Non-contact moving object charge measurement method based on mutual capacitance matrix

Abstract

The invention discloses a non-contact moving object charge measurement method based on a mutual capacitance matrix, and belongs to the technical field of electrostatic detection. According to the invention, a physical model for charge measurement is constructed, a capacitance matrix is established by using a mirror image principle, a mutual capacitance value between a measured charged body and an induction electrode is solved by using a mirror image method, a circuit model for non-contact charge measurement is constructed, and the charge of the measured charged body is measured by using the model. Compared with a measurement method based on an electrometer, the non-contact type charge quantity measurement method has the advantages that the charge quantity of the to-be-measured charged body is not changed in the measurement process, repeated measurement is facilitated, and compared with an existing detection method based on an electric field sensor and the electric field change rate, a mathematical model for non-contact type charge quantity measurement is established; the corresponding relation between the charge quantity of the detected charged body and the amplitude of the electrostatic signal is accurately represented, and the method has a good application prospect in the field of electrostatic detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrostatic detection, and particularly relates to a non-contact charge measurement method for a moving object based on a mutual capacitance matrix. Background Art

[0002] Electrostatic detection helps to understand the situation of electrostatic charging during production and use, judge the danger of electrostatic discharge, and prevent electrostatic discharge accidents. The electric charge quantity is a basic physical quantity reflecting the electrified situation of an object, which determines the probability and danger of an electrified body causing electrostatic discharge. And the object to be measured is usually in a moving state. Accurately measuring the electric charge quantity of a moving object helps to improve the level of electrostatic detection and is conducive to preventing the occurrence of electrostatic discharge accidents.

[0003] Currently, there are three commonly used electrostatic detection methods for estimating the charged level of an object to be measured, namely, the detection method based on an electrometer, the detection method based on an electric field sensor, and the detection method based on the rate of change of an electric field.

[0004] An electrometer is an instrument for directly measuring the electric charge quantity of an object. However, this detection method measures the charge of the object to be measured by directly connecting the electrometer to the object to be measured or connecting it to a Faraday cylinder, and is not suitable for measuring the electric charge quantity of a moving object.

[0005] The detection method based on an electric field sensor directly measures the electric field intensity on the surface of an induction electrode, and the electric field intensity reflects the charged level of the object. When the relative positions of the object to be measured and the electric field sensor are determined, the greater the electric charge quantity of the object to be measured, the greater the measured electric field intensity. However, the measured value of the electric field sensor is the electric field intensity on the surface of the induction electrode and cannot quantitatively reflect the electric charge quantity of the object.

[0006] The detection method based on the rate of change of an electric field uses an electrostatic sensor to measure the ambient electric field. The electrostatic sensor mainly consists of an induction electrode and a conditioning circuit. The induction electrode generates an induced current in a changing electric field, and the induced current is converted into an electrostatic signal through the conditioning circuit. The electrostatic signal is positively correlated with the rate of change of the electric field. The electrostatic sensor has a simple structure and no moving mechanical components, and is suitable for working environments with vibration, shock or full of dust. They are widely used in the continuous monitoring of industrial processes and mechanical systems. Since there is no transient charge measurement model based on an electrostatic sensor, an accurate corresponding relationship between the amplitude of the electrostatic signal and the electric charge quantity of the charged body cannot be established, and the accurate measurement of the electric charge quantity of a moving object cannot be achieved. Summary of the Invention

[0007] The present invention aims to address the technical problems existing in the prior art, and provides a non-contact charge measurement method for a moving object based on a mutual capacitance matrix. A physical model for charge measurement is constructed, and a capacitance matrix is established using the mirror principle. The mutual capacitance value between the charged object to be measured and the induction electrode is obtained by using the mirror method. A circuit model for non-contact charge measurement is constructed, and the charge of the charged object to be measured is measured using this model. Compared with the measurement method based on an electrometer, the present invention has the advantage of being non-contact, and the amount of charge of the charged object to be measured remains unchanged during the measurement process, facilitating repeated measurement. Compared with the existing detection methods based on an electric field sensor and the rate of change of the electric field, a mathematical model for non-contact charge measurement is established, accurately representing the corresponding relationship between the amount of charge of the charged object to be measured and the amplitude of the electrostatic signal, and having good application prospects in the field of electrostatic detection.

[0008] The present invention provides a non-contact charge measurement method for a moving object based on a mutual capacitance matrix, comprising the following steps: Construct a physical model for charge measurement, where the physical model for charge measurement includes a charged object to be measured, an induction electrode in an electrostatic inductor, and the ground. The charged object to be measured and the induction electrode are respectively equivalent to a first conducting sphere and a second conducting sphere, and the ratio of the distance between the charged object to be measured and the induction electrode to the radius of the first conducting sphere is greater than a preset threshold; Construct a physical model for mirror charge measurement, and establish a capacitance matrix according to the capacitance to the ground of the first conducting sphere and the second conducting sphere, and the mutual capacitance value between the first conducting sphere and the second conducting sphere; Solve the capacitance matrix using the mirror method to obtain the mutual capacitance value between the first conducting sphere and the second conducting sphere; Construct the circuit model for non-contact charge measurement according to the capacitance to the ground of the first conducting sphere and the second conducting sphere, and the mutual capacitance value between the first conducting sphere and the second conducting sphere; Measure the charge of the moving charged object to be measured using the circuit model for non-contact charge measurement.

[0009] Preferably, the physical model for charge measurement includes a charged object to be measured, an induction electrode, and the ground, where the induction electrode is fixed, the charged object to be measured moves and passes by the induction electrode, the charged object to be measured and the induction electrode are respectively equivalent to a first conducting sphere and a second conducting sphere, and the ratio of the distance between the charged object to be measured and the induction electrode to the radius of the first conducting sphere is greater than a preset threshold; assume the radius of the first conducting sphere is , and the height from the ground is ; the radius of the second conducting sphere is , and the height from the ground is ; The ground is an infinitely large conducting plane with a potential of 0V. The horizontal distance between the center of the charged object under test and the center of the induction electrode is .

[0010] Preferably, constructing the physical model for mirror charge measurement specifically means that according to the mirror principle, the corresponding conducting spheres are mirrored at the mirror image positions of the first conducting sphere and the second conducting sphere in the physical model of the charge measurement with respect to the ground.

[0011] Preferably, constructing the physical model for mirror charge measurement, establishing the capacitance matrix according to the capacitance to ground of the first conducting sphere and the second conducting sphere and the mutual capacitance value between the first conducting sphere and the second conducting sphere specifically includes: Let the electric charge quantity of the first conducting sphere be and the electric charge quantity of the second conducting sphere be . According to the superposition principle, the following relationship exists between the surface potential and the electric charge quantity of the conductor: (1) Wherein, is the surface potential of the first conducting sphere, is the surface potential of the second conducting sphere, , , , are all potential coefficients; Select the ground as the potential reference point, that is, . Replace the influence of the ground on the electrostatic field with mirror charges to obtain: (2) Wherein, is the vacuum permittivity, is the relative permittivity of air; Record Equation (2) in matrix form , wherein, is the potential matrix, is the potential coefficient matrix, is the charge matrix, and obtain: (3) Express the charge in terms of the function of the potential to obtain: (4) (5) In the formula, is the electrostatic induction coefficient, that is: (6) Obtain the capacitance matrix as follows: (7) Among them, is the capacitance to ground of the first conductor sphere, is the capacitance to ground of the second conductor sphere, is the mutual capacitance between the first conductor sphere and the second conductor sphere.

[0012] Preferably, the mirror image method is used to solve the capacitance matrix to obtain the mutual capacitance value between the first conductor sphere and the second conductor sphere.

[0013] Preferably, the circuit model of the non-contact charge measurement is specifically that the capacitance to ground of the first conductor sphere is connected in series between the first conductor sphere and the ground, the mutual capacitance value between the first conductor sphere and the second conductor sphere is connected in series between the first conductor sphere and the second conductor sphere, and the capacitance to ground of the second conductor sphere is connected in series between the second conductor sphere and the ground.

[0014] Preferably, when the charged object to be measured moves, the induced charge amount on the induction electrode changes, causing an induced current. The induced current is input into the conditioning circuit to be converted into an electrostatic signal to estimate the charge amount of the charged object to be measured. The induction electrode is connected to the electrostatic inductor, and the electrostatic inductor further includes a conditioning circuit, and the conditioning circuit can convert the induced current into an electrostatic signal.

[0015] Preferably, the charge measurement of the moving charged object to be measured using the circuit model of the non-contact charge measurement specifically includes: Connect the induction electrode to the conditioning circuit and set the potential of the induction electrode to 0, then is in parallel with ; Suppose the charge amount of the currently measured charged object is . Due to the electrostatic induction phenomenon, the induction electrode and the ground will carry opposite induced charges. When electrostatic equilibrium is reached, the induced charge amount on the induction electrode is: (8) The induced charge amount on the induction electrode changes with the movement of the charged object to be measured. Differentiating the induced charge amount with respect to time gives the induced current : (9) During the measurement process, the charge amount of the charged object to be measured remains unchanged; the conditioning circuit of the electrostatic sensor converts the induced current into an electrostatic signal ; (10) Among them, A is the transimpedance gain of the conditioning circuit; By arranging Formulas (9) and (10), the mathematical model of the electric charge of the charged object to be measured is shown as follows: (11).

[0016] Compared with the prior art, the present invention has the following beneficial effects: A physical model for charge measurement is constructed, and the capacitance matrix is established by using the mirror principle. The mutual capacitance value between the charged object to be measured and the induction electrode is obtained by using the mirror method. A non-contact charge measurement circuit model is constructed, and the model is used to measure the charge of the charged object to be measured. Compared with the measurement method based on an electrometer, the present invention has the advantage of being non-contact. During the measurement process, the electric charge of the charged object to be measured remains unchanged, which is convenient for repeated measurement. Compared with the existing detection methods based on electric field sensors and the rate of change of the electric field, a mathematical model for non-contact electric charge measurement is established, which accurately represents the corresponding relationship between the electric charge of the charged object to be measured and the amplitude of the electrostatic signal, and has good application prospects in the field of electrostatic detection. Description of the Drawings

[0017] Figure 1 It is a flowchart of a non-contact charge measurement method for a moving object based on a mutual capacitance matrix according to an embodiment of the present invention. Detailed Embodiments

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] As Figure 1 shown, the present invention provides a non-contact charge measurement method for a moving object based on a mutual capacitance matrix, including the following steps: Construct a physical model for charge measurement. The physical model for charge measurement includes a charged object to be measured, an induction electrode in an electrostatic inductor, and the ground. The charged object to be measured and the induction electrode are respectively equivalent to a first conductor sphere and a second conductor sphere. The ratio of the distance between the charged object to be measured and the induction electrode to the radius of the first conductor sphere is greater than a preset threshold; the preset threshold should make the distance between the charged object to be measured and the induction electrode much greater than the radius of the first conductor sphere; Construct a physical model for mirror charge measurement, and establish a capacitance matrix according to the capacitance to the ground of the first conductor sphere and the second conductor sphere and the mutual capacitance value between the first conductor sphere and the second conductor sphere; The capacitance matrix is solved by the mirror image method to obtain the mutual capacitance value between the first conductor sphere and the second conductor sphere; According to the capacitances to the ground of the first conductor sphere and the second conductor sphere and the mutual capacitance value between the first conductor sphere and the second conductor sphere, a circuit model for the non-contact charge measurement is constructed; The circuit model for the non-contact charge measurement is used to measure the charge of a moving charged object to be measured.

[0020] According to a specific implementation of the present invention, the physical model of the charge measurement includes a charged object to be measured, an induction electrode, and the ground. Among them, the induction electrode is fixed, the charged object to be measured moves and passes through the induction electrode. The charged object to be measured and the induction electrode are respectively equivalent to a first conductor sphere and a second conductor sphere. The ratio of the distance between the charged object to be measured and the induction electrode to the radius of the first conductor sphere is greater than a preset threshold; assume that the radius of the first conductor sphere is and the height from the ground is ; the radius of the second conductor sphere is and the height from the ground is ; the ground is an infinite conducting plane with a potential of 0V, and the horizontal distance between the center of the charged object to be measured and the center of the induction electrode is .

[0021] According to a specific implementation of the present invention, constructing the physical model of the mirror image charge measurement specifically means mirroring the corresponding conductor spheres at the mirror image positions of the first conductor sphere and the second conductor sphere in the physical model of the charge measurement with respect to the ground according to the mirror image principle.

[0022] According to a specific implementation of the present invention, constructing the physical model of the mirror image charge measurement and establishing a capacitance matrix according to the capacitances to the ground of the first conductor sphere and the second conductor sphere and the mutual capacitance value between the first conductor sphere and the second conductor sphere specifically includes: Let the charge amount of the first conductor sphere be and the charge amount of the second conductor sphere be . According to the superposition principle, the following relationship exists between the surface potential and the charge amount of the conductor: (1) where is the surface potential of the first conductor sphere, is the surface potential of the second conductor sphere, , , , are all potential coefficients; Select the ground as the potential reference point, that is , and replace the influence of the ground on the electrostatic field with mirror image charges to obtain: (2) Among them, is the vacuum permittivity, is the relative permittivity of air; Record Equation (2) in matrix form wherein, is the potential matrix, is the potential coefficient matrix, is the charge matrix, and we get: (3) Express the charge in terms of a function of the potential, and we get: (4) (5) In the formula, is the electrostatic induction coefficient, that is: (6) The capacitance matrix is obtained as follows: (7) wherein, is the capacitance to ground of the first conductor sphere, is the capacitance to ground of the second conductor sphere, is the mutual capacitance between the first conductor sphere and the second conductor sphere.

[0023] According to a specific embodiment of the present invention, the mirror method is used to solve the capacitance matrix to obtain the mutual capacitance value between the first conductor sphere and the second conductor sphere.

[0024] According to a specific embodiment of the present invention, the circuit model of the non-contact charge measurement is specifically to connect the capacitance to ground of the first conductor sphere in series between the first conductor sphere and the ground, connect the mutual capacitance value between the first conductor sphere and the second conductor sphere in series between the first conductor sphere and the second conductor sphere, and connect the capacitance to ground of the second conductor sphere in series between the second conductor sphere and the ground.

[0025] According to a specific embodiment of the present invention, when the movement of the charged object to be measured causes a change in the induced charge amount on the induction electrode, an induced current is generated. The induced current is input into a conditioning circuit to be converted into an electrostatic signal, and the charge amount of the charged object to be measured is estimated. The induction electrode is connected to the electrostatic inductor, and the electrostatic inductor further includes a conditioning circuit, and the conditioning circuit can convert the induced current into an electrostatic signal.

[0026] According to a specific embodiment of the present invention, the charge measurement of the moving charged object to be measured using the circuit model of the non-contact charge measurement specifically includes: Connect the induction electrode to the conditioning circuit and set the potential of the induction electrode to 0, then And In parallel; Let the charge quantity of the currently measured charged object be , due to the electrostatic induction phenomenon, the induction electrode and the ground will carry opposite induced charges. When electrostatic equilibrium is reached, the induced charge quantity on the induction electrode is: (8) The induced charge quantity on the induction electrode changes with the movement of the charged object to be measured. Differentiate the induced charge quantity with respect to time to obtain the induced current : (9) During the measurement process, the charge quantity of the charged object to be measured remains unchanged; the conditioning circuit of the electrostatic sensor converts the induced current into an electrostatic signal ; (10) Wherein, A is the transimpedance gain of the conditioning circuit; Arrange formulas (9) and (10) to obtain the mathematical model of the charge quantity of the charged object to be measured as shown in the following formula: (11).

[0027] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are all included within the protection scope of the present invention.

Claims

1. A non-contact moving object charge measurement method based on mutual capacitance matrix, characterized in that: The steps include: Constructing a physical model of charge measurement, wherein the physical model of charge measurement includes a charged object to be measured, an induction electrode in an electrostatic inductor, and a ground, wherein the charged object to be measured and the induction electrode are respectively equivalent to a first conductor sphere and a second conductor sphere, and a ratio of a distance between the charged object to be measured and the induction electrode to a radius of the first conductor sphere is greater than a preset threshold; Constructing a physical model of image charge measurement, and establishing a capacitance matrix according to the ground capacitance of the first conductor sphere and the second conductor sphere and the mutual capacitance between the first conductor sphere and the second conductor sphere; Solving the capacitance matrix using the mirror method to obtain the mutual capacitance value between the first conductor sphere and the second conductor sphere; Constructing a circuit model for contactless charge measurement according to the ground capacitance of the first conductor sphere and the second conductor sphere and the mutual capacitance between the first conductor sphere and the second conductor sphere; The circuit model of the non-contact charge measurement is used to measure the charge of a moving charged object.

2. The non-contact moving object charge measurement method based on mutual capacitance matrix according to claim 1 is characterized in that: The physical model of charge measurement includes a charged body to be measured, an induction electrode and the ground, wherein the induction electrode is fixed, the charged body to be measured moves and passes through the induction electrode, the charged body to be measured and the induction electrode are equivalent to a first conductor sphere and a second conductor sphere respectively, and the ratio of the distance between the charged body to be measured and the induction electrode to the radius of the first conductor sphere is greater than a preset threshold; assuming that the radius of the first conductor sphere is , height from ground is ; The radius of the second conductor sphere is , height from ground is ; The ground is an infinite conductor plane with an electric potential of 0V. The horizontal distance between the center of the charged body being measured and the center of the sensing electrode is .

3. The non-contact moving object charge measurement method based on mutual capacitance matrix according to claim 2 is characterized in that: The physical model of the mirror image charge measurement is constructed specifically by mirroring the mirror positions of the first conductor sphere and the second conductor sphere in the physical model of the charge measurement relative to the ground to obtain corresponding conductor spheres according to the mirror image principle.

4. The non-contact moving object charge measurement method based on mutual capacitance matrix according to claim 3 is characterized in that: Constructing a physical model for image charge measurement, and establishing a capacitance matrix according to the ground capacitance of the first conductor sphere and the second conductor sphere and the mutual capacitance between the first conductor sphere and the second conductor sphere specifically includes: Assume that the charge of the first conductor sphere is , the charge of the second conductor sphere is According to the superposition principle, the following relationship exists between the surface potential and charge of a conductor: (1) in, is the surface potential of the first conductor sphere, is the surface potential of the second conductor sphere, , , , All are potential coefficients; The ground is selected as the potential reference point, that is, , replace the effect of the ground on the electrostatic field with the image charge, and we get: (2) in, is the dielectric constant of vacuum, is the relative dielectric constant of air; Write equation (2) in matrix form ,in, is the potential matrix, is the potential coefficient matrix, As the charge matrix, we get: (3) Expressing the charge as a function of the potential, we obtain: (4) (5) In the formula, is the electrostatic induction coefficient, that is: (6) The capacitance matrix is ​​as follows: (7) in, is the capacitance of the first conductor sphere to ground, is the capacitance of the second conductor sphere to ground, is the mutual capacitance between the first conductive sphere and the second conductive sphere.

5. The non-contact moving object charge measurement method based on mutual capacitance matrix according to claim 4 is characterized in that: The capacitance matrix is ​​solved by using the mirror method to obtain the mutual capacitance value between the first conductive sphere and the second conductive sphere.

6. The non-contact moving object charge measurement method based on mutual capacitance matrix according to any one of claims 1 to 5, characterized in that: The circuit model of the contactless charge measurement is specifically as follows: the capacitance of the first conductor sphere to the ground is connected in series between the first conductor sphere and the ground, the mutual capacitance between the first conductor sphere and the second conductor sphere is connected in series between the first conductor sphere and the second conductor sphere, and the capacitance of the second conductor sphere to the ground is connected in series between the second conductor sphere and the ground.

7. The non-contact moving object charge measurement method based on mutual capacitance matrix according to claim 1, characterized in that: The charge measurement of the moving charged body under test using the circuit model of the contactless charge measurement is specifically performed as follows: when the charged body under test moves, the amount of induced charge on the induction electrode changes, causing an induced current, and the induced current is input into a conditioning circuit to be converted into an electrostatic signal, and the charge of the charged body under test is estimated. The induction electrode is connected to the electrostatic sensor, and the electrostatic sensor also includes a conditioning circuit, and the conditioning circuit can convert the induced current into an electrostatic signal.

8. The non-contact moving object charge measurement method based on mutual capacitance matrix according to claim 7, characterized in that: The method of measuring the charge of a moving charged object by using the circuit model of the non-contact charge measurement specifically includes: Connect the sensing electrode to the conditioning circuit and set the potential of the sensing electrode to 0. and in parallel; Assume that the current charge of the charged body being measured is Due to the electrostatic induction phenomenon, the induction electrode and the ground will carry different induced charges. When the electrostatic balance is reached, the amount of induced charge on the induction electrode is for: (8) The induced charge on the sensing electrode changes with the movement of the charged body being measured, and the induced current is obtained by differentiating the induced charge with respect to time. : (9) During the measurement process, the charge of the charged body is remain unchanged; the conditioning circuit of the electrostatic sensor converts the induced current Converted into static signal ; (10) in, A is the transimpedance gain of the conditioning circuit; Arranging formulas (9) and (10) to obtain the mathematical model of the charge of the charged body under test is as follows: （11）。

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