CN204813893U - Sole pressure distribution measuring device - Google Patents

Abstract

The utility model relates to a sole pressure distribution measuring device, including three -dimensional pressure measuring equipment body in sole and sensing system signal processor, a plurality of electric capacity pressure sensor that accept to press force information in the sole have been arranged in the three -dimensional pressure measuring equipment body in sole, the sensor includes ring electric capacity unique tuple and strip electric capacity unique tuple, ring electric capacity unique tuple is used for surveying the size of tangential force and normal force, strip electric capacity unique tuple is used for measuring the direction of tangential force, through plantar three -dimensional ressure measurement, establish disease complication monitoring and forewarning system, the system provides the reference frame for expert's aid decision, provide the reference frame to clinic treatment evaluation.

Description

Plantar pressure distribution measuring device

Technical Field

The utility model belongs to the technical field of medical instrument, a clinical medicine treatment effect detecting system is related to, concretely relates to plantar pressure distribution measuring device.

Background

The distribution of human plantar pressure reflects the conditions related to the structure and function of the foot, the posture control of the whole body and the like. The physiological and pathological mechanical parameters and functional parameters of the human body under various body states and motions can be obtained by testing and analyzing the plantar pressure, and the method has important significance for clinical medical diagnosis, disease degree determination, postoperative curative effect evaluation, biomechanics and rehabilitation research. The dynamic plantar pressure measurement is an important quantitative inspection and analysis means, and has wide application prospect. At present, the technology is used in function and curative effect evaluation before and after artificial joint operation, examination and follow-up of trunk and lower limb diseases, data provision for artificial limb and artificial joint design, analysis and evaluation of rehabilitation training and physical training, early prediction and treatment of diabetic foot, and the like.

Foot ulcers are one of the serious complications of diabetes, and diabetic patients suffering from foot ulcers have a significantly increased risk of amputation and death. Foot ulcers occur as a result of prolonged mechanical pressure increases due to increased plantar pressure caused by peripheral neuropathy. There are many foreign documents that demonstrate that abnormal elevation of dynamic plantar pressure is clearly associated with the development of diabetic plantar ulcers.

The existing sole pressure data acquisition device adopts pressure sensors, but the pressure sensors only acquire the pressure in the vertical direction: for example, the Chinese patent CN201110074892.6 adopts 10 film pressure sensors corresponding to sole pressure distribution points; CN201010230489.3 uses a matrix pressure sensor of 8 columns × 10 rows, and CN2012102984097 uses a matrix of piezoresistors of 40 × 40; however, it is known that the force between the sole and the active surface is also horizontal during walking. Collecting the force in the vertical direction alone is not sufficient to reflect the force of the sole and the active surface.

Disclosure of Invention

In order to overcome the not enough of prior art, the utility model provides a plantar pressure distribution measuring device for diabetes complication prevention control through carrying out ingenious setting to capacitanc pressure sensor structure, measures plantar three-dimensional pressure to through the improvement to sensor polar plate structure, eliminate the inter-dimensional coupling, through the analysis to plantar pressure, establish disease complication control early warning system, for the expert assists decision-making system and provides the reference basis, provide the reference basis to clinical treatment effect evaluation.

The technical scheme of the utility model is that: a plantar pressure distribution measuring device comprises a plantar three-dimensional pressure measuring device body and a sensing system signal processor, wherein a plurality of capacitance pressure sensors for receiving plantar pressure information are arranged in the plantar three-dimensional pressure measuring device body, each capacitance pressure sensor comprises a circular capacitance unit group and a strip-shaped capacitance unit group, the strip-shaped capacitance unit groups are arranged at four corners of an outer substrate of the circular capacitance unit group, each circular capacitance unit group comprises more than two pairs of circular capacitance unit pairs, each circular capacitance unit pair comprises two circular capacitance units, each strip-shaped capacitance unit group comprises an X-direction differential capacitance unit group and a Y-direction differential capacitance unit group, each X-direction differential capacitance unit group and each Y-direction differential capacitance unit group comprises more than two capacitance unit modules which mutually form a differential, and each capacitance unit module is of a comb-tooth-shaped structure consisting of more than two strip-shaped capacitance units, each ring capacitor unit and each strip capacitor unit respectively comprise a driving electrode of an upper polar plate and an induction electrode of a lower polar plate.

The utility model discloses a three-dimensional pressure measurement device body in sole pressure distribution measuring device's sole is from top to bottom including recovering substrate layer, lead layer and the stereoplasm backing plate of foam blanket, sensor layer, elasticity material, recovers the foam blanket and chooses polyurethane foam, organosilicon foam or modified organosilicon for use to fill inorganic short-staple, lead layer lead wire to lead toThe device is connected to a signal processor of a sensing system in a parallel or independent mode, and the upper surface of the plantar three-dimensional pressure measuring device is rectangular, has the width of 45 cm-1 m and the length of 3 m-5 m. The induction electrode and the driving electrode of each circular ring capacitor unit are opposite and same in shape, the driving electrode and the induction electrode of each strip capacitor unit are same in width, the length of the driving electrode of each strip capacitor unit is larger than that of the induction electrode, and left difference delta is reserved at two ends of the length of the driving electrode of each strip capacitor unit_{Left side of}And the right difference position delta_{Right side}，b_{0 drive}＝b_{Feeling of 0}+δ_{Right side}+δ_{Left side of}Wherein b is_{0 drive}Length of the driving electrode of the strip-shaped capacitor unit, b_{Feeling of 0}The length of the induction electrode of the strip-shaped capacitance unit. Left difference position delta of the strip-shaped capacitor unit_{Left side of}Right difference delta_{Right side}And is andwherein d is₀Is the thickness of the elastic medium, G is the shear modulus, τ, of the elastic medium_maxThe maximum stress value. The driving electrodes and the sensing electrodes of the strip-shaped capacitor units of the two groups of capacitor unit modules which mutually form the differential are provided with initial dislocation offsets along the width direction, and the dislocation offsets have the same size and opposite directions. The ring capacitor unit group comprises n concentric ring capacitor unitsWherein, a_{Flat plate}Length of parallel plate, r_{Round (T-shaped)}Is the width of the ring capacitor unit, a_{Delta circle}And the electrode distance between two adjacent circular capacitor units. The X-direction differential capacitance unit group and the Y-direction differential capacitance unit group both comprise m strip-shaped capacitance units,wherein, a_{Flat plate}Length of parallel plate, a_{Delta bar}Is the electrode spacing between two adjacent strip-shaped capacitor units, a₀The width of the strip-shaped capacitor unit. The width r of the concentric ring capacitor unit_{Round (T-shaped)}And strip-shaped capacitor sheetWidth of element a₀Equal; electrode spacing a of strip-shaped capacitor unit_{Delta bar}And the electrode spacing a of the circular ring capacitor unit_{Delta circle}Equal, width of the strip-shaped capacitor unitWherein d is₀E is the Young's modulus of the elastic medium, and G is the shear modulus of the elastic medium. The drive electrodes of the ring capacitor unit group and the strip capacitor unit group are connected with the sensing system signal processor through an outgoing line, the induction electrode of each ring capacitor unit of the ring capacitor unit group is connected with the sensing system signal processor through an independent lead, and the induction electrodes of the capacitor unit modules of the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group are connected with the sensing system signal processor through an outgoing line respectively. Intermediate converters are respectively arranged among the ring capacitor units, the capacitor unit modules and the sensing system signal processor and are used for setting transmission coefficients of voltage to capacitance or frequency to capacitance. The sensor system signal processor comprises a multi-channel signal high-speed switching circuit, an A/D conversion circuit and a control circuit, wherein the high-speed switching circuit comprises a three-stage switching circuit, the output of the previous stage switching circuit is the input signal of the next stage switching circuit, and the last stage switching circuit is sent into the control circuit through the A/D conversion circuit.

The invention has the beneficial effects that: the three-dimensional force of the foot can be detected by using the three-dimensional force pressure sensor, the three-dimensional pressure data of the sole is used for researching the diabetic complication foot ulcer, the measuring method is convenient and simple, the pain of a patient can not be brought, and the sole data is used for predicting the foot ulcer to prevent the disease deterioration. Additionally, the utility model discloses a normal force and tangential force can be measured simultaneously to the sensor, and sensitivity is high, and the polar plate utilization efficiency is high, and whole ring electric capacity unit group all makes contributions to the normal force to better dynamic behavior has.

Drawings

Fig. 1 is an area analysis diagram of the offset and dislocation of concentric rings according to the embodiment of the present invention.

Fig. 2 is an analysis diagram of the dislocation of the outer concentric rings to the outer diameter circle according to the embodiment of the present invention.

Fig. 3 is a plan view of a parallel plate capacitor according to an embodiment of the present invention.

Fig. 4 is a structural diagram of a drive electrode according to an embodiment of the present invention.

Fig. 5 is a rectangular coordinate system of the flat capacitor plate according to the embodiment of the present invention.

Fig. 6 is a structural diagram of two sets of circular capacitor sets according to an embodiment of the present invention.

Fig. 7 is an initial misalignment map of a differential strip capacitor cell according to an embodiment of the present invention.

Fig. 8 is a diagram illustrating the deviation of the differential strip-shaped capacitor unit after being stressed according to the embodiment of the present invention.

Fig. 9 is a schematic signal differential diagram of a unit capacitor pair according to an embodiment of the present invention.

Fig. 10 is a structural view of a foot ulcer monitoring device according to an embodiment of the present invention.

Wherein, 1 resumes the foam layer, 2 sensor layers, 3 substrate layers, 4 lead wire layers, 5 backing plates, 6 lead wire interface boards.

Detailed Description

The following description of the embodiments with reference to the drawings is intended to illustrate the present invention in further detail, such as the shapes and structures of the components, the mutual positions and connections between the components, the functions and working principles of the components, the manufacturing process, and the operation and use methods, etc., so as to help those skilled in the art understand the present invention more completely, accurately and deeply.

The utility model discloses a main thinking is: the utility model discloses a clinical treatment effect evaluation system includes sole three-dimensional pressure measuring device body and sensing system signal processor two parts, has arranged a plurality of flat capacitive pressure sensor that accept sole pressure information in the sole three-dimensional pressure measuring device body, and sensing system signal processor is the control circuit who is used for gathering sole three-dimensional pressure measuring device body information, accomplishes the collection, handles and sends of sole pressure information; and finally, carrying out noise reduction processing on the signals, and increasing the signal-to-noise ratio to ensure that the acquired signals are reliable and effective.

As shown in fig. 10, for the utility model discloses a three-dimensional pressure measurement device of sole's structure chart, measuring device are including resumeing foam blanket, sensor layer, substrate layer, lead layer, bolster layer and lead wire interface board, and the bottommost layer is the backing plate of hard material preparation, and the superiors are for resumeing the foam blanket, and the thickness of foam is 20mm-30mm, resumes the foam and select materials such as polyurethane foam, organosilicon foam, modified organosilicon packing inorganic short-staple for use. The sensor layer is arranged below the recovery foam layer, the substrate layer is arranged below the sensor layer, the lead layer is arranged below the substrate layer, the sensor and the lead are respectively arranged on different layers, so that mutual interference between the sensor and the lead is avoided, and the sensor lead of the lead layer is connected into the lead interface board. The substrate layer is an elastic matrix material and can be a rubber material, the capacitive pressure sensor layer is arranged between the substrate layer made of an elastic material and the recovery foam layer, and the substrate layer made of the elastic material and the recovery foam layer are both made of flexible materials, so that the pressure sensor can be protected, and the stress is uniform. The upper surface of the measuring device is rectangular, the width is 45 cm to 1m, the length is 3 m to 5 m, a tested person can walk on the measuring device conveniently, and the pressure change during standing and the pressure change of the sole during normal walking can be monitored.

The utility model discloses a capacitanc pressure sensor includes ring electric capacity unit group and strip electric capacity unit group, circleThe ring capacitor unit group is used for measuring the tangential force and the normal force, the strip capacitor unit group is used for measuring the direction of the tangential force, and the strip capacitor unit group is arranged at four corners outside the substrate circular ring capacitor unit group. The ring electric capacity unit group includes that ring electric capacity unit is right more than two sets of, ring electric capacity unit is right including two ring electric capacity units, strip electric capacity unit group includes X direction differential electric capacity unit group and Y direction differential electric capacity unit group, and X direction differential electric capacity unit group and Y direction differential electric capacity unit group all include the differential electric capacity unit module of mutual formation more than two, the electric capacity unit module adopts the broach structure of constituteing by the strip electric capacity unit more than two, and every ring electric capacity unit and strip electric capacity unit all include the drive electrode of upper polar plate and the induction electrode of bottom plate. The induction electrode and the driving electrode of each circular ring capacitor unit are opposite and same in shape, the driving electrode and the induction electrode of each strip capacitor unit are same in width, the length of the driving electrode of each strip capacitor unit is larger than that of the induction electrode, and left difference delta is reserved at two ends of the length of the driving electrode of each strip capacitor unit_{Left side of}And the right difference position delta_{Right side}，b_{0 drive}＝b_{Feeling of 0}+δ_{Right side}+δ_{Left side of}Wherein b is_{0 drive}Length of the driving electrode of the strip-shaped capacitor unit, b_{Feeling of 0}The length of the induction electrode of the strip-shaped capacitance unit. Left difference position delta of the strip-shaped capacitor unit_{Left side of}Right difference delta_{Right side}And is andwherein d is₀Is the thickness of the medium, G is the shear modulus, τ, of the elastic medium_ymaxThe maximum stress value. The driving electrodes and the sensing electrodes of the strip-shaped capacitor units of the two groups of capacitor unit modules which mutually form the differential are provided with initial dislocation offsets along the width direction, and the dislocation offsets have the same size and opposite directions. The ring capacitor unit group comprises n concentric ring capacitor unitsWherein, a_{Flat plate}Length of parallel plate, r_{Round (T-shaped)}Is the width of the ring capacitor unit, a_{Delta circle}And the electrode distance between two adjacent circular capacitor capacitors. The capacitor unit module adopts a comb-tooth structure, the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group both comprise m strip-shaped capacitor units,wherein, a_{Flat plate}Length of parallel plate, a_{Delta bar}Is the electrode spacing between two adjacent strip-shaped capacitor units, a₀The width of the strip-shaped capacitor unit. The width r of the concentric ring capacitor unit_{Round (T-shaped)}And the width a of the strip-shaped capacitor unit₀Equal; electrode spacing a of strip-shaped capacitor unit_{Delta bar}And the electrode spacing a of the circular ring capacitor unit_{Delta circle}Equal, width of the strip-shaped capacitor unitWherein d is₀E is the Young's modulus of the elastic medium, and G is the shear modulus of the elastic medium. The drive electrodes of the ring capacitor unit group and the strip capacitor unit group are connected with the sensing system signal processor through an outgoing line, the induction electrode independent lead of each ring capacitor unit of the ring capacitor unit group is connected with the sensing system signal processor, and the induction electrodes of the capacitor unit modules of the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group are respectively led out through an outgoing line and connected with the sensing system signal processor. Intermediate converters are respectively arranged among the ring capacitor units, the capacitor unit modules and the sensing system signal processor and are used for setting transmission coefficients of voltage or frequency to the capacitors.

The derivation and principle of the present invention, the shape, structure, mutual position and connection relationship between the parts, the function and operation principle of the parts, the manufacturing process and operation method, etc. will be described in further detail with reference to fig. 1-10.

1.1 capacitance formula and input-output characteristics thereof

The initial capacitance of the parallel plates is:

$C_0=\frac{{\mathrm{\ϵ}}_0\·{\mathrm{\ϵ}}_r\·A_0}{d_0}---\left(1\right)$

in the formula, epsilon₀The electric constant of the vacuum medium is 8.85PF/m, epsilon_r2.5 is the relative permittivity of the dielectric, a₀The initial facing area of the upper and lower polar plates. d₀Receive sigma_nIs excited to produce a relative deformation epsilon_n＝δ_n/d₀＝σ_nAnd E, substituting the formula (1) to obtain the input-output characteristics

$C_n={\mathrm{\ϵ}}_0\·{\mathrm{\ϵ}}_r\frac{A_0}{d_0(1-{\mathrm{\ϵ}}_n)}={\mathrm{\ϵ}}_0\·{\mathrm{\ϵ}}_r\frac{A_0}{d_0(1-\frac{F_n}{AE})}---\left(2\right)$

1.2 Linearity and sensitivity under Normal stress

1.2.1 Normal Linearity

(2) In the formula F_nIn the denominator, therefore C_n＝f(F_n) The relationship of (a) is non-linear. Maximum value sigma in the range of conversion_nmaxε compared with the dielectric elastic constant E_nIs a very small quantity, i.e. epsilon in the denominator_n<<1, expanding the formula (2) according to a series, and omitting high-order infinitesimal more than the square, which can be simplified as follows:

$C_n=C_0(1+\mathrm{\&epsiv;})=C_0(1+\frac{F_n}{A\&CenterDot;E})---\left(3\right)$

can be seen in C_nAnd F_nThe maximum relative error of the normal linearity in the conversion characteristic of (a) is close to zero.

1.2.2 sensitivity

Definition of sensitivity by Normal

According to the formula (2)

$S_{n2}=\frac{{\mathrm{dC}}_n}{{\mathrm{dF}}_n}=C_0\&CenterDot;\frac{1}{1-2\mathrm{\&epsiv;}}=C_0\&CenterDot;\frac{1}{1-2\frac{F_n}{A\&CenterDot;E}}---\left(4\right)$

The linear sensitivity can be obtained according to the formula (3),

S_n1＝C₀/AE＝ε₀ε_r/d₀E(5)

S_n2with F_nAnd is changed to F_nThe greater, S_n2The larger, the slightly non-linear over the entire conversion characteristic.

1.3 relationship between tangential displacement and effective area of circular ring capacitor

Analysis was performed for concentric ring capacitance pairs, as shown in FIG. 1, R₁Is the outer radius of the circle, R₂The radius of the inner circle, R equals the width of the ring, and equals the radius of the large outer circle R₁Inner circle radius R₂. Force F on a section of the drive electrode_xCausing a shear dislocation between the corresponding driving and sensing electrodes, and d_xThe displacement of the tangent plane and the dislocation area are S_{Inner part}And S_{Outer cover}The initial facing area of the electrode plate should be pi (R)₁ ²-R₂ ²). FIG. 2 is an analysis graph of capacitance of outer concentric ring versus outer diameter circle, where the distance between the centers of the two circles is d_xThe intersection point of the two circle centers and the two circles forms a rhombus before and after moving, and S can be calculated_{Outer cover}Area of (d):

in the above formula, there is d_x<<R₁To thereby obtain

By

Will be provided withAnd the high-order terms are omitted,

similarly, it can be known that S_{Inner part}＝2R₂d_xTherefore, the error area of the concentric ring capacitor is S-2R₁d_x+2R₂d_x。

1.4 capacitance Change of the Ring capacitive cell group under tangential stress τ excitation

The tangential stress tau does not change the geometric size parameter A of the polar plate₀To the thickness d of the medium₀Nor is it affected. However tau_xAnd τ_yThe spatial structure of the parallel plate capacitor is changed, and dislocation offset occurs between the upper and lower electrode plates facing in the forward direction. Dislocation deviation d of polar plate under action of tau_x. When tau is zero, the upper and lower electrodes of the circular ring capacitor unit are opposite, and the effective section between the upper and lower electrodesIn FIG. 2, at τ_xUnder the action of right direction, the upper polar plate is displaced to right relative to the lower polar plate_xThereby the effective area between the upper and lower polar plates is calculated when the capacitance is calculated $A_{\mathrm{\&tau;}}={\mathrm{\&pi;R}}_1^2-{\mathrm{\&pi;R}}_2^2-2R_1{d}_x-2R_2{d}_x,$ The resulting capacitance is:

$C_{\mathrm{\&tau;}x}=\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r\&CenterDot;({\mathrm{\&pi;R}}_1^2-{\mathrm{\&pi;R}}_2^2-2R_1{d}_x-2R_2{d}_x)}{d_0}---\left(6\right)$

according to shear Hooke's law

τ_x＝γ_x·G＝G·δ_x/d₀(7)

Substituting (7) into (6) to obtain

$C_{\mathrm{\&tau;}x}=C_0-\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r\&CenterDot;2(R_1+R_2)d_x}{d_0}=C_0-\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r\&CenterDot;2(R_1+R_2)F_x}{A_{\mathrm{\&tau;}}G}=C_0-\frac{2{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r{F}_x}{G\mathrm{\&pi;}(R_1-R_2)}---\left(8\right)$

(8) The formula is the input-output characteristic under shear stress, C_τAnd τ_xIn a linear relationship, its sensitivity

$S_{\mathrm{\&tau;}x}=\frac{{\mathrm{dC}}_{\mathrm{\&tau;}}}{{\mathrm{dF}}_x}=\frac{2{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{G\mathrm{\&pi;}(R_1-R_2)}---\left(9\right)$

From equation (9), the tangential sensitivity and R can be seen₁-R₂In relation to this, the tangential sensitivity is inversely proportional to the width of the ring, the smaller the width the higher the sensitivity.

Design of 2-plate capacitor

2.1 design of Flat capacitors

See the electrode plan layout in FIG. 3 and the block diagram of the drive electrode in FIG. 4, at a 10X 10mm thickness²The circular ring type contact parallel plate three-dimensional pressure sensor on the substrate comprises a circular ring capacitance unit group and a strip-shaped capacitance unit group, wherein the circular ring capacitance unit group is used for measuring the tangential force and the normal force, the strip-shaped capacitance unit group is used for measuring the direction of the tangential force, and the strip-shaped capacitance unit group is arranged at four corners outside the circular ring capacitance unit group of the substrate. Therefore, the area of the parallel plates can be effectively used, the circular capacitor unit group is paved on the whole parallel plate, the circular capacitor unit group plays a role in measuring the three-dimensional force, and the strip-shaped capacitor unit group effectively utilizes the space at four corners of the parallel plate after the circular capacitor unit group is paved, and is used for measuring the direction of the three-dimensional force tangential force. The driving electrode and the induction electrode of the circular ring capacitor unit group are both composed of n concentric circular rings, and n is an even number, so that an n/2 circular ring capacitor unit pair is formed. The hatched portions represent the outer mold sections of the lost wax casting process, which geometry and dimensions should also be precise during mechanical forming.

Referring to the rectangular coordinate system of the plate capacitor of fig. 5, the origin of the coordinate system is at the origin of the concentric circles of the circular capacitor unit groups, the X-axis and the y-axis are along the diagonal directions of the plate capacitor, the X-direction differential capacitor unit group includes an X-direction differential capacitor unit group i and an X-direction differential capacitor unit group iii, and the X-direction differential capacitor unit group i and the X-direction differential capacitor unit group iii are divided intoThe Y-direction differential capacitor unit group II and the Y-direction differential capacitor unit group IV are respectively positioned on the positive half shaft and the negative half shaft of the Y-axis and are symmetrical along the Y-axis, the X-direction differential capacitor unit group I and the X-direction differential capacitor unit group III form a pair tau_xThe differential capacitor unit group II and the differential capacitor unit group IV form a pair tau_yA responsive differential capacitive cell combination.

The ring capacitor unit group comprises n concentric ring capacitor unitsWherein, a_{Flat plate}Length of parallel plate, r_{Round (T-shaped)}Is the width of the ring capacitor unit, a_{Delta circle}And the electrode distance between two adjacent circular capacitor capacitors. The capacitor unit module adopts a comb-tooth structure, the X-direction differential capacitor unit group and the Y-direction differential capacitor unit group both comprise m strip-shaped capacitor units, wherein, a_{Delta bar}An electrode distance a is arranged between two adjacent strip-shaped capacitor units₀The width of the strip-shaped capacitor unit. Width r of concentric ring capacitor unit_{Round (T-shaped)}And the width a of the strip-shaped capacitor unit₀Equal; electrode spacing a of strip-shaped capacitor unit_{Delta bar}And the distance a between the electrodes of the circular capacitor_{Delta circle}Equal, width of the strip-shaped capacitor unitWherein d is₀E is the Young's modulus of the elastic medium, and G is the shear modulus of the elastic medium.

2.2 excitation Signal and coordinate System

The circular-ring capacitor unit is placed in a rectangular coordinate system shown in fig. 5, three-dimensional excitation is applied to the outer surface of the capacitor plate, and the generated contact-type acting force has three directional components of Fx, Fy and Fz, the acting directions of Fx and Fy are along the X axis and the Y axis, and the acting direction of Fz is along the OZ axis, namelyThe direction, normal direction and tangential direction stress are both stress tensors, and the response of capacitance can be output from the lead wires of the electrodes; normal stress sigma_nFn/A, whereinThe pole plate is a normal force bearing surface, and Fn is a normal component; generating paired tangential stresses tau on both side surfaces_{Cutting machine}＝F_{Cutting machine}/A。

According to Hooke's law, σ, in elastic mechanics_nAnd τ_x，τ_yA corresponding deformation of the elastomer will occur. Wherein,

${\mathrm{\&sigma;}}_n=E\&CenterDot;{\mathrm{\&epsiv;}}_n=E\&CenterDot;{\mathrm{\&delta;}}_n/d_0=\frac{F_n}{A}$

wherein E is the Young's modulus GN/m of the elastic medium²G is the shear modulus GN/m of the elastic medium²δ n is the normal displacement (unit: μm) of the elastic medium, δ x and δ y are the relative dislocation (unit: μm) of the upper and lower electrode plates of the circular ring capacitor unit, and the sign of the displacement is determined by the orientation of the coordinate axis.

2.3 calculation of Normal and tangential force magnitudes

And selecting the nth ring capacitor unit and the nth/2 ring capacitor unit, and calculating a composition equation set by establishing the ring capacitor units, as shown in fig. 6. After the electrode plate is subjected to normal and tangential excitation, the output capacitance of the nth circular ring capacitance unit is set as C₁N/2 ring capacitor units with output capacitance of C₂Tangential displacement of d_xNormal capacitance pole distance of d_n，S₁₀Is the initial facing area of the outer ring, S₂₀Is the initial facing area of the inner ring.

$C_1=\frac{\mathrm{\&epsiv;}(S_{10}-S1)}{d_n}=\frac{\mathrm{\&epsiv;}({\mathrm{\&pi;R}}_1^2-{\mathrm{\&pi;R}}_2^2)}{d_n}-\frac{\mathrm{\&epsiv;}(2R_1{d}_x+2R_2{d}_x)}{d_n}---\left(10\right)$

$C_2=\frac{\mathrm{\&epsiv;}(S_{20}-S2)}{d_n}=\frac{\mathrm{\&epsiv;}({\mathrm{\&pi;r}}_1^2-{\mathrm{\&pi;r}}_2^2)}{d_n}-\frac{\mathrm{\&epsiv;}(2r_1{d}_x+2r_2{d}_x)}{d_n}---\left(11\right)$

Will be provided withObtaining:

$C_1-C_2*\frac{R_1+R_2}{r_1+r_2}=\frac{\mathrm{\&epsiv;}\mathrm{\&pi;}(R_1^2-R_2^2)}{d_n}-\frac{R_1+R_2}{r_1+r_2}*\frac{\mathrm{\&epsiv;}\mathrm{\&pi;}(r_1^2-r_2^2)}{d_n}$

in the above formula $\frac{R_1+R_2}{r_1+r_2}=K,$ Then $d_n=\frac{\mathrm{\&epsiv;}(S_{10}-{\mathrm{KS}}_{20})}{C_1-{\mathrm{KC}}_2}$

According to $d_n=d_0-\mathrm{\&Delta;}d=d_0(1-\frac{F_n}{E\&CenterDot;S_0})$

Therefore, the following steps are carried out: $F_n=\frac{(d_n-d_0)E\&CenterDot;S_0}{d_0}$

mixing the above (10) × C₂-(11)*C₁Obtaining:

$d_x=\frac{C_2{S}_{10}-C_1{S}_{20}}{2C_2(R_1+R_2)-2C_1(r_1+r_2)};$

by $\mathrm{\&gamma;}=\frac{\mathrm{\&tau;}}{G}=\frac{F_{\mathrm{\&tau;}}}{G\&CenterDot;S_0}=\frac{d_x}{d_0}=\frac{C_2{S}_{10}-C_1{S}_{20}}{d_{0}2C_2(R_1+R_2)-d_{0}2C_1(r_1+r_2)},$ So F_τIs composed of

$F_{\mathrm{\&tau;}}=\frac{(C_2{S}_{10}-C_1{S}_{20})\&CenterDot;G\&CenterDot;S_0}{d_{0}2C_2(R_1+R_2)-d_{0}2C_1(r_1+r_2)}$

2.4 determination of the direction of tangential force

2.4.1 strip-shaped capacitor unit group structure and parameter design

To realize tau_xAnd τ_yTangential response does not mutually influence, and a reserved difference delta is reserved at two ends of the length of the driving electrode₀Thus b is_{0 drive}＝b_{0 bottom}+2·δ₀Wherein in b_{0 drive}The length reservation of the two ends should be ensured theoreticallyCalculated value thereof is ${10}^{-5}\&times;\frac{70\&times;{10}^3}{2.4\&times;{10}^6}2.9\&times;{10}^{-8}m={10}^{-2}um<<1um,$ Therefore, it should be ensured in terms of process b_{0 drive}－b_{0 bottom}Not less than 0.01 mm. To realize tau_xAnd τ_yThe normal capacitance response is not influenced, and the driving electrode and the sensing electrode of each strip-shaped capacitance unit are arranged on the plane and are provided with certain dislocation offset, so that the mutual influence is eliminated through differential motion.

As shown in fig. 4, four dotted line boxes in the figure are taken as the reference of the sensing electrode on the lower plate, and the position of the sensing electrode on the lower PCB substrate is taken as a reference, then the arrangement of the driving electrode on the upper PCB substrate should be taken as the reference of the edge line of the PCB substrate. Each strip-shaped capacitor unit comprises a driving electrode of an upper polar plate and an induction electrode of a lower polar plate, and the width of each strip-shaped capacitor unit is set to be a₀The width of the groove between two strip-shaped capacitor units is a_δThe pitch of each strip-shaped capacitor unit is a₀+a_δ. Thus ensuring tau already when calculating the normal capacitance output response_xAnd τ_yThe normal capacitance response is not affected. The differences between them and the geometric datum line are delta₀(0.1mm) to ensure that the X-direction differential capacitance unit group I and the X-direction differential capacitance unit group III only generate a pair tau_xThe Y-direction differential capacitance unit group II and the Y-direction differential capacitance unit group IV only generate a pair tau_ySetting an initial misalignment offset delta_xoThe value of which should be guaranteedCalculated value and delta thereof₀Similarly, their initial misalignment offsets are all set at δ_xo＝δ_yo0.01mm to ensure that four capacitor units are at tau_xAnd τ_yTwo groups of differential capacitance pairs can be generated under tangential excitation.

In FIG. 7, a pair of capacitors C_LAnd C_RElectrode size a₀、b₀、d₀All are the same, initial misalignment offset δ₀Also the same, the difference being the left capacitor C_LUpper layer delta₀The point of the tip is pointed at + OX, and the capacitor C on the right_RUpper layer delta₀The sharp corners point to-OX. When tau is_xWhen the content is equal to 0, the content,i.e. the capacitance corresponding to the shaded part of the figure. On the basis thereof, e.g. in-F_xProducing delta under excitation_xThe misalignment of (2) causes a capacitance increase and decrease effect as shown in FIG. 8,

$C_L=\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r\&CenterDot;b_0\&CenterDot;(a_0-{\mathrm{\&delta;}}_0\&PlusMinus;{\mathrm{\&delta;}}_x)}{d_0}---\left(12\right)$

in FIG. 8, C_LAnd C_RDifferential capacitor pair_xWill produce + -delta_xAnd + -. DELTA.C_τIn response to (2) the response of (c),δ₀should be of a size thatDesirable delta₀By 10 μm, formula (11) can be modified to

$C_{\mathrm{\&tau;}x}=C_{\mathrm{\&tau;}0}\&PlusMinus;\frac{{\mathrm{\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{{\mathrm{Ga}}_0}{F}_x---\left(13\right)$

In the formula,initial capacitance when the shear stress is zero, and formula (13) is the shear stress input-output characteristic, C_τxAnd F_xIs a linear relationship, and the sensitivity thereof

A is shown by formula (13)₀The smaller the sensitivity of the tangential stress response is, the larger the capacitance unit of the present invention is, the more the strip-shaped capacitance unit group composed of a plurality of strip-shaped capacitors is adopted.

2.4.2 tangential stress Direction calculation

C_ⅠTo C_ⅡAnd C_ⅢTo C_ⅣCan be used forImplementing two differential combinations, e.g. signal differential schematic of cell capacitor pair of FIG. 9, processed by differential techniques, the total response of the differential outputs

$O_{\mathrm{\&tau;}x}=\frac{2{\mathrm{mK\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{a_{0}G}{F}_x$

In which either the normal excitation F_nOr tangential excitation F_yAll are not to O_τEffecting, i.e. automatically cancelling, sigma_nAnd τ_yFor tau_xOr interference of the total output. Because the equivalent and congruent capacitance changes are automatically eliminated in all operations in which the signals contain subtraction. And F_yAnd F_xTo sigma_nCan pass through the upper electrode at b₀Direction increased geometric length 2 delta₀And (4) eliminating.

In the same way, the method for preparing the composite material, $O_{\mathrm{\&tau;}y}=\frac{2{\mathrm{mK\&epsiv;}}_0\&CenterDot;{\mathrm{\&epsiv;}}_r}{a_{0}G}{F}_y;$

according to O_τxAnd O_τyThe value of (c) calculates the direction of the tangential force.

2.4 selection of the principal materials and their characteristic parameters

Plate spacing d of parallel plate capacitor₀The inner spaces of the upper and lower substrates except for the copper foil electrodes were all PDMS (polydimethylsiloxane) super-elastic insulating media filled by a lost wax casting method, which was 0.1 mm. Its mechanical and physical parameters are Young's modulus E equal to 6.2MPa, shear elastic modulus G equal to 4.1MPa, and relative dielectric constant epsilon of medium polarization_γ2.5. Since E and G of the medium are much smaller than the elastic modulus E of copper_{Copper (Cu)}The deformation of the internal dielectric of the capacitor in a stress state is far larger than that of the polar plate because the internal dielectric of the capacitor is 103 GPa.

2.5 electrode lead design

Both the driving electrodes and the sensing electrodes need to be provided with lead-out lines, and considering that the respective driving electrodes are grounded in signal level, the driving electrodes need only share the same lead-out line. The driving electrodes of the ring capacitor unit group and the strip capacitor unit group are connected with a sensing system signal processor through an outgoing line, each ring independent lead of the ring capacitor unit group is connected with the sensing system signal processor, the sensing system signal processor calculates according to the output value free combination of each ring, then averaging is carried out to obtain the size of the tangential force and the size of the normal force, under the condition that the precision requirement is not high, the ring capacitor unit group can only select two optimal rings to lead out 2 leads, and d is obtained through the two rings_xAnd d_nSo as to obtain the magnitude of the tangential force and the magnitude of the normal force; the X-direction differential capacitance unit group and the Y-direction differential capacitance unit group are respectively led out through an outgoing line to be connected with the sensing system signal processor and used for calculating the direction of the tangential force. An intermediate converter is arranged between the sensing system signal processor and the capacitor unit and is used for setting the transmission coefficient of voltage or frequency to the capacitor. The entire capacitor assembly has at least 7 pins leading out from the side of the planar package so that the top and bottom outer surfaces of the entire assembly can be conveniently contacted with the measurement object.

The utility model discloses under the support of new material and new technology, accomplished the design of a novel three-dimensional force sensitive capacitor combination. At 10X 10mm²The stress surface can transmit the stress to the medium more uniformly in the normal direction or the tangential direction. In the contact of space force and sensor surface, the external force is only 1, and the normal direction F can be obtained by summing the capacitances_nInformation of (2), i.e. the whole electrode plate is aimed at F_nMake a contribution to obtain F_xAnd F_yThe three-dimensional force can be completely described, and the normal sensitivity, the tangential sensitivity and the maximum linear error of one-time conversion can be improved according to design parameters.

The capacitive pressure sensors are uniformly arranged between the substrate layer and the recovery foam layer in a matrix manner, the capacitive pole plates are connected with a sensor system signal processor through circuit leads, the sensor system signal processor comprises a multi-path signal high-speed switching circuit, an A/D conversion circuit and a control circuit, in order to save the A/D conversion circuit, the measurement of the multi-path pressure sensors is completed by one path of the A/D conversion circuit, the multi-path signal high-speed switching circuit and the control circuit are the design key of the system, and the switching speed influences the data volume tested in the short walking process. The utility model discloses an acquisition circuit carries out the signal switching to 256 way sensors simultaneously. After local shaping, a control system from the control circuit is switched in three stages, 32 8 switches are used for parallel work in the first stage, 32 signals are output, the 32 signals enter the second stage switch, 48 switches are adopted for parallel work to obtain 4 signals, and the 4 signals enter the third stage switch to obtain 1 signal and enter the A/D conversion circuit. The A/D conversion circuit reads data into the computer for temporary storage in the conversion process, and all the data are stored in the computer after being read.

In the actual use process, the pressure detection device is tiled on the ground, a tested person walks or stands still with normal gait on the pressure detection device, the measurement instrument collects three dynamic sole pressures and three static sole pressures respectively, the dynamic sole pressures and the three static sole pressures are compared with the sole pressure of a normal person, the respective average pressures of eight regions of the sole are analyzed through three tests, the heel, the arch, the 1 st metatarsal head, the 2 nd metatarsal head, the 3 rd to 5 th metatarsal head, the 1 st toe, the 2 nd toe and the 3 rd to 5 th toe are analyzed, and data of the sole pressure test provides reference basis for analyzing, diagnosing and establishing an expert assistant decision-making system and provides reference basis for clinical treatment effect evaluation. The present invention has been described above with reference to the accompanying drawings, and it is obvious that the present invention is not limited by the above-mentioned manner, and various insubstantial improvements can be made without modification to the method and technical solution of the present invention, or the present invention can be directly applied to other occasions without modification, all within the scope of the present invention. The protection scope of the present invention shall be subject to the protection scope defined by the claims.

Claims (10)

1. A plantar pressure distribution measuring device is characterized by comprising a plantar three-dimensional pressure measuring device body and a sensing system signal processor, wherein a plurality of capacitance pressure sensors for receiving plantar pressure information are arranged in the plantar three-dimensional pressure measuring device body, each capacitance pressure sensor comprises a circular ring capacitance unit group and a strip-shaped capacitance unit group, the strip-shaped capacitance unit groups are arranged at four corners of an outer base plate of the circular ring capacitance unit group, each circular ring capacitance unit group comprises more than two pairs of circular ring capacitance units, each circular ring capacitance unit pair comprises two circular ring capacitance units, each strip-shaped capacitance unit group comprises an X-direction differential capacitance unit group and a Y-direction differential capacitance unit group, each X-direction differential capacitance unit group and each Y-direction differential capacitance unit group respectively comprise more than two capacitance unit modules which mutually form a differential, and each capacitance unit module is of a comb-tooth-shaped structure consisting of more than two strip-shaped capacitance units, each ring capacitor unit and each strip capacitor unit respectively comprise a driving electrode of an upper polar plate and an induction electrode of a lower polar plate.

2. The plantar pressure distribution measuring device according to claim 1, wherein the plantar three-dimensional pressure measuring device body comprises a recovery foam layer, a sensor layer, a substrate layer made of an elastic material, a lead layer and a hard base plate from top to bottom, the recovery foam layer is made of polyurethane foam, organic silicon foam or modified organic silicon filled inorganic short fibers, leads of the lead layer are connected to a sensing system signal processor in a parallel or independent mode, the upper surface of the plantar three-dimensional pressure measuring device is rectangular, the width of the plantar three-dimensional pressure measuring device is 45 cm-1 m, and the length of the plantar three-dimensional pressure measuring device is 3 m-5 m.

3. The plantar pressure distribution measuring device according to claim 2, wherein the sensing electrode and the driving electrode of each circular ring capacitor unit are opposite and have the same shape, the driving electrode and the sensing electrode of each strip capacitor unit have the same width, the length of the driving electrode of each strip capacitor unit is greater than the length of the sensing electrode, and a left difference δ is reserved at each of two ends of the length of the driving electrode of each strip capacitor unit_{Left side of}And the right difference position delta_{Right side}，b_{0 drive}＝b_{Feeling of 0}+δ_{Right side}+δ_{Left side of}Wherein b is_{0 drive}Length of the driving electrode of the strip-shaped capacitor unit, b_{Feeling of 0}The length of the induction electrode of the strip-shaped capacitance unit.

4. The plantar pressure distribution measuring device according to claim 3, wherein the left difference δ of the strip-shaped capacitor unit_{Left side of}Right difference delta_{Right side}And is andwherein d is₀Is the thickness of the elastic medium, G is the shear modulus, τ, of the elastic medium_maxThe maximum stress value.

5. The plantar pressure distribution measuring device according to claim 2, characterized in that the driving electrodes and the sensing electrodes of the two groups of strip-shaped capacitive units forming a differential capacitive unit module with each other are provided with initial offset along the width direction, and the offset is the same in size and opposite in direction.

6. The plantar pressure distribution measuring device according to claim 2, wherein the circular ring capacitance unit group includes n concentric circular ring capacitance units, whereinWherein, a_{Flat plate}Length of parallel plate, r_{Round (T-shaped)}Is the width of the ring capacitor unit, a_{Delta circle}The electrode distance between two adjacent circular capacitor units.

7. The plantar pressure distribution measuring device according to claim 2, wherein the X-direction differential capacitance unit group and the Y-direction differential capacitance unit group each include m strip-shaped capacitance units, wherein, a_{Flat plate}Length of parallel plate, a_{Delta bar}Is the electrode spacing between two adjacent strip-shaped capacitor units, a₀The width of the strip-shaped capacitor unit.

8. The plantar pressure distribution measuring device according to claim 2, whereinIn the above, the width r of the concentric ring capacitor unit_{Round (T-shaped)}And the width a of the strip-shaped capacitor unit₀Equal; electrode spacing a of strip-shaped capacitor unit_{Delta bar}And the electrode spacing a of the circular ring capacitor unit_{Delta circle}Equal, width of the strip-shaped capacitor unitWherein d is₀E is the Young's modulus of the elastic medium, and G is the shear modulus of the elastic medium.

9. The plantar pressure distribution measuring device according to claim 2, wherein the driving electrodes of the circular ring capacitor unit groups and the strip capacitor unit groups are connected with a sensing system signal processor through a lead wire, the sensing electrode individual lead wire of each circular ring capacitor unit of the circular ring capacitor unit groups is connected with the sensing system signal processor, and the sensing electrodes of the capacitor unit modules of the X-direction differential capacitor unit groups and the Y-direction differential capacitor unit groups are respectively connected with the sensing system signal processor through a lead wire.

10. The plantar pressure distribution measuring device according to claim 2, characterized in that intermediate converters are respectively provided between the circular ring capacitance unit, the capacitance unit module and the sensor system signal processor, the intermediate converters are used for setting transmission coefficients of voltage to capacitance or frequency to capacitance, the sensor system signal processor comprises a multi-channel signal high-speed switching circuit, an A/D conversion circuit and a control circuit, the high-speed switching circuit comprises three stages of switching circuits, the output of the previous stage of switching circuit is the input signal of the next stage of switching circuit, and the last stage of switching circuit is sent to the control circuit through the A/D conversion circuit.