Skin pressure measuring system and method based on human body surface capacitance

Abstract

The invention relates to the technical field of pressure sensors, in particular to a skin pressure measuring system and method based on human body surface capacitance, the system comprises a metal electrode, the metal electrode serves as a contact surface with the skin, and the pressure is measured by measuring the contact capacitance of the metal electrode and the skin, and the metal electrode is used for enabling the pressure and the contact area to be in a mapping increasing relationship. According to the flexible strain unit, human skin is adopted, and capacitance is changed by changing the contact area with an electrode through pressure to serve as a strain unit.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensors, and in particular to a skin pressure measurement system and method based on human body surface capacitance. Background Art

[0002] Hand pressure sensing technology relies on core principles such as flexible electronics, magnetic induction, and the piezoelectric effect. Through high sensitivity, real-time monitoring, and flexible wearable features, it achieves precise perception of pressure distribution. It can be used in medical rehabilitation to improve patient muscle strength assessment and tactile feedback accuracy, in industrial robotics to test gripping safety, and in VR / AR scenarios to optimize immersive interactive experiences. It also provides data support for smart homes and human-computer interaction, driving intelligent service upgrades. However, current pressure sensor test circuits are complex, and flexible sensitive units present challenges in balancing service life and manufacturing cost. To address this issue, the present invention provides a skin pressure measurement system and method based on human surface capacitance. Summary of the Invention

[0003] The purpose of the present invention is to provide a skin pressure measurement system and method based on human body surface capacitance. The flexible strain unit uses human skin, and the capacitance is changed by changing the pressure and the contact area of the electrode as the strain unit.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A skin pressure measurement system based on human body surface capacitance includes: a metal electrode, which serves as a contact surface with the skin. Pressure is measured by measuring the contact capacitance between the metal electrode and the skin, wherein the metal electrode is used to make the pressure and contact area increase in a mapped relationship.

[0006] Optionally, measuring the contact capacitance between the metal electrode and the skin includes: obtaining a measurement capacitance matrix by a self-capacitance measurement method, wherein the self-capacitance measurement method uses an electrode that is in contact with the skin and is not subject to external pressure as a ground electrode;

[0007] Obtaining a mutual capacitance matrix according to a mutual capacitance measurement method, wherein a measurement frequency of the self-capacitance measurement method and the mutual capacitance measurement method is 1 kHz to 2 MHz;

[0008] Subtracting the mutual capacitance matrix from the measured capacitance matrix to obtain a capacitance true value matrix after removing the mutual capacitance;

[0009] The contact capacitance is obtained according to the capacitance truth matrix after removing the mutual capacitance.

[0010] Optionally, the mutual capacitance matrix C M for:

[0011] ;

[0012] The measured capacitance matrix C T for:

[0013] ;

[0014] The capacitance truth matrix C after removing the mutual capacitance R for:

[0015] ;

[0016] Among them, C1~C j is the capacitance value measured by j sensors, C M1j For capacitance sensor C1 and capacitance sensor C j The mutual capacitance parameters between them.

[0017] Optionally, the mutual capacitance matrix is obtained by pressing each of the metal electrodes individually or iteratively obtaining the mutual capacitance matrix using a least square method according to the measured capacitance values.

[0018] Optionally, the relationship between pressure and contact area increasing in a mapped manner includes:

[0019] F=F MAX *( C'-C0) / ( C MAX -C0) or F=f(ΔC);

[0020] Where F is the applied pressure, F MAX is the maximum pressure, C0 is the capacitance value at the initial touch, C' is the capacitance value after pressure is applied, and C MAX is the maximum capacitance, ΔC is the capacitance change, and f is the function between the applied pressure and the capacitance change.

[0021] Optionally, measuring pressure by measuring the contact capacitance between the metal electrode and the skin includes: connecting the metal electrodes located in the same row or column in parallel, obtaining the sum of the capacitances in the same row or column as the contact capacitance through row and column scanning, and obtaining the pressure.

[0022] The present invention also provides a method for measuring skin pressure based on human body surface capacitance, comprising:

[0023] Pressing a metal electrode against the surface of human skin to measure the contact capacitance between the metal electrode and the skin;

[0024] The skin pressure is obtained according to the contact capacitance.

[0025] Optionally, measuring the contact capacitance between the metal electrode and the skin includes: obtaining a measurement capacitance matrix by a self-capacitance measurement method, wherein the self-capacitance measurement method uses an electrode that is in contact with the skin and is not subject to external pressure as a ground electrode;

[0026] Obtaining a mutual capacitance matrix according to a mutual capacitance measurement method, wherein a measurement frequency of the self-capacitance measurement method and the mutual capacitance measurement method is 1 kHz to 2 MHz;

[0027] Subtracting the mutual capacitance matrix from the measured capacitance matrix to obtain a capacitance true value matrix after removing the mutual capacitance;

[0028] The contact capacitance is obtained according to the capacitance truth matrix after removing the mutual capacitance.

[0029] Optionally, the mutual capacitance matrix is obtained by pressing each of the metal electrodes individually or iteratively obtaining the mutual capacitance matrix using a least square method according to the measured capacitance values.

[0030] Optionally, measuring pressure by measuring the contact capacitance between the metal electrode and the skin includes: connecting metal electrodes located in the same row or column in parallel, obtaining the sum of the capacitances in the same row or column as the contact capacitance through row and column scanning, and obtaining the pressure.

[0031] The beneficial effects of the present invention are as follows: the method of the present invention utilizes simple metal electrodes and skin to form a sensor unit, detects changes in surface capacitance of human skin, and confirms the degree of pressure based on the obtained data, which is used to judge the gripping posture and as a basis for the degree of force exerted. While saving costs, it increases the life of the pressure sensor and reduces the difficulty of arranging multiple pressure sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 Schematic diagram of a capacitance test circuit according to an embodiment of the present invention;

[0034] Figure 2 Schematic diagram of a skin pressure measurement system based on human body surface capacitance according to an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of measuring self-capacitance according to an embodiment of the present invention;

[0036] Figure 4 FIG. 1 is a schematic diagram of combining multiple pressure sensors into a tactile sensor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1:

[0040] This embodiment provides a skin pressure measurement system based on human body surface capacitance, including: a metal electrode, the metal electrode serving as a contact surface with the skin, and measuring pressure by measuring the contact capacitance between the metal electrode and the skin, wherein the metal electrode is used to cause pressure and contact area to increase in a mapped relationship.

[0041] Specifically, a sensor unit is formed by using a simple flexible substrate (such as TPU, which only serves as a mechanical support and does not participate in the test circuit), a metal electrode (such as copper foil) and human skin to detect the pressure on the skin surface of the hand or foot, for example, wherein the metal electrode is provided on the substrate. The capacitance test circuit of this embodiment is as follows Figure 1 As shown, the test interface is connected to the sensor end of the skin, the ground electrode is connected to the end of the skin without pressure, and the sensor end is connected to the ground electrode through the skin's own conductivity; the system composition diagram is shown in Figure 2 As shown, the TPU deforms during pressure, increasing the contact area. This in turn increases the capacitance between the skin and the metal electrode, which can be measured to indicate the degree of pressure. The flexible substrate used here can be eliminated, and by shaping the metal itself into a specific shape, the skin flexes during contact, naturally increasing the contact area.

[0042] Furthermore, measuring the contact capacitance between the metal electrode and the skin includes: obtaining a measurement capacitance matrix through a self-capacitance measurement method, wherein the self-capacitance measurement method uses an electrode that is in contact with the skin and is not subject to external pressure as a ground electrode; obtaining a mutual capacitance matrix according to a mutual capacitance measurement method, wherein the measurement frequency of the self-capacitance measurement method and the mutual capacitance measurement method is 1kHz~2MHz; removing the mutual capacitance matrix from the measurement capacitance matrix to obtain a capacitance true value matrix after removing the mutual capacitance; and obtaining the contact capacitance based on the capacitance true value matrix after removing the mutual capacitance.

[0043] Specifically, there are two methods for measuring capacitance: self-capacitance (needs to be grounded) and mutual capacitance. This solution is compatible with both methods. Self-capacitance uses an electrode (such as the wrist) that is in long-term contact with the skin and is not subject to external pressure as the ground electrode. The ground electrode is connected to the GND port of the capacitance test chip through a lead, and the metal electrode is connected to the test port of the capacitance test chip through a lead. The principle is as follows Figure 3 As shown:

[0044] This connection method can be compatible with a large number of metal electrodes while using a single ground electrode, saving test interfaces and simplifying the overall circuit design. The disadvantage is that there is mutual capacitance between different metal electrodes, and the interference of mutual capacitance needs to be eliminated through testing in subsequent processes.

[0045] In addition, multiple pressure sensors can be combined to form a tactile sensor, such as Figure 4 As shown, capacitor C11 is simultaneously connected to the same vertical column circuit S1 and row column H1, and so on for each metal electrode. At this time, the circuit quickly detects the capacitance of S1-S3 and H1-H3. The capacitance of S1 is the sum of the capacitances of C11, C21, and C31. The capacitance of H1 is the sum of C11, C12, and C13. In practical applications, the corresponding pressure distribution can be generated according to the degree of change of the values of the vertical columns and rows, and then the corresponding lateral force and tangential force distribution can be generated according to the position distribution of each point.

[0046] Furthermore, the mutual capacitance matrix C M for:

[0047] ;

[0048] The measured capacitance matrix C T for:

[0049] ;

[0050] The capacitance truth matrix C after removing the mutual capacitance R for:

[0051] ;

[0052] Among them, C1~C j is the capacitance value measured by j sensors, C M1j For capacitance sensor C1 and capacitance sensor C j The mutual capacitance parameters between them.

[0053] Specifically, when multiple metal electrodes are arranged and tested using self-capacitance, mutual capacitance may exist between the electrodes, which can easily interfere with the test results. Traditional chip mutual capacitance deduction methods generally treat mutual capacitance as a constant value.

[0054] C can be obtained by pressing each metal electrode individually M The value of C M The constant characteristic of the capacitor is used to calculate the capacitance of C using the least square method. M Iterate, where C M Corresponding parameters in the matrix The iterative formula is:

[0055] ;

[0056] Where i is the number of iterations, C q,t is the measured value of capacitance q in the tth measurement, C k,t is the measured value of capacitance k in the t-th measurement, is the true value of capacitance q after deducting mutual capacitance at the t-1th iteration, is the true value of capacitance k after deducting mutual capacitance at the t-1th iteration, q, k are natural numbers between 1-j and q<k.

[0057] Furthermore, the linear relationship between pressure and contact area includes:

[0058] F=F MAX *(C'-C0) / ( C MAX -C0);

[0059] Where F is the applied pressure, F MAX is the maximum pressure, C0 is the capacitance at the initial touch, C' is the capacitance after pressure is applied, and C MAX is the maximum capacitance.

[0060] Furthermore, the mapping relationship between pressure and contact area includes:

[0061] F=f(ΔC);

[0062] Where F is the applied pressure and ΔC is the change in capacitance.

[0063] Specifically, the pressure collection method during the working process is as follows: First, the initial state is divided into two cases, one is that the metal electrode is not in contact with the skin, and the other is that the metal electrode is in contact with the skin.

[0064] Taking the initial state where the metal electrode and the skin are not in contact as an example, the initial capacitance value is 0. The capacitance value at the initial touch is C0. After the pressure F is applied, the contact area between the skin and the metal electrode increases due to the pressure, and the capacitance value rises to C'. The pressure is continued to be applied to the maximum pressure F. MAX , then the capacitance value rises to C MAXIf the increase in contact area between the skin and the metal electrode caused by pressure is proportional to the pressure, then the change in capacitance and force F satisfy a linear relationship:

[0065] F=F MAX *(C'-C0) / ( C MAX -C0);

[0066] If the initial state is contact, the capacitance value at the initial touch is C0, and the rest can be deduced similarly. It should be noted that since the electrical properties of each person's skin are different, the capacitance value is a value that depends on the process sampling. If the initial measured pressure is a known standard pressure, the specific pressure value can be calculated based on the measured capacitance value. Otherwise, it is more of a value that reflects the degree of pressure during the test. During the process, C Max It may be refreshed continuously. For convenience, you can do an initial sampling at the beginning and get an initial approximate value by making a fist or pressing the metal electrode hard. Max It can also be dynamically updated by recording sensor data in the subsequent process. In addition, if the increase in the contact area between the skin and the metal electrode caused by pressure is not proportional to the pressure, the change in capacitance value and force F are a point-to-point mapping relationship:

[0067] F=f(ΔC);

[0068] The specific mapping relationship formula can be used to make assumptions based on the deep learning model and data in the future to obtain the optimal result.

[0069] Furthermore, measuring pressure by measuring the contact capacitance between the metal electrode and the skin includes: connecting the metal electrodes in the same row or column in parallel, obtaining the sum of the capacitances in the same row or column as the contact capacitance by row and column scanning, and obtaining pressure.

[0070] Example 2:

[0071] A method for measuring skin pressure based on human body surface capacitance implemented by the system provided in embodiment 1 includes:

[0072] By pressing the metal electrode on the surface of human skin, the contact capacitance between the metal electrode and the skin is measured;

[0073] Based on the contact capacitance, the skin pressure is obtained.

[0074] Furthermore, measuring the contact capacitance between the metal electrode and the skin includes: obtaining a measurement capacitance matrix by a self-capacitance measurement method, wherein the self-capacitance measurement method uses an electrode that is in contact with the skin and is not subject to external pressure as a ground electrode;

[0075] Obtain a mutual capacitance matrix according to the mutual capacitance measurement method, wherein the measurement frequency of the self-capacitance measurement method and the mutual capacitance measurement method is 1 kHz to 2 MHz;

[0076] The mutual capacitance matrix is removed from the measured capacitance matrix to obtain a capacitance true value matrix after removing the mutual capacitance;

[0077] The contact capacitance is obtained based on the capacitance truth matrix after removing the mutual capacitance.

[0078] Furthermore, the mutual capacitance matrix is obtained by pressing each metal electrode individually or iteratively obtaining it by using the least square method according to the measured capacitance values.

[0079] The mutual capacitance matrix parameters obtained by iteratively fitting using the least squares method include:

[0080] ;

[0081] Where i is the number of iterations, C q,t is the measured value of capacitance q in the tth measurement, C k,t is the measured value of capacitance k in the t-th measurement, is the true value of capacitance q after deducting mutual capacitance at the t-1th iteration, is the true value of capacitance k after deducting mutual capacitance at the t-1th iteration, q,k is a natural number between 1-j and q<k.

[0082] Furthermore, measuring pressure by measuring the contact capacitance between the metal electrode and the skin includes: connecting the metal electrodes in the same row or column in parallel, obtaining the sum of the capacitances in the same row or column as the contact capacitance by row and column scanning, and obtaining pressure.

[0083] For a tactile sensor using row and column scanning (which measures the pressure at each point and converts it into lateral force and tangential force), the following is how to convert the 3X3 pressure signal into lateral force F normal and tangential force F friction Method:

[0084] ;

[0085] ;

[0086] Among them, a and b respectively indicate that the sensor is located in the ath row and the bth column, F ab Indicates the pressure on row a and column b. It represents the unit area of row a, column b and the angular size of the force.

[0087] Capacitance test method used: RC capacitance coupling method, which determines the capacitance by measuring the frequency. The response signal frequency used should be as low as possible, ranging from 1k to 2MHz.

[0088] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A skin pressure measurement system based on human body surface capacitance, characterized in that: include: A metal electrode serves as a contact surface with the skin, and pressure is measured by measuring the contact capacitance between the metal electrode and the skin, wherein the metal electrode is used to make the pressure and the contact area increase in a mapped relationship.

2. The skin pressure measurement system based on human body surface capacitance according to claim 1, characterized in that: Measuring the contact capacitance between the metal electrode and the skin includes: obtaining a measurement capacitance matrix by a self-capacitance measurement method, wherein the self-capacitance measurement method uses an electrode that is in contact with the skin and is not subject to external pressure as a ground electrode; Obtaining a mutual capacitance matrix according to a mutual capacitance measurement method, wherein a measurement frequency of the self-capacitance measurement method and the mutual capacitance measurement method is 1 kHz to 2 MHz; Subtracting the mutual capacitance matrix from the measured capacitance matrix to obtain a capacitance true value matrix after removing the mutual capacitance; The contact capacitance is obtained according to the capacitance truth matrix after removing the mutual capacitance.

3. The skin pressure measurement system based on human body surface capacitance according to claim 2, characterized in that: The mutual capacitance matrix C M for: ； The measured capacitance matrix C T for: ； The capacitance truth matrix C after removing the mutual capacitance R for: ； Among them, C1~C j is the capacitance value measured by j sensors, C M1j For capacitance sensor C1 and capacitance sensor C j The mutual capacitance parameters between them.

4. The skin pressure measurement system based on human body surface capacitance according to claim 3, characterized in that: The mutual capacitance matrix is obtained by pressing each of the metal electrodes individually or iteratively using the least square method according to the measured capacitance values.

5. The skin pressure measurement system based on human body surface capacitance according to claim 1, characterized in that: The relationship between pressure and contact area increases in a mapped manner includes: F=F MAX *( C'-C0) / ( C MAX -C0) or F=f(ΔC); Where F is the applied pressure, F MAX is the maximum pressure, C0 is the capacitance value at the initial touch, C' is the capacitance value after pressure is applied, and C MAX is the maximum capacitance, ΔC is the capacitance change, and f is the function between the applied pressure and the capacitance change.

6. The skin pressure measurement system based on human body surface capacitance according to claim 1, characterized in that: Measuring pressure by measuring the contact capacitance between the metal electrode and the skin includes: connecting the metal electrodes located in the same row or column in parallel, obtaining the sum of the capacitances in the same row or column as the contact capacitance by row-column scanning, and obtaining the pressure.

7. The method for measuring skin pressure based on human body surface capacitance implemented by the system according to any one of claims 1 to 6, characterized in that: include: Pressing a metal electrode against the surface of human skin to measure the contact capacitance between the metal electrode and the skin; The skin pressure is obtained according to the contact capacitance.

8. The method for measuring skin pressure based on human body surface capacitance according to claim 7, characterized in that: The measuring of the contact capacitance between the metal electrode and the skin comprises: obtaining a measurement capacitance matrix by a self-capacitance measurement method, wherein the self-capacitance measurement method uses an electrode that is in contact with the skin and is not subject to external pressure as a ground electrode; Obtaining a mutual capacitance matrix according to a mutual capacitance measurement method, wherein a measurement frequency of the self-capacitance measurement method and the mutual capacitance measurement method is 1 kHz to 2 MHz; Subtracting the mutual capacitance matrix from the measured capacitance matrix to obtain a capacitance true value matrix after removing the mutual capacitance; The contact capacitance is obtained according to the capacitance truth matrix after removing the mutual capacitance.

9. The method for measuring skin pressure based on human body surface capacitance according to claim 7, characterized in that: The mutual capacitance matrix is obtained by pressing each of the metal electrodes individually or iteratively using the least square method according to the measured capacitance values.

10. The pressure measurement method based on human skin surface capacitance according to claim 7, characterized in that: Measuring pressure by measuring the contact capacitance between the metal electrode and the skin includes: connecting the metal electrodes in the same row or column in parallel, obtaining the sum of the capacitances in the same row or column as the contact capacitance by row-column scanning, and obtaining the pressure.

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