Soft manipulator with flexible sensing and variable stiffness characteristics

Abstract

The application discloses a soft manipulator with flexible sensing and variable stiffness characteristics, solves the problems that a rigid manipulator is difficult to perform the task of grabbing fragile objects, and a soft manipulator has small gripping force and it is difficult for the soft manipulator to embed a sensor to perceive the external environment. Specifically, the soft manipulator comprises a mounting base and N fingers uniformly distributed on the same side of the mounting base, wherein N is a positive integer greater than or equal to 1; the mounting base is provided with N air pipe joints, the air pipe joints are provided with positive pressure air holes and negative pressure air holes; the N fingers correspond to the N air pipe joints one by one; the finger comprises a soft cavity and a variable stiffness cavity connected together; the soft cavity is in communication with the positive pressure air hole; the variable stiffness cavity is in communication with the negative pressure air hole; one side of the soft cavity and the variable stiffness cavity is planar, and the side away from the variable stiffness cavity is serrated or corrugated; the variable stiffness cavity is provided with a plurality of interference layers stacked with each other, and a flexible sensing layer is arranged between two adjacent interference layers.

Description

Technical Field

[0001] This invention relates to soft robotic hands, specifically to a soft robotic hand that combines flexible sensing and variable stiffness characteristics. Background Technology

[0002] Robotic arms, also known as end effectors, are crucial components of robots. Existing robotic arms primarily fall into two categories: rigid robotic arms and soft robotic arms. Rigid robotic arms offer high output force, relatively high precision, and ease of control, but lack environmental adaptability and interaction safety. Soft robotic arms, on the other hand, are mainly composed of flexible materials, possessing greater degrees of freedom and flexibility, exhibiting excellent compliance and adaptability to complex environments. Compared to traditional rigid robotic arms, soft robotic arms offer unparalleled advantages in human-robot interaction, grasping complex and fragile objects, and operating in confined spaces, thus demonstrating broad application prospects.

[0003] While rigid robotic arms offer great strength and precision, they are ill-suited for grasping fragile objects. Soft robotic arms, on the other hand, while possessing excellent flexibility and dexterity, suffer from drawbacks such as weak gripping force, poor rigidity, and low load capacity. Existing soft robotic arms are ineffective when dealing with large, irregularly shaped objects. Furthermore, due to the inherent flexibility and significant deformation of their materials, existing soft robotic arms struggle to incorporate sensors to detect changes in the external environment. Summary of the Invention

[0004] The purpose of this invention is to provide a soft robotic hand that combines flexible sensing and variable stiffness characteristics, in order to solve the technical problems that rigid robotic hands are unable to handle the task of grasping fragile items, while soft robotic hands have low gripping force, poor stiffness, low load, and it is difficult to embed sensors in soft robotic hands to sense changes in the external environment.

[0005] To achieve the above objectives, the present invention provides

[0006] A soft robotic hand that combines flexible sensing and variable stiffness characteristics is characterized by: including a mounting base for connecting to an external robotic arm and N fingers evenly distributed on the same side of the mounting base, where N is a positive integer greater than or equal to 1.

[0007] The mounting base is provided with N air pipe connectors, each air pipe connector having a positive pressure air port for connecting to a positive pressure air source and a negative pressure air port for connecting to a negative pressure air source; the N fingers correspond one-to-one with the N air pipe connectors;

[0008] The fingers comprise elongated, interconnected soft cavities and variable stiffness cavities; the soft cavities are connected to positive pressure air vents; the variable stiffness cavities are connected to negative pressure air vents.

[0009] The side of the soft cavity connected to the variable stiffness cavity is planar, while the side away from the variable stiffness cavity is serrated or corrugated, and the serrations or corrugations are arranged along the length direction of the soft cavity.

[0010] The variable stiffness cavity is provided with multiple layers of interference layers stacked on top of each other, and a flexible sensing layer is provided between a pair of adjacent interference layers; the flexible sensing layer is electrically connected to an external control board.

[0011] Furthermore, the flexible sensing layer is a piezoelectric polyvinylidene fluoride film.

[0012] Furthermore, a microstructure layer is provided between the flexible sensing layer and one of the adjacent interference layers;

[0013] The microstructure layer is adhered to the flexible sensing layer, and multiple protrusions are provided on the side of the microstructure layer near the flexible sensing layer.

[0014] Furthermore, the multi-layered interference layers are divided into two groups, namely a multi-layered first interference layer and a multi-layered second interference layer; one end of the first interference layer is connected to the end of the variable stiffness cavity near the mounting base; one end of the second interference layer is connected to the end of the variable stiffness cavity away from the mounting base; the other ends of the multi-layered first interference layer and the other ends of the multi-layered second interference layer are staggered and stacked in the middle of the variable stiffness cavity.

[0015] The plane containing the first and second interference layers is parallel to the connection plane between the soft cavity and the variable stiffness cavity.

[0016] The flexible sensing layer is disposed in the middle of the variable stiffness cavity and is located between a first interference layer and an adjacent second interference layer.

[0017] Furthermore, within the variable stiffness cavity, a first mounting base is provided at one end near the mounting base, and a second mounting base is provided at the other end away from the mounting base;

[0018] Multiple first-layer blocking layers are arranged side by side on the first mounting base along the direction away from the soft cavity, and a first interference layer is arranged between each two adjacent first-layer blocking layers;

[0019] The second mounting base has multiple second-layer blocking structures arranged side by side along the direction away from the soft cavity, and a second interference layer is arranged between each two adjacent second-layer blocking structures.

[0020] Furthermore, both the first interference layer and the second interference layer are made of fiberglass or paper.

[0021] Furthermore, the mounting base includes a base and an upper cover plate mounted on the base;

[0022] An installation cavity is provided between the base and the upper cover plate;

[0023] One end of the endotracheal connector is connected to the flexible cavity and the variable stiffness cavity respectively, and the other end passes through the base and extends into the mounting cavity, and is fixed by a nut located in the mounting cavity.

[0024] The upper cover plate has a flange in the middle for connecting an external robotic arm;

[0025] The flange is provided with a through hole for connecting the air pipe connector to a positive pressure air source and a negative pressure air source.

[0026] Furthermore, a limiting bushing is also fitted onto the tracheal connector;

[0027] The limiting bushing is located between the base and the finger.

[0028] Furthermore, the soft cavity and the variable stiffness cavity are made of silicone casting.

[0029] Furthermore, N=3, and the three fingers are evenly distributed around the central axis of the mounting base; the side of the variable stiffness cavity in each finger that is away from the soft cavity faces the extension line of the central axis of the mounting base.

[0030] The beneficial effects of this invention are:

[0031] 1. The soft robotic hand of the present invention is configured with fingers that combine a soft cavity and a variable stiffness cavity. One side of the soft cavity is flat, and the other side is serrated or corrugated, so that it can bend to one side when filled with gas to grasp objects. Multiple interference layers and a flexible sensing layer are also set in the variable stiffness cavity. When air is pumped out, the friction generated between the various interference layers can be used to increase the structural stiffness of the variable stiffness cavity. At the same time, the hardness of the object to be grasped can be obtained through the flexible sensing layer, so that the external control board can control the amount of air pumped into the variable stiffness cavity to adapt to objects of different hardness. The combination of the two can not only flexibly grasp fragile items, ensure the stability of grasping, and increase the maximum grasping load, but also sense the external environment through the flexible sensing layer, thereby realizing feedback adjustment.

[0032] 2. The present invention provides a microstructure layer with multiple protrusions on one side of the flexible sensing layer. The microstructure layer is adhered to the flexible sensing layer, which not only serves as a component of the variable stiffness structure, but also improves the sensitivity of the flexible sensing unit.

[0033] 3. The present invention divides the multi-layer interference layer into a multi-layer first interference layer and a multi-layer second interference layer, and fixes one end of the first interference layer and one end of the second interference layer respectively, so that the other ends of the two are stacked in an alternating manner; thus, the overall structure of the variable stiffness cavity is uniform and orderly, and the stiffness change is smooth.

[0034] 4. The mounting base of the present invention has a simple structure. The mounting cavity and the through holes on the flange provide space and through holes for the connection pipelines of the positive pressure air source and the negative pressure air source, as well as the connection lines of the flexible sensing layer, making the entire robot arm look neat and beautiful.

[0035] 5. The present invention also provides a limiting sleeve between the base and the finger to prevent the finger from passing through the base and to facilitate the installation of the finger.

[0036] 6. The soft cavity and variable stiffness cavity of the present invention are made of silicone casting, which is simple and efficient to manufacture.

[0037] 7. The control medium used in this invention is gas, which is pollution-free and requires only two gas sources: one to provide positive pressure for the gripping process and the other to provide negative pressure for the variable stiffness process. The operation is simple and convenient.

[0038] 8. The present invention embeds a flexible sensor between the interference layers in the variable stiffness cavity, which has a composite function. It can not only make the structure compact and the integration higher, but also sense the external environment and realize the interaction between the robot and the external environment. Attached Figure Description

[0039] Figure 1 This is a schematic diagram (partial cross-section) of an embodiment of a soft manipulator with both flexible sensing and variable stiffness characteristics according to the present invention.

[0040] Figure 2 This is an exploded view of a soft robotic hand that combines flexible sensing and variable stiffness characteristics according to the present invention.

[0041] Figure 3 This is a partial cross-sectional view of a finger in an embodiment of the present invention;

[0042] Figure 4 yes Figure 3 Enlarged view of point A in the middle;

[0043] Figure 5 This is a schematic diagram of the flexible state structure of the variable stiffness cavity in an embodiment of the present invention when it is not evacuated;

[0044] Figure 6 This is a schematic diagram of the rigid state structure of the variable stiffness cavity after it has been evacuated in an embodiment of the present invention.

[0045] Figure 7 This is a schematic diagram of the feedback control principle of the robotic arm in an embodiment of the present invention.

[0046] Icon labels:

[0047] 1-Top cover plate, 2-Flange, 3-Base, 4-Soft cavity, 5-Variable stiffness cavity, 51-First mounting seat, 511-First layer of blockage, 52-Second mounting seat, 521-Second layer of blockage, 6-Microstructure layer, 7-Flexible sensing layer, 8-Interference layer, 81-First interference layer, 82-Second interference layer, 9-Air pipe connector, 10-Nut, 11-Limiting bushing, 12-Bolt. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] A soft robotic hand that combines flexible sensing and variable stiffness characteristics, such as Figure 1 As shown, the robotic arm includes a mounting base and N fingers evenly distributed on the same side of the mounting base, where N is a positive integer greater than or equal to 1. In this embodiment, N = 3. In other embodiments, the number of fingers can be more or less, and can be selected according to the actual situation.

[0050] like Figure 2 As shown, the mounting base includes a base 3 and an upper cover plate 1 that is bolted to the base 3 by bolts 12; an mounting cavity is provided between the base 3 and the upper cover plate 1, which can be used to accommodate connecting air tubes and connecting lines; the base 3 is provided with three air tube connectors 9, which correspond one-to-one with three fingers, and the three fingers are evenly distributed around the center line of the mounting base; a limiting sleeve 11 is also fitted on the air tube connector 9; the limiting sleeve 11 is located between the base 3 and the fingers to restrict the axial movement of the soft fingers. The tracheal connector 9 is provided with a positive pressure air port for connecting a positive pressure air source and a negative pressure air port for connecting a negative pressure air source; one end of each tracheal connector 9 is connected to the corresponding finger, and the other end extends from the side of the base 3 away from the upper cover plate 1 through the base 3 into the mounting cavity, and is fixed by a nut 10 located in the mounting cavity; the upper cover plate 1 is provided with a flange 2 in the middle for connecting to the end of an external robotic arm; the flange 2 is provided with multiple through holes for connecting the tracheal connector 9 to the positive pressure air source and the negative pressure air source, and the through holes can also be used as wire passage holes.

[0051] Combination Figures 3-6As shown, each finger comprises a long, connected, flexible cavity 4 and a variable stiffness cavity 5. The side of the variable stiffness cavity 5 in each finger away from the flexible cavity 4 faces the extended centerline of the mounting base. Both the flexible cavity 4 and the variable stiffness cavity 5 are cast from silicone and are sealed chambers. The flexible cavity 4 is connected to a positive pressure air port on the air pipe connector 9 via a positive pressure air pipe. The variable stiffness cavity 5 is connected to a negative pressure air port on the air pipe connector 9 via a negative pressure air pipe. The side of the flexible cavity 4 connected to the variable stiffness cavity 5 is planar, while the side away from the variable stiffness cavity 5 is serrated or corrugated, with the serrations or corrugations extending along the flexible cavity. The length direction of 4 is set so that the sawtooth or corrugated parts are multiple identical chambers, which increases the surface area of ​​one side of the soft cavity 4. When a certain pressure of gas is filled into the soft cavity, the soft cavity will bend towards the side with smaller surface area (i.e., the planar side) due to the strain difference between the two sides of the soft cavity 4. The variable stiffness cavity 5 is provided with multiple layers of interference layers 8 stacked on each other. The interlayer interference structure can generate high resistance to external interference by utilizing the friction between the overlapping layers with negative pressure. Therefore, the multiple layers of interference layers 8 are squeezed against each other under the action of negative pressure, and friction is generated between each layer, thereby increasing the stiffness of the entire structure. The multi-layer interference layer 8 is divided into two groups: a multi-layer first interference layer 81 and a multi-layer second interference layer 82. Within the variable stiffness cavity 5, a first mounting base 51 is provided at one end near the mounting base, and a second mounting base 52 is provided at the other end away from the mounting base. Multiple first-layer blocking layers 511 are arranged side-by-side on the first mounting base 51 along the direction away from the soft cavity 4, with a first interference layer 81 between each two adjacent first-layer blocking layers 511 to connect one end of each first interference layer 81. Multiple second-layer blocking layers 521 are arranged side-by-side on the second mounting base 52 along the direction away from the soft cavity 4, with each two adjacent second-layer blocking layers 521... A second interference layer 82 is disposed between layers 21, connecting one end of each second interference layer 82; the other ends of the multiple first interference layers 81 and the multiple second interference layers 82 are staggered and stacked in the middle of the variable stiffness cavity 5; a flexible sensing layer 7 and a microstructure layer 6 are disposed between one first interference layer 81 and the adjacent second interference layer 82, and are adhered together. The microstructure layer 6 has multiple conical protrusions on the side near the flexible sensing layer 7. The microstructure layer 6 and the flexible sensing layer 7 are adhered together, which not only acts as a component of the variable stiffness structure, but also improves the sensitivity of the flexible sensing unit. The flexible sensing layer 7 is disposed in the middle of the variable stiffness cavity 5. The flexible sensing layer 7 is a piezoelectric polyvinylidene fluoride film (PVDF), which is a passive sensor. This passive sensor can detect curvature changes, sense the surface hardness of the object to be grasped, and transmit the information to an external control board connected to it, thereby providing feedback adjustment to the negative pressure air source and realizing the interaction between the soft manipulator and the external environment. Both the first interference layer 81 and the second interference layer 82 are made of fiber glass or paper. In this embodiment, the positive pressure gas source can be an air pump, and the negative pressure gas source can be a vacuum pump.When a robotic arm needs to handle objects that require friendly interaction, the combination of variable stiffness and stiffness sensing can provide robust gripping and safe control.

[0052] The robotic arm provided in this embodiment of the invention is a soft robotic arm that combines flexible sensing and variable stiffness characteristics, and its working principle is as follows:

[0053] When the air pump is connected to the positive pressure tube, the flexible cavity 4 will bend inward to achieve the grasping action;

[0054] When the vacuum pump is connected to the negative pressure pipe, the multi-layer interference layer 8, the flexible sensing layer 7, and the microstructure layer 6 will compress each other, increasing the overall structural rigidity and raising the maximum load of the entire robotic arm. Furthermore, due to the increased interlayer pressure, the flexible sensing layer 7 can also detect changes in curvature, enabling the robotic arm to interact better with the external environment.

[0055] Combination Figure 1 and Figure 7 As shown, when compressed gas is introduced into the positive pressure port of the air pipe connector 9, the soft cavity 4 bends towards the side with smaller deformation because the deformation on one side is greater than that on the other side. The multi-layer interference layer 8, the flexible sensing layer 7, and the microstructure layer 6 are located in a sealed chamber, with the flexible sensing layer 7 sandwiched between the multi-layer interference layer 8. When the vacuum pump and air pipe connector 9 are connected, under negative pressure, the multi-layer interference layer 8 in the sealed space compresses against each other, generating significant static friction. This effectively forms a relatively thick and long integral structure, increasing the rigidity of the robotic arm. At this time, the resistance of the flexible sensing layer 7 changes under pressure and bending conditions, allowing the measurement of the corresponding change in current. Finally, the curvature of the finger is obtained and transmitted to the external control board. The external control board controls the solenoid valve on the air pump to open, causing the air pump to release gas, thus mechanically deforming the soft cavity 4. When the deformation reaches a certain level, the control board controls the vacuum pump to generate a vacuum, increasing the rigidity of the variable stiffness cavity 5, thereby increasing the rigidity of the robotic arm. At this time, the flexible sensing layer 7 embedded in the variable stiffness cavity 5 deforms due to changes in external pressure. The control board then adjusts the flow rate of the air pump and vacuum pump according to the feedback voltage of the sensing circuit to adapt to objects with different surface hardness, providing safe control and stable gripping.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A soft manipulator with both flexible sensing and variable stiffness characteristics, characterized in that: The mounting base is used for connecting an external mechanical arm, and N fingers are uniformly distributed on the same side of the mounting base, where N is a positive integer greater than or equal to 1; N air pipe joints (9) are arranged on the mounting base, the air pipe joints (9) are provided with positive pressure air holes for connecting a positive pressure air source and negative pressure air holes for connecting a negative pressure air source, and the N fingers correspond to the N air pipe joints (9) in a one-to-one manner; The fingers each include a soft cavity (4) and a variable stiffness cavity (5) which are both long strips and are connected together, the soft cavity (4) is in communication with the positive pressure air holes, and the variable stiffness cavity (5) is in communication with the negative pressure air holes; One side of the soft cavity (4) connected with the variable stiffness cavity (5) is planar, and the side away from the variable stiffness cavity (5) is sawtooth-shaped or corrugated, and the sawtooth or corrugation is arranged along the length direction of the soft cavity (4); A plurality of interference layers (8) are arranged in the variable stiffness cavity (5) and are stacked on each other, a flexible sensing layer (7) is arranged between any two adjacent interference layers (8), and the flexible sensing layer (7) is electrically connected with an external control board; A microstructure layer (6) is further arranged between the flexible sensing layer (7) and one of the adjacent interference layers (8); The microstructure layer (6) is adhered to the flexible sensing layer (7), and a plurality of protrusions are arranged on the side of the microstructure layer (6) close to the flexible sensing layer (7); The plurality of interference layers (8) are divided into two groups, namely a plurality of first interference layers (81) and a plurality of second interference layers (82), one end of the first interference layer (81) is connected with one end of the variable stiffness cavity (5) close to the mounting base, one end of the second interference layer (82) is connected with one end of the variable stiffness cavity (5) away from the mounting base, and the other ends of the plurality of first interference layers (81) and the plurality of second interference layers (82) are arranged in a staggered and stacked manner in the middle part of the variable stiffness cavity (5); The planes on which the first interference layer (81) and the second interference layer (82) are arranged are parallel to the connecting plane of the soft cavity (4) and the variable stiffness cavity (5); The flexible sensing layer (7) is arranged in the middle part of the variable stiffness cavity (5) and between one of the first interference layers (81) and the adjacent second interference layer (82).

2. The soft manipulator with both flexible sensing and variable stiffness characteristics according to claim 1, wherein: The flexible sensing layer (7) is a piezoelectric polyvinylidene fluoride film.

3. The soft manipulator with both flexible sensing and variable stiffness characteristics according to claim 2, characterized in that: In the variable stiffness cavity (5), a first mounting seat (51) is arranged at one end close to the mounting base, and a second mounting seat (52) is arranged at one end away from the mounting base; A plurality of first layer blocks (511) are arranged side by side on the first mounting seat (51) in a direction away from the soft cavity (4), and one first interference layer (81) is arranged between every two adjacent first layer blocks (511); A plurality of second layer blocks (521) are arranged side by side on the second mounting seat (52) in a direction away from the soft cavity (4), and one second interference layer (82) is arranged between every two adjacent second layer blocks (521).

4. The soft manipulator with both flexible sensing and variable stiffness characteristics of claim 3, wherein: The first interference layer (81) and the second interference layer (82) are both fiber glass or paper sheets.

5. The soft manipulator with both flexible sensing and variable stiffness characteristics of claim 4, wherein: The mounting base includes a base (3) and an upper cover plate (1) which is covered on the base (3). The base (3) and the upper cover plate (1) are provided with a mounting cavity; One end of the tracheal connector (9) is respectively communicated with the soft cavity (4) and the variable stiffness cavity (5), the other end penetrates through the base (3) and extends into the mounting cavity, and is fixed through the nut (10) located in the mounting cavity; The upper cover plate (1) is provided with a flange (2) for connecting an external mechanical arm in the middle part; The flange (2) is provided with a through hole for connecting the tracheal connector (9) with the positive pressure source and the negative pressure source.

6. The soft-bodied robot of claim 5, wherein: The tracheal connector (9) is further sleeved with a limiting shaft sleeve (11); The limiting shaft sleeve (11) is located between the base (3) and the fingers.

7. The soft manipulator with both flexible sensing and variable stiffness characteristics of claim 6, wherein: The soft cavity (4) and the variable stiffness cavity (5) are made of silica gel pouring.

8. The soft-bodied robot of claim 1, wherein: N=3, the three fingers are uniformly distributed around the central axis of the mounting base; the side of the variable stiffness cavity (5) in each finger away from the soft cavity (4) is towards the extension line of the central axis of the mounting base.

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