Soft variable-stiffness gripper based on electrostatic hydraulic drive

Abstract

The invention discloses a soft variable stiffness gripper based on electrostatic hydraulic driving, which comprises a fixing frame, a fixing nut, an electrostatic hydraulic driver, a skeleton driving plate, an electrostatic adsorption layer interference assembly and a fixing bolt, realizes driving through an electrostatic hydraulic driving principle, and has the characteristics of simple structure, low energy consumption, quick response and high flexibility. Flexible grabbing and efficient grabbing of the gripper are facilitated, variable rigidity is achieved through the electrostatic adsorption layer interference principle, the gripper has the advantages of being low in energy consumption, rapid in response and large in rigidity, and the stable grabbing and carrying capacity of the gripper is easy to achieve; the driving mode and the variable rigidity mode have high consistency, an integrated control circuit can be easily achieved, meanwhile, dependence of external assemblies is greatly reduced through passive driving, the structure is simplified, the flexible grabbing capacity and the variable rigidity capacity achieve optimal design of the soft grabbing hand in the aspects of structure simplification, flexible rigidity adjustment, efficient grabbing and the like, and the soft grabbing hand is high in practicability. And the grabbing work of complex environments and tasks can be realized.

Description

Technical Field

[0001] The invention relates to the field of soft machine grippers, and in particular to a soft variable-rigidity gripper based on electrostatic hydraulic drive. Background Art

[0002] With the continuous development of robotics and automatic control theory, robotics technology has been widely used in industrial production, medical services, military reconnaissance and other fields. At the same time, mechanical grippers are the most widely used end effectors in robotics technology. However, due to their inherent rigid components, traditional rigid grippers usually have problems such as complex structure, large size, heavy weight, and high cost. They are difficult to adapt to unstructured environments and have low safety in human-computer interaction scenarios. In contrast, soft grippers are made of flexible materials and can adjust their own shape according to actual needs. They have better environmental adaptability and higher safety.

[0003] The driving modes of existing soft grippers mainly include air pressure drive, electroactive polymer drive, shape memory material drive, etc. The above-mentioned driving modes have problems such as the need for an external air source, slow response speed and high energy consumption, which have become the core factors hindering the development of soft grippers in end effectors. At the same time, as soft grippers are gradually expanded in complex application tasks, higher requirements are also placed on the adaptability of the gripper itself, that is, when grasping soft and fragile objects, flexibility can be achieved with low stiffness, and when grasping heavier objects, high stiffness stability can be achieved. In the prior art, driving technology and variable stiffness technology are often difficult to integrate, and more driving and variable stiffness mechanisms are required at the same time. For example, patent number CN202010629738.X is a variable stiffness picking manipulator based on rigid-flexible combination. Its rigid-flexible coupling verifies that the variable stiffness soft gripper has great application value, but its external air pump driving source and more driving mechanisms make the structure more complicated. At the same time, the high energy consumption also limits its wide adaptability, greatly affecting the flexibility of the gripper. Summary of the invention

[0004] In view of this, the present invention aims to provide a soft variable stiffness soft gripper based on electrostatic hydraulic drive. It combines the advantages of electrostatic hydraulic drive such as large output force, fast response, and low energy consumption with the stiffness adjustment and high efficiency of the electrostatic adsorption layer interference to achieve the optimized design of the soft gripper in terms of structural simplification, flexible stiffness adjustment, and efficient grasping. Relatively similar driving conditions simplify its structure, which helps to improve the integrity of the gripper and reduce production costs; flexible stiffness adjustment can enhance the gripper's adaptability to objects of different shapes and textures, while the efficient grasping performance provides a new breakthrough in the application scope and technical level of existing soft grippers.

[0005] In order to achieve the above technical objectives and the above effects, the present invention is implemented through the following technical solutions:

[0006] A soft variable stiffness gripper based on electrostatic hydraulic drive, comprising:

[0007] The fixing frame has a hexagonal side wall and is provided with mounting holes and circuit wiring holes. The mounting holes and the through holes on the skeleton drive board are detachably connected by fixing bolts and fixing nuts. In particular, since the side wall is hexagonal, a single-finger variable stiffness joint can be combined to form a two-finger gripper and a three-finger gripper, etc.; a circuit harness hole is provided on it to better connect and control with an external robotic arm;

[0008] An electrostatic hydraulic actuator, comprising an upper flexible electrode, an upper dielectric film, a dielectric oil, a lower dielectric film, and a lower flexible electrode, wherein the upper dielectric film and the lower dielectric film are sealed at the outer edges to form a flexible closed cavity, the dielectric oil is located in the closed space formed by the dielectric film, and the upper and lower flexible electrodes are respectively located on the outer sides of the upper and lower dielectric films;

[0009] The driving plate frame includes an upper driving plate, a spindle, a lower driving plate, and an anti-slip silicone sheet. The upper driving plate and the lower driving plate are made of PLA material with a certain rigidity, and are cross-embedded with each other through a hinge-like structure, and then the spindle made of fine steel wire is inserted into the middle through-mounting hole to form a hinge, and the anti-slip silicone sheet is bonded to the trapezoidal plane of the lower driving plate through double-sided adhesive.

[0010] The electrostatic adsorption layer interference component includes an adsorption plate outer layer, a double-sided adhesive layer, a flexible electrode layer, an insulating layer, and an adsorption plate inner layer. The flexible electrode layer is printed on one side of the insulating layer, and the other side of the electrode is connected to the adsorption plate inner layer and the adsorption plate outer layer through the double-sided adhesive layer to form an inner and outer layer adsorption unit.

[0011] Furthermore, the upper and lower dielectric films are TPU (thermoplastic polyurethane elastomer) films, the hot melt adhesive layers of the two TPU films face inwards and are sealed and connected by heat sealing.

[0012] Furthermore, the upper flexible electrode is graphene conductive ink attached to the upper dielectric film by printing, the lower flexible electrode is conductive tape adhered to the lower dielectric film, and the dielectric oil is silicone oil.

[0013] Furthermore, one end of the electrostatic hydraulic driver is connected to the upper driving plate via double-sided tape, and the other end of the driver is connected to the lower driving plate via double-sided tape. After being stimulated, the electrostatic hydraulic driver produces longitudinal linear contraction and axial expansion, thereby driving the lower driving plate to rotate around the central axis. In particular, the portion where the electrostatic hydraulic driver is connected to the lower driving plate should be as close as possible to the hinge-shaped protrusion to maximize the liquid pressure driving effect.

[0014] Furthermore, the upper driving plate has four pairs of mounting grooves for installing outer adsorption units, and the outer adsorption units are fixedly connected to the mounting grooves on the upper driving plate by UV light-curing glue. In particular, the outer adsorption units are installed on opposite sides so that the adsorption areas are all facing the inner layer, and the lower driving plate has four mounting grooves for installing inner adsorption units, and the inner adsorption units are fixedly connected to the mounting grooves on the upper driving plate by UV light-curing glue.

[0015] Furthermore, the inner and outer layers of the adsorption board are PVC boards formed by laser cutting, the flexible electrode layer is conductive ink, and the insulating layer is a PVDF composite film. The special conductive ink is printed on the insulating layer by screen printing. After the conductive ink is completely air-dried and solidified, double-sided tape is used to adhere the surface of the conductive ink and the PVC board to form an adsorption unit. In particular, the inner adsorption unit has adsorption areas on both sides, while the outer adsorption unit is a mirror-image unit with an adsorption area only on the side facing the inner adsorption unit.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention is a soft variable stiffness gripper based on electrostatic hydraulic drive. Its driving mode is passive driving, which greatly reduces the dependence on external components and simplifies the structure. At the same time, the gripper constructed by this driving mode exhibits flexible grasping in the grasping stage, and the variable stiffness function realized by the interference of the electrostatic adsorption layer improves the adaptive grasping ability of the gripper. At the same time, the consistent driving and variable stiffness excitation conditions simplify its structure, improve the integrity of the gripper and reduce power consumption, and realize the optimization design of the soft gripper in terms of structural simplification, flexible stiffness adjustment, and efficient grasping. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a structural explosion diagram of a soft variable-rigidity gripper based on electrostatic hydraulic drive according to the present invention;

[0019] Figure 2 It is a structural exploded diagram of the electrostatic hydraulic actuator in the present invention;

[0020] Figure 3 Schematic diagram of the structure of the electrostatic hydraulic actuator in the present invention (undriven state);

[0021] Figure 4 It is a structural schematic diagram of the skeleton driving plate in the present invention;

[0022] Figure 5 It is a partial structural exploded diagram of the electrostatic adsorption layer interference component in the present invention;

[0023] Figure 6 Schematic diagram of the structure of a single-finger variable stiffness joint in the present invention (undriven state);

[0024] Figure 7 for Figure 6 Schematic diagram of the structure of a single-finger variable stiffness joint (driven bending state);

[0025] Figure 8 Schematic diagram of the overall structure of the three-finger variable stiffness gripper of the present invention (undriven state);

[0026] Fig. 9 for Figure 8 Schematic diagram of the overall structure of the three-finger variable stiffness gripper (driven bending state);

[0027] Fig.10 It is a schematic diagram of the overall structure of the two-finger variable stiffness gripper of the present invention (driven bending state);

[0028] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0029] 1-fixed frame; 2-fixed nut; 3-electrostatic hydraulic driver; 4-skeleton drive board; 5-electrostatic adsorption layer interference component; 6-fixed bolt; 301-upper flexible electrode; 302-upper dielectric film; 303-dielectric oil; 304-lower dielectric film; 305-lower flexible electrode; 401-upper drive board; 402-spindle; 403-lower drive board; 404-anti-slip silicone sheet; 501-outer layer of adsorption board; 502-double-sided adhesive layer; 503-flexible electrode layer; 504-insulating layer; 505-inner layer of adsorption board. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] like Figures 1 to 10As shown, the present invention is a soft variable stiffness gripper based on electrostatic hydraulic drive, which includes: a fixing frame 1, a fixing nut 2, an electrostatic hydraulic driver 3, a skeleton driving plate 4, an electrostatic adsorption layer interference component 5, and a fixing bolt 6; the skeleton driving plate 4 can be fixed by bolts through a through hole set on the fixing frame 1 in the single-finger variable stiffness joint to form a detachable connection, the single-finger variable stiffness joint includes an electrostatic hydraulic driver 3, a skeleton driving plate 4 and an electrostatic adsorption layer interference component 5, the electrostatic hydraulic driver 3 is connected to the skeleton driving 4 through double-sided adhesives set at the head and tail positions, and the electrostatic hydraulic Under the stimulation of the high-voltage electric field, the driver 3 will produce longitudinal contraction and axial expansion, which will then act on the skeleton drive plate 4, causing the lower drive plate 403 to rotate around the central axis 402 to form a flexible grip. The electrostatic adsorption layer interference component 5 is provided with two rectangular mounting features at each end to cooperate with the two slots provided on the skeleton drive plate 4, and is fixedly connected with UV light-curing glue after installation. When the gripper completes the gripping and wrapping action, the electrostatic adsorption layer interference component 5 instantly increases the stiffness of the gripper joint under the stimulation of the high-voltage electric field, and then completes the lifting and transfer of the grip.

[0032] In this embodiment, the fixed frame 1 and at least two single-finger variable stiffness joints constitute the variable stiffness gripper body. The holes arranged on the wall of the fixed frame 1 are used to arrange the electrode connection lines of the electrostatic hydraulic driver 3 and the electrostatic adsorption layer interference variable stiffness component 5. A wire harness hole is arranged above it to collect the control circuits of the gripper for docking with an external robotic arm.

[0033] In this embodiment, the single-finger variable stiffness joint includes an electrostatic hydraulic driver 3, a skeleton driving plate 4 and an electrostatic adsorption layer interference component 5. The electrostatic hydraulic driver 3 is bonded to the middle position of the upper driving plate 401 with double-sided tape at one end close to the contact position of the flexible electrode pair, and the other end of the driver is bonded to the lower driving plate 403 near the hinge protrusion with double-sided tape. A pair of outer adsorption units of the electrostatic adsorption layer interference component 5 are installed in opposite directions at the mounting groove positions on the upper driving plate 401 and are fixedly connected with UV light-curing glue, and the inner adsorption unit of the electrostatic adsorption layer interference component 5 is installed in the mounting groove position on the lower driving plate 403 and is fixedly connected with UV light-curing glue.

[0034] In this embodiment, the electrostatic hydraulic actuator 3 includes an upper flexible electrode 301, an upper dielectric film 302, a dielectric oil 303, a lower dielectric film 304, and a lower flexible electrode 305. The upper dielectric film 302 and the lower dielectric film 303 are sealed at the outer edges to form a flexible closed cavity. The dielectric oil is located in the closed space formed by the dielectric film. The upper and lower flexible electrodes are respectively located on the outer sides of the upper and lower dielectric films.

[0035] In this embodiment, the driving plate skeleton 4 includes an upper driving plate 401, a core shaft 402, a lower driving plate 403, and an anti-slip silicone sheet 404. The upper driving plate 401 and the lower driving plate 403 are cross-embedded with each other through a hinge-like structure, and then the core shaft 403 made of fine steel wire is inserted into the middle through-mounting hole to form a hinge. The anti-slip silicone sheet 404 is bonded to the trapezoidal plane of the lower driving plate 403 through double-sided tape.

[0036] In this embodiment, the electrostatic adsorption layer interference component 5 includes an adsorption plate outer layer 501, a double-sided adhesive layer 502, a flexible electrode layer 503, an insulating layer 504, and an adsorption plate inner layer 505. The flexible electrode layer 503 is printed on one side of the insulating layer 504, and the other side of the electrode is respectively connected to the adsorption plate inner layer 505 and the adsorption plate outer layer 501 through the double-sided adhesive layer 502 to form an inner and outer layer adsorption unit.

[0037] In this embodiment, the flexible electrode pair composed of the upper flexible electrode 301 and the lower flexible electrode 305 forms a gripper driving source under the excitation of the positive and negative high-voltage electric fields. The excited electrode pair causes the dielectric film cavity to produce longitudinal contraction and axial expansion to form a drive. The two mirror-symmetrical outer adsorption units and the inner adsorption layer sandwiched in the middle together constitute a layer interference adsorption unit, in which the flexible electrode layer 503 is also attracted to each other under the action of the electric field, so the tangential friction force provided provides a greater stiffness for the gripper joint.

[0038] In this embodiment, the invention mainly has two systematic working stages: a flexible grasping stage and a variable stiffness enhancement stage.

[0039] During the flexible grasping stage, the upper flexible electrode 301 and the lower flexible electrode 305 form a flexible electrode pair with opposite voltage polarities. When the upper and lower electrodes of the driver are activated, due to the Maxwell attraction generated between the electrodes, the upper and lower electrodes drive the upper and lower films to attract each other, and squeeze the dielectric oil in the liquid cavity toward the electrode-free area, causing the liquid bag to bulge near the lower driving plate 403 and produce contraction and squeezing, driving the lower driving plate 403 to rotate around the core shaft 402, realizing the bending and grasping action of the joint. Since the joint is controlled by the flexible driver at this time, it is a flexible grasping stage.

[0040] During the variable stiffness enhancement stage, the flexible electrode layer 503 of the inner and outer adsorption units forms a parallel plate electrode pair, and its driving principle is consistent with the above-mentioned electrostatic hydraulic driver. After activation and excitation, the inner and outer adsorption units are tightly adsorbed together due to the electric field force. At this time, the large tangential force generated on the surface of the insulating layer 504 in the adsorption area makes the joint stiffness increase instantly. At this time, the joint forms a self-locking state and can maintain the joint bending state even when the excitation of the electrostatic hydraulic driver is removed. At the same time, the larger stiffness and holding force are used to carry the grasped objects.

[0041] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A soft variable stiffness gripper based on electrostatic hydraulic drive, characterized in that: The invention comprises a fixing frame (1), a fixing nut (2), an electrostatic hydraulic driver (3), a skeleton driving plate (4), an electrostatic adsorption layer interference component (5) and a fixing bolt (6); the skeleton driving plate (4) and the fixing frame (1) are detachably connected by bolts; the fixing frame (1) and at least two single-finger variable stiffness joints constitute a variable stiffness gripper body; the single-finger variable stiffness joints comprise an electrostatic hydraulic driver (3), a skeleton driving plate (4) and an electrostatic adsorption layer interference component (5); the electrostatic hydraulic driver (3) and the driving plate (4) are connected on the inside; and the electrostatic adsorption layer interference component (5) and the skeleton driving plate (4) are connected on the outside.

2. According to claim 1, a soft variable stiffness gripper based on electrostatic hydraulic drive is characterized in that: The electrostatic hydraulic actuator (3) comprises an upper flexible electrode (301), an upper dielectric film (302), a dielectric oil (303), a lower dielectric film (304), and a lower flexible electrode (305); the upper dielectric film and the lower dielectric film are sealed at the outer edges to form a flexible closed cavity; the dielectric oil is located in the closed space formed by the dielectric films; and the upper and lower flexible electrodes are respectively located on the outer sides of the upper and lower dielectric films; The skeleton driving plate (4) comprises an upper driving plate (401), a spindle (402), a lower driving plate (403), and an anti-slip silicone sheet (404); the upper driving plate (401) and the lower driving plate (403) are hinged via the spindle (402); and the anti-slip silicone sheet (404) and the lower driving plate (403) are bonded; The electrostatic adsorption layer interference component (5) comprises an adsorption plate outer layer (501), a double-sided adhesive layer (502), a flexible electrode layer (503), an insulating layer (504), and an adsorption plate inner layer (505); the flexible electrode layer (503) is printed on one side of the insulating layer, and the other side of the electrode is connected to the adsorption plate inner layer (505) and the adsorption plate outer layer (501) through the double-sided adhesive layer (502) to form inner and outer layer adsorption units, respectively; the outer layer adsorption units with adsorption areas arranged on two opposite sides place the inner layer adsorption unit in the middle by sandwiching to form the electrostatic adsorption layer interference component (5).

3. The variable stiffness soft gripper based on electrostatic hydraulic drive according to claim 1, characterized in that: The electrostatic hydraulic driver (3) has a squeezing effect on the protrusion at the hinge, and at the same time has a pulling effect on the drive plate to form the joint bending; its variable stiffness method is that the electrostatic adsorption layer interference component (5) on the outside of the drive plate has no effect on the inner drive, and at the same time when the component is in a driving effect, its stiffness is greatly improved, thereby making the joint have a high stiffness characteristic; the electrostatic hydraulic driver (3) and the electrostatic adsorption layer interference component (5) are both high-voltage drives, and their drive and control use the same set of drive control circuits to greatly improve the integrity of the gripper.

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