CN111397773B

CN111397773B - A kind of flexible fingertip touch sensor and preparation method thereof

Info

Publication number: CN111397773B
Application number: CN201911303848.0A
Authority: CN
Inventors: 孟海良; 马小龙; 鲍官军
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Dongguan Xunli Intelligent Technology Co ltd
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2021-07-30
Anticipated expiration: 2039-12-17
Also published as: CN111397773A

Abstract

A flexible fingertip contact sensor and a preparation method thereof aim to solve the technical problems that in the prior art, the fingertip contact sensor cannot detect space acting force and is high in manufacturing cost, so that large-scale commercial application cannot be realized. The invention comprises a Hall sensor for detecting pressure change, wherein the Hall sensor is arranged on a sensor fixing shaft and comprises a first sensor group and a second sensor group, one end of the sensor fixing shaft is provided with a first mounting groove for mounting the first sensor group, the peripheral surface of the sensor fixing shaft is provided with a second mounting groove for mounting the second sensor group, the other end of the sensor fixing shaft is provided with a mounting hole for mounting a manipulator, pins of the first sensor group and the second sensor group are connected through a conducting piece arranged on the sensor fixing shaft, the peripheral surface of the sensor fixing shaft is provided with a protective layer, the protective layer is provided with a rubber magnetic paste, and one side of the protective layer, which is far away from the sensor fixing shaft, is provided with a forming layer.

Description

Flexible fingertip contact sensor and preparation method thereof

Technical Field

The invention relates to the technical field of bionic robots or multi-dexterous hands, in particular to a flexible fingertip contact sensor and a preparation method thereof.

Background

During maneuvering and exploration tasks, the manipulator is often required to respond effectively to unknown objects and obstacles. In conventional industrial applications, the control of the end effector by the robot is achieved by embedding data models of the simulated object and environment into the control algorithm, so that the manipulators can only manipulate known objects and work in a structured environment, which means that their reaction to accidents is slow, and if there is no detailed operating environment model, the real-time measurement of the contact force is crucial to whether the robot can perform the task efficiently and safely. The touch perception is an important component of the autonomous smart hand operation of the robot and provides information such as the acting force and the surface characteristic of the contact point of the manipulator and an object. Although pressure sensors are of various types and are commercialized, ordinary pressure sensors often extract force information of only a single point and cannot help a robot to sense the environment. In recent years, for the problem, many scholars propose an array type architecture, that is, a plurality of pressure sensors are adopted for array arrangement, so that information extraction of multipoint acting force can be realized, and then the position and the acting force magnitude of a stress point are obtained, which lays a foundation for human-like touch. However, it should be noted that in the operation process of the manipulator, fingertips are often subjected to space acting force rather than plane acting force, and although various flexible tactile sensors are designed by domestic and foreign researchers, most of them are in the experimental research stage, and there are not many flexible tactile sensors produced, and there are fewer flexible tactile sensors widely used in robots. Currently, high-end fingertip sensors are widely used by many manufacturers who develop high-dexterity manipulators, but the fingertip sensors account for a large part of the cost of the manipulator.

Chinese patent application No. CN201811301176.5 discloses a finger wearable flexible force tactile feedback device, which comprises a fingertip finger sleeve worn on the distal phalanx of a finger, a middle phalanx finger sleeve worn on the middle phalanx of the finger, a proximal phalanx finger sleeve worn on the proximal phalanx of the finger, an outer transmission rod with bending elasticity arranged on the back of the finger, and an inner transmission rod with bending elasticity arranged on the belly of the finger; one end of the outer transmission rod is fixed on the fingertip finger sleeve and sequentially penetrates through the finger back sides of the middle-section finger sleeve and the proximal-section finger sleeve, and the other end of the outer transmission rod is positioned on the hand back and is connected with an outer driver which applies push-pull force to the outer transmission rod; one end of the inner transmission rod is fixed on the fingertip finger sleeve and sequentially penetrates through the finger pulp sides of the middle-section finger sleeve and the proximal-section finger sleeve, and the other end of the inner transmission rod is positioned on the palm and connected with an inner driver which applies push-pull force to the inner transmission rod; the fingertip fingerstall is provided with a first contact type pressure sensor connected with the end part of the outer transmission rod, the fingertip fingerstall is provided with a second contact type pressure sensor connected with the end part of the inner transmission rod, and the inner wall of the contact part of the fingertip fingerstall and the finger belly is provided with a thin film type pressure sensor. The feedback device is light in structure and convenient to wear, the fingers can flexibly move and interact naturally, and force and touch feedback information is provided for the fingers; however, the device has a complex structure and occupies a large space, and is not suitable for the anthropomorphic development direction of the bionic robot.

Chinese patent application No. CN201710382607.4 discloses a multi-array fingertip tactile interaction device, which is connected with a robot through a serial line, and includes a capacitive multi-array sensor arranged on a flexible circuit board, a main control board provided with an I2C communication interface, and a data sampling chip provided with a digital-analog interface and an I2C communication interface; the capacitive multi-array sensor comprises an upper sensing polar plate, a lower sensing polar plate and a plurality of flexible micro-needles fixed between the upper sensing polar plate and the lower sensing polar plate, wherein the upper sensing polar plate and the lower sensing polar plate are bonded through chemical bonds of filled plasma; the upper and lower sensing electrode plates of the capacitive multi-array sensor are directly connected with a digital-analog interface of a data sampling chip, and the data sampling chip is connected with a main control board through an I2C communication interface.

The sensor adopted in the patent is a capacitive sensor, more touch sensing points can be formed in a smaller area, the size is smaller, the wiring is simple, and the measurement is stable; however, the interaction device cannot detect the space force and is high in manufacturing cost, so that the interaction device is not suitable for large-scale commercial application.

Disclosure of Invention

The invention provides a flexible fingertip contact sensor and a preparation method thereof, aiming at overcoming the technical problems that the fingertip contact sensor in the prior art cannot detect space acting force and has higher manufacturing cost, so that large-scale commercial application cannot be realized.

In order to achieve the above object, the present invention adopts the following technical solutions.

The utility model provides a flexible fingertip contact sensor, including the hall sensor who is used for detecting pressure variation, hall sensor lays on the sensor fixed axle, hall sensor includes first sensor group and second sensor group, the one end of sensor fixed axle is equipped with the first mounting groove that is used for installing first sensor group, be equipped with the second mounting groove that is used for installing the second sensor group on the global of sensor fixed axle, the other end of sensor fixed axle is equipped with the mounting hole that is used for installing the manipulator, the pin of first sensor group and second sensor group links to each other through arranging the conduction piece on the sensor fixed axle, be equipped with the inoxidizing coating on the outer peripheral face of sensor fixed axle, hall sensor and conduction piece all are located between sensor fixed axle and the inoxidizing coating, be equipped with rubber magnetic paste on the inoxidizing coating, the one side that the sensor fixed axle was kept away from to the inoxidizing coating is. In the prior art, most of low-cost flexible tactile sensors can only detect the acting force change on a plane, namely can only detect the acting force change in the x direction and the y direction, but cannot detect the acting force change in the z direction, but because the flexible tactile sensors are in a four-dimensional space and interact with a three-dimensional object, the detection of the acting force change in the z direction means the dimension transition of the bionic simulation similarity for the bionic subject; at present, most of flexible touch sensors capable of synchronously detecting acting forces in x, y and z directions in space are high in cost and are not suitable for large-scale commercial application. The invention provides a flexible fingertip contact sensor, wherein a first sensor group is arranged on the end surface of a sensor fixing shaft, a second sensor group is arranged on the circumferential surface of the sensor fixing shaft, a protective layer is sleeved on the circumferential surface of the sensor fixing shaft, the protective layer is made of platinum catalytic silicone rubber, a rubber magnetic paste is arranged on the protective layer, when the surface of the flexible fingertip contact sensor is subjected to pressure, the protective layer is extruded and deformed, the rubber magnetic paste connected with the protective layer synchronously generates displacement change, and a Hall sensor fixed on the sensor fixing shaft does not generate displacement change, so that the displacement change of the rubber magnetic paste can cause the change of the surface magnetic field force of the Hall sensor, further the analog quantity output value of the Hall sensor is changed, further, the second sensor group is used for detecting the acting force in the x and y directions in a space, and the first sensor group is used for detecting the acting force in the z direction in the space, due to the fact that the Hall sensors are arranged in an array framework, the action area of external force can be identified. The flexible fingertip contact sensor realizes the detection of space acting force by the cooperation of the Hall sensor, the rubber magnetic sticker and the protective layer made of platinum catalytic silicone rubber, and the manufacturing cost is lower because the components are common components or materials.

Preferably, the sensor fixed axle includes body and installed part, and body and installed part all are the column, and the diameter of installed part and body coaxial arrangement and installed part is less than the diameter of body, is equipped with the locating hole on the global of installed part, the axial extension of the one end of body and edge installed part is kept away from to the installation hole site, and the inner wall of installation hole personally submits the screw thread form. The sensor fixed shaft comprises a body and an installation part, the body is used for installing the Hall sensor, the installation part is used for being connected with the manipulator, and positioning holes are formed in the circumferential surface of the installation part.

Preferably, the circumferential surface of the body is provided with a first annular groove and a second annular groove which are both intersected with the second mounting groove, the second annular groove is positioned on one side of the first annular groove, which is far away from the first sensor group, and is arranged at intervals with the first annular groove, the conducting piece comprises a first conducting piece and a second conducting piece, the first conducting piece is fixed in the first annular groove, and the second conducting piece is fixed in the second annular groove. The first mounting groove and the second mounting groove are respectively used for mounting a first sensor group and a second sensor group, the sensor comprises a pin, a first annular groove and a second annular groove which are intersected with the second mounting groove are formed in the circumferential surface of the body, the first conduction piece is fixed in the first annular groove, the second conduction piece is fixed in the second annular groove, then the pin is welded with the first conduction piece or the second conduction piece, and finally the lead is connected with the first conduction piece and the second conduction piece; through the design, the conducting wires and the pins do not need to be correspondingly connected one by one, and the assembling and mounting mode of the flexible fingertip contact sensor is effectively simplified.

Preferably, the pins comprise a power pin, a grounding pin and a signal pin, the power pin is connected with the first conduction piece in a welding mode, the grounding pin is connected with the second conduction piece in a welding mode, the signal pin extends towards one end close to the installation piece along the axial direction of the body, and a heat shrink tube used for being insulated and separated from the conduction piece is sleeved on the signal pin. The signal pin is sleeved with a heat shrink tube used for being insulated and separated from the conducting piece, so that the stability of signal transmission is ensured.

Preferably, the conducting wires arranged along the length direction of the sensor fixing shaft are communicated with the first conducting piece and the second conducting piece, the conducting wires comprise a first conducting wire and a second conducting wire, and the first conducting wire and the second conducting wire are symmetrically arranged along the radial direction of the body.

As preferred, first mounting groove and second mounting groove are T type groove, and T type groove includes the horizontal groove and is used for carrying out spacing vertical groove to the pin, and vertical groove arranges along the length direction of sensor fixed axle, and the horizontal groove of first mounting groove is located the body and keeps away from the one end of installed part, and the vertical groove of first mounting groove and the vertical groove of second mounting groove along the length direction dislocation of body arrange. The vertical groove of the first mounting groove and the vertical groove of the second mounting groove are arranged along the length direction of the body in a staggered mode, the first sensor group and the second sensor group are arranged in a staggered mode in the mounting process, and integration of arrangement of the Hall sensors is achieved while the mounting area is saved.

Preferably, Smooth-On EcoFlex 0030 is used as the platinum-catalyzed silicone rubber. The Smooth-On EcoFlex 0030 type platinum-catalyzed silicone rubber is very soft after being cured, has good tensile tearing resistance, good elasticity and elongation, can be stretched by multiple times without tearing, and can rebound to the original size without deformation; the platinum catalytic silicone rubber can ensure that the protective layer and the forming layer can still be reset to the original shape after being deformed for multiple times, and the durability and the service life of the flexible fingertip contact sensor are greatly improved.

Preferably, the number of the hall sensors in the first sensor group and the second sensor group is 4, the rubber magnetic paste comprises a first magnetic paste group and a second magnetic paste group, a first rectangular groove used for packaging the first magnetic paste group is arranged on the end face of the protective layer, a second rectangular groove used for packaging the second magnetic paste group is arranged on the circumferential face of the protective layer, and the first rectangular groove and the second rectangular groove are both communicated along the thickness direction of the protective layer.

A preparation method of the flexible fingertip contact sensor comprises the following steps of:

(1) preparing a sensor fixing shaft, wherein four first mounting grooves are uniformly formed in the end face of the sensor fixing shaft, four second mounting grooves are uniformly formed in the circumferential surface of the sensor fixing shaft along the circumferential direction, first annular grooves and second annular grooves are formed in the circumferential surface of the sensor fixing shaft at intervals along the length direction of the sensor fixing shaft, a first conduction piece and a second conduction piece are sequentially embedded into the first annular groove and the second annular groove, a first sensor group and a second sensor group are respectively and correspondingly arranged in the first mounting groove and the second mounting groove, a power supply pin and the first conduction piece are welded, a grounding pin and the second conduction piece are welded, a heat shrink tube is sleeved on a signal pin, and conducting wires are welded on the first conduction piece, the second conduction piece and the signal pin;

(2) preparing a protective layer mold, wherein the protective layer mold is a hollow cylinder, the protective layer is made of two-component room temperature curing platinum catalytic silicone rubber which is prepared according to the proportion of 1:1, placing a flexible fingertip contact sensor into the protective layer mold, pouring the platinum catalytic silicone rubber into the protective layer mold, pumping out bubbles in the platinum catalytic silicone rubber under the negative pressure of 0.1MPa and keeping for 5 minutes, then placing the protective layer mold containing the platinum catalytic silicone rubber into an oven to be heated for 2 hours at the temperature of 50 ℃, and finally taking out the protective layer mold to be cooled and demolded;

(3) preparing a forming layer mold, wherein the forming layer mold is a hollow cylinder, the top of the forming layer mold is hemispherical, the forming layer mold is made of double-component room temperature curing platinum catalytic silicone rubber which is prepared according to the proportion of 1:1, placing a flexible fingertip contact sensor with a protective layer into the forming layer mold, pouring the platinum catalytic silicone rubber into the forming layer mold, pumping out air bubbles in the platinum catalytic silicone rubber under the negative pressure of 0.1MPa, keeping for 5 minutes, then placing the forming layer mold containing the platinum catalytic silicone rubber into an oven, heating for 2 hours at the temperature of 50 ℃, and finally taking out the forming layer mold, cooling and demolding.

In conclusion, the invention has the following beneficial effects: (1) the sensor can realize the detection of space acting force, has low manufacturing cost and can be suitable for large-scale commercial application; (2) the first sensor group and the second sensor group are arranged in a staggered mode in the installation process, so that the installation area is saved, and the arrangement integration of the Hall sensors is realized; (3) the protective layer and the forming layer can still be reset to the original shape after being deformed for multiple times, and the durability and the service life of the flexible fingertip contact sensor are greatly improved; (4) the flexible silica gel is used for skin affinity, has good consistency with the characteristics of human skin, and can also play an insulating role in a circuit in the sensor; (5) the manufacture is simple, and the measuring range and the sensitivity of the fingertip contact sensor can be adjusted by selecting rubber magnetic pastes with different magnetic forces and adjusting the distance between the rubber magnetic pastes and the surface of the Hall sensor.

Drawings

FIG. 1 is a schematic view of a fixed shaft structure of a sensor according to the present invention.

Fig. 2 is a schematic view of the hall sensor installation of the present invention.

Fig. 3 is a schematic view of a protective layer according to the present invention.

FIG. 4 is a schematic representation of a shaping layer of the present invention.

Fig. 5 is an assembly view of the present invention.

In the figure:

the rubber magnetic paste comprises a rubber magnetic paste 1, a first sensor group 2, a second sensor group 3, a first mounting groove 4, a second mounting groove 5, a conducting piece 6, a protective layer 7, a forming layer 8, a body 9, a mounting piece 10, a positioning hole 11, a first annular groove 12, a second annular groove 13, a first conducting piece 14, a second conducting piece 15, a power supply pin 16, a grounding pin 17, a signal pin 18, a heat shrink tube 19, a conducting wire 20, a first rectangular groove 21 and a second rectangular groove 22.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example (b):

as shown in fig. 1 to 5, a flexible fingertip contact sensor includes a hall sensor 1 for detecting pressure change, and is characterized in that the hall sensor is disposed on a sensor fixing shaft, the hall sensor includes a first sensor group 2 and a second sensor group 3, one end of the sensor fixing shaft is provided with a first mounting groove 4 for mounting the first sensor group, a second mounting groove 5 for mounting the second sensor group is disposed on the circumferential surface of the sensor fixing shaft, the other end of the sensor fixing shaft is provided with a mounting hole for mounting a manipulator, pins of the first sensor group and the second sensor group are connected by a conduction member 6 disposed on the sensor fixing shaft, a protective layer 7 is disposed on the circumferential surface of the sensor fixing shaft, the hall sensor and the conduction member are both located between the sensor fixing shaft and the protective layer, and a rubber magnetic sticker 1 is disposed on the protective layer, a forming layer 8 is arranged on one side of the protective layer, which is far away from the sensor fixing shaft; the sensor fixing shaft comprises a body 9 and an installation part 10, the body and the installation part are both columnar, the installation part and the body are coaxially arranged, the diameter of the installation part is smaller than that of the body, positioning holes 11 are formed in the peripheral surface of the installation part, the installation holes are located at one end, far away from the body, of the installation part and extend in the axial direction of the installation part, and the inner wall of each installation hole is threaded; the circumferential surface of the body is provided with a first annular groove 12 and a second annular groove 13 which are intersected with the second mounting groove, the second annular groove is positioned on one side of the first annular groove, which is far away from the first sensor group, and is arranged at intervals with the first annular groove, the conducting piece comprises a first conducting piece 14 and a second conducting piece 15, the first conducting piece is fixed in the first annular groove, and the second conducting piece is fixed in the second annular groove; the pins comprise a power supply pin 16, a grounding pin 17 and a signal pin 18, the power supply pin is connected with the first conducting piece in a welding mode, the grounding pin is connected with the second conducting piece in a welding mode, the signal pin extends towards one end close to the mounting piece along the axial direction of the body, and a heat shrinkage pipe 19 used for being insulated and separated from the conducting piece is sleeved on the signal pin; the lead wires 20 arranged along the length direction of the sensor fixing shaft are communicated with the first conducting piece and the second conducting piece, the lead wires comprise a first lead wire and a second lead wire, and the first lead wire and the second lead wire are symmetrically arranged along the radial direction of the body; the first mounting groove and the second mounting groove are both T-shaped grooves, each T-shaped groove comprises a horizontal groove and a vertical groove used for limiting the pins, the vertical grooves are arranged along the length direction of the sensor fixing shaft, the horizontal groove of the first mounting groove is positioned at one end, far away from the mounting piece, of the body, and the vertical grooves of the first mounting groove and the vertical grooves of the second mounting groove are arranged in a staggered mode along the length direction of the body; the protective layer and the forming layer are both made of platinum-catalyzed silicone rubber, and the platinum-catalyzed silicone rubber is Smooth-On EcoFlex 0030; the quantity of hall sensor is 4 in first sensor group and the second sensor group, and the rubber magnetic paste includes first magnetic paste group and second magnetic paste group, is equipped with the first rectangular channel 21 that is used for the first magnetic paste group of encapsulation on the terminal surface of inoxidizing coating, is equipped with the second rectangular channel 22 that is used for the second magnetic paste group of encapsulation on the global of inoxidizing coating, and first rectangular channel and second rectangular channel all link up along the thickness direction of inoxidizing coating.

As shown in fig. 2, the sensor fixing shaft sequentially comprises a body and an installation part from top left to bottom right, the body and the installation part are both cylindrical, the body and the installation part are coaxially arranged, the diameter of the body is larger than that of the installation part, a first installation groove is arranged on the upper end face of the body and is a T-shaped groove, a horizontal groove of the T-shaped groove is positioned on the upper end face of the body, vertical grooves of the T-shaped groove are positioned on the peripheral face of the body, the number of the first installation grooves is four, the first installation grooves are arranged along the circumferential direction of the body at equal included angles, the included angle between every two adjacent first installation grooves is 90 degrees, a first sensor group is arranged in the first installation grooves, wherein a detection element of a hall sensor is positioned in the horizontal groove, and a pin of the hall sensor extends along the axial direction of the body and is positioned in the vertical groove; the peripheral surface of the body is provided with second mounting grooves, the number of the second mounting grooves is four, the second mounting grooves are arranged along the circumferential direction of the body at equal included angles, the second mounting grooves are T-shaped grooves, the first mounting grooves and the second mounting grooves are arranged along the circumferential direction of the body at intervals, the first mounting grooves and the second mounting grooves are arranged along the axial direction of the body in a staggered manner, first annular grooves and second annular grooves are sequentially arranged below horizontal grooves of the second mounting grooves, the first annular grooves and the second annular grooves are arranged at intervals, first conduction pieces made of copper are arranged in the first annular grooves, second conduction pieces made of copper are arranged in the second annular grooves, power pins of the first sensor group and power pins of the second sensor group are welded with the first conduction pieces, grounding pins of the first sensor group and the second sensor group are welded with the second conduction pieces, and conducting wires are arranged along the length direction of the sensor fixing shaft and are connected with the first conduction pieces and the second conduction pieces; the outer peripheral face of the sensor fixing shaft is sleeved with a protective layer made of platinum catalytic silicone rubber, a first rectangular groove and a second rectangular groove are formed in the positions, corresponding to the horizontal groove of the T-shaped groove, of the protective layer respectively, the first rectangular groove is located on the end face of the protective layer, the second rectangular groove is located on the peripheral face of the protective layer, a first magnetic paste group is packaged in the first rectangular groove, a second magnetic paste group is packaged in the second rectangular groove, and a forming layer made of platinum catalytic silicone rubber is sleeved outside the protective layer.

Claims

1. a flexible fingertip touch sensor, comprising the Hall sensor in order to detect pressure change, it is characterized in that, the Hall sensor is arranged on the sensor fixed axis, the Hall sensor comprises the first sensor group and the second sensor group, the sensor One end of the fixed shaft is provided with a first installation groove for installing the first sensor group, the peripheral surface of the sensor fixed shaft is provided with a second installation groove for the installation of the second sensor group, and the other end of the sensor fixed shaft is provided with a robot arm. The mounting holes of the first sensor group and the second sensor group are connected through a conducting member arranged on the sensor fixing shaft. The outer peripheral surface of the sensor fixing shaft is provided with a protective layer, and the Hall sensor and the conducting member are located in the Between the sensor fixing shaft and the protective layer, a rubber magnet is arranged on the protective layer, and the side of the protective layer away from the sensor fixing shaft is provided with a molding layer. The protective layer and the molding layer are both made of platinum-catalyzed silicone rubber. The sensor fixing shaft includes The body and the mounting piece, the body and the mounting piece are both cylindrical, the mounting piece and the body are arranged coaxially, and the diameter of the mounting piece is smaller than the diameter of the body, the peripheral surface of the mounting piece is provided with a positioning hole, and the mounting hole is located on the mounting piece away from the body. One end of the sensor extends along the axial direction of the mounting piece, the inner wall of the mounting hole is threaded, the number of Hall sensors in the first sensor group and the second sensor group are both 4, and the rubber magnet includes the first magnet group and For the second magnetic sticker group, the end surface of the protective layer is provided with a first rectangular slot for encapsulating the first magnetic sticker group, and the peripheral surface of the protective layer is provided with a second rectangular slot for encapsulating the second magnetic sticker group. Both the groove and the second rectangular groove penetrate along the thickness direction of the protective layer.

2 . The flexible fingertip contact sensor according to claim 1 , wherein the peripheral surface of the body is provided with a first annular groove and a second annular groove both intersecting with the second installation groove, and the second annular groove is located on the side of the first annular groove away from the first sensor group and is spaced from the first annular groove, the conducting member includes a first conducting member and a second conducting member, and the first conducting member is fixed in the first annular groove Inside, the second conducting member is fixed in the second annular groove.

3. A flexible fingertip contact sensor according to claim 2, wherein the pins comprise power pins, ground pins and signal pins, the power pins are connected to the first conducting member by welding, and the ground pins are connected to each other by welding. The pin is connected to the second conducting piece by welding, the signal pin extends along the axial direction of the body toward the end close to the mounting piece, and a heat shrinkable tube is sleeved on the signal pin for insulating and separating from the conducting piece.

4 . The flexible fingertip touch sensor according to claim 3 , wherein the wires arranged along the length direction of the fixed axis of the sensor communicate with the first conducting member and the second conducting member, and the wires comprise the first conducting wire and the second conducting member 4 . Two conducting wires, the first conducting wire and the second conducting wire are symmetrically arranged along the radial direction of the body.

5. A flexible fingertip contact sensor according to claim 1, wherein the first installation groove and the second installation groove are both T-shaped grooves, and the T-shaped grooves comprise horizontal grooves and are used to limit the pins. The vertical groove is arranged along the length direction of the sensor fixing shaft, the horizontal groove of the first installation groove is located at the end of the body away from the mounting piece, the vertical groove of the first installation groove and the vertical groove of the second installation groove Displaced along the length of the body.

6 . The flexible fingertip contact sensor according to claim 1 , wherein the platinum-catalyzed silicone rubber is selected from Smooth-On EcoFlex 0030. 7 .

7. A method for preparing a flexible fingertip contact sensor according to any one of claims 1 to 6, characterized in that it comprises the steps of executing in the following order:

(1) Prepare the sensor fixed shaft. Four first installation grooves are evenly opened on the end surface of the sensor fixed shaft. Four second installation grooves are evenly formed on the circumferential surface of the sensor fixed shaft along the circumferential direction. A first annular groove and a second annular groove are spaced in the longitudinal direction, the first and second conductive members are inserted into the first annular groove and the second annular groove in turn, and the first sensor group and the second sensor group are respectively Install the first installation slot and the second installation slot correspondingly, weld the power supply pin to the first conduction piece, weld the ground pin to the second conduction piece, set the heat shrink tube on the signal pin, A conducting member, a second conducting member and welding wires on the signal pins;

(2) Prepare a protective layer mold. The protective layer mold is a hollow cylinder. The protective layer is made of two-component room temperature cured platinum-catalyzed silicone rubber prepared in a ratio of 1:1. The flexible fingertip touch sensor is placed in the protective layer. In the mold, the platinum-catalyzed silicone rubber was poured into the protective layer mold, and the air bubbles in the platinum-catalyzed silicone rubber were extracted under a negative pressure of 0.1 MPa and kept for 5 minutes, and then the protective layer mold containing the platinum-catalyzed silicone rubber was put into the mold. Heating in an oven at 50 °C for 2 hours, and finally taking out the protective layer mold and cooling and demoulding;

(3) Prepare a molding layer mold. The molding layer mold is a hollow cylinder with a hemispherical top. The molding layer is made of two-component room temperature-curing platinum-catalyzed silicone rubber prepared in a ratio of 1:1. The flexible fingertip contact sensor is put into the molding layer mold, and the platinum-catalyzed silicone rubber is poured into the molding layer mold and the air bubbles in the platinum-catalyzed silicone rubber are extracted under the negative pressure of 0.1MPa and kept for 5 minutes, and then the containing The forming layer mold of platinum-catalyzed silicone rubber was placed in an oven and heated at 50° C. for 2 hours. Finally, the forming layer mold was taken out and cooled and demolded.