b via joint portions 30a and 30b. The joint portions 30a and 30b are provided so as to correspond to the position of the user's hip joint. In the joint portions 30a and 30b, the lower portions of the first arm portions 31a and 31b and the upper portions of the second arm portions 33a and 33b are connected to be relatively rotatable. For example, the first arm portions 31a and 31b and the second arm portions 33a and 33b may be supported so as to be relatively rotatable with respect to a rotation shaft portion (not shown) provided in the joint portions 30a and 30b.

  The second arm portions 33a and 33b extend downward from the joint portions 30a and 30b, and support frames 35a and 35b are provided below the second arm portions 33a and 33b. The support frames 35a and 35b are fixed to the thigh mounting portions 37a and 37b. The second arm portions 33a and 33b and the thigh mounting portions 37a and 37b may be integrally formed. The thigh mounting portions 37a and 37b are wound below the thighs of the user's legs and are fixed to the thighs using thigh fixing belts 39a and 39b. The thigh fixing belts 39a and 39b have connecting tools (not shown) such as buckles or hook-and-loop fasteners, and the thigh fixing belts 39a and 39b are fixed to the thighs by connecting the connecting tools. The thigh fixing belts 39a and 39b may be provided with a length adjusting unit capable of adjusting the length by folding the belt.

  The relative rotation operations of the first arm portions 31a and 31b and the second arm portions 33a and 33b around the joint portions 30a and 30b are driven by the actuators 20a and 20b. The actuators 20a and 20b make the first arm portions 31a and 31b and the second arm portions 33a and 33b relative to each other by winding or sending out the wires 21a and 21b as flexible force transmission members. Rotate.

  Moreover, the movement assistance apparatus 1 may have a myoelectric potential sensor (not shown) for detecting a myoelectric potential signal of the user. The myoelectric potential sensor may include, for example, a surface myoelectric potential detection electrode (surface electrode) disposed on the surface of the user's thigh. The myoelectric potential sensor is arranged with its position determined in advance according to the exercise unit (muscle) corresponding to the muscle force for performing the operation assisted by the operation assisting device 1. In addition, the number of surface electrodes may be one or plural.

  For example, since the motion assisting device 1 according to the present embodiment is a device that assists the user's leg motion in the back and forth direction, the surface electrodes of these myoelectric sensors detect the myoelectric potential of the user's quadriceps at the time of wearing. It is arranged at a detectable position. At this time, the electrode of the myoelectric potential sensor may include two electrodes arranged close to each other. Furthermore, the electrodes of the myoelectric potential sensor may be arranged along the direction of the muscle fibers of the motor unit. Thereby, the myoelectric potential of the same muscle fiber is easily detected, and the difference between the two detection values can be obtained to reduce noise.

  As the myoelectric potential sensor, for example, a capacitance type sensor is used. In the electrostatic capacitance type myoelectric potential sensor, the electrostatic capacitance changes in accordance with the detected myoelectric potential, and the change in the electrostatic capacitance is converted into an electrical signal and output. If it is a capacitance type myoelectric potential sensor, the myoelectric potential of a desired muscle can be detected without directly contacting the surface of the skin. When an electrostatic capacitance type myoelectric potential sensor is used, the myoelectric potential sensor includes, for example, an electrode unit, an oscillation circuit, and an output circuit. The myoelectric potential sensor may include an AD converter and an amplifier. The myoelectric potential sensor may include an AD converter and an amplifier. The electrode portion of the myoelectric potential sensor may be, for example, a monopolar, bipolar, or tripolar electrode, and may be an array type or matrix type electrode.

(2. System configuration)
FIG. 4 shows a system configuration example of the motion assisting device 1. This system configuration example shows a system configuration for relatively rotating the first arm portion 31 and the second arm portion 33 on one side of the left and right legs. 4, a block diagram of the actuator 20, the battery unit 23, and the control unit 25 is shown together with a configuration example of a rotation mechanism that relatively rotates the joint portions 30a and 30b. Further, FIG. 4 shows a configuration example of the rotation mechanism when the first arm portion 31 and the second arm portion 33 are viewed from the back side.

  In the motion assisting apparatus 1 according to the present embodiment, the joint portions 30a and 30b that rotatably connect the first arm portions 31a and 31b and the second arm portions 33a and 33b are flexible forces such as wires. It is driven by the actuator 20 via the transmission member. In the illustrated rotating mechanism, a Bowden cable in which the periphery of the wire 21 is covered with covers 61 and 63 is used as a force transmission member. The Bowden cable is fixed to the first arm portion 31 by fixing members 65 and 67. However, the wire 21 of the Bowden cable is movable in the covers 61 and 63. The flexible force transmission member is not limited to a wire or a Bowden cable, and may be a belt or a chain.

  In the joint portion 30, a pulley 71 having the same axis as the rotation shaft portion 73 is provided on the back surface side of the second arm portion 33. On the outer circumferential surface of the pulley 71, a groove in which the wire 21 is disposed is provided along the circumferential direction. For example, the rotation shaft portion 73 is fixed to the first arm portion 31, while the pulley 71 of the second arm portion 33 is rotatably supported by the rotation shaft portion 73. A wire 21 is wound around the pulley 71, and each end portion of the wire 21 is led out from the actuator 20. The actuator 20 winds up one end side of both ends of the wire 21 wound around the pulley 71 and sends out the other end side. As a result, the pulley 71 is rotated about the rotation shaft portion 73, and the second arm portion 33 is rotated.

  The actuator 20 includes, for example, a motor and a speed reduction mechanism. As the motor, for example, a stepping motor or a brushless motor can be used. The actuator 20 is not limited to an actuator using a rotary rotary motor, and may be an actuator including a linear motor and a rotation mechanism. By driving the actuator 20, the pulley 71 provided in the joint portion 30 rotates, and the second arm portion 33 rotates around the joint portion 30. Thereby, the movement of the user's thigh around which the thigh mounting part 37 is wound is assisted.

  A battery unit 23 is connected to the actuator 20. The battery unit 23 supplies power to the actuator 20. The actuator 20 is driven and controlled by the control unit 25. The control unit 25 drives the actuator 20 by controlling the electric power supplied to the actuator 20, and rotates the second arm portion 33 bidirectionally. The control unit 25 includes, for example, a microcomputer such as a CPU (Central Processing Unit), a storage element such as a ROM (Read Only Memory) or a RAM (Random Access Memory), a drive circuit, and the like.

  For example, the microcomputer rotates the second arm unit 33 according to the user's intention by executing a program stored in the ROM in advance. For example, the microcomputer may calculate the required auxiliary force based on a sensor signal from a myoelectric potential sensor or the like that can detect the user's movement intention, and may perform the feedforward control of the actuator 20. Alternatively, the rotational speed or rotational torque when the first arm portion 31 and the second arm portion 33 rotate relative to each other in accordance with the user's operation is detected, and the actuator 20 is controlled based on the rotational speed or rotational torque. Feedback control may be performed. The control method of the actuator 20 by the control unit 25 is not limited to these examples.

  The motion assisting device 1 according to the present embodiment has a first centering on the left and right joints 30a and 30b arranged on both sides of the user's hip joint in order to assist the movement of the left and right legs. It is comprised as an apparatus which rotates the arm parts 31a and 31b and the 2nd arm parts 33a and 33b relatively. Therefore, at least the actuator 20 includes two actuators 20a and 20b corresponding to the left and right joint portions 30a and 30b, respectively. Further, the motion assisting device 1 according to the present embodiment includes one battery unit 23 that supplies electric power to the two actuators 20a and 20b. The two actuators 20a and 20b are driven and controlled by one control unit 25.

(3. Configuration for reducing the load on users)
In the motion assisting apparatus 1 according to the present embodiment, the battery unit 23 and the control unit 25 are disposed on the back surface portion 15R of the waist mounting portion 15, and the two actuators 20a and 20b are disposed on the front surface portion 15F of the waist mounting portion 15. Yes. Since these actuators 20a and 20b, the battery unit 23, and the control unit 25 are all relatively large in mass, if they are arranged together on the front side or the back side of the user, the center of gravity of the user wearing the motion assisting device 1 is placed. The position in the front-rear direction may be shifted from the position in the front-rear direction of the center of gravity of the body, which may increase the load on the user.

  However, in the motion assisting apparatus 1 according to the present embodiment, the two actuators 20a and 20b, the battery unit 23, and the control unit 25 are arranged separately on the front side and the back side. For this reason, the position of the user's center of gravity in the front-rear direction can be maintained at a position close to the position of the body's center of gravity in the front-rear direction when the motion assisting device 1 is mounted. Thereby, a user's load can be reduced.

  Further, in the motion assisting apparatus 1 according to the present embodiment, the battery unit 23 and the control unit 25 have a relatively thin outer shape, and are provided on the back surface portion 15R disposed on the back surface of the user among the waist mounting portion 15. They are arranged in parallel. For example, the battery unit 23 and the control unit 25 are packed in advance in the holding member 17 and are fixed to the back surface portion 15 </ b> R of the waist mounting portion 15. The battery unit 23 and the control unit 25 are connected to a cable (not shown) that transmits electric power or an electric signal to the actuators 20a and 20b, and the other end side of the cable is connected to the actuators 20a and 20b or can be connected. Yes. The control unit 25 and the actuators 20 and 20b may be connected by wireless communication means.

  Since the operation assisting device 1 includes the thin battery unit 23 and the control unit 25, the battery unit 23 and the control unit 25 are not bulky. Therefore, for example, even when the user sits on a chair or the like with the motion assisting device 1 mounted, the battery unit 23 and the control unit 25 do not get in the way. In addition, since the operation assisting device 1 includes the thin battery unit 23 and the control unit 25, the operation assisting device 1 has a clean appearance.

  In addition, while the battery unit 23 and the control unit 25 are made thin, it is often difficult to make the actuators 20a and 20b thin because of the structure. However, in the motion assisting apparatus 1 according to the present embodiment, the actuators 20a and 20b are arranged on the front surface portion 15F of the waist mounting portion 15, so that the actuators 20a and 20b themselves are close to the position in the front-rear direction of the body center of gravity. Can be held. Therefore, the load on the user due to the mass of the actuator can be reduced.

(4. Modifications)
So far, an example of the motion assisting apparatus 1 according to the present embodiment has been described. The motion assisting apparatus 1 according to the present embodiment is not limited to the above example, and various modifications can be made. Hereinafter, a different example of the motion assisting device 1 from the motion assisting device 1 according to the above embodiment will be described.

  5 to 7 are a front view, a rear view, and a side view, respectively, showing a user wearing the motion assisting device 101 according to a modification. The motion assisting device 101 according to the modification is different from the motion assisting device 1 according to the above-described embodiment in that the motion assisting device 101 has two joint portions corresponding to the left and right legs, respectively.

  The motion assisting device 101 according to the modification includes a mounting tool, actuator units 120a and 120b, a battery unit 123, and a control unit 25. The wearing tools include a vest 115, vest fixing belts 109 and 113, first arm parts 131a and 131b, second arm parts 133a and 133b, third arm parts 143a and 143b, and thigh attachments. Parts 137a, 137b, thigh fixing belts 139a, 139b, crus mounting parts 147a, 147b, and crus fixing belts 149a, 149b.

  Among the mounting tools, the first arm portions 131a and 131b, the second arm portions 133a and 133b, and the third arm portions 143a and 143b can be formed of a molded body formed of a resin material, for example. On the other hand, the vest 115, the vest fixing belts 109 and 113, the thigh mounting portions 137a and 137b, the thigh fixing belts 139a and 139b, the crus mounting portions 147a and 147b, and the crus fixing belts 149a and 149b are, for example, Further, it can be composed of a woven fabric, a knitted fabric or the like.

  The vest 115 is attached to the upper body of the user and fixed to the waist using the vest fixing belts 109 and 113. The vest fixing belts 109 and 113 include, for example, connecting tools 107 and 111 such as buckles or hook-and-loop fasteners, and by connecting the connecting tools 107 and 111, the left and right vest fixing belts 109 and 113 are connected. Fixed to the upper body. First arm portions 131a and 131b are fixed to portions of the vest 115 located on the side of the waist of the body. The second arm portions 133a and 133b are connected to the first arm portions 131a and 131b via the first joint portions 130a and 130b. The first joint portions 130a and 130b are provided so as to correspond to the positions of the user's hip joints.

  Intermediate portions in the length direction of the second arm portions 133a and 133b are fixed to the thigh mounting portions 137a and 137b. The thigh mounting parts 137a and 137b are wound below the thighs of the user's legs and are fixed to the thighs using the thigh fixing belts 139a and 139b. The third arm portions 143a and 143b are connected to the second arm portions 133a and 133b via the second joint portions 140a and 140b. The second joint portions 140a and 140b are provided so as to correspond to the position of the user's knee joint.

  Support frames 145a and 145b are provided below the third arm portions 143a and 143b. The support frames 145a and 145b are fixed to the crus mounting portions 147a and 147b. The third arm portions 143a and 143b and the crus attachment portions 147a and 147b may be integrally formed. The lower leg mounting parts 147a and 147b are wound around the lower leg part of the user's leg and fixed to the lower leg part using the lower leg fixing belts 149a and 149b.

  The relative rotation operation of the first arm portions 131a and 131b and the second arm portions 133a and 133b with the first joint portions 130a and 130b as the center is the first actuator provided in the actuator units 120a and 120b. Driven by. In addition, relative rotation operations of the second arm portions 133a and 133b and the third arm portions 143a and 143b with the second joint portions 140a and 140b as the center are the second rotation units provided in the actuator units 120a and 120b. It is driven by the actuator. The first actuator causes the first arm portions 131a and 131b and the second arm portions 133a and 133b to rotate relative to each other by winding or sending out the wires 121a and 121b as force transmission members. Further, the second actuator relatively rotates the second arm parts 133a and 133b and the third arm parts 143a and 143b by winding or sending out the wires 122a and 122b as force transmission members. .

  Further, the motion assisting device 101 may have a myoelectric potential sensor (not shown) for detecting a user's myoelectric potential signal. The myoelectric potential sensor can include, for example, surface myoelectric potential detection electrodes (surface electrodes) disposed on the surfaces of the user's thigh and crus.

  A configuration for relatively rotating the first arm portions 131a and 131b and the second arm portions 133a and 133b by the first actuator, and the second arm portions 133a and 133b and the third arm by the second actuator The configuration for relatively rotating the arm portions 143a and 143b can be the same as the configuration using the rotation mechanism according to the above-described embodiment. Electric power is supplied from a common battery unit 123 to the first actuator and the second actuator, respectively. Further, the first actuator and the second actuator are each driven and controlled by a common control unit 125. However, a separate battery unit and control unit may be connected to each of the first actuator and the second actuator.

  In addition, since the actuator units 120a and 120b are mounted on the front surface side of the vest 115, the user holds the actuator units 120a and 120b having a large mass near the position in the front-rear direction of the center of gravity of the body. It becomes easy to do. Furthermore, the battery unit 123 and the control unit 125 have a relatively thin outer shape, and are arranged in parallel on the back surface portion 115 </ b> R of the vest 115 disposed on the back surface of the user. Therefore, the position of the user's center of gravity in the front-rear direction can be maintained at a position close to the position of the body's center of gravity in the front-rear direction when the motion assist device 101 is mounted. Thereby, a user's load can be reduced.

  As described above, in the motion assisting apparatus 1 according to the present embodiment, the actuator 20 is disposed on the front side of the user, and the battery unit 23 and the control unit 25 are disposed on the back side of the user. Therefore, the components having a relatively large mass are provided separately in the front-rear direction of the user's body, so that the center of gravity of the user wearing the motion assisting device 1 can be maintained at a position close to the center of gravity of the body. Thereby, a user's load is reduced.

  Further, in the motion assisting apparatus 1 according to the present embodiment, the battery unit 23 and the control unit 25 arranged on the back side of the user have a thin and non-bulky outer shape. Therefore, when the user sits on a chair or the like, the battery unit 23 and the control unit 25 are less likely to get in the way.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above embodiment, the motion assisting device 1 is configured as a device that assists the user's movement of both legs, but the present invention is not limited to such an example. For example, the motion assisting device may be a device that assists the user's movement of one leg. In this case, the first arm portion, the second arm portion, or the third arm is provided only on either the left or right side. Further, the movement assist device 1 may be a device that assists the movement of the arm.

  Further, in the above embodiment, the motion assisting device 1 includes the myoelectric potential sensor, and detects the user's myoelectric potential signal by the myoelectric potential sensor to control the driving of the actuator 20, but the present invention is limited to such an example. Not. For example, instead of the myoelectric potential sensor, a sensor that detects a biological signal other than the myoelectric potential signal may be used. Examples of the biological signal include, but are not limited to, an electroencephalogram, a skin electroencephalogram, an electric skin reaction, or a nerve potential.

DESCRIPTION OF SYMBOLS 1 Operation | movement assistance apparatus 15 Waist part mounting part 20,20a, 20b Actuator 21,21a, 21b Wire 23 Battery unit 25 Control unit 30,30a, 30b Joint part 31,31a, 31b 1st arm part 33,33a, 33b 2nd Arm part 37, 37a, 37b Thigh attachment part 61, 63 Cover

Claims (4)

A wearing tool that is attached to a user's human body and has a joint portion that connects the first member and the second member in a relatively rotatable manner;
An actuator for relatively rotating the first member and the second member;
A control device that performs drive control of the actuator;
A battery device for storing electric power supplied to the actuator,
The actuator is disposed on a front surface portion of the mounting tool that is disposed on a front surface of the user, and the battery device is disposed on a back surface portion of the mounting tool that is disposed on the back surface of the user. Operation assistance device. A control device for controlling the driving of the actuator;
The motion assisting device according to claim 1, wherein the control device is disposed on a back surface portion of the wearing tool.   The motion assisting device according to claim 1, wherein the actuator is disposed on a front surface of a waist mounting portion of the mounting tool, and the battery device is disposed on a back surface of the waist mounting portion.   The operation assisting device according to claim 1, wherein the actuator is disposed on a front surface of the vest of the wearing tool, and the battery device is disposed on a rear surface of the vest.

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