Negative pressure variable stiffness driver and driving system

Abstract

The invention 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 main body, and the driver main body comprises a sealing soft bag, an elastic skeleton 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 a negative pressure variable stiffness driver. When air is exhausted to the variable-rigidity layer and negative pressure is formed in the variable-rigidity layer, the rigidity of the variable-rigidity layer is increased, the rigidity of the driver main body is asymmetric, and the driver main body is bent towards the opposite side direction; and when air is exhausted from the sealed soft bag and the internal air pressure of the variable stiffness layer is recovered to atmospheric pressure, the driver main body does contraction motion. The driver has the high power-to-weight ratio and the contraction characteristic and compliance similar to those of biological muscles, the multi-direction bending function can be achieved, and various types of objects can be grabbed. Meanwhile, the movement of the driver can be represented through the change of the inductance of the spring so as to realize a self-sensing function.

Description

Technical Field

[0001] The invention belongs to the field of drivers, and in particular relates to a negative pressure variable stiffness driver and a driving system. Background Art

[0002] With the development of technology and economy, the demand for robots in the fields of medical, family, education, service, rescue and wearable devices is growing, which puts higher requirements on the flexibility and compliance of robot structures. Accordingly, the characteristics of flexible robots compared with traditional robots, such as continuous deformation, flexible movement and high compliance, have gradually attracted the attention of researchers.

[0003] As one of the key technologies of flexible robots, the driving method is of great importance. Among the many driving methods (such as electricity, heat, light and magnetism), pneumatic drive has attracted widespread attention due to its simple and safe operation, low cost and easy manufacturing. Pneumatic actuators are a commonly used actuator in flexible robots. They have a high power-to-weight ratio, contraction characteristics similar to biological muscles and excellent compliance. These characteristics ensure that they can achieve a variety of motion modes such as contraction, stretching, bending or rotation.

[0004] In order to cater to the needs of different scenarios, pneumatic actuators have gradually developed negative pressure actuators based on the original positive pressure actuators. Compared with positive pressure actuators, negative pressure actuators have several unique inherent advantages. First, they are not at risk of explosion or bursting, and the safety factor is greatly improved; for positive pressure actuators, the potential risk of user injury increases with the use of higher pressures. Second, the volume is relatively smaller during operation, allowing them to be effectively used in confined spaces. Third, the contraction ratio is increased and the radial expansion is reduced. Fourth, relying on the characteristics of negative pressure drive, the drive can start quickly. One of the few major limitations is that the maximum applicable force and displacement of the negative pressure actuator are limited by the maximum vacuum pressure.

[0005] The current pneumatic actuator lacks a design that can realize multi-directional bending motion. Therefore, it is necessary to design a multi-directional bending negative pressure actuator with variable stiffness based on the negative pressure actuator. Summary of the invention

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

[0007] The present invention is implemented as follows: a negative pressure variable stiffness driver comprises a negative pressure source and a driver body, wherein the driver body comprises a sealing soft bag, an elastic skeleton and a variable stiffness layer; the negative pressure source is connected to the sealing soft bag through a first air tube; the elastic skeleton is embedded in the sealing soft bag to support the sealing soft bag; the variable stiffness layer is fixed on the bag wall of the sealing soft bag, and the negative pressure source is connected to the variable stiffness layer through a second air tube;

[0008] When air is pumped into the variable stiffness layer and negative pressure is formed inside the variable stiffness layer, the stiffness of the variable stiffness layer increases, the stiffness on the driver body becomes asymmetric, and bends toward the opposite side where the variable stiffness layer is installed; when air is pumped into the sealed soft bag and 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 contracts.

[0009] Furthermore, the sealing soft bag includes a film tube and a sealing plug, the two sealing plugs are respectively sealed and covered on two ends of the film tube, and the elastic skeleton supports the inner wall of the film tube.

[0010] Furthermore, the elastic skeleton is a spring, and the elastic skeleton can be stretched and retracted along its own length direction and bent toward the outside, and the length direction of the elastic skeleton is parallel to the length direction of the film tube.

[0011] Furthermore, 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 variable stiffness layers are distributed at intervals along the circumferential direction of the film cylinder.

[0012] Furthermore, the sealing plug is prepared by 3D printing technology, and the sealing plug is treated by ultraviolet light curing to ensure an airtight effect.

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

[0014] Furthermore, the variable stiffness structure of the variable stiffness layer is a layer interference structure. When air is not pumped into the variable stiffness layer, the layer interference structure inside the variable stiffness layer can slide relatively freely, and the variable stiffness layer has a lower stiffness. When air is pumped into the variable stiffness layer to form a negative pressure inside the variable stiffness layer, adjacent layer interference structures inside the variable stiffness layer are coupled with each other, and the stiffness of the variable stiffness layer becomes greater.

[0015] Furthermore, the variable stiffness structure of the variable stiffness layer is an electrostatic adsorption structure, which is achieved by placing the positive electrode sheet and the negative electrode sheet relative to each other and connecting them to 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, 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, the two cannot slide relative to each other, and the stiffness of the variable stiffness layer becomes greater.

[0016] In order to achieve the above-mentioned purpose of the invention, the present invention also provides a negative pressure variable stiffness drive system, including 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 both connected to the pneumatic valve; the signal acquisition card outputs an analog signal to control the pneumatic valve to adjust the size and direction of the air pressure, thereby respectively controlling the air pressure inside the sealing soft bag and the variable stiffness layer, so as to achieve different functions.

[0017] The control workstation is electrically connected to 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, and the measured data is input back to the signal acquisition card through an analog signal and integrated and analyzed in the control workstation.

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

[0019] The negative pressure variable stiffness actuator provided by the present invention can realize contraction movement in the unchanged stiffness state; in the variable stiffness state, it can realize optional bending deformation by increasing the stiffness of the variable stiffness layer, and its adaptability is greatly improved compared with the traditional rigid actuator, and it has a high power-to-weight ratio, contraction characteristics similar to biological muscles, and excellent compliance, and is particularly suitable for application in flexible robots to realize the grasping of various types of objects. At the same time, the negative pressure variable stiffness actuator uses a spring as the internal skeleton, and can characterize the movement of the actuator body through the change of inductance to realize the self-sensing function. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a longitudinal cross-sectional schematic diagram of a negative pressure variable stiffness actuator provided by an embodiment of the present invention;

[0021] Figure 2 yes Figure 1 A cross-sectional schematic diagram of the negative pressure variable stiffness actuator shown;

[0022] Figure 3a to Figure 3d It is a schematic diagram of setting different numbers of variable stiffness layers on the outer periphery of the sealed soft capsule;

[0023] Figures 4a to 4c is a schematic diagram of the driver of this 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 in this embodiment;

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

[0026] Figure 6 is a structural block diagram of a negative pressure variable stiffness drive system provided by an embodiment of the present invention;

[0027] Figure 7 It is a comparison chart of experimental data and theoretical data of the self-sensing function of a negative pressure variable stiffness actuator provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] 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.

[0029] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] This embodiment provides a negative pressure variable stiffness driver, including a negative pressure source and a driver body, referring to Figure 1 and Figure 2The driver body includes a sealed soft bag 1, an elastic skeleton 2 and a variable stiffness layer 3; the negative pressure source is connected to the sealed soft bag 1 through a first air tube 4; the elastic skeleton 2 is embedded in the sealed soft bag to support the sealed soft bag 1; the variable stiffness layer 3 is fixed on the wall of the sealed soft bag 1, and the negative pressure source is connected to the variable stiffness layer 3 through a second air tube 5. When air is pumped into the variable stiffness layer 3 and negative pressure is formed inside the variable stiffness layer 3, the stiffness of the variable stiffness layer 3 increases, and the stiffness on the driver body is asymmetric and bends toward the opposite side where the variable stiffness layer 3 is installed. When air is pumped into the sealed soft bag 1 and negative pressure is formed inside the sealed soft bag 1, and at the same time the internal air pressure of the variable stiffness layer 3 is restored to atmospheric pressure, the driver body performs a contraction movement.

[0031] Specifically, the negative pressure source is a vacuum pump, and the first air tube 4 and the second air tube 5 are both PU air tubes with an inner diameter of 2.5 mm and an outer diameter of 4 mm.

[0032] The sealed soft capsule 1 includes a PE film tube 11 and a sealing plug 12, and the two sealing plugs 12 are respectively sealed and covered on the two ends of the PE film tube 11. In this embodiment, the sealing plug 12 is prepared by 3D printing technology, the selected 3D printing material is PLA, and the sealing plug 12 is cured by ultraviolet light to ensure the airtight effect.

[0033] The elastic skeleton 2 is used to support the inner wall of the PE film tube 11. In this embodiment, the elastic skeleton 2 is a steel coil 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 skeleton 2 can be changed according to the needs of different scenarios. The elastic skeleton 2 can be stretched and contracted along its own length direction and bent outward. The length direction of the elastic skeleton 2 is parallel to the length direction of the PE film tube 11.

[0034] The variable stiffness layer 3 is attached to the outer periphery of the PE film cylinder 11. The driver body includes at least one variable stiffness layer 3. All variable stiffness layers 3 are spaced apart along the circumferential direction of the PE film cylinder 11. In practical applications, the number and position distribution of the variable stiffness layers 3 are not limited. Figure 3a to Figure 3d , respectively showing the application mode of setting 1 to 4 variable stiffness layers 3 on the outer periphery of the sealed soft bag 1. It is easy to understand that one or more of the multiple variable stiffness layers 3 can be selectively evacuated to form negative pressure, so that the driver body can bend in an optional direction. For example, only one variable stiffness layer 3 is evacuated to achieve unidirectional bending (since the stiffness of the opposite side of the variable stiffness layer 3 is small, the bending direction is the direction of the side opposite to the variable stiffness layer 3). The variable stiffness layers 3 on the left and right sides are evacuated to achieve left and right swinging of the driver body. The more the number of variable stiffness layers 3, the more directions of bending deformation that the driver body can choose.

[0035] Based on the fact that the negative pressure variable stiffness actuator of this embodiment has the characteristic of optional bending, the actuator of this embodiment can realize various types of grasping according to the different shapes of objects. Figure 4a , the two actuators bend inwards, which can realize the grasping of general objects; refer to Figure 4b , the two actuators bend outwards against the cavity inside the object to achieve grasping; refer to Figure 4c , a single drive bending can achieve the hooking of objects.

[0036] The variable stiffness mechanisms of the variable stiffness layer include but are 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: Figure 5a , a layer interference structure is composed of sheets of flexible material placed in an airtight shell. When no negative pressure is applied, the layers in the layer interference structure can slide freely relative to each other, and the whole has low stiffness. When the negative pressure source is controlled to evacuate, the increased friction causes each layer of material to couple with its adjacent layers. The entire structure behaves like a cohesive "beam" rather than independent discrete layers. The stiffness of the interference structure is high until the shear stress induced in the "beam" is able to exceed the friction stress caused by the applied negative pressure.

[0038] Specifically, the principle of particle interference is as follows: particle interference usually consists of particle elements in an airtight shell. When no negative pressure is applied, the particles move freely with each other and behave like liquid. When pressure is applied, the grains are constrained and the structure transforms into a solid state.

[0039] Specifically, the principle of fiber interference is as follows: Fiber interference consists of longitudinal fibers in an airtight shell. 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: Figure 5b , fiber interference consists of longitudinal fibers in an airtight shell. 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] Reference Figure 6 The present embodiment also provides a negative pressure variable stiffness drive system, including a power supply, a signal acquisition card, a pneumatic valve, a negative pressure variable stiffness driver, an inductance measurement module and a control workstation, wherein 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 both connected to a pneumatic valve, which can be a solenoid valve or a proportional valve. The signal acquisition card in the computer outputs an analog signal to control the pneumatic valve to adjust the size and direction of the air pressure, thereby controlling the air pressure inside the sealing soft bag 1 and the variable stiffness layer 3 respectively, so as to achieve different functions.

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

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

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

[0046] After the variable stiffness layer 3 completes the stiffness change, the internal drive layer is evacuated, and the driver body is bent and deformed;

[0047] Turn off the negative pressure source and the driver body returns to its original state.

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

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A negative pressure variable stiffness actuator, characterized in that: The invention comprises a negative pressure source and a driver body, wherein the driver body comprises a sealing soft bag, an elastic skeleton and a variable stiffness layer; the negative pressure source is connected to the sealing soft bag through a first air tube; the elastic skeleton is embedded in the sealing soft bag to support the sealing soft bag; the variable stiffness layer is fixed on the wall of the sealing soft bag, and the negative pressure source is connected to the variable stiffness layer through a second air tube; When air is pumped into the variable stiffness layer and negative pressure is formed inside the variable stiffness layer, the stiffness of the variable stiffness layer increases, the stiffness on the driver body becomes asymmetric, and bends toward the opposite side where the variable stiffness layer is installed; when air is pumped into the sealed soft bag and 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 contracts.

2. The negative pressure variable stiffness actuator according to claim 1, characterized in that: The sealing soft bag comprises a film tube and a sealing plug, wherein the two sealing plugs are respectively sealed and covered on two ends of the film tube, and the elastic frame supports the inner wall of the film tube.

3. The negative pressure variable stiffness actuator according to claim 2, characterized in that: The elastic skeleton is a spring, and the elastic skeleton can be stretched and retracted along its own length direction and bent toward the outside. The length direction of the elastic skeleton is parallel to the length direction of the film tube.

4. The negative pressure variable stiffness actuator according to claim 2, characterized in that: 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 variable stiffness layers are distributed at intervals along the circumferential direction of the film cylinder.

5. The negative pressure variable stiffness actuator according to claim 2, characterized in that: The sealing plug is prepared by 3D printing technology, and the sealing plug is cured by ultraviolet light to ensure the airtight effect.

6. The negative pressure variable stiffness actuator according to claim 1, characterized in that: The variable stiffness mechanism of the variable stiffness layer is layer interference, particle interference, fiber interference or electrostatic layer interference.

7. The negative pressure variable stiffness actuator according to claim 1, characterized in that: The variable stiffness structure of the variable stiffness layer is a layer interference structure. When air is not pumped into the variable stiffness layer, the layer interference structure inside the variable stiffness layer can slide relatively freely, and the variable stiffness layer has a lower stiffness. When air is pumped into the variable stiffness layer to form a negative pressure inside the variable stiffness layer, adjacent layer interference structures inside the variable stiffness layer are coupled to each other, and the stiffness of the variable stiffness layer becomes greater.

8. The negative pressure variable stiffness actuator according to claim 1, characterized in that: The variable stiffness structure of the variable stiffness layer is an electrostatic adsorption structure, which is achieved by placing the positive electrode sheet and the negative electrode sheet relative to each other and connecting them to 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, 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, the two cannot slide relative to each other, and the stiffness of the variable stiffness layer becomes greater.

9. A negative pressure variable stiffness drive system, characterized in that: The device comprises a signal acquisition card, a pneumatic valve, an inductance measurement module, a control workstation and the negative pressure variable stiffness driver as claimed in claim 3, wherein the first air pipe and the second air pipe are both connected to the pneumatic valve; the signal acquisition card outputs an analog signal to control the pneumatic valve to adjust the size and direction of the air pressure, thereby respectively controlling the air pressure inside the sealing soft bag and the variable stiffness layer, so as to achieve different functions; The control workstation is electrically connected to 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, and the measured data is input back to the signal acquisition card through an analog signal and integrated and analyzed in the control workstation.

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