A novel device and method for detecting equivalent inductance

Abstract

The present invention relates to the technical field of sensors, and specifically to a novel device and method for detecting equivalent inductance. An induction coil is connected to a detection device, which includes a drive circuit and a time window detection circuit. The drive circuit is connected to a start trigger and a stop trigger. The start trigger and the stop trigger are connected to a counter, and the counter is connected to a high-precision clock. A capacitor discharges to the induction coil, triggering the time window detection circuit. The start trigger causes the counter to count. When the drive circuit detects that the current change rate input to the induction coil is 0 or the discharge reaches a certain scale, it triggers the stop trigger to work, and the stop trigger triggers the counter to stop counting. Compared with the prior art, the detection device composed of a signal drive circuit and a time window detection circuit detects the equivalent inductance value of a metal displacement sensor, and only one oscillation period is required to complete the detection. The fixed bias magnetic field and the uniformly changing magnetic field do not interfere with the detection circuit, and the anti-temperature drift property is stronger.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and specifically to a novel device and method for detecting equivalent inductance. Background Art

[0002] An angular position sensor can detect the rotational angular displacement of a detected target. Angular position sensors are mainly used in flow meters, industrial machine tools, and the robotics industry. Among them, metal displacement sensors are mainly applied in the industrial machine tool, robotics, and industrial Internet of Things industries. Currently, grating is the main type of angular displacement and displacement sensors in industry.

[0003] Existing inductance detection methods generally detect the change in the amplitude or frequency of LC oscillation. However, when the amplitude changes in the case of weak signals and low power consumption, it is very difficult to detect. Moreover, frequency detection has relatively weak anti-interference ability and is greatly affected by temperature drift.

[0004] Therefore, it is necessary to design a novel device and method for detecting equivalent inductance to detect the equivalent inductance value of the output signal of the induction coil, so that it can be applied to the working environment of low power consumption and weak signals, and can be used in angular displacement and metal displacement sensor products, with high sensitivity, easy production, high precision, and strong anti-interference ability. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies of the prior art and provide a novel device and method for detecting equivalent inductance to detect the equivalent inductance value of the output signal of the induction coil, so that it can be applied to the working environment of low power consumption and weak signals, and can be used in angular displacement and metal displacement sensor products, with high sensitivity, easy production, high precision, and strong anti-interference ability.

[0006] To achieve the above object, the present invention provides a novel device and method for detecting equivalent inductance, including a detection device, a high-precision clock, a start trigger, a counter, a stop trigger, a drive circuit, a capacitor, an induction coil, and a PCB circuit board. The induction coil is connected to the detection device. The detection device includes a drive circuit and a time window detection circuit. The time window detection circuit includes a high-precision clock, a start trigger, a counter, and a stop trigger. The drive circuit is respectively connected to the start trigger and the stop trigger. The start trigger and the stop trigger are connected to the counter. The counter is connected to the high-precision clock.

[0007] The induction coil is printed on the PCB circuit board.

[0008] The wire routing of the induction coil ensures that the magnetic field directions generated by its current are consistent.

[0009] The number of induction coils is 1.

[0010] A capacitor is provided on the drive circuit. The drive circuit is an LC oscillation circuit, and the designed impedance of the circuit is preferably the critical damping parameter.

[0011] A detection method for a novel equivalent inductance detection device includes the following steps:

[0012] S1: Move the metal object to be detected closer to or farther away from the induction coil;

[0013] S2: The drive circuit starts to work. The drive circuit drives the capacitor to discharge to the induction coil. The drive circuit triggers the time window detection circuit to trigger the start trigger to start working, and the start trigger enables the counter to start counting;

[0014] S3: When the drive circuit detects that the capacitor discharges to a certain scale or detects that the current change rate input to the induction coil is 0, it triggers the stop trigger to start working, and the stop trigger triggers the counter to stop counting;

[0015] The ways for the drive circuit to discharge to the induction coil include discharging to the induction coil in a capacitor energy storage manner or in a constant voltage and controllable current change rate manner.

[0016] The time window detected by the time window detection circuit includes the time from the start of discharge to the current change rate being 0 or from the start of discharge to discharging to a certain scale.

[0017] The time window detection circuit detects the change in the equivalent inductance value by detecting the change in the time window through a high-precision clock.

[0018] The specific calculation method of the circuit for detecting the equivalent inductance in S1 to S3 is as follows:

[0019] Design a second-order circuit with R, L, and C in series, where the initial value of the capacitor voltage is u C (0 + ) = u C (0 - ) = U0, and the initial value of the inductor current is i L (0 + ) = i L (0 - ) = 0

[0020] According to the second-order circuit, write the circuit equation as -u C + u R + u L = 0

[0021] Where the circuit current is: It can be obtained that

[0022] The obtained circuit equation is:

[0023] Characteristic roots:

[0024]

[0025]

[0026] Overdamping, critical damping;

[0027] 1. Critical damping;

[0028] When That is , the characteristic roots x1, x2 are equal negative real numbers x; at this time, the natural frequencies are equal negative real numbers, and this is critical damping;

[0029] Response at critical damping:

[0030] When the characteristic roots of the equation are the same, u c (t) = (A1 + A2t)e xt , obtain the undetermined coefficients according to the initial values; or use the solution of the non-oscillatory discharge process, let Take the limit to obtain;

[0031] Solution of the non-oscillatory discharge process:

[0032] Take the limit, according to L'Hopital's rule:

[0033]

[0034]

[0035] It can be seen that u c (t) and i L (t) are also exponential functions that decay with time, and are still non-oscillatory responses; where

[0036] 2. Overdamping

[0037] When That is , the characteristic roots x1, x2 are unequal negative real numbers.

[0038] At this time, the natural frequencies are unequal negative real numbers, and this is overdamping:

[0039] Response at overdamping:

[0040] When the characteristic roots are unequal real numbers, the form of the solution of the equation is

[0041]

[0042] Among them:

[0043]

[0044]

[0045] while and the initial condition of the circuit is \(i\) L (0 + ) = \(I_0\), there is

[0046] while

[0047] \(u\) c (0 + ) = \(u_0\), \(i\) L (0 - ) = \(i\) L (0 + ) = 0,

[0048] Meanwhile

[0049]

[0050] Therefore, the initial condition is:

[0051] \(u\) c (0 + ) = \(u_0\),

[0052] Substituting into the equation can solve the undetermined coefficients therein and obtain

[0053]

[0054]

[0055]

[0056] It can be seen that \(u\) c (\(t\)) and \(i\) L (\(t\)) are both exponential functions that decay with time, and the response of the circuit is a non-oscillatory response. Among them, the current reaches the maximum value at the moment \(T_m\) when the rate of change of the current is zero.

[0057]

[0058] Then

[0059]

[0060] The value of the equivalent inductance changes as the detected metal object approaches and moves away from the induction coil, but its impedance does not change. By detecting the value of \(T_m\), the change in the equivalent inductance value \(L\) can be obtained.

[0061] Compared with the prior art, the present invention detects the equivalent inductance value of a metal displacement sensor through a detection device composed of a signal driving circuit and a time window detection circuit. The detection can be completed within only one oscillation period, and the fixed bias magnetic field and the uniformly changing magnetic field do not interfere with the detection circuit, so it has stronger resistance to temperature drift. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a schematic diagram of the device of the present invention.

[0063] Figure 2 It is a schematic diagram of the second-order circuit with R, L, and C in series of the present invention.

[0064] Figure 3 It is a response curve diagram of the critically damped situation of the present invention.

[0065] DESCRIPTION OF THE REFERENCE NUMERALS:

[0066] 1 is a high-precision clock, 2 is a start trigger, 3 is a counter, 4 is a stop trigger, 5 is a driving circuit, 6 is a capacitor, 7 is an induction coil, and 8 is a metal object. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0067] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, 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.

[0068] The present invention will be further described below with reference to the accompanying drawings.

[0069] Referring to Figures 1 - 3 , the present invention provides a novel detection equivalent inductance device and method, including a detection device, a high-precision clock 1, a start trigger 2, a counter 3, a stop trigger 4, a driving circuit 5, a capacitor 6, an induction coil 7, and a PCB circuit board. The induction coil 7 is connected to the detection device. The detection device includes a driving circuit 5 and a time window detection circuit. The time window detection circuit includes a high-precision clock 1, a start trigger 2, a counter 3, and a stop trigger 4. The driving circuit 5 is respectively connected to the start trigger 2 and the stop trigger 4. The start trigger 2 and the stop trigger 4 are connected to the counter 3. The counter 3 is connected to the high-precision clock 1.

[0070] The induction coil 7 is printed on the PCB circuit board.

[0071] The wiring of the induction coil 7 ensures that the magnetic field directions generated by its current are consistent.

[0072] The number of the induction coils 7 is 1.

[0073] A capacitor 6 is provided on the drive circuit 5. The drive circuit 5 is an LC oscillation circuit, and the designed impedance of the circuit is a critically damped parameter.

[0074] A detection method for a novel equivalent inductance detection device includes the following steps:

[0075] S1: Move the metal object 8 to be detected closer to or farther away from the induction coil 7;

[0076] S2: The drive circuit 5 starts to work. The drive circuit 5 drives the capacitor 6 to discharge to the induction coil 7. The drive circuit 5 triggers the time window detection circuit to trigger the start trigger 2 to start working, and the start trigger 2 enables the counter 3 to start counting;

[0077] S3: When the drive circuit 5 detects that the capacitor 6 discharges to a certain scale or detects that the current change rate input to the induction coil is 0, it triggers the stop trigger 4 to start working, and the stop trigger 4 triggers the counter 3 to stop counting;

[0078] The ways for the drive circuit 5 to discharge to the induction coil include discharging to the induction coil in a capacitor energy storage manner or discharging to the induction coil in a constant voltage and controllable current change rate manner.

[0079] The time window detected by the time window detection circuit includes the period from the start of discharge to the current change rate being 0 or from the start of discharge to discharging to a certain scale.

[0080] The time window detection circuit detects the change in the equivalent inductance value by detecting the change in the time window through the high-precision clock 1.

[0081] The specific calculation method of the circuit for detecting the equivalent inductance in S1 to S3 is as follows:

[0082] Design a second-order circuit with R, L, and C in series, where the initial value of the capacitor voltage is u C (0 + ) = u C (0 - ) = U0, and the initial value of the inductor current is i L (0 + ) = i L (0 - ) = 0

[0083] Write the circuit equation according to the second-order circuit as -u C + u R + u L = 0

[0084] Where the circuit current is: It can be obtained that

[0085] The obtained circuit equation is:

[0086] Characteristic roots:

[0087]

[0088]

[0089] Overdamping and critical damping are both acceptable. Preferably, critical damping is selected;

[0090] When That is , the characteristic roots x1, x2 are equal negative real numbers x; at this time, the natural frequency is equal negative real numbers, and at this time it is critical damping;

[0091] Response at critical damping:

[0092] When the characteristic roots of the equation are the same, u c (t) = (A1 + A2t)e xt , and the undetermined coefficients are obtained according to the initial values; or

[0093] Using the solution of the non-oscillatory discharge process, let Take the limit to obtain;

[0094] The solution of the non-oscillatory discharge process is:

[0095] Take the limit, according to L'Hopital's rule:

[0096]

[0097]

[0098] It can be seen that u c (t) and i L (t) are also exponential functions that decay with time and are still non-oscillatory responses; where

[0099] The value of the equivalent inductance changes as the detected metal object 8 approaches and moves away from the induction coil 7, but the impedance does not change. By detecting the Tm value, the change in the equivalent inductance value L can be obtained.

[0100] Example:

[0101] The metal object 8 moves away from the induction coil 7, and the trigger 2 starts to trigger and work. The capacitor 6 discharges to the inductor of the induction coil 7, and the high-precision clock 1 starts to time; the drive circuit detects that the current change rate input to the induction coil is 0, triggers the stop trigger 4 to stop working, stops the high-precision clock 1 from timing, and stops working. At this time, the high-precision clock 1 detects that the time window is T1.

[0102] Further, when the metal object 8 approaches the induction coil 7, the start trigger 2 starts to trigger and work. The capacitor 6 discharges inductively to the induction coil 7, and the high-precision clock 1 starts timing. The drive circuit detects that the current change rate input to the induction coil is 0, triggers the stop trigger 4 to stop working, stops the high-precision clock 1 from timing, and stops working. At this time, the high-precision clock 1 detects that the time window is T2.

[0103] The values of T1 and T2 must be different. The difference between T2 and T1 is caused by the change in the equivalent inductance value due to the metal object moving away from and approaching.

[0104] Working principle:

[0105] By inputting a specific waveform signal or discharging to the induction coil 7 and starting the high-precision clock 1 to time, the detection device circuit receives the output signal of the induction coil 7 circuit part. The detection device circuit processes and calculates the output signal of the induction coil 7 circuit part, processes and calculates the current change rate of the signal. If the current change rate is 0 or the discharge reaches a certain scale, the trigger stops working, the timing stops, and the work stops.

[0106] The drive circuit 5 discharges to the induction coil 7 or the drive circuit 5 inputs a constant voltage with a controllable change rate current to the induction coil 7, and the induction coil 7 will generate magnetic force lines perpendicular to the plane of the induction coil 7. This will cause the metallized area to cut the magnetic force lines to generate Foucault current, which hinders the change of magnetic flux, and further causes the change of the equivalent inductance value of the oscillation circuit.

[0107] When the metal object 8 approaches or moves away from the induction coil 7, or the projected area of the metal object 8 projected onto the induction coil 7 changes, it will affect the change of the equivalent inductance value, and thus the detected time window value will change.

[0108] The present invention solves the problems in the prior art that it is difficult to detect the LC oscillation amplitude change in the case of micro-signal and micro-power consumption, and the detection has weak anti-interference ability and is greatly affected by temperature drift. Through a detection device composed of a signal drive circuit and a time window detection circuit, the equivalent inductance value of the output signal of the induction coil is detected, with high sensitivity, and it can be applied to the working environment of micro-power consumption and micro-signal, and has a simple structure and convenient use.

[0109] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A new type of device for detecting equivalent inductance, characterized in that It includes a detection device, a high-precision clock (1), a start trigger (2), a counter (3), a stop trigger (4), a drive circuit (5), a capacitor (6), an induction coil (7) and a PCB circuit board. The induction coil (7) is connected to the detection device. The detection device includes a drive circuit (5) and a time window detection circuit. The time window detection circuit includes a high-precision clock (1), a start trigger (2), a counter (3) and a stop trigger (4). The drive circuit (5) is respectively connected to the start trigger (2) and the stop trigger (4). The start trigger (2) and the stop trigger (4) are connected to the counter (3). The counter (3) is connected to the high-precision clock (1); The detection method of the novel detection equivalent inductance device includes the following steps: S1: Move the metal object to be detected (8) closer to or farther away from the induction coil (7); S2: The drive circuit (5) starts to work. The drive circuit (5) drives the capacitor (6) to discharge to the induction coil (7). The drive circuit (5) triggers the time window detection circuit to trigger the start trigger (2) to start working. The start trigger (2) enables the counter (3) to start counting; S3: The drive circuit (5) detects that the capacitor (6) discharges until it detects that the current change rate input to the induction coil is 0, and triggers the stop trigger (4) to start working. The stop trigger (4) triggers the counter (3) to stop counting; The time between the start counting and the stop counting in S2 and S3 is recorded as the time window. The time window varies with the change of the equivalent inductance value caused by the metal object to be detected (8) approaching or leaving the induction coil (7).

2. The novel equivalent inductance detection device according to claim 1, wherein The induction coil (7) is printed on the PCB circuit board.

3. A novel equivalent inductance detection device according to claim 1, characterized in that The wiring of the induction coil (7) ensures that the magnetic field directions generated by its current are consistent.

4. A novel equivalent inductance detection device according to claim 2 or 3, characterized in that The number of the induction coils (7) is 1.

5. A novel equivalent inductance detection device according to claim 1, characterized in that, A capacitor (6) is provided on the drive circuit (5). The drive circuit (5) is an LC oscillation circuit, and the circuit design impedance is over-damping and critical-damping parameters.

6. The novel equivalent inductance detection device according to claim 1, wherein The ways for the drive circuit (5) to discharge to the induction coil include discharging to the induction coil in the way of capacitor energy storage or discharging to the induction coil in the way of constant voltage and controllable current change rate.

7. A novel equivalent inductance detection device according to claim 1, characterized in that, The time window detected by the time window detection circuit includes the time from the start of discharge to the current change rate being 0.

8. A novel equivalent inductance detection device according to claim 1, characterized in that, The time window detection circuit detects the change of the equivalent inductance value by detecting the change of the time window through the high-precision clock (1).

9. A novel equivalent inductance detection device according to claim 1, characterized in that, The specific calculation method of the circuit for detecting the equivalent inductance in S1 - S3 is as follows: Design a second-order circuit with R, L, and C in series, where the initial value of the capacitor voltage is u C (0 + ) = u C (0 - ) = U0, The initial value of the inductor current is i L (0 + ) = i L (0 - ) = 0, Based on the described second-order circuit, the circuit equation is written as -u C +u R +u L = 0, where the circuit current is: It can be obtained The circuit equation obtained is as follows: Characteristic root: Over-damping, critical damping; 1. Critical damping When i.e., the characteristic roots x1, x2 are equal negative real numbers x; in this case, the natural frequencies are equal negative real numbers, and this is the critical damping at this time. The response at critical damping: When the characteristic roots of the equation are the same, u c (t) = (A1 + A2t)e xt , determine the undetermined coefficients according to the initial values; or use the solution of the non-oscillatory discharge process and let obtain by taking the limit; The solution of the non-oscillatory discharge process is as follows: Take the limit. According to L'Hopital's rule: It can be seen that u c (t) and i L (t) are also exponential functions that decay with time and are still non-oscillatory responses; where The equivalent inductance value changes as the metal object to be detected (8) approaches and leaves the induction coil (7), but the impedance does not change. The change of the equivalent inductance value L can be obtained by detecting the Tm value; 2. Over-damping When i.e. , the characteristic roots x1 and x2 are unequal negative real numbers; At this time, the natural frequency is unequal negative real numbers, and this is over-damping: The response at over-damping: When the characteristic roots are unequal real numbers, the form of the solution of the equation is Where: while and the initial condition of the circuit \(i\) L (0 + ) = I0, thus u c (0 + ) = U0,i L (0 _ ) = i L (0 + ) = 0; At the same time Therefore, the initial conditions are: Substitute into the equation to solve for the undetermined coefficients and obtain It can be seen that u c (t) and i L (t) are both exponential functions that decay with time, and the response of the circuit is a non-oscillatory response; where the current reaches its maximum value at the moment Tm when the rate of change of the current is zero; Then The equivalent inductance value changes as the detected metal object (8) approaches and moves away from the induction coil (7), but the impedance does not change. By detecting the Tm value, the change in the equivalent inductance value L can be obtained.

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