WO2024174368A1

WO2024174368A1 - Electroadhesive device for manipulating flexible article

Info

Publication number: WO2024174368A1
Application number: PCT/CN2023/089390
Authority: WO
Inventors: Raymond Chiu; Andrew YEUNG; Leo CHOI
Original assignee: Hong Kong Research Institute of Textiles and Apparel Ltd
Current assignee: Hong Kong Research Institute of Textiles and Apparel Ltd
Priority date: 2023-02-22
Filing date: 2023-04-20
Publication date: 2024-08-29
Anticipated expiration: 2025-08-22
Also published as: CN120641341A

Abstract

An electroadhesive device (100) for manipulating a flexible article includes a gripping surface (110) for picking up the flexible article, a plurality of electrodes (120, 130) positioned on an inner side of the gripping surface (110), and a dielectric material (140) positioned between the electrodes (120, 130); a voltage difference between neighboring electrodes (120, 130) generates an electroadhesive force causing the flexible article to be adhered to the gripping surface (110); the gripping surface (110) includes a curved surface; the electroadhesive device (100) is able to roll on the flexible article or rotatable about an axis of rotation such that at least a portion of the flexible article can be wrapped on the curved surface.

Description

ELECTROADHESIVE DEVICE FOR MANIPULATING A FLEXIBLE ARTICLE

TECHNICAL FIELD

The present disclosure relates to electroadhesive devices and systems for manipulating a flexible article and methods for conveying a flexible article.

BACKGROUND

Textile industry is one of the largest manufacturing sectors globally. Despite having a huge market, textile industry is still labor intensive. Due to the complexity of fabric manipulation in the manufacturing process, the transition to full automation is slow. Textile industry is thus suffering from high factory cost.

Conventional robotic grippers typically use suction or actuator-driven mechanical grippers to pick up and move items. However, such grippers are not suitable for handling flexible articles. The difficulty of fabric manipulation lies in the high flexibility of the fabric. Thin and flexible fabrics are difficult to pick up piece by piece from a stack of fabrics with conventional grippers. In particular, conventional grippers may cause wrinkles and folds on the fabric and may damage the fabric when attempting to place the fabric in an accurate position on a working platform.

Electroadhesion is an electrically controllable adhesion mechanism that has been studied and used in various applications. Electroadhesion refers to the coupling of two objects using electrostatic forces. Electroadhesion uses electrical control of these electrostatic forces to permit temporary and detachable attachment between two objects. This electrostatic adhesion holds two surfaces of these objects together or increases the effective traction or friction between two surfaces due to electrostatic forces created by an applied electric field. Compared to other existing adhesion solutions, electroadhesion offers enhanced adaptability, reduced system complexity, low energy consumption, and is less-damaging to materials.

Electroadhesion based gripping systems have been developed recently to manipulate flexible articles. Most systems use a generally flat electroadhesive pad to pick up the flexible article. To avoid wrinkles and folds on the flexible article, the size of the flat electroadhesive pad needs to match the size of the flexible article. As a result, in order to handle flexible articles having a large size, manufacturers may need to build at least an equally large electroadhesion based gripping system, which could be very expensive.

Accordingly, there is a need to provide an alternative and improved way of handling flexible articles, which permits automatic picking, moving and positioning of thin and fragile items without the risk of causing unwanted marks and damages on the items.

SUMMARY

The present disclosure provides a novel electroadhesive gripping device and system for manipulating flexible articles which solves the aforementioned problems in conventional systems. The size and the cost of the gripping system can be reduced significantly. The gripping force can be controlled to ensure that the flexible article does not fall during the manipulation.

In a first aspect, an electroadhesive device for manipulating a flexible article is provided. The electroadhesive device can comprise a gripping surface for picking up the flexible article, a plurality of electrodes on an inner side of the gripping surface, and a dielectric material positioned between the electrodes. A voltage difference between neighboring electrodes can generate an electroadhesive force causing the flexible article to be adhered to the gripping surface. The gripping surface can comprise a curved surface. The electroadhesive device is able to roll on the flexible article or rotatable about an axis of rotation such that at least a portion of the flexible article can be wrapped on the curved surface.

In certain embodiments, the electroadhesive device can be in the form of a roller and the cross section of the gripping surface can be substantially circular. The plurality of electrodes can comprise positive electrodes and negative electrodes embedded in the dielectric material in an alternating manner. The electroadhesive device can comprise a protecting layer enclosing the positive electrodes, negative electrodes and the dielectric material. Alternatively, the gripping surface can comprise a substantially flat portion which smoothly transitions to the curved surface. The substantially flat portion can be configured to contact the flexible article prior to the curved surface.

In certain embodiments, at least a portion of the electroadhesive device can be deformable to increase an initial contacting area between the gripping surface and the flexible article. The electrodes can be removably mounted to the electroadhesive device. The gripping surface can be a rough surface for increasing the frictional force when the electroadhesive device is rolling on the flexible article.

In a second aspect, an electroadhesive system for conveying a flexible article is provided. The electroadhesive system can comprise a first gripper comprising at least one electroadhesive device, a second gripper comprising at least one electroadhesive device, a voltage source for applying voltage to the electrodes in the first and second grippers, a driving system for actuating the first and second grippers, and a controller for controlling the operation of the first and second grippers.

In certain embodiments, the first gripper can comprise a first electroadhesive roller and the second gripper can comprise a second electroadhesive roller. The first and second electroadhesive rollers can be oriented parallel to each other and are controlled separately. The first electroadhesive roller can be controlled to roll in one direction to pick up one edge of the flexible article. The second electroadhesive roller can be controlled to roll in the opposite direction to pick up the opposite edge of the flexible article. Each of the first and second electroadhesive rollers can comprise a sensor for detecting the wrapping area of the edge of the flexible article on the gripping surface.

In certain embodiments, the controller can comprise a rolling control unit for controlling the rolling distance or angle of rotation of the first and second electroadhesive rollers based on operating parameters selected from the group consisting of the number of electrodes in the first and second electroadhesive rollers, size of the first and second electroadhesive rollers, composition of the flexible article, thickness of the article material, density of the flexible article, and coefficient of friction of the flexible article. The controller can comprise a voltage control unit for controlling the voltage applied to the electrodes based on the properties of the flexible article and the parameters of the first and second electroadhesive rollers. The controller can comprise an edge detection unit for detecting the positions of the edges of the flexible article and assisting the alignment of the first and second electroadhesive rollers with the edges of the flexible article.

In a third aspect, a method of conveying a flexible article is provided. The method can comprise placing a first gripper in contact with a first edge of the flexible article, applying a first voltage to the electrodes in the first gripper to establish an electroadhesive adhesion between the first gripper and the first edge, rolling the first gripper in a first direction to cause a first portion of the flexible article near the first edge to be wrapped on the first gripper, placing a second gripper in contact with a second edge of the flexible article, applying a second voltage to the electrodes in the second gripper to establish an electroadhesive adhesion between the second gripper and the second edge, rolling the second gripper in a second direction opposite to the first direction to cause a second portion of the flexible article near the second edge to be wrapped on the second gripper, and moving the first and second grippers to a target location.

In certain embodiments, the rotational movement of the first and second electroadhesive rollers are disabled when the first and second electroadhesive rollers are being moved to a target location.

In certain embodiments, the first electroadhesive roller can be driven to roll on the flexible article by a first distance. The second electroadhesive roller can be driven to roll on the flexible article by a second distance. The first distance and second distance can be determined based on the operating parameters selected from the group consisting of the number of electrodes in the first and second electroadhesive rollers, size of the first and second electroadhesive rollers, composition of the flexible article, thickness of the article material, density of the flexible article, and coefficient of friction of the flexible article.

In certain embodiments, the method can comprise aligning the longitudinal axes of the first and second electroadhesive rollers with the first and second edges of the flexible article respectively. The alignment can be assisted by an edge detection unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of the invention, when taken in conjunction with the accompanying drawings, in which:

Fig. 1 shows the cross sectional view of an electroadhesive device according to one embodiment of the present disclosure.

Figs. 2A and 2B show the operation of an electroadhesive roller according to one embodiment of the present disclosure.

Figs. 3A and 3B show the operation of an electroadhesive roller according to another embodiment of the present disclosure.

Fig. 4 shows a functional block diagram of an electroadhesive system for conveying a flexible article according to one embodiment of the present disclosure.

Fig. 5 shows the arrangement of the first and second grippers in the electroadhesive system.

Fig. 6 shows a state when the electroadhesive rollers have picked up the flexible article.

Fig. 7 shows a flowchart of a method of conveying a flexible article according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is directed generally toward an electroadhesive device, system and method for conveying a flexible article. Fig. 1 shows an exemplary electroadhesive device in cross sectional view. The electroadhesive device 100 includes a gripping surface 110 for picking up a flexible article and a plurality of electrodes 120, 130 positioned on an inner side of the gripping surface 110. For purposes of illustration, the electroadhesive device 100 has a total of 12 electrodes forming six pairs. Each pair has a positive electrode 120 a negative electrode 130. It will be readily appreciated that more or fewer electrodes can be used in a given electroadhesive device. In certain embodiments, the positive electrodes and negative electrodes are embedded in a dielectric material 140 in an alternating manner on the inner side of the gripping surface 110. As shown in Fig. 1, the electrodes 120, 130 are arranged along the circumferential direction on the inner side of the gripping surface 110. Neighboring electrodes 120, 130 are separated by the dielectric material 140. The gap between neighboring electrodes 120, 130 can be selected based on the needs of a particular application.

When the electroadhesive device 100 is placed against or close to a surface of the flexible article, an electrostatic adhesion voltage can be applied to the electrodes. The electrostatic adhesion voltage causes positive and negative charges on neighboring electrodes which creates an electric field. Electrostatic adhesion voltage refers to a voltage that produces a suitable electrostatic force to couple the adjacent surfaces. The electrode pairs 120, 130 form electrical conductors in close proximity that generate alternating patterns of induced current flow. The electrode pairs 120, 130 are embedded in the dielectric material 140 so that the electric field between each of the electrode pairs induces charges in the dielectric material. An increase in the electric field results in an increase in charge density. When the electroadhesive device 100 is brought in contact with the flexible article, opposite charges are established in the surface of the flexible article by the same electric field. Since the charges are opposite, they create an attractive force therebetween. As a result, the flexible article is adhered to the gripping surface 110 of the electroadhesive device 100.

The voltage needed for the electroadhesive device 100 varies in relation to factors including the area of the gripping surface, the material conductivity, the gap between the electrode pairs, the dielectric material, the surface material of the flexible article, and also the operating environment conditions including temperature and humidity. In one embodiment, the electrostatic adhesion voltage includes a differential voltage between the electrode pairs 120, 130 that is between about 100 volts and about 10 kilovolts. The voltage on a single electrode may also be varied in time. The amount of electroadhesive force may be adjusted for example by varying the area of the contacting surfaces, varying the applied voltage, and/or varying the distance between the electrodes and flexible article.

The electroadhesive device 100 may include a protecting layer 150 enclosing the positive electrodes 120, negative electrodes 130 and the dielectric material 140. The protecting layer 150 is made of an insulating material.

Conventional electroadhesive devices usually include a gripping pad having a generally flat gripping surface for maximizing the area of contact between the gripping surface and the flexible article to be picked up. To avoid generating wrinkles and folds on the flexible article, the size of the flat electroadhesive pad needs to match the size of the flexible article. However, producing a large gripping pad is expensive and a single gripping pad may not be able to handle flexible articles of different sizes.

In the embodiment shown in Fig. 1, the gripper surface 110 includes a curved surface. The curved surface is efficient when handling thin and flexible sheets such as textile fabrics. The area of contact between the gripping surface and the flexible sheet can be increased by rolling or rotating the electroadhesive device which causes a larger portion of the flexible sheet to be wrapped on and adhered to the curved surface.

In one embodiment, the electroadhesive device 100 is in the form of a roller and the cross section of the gripping surface 110 is substantially circular. Roller having a larger diameter provides a larger area of contact between the gripping surface and the flexible article when the flexible article is wound on the roller. Length of the roller can be selected to match the size of the flexible article to be manipulated. In certain embodiments, the roller length can be larger than the length of the edge of the flexible article such that the full edge of the flexible article can be wrapped on the roller.

Fig. 2A and 2B show the operation of an electroadhesive roller 200. The electroadhesive roller 200 has a circular gripping surface 210 in cross sectional view with positive and negative electrodes embedded in a dielectric material in an alternating manner on an inner side of the gripping surface 210. The flexible article to be picked up is a fabric sheet 800. The fabric sheet 800 can be the uppermost one of a stack of fabric sheets. The fabric sheet 800 is generally rectangular in shape. The fabric sheet 800 has a first edge 801, a second edge 802, an upper surface 810 and a lower surface 820.

Fig. 2A shows a state when the electroadhesive roller 200 touches the upper surface 810 near the first edge 801. A voltage can be applied to the electrodes to generate an electroadhesive force between the gripping surface 210 and the fabric sheet 800. The electroadhesive force causes the first edge 801 to be adhered to the bottom portion 220 of the gripping surface 210. Then the electroadhesive roller 200 is driven to roll on the fabric sheet 800, thereby causing a larger portion of the fabric sheet 800 to be wrapped on the gripping surface 210. In certain embodiments, the gripping surface 210 can be a rough surface for increasing the frictional force between the gripping surface 210 and the upper surface 810 of the fabric sheet 800. Fig. 2B shows a state when half of the gripping surface 210 is covered by the fabric sheet 800. The first edge 801 is now on the top of the electroadhesive roller 200.

It should be noted that a direct surface to surface contact is not always required. For example, when the electroadhesive roller 200 is placed in close proximity to the fabric sheet 800, the electroadhesive force can still attract the fabric sheet 800. Then the electroadhesive roller 200 can be driven to rotate to cause a larger portion of the fabric sheet 800 to be wrapped on the gripping surface 210.

While Fig. 2A and 2B show an electroadhesive roller 200 having a circular gripping surface 210, it will be appreciated that various alternative designs of the electroadhesive device can be used. For example, the cross sectional shape of the gripping surface may be elliptical or semicircular. To avoid damaging the flexible article, it is preferred to avoid corners or abrupt changes on the gripping surface.

In certain embodiments, the gripping surface may include a substantially flat portion which smoothly transitions to the curved surface. Figs. 3A and 3B show an electroadhesive roller 300 having a racetrack shaped gripping surface 310. The gripping surface 310 includes a flat portion 330 which smoothly transitions to a curved surface 320. The flat portion 330 can be provided at the bottom of the electroadhesive device 300 such that the flat portion 330 always contacts and picks up the flexible article 800 prior to the curved surface 320. Fig. 3B shows a state when both of the flat portion 330 and the curved surface 320 are covered by the fabric sheet 800.

Further, it is also contemplated that at least a portion of the electroadhesive device, for example the lower portion, can be made deformable. When the electroadhesive device is placed against the flexible article, an external force can be applied to the electroadhesive device to cause its lower portion to deform. Deformation of the lower portion allows the bottom part of the gripping surface to conform to the surface of the flexible article. As a result, the initial contacting area between the gripping surface and the flexible article can be increased.

In certain embodiments, the electrodes are removably mounted in the electroadhesive device. Electrodes may be in the form of bars, rods or panels extending in the longitudinal direction of the electroadhesive device. Electrodes may be inserted into the channels formed in the dielectric material. Removable electrodes facilitate the replacement and maintenance of the device.

Rolling motion of the electroadhesive device can be considered as a combination of translational motion and rotational motion where the point of contact is instantaneously at rest. The rotational motion can be generated by an actuator, such as an electric motor. In one embodiment, the electroadhesive device may include a hole or recess for receiving a drive shaft coupled to the actuator. The gripping surface of the electroadhesive device can be a rough surface for increasing the frictional force between the gripping surface and the flexible sheet. Further, a downward force may be applied to press the electroadhesive device against the flexible sheet. The rotational speed of the drive shaft and the downward force can be controlled during the rolling motion to ensure that the flexible sheet is wrapped on the gripping surface.

Fig. 4 shows a functional block diagram of an exemplary electroadhesive system for conveying a flexible article according to one embodiment of the present disclosure. The electroadhesive conveying system 500 includes a first gripper 510 and a second gripper 520. Each of the two grippers 510, 520 may include one or more electroadhesive devices as described above. A support structure may be provided for supporting the first and second grippers 510, 520. A voltage source 530 is provided for applying voltage to the electrodes in the first and second grippers 510, 520. In certain embodiments, a power supply is used to provide alternating current voltage or direct current voltage.

The electroadhesive conveying system 500 further includes a driving system 540 for actuating the first and second grippers 510, 520. The driving system 540 may include multiple driving modules, including a first gripping module for generating a rolling or rotational motion of the first gripper, a first conveying module for generating a translational motion of the first gripper, a second gripping module for generating a rolling or rotational motion of the second gripper, and a second conveying module for generating a translational motion of the second gripper. The driving modules may be controlled by a controller 550, which determines and controls the rolling distance, angle of rotation, rotational speed, translational speed and/or target location of the first and second grippers 510, 520.

Fig. 5 shows an exemplary arrangement of the first and second grippers 510, 520. The first gripper 510 includes a first electroadhesive roller 511 and the second gripper 520 includes a second electroadhesive roller 521. The first and second electroadhesive rollers 511, 521 are spaced apart and oriented parallel to each other. During operation, the first electroadhesive roller 511 is controlled to roll in one direction to pick up one edge 801 of the flexible article 800, and the second electroadhesive roller 521 is controlled to roll in the opposite direction to pick up the opposite edge 802 of the flexible article 800. Fig. 6 shows a state when the electroadhesive rollers 511, 521 have picked up the edges 801, 802 of the flexible article 800.

In other embodiments, the electroadhesive conveying system 500 may include more than two grippers. For example, four electroadhesive rollers may be used to pick up four edges of a rectangular fabric sheet.

Each electroadhesive roller 511, 521 may be provided with a sensor 512, 522 for detecting the wrapping area of the flexible article on the roller surface. Various different types of sensors can be used, including electronic sensor, optical sensor, and pressure sensor. In one embodiment, the controller may stop the rolling motion if it is detected that over a half of the roller surface is covered by the flexible article.

The generated gripping force may be affected by multiple factors, including the voltage applied, the arrangement of electrodes in the electroadhesive roller, the wrapping area, and the material of the flexible article. The controller 550 may include a voltage control unit 552 for controlling the voltage applied to the electrodes based on the properties of the flexible article and the parameters of the electroadhesive roller. The controller 550 may also include a rolling control unit 551 for controlling the rolling distance or angle of rotation of the electroadhesive rollers based on various operating parameters. The operating parameters may include the number of electrodes in the first and second electroadhesive rollers, the arrangement pattern of the electrodes, size (diameter and length) of the first and second electroadhesive rollers, composition of the flexible article, thickness of the article material, density of the flexible article, and coefficient of friction of the flexible article.

In one embodiment, the electroadhesive conveying system 500 may include a user interface 560 which allows user to input the location information of the flexible article to be conveyed, set the properties of the flexible article, and/or choose a specific operation mode among multiple preset modes stored in the controller 550.

It is important for the electroadhesive conveying system 500 to know the accurate location of the flexible article 800. The controller 550 can control the driving system 540 to move the first and the second electroadhesive rollers 511, 521 to the correct position to pick up the flexible article. In one embodiment, the user interface allows user to manually set the position of the flexible article. Alternatively or additionally, the controller 550 may include an edge detection module 553 for detecting the position of the flexible article, in particular, the position of the edges of the flexible article. The edge detection module 553 may also assist the driving system 540 to align the first and second electroadhesive rollers 511, 521 with the edges 801, 802 of the flexible article 800. The edge detection module may include a computer vision system, optical sensors, ultrasonic sensors, or any other sensor that can detect the edges of the flexible article.

In another embodiment, the electroadhesive roller 511, 521 can be formed by connecting multiple roller segments together. All roller segments may share the same cross sectional shape and may be configured to be driven by the same actuator. The number of roller segments can be selected to match the edge length of the flexible article to be conveyed. This is particularly advantageous when the system is used to convey flexible articles having different sizes, including very large fabric sheets.

Fig. 7 shows a flowchart of a method 600 of conveying a flexible article according to one embodiment of the present disclosure. The method 600 can be performed by the electroadhesive conveying system 500 as shown in Fig. 4. In step 601, information of the location of the flexible article 800 is gathered. The location information can be set by user via the user interface 560 or detected by sensors or computer vision system of the edge detection module 553. The location information includes information of the two edges 801, 802 of the flexible article 800.

In step 602, a first gripper 510 is aligned with a first edge 801 of the flexible article 800. The first gripper may include at least one electroadhesive device as described above, such as an electroadhesive roller having a circular cross section. The first gripper can be moved by a driving system 540. Alignment between the longitudinal axis of the first gripper and the first edge can be assisted by an edge detection unit 553.

In step 603, the first gripper is placed in contact with the first edge of the flexible article. The first gripper can be lowered by the driving system until it touches the surface of the flexible article.

In step 604, a voltage is applied to the electrodes in the first gripper to establish an electroadhesive adhesion between the first gripper and the first edge. The voltage can be controlled based on the properties of the flexible article and the parameters of the first gripper. A signal can be sent to the controller once the first edge is firmly adhered to the gripping surface of the first gripper.

In step 605, the first gripper is rolled in a first direction to cause a first portion of the flexible article near the first edge to be wrapped on the gripping surface of the first gripper. The rolling distance can be controlled based on the number of electrodes in the first gripper, arrangement pattern of the electrodes, size of the first gripper, composition of the flexible article, thickness of the article material, density of the flexible article, and coefficient of friction of the flexible article. In one embodiment, the wrapping area of the first edge on the gripping surface is detected. The detected wrapping area can help the controller to determine whether the first gripper has rolled the correct distance.

In step 606, a second gripper 520 is aligned with a second edge 802 of the flexible article 800. The second gripper may also include at least one electroadhesive device as described above, such as an electroadhesive roller having a circular cross section. Similar to step 602, alignment between the longitudinal axis of the second gripper and the second edge can be assisted by the edge detection unit.

In step 607, the second gripper is placed in contact with the second edge of the flexible article. The second gripper can be lowered by the driving system until it touches the surface of the flexible article.

In step 608, a voltage is applied to the electrodes in the second gripper to establish an electroadhesive adhesion between the second gripper and the second edge. The voltage can be controlled based on the properties of the flexible article and the parameters of the second gripper. A signal can be sent to the controller once the second edge is firmly adhered to the surface of the second gripper.

In step 609, the second gripper is rolled in a second direction opposite to the first direction to cause a second portion of the flexible article near the second edge to be wrapped on the gripping surface of the second gripper. The rolling distance can be controlled based on the number of electrodes in the second gripper, arrangement pattern of the electrodes, size of the second gripper, composition of the flexible article, thickness of the article material, density of the flexible article, and coefficient of friction of the flexible article. In one embodiment, the wrapping area of the second edge on the gripping surface is detected. The detected wrapping area can help the controller to determine whether the second gripper has rolled the correct distance.

It will be appreciated that the first and second grippers can be controlled separately. In one embodiment, steps 602 to 605 and steps 606 to 609 can be performed at the same time to increase the efficiency of the gripping operation.

In step 610, the first and second grippers carrying two edges of the flexible article are moved to the target location. It is preferred that the distance between the two grippers remains the same in step 610 to avoid stretching the flexible article and to prevent wrinkles and folds. Rotation and rolling of the grippers also need to be avoided.

When the flexible article reaches the target location, the voltage applied to the electrodes in the first and second grippers can be reduced to release the two edges of the flexible article from the gripping surfaces. In certain embodiments, the target location can be a working platform.

Although the disclosed subject matter has been described and illustrated in the foregoing exemplary embodiments, it is understood that the present disclosure has been made only by way of example, and that various changes in the details of implementation of the disclosed subject matter may be made without departing from the spirit and scope of the disclosed subject matter. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more other features of the other embodiments as may be desired and advantageous for any given or particular application.

Claims

An electroadhesive device for manipulating a flexible article, comprising:

a gripping surface for picking up the flexible article;

a plurality of electrodes positioned on an inner side of the gripping surface; and

a dielectric material positioned between the electrodes;

wherein a voltage difference between neighboring electrodes generates an electroadhesive force causing the flexible article to be adhered to the gripping surface;

wherein the gripping surface comprises a curved surface, and the electroadhesive device is able to roll on the flexible article or rotatable about an axis of rotation such that at least a portion of the flexible article can be wrapped on the curved surface.
The electroadhesive device according to claim 1, wherein the plurality of electrodes comprises positive electrodes and negative electrodes embedded in the dielectric material in an alternating manner, and the electroadhesive device comprises a protecting layer enclosing the positive electrodes, negative electrodes and the dielectric material.
The electroadhesive device according to claim 1 or 2, wherein the electroadhesive device is in the form of a roller and the cross section of the gripping surface is substantially circular.
The electroadhesive device according to claim 1 or 2, wherein the gripping surface comprises a substantially flat portion which smoothly transitions to the curved surface, the substantially flat portion is configured to contact the flexible article prior to the curved surface.
The electroadhesive device according to claim 1 or 2, wherein at least a portion of the electroadhesive device is deformable to increase an initial contacting area between the gripping surface and the flexible article.
The electroadhesive device according to any one of claims 1 to 5, wherein the electrodes are removably mounted to the electroadhesive device.
The electroadhesive device according to any one of claims 1 to 6, wherein the gripping surface is a rough surface for increasing the frictional force when the electroadhesive device is rolling on the flexible article.
The electroadhesive device according to any one of claims 1 to 7, wherein the electroadhesive device is driven to roll or rotate by an actuator, and the electroadhesive device comprises a hole or recess for receiving a drive shaft coupled to the actuator.
An electroadhesive system for conveying a flexible article, comprising:

a first gripper comprising at least one electroadhesive device according to any one of claims 1 to 8;

a second gripper comprising at least one electroadhesive device according to any one of claims 1 to 8;

a voltage source for applying voltage to the electrodes in the first and second grippers;

a driving system for actuating the first and second grippers; and

a controller for controlling the operation of the first and second grippers.
The electroadhesive system according to claim 9, wherein the first gripper comprises a first electroadhesive roller and the second gripper comprises a second electroadhesive roller, the first and second electroadhesive rollers are oriented parallel to each other and are controlled separately.
The electroadhesive system according to claim 10, wherein the first electroadhesive roller is controlled to roll in one direction to pick up one edge of the flexible article, and the second electroadhesive roller is controlled to roll in the opposite direction to pick up the opposite edge of the flexible article.
The electroadhesive system according to claims 10 or 11, wherein each of the first and second electroadhesive rollers comprises a sensor for detecting the wrapping area of the edge of the flexible article on the gripping surface.
The electroadhesive system according to any one of claims 9 to 12, wherein the controller comprises a rolling control unit for controlling the rolling distance or angle of rotation of the first and second electroadhesive rollers based on operating parameters selected from the group consisting of the number of electrodes in the first and second electroadhesive rollers, size of the first and second electroadhesive rollers, composition of the flexible article, thickness of the article material, density of the flexible article, and coefficient of friction of the flexible article.
The electroadhesive system according to any one of claims 9 to 13, wherein the controller comprises a voltage control unit for controlling the voltage applied to the electrodes based on the properties of the flexible article and the parameters of the first and second electroadhesive rollers.
The electroadhesive system according to any one of claims 9 to 14, further comprising a user interface for user to input the location information of the flexible article to be conveyed, set the properties of the flexible article, and/or choose a specific operation mode among multiple preset modes stored in the controller.
The electroadhesive system according to any one of claims 9 to 15, wherein the controller comprises an edge detection unit for detecting the positions of the edges of the flexible article and assisting the alignment of the first and second electroadhesive rollers with the edges of the flexible article, wherein the edge detection unit comprises one or more sensors or an AI-based computer vision system.
The electroadhesive system according to claim 9, wherein the first gripper and/or second gripper comprises multiple electroadhesive devices, the electroadhesive devices are connected together and configured to be driven by the same actuator during operation, preferably, the number of electroadhesive devices in the first gripper and/or second gripper is selected to match the size of the flexible article to be conveyed.
A method of conveying a flexible article, comprising:

placing a first gripper in contact with a first edge of the flexible article, wherein the first gripper comprises at least one electroadhesive device according to any one of claims 1 to 8;

applying a first voltage to the electrodes in the first gripper to establish an electroadhesive adhesion between the first gripper and the first edge;

rolling the first gripper in a first direction to cause a first portion of the flexible article near the first edge to be wrapped on the first gripper;

placing a second gripper in contact with a second edge of the flexible article, wherein the second gripper comprises at least one electroadhesive device according to any one of claims 1 to 8;

applying a second voltage to the electrodes in the second gripper to establish an electroadhesive adhesion between the second gripper and the second edge;

rolling the second gripper in a second direction opposite to the first direction to cause a second portion of the flexible article near the second edge to be wrapped on the second gripper; and

moving the first and second grippers to a target location.
The method of conveying a flexible article according to claim 18, wherein the first gripper comprises a first electroadhesive roller and the second gripper comprises a second electroadhesive roller, the first and second electroadhesive rollers are oriented in parallel with each other, and the first and second edges of the flexible article are opposite to each other.
The method of conveying a flexible article according to claim 19, wherein the rotational movement of the first and second electroadhesive rollers are disabled when the first and second electroadhesive rollers are being moved to a target location.
The method of conveying a flexible article according to claim 19 or 20, wherein:

the step of rolling the first gripper in a first direction comprises driving the first electroadhesive roller to roll on the flexible article by a first distance; and

the step of rolling the second gripper in a second direction comprises driving the second electroadhesive roller to roll on the flexible article by a second distance;

wherein the first distance and second distance are determined based on the operating parameters selected from the group consisting of the number of electrodes in the first and second electroadhesive rollers, size of the first and second electroadhesive rollers, composition of the flexible article, thickness of the article material, density of the flexible article, and coefficient of friction of the flexible article.
The method of conveying a flexible article according to any one of claims 19 to 21, further comprising:

before the step of applying a first voltage to the electrodes in the first gripper, aligning the longitudinal axis of the first electroadhesive roller with the first edge of the flexible article; and

before the step of applying a second voltage to the electrodes in the second gripper, aligning the longitudinal axis of the second electroadhesive roller with the second edge of the flexible article,

wherein alignment of the first and second electroadhesive rollers is assisted by an edge detection unit.