Introduction
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We propose an effective way, which introduces a cylindrical brush, for picking up thin sheets of fabric that easily adhere together.
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We designed the hardware to realize the proposed picking up method and devised an appropriate manipulation procedure.
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We evaluate the effectiveness of the proposed end-effector by performing the picking procedure using an actual robot system with a vision sensor.
Related work
Mechanical hardware for garment picking
Cloth manipulation system
Problem settings and our concept
Problem settings
Hardware concept
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Do not damage the cloth or attach liquids to it during picking up. It should be a method that does not apply excessive force to cloth.
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The end-effector must be small enough not to interfere with the supply of fabric to sewing machines. Also, it is desired not to move manipulators unnecessarily during picking up the cloth. For example, after the end-effector is brought into contact with a cotton sheet, the sheet can be held only by the movement inside the end-effector.
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Suitable for repetitive work. In other words, even the case that a large number of cotton sheets are stacked, it is possible to continue picking up only the top cotton sheet without significantly affecting the state of the remaining sheets.
The end-effector for rolling up a cloth sheet
Overview
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Cylindrical brush: It is a cylindrical part that is actively rotated by an actuator. Two cylinders are attached to one rotating shaft, and it is placed at the bottom of the end effector. ’Remover cloth’ is attached to the surface of the cylinders. The end-effector is approached from directly above to a cotton sheet placed on a horizontal table, and then the sheet is rolled up by utilizing the fact that the brush and the cotton sheet adhere. Details of this part are explained in the next sub-section.
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Actuator: The end-effector is operated by one unit of Dynamixel AX-18 (holding torque 1.8 N\(\cdot \)m, no-load rotation speed 97rpm) manufactured by Best Technology Inc. Since this actuator is small and lightweight, it can be embedded inside the end-effector.
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Driving force transmission section: The driving force from the actuator is transmitted to the cylindrical brush via a timing belt, gears, and pulleys. This timing belt is located in the center of the end-effector and rotates the two brushes. At the same time, the end-effector body is moved horizontally in the front-rear direction. This mechanism will be explained in detail in the final sub-section of this section.
Cylindrical brush
z: gear and pulley teeth | PD: pitch diameter [mm] | |
---|---|---|
Gear 1 | 20 | 20 |
Gear 2 | 24 | 24 |
Pulley 1 | 18 | – |
Pulley 2 | 16, 24, 32 | – |
Pulley 3 | 32 | – |
Pulley 4 | 16 | – |
Pulley 5 | 18 | – |
Horizontal movement mechanism associated with brush rotation
Fundamental experiments
Examination of gear ratio
No. of teeth | 32 | 24 | 16 |
---|---|---|---|
(a) | 3 | 4 | 17 |
(b) | 3 | 9 | 7 |
(c) | 2 | 1 | 1 |
(d) | 5 | 5 | 0 |
(e) | 1 | 1 | 0 |
(f) | 2 | 0 | 0 |
No. of action (N) | 16 | 20 | 25 |
Pick up success rate | 62.5% | 70% | 100% |
Release success rate | 75% | 92% | 96% |
Overall success rate | 24% | 52% | 96% |
Surface material of the cylindrical brush
No. of teeth | 32 | 24 | 16 |
---|---|---|---|
(a) | 0 | 0 | 0 |
(b) | 0 | 0 | 0 |
(c) | 1 | 7 | 0 |
(d) | 8 | 6 | 10 |
(e) | 0 | 0 | 0 |
(f) | 0 | 0 | 0 |
Verification experiments
Fabric (1) | Fabric (2) | Fabric (3) | |
---|---|---|---|
(a) | 48 | 49 | 15 |
(b) | 0 | 0 | 0 |
(c) | 2 | 1 | 15 |
(d) | 0 | 0 | 10 |
(e) | 0 | 0 | 0 |
(f) | 0 | 0 | 0 |
No. of action | 50 | 50 | 40 |
Pick up success rate | 100% | 100% | 75% |
Release success rate | 96% | 98% | 50% |
Overall success rate | 96% | 98% | 33.3% |