Double-row time grating linear displacement sensor based on alternating electric field

Abstract

The invention discloses a double-row time grating linear displacement sensor based on an alternating electric field, which relates to the technical field of linear displacement measurement, and is technically characterized by comprising a fixed ruler and a movable ruler, and the movable ruler is composed of a transmitting module; the fixed ruler is composed of an induction module. When the fixed ruler and the movable ruler move relatively, the overlapping area of the transmitting module and the sensing module changes. The transmitting module is connected with a cosine signal, an electric signal output by the induction electrode is connected to the amplifying circuit, and after the electric signal is shaped by the shaping circuit, the phase of a transmitting electrode signal and the phase of an induction electrode signal are compared by the digital phase comparator. A waveform generator device and a subsequent signal processing circuit are connected with a microprocessor to be integrated into an electrical part of the sensor, the result of a counter can be directly output as data or a graph and can also be processed by the microprocessor, so that an intelligent sensor is formed, and the sensor can be compared with other high-precision grating sensors in precision.

Description

Technical Field

[0001] The invention relates to the technical field of linear displacement measurement, in particular to a double-row time-grating linear displacement sensor based on an alternating electric field. Background Art

[0002] Linear displacement measurement is the most basic geometric measurement, which is widely used in industrial practice and scientific practice represented by manufacturing industry. Precision linear displacement measurement mainly uses linear displacement sensors, such as gratings, magnetic gratings, capacitive gratings, etc. These sensors obtain displacement by counting the grid lines evenly divided in space. Their common feature is that they use high-density, ultra-precision spatial grid lines to achieve the resolution requirements of small displacements.

[0003] In order to further improve the measurement resolution and accuracy of the sensor, in addition to relying on advanced scribing technology to increase the scribing density, it is usually necessary to rely on complex electronic subdivision technology to subdivide the original signal output by the sensor, thereby making the structure of the sensor measurement system more complex, increasing costs, and having poor anti-interference capabilities, and being easily affected by interference from the working environment. Therefore, the above technical problems need to be solved. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention proposes a time-grating linear displacement sensor for linear displacement measurement, which does not require precise engraving lines or electronic subdivision boxes, but uses high-frequency clock pulses as a displacement measurement reference to calculate linear displacement. Therefore, it has a simple structure, low cost, high resolution, and strong anti-interference ability.

[0005] To achieve the above object, the present invention provides the following technical solution: a double-row time-grating linear displacement sensor based on an alternating electric field, comprising a fixed scale and a movable scale,

[0006] The dynamic ruler consists of a transmitting module;

[0007] The cut-to-length system consists of a sensing module;

[0008] When the fixed scale and the movable scale move relative to each other, the overlapping area of ​​the transmitting module and the sensing module changes;

[0009] The transmitting module is connected to the cosine signal, and the electrical signal output by the sensing electrode is connected to the amplification circuit, and then shaped by the shaping circuit, and the phase of the transmitting electrode signal and the phase of the sensing electrode signal are compared by the digital phase comparator;

[0010] The phase difference between the two signals is represented by the number of clock pulses inside the FPGA, which is then converted into a linear displacement value and displayed as linear displacement data after being processed by the microprocessor and memory.

[0011] Preferably, the transmitting module is composed of a rectangular transmitting electrode equally divided in upper and lower parts, and the sensing module is composed of a double-sinusoidal sensing electrode equally divided in upper and lower parts.

[0012] Preferably, the planes of the fixed ruler and the movable ruler are opposite and parallel, a vertical distance is left between the fixed ruler and the movable ruler, and the starting points of the fixed ruler and the movable ruler are at the same position, which is 0.

[0013] Preferably, the movable ruler further comprises an emitting unit in area A, which is divided into two groups of independent emitting pieces in area A0 and area A1. Two adjacent rectangular emitting electrodes in area A are spaced π / 2 apart, the starting point of area A1 is 0, and the starting point of area A0 is π / 2.

[0014] Preferably, the signal transmitted by A1 is F1(x)=cos(x), and the signal transmitted by A0 is F0(x)=cos(x+π / 2), wherein x=2*π*f*t, f represents the frequency of the sine wave, and t represents time.

[0015] Preferably, the sizing also includes a receiving unit in area B, which is divided into two independent receiving pieces, area B0 and area B1. The interval between two adjacent pieces in area B is 0, the starting point of area B0 is 0, and the starting point of area B1 is 0.

[0016] Preferably, the B0 area receives signals from the A0 area, and the B1 area receives signals from the A1 area.

[0017] Preferably, the odd-numbered electrodes in the A0 area are marked as S4, the even-numbered electrodes in the A0 area are marked as S3, the odd-numbered electrodes in the A1 area are marked as S1, the even-numbered electrodes in the A1 area are marked as S2, the S4 electrode emission signal is F1(x)=cos(x), the S1 electrode emission signal is F2(x)=cos(x+π), the S3 electrode emission signal is F3(x)=cos(x+π / 2), and the S2 electrode emission signal is F4(x)=cos(x+3π / 2).

[0018] Preferably, the integral of the overlapping area of ​​odd electrodes in region A1 is S1(p)=∫(2a-(a+cos(p)))dp, the integral of the overlapping area of ​​even electrodes is S2(p)=∫(2a-(a-cos(p)))dp, the integral of the overlapping area of ​​odd electrodes in region A0 is S3(p)=∫(2a-(a-sin(p)))dp, the integral of the overlapping area of ​​even electrodes is S4(p)=∫(2a-(a+sin(p)))dp, and the synthesized signal is F1(x)*S1(p)+F2(x)*S2(p)-[F3(x)*S3(p)+F4(x)*S4(p)]=2sin(x+p), wherein a represents the vertical height of the sinusoidal pattern, and the phase difference p value is calculated, p=(p / 8mm)*(2*π), which is converted to obtain the linear displacement value y.

[0019] Compared with the prior art, the present invention provides a double-row time-grating linear displacement sensor based on an alternating electric field, which has the following beneficial effects: the movable scale and the fixed scale as the sensing part of the sensor can be independently formed into a mechanical structural component in a traditional manner, and the waveform generator device and the subsequent signal processing circuit are integrated with a microprocessor into a sensor electrical part. The result of the counter can be directly output as data or graphics, and can also be processed by a microprocessor, thereby forming an intelligent sensor. This sensor can be compared in accuracy with other high-precision grating sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A combined diagram of the corresponding relationship between the movable scale and the fixed scale positions of the invention;

[0021] Figure 2 It is the wiring diagram of the movable ruler electrode of the invention;

[0022] Figure 3 It is a schematic diagram of the wiring of the fixed-length electrode of the invention;

[0023] Figure 4 The schematic diagram of the invented signal generation and data processing system;

[0024] Figure 5 A phase comparison diagram of the excitation signal and the synthetic signal of the invention. DETAILED DESCRIPTION

[0025] In the present invention, unless otherwise specified, the directions used, such as "up" and "down", usually refer to the directions shown in the drawings, or to the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "left" and "right" usually refer to the left and right shown in the drawings; "inside" and "outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directions are not used to limit the present invention.

[0026] See also Figure 1-5 The present invention provides a technical solution of a double-row time-grating linear displacement sensor based on an alternating electric field: comprising a fixed scale and a movable scale,

[0027] The dynamic ruler consists of a transmitting module;

[0028] The cut-to-length system consists of a sensing module;

[0029] When the fixed scale and the movable scale move relative to each other, the overlapping area of ​​the transmitting module and the sensing module changes;

[0030] The transmitting module is connected to the cosine signal, and the electrical signal output by the sensing electrode is connected to the amplification circuit, and then shaped by the shaping circuit, and the phase of the transmitting electrode signal and the phase of the sensing electrode signal are compared by the digital phase comparator;

[0031] The phase difference between the two signals is represented by the number of clock pulses inside the FPGA, which is then converted into a linear displacement value, and then processed by the microprocessor and memory to display the linear displacement data;

[0032] The transmitting module is composed of a rectangular transmitting electrode equally divided from top to bottom, and the sensing module is composed of a double sinusoidal sensing electrode equally divided from top to bottom. The fixed scale and the movable scale are parallel to each other, and a vertical distance is left between the fixed scale and the movable scale. The starting points of the fixed scale and the movable scale are at the same position, both of which are 0.

[0033] The movable ruler also includes a transmitting unit in area A, which is divided into two groups of independent transmitting pieces in area A0 and area A1. The interval between two adjacent rectangular transmitting electrodes in area A is π / 2. The starting point of area A1 is 0, and the starting point of area A0 is π / 2. The signal transmitted by A1 is F1(x)=cos(x), and the signal transmitted by A0 is F0(x)=cos(x+π / 2), wherein x=2*π*f*t, f represents the frequency of the sine wave, and t represents time;

[0034] The sizing also includes a receiving unit in area B, which is divided into two independent receiving pieces, area B0 and area B1. The interval between two adjacent pieces in area B is 0, the starting point of area B0 is 0, and the starting point of area B1 is 0. Area B0 receives signals from area A0, and area B1 receives signals from area A1.

[0035] The odd-numbered electrodes in the A0 region are labeled as S4, the even-numbered electrodes in the A0 region are labeled as S3, the odd-numbered electrodes in the A1 region are labeled as S1, the even-numbered electrodes in the A1 region are labeled as S2, the S4 electrode transmits a signal F1(x)=cos(x), the S1 electrode transmits a signal F2(x)=cos(x+π), the S3 electrode transmits a signal F3(x)=cos(x+π / 2), and the S2 electrode transmits a signal F4(x)=cos(x+3π / 2);

[0036] The integral of the overlapping area of ​​the odd-numbered electrodes in the A1 region is S1(p)=∫(2a-(a+cos(p)))dp, the integral of the overlapping area of ​​the even-numbered electrodes is S2(p)=∫(2a-(a-cos(p)))dp, the integral of the overlapping area of ​​the odd-numbered electrodes in the A0 region is S3(p)=∫(2a-(a-sin(p)))dp, the integral of the overlapping area of ​​the even-numbered electrodes is S4(p)=∫(2a-(a+sin(p)))dp, and the synthesized signal is F1(x)*S1(p)+F2(x)*S2(p)-[F3(x)*S3(p)+F4(x)*S4(p)]=2sin(x+p), wherein a represents the vertical height of the sinusoidal pattern, and the phase difference p value is calculated, p=(p / 8mm)*(2*π), which is converted into the linear displacement value y;

[0037] When the movable ruler area A and the fixed ruler area B move relative to each other, the fixed ruler sensing electrode uses a pair of double sinusoidal pole pieces arranged in a pair of poles with a spatial position difference of 2π. Its shape is formed by connecting two double sinusoidal function curves, and then picks up the traveling wave signal through the electric field coupling between the movable ruler and the fixed ruler. For ease of understanding, the sensing mechanism of a single double sinusoidal sensing electrode is first analyzed. A single double sinusoidal sensing electrode and the corresponding excitation electrode form a flat plate capacitor when the gap is L. For an ideal flat plate capacitor (ignoring the edge effect of the electrode), C = εS / L, where ε is the dielectric constant of the intervening material. When the values ​​of L and ε remain constant, the output signal is a linear response of the change in the overlapping area S between the sensing electrode and the excitation electrode. Therefore, when the sensing electrode moves relative to the excitation electrode, the linear displacement between the excitation electrode and the sensing electrode is proportional to the effective area of ​​the capacitor. Assuming that the length of the rectangular electrode in area A is 2d and the width is 2π / 4, the area integration method is used to integrate the linear displacement of the movable ruler in a period of time to obtain ΔS,

[0038] When moving between 0 and 2π / 4, ΔS1=d*(2π / 4)+sin(p)-cos(p); ΔS2=d*(2π / 4)-sin(p)+cos(p); ΔS3=d*(2π / 4)+sin(p)+cos(p); ΔS4=d*(2π / 4)-sin(p)-cos(p);

[0039] When moving between 2π / 4 and 4π / 4, ΔS1=d*(2π / 4)+sin(p)+cos(p); ΔS2=d*(2π / 4)-sin(p)-cos(p); ΔS3=d*(2π / 4)-sin(p)+cos(p); ΔS4=d*(2π / 4)+sin(p)-cos(p);

[0040] When moving between 4π / 4 and 6π / 4, ΔS1=d*(2π / 4)-sin(p)+cos(p); ΔS2=d*(2π / 4)+sin(p)-cos(p); ΔS3=d*(2π / 4)-sin(p)-cos(p); ΔS4=d*(2π / 4)+sin(p)+cos(p);

[0041] When moving between 6π / 4 and 8π / 4, ΔS1=d*(2π / 4)-sin(p)-cos(p); ΔS2=d*(2π / 4)+sin(p)+cos(p); ΔS3=d*(2π / 4)+sin(p)-cos(p); ΔS4=d*(2π / 4)-sin(p)+cos(p);

[0042] When F1(x)=cos(x) is applied to S1, F2(x)=cos(x+π / 2) is applied to S2, F3(x)=cos(x+π) is applied to S3, and F4(x)=cos(x+3π / 2) is applied to S4, the feedback signal received by area B1 minus the feedback signal received by area B0 is obtained to obtain the synthesized signal ΔU:

[0043] ΔU=F1(x)*S1(p)+F2(x)*S2(p)-[F3(x)*S3(p)+F4(x)*S4(p)],

[0044] When moving between 0 and 2π / 4, ΔU = 2[sin(x+p)-cos(x+p)];

[0045] When moving between 2π / 4 and 4π / 4, ΔU = 2[sin(x+p)+cos(x+p)];

[0046] When moving between 4π / 4 and 6π / 4, ΔU = -2[sin(x+p)-cos(x+p)];

[0047] When moving between 6π / 4 and 8π / 4, ΔU = -2[sin(x+p)+cos(x+p)];

[0048] When the movement is from 0 to 2π, it is a complete cycle. By comparing the ΔU signal with the transmitted cosine signal cos(x), the relative displacement y value between the moving ruler and the fixed ruler can be obtained.

[0049] See also Figure 2 This is a schematic diagram of the wiring of the moving ruler electrode of the first embodiment. The rectangular electrodes of the moving ruler are all arranged with copper on the printed PCB circuit board. A1 area punches holes on the back of the PCB board to connect all the rectangular electrodes marked with S1 through PCB wiring to input the cos(x) electrical signal. A1 area punches holes on the back of the PCB board to connect all the rectangular electrodes marked with S2 through PCB wiring to input the cos(x+π) electrical signal. A0 area punches holes on the back of the PCB board to connect all the rectangular electrodes marked with S3 through PCB wiring to input the cos(x+π / 2) electrical signal. A1 area punches holes on the back of the PCB board to connect all the rectangular electrodes marked with S4 through PCB wiring to input the cos(x+3π / 2) electrical signal. The rectangular electrode marked with GND is grounded to prevent signal crosstalk between electrodes. The rectangular electrode marked with Ub1 receives the feedback signal of the fixed-length B1 area and is connected to the positive end of the signal processing subtractor module. The rectangular electrode marked with Ub0 receives the feedback signal of the fixed-length B0 area and is connected to the negative end of the signal processing subtractor module, thereby realizing the synthesis signal.

[0050] See also Figure 3This is a schematic diagram of the fixed-length electrode wiring of the first embodiment. The rectangular electrodes and the double-sinusoidal pattern electrodes on the fixed-length are all arranged on the copper plating of the printed PCB circuit board. The copper skins of the double-sinusoidal electrodes marked with b1 in the B1 area are all connected to the rectangular copper skin marked with Ub1 through wiring, and the Ub1 signal is fed back to the A1 area. The copper skins of the double-sinusoidal electrodes marked with b0 in the B0 area are all connected to the rectangular copper skin marked with Ub0 through wiring, and the Ub0 signal is fed back to the A0 area.

[0051] See also Figure 4 This is a schematic diagram of the signal generation and data processing system of the first embodiment. The microprocessor and memory control the digital signal generator to generate four cosine signals with a phase difference of 90 degrees to the excitation electrode of the time grid sensor, and the excitation electrode and the sensing electrode move relative to each other; the two electrical signals output by the sensing electrode are amplified and rectified by the synthetic signal after the signal processing subtractor module and the cosine signal generated by the waveform generator is compared in phase by the digital phase comparator; the phase difference of the two signals is represented by the number of interpolated clock pulses, and then converted into a linear displacement value, which is directly or after being processed by the microprocessor and memory as linear displacement data for display.

[0052] See also Figure 5 This is a phase comparison diagram of the excitation signal and the synthetic signal of Example 1. The line marked 1 is the waveform of the cosine excitation signal, and the lines marked 2, 3, and 4 are the synthetic signal waveforms of the moving ruler moving 3π / 8, 2π / 8, and π / 8, respectively. The relative displacement between the moving ruler and the fixed ruler can be reflected by the difference in phase between the excitation signal and the synthetic signal.

[0053] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A double-row time-grating linear displacement sensor based on an alternating electric field, comprising a fixed scale and a moving scale, characterized in that: The dynamic ruler consists of a transmitting module; The cut-to-length system consists of a sensing module; When the fixed scale and the movable scale move relative to each other, the overlapping area of ​​the transmitting module and the sensing module changes; The transmitting module is connected to the cosine signal, and the electrical signal output by the sensing electrode is connected to the amplification circuit, and then shaped by the shaping circuit, and the phase of the transmitting electrode signal and the phase of the sensing electrode signal are compared by the digital phase comparator; The phase difference between the two signals is represented by the number of clock pulses inside the FPGA, which is then converted into a linear displacement value and displayed as linear displacement data after being processed by the microprocessor and memory.

2. The double-row time-grating linear displacement sensor based on an alternating electric field according to claim 1, characterized in that: The transmitting module is composed of rectangular transmitting electrodes equally divided up and down, and the sensing module is composed of double sinusoidal sensing electrodes equally divided up and down.

3. The double-row time-grating linear displacement sensor based on alternating electric field according to claim 1, characterized in that: The planes of the fixed ruler and the movable ruler are opposite and parallel, a vertical distance is left between the fixed ruler and the movable ruler, and the starting points of the fixed ruler and the movable ruler are at the same position, both of which are 0.

4. The double-row time-grating linear displacement sensor based on an alternating electric field according to claim 2, characterized in that: The movable ruler also includes an emitting unit in area A, which is divided into two groups of independent emitting pieces in area A0 and area A1. The interval between two adjacent rectangular emitting electrodes in area A is π / 2, the starting point of area A1 is 0, and the starting point of area A0 is π / 2.

5. The double-row time-grating linear displacement sensor based on alternating electric field according to claim 4, characterized in that: The signal transmitted by A1 is F1(x)=cos(x), and the signal transmitted by A0 is F0(x)=cos(x+π / 2), wherein x=2*π*f*t, f represents the frequency of the sine wave, and t represents time.

6. The double-row time-grating linear displacement sensor based on alternating electric field according to claim 4, characterized in that: The sizing also includes a receiving unit in area B, which is divided into two independent receiving pieces, area B0 and area B1. The interval between two adjacent pieces in area B is 0, the starting point of area B0 is 0, and the starting point of area B1 is 0.

7. The double-row time-grating linear displacement sensor based on alternating electric field according to claim 6, characterized in that: The B0 area receives the A0 area signal, and the B1 area receives the A1 area signal.

8. The double-row time-grating linear displacement sensor based on alternating electric field according to claim 4, characterized in that: The odd-numbered electrodes in the A0 area are marked as S4, the even-numbered electrodes in the A0 area are marked as S3, the odd-numbered electrodes in the A1 area are marked as S1, the even-numbered electrodes in the A1 area are marked as S2, the signal emitted by the S4 electrode is F1(x)=cos(x), the signal emitted by the S1 electrode is F2(x)=cos(x+π), the signal emitted by the S3 electrode is F3(x)=cos(x+π / 2), and the signal emitted by the S2 electrode is F4(x)=cos(x+3π / 2).

9. The double-row time-grating linear displacement sensor based on alternating electric field according to claim 8, characterized in that: The integral of the overlapping area of ​​the odd electrodes in region A1 is S1(p)=∫(2a-(a+cos(p)))dp, the integral of the overlapping area of ​​the even electrodes is S2(p)=∫(2a-(a-cos(p)))dp, the integral of the overlapping area of ​​the odd electrodes in region A0 is S3(p)=∫(2a-(a-sin(p)))dp, the integral of the overlapping area of ​​the even electrodes is S4(p)=∫(2a-(a+sin(p)))dp, and the synthesized signal is F1(x)*S1(p)+F2(x)*S2(p)-[F3(x)*S3(p)+F4(x)*S4(p)]=2sin(x+p), wherein a represents the vertical height of the sinusoidal pattern, and the phase difference p value is calculated, p=(y / 8mm)*(2*π), which is converted into the linear displacement value y.

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