A capacitive time-grating linear displacement sensor

Abstract

The invention discloses a capacitive time-grating linear displacement sensor, which relates to the technical field of linear displacement measurement. Its technical key points include a fixed scale and a movable scale, the movable scale is composed of a transmitting module; the fixed scale is composed of a sensing module; when the fixed scale and the movable scale undergo relative movement, the overlapping area of ​​the transmitting module and the sensing module changes; the transmitting module is connected to four sinusoidal wave signals with a phase difference of 90 degrees, the sensing module outputs two induced electrical signals connected to a subtractor amplifier circuit, and then after being shaped by a shaping circuit, the signal phase of the transmitting module and the signal phase of the sensing module are compared. The technical effect is that the sensor can be compared with other types of high-precision sensors for accuracy, does not require precise engraving, but uses a high-frequency clock pulse as a displacement measurement reference to calculate the linear displacement, so it has the advantages of simple structure, low cost, high resolution, strong anti-interference ability, and easy productization.

Description

Technical Field

[0001] The invention relates to the technical field of linear displacement measurement, in particular to a capacitive time-grating linear displacement sensor. Background Art

[0002] With the development of electronic circuits and information technology, related applications have gradually been popularized. At present, there are applications of time-grating linear displacement sensors in the field of measurement and detection. It is based on time-grating measurement technology and uses clock pulses as the linear displacement measurement benchmark through time-space coordinate conversion. It has the characteristics of high precision, high resolution and fast response, and can be applied to industrial automation, robots, aerospace, weapons and equipment, metrology and detection, etc.

[0003] In order to further improve the measurement resolution and accuracy of the sensor, the spatial precision engraving has extremely high requirements on the processing equipment and processing environment, which makes the structure of the sensor measurement system more complicated, increases the cost, and has poor anti-interference ability, which is easily affected by the interference of 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 use precise engraving lines, but uses high-frequency clock pulses as the displacement measurement reference to calculate the 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 capacitive time-grating linear displacement sensor, 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 four sinusoidal wave signals with a phase difference of 90 degrees. The sensing module outputs two induced electrical signals which are connected to the subtractor amplifier circuit. After being shaped by the shaping circuit, the phase of the transmitting module signal is compared with the phase of the sensing module signal.

[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 directly transmitted to the host computer for processing and display of linear displacement data.

[0011] Preferably, the transmitting module is composed of rectangular transmitting electrodes equally divided into upper and lower parts, and the sensing module is composed of sinusoidal sensing electrodes.

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

[0014] Preferably, the signal emitted by A1 is F1(x) = sin(x), and the signal emitted by A0 is F0(x) = cos(x), 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 B0 and B1, the interval between two adjacent pieces in area B is 0, the starting point of B0 is π / 2, and the starting point of 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 signal emitted by the S4 electrode is F1(x) = sin(x+π / 2), the signal emitted by the S1 electrode is F2(x)=sin(x+π), the signal emitted by the S3 electrode is F3(x)=sin(x+3π / 2), and the signal emitted by the S2 electrode is F4(x)=sin(x).

[0018] Preferably, the integral of the overlapping area of ​​odd-numbered electrodes in region A0 is S4(p)=∫(2a-(a+cos(p)))dp, the integral of the overlapping area of ​​even-numbered electrodes is S3(p)=∫(2a-(a-cos(p)))dp, the integral of the overlapping area of ​​odd-numbered electrodes in region A1 is S1(p)=∫(2a-(a-sin(p)))dp, the integral of the overlapping area of ​​even-numbered electrodes is S2(p)=∫(2a-(a+sin(p)))dp, and the synthesized signal is F1(x)*S4(p)+F3(x)*S3(p)-[F2(x)*S1(p)+F4(x)*S2(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 to obtain the linear displacement value y.

[0019] Compared with the prior art, the present invention provides a capacitive time-grating linear displacement sensor having the following beneficial effects: the sensor can be compared with other types of high-precision sensors for accuracy, and does not require precise engraving lines, but uses high-frequency clock pulses as the displacement measurement reference to calculate linear displacement. Therefore, the sensor has the advantages of simple structure, low cost, high resolution, strong anti-interference ability, and easy commercialization. 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 wiring diagram 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 capacitive time-grating linear displacement sensor: 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 four sinusoidal wave signals with a phase difference of 90 degrees. The sensing module outputs two induced electrical signals which are connected to the subtractor amplifier circuit. After being shaped by the shaping circuit, the phase of the transmitting module signal is compared with the phase of the sensing module signal.

[0031] The phase difference of the two signals is represented by the number of clock pulses inside the FPGA, which is then converted into a linear displacement value and directly transmitted to the host computer for processing to display the linear displacement data. The FPGA controls the digital signal generator to generate four sinusoidal signals with a phase difference of 90 degrees and send them to the transmitting electrode of the time-grid sensor. The transmitting 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 synthesized signal after the signal processing subtractor module and the sinusoidal signal generated by the waveform generator is compared with the 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. The linear displacement data is displayed directly or after being processed by the microprocessor and memory.

[0032] The transmitting module is composed of rectangular transmitting electrodes equally divided from top to bottom, and the sensing module is composed of sinusoidal sensing electrodes. The fixed scale and the moving scale are parallel to each other, and a vertical distance is left between the fixed scale and the moving scale. The starting points of the fixed scale and the moving scale are at the same position, both 0. The moving scale also includes the transmitting unit in area A, which is divided into two independent transmitting pieces A0 and A1. The interval between two adjacent rectangular transmitting electrodes in area A is π / 2, the starting point of A1 is 0, and the starting point of A0 is 0;

[0033] The signal transmitted by A1 is F1(x)=sin(x), and the signal transmitted by A0 is F0(x)=cos(x);

[0034] The electrode pattern planes of the moving ruler and the fixed ruler are relatively parallel. When the moving ruler area A and the fixed ruler area B move relative to each other, the fixed ruler sensing electrode uses two sinusoidal pole pieces with a spatial position difference of 0 arranged in a pair of poles. Its shape is formed by connecting the sine function curve with the coordinate axis, and then the traveling wave signal is picked up through the electric field coupling between the moving ruler and the fixed ruler. When the sensing electrode moves relative to the transmitting electrode, the linear displacement between the transmitting 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 linear displacement of the moving ruler in a period of time can be integrated by the area integration method to obtain ΔS;

[0035] When the displacement y moves 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);

[0036] When the displacement y moves 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);

[0037] When the displacement y moves 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);

[0038] When the displacement y moves between 6π / 4~8π / 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);

[0039] The signal emitted by the S4 electrode is F1(x)=sin(x+π / 2), the signal emitted by the S1 electrode is F2(x)= sin(x+π), the signal emitted by the S3 electrode is F3(x)=sin(x+3π / 2), and the signal emitted by the S2 electrode is F4(x)= sin(x).

[0040] The cut length also includes a receiving unit in area B, which is divided into two independent receiving sheets, B0 and B1. The interval between two adjacent sheets in area B is 0, the starting point of B0 is π / 2, and the starting point of B1 is 0. Area B0 receives signals from area A0, and area B1 receives signals from area A1. The rectangular electrodes and double sinusoidal pattern electrodes on the cut length are all copper-plated on a printed PCB circuit board. All the copper skins of the sinusoidal electrodes marked with b1 in area B1 are connected to the rectangular copper skin marked with Ub1 through wiring, and the Ub1 signal is fed back to area A1. All the copper skins of the sinusoidal electrodes marked with b0 in area B0 are connected to the rectangular copper skin marked with Ub0 through wiring, and the Ub0 signal is fed back to area A0.

[0041] The feedback signal received in area B0 minus the feedback signal received in area B1 is the synthesized signal ΔU:

[0042] ΔU=F1(x)*S4(p)+F3(x)*S3(p)-[F2(x)*S1(p)+F4(x)*S2(p)],

[0043] When the displacement y moves between 0 and 2π / 4, ΔU = 2[sin(x+p)-cos(x+p)];

[0044] When the displacement y moves between 2π / 4 and 4π / 4, ΔU = 2[sin(x+p)+cos(x+p)];

[0045] When the displacement y moves between 4π / 4 and 6π / 4, ΔU = -2[sin(x+p)-cos(x+p)];

[0046] When the displacement y moves between 6π / 4 and 8π / 4, ΔU = -2[sin(x+p)+cos(x+p)];

[0047] When the displacement y moves from 0 to 2π, it is just a complete cycle. By comparing the ΔU signal with the emitted sinusoidal signal sin(x), the relative displacement y value between the moving scale and the fixed scale can be obtained.

[0048] The odd electrodes in the A0 area are marked as S4, the even electrodes in the A0 area are marked as S3, the odd electrodes in the A1 area are marked as S1, and the even electrodes in the A1 area are marked as S2. The rectangular electrodes of the movable ruler are all arranged on the copper plating of the printed PCB circuit board. In the A1 area, holes are punched on the back of the PCB board to connect all the rectangular electrodes marked with S1 through PCB wiring to input the sin(x+π) electrical signal. In the A1 area, holes are punched on the back of the PCB board to connect all the rectangular electrodes marked with S2 through PCB wiring to input the sin(x) electrical signal. In the A0 area, holes are punched on the back of the PCB board to connect all the rectangular electrodes marked with S3 through PCB wiring to input the sin (x+3π / 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 sin(x+π / 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-size B1 area and is connected to the negative end of the signal processing subtractor module, the rectangular electrode marked with Ub0 receives the feedback signal of the fixed-size B0 area and is connected to the positive end of the signal processing subtractor module, so as to realize the synthetic signal, the S4 electrode transmits the signal F1(x)=sin(x+π / 2), the S1 electrode transmits the signal F2(x)= sin(x+π), the S3 electrode transmits the signal F3(x)=sin(x+3π / 2), and the S2 electrode transmits the signal F4(x)=sin(x);

[0049] The integral of the overlapping area of ​​odd-numbered electrodes in region A0 is S4(p)=∫(2a -(a+cos(p)))dp, the integral of the overlapping area of ​​even-numbered electrodes is S3(p)=∫(2a -(a-cos(p)))dp, the integral of the overlapping area of ​​odd-numbered electrodes in region A1 is S1(p) =∫(2a -(a-sin(p)))dp, the integral of the overlapping area of ​​even-numbered electrodes is S2(p)=∫(2a-(a+sin(p)))dp, the synthesized signal is F1(x)*S4(p)+F3(x)*S3(p)-[F2(x)*S1(p)+F4(x)*S2(p)]= 2sin(x+p), where a represents the vertical height of the sinusoidal pattern, the phase difference p value is calculated, p=(y / 8mm)*(2*π), and the linear displacement value y is converted;

[0050] It should be noted that: Figure 5 The line marked 1 is the waveform of the sinusoidal excitation signal, and the lines marked 2, 3, and 4 are the synthetic signal waveforms of the moving ruler moving 5π / 8, 6π / 8, and 7π / 8, respectively. The relative displacement between the moving ruler and the fixed ruler can be reflected by the phase difference between the excitation signal and the synthetic signal.

[0051] 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 capacitive time-grating linear displacement sensor, 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 four sinusoidal wave signals with a phase difference of 90 degrees. The sensing module outputs two induced electrical signals which are connected to the subtractor amplifier circuit. After being shaped by the shaping circuit, the phase of the transmitting module signal is compared with the phase of the sensing module signal. 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 directly transmitted to the host computer for processing and display as linear displacement data; 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 A1 is 0, and the starting point of A0 is 0; The odd-numbered electrodes in the A0 region are marked as S4, the even-numbered electrodes in the A0 region are marked as S3, the odd-numbered electrodes in the A1 region are marked as S1, the even-numbered electrodes in the A1 region are marked as S2, the signal emitted by the S4 electrode is F1(x)=sin(x+π / 2), the signal emitted by the S1 electrode is F2(x)=sin(x+π), the signal emitted by the S3 electrode is F3(x)=sin(x+3π / 2), and the signal emitted by the S2 electrode is F4(x)=sin(x), wherein x=2*π*f*t, f represents the frequency of the sine wave, and t represents time; The integral of the overlapping area of ​​the odd electrodes in region A0 is S4(p)=∫(2a -(a+cos(p)))dp, the integral of the overlapping area of ​​the even electrodes is S3(p)=∫(2a-(a-cos(p)))dp, the integral of the overlapping area of ​​the odd electrodes in region A1 is S1(p)=∫(2a -(a-sin(p)))dp, the integral of the overlapping area of ​​the even electrodes is S2(p)=∫(2a-(a+sin(p)))dp, and the synthesized signal is F1(x)*S4(p)+F3(x)*S3(p)-[F2(x)*S1(p)+F4(x)*S2(p)]= 2sin(x+p), where a represents the vertical height of the sinusoidal pattern, and to calculate the phase difference p value, p=(y / 8mm)*(2*π), which is converted to obtain the linear displacement value y.

2. A capacitive time-grating linear displacement sensor according to claim 1, characterized in that: The transmitting module is composed of rectangular transmitting electrodes equally divided into upper and lower parts, and the sensing module is composed of sinusoidal sensing electrodes.

3. The capacitive time-grating linear displacement sensor 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 capacitive time-grating linear displacement sensor according to claim 1, characterized in that: The signal transmitted by A1 is F1(x)=sin(x), and the signal transmitted by A0 is F0(x)=cos(x), wherein x=2*π*f*t, f represents the frequency of the sine wave, and t represents time.

5. The capacitive time-grating linear displacement sensor 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 π / 2, and the starting point of area B1 is 0.

6. A capacitive time-grating linear displacement sensor according to claim 5, characterized in that: The B0 area receives the A0 area signal, and the B1 area receives the A1 area signal.

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