CN115674276A - Triboelectric type variable-stiffness soft paw state monitoring sensor and testing method thereof - Google Patents

Abstract

The invention provides a triboelectric type rigidity-variable soft paw state monitoring sensor and a testing method thereof. The sensor comprises an angle monitoring unit and a rigidity monitoring unit, wherein the angle monitoring unit comprises a silica gel substrate and a liquid metal electrode, and signal output ports are arranged at the tail ends of the two sides of the liquid metal electrode to monitor resistance change; the rigidity monitoring unit comprises an aluminum ball electrode and an external wrapping device, the external wrapping device is connected through a silica gel adhesive, and the aluminum ball is filled in the wrapping device. The aluminum ball can be used as a detection element and a rigidity adjusting element of the finger in the integral structure of the soft finger. When the paw is bent, the liquid metal layer stretches to change the resistance, and when the paw is changed in rigidity, the external wrapping device is in contact with the aluminum ball to change the voltage of the aluminum ball electrode, so that different electric signals are generated along with the change of the rigidity. The invention can realize the detection of the bending angle and the rigidity of the soft paw and has the advantages of wide measurement range, high measurement precision, long service life and the like.

Description

A triboelectric variable stiffness soft gripper state monitoring sensor and its testing method

technical field

The invention belongs to the technical field of sensors, and in particular relates to a triboelectric variable stiffness software gripper state monitoring sensor and a testing method thereof.

Background technique

With the development of the logistics industry, traditional logistics has been unable to meet the needs of the current fast-paced society due to its low timeliness and high cost in warehousing and sorting, which has become the main reason hindering the development of the logistics industry. In recent years, intelligent logistics has developed vigorously. Through intelligent technical means such as cyber-physical systems and the Internet of Things, intelligent analysis can be realized, thereby improving the efficiency of logistics operations. In order to improve the efficiency and flexibility of unmanned sorting, rigid manipulators are widely used in sorting system and achieved remarkable results. However, most rigid manipulators are made of metal materials, which have poor safety and limited adaptability. Especially in the process of sorting fragile and brittle objects such as fruits and eggs, it is easy to cause skin damage and it is difficult to achieve non-destructive sorting, resulting in certain Economic losses. In recent years, due to its inherent flexibility and strong adaptability, soft grippers have attracted widespread attention and are expected to achieve non-destructive sorting. They have been widely used in the manufacturing industry.

As a bridge connecting machines and computers, sensors are crucial in the process of intelligence. On the one hand, the soft gripper needs sensors to monitor the clamping behavior. On the other hand, it needs to be able to simulate the human hand under the premise of ensuring flexibility, and change the stiffness when grasping different heavy objects to enhance the robustness. The potentiometer and encoder in the traditional sensor limit the nonlinear deformation of the soft gripper, which affects the flexibility of the soft gripper, and is not suitable for the field of clamping behavior monitoring of the soft gripper. At present, the common behavior monitoring methods of soft paws include light detection, conductive nanocomposite materials and electromagnetic effects. However, the above method still has some disadvantages, such as the usual visual recognition does not work in a dark space, adding a light source alone will make the mechanism too complicated, and the detection of electromagnetic effects requires an additional magnetic field.

Therefore, there is an urgent need to design a new monitoring structure with simple structure, easy integration, high precision, and stability and reliability, which can not only meet the demand for variable stiffness of the gripper, but also monitor various parameters of the gripper in real time, so as to meet the needs of miniaturization and intelligence of modern mechanical equipment. needs.

Contents of the invention

The purpose of the present invention is to solve the problem that it is necessary to design a variable stiffness soft gripper state monitoring sensor with simple structure, easy integration, high precision, stability and reliability to meet the current intelligent sorting in the logistics industry, and proposes a triboelectric variable Stiffness soft gripper state monitoring sensor and testing method thereof. The sensor and its testing method can realize real-time monitoring of the bending angle and stiffness of the soft gripper.

The present invention is achieved through the following technical solutions. The present invention proposes a triboelectric variable stiffness soft gripper state monitoring sensor, the sensor includes: an angle monitoring unit 2 and a stiffness monitoring unit 3, and the angle monitoring unit 2 includes an upper layer The substrate 21, the liquid metal electrode layer 22 and the lower substrate 23, the stiffness monitoring unit 3 includes a substrate 31, an aluminum ball electrode 32, an aluminum ball sleeve 33 and a confining layer 34, wherein the aluminum ball sleeve 33 has an air extraction hole 331, The upper substrate 21 and the substrate 31 overlap.

Further, the upper substrate 21 of the angle monitoring unit 2 is connected to the soft gripper 1 through Sil-Poxy silicone adhesive, the lower substrate 23 is cast on the upper substrate 21, and the liquid metal electrode layer 22 is injected into the channel between the upper substrate 21 and the lower substrate 23 through a syringe.

Further, the base 31 of the stiffness monitoring unit 3 is connected to the aluminum ball sleeve 33 through Sil-Poxy silica gel adhesive, the aluminum ball sleeve 33 is connected to the limiting layer 34 through Sil-Poxy silica gel adhesive, and the aluminum ball electrode 32 is filled with A rectangular parallelepiped chamber composed of a full base 31 , an aluminum ball sleeve 33 and a restrictive layer 34 .

Further, the materials of the upper substrate 21 and the lower substrate 23 are both Dragon skin30, and the liquid metal is liquid gallium indium tin bismuth alloy.

Further, the aluminum ball electrode 32 is composed of a solid aluminum ball, the material of the aluminum ball sleeve 33 is Dragon skin30, and the material of the limiting layer 34 is epoxy resin.

Further, the liquid metal electrode layer 22 includes 8 channels, each channel is arranged in parallel, and the overall shape is rectangular. The length of each channel is 133 mm and the width is 1 mm. The overall length of the liquid metal electrode layer 22 is 136 mm. The width is 24.5mm.

Further, the ends of both sides of the liquid metal electrode layer 22 are provided with output ports to reserve space for the arrangement of electrical signal output wires. The length of the output ports on both sides is 5 mm and the width is 4 mm.

Further, with the bending of the soft gripper 1, the upper substrate 21 and the lower substrate 23 are stretched, the channel in the middle is narrowed, the liquid metal electrode layer 22 becomes thinner and longer, and the resistance changes, and the resistance changes with the degree of bending. change with change.

Further, when the stiffness monitoring unit 3 is pumping air, the contact area between the silica gel in the cuboid chamber and the aluminum ball electrode 32 changes as the air pressure changes, and the voltage of the aluminum ball electrode 32 varies with the contact area with the silica gel. change with changes.

The present invention proposes a test method for the state monitoring sensor of the triboelectric variable stiffness soft gripper, the method specifically includes the following steps:

Step S1: Use the electrostatic collection device to record the electrical signal generated by the triboelectric variable stiffness soft gripper state monitoring sensor, and convert the original sinusoidal signal into a square wave signal through the signal processing module to improve the stability of the signal and reduce the complexity of the detection signal;

Step S2: Use a professional camera to record the bending angle and pumping pressure of the soft gripper 1;

Step S3: According to the output electrical signal and the recorded angle and pressure, the bending angle of the soft gripper 1 is characterized by the change of resistance, and the stiffness of the soft gripper 1 is characterized by the change of voltage.

Beneficial effects of the present invention:

(1) In the sensor proposed by the present invention, when the claw is bent, the claw drives the angle monitoring unit to stretch and bend, the length of the liquid metal electrode in the angle monitoring unit increases, the cross-sectional area decreases, and the resistance changes accordingly. The output resistance value will change synchronously with the bending angle of the claw, so the function relationship between the bending angle of the claw and the resistance can be obtained by collecting and summarizing the resistance values of different bending angles.

(2) For the sensor proposed by the present invention, when the grip becomes rigid, the gap between each aluminum ball in the aluminum ball electrode decreases, the contact tightness increases, the contact area with the external silica gel increases, and the voltage changes accordingly. The output voltage will change synchronously with the pumping pressure, so the functional relationship between the claw stiffness and the voltage can be obtained by collecting the voltage value and the gripper stiffness value under different pumping pressures. Since the sensor is integrated with the variable stiffness structure, it has a long service life and high stability, and can detect the angle and speed of the soft gripper. It has self-driven sensing, wide detection range, and high measurement accuracy. and long service life.

(3) The present invention has the characteristics of miniaturization and integration, and can realize real-time monitoring of the bending angle and stiffness of the gripper under the premise of maintaining the integrity and functional integrity of the gripper. Development provides theoretical and experimental basis.

Description of drawings

Fig. 1 is the structure schematic diagram of the state monitoring sensor of triboelectric variable stiffness software gripper according to the present invention;

Fig. 2 is a schematic structural view of the angle monitoring unit in the triboelectric variable stiffness soft gripper state monitoring sensor of the present invention;

Fig. 3 is a schematic structural view of the liquid metal electrode layer in the angle detection unit of the present invention;

Fig. 4 is an enlarged schematic diagram of place A in Fig. 3;

Fig. 5 is a structural schematic diagram of the stiffness monitoring unit in the triboelectric variable stiffness soft gripper state monitoring sensor of the present invention;

Fig. 6 is the flow chart of the test method of the triboelectric variable stiffness software gripper state monitoring sensor according to the present invention;

Fig. 7 is a schematic diagram of the voltage characteristics of the triboelectric variable stiffness soft gripper state monitoring sensor at different frequencies according to the present invention;

Fig. 8 is the monitoring schematic diagram of the state monitoring sensor of the triboelectric variable stiffness software gripper according to the present invention, wherein (a) represents the fitting curve schematic diagram of bending angle and resistance; (b) represents the fitting of gripper stiffness and voltage Schematic diagram of the curve.

Fig. 9 is a result diagram of the durability test of the triboelectric variable stiffness soft gripper state monitoring sensor according to the present invention;

Explanation of reference signs: 1-soft gripper; 2-angle monitoring unit; 21-upper base; 22-liquid metal electrode layer; 23-lower base; 3-stiffness monitoring unit; 31-base; 32-aluminum ball electrode; 33-aluminum ball sleeve; 34-restriction layer.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

1-9, the present invention proposes a triboelectric variable stiffness soft gripper state monitoring sensor, the sensor includes: an angle monitoring unit 2 and a stiffness monitoring unit 3, the angle monitoring unit 2 includes an upper substrate 21, The liquid metal electrode layer 22 and the lower substrate 23, the stiffness monitoring unit 3 includes a substrate 31, an aluminum ball electrode 32, an aluminum ball sleeve 33 and a limiting layer 34, wherein an air extraction hole 331 is opened on the aluminum ball sleeve 33, and the upper layer The base 21 and the base 31 are coincident.

The upper substrate 21 of the angle monitoring unit 2 is connected to the soft gripper 1 through Sil-Poxy silicone adhesive, the lower substrate 23 is cast on the basis of the upper substrate 21, and the liquid metal electrode layer 22 is passed through a syringe It is formed by injecting into the channel between the upper substrate 21 and the lower substrate 23 . The liquid metal electrode is injected into the channel between the upper and lower substrates as the electrode material. After the injection, the liquid metal should completely fill the inside of the channel, and each prepared liquid metal electrode has the same initial resistance.

The base 31 of the stiffness monitoring unit 3 is connected to the aluminum ball sleeve 33 through Sil-Poxy silica gel adhesive, the aluminum ball sleeve 33 is connected to the limiting layer 34 through Sil-Poxy silica gel adhesive, and the aluminum ball electrode 32 fills the base 31 1. A cuboid chamber composed of the aluminum ball sleeve 33 and the restricting layer 34.

Both the upper substrate 21 and the lower substrate 23 are made of Dragon skin30, and the liquid metal is liquid gallium indium tin bismuth alloy.

The aluminum ball electrode 32 is composed of a solid aluminum ball, the material of the aluminum ball sleeve 33 is Dragon skin 30, and the material of the limiting layer 34 is epoxy resin.

The liquid metal electrode layer 22 includes 8 channels, each channel is arranged in parallel, each channel has the same size and the same spacing, and the overall shape is rectangular. The length of each channel is 133 mm and the width is 1 mm. The liquid metal electrode layer 22 The overall length is 136mm and the overall width is 24.5mm.

Signal output ports are provided at both ends of the liquid metal electrode layer 22 to monitor resistance changes, and reserve space for the arrangement of electrical signal output wires. The length of the output ends on both sides is 5 mm, and the width is 4 mm.

The working principle of the angle monitoring unit 2 is: with the bending of the soft gripper 1, the upper substrate 21 and the lower substrate 23 are stretched, the channel in the middle is narrowed, the liquid metal electrode layer 22 becomes thinner and longer, and the resistance changes. And the resistance changes with the degree of bending.

The working principle of the stiffness monitoring unit 3 is as follows: the upper side of the aluminum ball sleeve 33 is provided with a through hole for connecting a pipeline to pump air to the aluminum ball electrode 32 . When the aluminum ball sleeve 33 is pumped through the air extraction hole 331, the cuboid cavity formed by the base 31, the aluminum ball sleeve 33 and the confining layer 34 is sunken inward under the action of the external air pressure, reducing the distance between the aluminum balls in the aluminum ball electrode 32. The gap improves the stiffness of the stiffness monitoring unit 3, suppresses the bending of the soft gripper 1, and the stiffness increases with the increase of the pumping air pressure. At the same time, the silica gel of the cuboid chamber and the aluminum of the aluminum ball electrode 32 The contact area of the ball increases with the increase of the pumping air pressure. At this time, the gap between the aluminum ball electrode 32 and the external silica gel decreases, and a potential difference is generated, that is, an open circuit voltage. After the pumping is completed, due to the difference in electronegativity, electrons flow from the ground to the aluminum ball electrode, continuously generating voltage signals. When the air suction hole 331 releases the vacuum pressure on the aluminum ball sleeve 33 , the force of the external air pressure is released, and the stiffness of the stiffness monitoring unit 3 decreases. The negative charge on the surface of the aluminum ball electrode 32 drives free electrons to flow from the aluminum ball electrode 32 to the ground, resulting in the accumulation of positive charges in the outer silica gel, generating a voltage signal in the opposite direction.

The present invention proposes a test method for the state monitoring sensor of the triboelectric variable stiffness soft gripper, the method specifically includes the following steps:

Step S1: Use the electrostatic collection device to record the electrical signal generated by the triboelectric variable stiffness soft gripper state monitoring sensor, and convert the original sinusoidal signal into a square wave signal through the signal processing module to improve the stability of the signal and reduce the complexity of the detection signal;

Step S2: Use a professional camera to record the bending angle and pumping pressure of the soft gripper 1;

Step S3: According to the output electrical signal and the recorded angle and pressure, the bending angle of the soft gripper 1 is characterized by the change of resistance (corresponding the resistance and the bending angle to obtain a function curve), and the stiffness of the soft gripper 1 is characterized by the change of voltage (the The function curve is obtained corresponding to the voltage and the stiffness of the gripper).

As shown in Figure 7, it is a schematic diagram of the voltage characteristics of the triboelectric variable stiffness software gripper state monitoring sensor at different frequencies. The experimental results show that the voltage signal amplitude of the sensor according to the present invention will change as the gripper variable stiffness frequency increases. , but gradually tends to be stable.

As shown in Figure 8, it is the monitoring schematic diagram of the triboelectric type variable stiffness soft gripper state monitoring sensor according to the present invention. The experimental results show that the resistance of the sensor according to the present invention has a certain linear relationship with the bending angle of the gripper. The stiffness and the voltage also have a certain linear relationship, and the resistance signal and voltage signal of the sensor in the present invention can better reflect the bending information of the gripper.

As shown in Figure 9, it is the result of the durability test of the triboelectric variable stiffness soft gripper state monitoring sensor according to the present invention, and the experimental results show that its output voltage amplitude is after 1500 continuous bending stiffness changes (1.5 hours). It is still stable at 9V without obvious attenuation, reflecting the super long service life of the sensor of the present invention.

Since the variable stiffness structure of the sensor is integrated with the sensing structure, it has a long service life and high stability, and can realize self-driven sensing, wide detection range and high detection accuracy.

The triboelectric variable-stiffness software gripper state monitoring sensor proposed by the embodiment of the present invention has the characteristics of miniaturization and integration, and can realize real-time monitoring of the gripper's bending angle and stiffness under the premise of the gripper's structural integrity and functional integrity. The test provides a theoretical and experimental basis for the development of new self-driving and self-sensing intelligent bearings.

A kind of triboelectric variable stiffness soft gripper state monitoring sensor and its test method proposed by the present invention have been introduced in detail above. In this paper, specific examples have been used to illustrate the principle and implementation of the present invention. The above examples The description is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and scope of application. In summary , the contents of this specification should not be construed as limiting the present invention.

Claims (10)

1. A triboelectric type variable stiffness software gripper state monitoring sensor, is characterized in that, said sensor comprises: angle monitoring unit (2) and stiffness monitoring unit (3), and described angle monitoring unit (2) comprises upper substrate (21), liquid metal electrode layer (22) and lower floor substrate (23), described stiffness monitoring unit (3) comprises substrate (31), aluminum ball electrode (32), aluminum ball sleeve (33) and restriction layer (34 ), wherein the aluminum ball sleeve (33) has an air extraction hole (331), and the upper substrate (21) and the substrate (31) overlap. 2. The sensor according to claim 1, characterized in that, the upper substrate (21) of the angle monitoring unit (2) is connected to the soft gripper (1) by Sil-Poxy silica gel adhesive, and the lower substrate (23) is cast on the basis of the upper base (21), and the liquid metal electrode layer (22) is injected into the channel between the upper base (21) and the lower base (23) through a syringe. 3. The sensor according to claim 1, characterized in that, the base (31) of the stiffness monitoring unit (3) is connected with the aluminum ball sleeve (33) by Sil-Poxy silica gel adhesive, and the aluminum ball sleeve (33 ) and the confinement layer (34) are connected by Sil-Poxy silica gel adhesive, and the aluminum ball electrode (32) fills the cuboid cavity formed by the substrate (31), the aluminum ball sleeve (33) and the confinement layer (34). 4. The sensor according to claim 1, characterized in that, the materials of the upper substrate (21) and the lower substrate (23) are both Dragon skin30, and the liquid metal is liquid gallium indium tin bismuth alloy. 5. The sensor according to claim 1, characterized in that, the aluminum ball electrode (32) is composed of a solid aluminum ball, the material of the aluminum ball sleeve (33) is Dragon skin30, and the material of the limiting layer (34) is epoxy resin . 6. The sensor according to claim 1, characterized in that, the liquid metal electrode layer (22) comprises 8 channels, each channel is arranged in parallel, the overall shape is rectangular, the length of each channel is 133 mm, and the width is 1 mm , the overall length of the liquid metal electrode layer (22) is 136 mm, and the overall width is 24.5 mm. 7. The sensor according to claim 6, characterized in that, the ends of both sides of the liquid metal electrode layer (22) are provided with output ports to reserve space for the arrangement of electrical signal output wires, and the length of the output ends on both sides is 5mm , the width is 4mm. 8. The sensor according to claim 1, characterized in that, with the bending of the soft gripper (1), the upper substrate (21) and the lower substrate (23) are stretched, the channel in the middle is narrowed, and the liquid metal electrode The layer (22) becomes thinner and longer, the resistance changes, and the resistance changes with the degree of bending. 9. The sensor according to claim 3, characterized in that, when the stiffness monitoring unit (3) is pumping air, the silica gel in the cuboid chamber and the aluminum ball contact area of the aluminum ball electrode (32) increase with the increase of the pumping air pressure. Change and change, the voltage of aluminum ball electrode (32) changes along with the change of contact area with silica gel. 10. A method for testing the sensor according to any one of claims 1-9, wherein the method specifically comprises the following steps: Step S1: Use the electrostatic collection device to record the electrical signal generated by the triboelectric variable stiffness soft gripper state monitoring sensor, and convert the original sinusoidal signal into a square wave signal through the signal processing module to improve the stability of the signal and reduce the complexity of the detection signal; Step S2: Use a professional camera to record the bending angle and pumping pressure of the soft gripper (1); Step S3: According to the output electrical signal and the recorded angle and pressure, the bending angle of the soft gripper (1) is characterized by the change of resistance, and the stiffness of the soft gripper (1) is characterized by the change of voltage.

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