A sensor for transmitting finger operations in VR devices

Abstract

The present invention provides a sensor for transmitting finger operations in VR devices, which consists of a four-component force sensor with four mutually separated and non-crosstalking piezoresistors and a force conduction structure with a rigid lining; the inner and outer layers of the structure are tightly fitted, the outer layer is a soft hemispherical shell, and the middle layer is a hard structure similar to a four-corner support frame; the force conduction structure is tightly connected to the packaging layer on the above-mentioned four-component force sensor through an adhesive layer; a set of equipment for sensor signal acquisition and transmission can realize remote data transmission through the equipped Bluetooth signal transmission module; therefore, compared with traditional flexible shear force sensors, the sensor of the present invention can achieve higher-dimensional shear force perception, not only can it perceive the magnitude of the shear force, but also has the ability to recognize the direction of the shear force at all angles.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a sensor for transmitting finger operations in VR equipment. Background Art

[0002] With the advancement and development of science and technology and the continuous improvement of people's living standards, traditional human-computer interaction methods—monitors paired with keyboards, mice, and joysticks—are no longer able to meet the demand for more three-dimensional and immersive interaction modes. The next generation of human-computer interaction interfaces has evolved into virtual reality (VR) and augmented reality (AR). The emergence of VR glasses has revolutionized the flat display model, bringing a visually immersive experience to our eyes and taking a significant step towards a fully immersive human-computer interaction experience. However, the interaction method currently used with VR glasses on the market is generally achieved through joysticks. While VR joysticks can accurately carry out a variety of user commands and include numerous buttons and functions, they are also generally heavy. Furthermore, the joystick operation mode undoubtedly significantly affects the user's immersive experience. In addition, some interaction solutions using smart gloves have also emerged on the market. These sensors at the joints and wrists monitor hand posture and position, allowing interaction with the terminal based on hand gestures. These smart gloves provide a more immersive experience in VR devices, but they also have the problem of being heavy and causing fatigue after wearing them for long periods of time. Therefore, the development of lightweight, compact, and high-performance VR interaction methods is necessary.

[0003] Flexible tactile sensors, also known as electronic skin, have the advantages of being thin, lightweight, having a low detection limit, high sensitivity, and being highly flexible. They can be well attached to human skin, deforming with human movement while maintaining stable performance. They have been widely used in the fields of medical health testing and human-computer interaction. However, current research on flexible tactile sensors mainly focuses on the perception of normal stress, and various methods of introducing microstructures are often used to improve sensor sensitivity. In addition, sensing shear force is also a major function of tactile receptors. The commonly used method is to use a force-conducting structure, such as a dome, assembled on the sensor surface to convert the shear force exerted on the device into the normal force of the pressure sensor, thereby realizing the perception of shear force. Although many studies have been able to sense shear force, achieving high-precision recognition of both the direction and magnitude of the shear force is still a major challenge in the field of flexible tactile sensors. Summary of the Invention

[0004] To solve the above problems, the present invention provides a sensor for transmitting finger operations in VR devices, which can realize full-angle force recognition and perfectly reproduce the user's operation instructions.

[0005] A sensor for transmitting finger operations in VR devices, comprising a force transmission structure, a four-component force sensor assembly, a voltage divider resistor assembly, an acquisition module, and a processing module;

[0006] The four-component force sensor assembly comprises, from top to bottom, an upper packaging layer 3, an upper electrode layer 4, a piezoresistive layer 5, a lower electrode layer 6, and a lower packaging layer 7. The upper electrode layer 4 is composed of four separate sector-shaped electrodes that can be combined into a full circle, and the lower electrode layer 6 is a complete circular electrode, thereby dividing the piezoresistive layer 5 located between the upper electrode layer 4 and the lower electrode layer 6 into four piezoresistors.

[0007] The voltage divider resistor assembly comprises four fixed resistors with the same resistance value, and one end of each fixed resistor is connected in series with a sector electrode, and the other end is connected to a common ground terminal;

[0008] The force transmission structure consists of a flexible micro-dome housing 1 and a rigid lining structure 2. The rigid lining structure 2 has four branches arranged in a cross pattern, each of which is bonded to an upper packaging layer 3. The projections of each branch on the upper packaging layer 3 correspond one-to-one with the projections of each sector-shaped electrode on the upper packaging layer 3. The rigid lining structure 2 is used to transmit the pressure exerted on the flexible micro-dome housing 1 to each piezoresistor.

[0009] When measuring the pressure on the flexible micro-dome housing 1, a constant voltage is applied to the lower electrode layer 6, and the divided voltage of the four fixed resistors is measured by the acquisition module. The pressure component borne by each piezoresistor is different, and the divided voltage of the corresponding fixed resistor is different;

[0010] The processing module determines the type and magnitude of the pressure according to the change directions and magnitudes of the four partial pressures, wherein the types of pressure are shear force and normal force.

[0011] Furthermore, the method for determining the pressure category to which the flexible micro-dome housing 1 is subjected is as follows:

[0012] It is determined whether the changing directions of the four partial pressures are the same. If so, the pressure on the flexible micro-dome shell 1 is a normal force; if not, the pressure on the flexible micro-dome shell 1 is a shear force. The changing direction includes increasing and decreasing.

[0013] Furthermore, the method for determining the pressure applied to the flexible micro-dome housing 1 is as follows:

[0014] The four divided voltages corresponding to the four sector electrodes are recorded as VIO0, VIO1, VIO2, and VIO3 in clockwise direction;

[0015] Determine whether the changing directions of the four partial pressures are the same. If so, the pressure on the flexible micro-dome housing 1 is a normal force, and the sum of VIO0, VIO1, VIO2, and VIO3 is used as the magnitude of the normal force on the flexible micro-dome housing 1. The changing direction includes increasing and decreasing.

[0016] If not, the pressure on the flexible micro-dome shell 1 is a shear force, VIO0 and VIO2 are used as the X components of the shear force vector, VIO1-VIO3 are used as the Y components of the shear force vector, and at the same time, the magnitude of the resultant vector of the X component and the Y component in the rectangular coordinate system is used as the magnitude of the shear force on the flexible micro-dome shell 1, and the direction of the resultant vector is used as the direction of the shear force on the flexible micro-dome shell 1.

[0017] Furthermore, the material of the upper encapsulation layer 3 and the lower encapsulation layer 7 is polyimide PI.

[0018] Furthermore, the material of the upper electrode layer 4 and the lower electrode layer 6 is conductive silver paste.

[0019] Furthermore, the radius of the full circle formed by the upper electrode layer 4 is smaller than the radius of the circular electrode of the lower electrode layer 6 .

[0020] Furthermore, the preparation method of the force conduction structure is:

[0021] 1) Two PLA plastic molds were printed using a melt extrusion 3D printer. One mold had a hemispherical groove with a radius of 3 mm, and the other mold had a cylindrical protrusion with four triangular support structures.

[0022] 2) Weigh and mix the PDMS matrix and crosslinker in a ratio of 10:1 on an electronic scale. Stir with a glass rod until thoroughly mixed. Pour the PDMS mixture into a PLA plastic mold and defoam twice in a vacuum defoaming chamber. Then, heat the PLA plastic mold on a hot plate at 85°C for 2 hours.

[0023] 3) Peel off the PLA plastic mold on the raised side of the cured PDMS. At this point, the flat side of the PDMS will have a recess reserved for the rigid lining structure. Epoxy resin components A and B are weighed and mixed in a 1:1 ratio on an electronic scale. Stir with a glass rod until thoroughly mixed. Pour the epoxy resin mixture into the recess of the PDMS. Degas the mixture twice in a vacuum defoaming chamber. Leave the PDMS at room temperature for 24 hours.

[0024] 4) Peel off the cured epoxy resin and PDMS on the other side of the mold, and remove the excess part with a blade, leaving the hemispherical dome and the flat side to obtain a force conduction structure with a rigid lining.

[0025] Furthermore, the preparation method of the four-component force sensor assembly is:

[0026] 1) After wiping both sides of the varistor clean with anhydrous ethanol, use two pieces of 240-grit sandpaper as a template, clamp them on both sides of the varistor, and use a hot press at 50°C for 90 seconds;

[0027] 2) After hot pressing, use a laser marking machine to cut the varistor sheet into discs with a radius of 4 mm;

[0028] 3) Using a slurry printer, print the upper electrode, lower electrode, and their leads with silver paste on the adhesive side of a 100-μm-thick single-sided PI tape. The upper electrode is in the shape of four separate sectors, and the lower electrode is a single circular piece.

[0029] 4) After printing, place the PI tape on a hot plate at 105°C for 5 minutes;

[0030] 5) After the silver paste material is cured, place the PI tape with the upper electrode layer facing up into a plasma processor and perform plasma treatment for 5 minutes to make the surface hydrophilic.

[0031] 6) The two prepared PI tapes with upper and lower electrodes are stacked and assembled with the piezoresistive sheet to obtain a four-component force sensor assembly.

[0032] Furthermore, the assembly method of the four-component force sensor assembly and the force transmission structure is as follows:

[0033] 1) Weigh and mix the PDMS substrate and crosslinker in a ratio of 10:1 on an electronic scale. Stir the mixture with a glass rod until thoroughly mixed. Defoam the mixture twice in a vacuum defoaming chamber to remove excess air from the PDMS before use.

[0034] 2) Applying the mixed, stirred, and defoamed PDMS to the upper side of the upper packaging layer of the four-component force sensor assembly, aligning the prepared force transmission structure with a rigid liner and adhering it to the upper side of the upper packaging layer of the four-component force sensor assembly, wherein the four branches of the rigid liner structure are aligned one by one with the four separate sector-shaped electrodes of the upper electrode layer;

[0035] 3) After alignment and adhesion, the bonded device was placed on a 45°C hot plate for 12 hours to complete the assembly of the four-component force sensor assembly and the force transmission structure.

[0036] Furthermore, the acquisition module packages the four collected partial pressures and sends them to the VR terminal where the processing module is located through serial communication. The processing module determines the type and magnitude of the pressure, and then controls the cursor in the VR virtual reality to move in the direction of the shear force, ultimately realizing cursor clicks and simulated key input in the VR virtual reality.

[0037] Beneficial effects:

[0038] 1. The present invention provides a sensor for transmitting finger operations in VR devices, which is composed of a four-component force sensor with four mutually separated and non-crosstalking piezoresistors and a force conduction structure with a rigid lining; the inner and outer layers of the structure are tightly fitted, with the outer layer being a soft hemispherical shell and the middle layer being a hard structure similar to a four-corner support frame; the force conduction structure is tightly connected to the packaging layer above the four-component force sensor through an adhesive layer; a set of equipment for sensor signal acquisition and transmission can realize remote data transmission through the equipped Bluetooth signal transmission module; therefore, compared with traditional flexible shear force sensors, the sensor of the present invention can achieve higher-dimensional shear force perception, not only sensing the magnitude of the shear force, but also having the ability to identify the direction of the shear force at all angles.

[0039] 2. The present invention provides a sensor for transmitting finger operations in VR devices. Multiple piezoresistive sensor modules are formed in a small area through a circuit connection method of a complete lower electrode and multiple fan-shaped upper electrodes. Each piezoresistive resistor is then connected in series with a resistor of a fixed resistance. By collecting the divided voltage on the fixed resistor, the resistance value of each piezoresistive resistor is obtained simultaneously, and then the components of the shear force relative to each direction are obtained, thereby realizing accurate judgment of the direction and magnitude of the shear force.

[0040] 3. The present invention provides a sensor for transmitting finger operations in VR devices. By introducing a hard rigid lining into the force conduction structure, the efficiency of shear force conduction is greatly improved. When the same shear force is applied, a greater positive pressure can be generated on the lower surface of the structure. After being bonded to the four-component force sensor device through an adhesive layer, the sensitivity of shear force recognition is greatly improved, so that the invention can not only identify the direction of shear force in all directions, but also detect the magnitude of shear force.

[0041] 4. The present invention provides a sensor for transmitting finger operations in VR devices. By attaching multiple small flexible omnidirectional force recognition sensors to the fingers, the user can perform VR interaction by replacing the traditional operating handles. Only a slight movement of the finger is required to complete a series of operations. In addition, the sensor is small, flexible and lightweight, and will not put too much burden on the user's hands. It will not cause fatigue after long-term use, and can provide a more immersive experience during VR interaction. In other words, the present invention can transmit data to the VR terminal through the single-chip microcomputer to realize operations such as cursor movement, clicking, and key simulation within the application.

[0042] 5. This invention provides a sensor for transmitting finger operations in VR devices. The flexible omnidirectional force sensor uses flexible materials for its packaging layer (PI), outer layer (PDMS) for its force-conducting structure, and pressure-sensitive layer. These materials are all biocompatible and can be worn on the human body for extended periods. Compared to traditional rigid omnidirectional force sensors, this invention offers advantages such as lower cost, clearer structure, and simpler fabrication. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the split structure of the flexible omnidirectional force recognition sensor of the present invention;

[0044] Figure 2 Schematic diagram of the connection between the flexible omnidirectional force recognition sensor and the single-chip microcomputer of the present invention;

[0045] Figure 3 This is a graph showing the current change after the piezoresistive sheet of the flexible omnidirectional force recognition sensor of the present invention is subjected to 14,000 cycles of compression and recovery under a normal force of 41 kPa after introducing a microstructure;

[0046] Among them, 1-PDMS flexible micro-dome shell, 2-rigid inner lining epoxy resin structure, 3-polyimide PI upper packaging layer, 4-silver paste upper electrode layer, 5-varistor sheet, 6-silver paste lower electrode layer, 7-polyimide PI lower packaging layer, 8-P-103 potentiometer, 9-equivalent resistance of four varistors, 10-STM32 microcontroller. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0048] like Figure 1 As shown, a sensor for transmitting finger operations in VR devices includes a force transmission structure, a four-component force sensor component, a voltage divider resistor component, an acquisition module, and a processing module;

[0049] The four-component force sensor assembly comprises, from top to bottom, an upper packaging layer (3), an upper electrode layer (4), a piezoresistive layer (5), a lower electrode layer (6) and a lower packaging layer (7); wherein the upper electrode layer (4) is composed of four separate sector-shaped electrodes that can be combined into a full circle, and the lower electrode layer (6) is a complete circular electrode, thereby dividing the piezoresistive layer (5) located between the upper electrode layer (4) and the lower electrode layer (6) into four mutually non-interfering piezoresistors for individually responding to the normal pressure and tangential pressure applied to each upper sector-shaped electrode; it should be noted that the force conduction structure and the four-component force sensor device are stacked on the upper packaging layer 3 through an adhesive layer to form the flexible omnidirectional force recognition sensor of the present invention, and each part of the entire device cannot produce dislocation, but because each part is made of flexible material and the overall thickness of the device is very thin, the sensor still has good bending ability.

[0050] The voltage divider resistor assembly comprises four fixed resistors with the same resistance value, and one end of each fixed resistor is connected in series with a sector electrode, and the other end is connected to a common ground terminal;

[0051] The force transmission structure is composed of a flexible micro-dome shell (1) and a rigid lining structure (2); wherein the rigid lining structure (2) has four branches distributed in a cross shape, and each branch is bonded to the upper packaging layer (3), and at the same time, the projection of each branch on the upper packaging layer (3) corresponds one-to-one with the projection of each sector electrode on the upper packaging layer (3); the rigid lining structure (2) is used to transmit the pressure exerted on the flexible micro-dome shell (1) to each piezoresistor; wherein the radius of the full circle formed by the upper electrode layer (4) is slightly smaller than the radius of the circular electrode of the lower electrode layer (6), and each electrode is provided with a lead to lead out the electrode.

[0052] When measuring the pressure exerted on the flexible micro-dome housing (1), a constant voltage is applied to the lower electrode layer (6), and the divided voltage of the four fixed resistors is measured through the acquisition module, wherein the pressure components exerted on each piezoresistor are different, and the divided voltage of the corresponding fixed resistor is different; that is, by measuring the divided voltage of the fixed resistors, the resistance change of the piezoresistor in the corresponding area can be obtained.

[0053] The processing module determines the type and magnitude of the pressure according to the change directions and magnitudes of the four partial pressures, wherein the types of pressure are shear force and normal force.

[0054] It should be noted that the force conduction structure is a "quadruple frame" structure similar to a camera tripod. When the upper end of the structure is subjected to a lateral shear force, the bottom area consistent with the direction of the shear force will be subjected to a greater positive pressure to maintain the stability of the overall structure. Therefore, the role of this structure is to convert the shear force exerted on the device into the positive pressure exerted on each area of ​​the four-component force device. The introduction of the rigid lining structure 2 greatly improves the accuracy and efficiency of shear force conduction. Here we discuss the device under the action of a certain normal pressure. When the device is subjected to a shear force in a certain direction, the positive pressure exerted on the area corresponding to the direction will increase, and the two sides will hardly bear the additional positive pressure brought by the shear force, while the positive pressure exerted in the opposite direction will decrease. This is the role of the force conduction structure.

[0055] Based on this, the method for determining the pressure category to which the flexible micro-dome housing (1) is subjected is as follows:

[0056] It is determined whether the directions of change of the four partial pressures are the same. If so, the pressure on the flexible micro-dome shell (1) is a normal force; if not, the pressure on the flexible micro-dome shell (1) is a shear force, wherein the direction of change includes increase and decrease.

[0057] The method for determining the pressure magnitude of the flexible micro-dome housing (1) is as follows:

[0058] The four partial voltages corresponding to the four sector electrodes are recorded as VIO0, VIO1, VIO2, and VIO3 in a clockwise direction; it is determined whether the change directions of the four partial voltages are the same. If yes, the pressure on the flexible micro-dome shell (1) is a normal force, and the sum of VIO0, VIO1, VIO2, and VIO3 is used as the magnitude of the normal force on the flexible micro-dome shell (1); wherein the change direction includes increase and decrease; if no, the pressure on the flexible micro-dome shell (1) is a shear force, and VIO0 and VIO2 are used as the X components of the shear force vector, and VIO1-VIO3 are used as the Y components of the shear force vector. At the same time, the magnitude of the resultant vector of the X component and the Y component in the rectangular coordinate system is used as the magnitude of the shear force on the flexible micro-dome shell (1), and the direction of the resultant vector is used as the direction of the shear force on the flexible micro-dome shell (1).

[0059] That is to say, the four-component force sensor device has independent pressure sensing capabilities in the four fan-shaped areas. When the flexible micro-dome shell is subjected to normal pressure, the signals of the four-component force sensor assembly will change in the same direction. When the flexible micro-dome shell is subjected to shear force, the signal change directions of the four-component force sensor assembly will be inconsistent. In this way, the sum of the four channel signal changes (ΔVIO0~3) is used as the device's response to normal force, and the difference between the four channel signal changes (ΔVIO0-ΔVIO2, ΔVIO1-ΔVIO3) is used as the device's response to shear force, thereby achieving simultaneous and accurate measurement of normal force and shear force.

[0060] Further, refer to Figure 2 , the four fan-shaped electrodes of the sensor are connected in series as sensing units 9 and fixed resistors 8, and then the STM32 microcontroller 10 is used as an acquisition module to collect the voltage signal divided on the four fixed resistors, and then the voltage signal is transmitted to the PC terminal or VR terminal. Figure 1 As shown, the four sector-shaped sensing units of the upper electrode 4 are distributed in a cross pattern, so the signals of the four sensing units are sequentially represented as VIO0, VIO1, VIO2, and VIO3 in a clockwise direction. As mentioned above, when the device is subjected to a normal force, VIO0~3 change in the same direction, and increase or decrease at the same time when the normal force changes. Therefore, the sum of VIO0~3 can represent the normal force applied to the device. When the device is subjected to a shear force, the signal changes in different directions of each unit. VIO0 and VIO2 change in opposite directions, and VIO1 and VIO3 change in opposite directions. Therefore, VIO0-VIO2 is used as the X component of the shear force vector, and VIO1-VIO3 is used as the Y component of the shear force vector. Then, the shear force applied to the device is the resultant vector of the above X and Y components in the rectangular coordinate system. The magnitude of this vector represents the magnitude of the shear force, and its direction is the direction of the shear force applied to the device. The synthesis and decomposition of the vectors is the coordinate conversion process from the plane rectangular coordinate system (x, y) to the plane polar coordinate system (ρ, θ).

[0061] It should be noted that the calculation process of the magnitude and direction of the normal force and shear force can be implemented through a C language program on a PC or VR terminal. The calculated finger operation data is then used to control the machine. Currently, functions such as cursor movement, clicking, and simulated key input on the PC can be realized, and it has good compatibility with VR applications that can run on the PC. Because the mechanical information that this device can obtain is not just a single normal force, but multi-dimensional mechanical information of normal force, shear force direction, and shear force magnitude, it can also realize more and more complex functions. At the same time, when combined with multiple sensing units, it can basically cover most functions that traditional operating handles can perform.

[0062] In a preferred embodiment, the flexible micro-dome shell 1 is a hemisphere with a radius of 3 mm, with a space in the middle reserved for a rigid lining structure. Meanwhile, the outer shell of the force-conducting structure is made of PDMS with a matrix to cross-linking agent ratio of 10:1; the rigid lining of the force-conducting structure is made of epoxy resin with a ratio of components A to B of 1:1.

[0063] In a preferred embodiment, the rigid lining structure 2 is a cylinder with four triangular support structures. Preferably, the cylinder has a radius of 0.6 mm and a height of 2.6 mm. The base of the triangular support is 2 mm long, 2 mm high, and 0.8 mm wide.

[0064] In a preferred embodiment, the thickness of the upper and lower packaging layers is 100 microns; the material of the upper packaging layer (3) and the lower packaging layer (7) is polyimide PI.

[0065] In a preferred embodiment, the thickness of the upper and lower electrodes is about 50-100 microns; the material of the upper electrode layer (4) and the lower electrode layer (6) is conductive silver paste.

[0066] In a preferred embodiment, the upper electrode is in the form of four separate sectors, each sector being separated from the middle by a cross having a width of 1 mm by a circle having a radius of 3 mm. Figure 1 As shown, each of the four areas is provided with a lead wire to lead them out, and the width of the lead wire is 0.5 mm;

[0067] In a preferred embodiment, the lower electrode is a circular piece with a radius of 3.5 mm, and is also provided with a 0.5 mm lead wire leading out thereof;

[0068] In a preferred embodiment, the thickness of the varistor sheet is 100 microns, and the surface is not completely flat, but has a certain sandpaper-like microstructure. At the same time, the varistor material is selected to have relatively stable piezoresistive properties, and the microstructure is modified by hot pressing to improve its sensitivity.

[0069] In a preferred embodiment, the fixed resistor is a P-103 potentiometer with an adjustable resistance of 10K; and the signal collection and transmission are performed using an STM32 single-chip microcomputer.

[0070] Figure 3 The current change of the varistor after the introduction of the microstructure was demonstrated after 14,000 cycles of compression and release under a normal pressure of 41 kPa, indicating that the stability of the varistor after the introduction of the microstructure is still good.

[0071] The following describes the preparation process of the flexible omnidirectional force recognition sensor of the present invention.

[0072] The sensor preparation in the embodiment is divided into three parts. The first is the preparation process of the force transmission structure with a rigid lining:

[0073] 1) Two PLA plastic molds were printed using a melt extrusion 3D printer. One mold had a hemispherical groove with a radius of 3 mm, and the other mold had a cylindrical protrusion with four triangular support structures. The parameters of the protrusion were consistent with the shape and parameters of the rigid lining structure 2 in the preferred embodiment above, and will not be repeated here.

[0074] 2) Weigh and mix the PDMS matrix and crosslinker in a 10:1 ratio on an electronic scale. Stir with a glass rod until thoroughly mixed. Pour the PDMS into the mold and defoam the mixture twice in a vacuum defoaming chamber to remove excess air. Then, heat the mold on a hot plate at 85°C for 2 hours.

[0075] 3) Peel off the raised side of the cured PDMS mold. The flat side of the PDMS will now have a recessed area reserved for the rigid lining structure. Epoxy resin components A and B are weighed and mixed in a 1:1 ratio on an electronic scale. Stir with a glass rod until thoroughly mixed. Pour the epoxy resin into the recessed area of ​​the PDMS. Degas the epoxy resin twice in a vacuum defoaming chamber to remove excess air. Leave the PDMS at room temperature for 24 hours.

[0076] 4) Peel off the cured epoxy resin and PDMS on the other side of the mold, and carefully remove the excess with a blade, leaving the hemispherical dome and a clean, flat side, to obtain the force-conducting structure with a rigid liner in the embodiment for future use;

[0077] Then comes the preparation process of the four-component force sensor device:

[0078] 1) After wiping both sides of the purchased varistor clean with anhydrous ethanol, use two pieces of 240-grit sandpaper as a template, clamp them on both sides of the varistor, and use a hot press at 50°C for 90 seconds;

[0079] 2) After hot pressing, use a laser marking machine at low power output to cut the varistor sheet into discs with a radius of 4 mm;

[0080] 3) Using a high-viscosity paste printer, silver paste was used to print the upper and lower electrodes and their leads on the adhesive side of a single-sided PI tape with a thickness of 100 microns. The upper electrode was in the shape of four separate sectors, and the lower electrode was in the shape of a single circular piece. The specific dimensions of the upper and lower electrodes and the leads were consistent with the parameters of the upper electrode layer 4 and the lower electrode layer 6 in the above-mentioned preferred embodiment, and are not further described here.

[0081] 4) After printing, place the PI tape on a hot plate at 105°C for 5 minutes;

[0082] 5) After the silver paste solidifies, place the PI tape with the top electrode layer facing up into a plasma processor and perform plasma treatment for 5 minutes to make the surface hydrophilic.

[0083] 6) Stack and assemble the two prepared PI tapes with upper and lower electrodes and the varistor disc. Note that the sides of the PI tape with the upper and lower electrodes are facing each other, and the varistor disc is sandwiched in the middle. Since the electrodes are printed on the side with the tape, no additional fixing means is required;

[0084] Then comes the assembly of the four-component force sensor device and the force transmission structure with a rigid lining:

[0085] 1) Weigh and mix the PDMS substrate and crosslinker in a ratio of 10:1 on an electronic scale. Stir with a glass rod until thoroughly mixed. Defoam the PDMS twice in a vacuum defoaming chamber to remove excess air before use.

[0086] 2) Apply an appropriate amount of mixed, stirred, and defoamed PDMS to the upper packaging layer of the four-component force sensor device, i.e., the plasma-treated side of the PI tape with the upper electrode. Then, align the prepared force transmission structure with the rigid liner and adhere it to the upper packaging layer of the four-component force sensor device. The four triangular support structures of the rigid liner need to be aligned one by one with the four separated sector-shaped areas of the upper electrode layer to achieve optimal shear force sensing.

[0087] 3) After alignment and adhesion, the device was placed on a 45° C. hot plate and allowed to stand for 12 hours, thereby completing the preparation of the flexible omnidirectional force recognition sensor in the embodiment.

[0088] Finally, the connection between the sensor and the microcontroller and the data processing on the VR device side:

[0089] 1) Lead out the lower electrode 6 of the prepared flexible omnidirectional force recognition sensor and connect it to the common source terminal of the microcontroller, such as Figure 2 As shown in the lower left part;

[0090] 2) The four electrodes of the upper electrode 4 of the flexible omnidirectional force recognition sensor are led out separately and connected in series with the potentiometers respectively. The other end of the potentiometer is connected to the common ground terminal of the microcontroller, such as Figure 2 As shown in the upper left part;

[0091] 3) Connect the four IO ports of STM32 to the non-ground terminal of the potentiometer, such as Figure 2 As shown in the middle left and right parts;

[0092] 4) The four port voltage signals collected by the STM32 are packaged and sent to the VR terminal through serial communication through single-chip microcomputer programming, and the serial port information is read and processed using C language to realize operations such as cursor movement, clicking, and simulated key input in VR virtual reality;

[0093] It should be noted that the choice of single-chip microcontroller is not limited to the STM32; various other chips and circuits with multi-channel voltage acquisition capabilities can also be used. Therefore, there are many alternative solutions for data transmission between the sensor and the machine terminal. At the same time, while the present invention demonstrates the sensor's ability to control VR devices, in reality, any application, program, or interactive method that supports running on a PC terminal can be implemented through this sensor system. Therefore, there are also many alternative solutions for how the sensor can control the machine terminal.

[0094] To sum up, an embodiment of the present invention proposes a flexible omnidirectional force recognition sensor for transmitting finger operations in VR devices. The flexible omnidirectional force recognition sensor can fit well on the user's fingers, accurately sense the finger sliding direction and force information, thereby realizing a series of operations of the user in the VR device; compared with the operation method of traditional operating handles or smart gloves, since the sensor is small and light, the human hand will not be burdened too much in this operation mode, and will not feel tired even after long-term use, and it has a more immersive interactive experience, providing new ideas for the next generation of VR device operation and interaction modes.

[0095] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may of course make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A sensor for transmitting finger operations in VR equipment, characterized in that: It includes a force transmission structure, a four-component force sensor assembly, a voltage divider resistor assembly, an acquisition module, and a processing module; The four-component force sensor assembly comprises, from top to bottom, an upper packaging layer (3), an upper electrode layer (4), a piezoresistive layer (5), a lower electrode layer (6), and a lower packaging layer (7); wherein the upper electrode layer (4) is composed of four separate sector-shaped electrodes that can be combined into a full circle, and the lower electrode layer (6) is a complete circular electrode, thereby dividing the piezoresistive layer (5) located between the upper electrode layer (4) and the lower electrode layer (6) into four piezoresistors; The voltage divider resistor assembly comprises four fixed resistors with the same resistance value, and one end of each fixed resistor is connected in series with a sector electrode, and the other end is connected to a common ground terminal; The force transmission structure is composed of a flexible micro-dome shell (1) and a rigid lining structure (2); wherein the rigid lining structure (2) has four branches distributed in a cross shape, and each branch is bonded to the upper packaging layer (3), and at the same time, the projection of each branch on the upper packaging layer (3) corresponds one-to-one to the projection of each sector electrode on the upper packaging layer (3); the rigid lining structure (2) is used to transmit the pressure exerted on the flexible micro-dome shell (1) to each piezoresistor; When measuring the pressure on the flexible micro-dome housing (1), a constant voltage is applied to the lower electrode layer (6), and the divided voltage of the four fixed resistors is measured through the acquisition module, wherein the pressure components borne by each piezoresistor are different, and the divided voltage of the corresponding fixed resistor is different; The processing module determines the type and magnitude of the pressure according to the change directions and magnitudes of the four partial pressures, wherein the types of pressure are shear force and normal force.

2. A sensor for transmitting finger operations in a VR device according to claim 1, characterized in that: The method for determining the pressure category to which the flexible micro-dome housing (1) is subjected is as follows: It is determined whether the directions of change of the four partial pressures are the same. If so, the pressure on the flexible micro-dome shell (1) is a normal force; if not, the pressure on the flexible micro-dome shell (1) is a shear force, wherein the direction of change includes increase and decrease.

3. A sensor for transmitting finger operations in a VR device according to claim 1, characterized in that: The method for determining the pressure magnitude of the flexible micro-dome housing (1) is as follows: The four divided voltages corresponding to the four sector electrodes are recorded as VIO0, VIO1, VIO2, and VIO3 in clockwise direction; Determine whether the directions of change of the four partial pressures are the same; if so, the pressure on the flexible micro-dome shell (1) is a normal force, and the sum of VIO0, VIO1, VIO2, and VIO3 is used as the magnitude of the normal force on the flexible micro-dome shell (1); wherein the direction of change includes increase and decrease; If not, the pressure on the flexible micro-dome shell (1) is a shear force, VIO0 and VIO2 are used as the X components of the shear force vector, VIO1-VIO3 are used as the Y components of the shear force vector, and at the same time, the magnitude of the resultant vector of the X component and the Y component in the rectangular coordinate system is used as the magnitude of the shear force on the flexible micro-dome shell (1), and the direction of the resultant vector is used as the direction of the shear force on the flexible micro-dome shell (1).

4. A sensor for transmitting finger operations in a VR device according to claim 1, characterized in that: The materials of the upper packaging layer (3) and the lower packaging layer (7) are polyimide PI.

5. The sensor for transmitting finger operation in VR equipment according to claim 1, characterized in that: The materials of the upper electrode layer (4) and the lower electrode layer (6) are conductive silver paste.

6. A sensor for transmitting finger operations in a VR device according to claim 1, characterized in that: The radius of the full circle formed by the upper electrode layer (4) is smaller than the radius of the circular electrode of the lower electrode layer (6).

7. A sensor for transmitting finger operations in a VR device according to claim 1, characterized in that: The preparation method of the force transmission structure is as follows: 1) Two PLA plastic molds were printed using a melt extrusion 3D printer. One mold had a hemispherical groove with a radius of 3 mm, and the other mold had a cylindrical protrusion with four triangular support structures. 2) Weigh and mix the PDMS matrix and crosslinker in a ratio of 10:1 on an electronic scale. Stir with a glass rod until thoroughly mixed. Pour the PDMS mixture into a PLA plastic mold and defoam twice in a vacuum defoaming chamber. Then, heat the PLA plastic mold on a hot plate at 85°C for 2 hours. 3) Peel off the PLA plastic mold on the raised side of the cured PDMS. At this point, the flat side of the PDMS will have a recess reserved for the rigid lining structure. Epoxy resin components A and B are weighed and mixed in a 1:1 ratio on an electronic scale. Stir with a glass rod until thoroughly mixed. Pour the epoxy resin mixture into the recess of the PDMS. Degas the mixture twice in a vacuum defoaming chamber. Leave the PDMS at room temperature for 24 hours. 4) Peel off the cured epoxy resin and PDMS on the other side of the mold, and remove the excess part with a blade, leaving the hemispherical dome and the flat side to obtain a force conduction structure with a rigid lining.

8. The sensor for transmitting finger operations in a VR device according to claim 1, wherein: The preparation method of the four-component force sensor assembly is as follows: 1) After wiping both sides of the varistor clean with anhydrous ethanol, use two pieces of 240-grit sandpaper as a template, clamp them on both sides of the varistor, and use a hot press at 50°C for 90 seconds; 2) After hot pressing, use a laser marking machine to cut the varistor sheet into discs with a radius of 4 mm; 3) Using a slurry printer, print the upper electrode, lower electrode, and their leads with silver paste on the adhesive side of a 100-μm-thick single-sided PI tape. The upper electrode is in the shape of four separate sectors, and the lower electrode is a single circular piece. 4) After printing, place the PI tape on a hot plate at 105°C for 5 minutes; 5) After the silver paste material is cured, place the PI tape with the upper electrode layer facing up into a plasma processor and perform plasma treatment for 5 minutes to make the surface hydrophilic. 6) The two prepared PI tapes with upper and lower electrodes are stacked and assembled with the piezoresistive sheet to obtain a four-component force sensor assembly.

9. The sensor for transmitting finger operations in a VR device according to claim 1, wherein: The assembly method of the four-component force sensor assembly and the force transmission structure is as follows: 1) Weigh and mix the PDMS substrate and crosslinker in a ratio of 10:1 on an electronic scale. Stir the mixture with a glass rod until thoroughly mixed. Defoam the mixture twice in a vacuum defoaming chamber to remove excess air from the PDMS before use. 2) Applying the mixed, stirred, and defoamed PDMS to the upper side of the upper packaging layer of the four-component force sensor assembly, aligning the prepared force transmission structure with a rigid liner and adhering it to the upper side of the upper packaging layer of the four-component force sensor assembly, wherein the four branches of the rigid liner structure are aligned one by one with the four separate sector-shaped electrodes of the upper electrode layer; 3) After alignment and adhesion, the bonded device was placed on a 45°C hot plate for 12 hours to complete the assembly of the four-component force sensor assembly and the force transmission structure.

10. The sensor for transmitting finger operation in VR equipment according to claim 1, characterized in that: The acquisition module packages the four collected partial pressures and sends them to the VR terminal where the processing module is located through serial communication. The processing module determines the type and magnitude of the pressure, and then controls the cursor in the VR virtual reality to move in the direction of the shear force, ultimately realizing cursor clicks and simulated key input in the VR virtual reality.

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