A negative pressure variable stiffness driver and driving system

Abstract

The application discloses a negative pressure variable stiffness driver and a driving system. The negative pressure variable stiffness driver comprises a negative pressure source and a driver body. The driver body comprises a sealed soft bag, an elastic framework and a variable stiffness layer. The elastic framework is embedded in the sealed soft bag, and the variable stiffness layer is fixed on the bag wall of the sealed soft bag. The negative pressure variable stiffness driving system comprises a signal acquisition card, a pneumatic valve and the negative pressure variable stiffness driver. When the variable stiffness layer is pumped, the internal negative pressure of the variable stiffness layer is formed, the stiffness of the variable stiffness layer is increased, the stiffness of the driver body is asymmetric, and the driver body is bent towards the opposite direction; when the sealed soft bag is pumped and the internal air pressure of the variable stiffness layer is restored to the atmospheric pressure, the driver body performs a contraction movement. The driver has a high power-to-weight ratio, similar contraction characteristics and compliance to biological muscles, can realize a multi-directional bending function, and can grasp various types of objects. Meanwhile, the movement of the driver can be characterized by the change of the spring inductance to realize a self-sensing function.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of driver, in particular to a negative pressure variable stiffness driver and driving system. BACKGROUND

[0002] With the development of technology and economy, the demand for robots in the fields of medical treatment, family, education, service, rescue and wearable devices is growing, which puts forward higher requirements for the flexibility and compliance of the structure of the robot. Correspondingly, the flexible robot has the characteristics of continuous deformation, flexible movement and high compliance, which gradually attracts the attention of researchers.

[0003] As one of the key technologies of flexible robots, the driving method is self-evident in importance. Among the many driving methods (such as electricity, heat, light and magnetism), pneumatic driving is widely concerned because of its simple and safe operation characteristics, low cost and easy manufacturing. The pneumatic driver is a commonly used driver in flexible robots, which has a high power-to-weight ratio, similar contraction characteristics to biological muscles and excellent compliance, which ensures that it can realize contraction, stretching, bending or rotation and other movement modes.

[0004] In order to meet the needs of different scenes, the pneumatic driver gradually developed a negative pressure driver on the basis of the original positive pressure driver. Compared with positive pressure driving, negative pressure driving has several unique inherent advantages. First, they have no risk of explosion or burst, and the safety factor is greatly improved; for positive pressure drivers, the potential risk of injury to the user increases with the use of higher pressure. Second, the volume is relatively smaller when running, so they can be effectively used in closed spaces. Third, the contraction ratio is increased and the radial expansion is reduced. Fourth, relying on the characteristics of negative pressure driving, the driver can start quickly. One of the few main limitations is that the maximum applicable force and displacement of the negative pressure driver is limited by the maximum vacuum pressure.

[0005] The current pneumatic driver lacks the design of multi-directional bending movement. Therefore, it is necessary to design a variable stiffness multi-directional bending negative pressure driver on the basis of the negative pressure driver. SUMMARY

[0006] The purpose of the present application is to provide a negative pressure variable stiffness driver and driving system, which can realize contraction movement in the unvariable stiffness state; in the variable stiffness state, the stiffness is actively changed to realize optional multi-directional bending deformation.

[0007] The application is achieved by a negative pressure variable stiffness driver, comprising a negative pressure source and a driver body, the driver body comprising a sealed soft bag, an elastic framework and a variable stiffness layer; the negative pressure source is communicated with the sealed soft bag through a first air pipe; the elastic framework is embedded in the sealed soft bag for supporting the sealed soft bag; the variable stiffness layer is fixed on the bag wall of the sealed soft bag, and the negative pressure source is communicated with the variable stiffness layer through a second air pipe.

[0008] When the variable stiffness layer is pumped, a negative pressure is formed inside the variable stiffness layer, the stiffness of the variable stiffness layer is increased, the stiffness on the driver body is asymmetric, and the driver body is bent towards the opposite side of the variable stiffness layer; when the sealed soft bag is pumped, a negative pressure is formed inside the sealed soft bag, and at the same time, the internal air pressure of the variable stiffness layer is restored to atmospheric pressure, the driver body performs a contraction movement.

[0009] Further, the sealed soft bag comprises a film cylinder and sealing plugs, the two sealing plugs are respectively sealed and capped on the two ports of the film cylinder, and the elastic framework supports the inner wall of the film cylinder.

[0010] Further, the elastic framework is a spring, the elastic framework can be stretched and contracted along the length direction and bent outward, and the length direction of the elastic framework is parallel to the length direction of the film cylinder.

[0011] Further, the variable stiffness layer is attached to the outer periphery of the film cylinder, the driver body comprises at least one variable stiffness layer, and all the variable stiffness layers are distributed in the circumferential direction of the film cylinder.

[0012] Further, the sealing plug is prepared by using 3D printing technology, and the sealing plug is subjected to ultraviolet light curing treatment to ensure the air tightness.

[0013] Further, the variable stiffness mechanism of the variable stiffness layer is layer interference, particle interference, fiber interference or electrostatic layer interference.

[0014] Further, the variable stiffness structure of the variable stiffness layer is a layer interference structure, when the variable stiffness layer is not pumped, the layer interference structure inside the variable stiffness layer can relatively freely slide, and the variable stiffness layer has a lower stiffness; when the variable stiffness layer is pumped to form a negative pressure inside, the adjacent layer interference structures inside the variable stiffness layer are coupled with each other, and the stiffness of the variable stiffness layer is increased.

[0015] Further, the variable stiffness structure of the variable stiffness layer is an electrostatic adsorption structure, which is realized by oppositely arranging a positive electrode sheet and a negative electrode sheet and connecting a high-voltage source; when the high-voltage source is not connected, there is no interaction force between the positive electrode sheet and the negative electrode sheet, and the two can slide freely relative to each other, and the variable stiffness layer has a lower stiffness; when the high-voltage source is connected, an adsorption force is generated between the positive electrode sheet and the negative electrode sheet, and the two cannot slide relative to each other, and the stiffness of the variable stiffness layer is increased.

[0016] To achieve the above-mentioned purposes of the application, the application further provides a negative pressure variable stiffness driving system, comprising a signal acquisition card, a pneumatic valve, an inductance measurement module, a control workstation and the above-mentioned negative pressure variable stiffness driver, the first air pipe and the second air pipe are connected with the pneumatic valve; the signal acquisition card outputs an analog signal to control the pneumatic valve to adjust the size and direction of air pressure, so as to control the air pressure in the sealed soft bag and the variable stiffness layer respectively, thereby realizing different functions.

[0017] The control workstation is electrically connected with the signal acquisition card, the pneumatic valve and the inductance measurement module; the inductance change of the spiral spring coil is measured by the inductance measurement module to reflect the deformation condition, the measured data is input back to the signal acquisition card through an analog signal, and is integrated and analyzed in the control workstation.

[0018] Compared with the prior art, the application has the following beneficial effects:

[0019] The negative pressure variable stiffness driver provided by the application can realize contraction movement in the unvariable stiffness state, and can realize optional bending deformation by increasing the stiffness of the variable stiffness layer in the variable stiffness state, so that the adaptability is greatly improved compared with traditional rigid drivers, and the power-to-weight ratio is high, the contraction characteristics are similar to biological muscles, and the compliance is excellent, and the negative pressure variable stiffness driver is especially suitable for application in a flexible robot to realize grasping of various types of objects. Meanwhile, the negative pressure variable stiffness driver adopts a spring as an internal skeleton, and the movement of the driver body can be characterized by the change of inductance to realize a self-sensing function. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a longitudinal sectional view of a negative pressure variable stiffness driver provided by an embodiment of the application;

[0021] Figure 2 is Figure 1 is a transverse sectional view of the negative pressure variable stiffness driver shown in the figure;

[0022] Figures 3a to 3d is a schematic view of arranging different numbers of variable stiffness layers on the outer periphery of the sealed soft bag;

[0023] Figures 4a to 4c is a schematic view of the driver of the embodiment realizing various types of grasping according to different shapes of objects;

[0024] Figure 5a is a schematic diagram of a variable stiffness layer of a layer interference structure provided by the embodiment;

[0025] Figure 5b is a schematic diagram of a variable stiffness layer of an electrostatic adsorption structure provided by the embodiment;

[0026] Figure 6 is a structural block diagram of a negative pressure variable stiffness driving system provided by the embodiment of the application;

[0027] Figure 7 is a comparison diagram of experimental data and theoretical data of a self-sensing function of a negative pressure variable stiffness driver provided by the embodiment of the application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application.

[0029] In the description of the application, it should be noted that the terms "center", "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application; the terms "first", "second", "third" are only used for description purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise explicitly specified and limited, the terms "mounting", "connection" and "connection" should be understood broadly, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium, or the communication between two components. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0030] The embodiment provides a negative pressure variable stiffness driver, which comprises a negative pressure source and a driver main body, with reference to Figure 1 and Figure 2The driver body comprises a sealed soft bag 1, an elastic framework 2 and a variable stiffness layer 3; a negative pressure source is communicated with the sealed soft bag 1 through a first air pipe 4; the elastic framework 2 is embedded in the sealed soft bag 1 and used for supporting the sealed soft bag 1; the variable stiffness layer 3 is fixed on the bag wall of the sealed soft bag 1, and the negative pressure source is communicated with the variable stiffness layer 3 through a second air pipe 5. When the variable stiffness layer 3 is pumped and a negative pressure is formed in the variable stiffness layer 3, the stiffness of the variable stiffness layer 3 becomes larger, the stiffness of the driver body is asymmetric, and the driver body bends towards the opposite side of the variable stiffness layer 3. When the sealed soft bag 1 is pumped and a negative pressure is formed in the sealed soft bag 1, and the internal air pressure of the variable stiffness layer 3 is restored to the atmospheric pressure at the same time, the driver body performs a contraction movement.

[0031] Specifically, the negative pressure source is a vacuum pump, the first air pipe 4 and the second air pipe 5 are PU air pipes, the inner diameter is 2.5 mm, and the outer diameter is 4 mm.

[0032] The sealed soft bag 1 comprises a PE film cylinder 11 and sealed plugs 12, and the two sealed plugs 12 are respectively sealed and capped on the two ports of the PE film cylinder 11. In the embodiment, the sealed plugs 12 are prepared by using a 3D printing technology, the selected 3D printing material is PLA, and the sealed plugs 12 are treated by ultraviolet light curing to ensure the air tightness.

[0033] The elastic framework 2 is used for supporting the inner wall of the PE film cylinder 11, and in the embodiment, the elastic framework 2 is a steel spiral spring with a wire diameter of 0.9 mm, an outer diameter of 20 mm and a length of 100 mm. The form and size of the elastic framework 2 can be changed according to different scene requirements. The elastic framework 2 can stretch along the length direction and bend outward, and the length direction of the elastic framework 2 is parallel to the length direction of the PE film cylinder 11.

[0034] The variable stiffness layer 3 is attached to the outer periphery of the PE film cylinder 11, and the driver body comprises at least one variable stiffness layer 3, and all the variable stiffness layers 3 are distributed in the circumferential direction of the PE film cylinder 11. In actual application, the number and position distribution of the variable stiffness layers 3 are not limited. Referring to Figures 3a to 3d , the application modes of arranging 1-4 variable stiffness layers 3 on the outer periphery of the sealed soft bag 1 are respectively shown. It is easy to understand that the multiple variable stiffness layers 3 can selectively pump one or more of them to form a negative pressure, so that the driver body can realize the bending in the optional direction, for example, pumping only one variable stiffness layer 3 to realize the bending in one direction (since the stiffness of the opposite side of the variable stiffness layer 3 is small, the bending direction is the side opposite to the variable stiffness layer 3), and pumping the left and right variable stiffness layers 3 to realize the left and right swing of the driver body. The more the number of the variable stiffness layers 3 is, the more the directions of the bending deformation of the driver body can be selected.

[0035] The negative pressure variable stiffness driver based on the embodiment has the characteristic of optional bending, so the driver of the embodiment can realize various types of grabbing according to different shapes of objects. Referring to Figure 4a , the two drivers bend inward to realize grabbing of general objects; referring to Figure 4b , the two drivers bend outward to press against the cavity inside the object to realize grabbing; referring to Figure 4c , the single driver bends to realize hooking of the object.

[0036] The variable stiffness mechanism of the variable stiffness layer includes but is not limited to the following four types: (1) layer interference; (2) particle interference; (3) fiber interference; and (4) electrostatic layer interference.

[0037] Specifically, the principle of layer interference is as follows: referring to Figure 5a , the layer interference structure is composed of flexible material sheets placed in a gas-tight enclosure. When no negative pressure is applied, the layers in the layer interference structure can slide freely relative to one another, and the overall stiffness is low. When the negative pressure source is controlled to draw air, the increased friction causes each layer of material to couple with its adjacent layer. The entire structure behaves like a cohesive "beam" rather than a collection of independent discrete layers. The stiffness of the interference structure is high until the shear stress induced in the "beam" can overcome the frictional stress caused by the applied negative pressure.

[0038] Specifically, the principle of particle interference is as follows: particle interference is usually composed of granular elements in a gas-tight enclosure, which are free to move relative to each other when no negative pressure is applied, behaving like a liquid. When pressure is applied, the grains are constrained, and the structure changes to a solid state.

[0039] Specifically, the principle of fiber interference is as follows: fiber interference is composed of longitudinal fibers in a gas-tight enclosure. Along one plane, the fibers can rearrange like grains, while in the other two orthogonal planes, they can slide relative to each other like layers.

[0040] Specifically, the principle of electrostatic layer interference is as follows: referring to Figure 5b , fiber interference is composed of longitudinal fibers in a gas-tight enclosure. Along one plane, the fibers can rearrange like grains, while in the other two orthogonal planes, they can slide relative to each other like layers.

[0041] Referring to Figure 6 , the embodiment also provides a negative pressure variable stiffness driving system, which includes a power supply, a signal acquisition card, a pneumatic valve, a negative pressure variable stiffness driver, an inductance measurement module, and a control workstation. The control workstation is electrically connected to the signal acquisition card, the pneumatic valve, and the inductance measurement module.

[0042] The first air pipe 4 and the second air pipe 5 are connected with a pneumatic valve, which can be an electromagnetic valve or a proportional valve. An analog signal is output by a signal acquisition card in the computer, which controls the pneumatic valve to adjust the size and direction of air pressure, thereby controlling the air pressure inside the sealed soft bag 1 and the variable stiffness layer 3, respectively, to achieve different functions.

[0043] With reference to Figure 7 The inductance change of the coil of the helical spring can be measured by the inductance measurement module to reflect the deformation, and the measured data is input back to the signal acquisition card through an analog signal and is integrated and analyzed in the control workstation.

[0044] The working process of the negative pressure variable stiffness driving system of the embodiment includes the following steps:

[0045] The variable stiffness layer 3 is pumped (the layer interference structure is selected here), and the stiffness of the variable stiffness layer 3 increases;

[0046] After the stiffness change of the variable stiffness layer 3 is completed, the internal driving layer is pumped, and the driver body is bent and deformed;

[0047] The negative pressure source is turned off, and the driver body returns to the original state.

[0048] In summary, the negative pressure variable stiffness driver provided by the embodiment can realize contraction movement in the unvariable stiffness state, and can realize optional bending deformation (i.e., multi-directional bending deformation) by increasing the stiffness of the variable stiffness layer 3 in the variable stiffness state, which greatly improves the adaptability compared with traditional rigid drivers, has a high power-to-weight ratio, similar contraction characteristics to biological muscles, and excellent compliance, and is particularly suitable for application in flexible robots to realize grasping of various types of objects. At the same time, the negative pressure variable stiffness driver uses a helical spring as an internal skeleton, and the movement of the driver body can be characterized by the change of inductance to realize self-sensing function.

[0049] The above only describes the preferred embodiments of the present application and should not be used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A negative stiffness driver, characterized by, The driver body includes a sealed soft bag, an elastic framework and a variable stiffness layer; the negative pressure source is communicated with the sealed soft bag through a first air pipe; the elastic framework is embedded in the sealed soft bag for supporting the sealed soft bag; the variable stiffness layer is fixed on the bag wall of the sealed soft bag, and the negative pressure source is communicated with the variable stiffness layer through a second air pipe; When the variable stiffness layer is pumped, the stiffness of the variable stiffness layer is increased, the stiffness of the driver body is asymmetric, and the driver body is bent towards the opposite side of the variable stiffness layer; when the sealed soft bag is pumped, the internal pressure of the sealed soft bag is formed, and the internal pressure of the variable stiffness layer is restored to atmospheric pressure, the driver body is contracted; the elastic framework is a spiral spring coil, the spiral spring coil can be stretched along the length direction and bent outward, the sealed soft bag includes a film cylinder, the spiral spring coil supports the inner wall of the film cylinder, and the length direction of the spiral spring coil is parallel to the length direction of the film cylinder; the deformation condition is reflected by measuring the inductance change of the spiral spring coil.

2. The negative pressure variable stiffness actuator of claim 1, wherein, The sealed soft bag includes sealing plugs, and the two sealing plugs are respectively sealed and capped on the two ports of the film cylinder.

3. The negative pressure variable stiffness actuator of claim 2, wherein, The variable stiffness layer is attached to the outer periphery of the film cylinder, the driver body includes at least one variable stiffness layer, and all the variable stiffness layers are distributed along the circumferential direction of the film cylinder.

4. The negative pressure variable stiffness actuator of claim 2, wherein, The sealing plug is prepared by 3D printing technology, and the sealing plug is treated by ultraviolet light curing to ensure the air tightness.

5. The negative pressure variable stiffness actuator of claim 1, wherein, The variable stiffness mechanism of the variable stiffness layer is layer interference, particle interference, fiber interference or electrostatic layer interference.

6. The negative pressure variable stiffness actuator of claim 1, wherein, The variable stiffness structure of the variable stiffness layer is a layer interference structure, the layer interference structure in the variable stiffness layer can slide relatively freely when the variable stiffness layer is not pumped, and the variable stiffness layer has a lower stiffness; when the variable stiffness layer is pumped to form a negative pressure inside, the adjacent layer interference structures in the variable stiffness layer are coupled with each other, and the stiffness of the variable stiffness layer is increased.

7. The negative pressure variable stiffness actuator of claim 1, wherein, The variable stiffness structure of the variable stiffness layer is an electrostatic adsorption structure, which is realized by relatively placing the positive electrode sheet and the negative electrode sheet and connecting a high voltage source; when the high voltage source is not connected, there is no interaction force between the positive electrode sheet and the negative electrode sheet, and the two can slide relatively freely, and the variable stiffness layer has a lower stiffness; when the high voltage source is connected, the adsorption force is generated between the positive electrode sheet and the negative electrode sheet, and the two cannot slide relatively, and the stiffness of the variable stiffness layer is increased.

8. A negative pressure variable stiffness drive system, characterized by, The negative pressure variable stiffness driver comprises a signal acquisition card, a pneumatic valve, an inductance measurement module, a control workstation and the negative pressure variable stiffness driver of claim 1, the first air pipe and the second air pipe are connected with the pneumatic valve; the signal acquisition card outputs an analog signal, controls the pneumatic valve to adjust the size and direction of air pressure, thereby respectively controls the air pressure inside the sealed soft bag and the variable stiffness layer, so as to realize different functions; the control workstation is electrically connected with the signal acquisition card, the pneumatic valve and the inductance measurement module; the inductance change of the spiral spring coil is measured by the inductance measurement module to reflect the deformation condition, the measured data is input back to the signal acquisition card through an analog signal, and is integrated and analyzed in the control workstation.

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