Automobile intelligent cockpit steering wheel hand-off detection device using flexible force sensor

Abstract

The present invention specifically relates to an intelligent car cockpit steering wheel hand-off detection device using a flexible force sensor, which solves the problems of misjudgment, limited detection, and high cost of detection equipment in existing car steering wheel hand-off detection technology. An intelligent car cockpit steering wheel hand-off detection device using a flexible force sensor, the pressure detection part includes a flexible capacitive pressure sensor; the flexible capacitive pressure sensor includes two flexible plates and a flexible dielectric elastomer; the flexible dielectric elastomer is made of a composite material mixed with PDMS and gallium indium tin liquid metal, and blocking particles are arranged inside the composite material; the warning part includes an audible and visual alarm; the control part includes a capacitive data acquisition card and a 32-bit microcontroller. The present invention ensures that the liquid metal is highly dispersed in the flexible dielectric elastomer and the flexible conductive elastomer through blocking particles, and has the advantages of high dielectricity, high conductivity, high conformality, low percolation threshold, and low cost.

Description

Technical Field

[0001] The invention relates to a technology for detecting hands-off of a steering wheel in an intelligent automobile cockpit, and in particular to a device for detecting hands-off of a steering wheel in an intelligent automobile cockpit using a flexible force sensor. Background Art

[0002] With the improvement of automobile automation, the intelligent cockpit of the car has realized the combination of vehicle environmental perception, location perception, and user scenario needs to provide corresponding intelligent services. Among them, steering wheel hand-off detection is a key intelligent technology in the intelligent cockpit. During driving, the driver may take his hands off the steering wheel due to emergencies or habitual reasons. This is a very dangerous behavior whether driving at low or high speeds. Steering wheel hand-off detection, during driving, hand-off detection detects whether the driver's hands have left the steering wheel and issues a warning, which is crucial to ensuring driving safety.

[0003] Traditional detection technologies use steering column torque sensors, optical sensors, and steering wheel capacitive sensors to detect when the driver's hands are off the steering wheel. The torque sensor detects when the driver's hands are off the steering wheel by detecting the torque of the steering column, but it may misjudge small angles and continuous deflections. The optical sensor uses a camera installed on the steering wheel to determine in real time whether the driver's hands have left the steering wheel, but the camera assembly is complex, expensive, and has limited shooting angles. The steering wheel capacitive sensor is a sensor arranged under the skin of the steering wheel that can determine whether the driver's left or right hands have left the steering wheel, but it is expensive and has a detection blind spot. At the same time, the above three types of hand-off detection sensors are rigid sensors, and installing them on the steering wheel will affect the driver's comfort.

[0004] Research has shown that liquid metal elastomer is a flexible multifunctional material with good performance, but there is a problem of liquid metal sedimentation, which affects the material performance and increases the cost. Interestingly, pomegranate is a fruit of the Punica granatum plant, the fruit part of which is an obtuse-angled pomegranate berry in a compact granular form. This spatial layout makes the pomegranate seeds block each other, which has the advantage of good structural consistency. The pomegranate fruit structure has excellent stability, which provides a new idea for designing a liquid metal elastomer sensor with blocking particles.

[0005] Based on this, it is necessary to invent a car intelligent cockpit steering wheel hands-off detection device using a flexible force sensor. The device has the advantages of flexible attachment features, sensitive response characteristics and low cost. It can detect the driver's pressure changes on the steering wheel through flexible force sensing, and transmit the pressure data to a 32-bit microcontroller through a capacitive data acquisition card. The 32-bit microcontroller controls the sound and light alarm. When the transmission signal is that the driver's hands leave the steering wheel, the 32-bit microcontroller controls the sound and light alarm to turn on to remind the driver, which makes up for the shortcomings of traditional steering wheel hands-off detection sensor technology. Summary of the invention

[0006] In order to solve the problems of misjudgment, limited detection and high cost of detection equipment in existing automobile steering wheel hands-off detection technology, the present invention provides an automobile intelligent cockpit steering wheel hands-off detection device using a flexible force sensor.

[0007] The present invention is achieved by adopting the following technical solutions:

[0008] An automobile intelligent cockpit steering wheel hands-off detection device using a flexible force sensor, comprising a pressure detection part, a warning part and a control part;

[0009] The pressure detection part includes N flexible capacitive pressure sensors arranged between the upper surface of the foaming layer and the inner surface of the leather layer and distributed along the circumferential direction of the steering wheel, and N is a positive integer greater than or equal to 4; the flexible capacitive pressure sensor includes two flexible plates distributed in parallel up and down and a flexible dielectric elastomer arranged between the two flexible plates, the opposite surfaces of the two flexible plates are provided with metal coatings, and the upper surface and the lower surface of the flexible dielectric elastomer are fixedly attached to the two metal coatings respectively; the flexible dielectric elastomer is made of a composite material mixed with PDMS and gallium indium tin liquid metal, and a plurality of uniformly distributed blocking particles are arranged inside the composite material;

[0010] The warning part includes an audible and visual alarm arranged on the upper side of the middle part of the steering wheel;

[0011] The control part includes a capacitance data acquisition card and a 32-bit microcontroller. Each metal coating is electrically connected to the capacitance data acquisition card through a wire. The control end of the sound and light alarm and the capacitance data acquisition card are electrically connected to the 32-bit microcontroller.

[0012] PDMS is polydimethylsiloxane; the gallium indium tin liquid metal described in the present invention is a non-toxic liquid metal. In the present invention, an AD capacitance conversion circuit is provided in the capacitance data acquisition card, and each metal coating is electrically connected to the AD capacitance conversion circuit through a wire to convert the capacitance signal into a digital signal.

[0013] Furthermore, the warning part also includes a contactor, a flexible conductive elastomer arranged at the bottom of the sound and light alarm, and a flexible substrate adhered to the bottom of the flexible conductive elastomer and fixed to the upper side of the steering wheel; the contactor and the flexible conductive elastomer are both connected in series in the power supply circuit of the sound and light alarm, and the control end of the contactor is electrically connected to the 32-bit microcontroller; the flexible conductive elastomer is made of a composite material I mixed with PDMS and gallium indium tin liquid metal, and a plurality of evenly distributed blocking particles are arranged inside the composite material I.

[0014] The present invention can reduce the complexity of the structure at the installation location of the sound and light alarm by installing the sound and light alarm on a flexible conductive elastic body.

[0015] Furthermore, the steering wheel is in the shape of a clock dial, and the number of the flexible capacitive pressure sensors is 4 to 8; two of the flexible capacitive pressure sensors are respectively located between nine o'clock and ten o'clock and between three o'clock and four o'clock on the clock dial; the remaining flexible capacitive pressure sensors are distributed in the empty positions of the clock dial.

[0016] The position between nine o'clock and ten o'clock is the correct holding position of the driver's left hand, and the position between three o'clock and four o'clock is the correct holding position of the driver's right hand, and when held correctly, this posture is conducive to supporting the body. In the present invention, N flexible capacitive pressure sensors are arranged in a circular array, which can fully cover the holding position of the driver's hand, thereby increasing the detection accuracy.

[0017] Furthermore, the droplet particle size of the gallium indium tin liquid metal in the composite material and the droplet particle size of the gallium indium tin liquid metal in the composite material I are both 10μm to 50μm; the gallium indium tin liquid metal in the composite material and the gallium indium tin liquid metal in the composite material I are both composed of the following raw materials in percentage by mass: 68.5% gallium, 21.5% indium, and 10% tin; the blocking particles are PDMS particles obtained by crushing a solidified PDMS block, and have a particle size of 100μm to 225μm, presenting an irregular polyhedral structure.

[0018] The volume percentages of the components in the flexible dielectric elastomer are as follows: gallium indium tin liquid metal is greater than or equal to 10% and less than 40%, blocking particles are 20% to 30%, and the balance is PDMS;

[0019] The volume percentages of the various components in the flexible conductive elastomer are as follows: 40% to 60% of gallium, indium and tin liquid metal, 20% to 30% of blocking particles, and the remainder being PDMS.

[0020] Furthermore, the volume percentages of PDMS, gallium indium tin liquid metal, and blocking particles in the flexible dielectric elastomer and the volume percentages of PDMS, gallium indium tin liquid metal, and blocking particles in the flexible conductive elastomer are determined by a mixture design method based on a Scheffe trinomial model, and the Scheffe trinomial model is shown in formula (a):

[0021]

[0022] Where q = 3, y is the conductivity, each β represents the parameter to be estimated, ε represents the error, and E(ε) = 0, D(ε) = σ 2 , α represents the volume percentage of each of the q components in the mixture system, and the volume percentage of each component is in the normal simplex S q-1 The points are selected inside and must satisfy the following equation:

[0023]

[0024] The present invention studies the optimal conductive orthogonal block design for parameter estimation through a mixture design method based on the Scheffe polynomial model, wherein for a mixture system of q components, the Scheffe polynomial model is shown in formula (c):

[0025]

[0026] In the formula, y is the test index, each β represents the parameter to be estimated, α represents the proportion of various components in the mixture, that is, the percentage of each q component in the parameter mixture system, ε represents the error, and E(ε)=0, D(ε=σ2, each mixture variable is in the normal simplex S q-1 The points are selected inside and must satisfy the following equation:

[0027]

[0028] When the volume percentage of PDMS, gallium indium tin liquid metal, and blocking particles in the flexible dielectric elastomer and the volume percentage of PDMS, gallium indium tin liquid metal, and blocking particles in the flexible conductive elastomer are determined using the mixture design method based on the Scheffe trinomial model, the initial parameter setting range is: the volume percentage of gallium indium tin liquid metal is 10% to 70%; the volume percentage of PDMS is 20% to 90%; the volume percentage of blocking particles is 20% to 50%.

[0029] Furthermore, the control part also includes a host computer, which is electrically connected to the control end of the sound and light alarm and the 32-bit microcontroller respectively;

[0030] Furthermore, the sound and light alarm includes an LED lamp and an alarm; the flexible substrate is made of PDMS, platinum-cured rubber, Teflon or natural rubber; the flexible electrode is a rectangular electrode made of polyimide, and its length is 10mm~50mm, width is 5mm~20mm, and thickness is 100μm~200μm; the metal coating is a gold layer with a thickness of 100nm; the flexible dielectric elastomer is in the shape of a rectangular parallelepiped, and its length is 10mm~50mm, width is 5mm~20mm, and thickness is 1mm~5mm; the flexible conductive elastomer is in the shape of a long strip, and its width is 2mm~4mm, and thickness is 0.5mm~1mm.

[0031] Furthermore, the preparation of the flexible dielectric elastomer is achieved by the following steps:

[0032] Step S1: preparing blocking particles; the specific steps are as follows:

[0033] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0034] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush them at a speed of 3000 rpm for 3 minutes, pause for 2 minutes to 5 minutes, shear and crush them again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles;

[0035] Step S2: preparing a flexible dielectric elastomer; the specific steps are as follows:

[0036] Step S2.1: First, gallium indium tin liquid metal is mixed with a PDMS solution so that the volume percentage of the gallium indium tin liquid metal in the flexible dielectric elastomer is greater than or equal to 10% and less than 40%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 2 minutes to 4 minutes, and then stirring with a vacuum stirrer for 10 minutes to 15 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 10 μm to 50 μm, and a composite material is obtained;

[0037] Step S2.2: Add blocking particles to the composite material obtained in step S2.1 and mix them so that the volume percentage of the blocking particles in the flexible dielectric elastomer is 20% to 30%; stir manually with a glass rod for 2 minutes to 4 minutes, and then stir with a vacuum stirrer for 10 minutes to 15 minutes, and during stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material with blocking particles;

[0038] Step S2.3: Pour the composite material with blocking particles obtained in step S2.2 into a rectangular resin mold, evacuate the air, and put it into a forced air drying oven for curing at a temperature of 80° C. for 2 hours, thereby obtaining a flexible dielectric elastomer.

[0039] Furthermore, the preparation of the flexible conductive elastomer is achieved by the following steps:

[0040] Step S1: preparing blocking particles; the specific steps are as follows:

[0041] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0042] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush them at a speed of 3000 rpm for 3 minutes, pause for 2 minutes to 5 minutes, shear and crush them again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles;

[0043] Step S2: preparing a flexible conductive elastomer; the specific steps are as follows:

[0044] Step S2.1: firstly, gallium indium tin liquid metal is mixed with PDMS solution so that the volume percentage of gallium indium tin liquid metal in the flexible conductive elastomer is 40% to 60%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 2min to 4min, and then stirring with a vacuum stirrer for 10min to 15min, and during stirring, the stirring speed is first set to 900rpm, then adjusted to 2000rpm, and then adjusted to 1000rpm, so that the droplet size of the gallium indium tin liquid metal is 10μm to 50μm, to obtain a composite material I;

[0045] Step S2.2: Add blocking particles to the composite material I obtained in step S2.1 and mix them so that the volume percentage of the blocking particles in the flexible conductive elastomer is 20% to 30%; stir manually with a glass rod for 2 minutes to 4 minutes, and then use a vacuum stirrer for 10 minutes to 15 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material I with blocking particles;

[0046] Step S2.3: Scrape the composite material I with blocking particles obtained in step S2.2 onto a mold on a flexible substrate, evacuate the air, and place it in a forced air drying oven for curing at a temperature of 80°C for 2 hours, thereby obtaining a flexible conductive elastomer.

[0047] In step S2.3, the mold is placed on the upper surface of the flexible substrate, and a groove matching the shape of the flexible conductive elastomer is opened on the mold, so that the composite material I with blocking particles can pass through the groove and be fixedly bonded to the upper surface of the flexible substrate.

[0048] The specific working process of the present invention is as follows:

[0049] When the driver of the car holds the steering wheel and drives normally, the sound and light alarm in the present invention does not light up and does not alarm. The specific principle is: the flexible capacitive pressure sensor attached between the foaming layer and the leather layer of the handheld part is compressed, the distance between the two flexible plates is reduced, the flexible dielectric elastomer is compressed, the plate spacing of the flexible capacitive pressure sensor is reduced, and the dielectric constant increases (the specific reason is: the gallium indium tin liquid metal droplets are highly dispersed in the flexible dielectric elastomer, because the flexible dielectric elastomer is compressed, the gallium indium tin liquid metal droplets are changed from spherical to elliptical, and the distance between the droplets is reduced, which increases the electron transmission ability, so that the flexible dielectric elastomer is reduced by the dielectric loss factor), so that the capacitance of the flexible capacitive pressure sensor increases. In this process, the capacitance data is received in real time by the capacitance data acquisition card, and the acquisition result is transmitted to the 32-bit microcontroller, the 32-bit microcontroller determines that the data capacitance is higher than the set threshold, and sends a control signal to the control end of the sound and light alarm in real time, and the sound and light alarm does not light up and does not alarm.

[0050] When the driver of the car leaves the steering wheel with both hands, the sound and light alarm in the present invention lights up and alarms. The specific principle is: the shape of each flexible capacitive pressure sensor attached between the foaming layer and the leather layer is restored to the initial shape, the spacing of each pair of flexible plates returns to the initial distance, each flexible dielectric elastomer becomes the initial state, the plate spacing of each flexible capacitive pressure sensor is increased to the initial distance, and the dielectric constant is changed to the initial value, so that the capacitance of each flexible capacitive pressure sensor is reduced to the initial capacitance. In this process, the capacitance data is received in real time by the capacitance data acquisition card, and the collection result is input to the 32-bit microcontroller. When the capacitance value of each flexible capacitive pressure sensor is lower than the set threshold, it means that the driver's hand leaves the steering wheel. At this time, the 32-bit microcontroller sends a control signal to the control end of the sound and light alarm in real time, and the power supply circuit of the sound and light alarm is in a path state. There is current passing through the flexible conductive elastic body, and the sound and light alarm lights up and alarms, reminding the driver to drive safely.

[0051] Based on the above process, compared with the traditional detection technology of automobile hand-off detection, the automobile intelligent cockpit steering wheel hand-off detection device using a flexible force sensor described in the present invention has the following beneficial effects: First, the present invention no longer uses ordinary sensors and displays, but uses a flexible dielectric elastomer with blocking particles to prepare a flexible capacitive pressure sensor, and uses a flexible conductive elastomer with blocking particles to connect an acoustic and light alarm, wherein the flexible dielectric elastomer and the flexible conductive elastomer are not a traditional mixture of liquid metal and elastomer, but by imitating the blocking structure of pomegranate fruit, PDMS-made blocking particles are introduced into the flexible dielectric elastomer and the flexible conductive elastomer as a blocking structure to block the precipitation of liquid metal, thereby ensuring a high dispersion of liquid metal in the flexible dielectric elastomer and the flexible conductive elastomer, having the advantages of high dielectricity, high conductivity, high conformality, low percolation threshold, low cost, etc., and can be used to prepare the installation mechanism of flexible capacitive pressure sensors and acoustic and light alarms. Secondly, the present invention adopts a fully flexible design, which can be easily and conveniently attached to the complex surface of the steering wheel. When the driver's hands leave the steering wheel, it can timely feedback the hands-off operation and control the sound and light alarm to light up and alarm. Therefore, when the driver of the car leaves the steering wheel with both hands during driving, even if the time of leaving is very short, the present invention can timely and accurately detect the driver's dangerous operation, so as not to miss the best time for remediation, thereby effectively improving the safety factor in car driving, ensuring the safety of the driver and passengers, and realizing the intelligence of the car cockpit.

[0052] In order to verify the above beneficial effects, the following comparative tests were conducted:

[0053] Comparative experiment 1:

[0054] First, LME elastomer and LMEP elastomer with a volume percentage of 20% of gallium indium tin liquid metal (LM) were prepared; wherein the LMEP elastomer is a flexible dielectric elastomer with blocking particles described in the present invention, and the LME elastomer is a flexible dielectric elastomer without blocking particles inside (i.e., only PDMS and gallium indium tin liquid metal are contained inside), which serve as control samples in this comparative experiment;

[0055] Then a small piece was cut off with a knife, and the sample micromorphology was characterized by SEM, and the SEM images of LME elastomer and LMEP elastomer at 300X were obtained by scanning at 20kV voltage;

[0056] By the attached Figure 5 It can be seen that when the LM volume fraction is constant and the curing time is the same, the LM droplets in the LME elastomer settle and gather under the sample to form a dense layer. Figure 5 a; on the contrary, after the introduction of blocking particles, the LM droplets of LMEP elastomer are highly dispersed and no aggregation occurs, as shown in the attached Figure 5 As shown in b.

[0057] The conclusions are as follows: Compared with LME elastomers, LMEP elastomers imitate the blocking structure of pomegranate fruit, and the introduction of PDMS blocking particles solves the LM droplet sedimentation problem in LME elastomer samples. LMEP elastomer samples can improve the dielectric or conductive properties of LME elastomers at a lower LM volume percentage, reduce the percolation threshold of LME elastomers, and reduce the cost of composite materials.

[0058] Comparative experiment 2:

[0059] Since the steering wheel hand-off detection device used in the car's intelligent cockpit needs to have a high grip recognition ability, the pressure detection part needs to have good capacitance change ability, and the maximum continuous driving time is 4 hours, the flexible capacitive pressure sensor needs to have good repeatability and stability, so the following comparative experiment is carried out.

[0060] First, six kinds of flexible dielectrics were prepared, namely:

[0061] The first flexible dielectric was made of a single PDMS and was referred to as φ LM =0% LME;

[0062] The second flexible dielectric is made of 10% gallium indium tin liquid metal (hereinafter referred to as liquid metal) and 90% PDMS solution. LM =10% LME;

[0063] The third flexible dielectric is composed of 10% liquid metal by volume, 30% PDMS blocking particles by volume, and 60% PDMS solution by volume, which is referred to as φ LM =10% LMEP;

[0064] The fourth flexible dielectric is composed of 30% liquid metal and 70% PDMS solution, referred to as φ LM =30% LME;

[0065] The fifth flexible dielectric is composed of 30% liquid metal by volume, 30% PDMS blocking particles by volume, and 40% PDMS solution by volume, referred to as φ LM =30% LMEP;

[0066] The sixth flexible dielectric is composited by 20% by volume of liquid metal, 30% by volume of PDMS blocking particles and 50% by volume of PDMS solution.

[0067] Then, six kinds of flexible dielectrics were used to prepare six kinds of flexible capacitive sensors, and the flexible capacitive sensors made from the first five kinds of flexible dielectrics were subjected to continuous strains of 0 to 30%, and the following results were obtained: Figure 6 The strain-capacitance change rate curves are shown in the figure. The three flexible capacitive sensors (made from the third, fifth, and sixth flexible dielectrics, respectively) with a volume fraction of 30% PDMS blocking particles and the flexible capacitive sensor without PDMS blocking particles (made from the first flexible dielectric) were subjected to continuous stress of 0 to 300 kPa, and the results are shown in the figure below. Figure 7 The stress-capacitance change rate curve is shown in the figure. The flexible capacitive sensor prepared by the fifth flexible dielectric was tested for stability and cyclicity of the sensor, and the attached Figure 8 The time-capacitance change rate curve is shown.

[0068] By the attached Figure 6 It can be seen that the greater the liquid metal content, the greater the capacitance change rate; when the liquid metal content is the same, the composite material with PDMS blocking particles has a greater capacitance change rate, which is attributed to the presence of PDMS blocking particles, which makes the liquid metal in the flexible dielectric highly dispersed, increases the electron mobility, and changes the capacitance sensitively. This shows that the liquid metal dielectric elastomer with PDMS blocking particles has better dielectric properties than traditional liquid metal elastomers.

[0069] By the attached Figure 7It can be seen that when the volume fraction of PDMS particles is 30%, the greater the volume fraction of liquid metal, the greater the capacitance change rate of the flexible capacitive sensor. When the volume fraction of liquid metal is 30%, the capacitance change rate of the flexible capacitive sensor is as high as 1.08, which is 2.4 times that of the pure PDMS flexible capacitive sensor (the flexible capacitive sensor made of the first flexible dielectric).

[0070] By the attached Figure 8 It can be seen that the sensor has the advantages of good stability, good repeatability and long life after 1000 cycles under 30% strain.

[0071] Comparative experiment three:

[0072] First, seven flexible elastomers with sizes of 20 mm × 20 mm × 4 mm were prepared:

[0073] The first flexible elastomer was made of a composite material containing 10 vol% of gallium indium tin liquid metal, 70 vol% of PDMS solution, and 20 vol% of PDMS blocking particles;

[0074] The second flexible elastomer was made of a composite material containing 20 vol% of gallium indium tin liquid metal, 60 vol% of PDMS solution, and 20 vol% of PDMS blocking particles;

[0075] The third flexible elastomer was made of a composite material containing 30 vol% of gallium indium tin liquid metal, 50 vol% of PDMS solution, and 20 vol% of PDMS blocking particles;

[0076] The fourth flexible elastomer was made of a composite material containing 36.5 vol% of gallium indium tin liquid metal, 43.5 vol% of PDMS solution, and 20 vol% of PDMS blocking particles;

[0077] The fifth flexible elastomer is made of a composite material containing 40 vol% of gallium indium tin liquid metal, 40 vol% of PDMS solution and 20 vol% of PDMS blocking particles;

[0078] The sixth flexible elastomer is made of a composite material containing 50 vol% of gallium indium tin liquid metal, 30 vol% of PDMS solution and 20 vol% of PDMS blocking particles;

[0079] The seventh flexible elastomer is made of a composite material containing 60 vol% of gallium indium tin liquid metal, 20 vol% of PDMS solution and 20 vol% of PDMS blocking particles;

[0080] Then, the composite material, two pieces of copper tape, wire and Keithley ammeter of model 2450 were used to form a conductive loop, and the resistance of seven flexible elastomers was tested. Fig. 9 Liquid metal volume fraction-resistance change curve shown;

[0081] By the attached Fig. 9 It can be seen that when the volume fraction of PDMS blocking particles is 20% and the volume fraction of gallium indium tin liquid metal is less than 30%, the resistance of the composite material reaches 107Ω, which is a dielectric; when the volume fraction of gallium indium tin liquid metal is 36.5%, the sample resistance is 254Ω; when the volume fraction of gallium indium tin liquid metal is 40%, the sample resistance is 7.3401Ω; when the volume fraction of gallium indium tin liquid metal is 50%, the sample resistance is 0.29541Ω; when the volume fraction of gallium indium tin liquid metal is 60%, the sample resistance is 0.02301Ω;

[0082] The conclusions are as follows: the resistance of the liquid metal flexible elastomer with PDMS blocking particles increases with the increase of the gallium indium tin liquid metal content. When the volume fraction of the gallium indium tin liquid metal is greater than 36.5%, the flexible elastomer exhibits conductive properties and can be used as a flexible conductive elastomer connected to an audible and visual alarm in the steering wheel hands-off detection of the present invention to respond and warn the driver's erroneous operation of taking both hands off the steering wheel in an intuitive form.

[0083] Comparative experiment 4:

[0084] First, a composite material containing 40 vol% of gallium indium tin liquid metal, 30 vol% of PDMS solution and 30 vol% of PDMS blocking particles was prepared, and a flexible conductive elastomer was designed, such as the attached Fig.10 As shown,

[0085] Then, a flexible conductive elastomer is made on a PDMS substrate (corresponding to PDMS in the figure), a platinum cured rubber substrate (corresponding to Ecoflex in the figure), a Teflon tape (corresponding to Teflon tape in the figure), and a Teflon sheet (corresponding to Teflon sheet in the figure), and a power source is connected to obtain the following Fig.10 The flexible display circuit shown in the figure. Fig.10 In the figure, bending refers to the working state of the flexible conductive elastomer in a bending state; stretching refers to the working state of the flexible conductive elastomer in a stretching state.

[0086] The conclusions are as follows: when the volume fraction of gallium indium tin liquid metal is 40% and the volume fraction of PDMS blocking particles is 30%, the composite material has good electrical conductivity and is well connected to substrates of various materials, including Teflon material with poor adsorption properties, indicating that the present invention can be applied to automobile steering wheels of different materials.

[0087] The invention has a simple process and a reasonable design, solves the problems of misjudgment, limited detection, high cost of detection equipment, etc. of the traditional automobile steering wheel hands-off detection technology, and is suitable for automobile steering wheel hands-off detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 It is a schematic diagram of the structure of the present invention;

[0089] Figure 2 It is a schematic diagram of the arrangement of the flexible capacitive pressure sensor installation location in the present invention;

[0090] Figure 3 It is a structural schematic diagram of the flexible capacitive pressure sensor in the present invention;

[0091] Figure 4 is a schematic diagram of the internal structure of the flexible conductive elastomer in the present invention;

[0092] Figure 5 (a) Figure 5 (b) is a SEM image of the LME elastomer and the LMEP elastomer in the comparative experiment 1 of the present invention;

[0093] Figure 6 is the strain-capacitance change rate curve obtained in the second comparative experiment of the present invention;

[0094] Figure 7 is the stress-capacitance change rate curve obtained in the comparative experiment 2 of the present invention;

[0095] Figure 8 It is the time-capacitance change rate variation curve obtained in the comparative experiment 2 of the present invention;

[0096] Fig. 9 This is the GaInSn liquid metal volume fraction-resistance change curve obtained in the comparative experiment 3 of the present invention;

[0097] Fig.10 It is a comparison diagram of flexible display circuits on different substrates obtained in comparative experiment 4 of the present invention.

[0098] In the figure, 1- foaming layer, 2- leather layer, 3- steering wheel, 4- flexible capacitive pressure sensor, 5- flexible electrode, 6- metal coating, 7- blocking particles, 8- sound and light alarm, 9- wire, 10- flexible conductive elastomer, 11- flexible substrate, 12- PDMS, 13- gallium indium tin liquid metal droplet. DETAILED DESCRIPTION

[0099] Example 1

[0100] An automobile intelligent cockpit steering wheel hands-off detection device using a flexible force sensor, comprising a pressure detection part, a warning part and a control part;

[0101] As attached Figure 1 , Attachment Figure 2 As shown; the pressure detection part includes six flexible capacitive pressure sensors 4 arranged between the upper surface of the foam layer 1 and the inner surface of the leather layer 2 and distributed along the circumferential direction of the steering wheel 3; as shown in the attached Figure 3 As shown; the flexible capacitive pressure sensor 4 includes two flexible plates 5 arranged in parallel up and down and a flexible dielectric elastomer arranged between the two flexible plates 5, the opposite surfaces of the two flexible plates 5 are provided with metal coatings 6, and the upper surface and the lower surface of the flexible dielectric elastomer are fixedly attached to the two metal coatings 6 respectively; the flexible dielectric elastomer is made of a composite material mixed with PDMS and gallium indium tin liquid metal, and a plurality of uniformly distributed blocking particles 7 are arranged inside the composite material;

[0102] The warning part includes an audible and visual alarm 8 arranged on the upper side of the middle part of the steering wheel 3;

[0103] The control part includes a capacitance data acquisition card and a 32-bit microcontroller of model STM32F103C8T6. Each metal coating 6 is electrically connected to the capacitance data acquisition card through a wire 9. The control end of the sound and light alarm 8 and the capacitance data acquisition card are electrically connected to the 32-bit microcontroller.

[0104] As attached Figure 1 , Attachment Figure 4 As shown; the warning part also includes a contactor, a flexible conductive elastomer 10 arranged at the bottom of the sound and light alarm 8 and a flexible substrate 11 adhered to the bottom of the flexible conductive elastomer 10 and fixed to the upper side of the steering wheel 3; the contactor and the flexible conductive elastomer 10 are connected in series in the power supply circuit of the sound and light alarm 8, and the control end of the contactor is electrically connected to the 32-bit microcontroller; the flexible conductive elastomer 10 is made of a composite material I mixed with PDMS and gallium indium tin liquid metal, and a plurality of evenly distributed blocking particles 7 are arranged inside the composite material I.

[0105] The steering wheel 3 is in the shape of a clock face, and the number of the flexible capacitive pressure sensors 4 is 6; two of the flexible capacitive pressure sensors 4 are respectively located between 9 o'clock and 10 o'clock and between 3 o'clock and 4 o'clock of the clock face; the remaining flexible capacitive pressure sensors 4 are distributed in the empty positions of the clock face.

[0106] The droplet size of the gallium indium tin liquid metal in the composite material is 10 μm, and the droplet size of the gallium indium tin liquid metal in the composite material I is 53 μm; the gallium indium tin liquid metal in the composite material and the gallium indium tin liquid metal in the composite material I are both composed of the following raw materials in mass percentage: 68.5% gallium, 21.5% indium, and 10% tin; the blocking particles 7 are PDMS particles obtained by crushing the solidified PDMS block, and the particle size thereof is 100 μm to 225 μm;

[0107] The volume percentages of the components in the flexible dielectric elastomer are as follows: 10% of gallium indium tin liquid metal, 20% of blocking particles, and the balance of PDMS;

[0108] The volume percentages of the components in the flexible conductive elastomer 10 are as follows: 40% of gallium indium tin liquid metal, 30% of blocking particles, and the remainder of PDMS.

[0109] The volume percentages of PDMS, gallium indium tin liquid metal, and blocking particles 7 in the flexible dielectric elastomer and the volume percentages of PDMS, gallium indium tin liquid metal, and blocking particles 7 in the flexible conductive elastomer 10 are determined by a mixture design method based on a Scheffe trinomial model, as shown in formula (a):

[0110]

[0111] Where q = 3, y is the conductivity, each β represents the parameter to be estimated, ε represents the error, and E(ε) = 0, D(ε) = σ 2 , α represents the volume percentage of each of the q components in the mixture system, and the volume percentage of each component is in the normal simplex S q-1 The points are selected inside and must satisfy the following equation:

[0112]

[0113] The control part also includes a host computer, which is electrically connected to the control end of the sound and light alarm 8 and the 32-bit microcontroller respectively;

[0114] The sound and light alarm 8 includes an LED lamp and an alarm; the flexible substrate 11 is made of PDMS; the flexible electrode 5 is a rectangular electrode made of polyimide, and its length is 10mm, width is 5mm, and thickness is 100μm; the metal coating 6 is a gold layer with a thickness of 100nm; the flexible dielectric elastomer is in the shape of a rectangular parallelepiped, and its length is 10mm, width is 5mm, and thickness is 1mm; the flexible conductive elastomer 10 is in the shape of a long strip, and its width is 2mm and thickness is 0.5mm.

[0115] The preparation of the flexible dielectric elastomer is achieved by the following steps:

[0116] Step S1: preparing blocking particles 7; the specific steps are as follows:

[0117] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0118] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush at a speed of 3000 rpm for 3 minutes, pause for 2 minutes, shear and crush again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles 7;

[0119] Step S2: preparing a flexible dielectric elastomer; the specific steps are as follows:

[0120] Step S2.1: firstly, the gallium indium tin liquid metal is mixed with the PDMS solution so that the volume percentage of the gallium indium tin liquid metal in the flexible dielectric elastomer is 10%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 2 minutes, and then stirring with a vacuum stirrer for 10 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 10 μm, and a composite material is obtained;

[0121] Step S2.2: Add blocking particles 7 to the composite material obtained in step S2.1 and mix them so that the volume percentage of blocking particles 7 in the flexible dielectric elastomer is 20%; stir manually with a glass rod for 2 minutes, and then stir with a vacuum stirrer for 10 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material with blocking particles 7;

[0122] Step S2.3: Pour the composite material with blocking particles 7 obtained in step S2.2 into a rectangular resin mold, evacuate the air, and put it into a forced air drying oven for curing at a temperature of 80° C. for 2 hours, thereby obtaining a flexible dielectric elastomer.

[0123] The preparation of the flexible conductive elastomer 10 is achieved by the following steps:

[0124] Step S1: preparing blocking particles 7; the specific steps are as follows:

[0125] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0126] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush at a speed of 3000 rpm for 3 minutes, pause for 2 minutes, shear and crush again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles 7;

[0127] Step S2: preparing the flexible conductive elastomer 10; the specific steps are as follows:

[0128] Step S2.1: First, gallium indium tin liquid metal is mixed with PDMS solution so that the volume percentage of gallium indium tin liquid metal in the flexible conductive elastomer 10 is 40%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 2 minutes, and then stirring with a vacuum stirrer for 10 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 50 μm, to obtain a composite material I;

[0129] Step S2.2: Add blocking particles 7 to the composite material I obtained in step S2.1 and mix them so that the volume percentage of the blocking particles 7 in the flexible conductive elastomer 10 is 30%; stir manually with a glass rod for 2 minutes, and then use a vacuum stirrer for 10 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material I with blocking particles 7;

[0130] Step S2.3: Scrape the composite material I with blocking particles 7 obtained in step S2.2 onto a mold on a flexible substrate 11, evacuate the air, and place it in a forced air drying oven for curing at a temperature of 80°C for 2 hours, thereby obtaining a flexible conductive elastomer 10.

[0131] Example 2

[0132] The steering wheel 3 is in the shape of a clock face, and there are four flexible capacitive pressure sensors 4; two of the flexible capacitive pressure sensors 4 are respectively located between nine o'clock and ten o'clock and between three o'clock and four o'clock on the clock face; the remaining flexible capacitive pressure sensors 4 are distributed in the empty positions of the clock face.

[0133] The droplet size of the gallium indium tin liquid metal in the composite material is 50 μm, and the droplet size of the gallium indium tin liquid metal in the composite material I is 10 μm; the gallium indium tin liquid metal in the composite material and the gallium indium tin liquid metal in the composite material I are both composed of the following raw materials in mass percentage: 68.5% gallium, 21.5% indium, and 10% tin; the blocking particles 7 are PDMS particles obtained by crushing the solidified PDMS block, and the particle size thereof is 100 μm to 225 μm;

[0134] The volume percentages of the components in the flexible dielectric elastomer are as follows: 39.5% of gallium indium tin liquid metal, 30% of blocking particles, and the balance of PDMS;

[0135] The volume percentages of the components in the flexible conductive elastomer 10 are as follows: 60% of gallium indium tin liquid metal, 20% of blocking particles, and the remainder of PDMS.

[0136] The sound and light alarm 8 includes an LED lamp and an alarm; the flexible substrate 11 is made of platinum cured rubber; the flexible electrode 5 is a rectangular electrode made of polyimide, and its length is 50mm, width is 20mm, and thickness is 200μm; the metal coating 6 is a gold layer with a thickness of 100nm; the flexible dielectric elastomer is in the shape of a rectangular parallelepiped, and its length is 50mm, width is 20mm, and thickness is 5mm; the flexible conductive elastomer 10 is in the shape of a long strip, and its width is 4mm and thickness is 1mm.

[0137] The preparation of the flexible dielectric elastomer is achieved by the following steps:

[0138] Step S1: preparing blocking particles 7; the specific steps are as follows:

[0139] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0140] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush at a speed of 3000 rpm for 3 minutes, pause for 5 minutes, shear and crush again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles 7;

[0141] Step S2: preparing a flexible dielectric elastomer; the specific steps are as follows:

[0142] Step S2.1: firstly, the gallium indium tin liquid metal is mixed with the PDMS solution so that the volume percentage of the gallium indium tin liquid metal in the flexible dielectric elastomer is 39.5%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 4 minutes, and then stirring with a vacuum stirrer for 15 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 50 μm, and a composite material is obtained;

[0143] Step S2.2: Add blocking particles 7 to the composite material obtained in step S2.1 and mix them so that the volume percentage of blocking particles 7 in the flexible dielectric elastomer is 30%; stir manually with a glass rod for 4 minutes, and then stir with a vacuum stirrer for 15 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material with blocking particles 7;

[0144] Step S2.3: Pour the composite material with blocking particles 7 obtained in step S2.2 into a rectangular resin mold, evacuate the air, and put it into a forced air drying oven for curing at a temperature of 80° C. for 2 hours, thereby obtaining a flexible dielectric elastomer.

[0145] The preparation of the flexible conductive elastomer 10 is achieved by the following steps:

[0146] Step S1: preparing blocking particles 7; the specific steps are as follows:

[0147] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0148] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush at a speed of 3000 rpm for 3 minutes, pause for 5 minutes, shear and crush again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles 7;

[0149] Step S2: preparing the flexible conductive elastomer 10; the specific steps are as follows:

[0150] Step S2.1: First, gallium indium tin liquid metal is mixed with PDMS solution so that the volume percentage of gallium indium tin liquid metal in the flexible conductive elastomer 10 is 60%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 4 minutes, and then stirring with a vacuum stirrer for 15 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 10 μm, to obtain a composite material I;

[0151] Step S2.2: Add blocking particles 7 to the composite material I obtained in step S2.1 and mix them so that the volume percentage of the blocking particles 7 in the flexible conductive elastomer 10 is 20%; stir manually with a glass rod for 4 minutes, and then use a vacuum stirrer for 15 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material I with blocking particles 7;

[0152] Step S2.3: Scrape the composite material I with blocking particles 7 obtained in step S2.2 onto a mold on a flexible substrate 11, evacuate the air, and place it in a forced air drying oven for curing at a temperature of 80°C for 2 hours, thereby obtaining a flexible conductive elastomer 10.

[0153] Example 3

[0154] The steering wheel 3 is in the shape of a clock face, and the number of the flexible capacitive pressure sensors 4 is 8; two of the flexible capacitive pressure sensors 4 are respectively located between 9 o'clock and 10 o'clock and between 3 o'clock and 4 o'clock of the clock face; the remaining flexible capacitive pressure sensors 4 are distributed in the empty positions of the clock face.

[0155] The droplet size of the gallium indium tin liquid metal in the composite material is 20 μm, and the droplet size of the gallium indium tin liquid metal in the composite material I is 30 μm; the gallium indium tin liquid metal in the composite material and the gallium indium tin liquid metal in the composite material I are both composed of the following raw materials in mass percentage: 68.5% gallium, 21.5% indium, and 10% tin; the blocking particles 7 are PDMS particles obtained by crushing the solidified PDMS block, and the particle size thereof is 100 μm to 225 μm;

[0156] The volume percentages of the components in the flexible dielectric elastomer are as follows: 20.5% of gallium indium tin liquid metal, 24% of blocking particles, and the balance of PDMS;

[0157] The volume percentages of the components in the flexible conductive elastomer 10 are as follows: 48% of gallium indium tin liquid metal, 23% of blocking particles, and the remainder of PDMS.

[0158] The sound and light alarm 8 includes an LED lamp and an alarm; the flexible substrate 11 is made of Teflon; the flexible electrode 5 is a rectangular electrode made of polyimide, and its length is 31mm, width is 11mm, and thickness is 130μm; the metal coating 6 is a gold layer with a thickness of 100nm; the flexible dielectric elastomer is in the shape of a rectangular parallelepiped, and its length is 23mm, width is 11mm, and thickness is 3mm; the flexible conductive elastomer 10 is in the shape of a long strip, and its width is 2.8mm, and thickness is 0.7mm.

[0159] The preparation of the flexible dielectric elastomer is achieved by the following steps:

[0160] Step S1: preparing blocking particles 7; the specific steps are as follows:

[0161] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0162] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush at a speed of 3000 rpm for 3 minutes, pause for 3 minutes, shear and crush again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles 7;

[0163] Step S2: preparing a flexible dielectric elastomer; the specific steps are as follows:

[0164] Step S2.1: firstly, the gallium indium tin liquid metal is mixed with the PDMS solution so that the volume percentage of the gallium indium tin liquid metal in the flexible dielectric elastomer is 20.5%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 3.5 minutes, and then stirring with a vacuum stirrer for 12 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 20 μm, and a composite material is obtained;

[0165] Step S2.2: Add blocking particles 7 to the composite material obtained in step S2.1 and mix them so that the volume percentage of blocking particles 7 in the flexible dielectric elastomer is 24%; stir manually with a glass rod for 2.8 minutes, and then stir with a vacuum stirrer for 11 minutes, and during stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material with blocking particles 7;

[0166] Step S2.3: Pour the composite material with blocking particles 7 obtained in step S2.2 into a rectangular resin mold, evacuate the air, and put it into a forced air drying oven for curing at a temperature of 80° C. for 2 hours, thereby obtaining a flexible dielectric elastomer.

[0167] The preparation of the flexible conductive elastomer 10 is achieved by the following steps:

[0168] Step S1: preparing blocking particles 7; the specific steps are as follows:

[0169] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0170] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush at a speed of 3000 rpm for 3 minutes, pause for 4 minutes, shear and crush again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles 7;

[0171] Step S2: preparing the flexible conductive elastomer 10; the specific steps are as follows:

[0172] Step S2.1: First, gallium indium tin liquid metal is mixed with PDMS solution so that the volume percentage of gallium indium tin liquid metal in the flexible conductive elastomer 10 is 48%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 3.1 minutes, and then stirring with a vacuum stirrer for 14 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 30 μm, to obtain a composite material I;

[0173] Step S2.2: Add blocking particles 7 to the composite material I obtained in step S2.1 and mix them so that the volume percentage of the blocking particles 7 in the flexible conductive elastomer 10 is 23%; stir manually with a glass rod for 2.9 minutes, and then use a vacuum stirrer for 12 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material I with blocking particles 7;

[0174] Step S2.3: Scrape the composite material I with blocking particles 7 obtained in step S2.2 onto a mold on a flexible substrate 11, evacuate the air, and place it in a forced air drying oven for curing at a temperature of 80°C for 2 hours, thereby obtaining a flexible conductive elastomer 10.

[0175] Example 4

[0176] The steering wheel 3 is in the shape of a clock face, and there are 7 flexible capacitive pressure sensors 4; two of the flexible capacitive pressure sensors 4 are respectively located between 9 o'clock and 10 o'clock and between 3 o'clock and 4 o'clock of the clock face; the remaining flexible capacitive pressure sensors 4 are distributed in the empty positions of the clock face.

[0177] The droplet size of the gallium indium tin liquid metal in the composite material is 41 μm, and the droplet size of the gallium indium tin liquid metal in the composite material I is 23 μm; the gallium indium tin liquid metal in the composite material and the gallium indium tin liquid metal in the composite material I are both composed of the following raw materials in mass percentage: 68.5% gallium, 21.5% indium, and 10% tin; the blocking particles 7 are PDMS particles obtained by crushing the solidified PDMS block, and the particle size thereof is 100 μm to 225 μm;

[0178] The volume percentages of the components in the flexible dielectric elastomer are as follows: 10% of gallium indium tin liquid metal, 20% of blocking particles, and the balance of PDMS;

[0179] The volume percentages of the components in the flexible conductive elastomer 10 are as follows: 52% of gallium indium tin liquid metal, 20% of blocking particles, and the remainder of PDMS.

[0180] The sound and light alarm 8 includes an LED lamp and an alarm; the flexible substrate 11 is made of natural rubber; the flexible electrode 5 is a rectangular electrode made of polyimide, and its length is 28mm, width is 13mm, and thickness is 150μm; the metal coating 6 is a gold layer with a thickness of 100nm; the flexible dielectric elastomer is in the shape of a rectangular parallelepiped, and its length is 41mm, width is 19mm, and thickness is 4mm; the flexible conductive elastomer 10 is in the shape of a long strip, and its width is 3.2mm and thickness is 0.8mm.

[0181] The preparation of the flexible dielectric elastomer is achieved by the following steps:

[0182] Step S1: preparing blocking particles 7; the specific steps are as follows:

[0183] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0184] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush at a speed of 3000 rpm for 3 minutes, pause for 4.1 minutes, shear and crush again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles 7;

[0185] Step S2: preparing a flexible dielectric elastomer; the specific steps are as follows:

[0186] Step S2.1: First, gallium indium tin liquid metal is mixed with a PDMS solution so that the volume percentage of the gallium indium tin liquid metal in the flexible dielectric elastomer is 10%; the PDMS solution contains a prepolymer and a cross-linking agent; the mixture is manually stirred for 3 minutes using a glass rod, and then stirred for 11 minutes using a vacuum stirrer. During the stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 41 μm, thereby obtaining a composite material;

[0187] Step S2.2: Add blocking particles 7 to the composite material obtained in step S2.1 and mix them so that the volume percentage of blocking particles 7 in the flexible dielectric elastomer is 20%; stir manually with a glass rod for 3 minutes, and then stir with a vacuum stirrer for 13 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material with blocking particles 7;

[0188] Step S2.3: Pour the composite material with blocking particles 7 obtained in step S2.2 into a rectangular resin mold, evacuate the air, and put it into a forced air drying oven for curing at a temperature of 80° C. for 2 hours, thereby obtaining a flexible dielectric elastomer.

[0189] The preparation of the flexible conductive elastomer 10 is achieved by the following steps:

[0190] Step S1: preparing blocking particles 7; the specific steps are as follows:

[0191] Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block;

[0192] Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush at a speed of 3000 rpm for 3 minutes, pause for 3.3 minutes, shear and crush again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles 7;

[0193] Step S2: preparing the flexible conductive elastomer 10; the specific steps are as follows:

[0194] Step S2.1: First, gallium indium tin liquid metal is mixed with PDMS solution so that the volume percentage of gallium indium tin liquid metal in the flexible conductive elastomer 10 is 52%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 3.5 minutes, and then stirring with a vacuum stirrer for 11 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 23 μm, and a composite material I is obtained;

[0195] Step S2.2: Add blocking particles 7 to the composite material I obtained in step S2.1 and mix them so that the volume percentage of the blocking particles 7 in the flexible conductive elastomer 10 is 20%; stir manually with a glass rod for 3 minutes, and then use a vacuum stirrer for 13 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material I with blocking particles 7;

[0196] Step S2.3: Scrape the composite material I with blocking particles 7 obtained in step S2.2 onto a mold on a flexible substrate 11, evacuate the air, and place it in a forced air drying oven for curing at a temperature of 80°C for 2 hours, thereby obtaining a flexible conductive elastomer 10.

[0197] In the description of the present invention, it is necessary to understand that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0198] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A vehicle intelligent cockpit steering wheel hand-off detection device using a flexible force sensor, characterized in that: It includes pressure detection part, warning part and control part; The pressure detection part comprises N flexible capacitive pressure sensors (4) arranged between the upper surface of the foaming layer (1) and the inner surface of the leather layer (2) and distributed along the circumferential direction of the steering wheel (3), and N is a positive integer greater than or equal to 4; the flexible capacitive pressure sensor (4) comprises two flexible plates (5) arranged in parallel up and down and a flexible dielectric elastomer arranged between the two flexible plates (5), the opposite surfaces of the two flexible plates (5) are provided with metal coatings (6), and the upper surface and the lower surface of the flexible dielectric elastomer are respectively fixedly attached to the two metal coatings (6); the flexible dielectric elastomer is made of a composite material formed by mixing PDMS and gallium indium tin liquid metal, and a plurality of uniformly distributed blocking particles (7) are arranged inside the composite material; The warning part comprises an audible and visual alarm (8) arranged on the upper side of the middle part of the steering wheel (3); The control part comprises a capacitance data acquisition card and a 32-bit microcontroller, each metal coating (6) is electrically connected to the capacitance data acquisition card via a wire (9), and the control end of the sound and light alarm (8) and the capacitance data acquisition card are electrically connected to the 32-bit microcontroller; The warning part further comprises a contactor, a flexible conductive elastomer (10) arranged at the bottom of the sound and light alarm (8), and a flexible substrate (11) adhered to the bottom of the flexible conductive elastomer (10) and fixed to the upper side of the steering wheel (3); the contactor and the flexible conductive elastomer (10) are both connected in series to the power supply circuit of the sound and light alarm (8), and the control end of the contactor is electrically connected to the 32-bit microcontroller; the flexible conductive elastomer (10) is made of a composite material I formed by mixing PDMS and gallium indium tin liquid metal, and a plurality of uniformly distributed blocking particles (7) are arranged inside the composite material I; The volume percentages of PDMS, gallium indium tin liquid metal, and blocking particles (7) in the flexible dielectric elastomer and the volume percentages of PDMS, gallium indium tin liquid metal, and blocking particles (7) in the flexible conductive elastomer (10) are determined by a mixture design method based on a Scheffe trinomial model, wherein the Scheffe trinomial model is shown in formula (a): Where q = 3, y is the conductivity, each β represents the parameter to be estimated, ε represents the error, and E(ε) = 0, D(ε) = σ 2 , α represents the volume percentage of each of the q components in the mixture system, and the volume percentage of each component is in the normal simplex S q-1 The points are selected inside and must satisfy the following equation:

2. The vehicle intelligent cockpit steering wheel hand-off detection device using a flexible force sensor according to claim 1 is characterized in that: The steering wheel (3) is in the shape of a clock face, and the number of the flexible capacitive pressure sensors (4) is 4 to 8; two of the flexible capacitive pressure sensors (4) are respectively located between 9 o'clock and 10 o'clock and between 3 o'clock and 4 o'clock on the clock face; the remaining flexible capacitive pressure sensors (4) are evenly distributed in the empty positions of the clock face.

3. The vehicle intelligent cockpit steering wheel hand-off detection device using a flexible force sensor according to claim 1, characterized in that: The droplet size of the gallium indium tin liquid metal in the composite material and the droplet size of the gallium indium tin liquid metal in the composite material I are both 10 μm to 50 μm; the gallium indium tin liquid metal in the composite material and the gallium indium tin liquid metal in the composite material I are both composed of the following raw materials in mass percentage: 68.5% gallium, 21.5% indium, and 10% tin; the blocking particles (7) are PDMS particles obtained by crushing a solidified PDMS block, and the particle size thereof is 100 μm to 225 μm; The volume percentages of the components in the flexible dielectric elastomer are as follows: gallium indium tin liquid metal is greater than or equal to 10% and less than 40%, blocking particles (7) are 20% to 30%, and the balance is PDMS; The volume percentages of the components in the flexible conductive elastomer (10) are as follows: 40% to 60% of gallium, indium and tin liquid metal, 20% to 30% of blocking particles (7), and the remainder of PDMS.

4. The vehicle intelligent cockpit steering wheel hand-off detection device using a flexible force sensor according to claim 1, characterized in that: The control part also includes a host computer, which is electrically connected to the control end of the sound and light alarm (8) and the 32-bit microcontroller respectively.

5. The vehicle intelligent cockpit steering wheel hands-off detection device using a flexible force sensor according to claim 1, characterized in that: The sound and light alarm (8) comprises an LED lamp and an alarm; the flexible substrate (11) is made of PDMS, platinum-cured rubber, Teflon or natural rubber; the flexible plate (5) is a rectangular plate made of polyimide, and its length is 10 mm to 50 mm, its width is 5 mm to 20 mm, and its thickness is 100 μm to 200 μm; the metal coating (6) is a gold layer with a thickness of 100 nm; the flexible dielectric elastomer is in the shape of a rectangular parallelepiped, and its length is 10 mm to 50 mm, its width is 5 mm to 20 mm, and its thickness is 1 mm to 5 mm; the flexible conductive elastomer (10) is in the shape of a long strip, and its width is 2 mm to 4 mm, and its thickness is 0.5 mm to 1 mm.

6. The vehicle intelligent cockpit steering wheel hands-off detection device using a flexible force sensor according to claim 3 is characterized in that: The preparation of the flexible dielectric elastomer is achieved by the following steps: Step S1: preparing blocking particles (7); the specific steps are as follows: Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block; Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush them at a speed of 3000 rpm for 3 minutes, pause for 2 minutes to 5 minutes, shear and crush them again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles (7); Step S2: preparing a flexible dielectric elastomer; the specific steps are as follows: Step S2.1: First, gallium indium tin liquid metal is mixed with a PDMS solution so that the volume percentage of the gallium indium tin liquid metal in the flexible dielectric elastomer is greater than or equal to 10% and less than 40%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 2 minutes to 4 minutes, and then stirring with a vacuum stirrer for 10 minutes to 15 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 10 μm to 50 μm, and a composite material is obtained; Step S2.2: Add blocking particles (7) to the composite material obtained in step S2.1 and mix them so that the volume percentage of the blocking particles (7) in the flexible dielectric elastomer is 20% to 30%; stir manually with a glass rod for 2 minutes to 4 minutes, and then stir with a vacuum stirrer for 10 minutes to 15 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material with blocking particles (7); Step S2.3: Pour the composite material with blocking particles (7) obtained in step S2.2 into a rectangular resin mold, evacuate the air, and put it into a forced air drying oven for curing at a temperature of 80°C for 2 hours, thereby obtaining a flexible dielectric elastomer.

7. The vehicle intelligent cockpit steering wheel hand-off detection device using a flexible force sensor according to claim 3 is characterized in that: The flexible conductive elastomer (10) is prepared by the following steps: Step S1: preparing blocking particles (7); the specific steps are as follows: Step S1.1: Mix the prepolymer and the cross-linking agent in a mass ratio of 8:1 and stir evenly, pour into a mold, heat and cure, and obtain a PDMS block; Step S1.2: First, use scissors to cut the PDMS block into small blocks; then put the small blocks into a solid pulverizer, shear and crush them at a speed of 3000 rpm for 3 minutes, pause for 2 minutes to 5 minutes, shear and crush them again, and repeat the operation three times to obtain PDMS particles; use a 70-mesh sample sieve to select PDMS particles with a particle size of 100 μm to 225 μm, thereby obtaining blocking particles (7); Step S2: preparing a flexible conductive elastomer (10); the specific steps are as follows: Step S2.1: firstly, gallium indium tin liquid metal is mixed with PDMS solution so that the volume percentage of gallium indium tin liquid metal in the flexible conductive elastomer (10) is 40% to 60%; the PDMS solution contains a prepolymer and a cross-linking agent; manually stirring with a glass rod for 2 minutes to 4 minutes, and then stirring with a vacuum stirrer for 10 minutes to 15 minutes, and during stirring, the stirring speed is first set to 900 rpm, then adjusted to 2000 rpm, and then adjusted to 1000 rpm, so that the droplet size of the gallium indium tin liquid metal is 10 μm to 50 μm, to obtain a composite material I; Step S2.2: Add blocking particles (7) to the composite material I obtained in step S2.1 and mix them so that the volume percentage of the blocking particles (7) in the flexible conductive elastomer (10) is 20% to 30%; stir manually with a glass rod for 2 minutes to 4 minutes, and then use a vacuum stirrer for 10 minutes to 15 minutes. When stirring, first set the stirring speed to 900 rpm, then adjust the stirring speed to 2000 rpm, and then adjust the stirring speed to 1000 rpm, thereby obtaining a composite material I with blocking particles (7); Step S2.3: Scrape the composite material I with blocking particles (7) obtained in step S2.2 onto a mold on a flexible substrate (11), evacuate the air, and place it in a forced air drying oven for curing at a curing temperature of 80°C for 2 hours, thereby obtaining a flexible conductive elastomer (10).

Images