Capacitive grating sensor and absolute position measuring device

Abstract

The present invention provides a capacitive grating sensor and an absolute position measuring device. The capacitive grating sensor includes: a first grating plate, on which there are provided a first coupling pole array having a first pitch and including a plurality of first coupling poles, a first reflecting pole electrically connected to the plurality of first coupling poles, a second coupling pole array having a second pitch and including a plurality of second coupling poles, and a second reflecting pole electrically connected to the plurality of second coupling poles; and a second grating plate, on which there are provided an emitter array having a standard pitch and including a plurality of emitter sub-arrays, and a first receiving pole and a second receiving pole arranged on both sides of the emitter array and electrically isolated from it. Each emitter sub-array includes a plurality of emitter sheets. The shapes of the first coupling poles and the second coupling poles are the same or similar. The first coupling pole array and the second coupling pole array are arranged in a reverse interleaved manner and are opposite to the emitter array in space. The first pitch is not equal to the second pitch.

Description

Technical Field

[0001] The present invention relates to a capacitive grating sensor and an absolute position measuring device, in particular to a capacitive grating measuring device for absolute position measurement. Background Art

[0002] In displacement measuring devices, using a capacitive grating sensor as a displacement detection element is one of the most extensive applications of capacitive gratings. The capacitive grating sensor can form a displacement measuring element for measuring length, angle, speed, precision positioning, servo tracking and other measuring devices. It forms a capacitive grating sensor measuring device with a displacement measuring circuit, and there are periodic and absolute types. In particular, in the case of a large displacement measurement range, a periodic (grating type) measuring device must be used. The periodic measuring device obtains measurement data by comparing the difference between the signal amplitude (or phase) within a period (pitch, also called pole pitch or grating pitch) and a reference value. The measurement data within one period is the corresponding position value, which can be regarded as absolute type; when measuring a displacement exceeding one period, if the displacement deviation signal values detected are measured by algebraic accumulation of the data of each period, it is incremental type; if the position values of each period are combined by identifying the codes of each period, it is absolute type.

[0003] According to different signal processing methods, capacitive grating sensors are further divided into phase discrimination type and amplitude discrimination type. The working principles of currently widely used phase discrimination type capacitive grating sensors all follow the technology disclosed in US Patent US4437055 (1984) and similar technologies. By adopting a moving grating and a fixed grating structure, using the pitch as the measurement period, applying the gate average effect and multi-channel active driving technology, and supplemented by the implementation means of large-scale integrated circuits, the absolute position quantity within a period is obtained by phase discrimination, and the direction is counted according to the detection of multi-channel active driving signals with different phases. The measurement exceeding one period (pitch) is realized by continuous detection. After more than 30 years of development, it has become increasingly perfect and mature in the processing and manufacturing of the moving and fixed gratings of the sensor, the improvement of integrated circuits and the analysis of errors, and has developed from incremental displacement measurement to absolute displacement measurement. In an absolute displacement sensor, the absolute displacement (position) of the movable part relative to the fixed part can be obtained without continuously counting the operation of the periodic signal.

[0004] Mitutoyo Corporation (Japan) has developed a capacitive measuring device capable of absolute measurement (see U.S. Patent No. 4,420,754, hereinafter referred to as the "754 patent"). This device uses two sets of electrode arrays (emitter / receiver pairs) arranged side by side. In each array pair, the distance between the emitter electrode and the receiver electrode is the same, but between the two array pairs, the distances between the corresponding emitter and receiver electrodes are slightly different. Additionally, the two sets of electrode arrays have their own periodic drive signals and corresponding independent received signals, and absolute measurement is achieved by measuring the phase difference between the two received signals. However, the practicality of the measuring device of the 754 patent is limited. For example, since the calculation of the absolute measurement value is based on two independent measurements, the accumulation of slight errors in both measurements can cause large position measurement errors. Therefore, in order to obtain accurate absolute position measurement, the corresponding signal processing circuit must have precisely matched performance characteristics. Moreover, if the two processes cannot be precisely carried out simultaneously, even a very small displacement of the support members relative to each other between the two measurements will cause large errors in position measurement. In addition, in the measuring device of the 754 patent, the actual requirements of the two separate electrode arrays limit its application in manual test tools with small size requirements.

[0005] The Chinese patents CN89106051 (hereinafter referred to as the "051 patent") and CN931177014 (hereinafter referred to as the "014 patent") of Mitutoyo Corporation (Japan) disclose a capacitive absolute displacement sensor that uses thick, medium, and thin three-electrode arrays and has three signal outputs: a periodic signal with a coarse pitch (coarse scale signal), a periodic signal with a medium pitch (medium scale signal), and a periodic signal with a fine pitch (fine scale signal), corresponding to the electrode structure shapes formed on the moving grating and the fixed grating. By processing the phase information of these periodic signals, the absolute displacement of the movable component can be detected. The 051 patent and the 014 patent avoid some of the deficiencies of the 754 patent, but also introduce new problems because the calculation and processing of the three different modes of signals relative to the reference signal require synchronous modulation control, which is very complex and greatly increases the complexity and structural size of the electronic unit processing device. Summary of the Invention

[0006] Therefore, the object of the present invention is to overcome the above-mentioned defects of the prior art and provide a capacitive grating sensor, which includes:

[0007] A first grating plate, on which there is provided a first coupling pole array having a first pitch and including a plurality of first coupling poles, a first reflecting pole electrically connected to the plurality of first coupling poles, a second coupling pole array having a second pitch and including a plurality of second coupling poles, and a second reflecting pole electrically connected to the plurality of second coupling poles, and

[0008] A second grid plate, on which an emitter array with a standard pitch including a plurality of emitter sub-arrays is provided, and a first receiver electrode and a second receiver electrode which are arranged on both sides of the emitter array and are electrically isolated from it. The emitter sub-array includes a plurality of emitter sheets. The first receiver electrode is spatially opposite to the first reflector electrode, and the second receiver electrode is spatially opposite to the second reflector electrode.

[0009] Wherein, one of the first grid plate and the second grid plate is a fixed grid plate, and the other is a movable grid plate. The movable grid plate is configured to be able to move relative to the fixed grid plate.

[0010] The first coupling electrode and the second coupling electrode have the same or similar shapes. The first coupling electrode array and the second coupling electrode array are arranged in a reverse interleaved manner and are opposite to the emitter array in space. The first pitch is not equal to the second pitch.

[0011] For the grid capacitance sensor according to the present invention, preferably, the first reflector electrode includes an array composed of a plurality of first reflector sheets, the second reflector electrode includes an array composed of a plurality of second reflector sheets, the plurality of first reflector sheets are electrically connected to the plurality of first coupling electrodes in a one-to-one correspondence, and the plurality of second reflector sheets are electrically connected to the plurality of second coupling electrodes in a one-to-one correspondence.

[0012] For the grid capacitance sensor according to the present invention, preferably, the first pitch is a standard pitch, and the second pitch is offset based on the standard pitch.

[0013] For the grid capacitance sensor according to the present invention, preferably, the first pitch and the second pitch are respectively increased and decreased by the same amount based on the standard pitch.

[0014] For the grid capacitance sensor according to the present invention, preferably, the difference between the first pitch and the second pitch is not less than 1% of the standard pitch and not greater than 25% of the standard pitch.

[0015] For the grid capacitance sensor according to the present invention, preferably, the difference between the first pitch and the second pitch is not greater than 2% of the standard pitch.

[0016] For the grid capacitance sensor according to the present invention, preferably, the first grid plate and the second grid plate are rectangular plates, and the second grid plate is configured to translate relative to the first grid plate.

[0017] For the grid capacitance sensor according to the present invention, preferably, the emitter array includes a plurality of strip-shaped emitters.

[0018] For the grid capacitance sensor according to the present invention, preferably, the first coupling electrode and the second coupling electrode are triangular, sinusoidal or trapezoidal.

[0019] For the grid capacitance sensor according to the present invention, preferably, the first grid plate and the second grid plate are circular plates, and the second grid plate is configured to rotate relative to the first grid plate.

[0020] For the grid capacitance sensor according to the present invention, preferably, the emitter array includes a plurality of concentric fan-shaped ring emitters.

[0021] For the grid capacitance sensor according to the present invention, preferably, the first coupling electrode is a first fan-shaped ring, the second coupling electrode is a second fan-shaped ring, and the first fan-shaped ring and the second fan-shaped ring are concentric.

[0022] On the other hand, the present invention provides an absolute position measuring device, which includes the grid capacitance sensor according to the present invention, and further includes:

[0023] A drive signal generation circuit for providing a drive signal to the emitter;

[0024] A first signal processing circuit for receiving the signal from the first receiving electrode and outputting a first signal;

[0025] A second signal processing circuit for receiving the signal from the second receiving electrode and outputting a second signal; and

[0026] A calculation device for respectively converting the first signal and the second signal into first position data and second position data of the emitter array within one pitch, and determining the absolute position of the moving grid plate relative to the fixed grid plate based on the first position data and the second position data.

[0027] For the absolute position measuring device according to the present invention, preferably, the calculation device includes a memory, and a look-up table or a calculation formula is pre-stored in the memory.

[0028] For the absolute position measuring device according to the present invention, preferably, the look-up table is obtained by segmentally measuring the positions within each pitch of the first coupling electrode and the second coupling electrode during the production process.

[0029] For the absolute position measuring device according to the present invention, preferably, the calculation formula is a difference spline curve approximation formula, which is obtained based on the position data of the two-way sensors at each position point within each pitch of the first coupling electrode and the second coupling electrode during the production process.

[0030] For the absolute position measuring device according to the present invention, preferably, it further includes a processor, which is configured to obtain the pitch encoded number based on the first position data, the second position data, and the look-up table or the calculation formula, and calculate the absolute position data L through the following formula n :

[0031] L n = A n + N n × M,

[0032] wherein, A n is the first position data, N n is the pitch coding number, and M represents the absolute displacement data of one pitch.

[0033] According to the absolute position measuring device of the present invention, preferably, the processor is further configured to convert the absolute position data into an absolute position value.

[0034] According to the absolute position measuring device of the present invention, preferably, the processor is further configured to correct the absolute position value.

[0035] Compared with the prior art, the advantages of the present invention are as follows:

[0036] 1) On the basis of inheriting the phase discrimination type capacitive grating technology for more than 30 years, the phase discrimination type incremental capacitive grating measuring device has good anti-interference ability, and the mature moving grating and fixed grating structures and production technology advantages are utilized to enhance the easy implementability of the technology and reduce the cost.

[0037] 2) Since the sensor structure with the same emitter drive and two-way interleaved electrode coupling method is adopted, the deficiencies of the two independent measurements, the corresponding signal processing circuits cannot be accurately matched, and the separated electrode layout cannot be miniaturized are avoided.

[0038] 3) By improving the shape of the coupling electrode plates, the two-way coupling electrode plates with the same or similar shapes are arranged in a variable pitch and misaligned manner in the measurement direction, and different pitches are encoded and distinguished according to the positions of the coupling electrode plates at the physical level; then, the single-chip microcomputer compares the measured two-way position values with the theoretical (set) corresponding values at each pitch position to identify the pitch code, and realizes the multi-pitch absolute measurement according to the combination of the pitch code and the position value within the current pitch. Since the shapes of the two-way coupling pole pieces are the same or similar, the same drive processing method is used, and the single-chip microcomputer software judges and identifies the pitch code, which can effectively avoid the deficiencies of the complex calculation and processing of the three different modes of signals relative to the reference signal that need to be synchronously modulated and controlled in the absolute capacitive grating sensor patent with the coarse, medium, and fine three-electrode array, reduce the product development difficulty, and improve the product qualification rate.

[0039] 4) Based on the technical characteristics that the shapes of the two-way coupling poles are the same or similar and the offset directions are opposite, the algebraic analysis and processing of the data of the equivalent change of the two-way pitch position is carried out to correct the position data within the pitch and eliminate the influence of abnormal data such as large numbers that occasionally appear in the high-resolution sampling, thereby improving the measurement accuracy. Brief Description of the Drawings

[0040] The embodiments of the present invention will be further described below with reference to the accompanying drawings, where:

[0041] Figure 1 is a schematic structural diagram of a capacitive grating sensor absolute position measurement device according to the first embodiment of the present invention;

[0042] Figure 2 is a top view of a moving grating plate according to the first embodiment of the present invention;

[0043] Figure 3 is a top view of a fixed grating plate according to the first embodiment of the present invention;

[0044] Figure 4 is a structural block diagram of chip 30 of the capacitive grating sensor absolute position measurement device according to the first embodiment of the present invention;

[0045] Figure 5 is a structural block diagram of the single-chip microcomputer of the capacitive grating sensor absolute position measurement device according to the first embodiment of the present invention;

[0046] Figure 6 is a working flow chart of the single-chip microcomputer according to the first embodiment of the present invention;

[0047] Figure 7 is a schematic diagram of an equivalent pulse width modulation square wave modulated by the ADSO signal mapped from the CLK512 signal and the ADSO signal according to the embodiment of the present invention;

[0048] Figure 8 is a schematic structural diagram of a capacitive grating sensor absolute position measurement device according to another embodiment of the present invention;

[0049] Figure 9 is a further working flow chart of the single-chip microcomputer according to the first embodiment of the present invention;

[0050] Figure 10 and Figure 11 shows top views of two fixed grating plates of a capacitive grating sensor according to the second embodiment of the present invention;

[0051] Figure 12 is a top view of the fixed grating plate and the moving grating plate of a circular capacitive grating sensor according to the third embodiment of the present invention;

[0052] Figure 13 is Figure 12 an enlarged view of a part of the shown moving grating plate; and

[0053] Figure 14 is Figure 12 an enlarged view of a part of the shown fixed grating plate. Detailed implementation manners

[0054] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below through specific embodiments with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0055] First Embodiment

[0056] See Figure 1 The structural schematic diagram of the absolute position measuring device of the capacitive grating sensor according to the first embodiment of the present invention as shown, which includes a capacitive grating sensor composed of a moving grating plate (also called "moving electrode plate" or "moving plate") 100 and a fixed grating plate (also called "fixed electrode plate" or "fixed plate") 200, and a signal processing chip (ASIC) 30. The moving grating plate 100 can move parallel to the fixed grating plate 200 in the plane where the moving grating plate 100 is located along its length direction (for example, the direction indicated by the arrow F in the figure), and the fixed grating plate 200 serves as a scale. The signal processing chip 30 can be arranged on the moving grating plate 100 or outside the moving grating plate 100. In an exemplary implementation, the moving grating plate 100 is arranged on a slide rail, and the fixed grating plate 200 is arranged on a fixed base. Combining Figure 2 The top view of the moving grating plate 100 of the first embodiment as shown, two receiving electrodes 101 and 102 are arranged on the moving grating plate 100 on both sides of and electrically isolated from the emitter 103. The pitch of the emitter 103 is L, which is called the standard pitch. The emitter 103 receives a multi-channel driving signal from the chip 30, and the multi-channel driving signal is, for example, an 8-channel driving signal. The embodiments of the present invention are described by taking the 8-channel driving signal as an example, but those skilled in the art can understand that the number of driving signals is not limited to this. For Figure 2 The emitter 103 as shown, within one standard pitch L thereof, includes 8 emitter pieces spaced apart from each other. Combining Figure 3Top view of the fixed grating 200 according to the first embodiment shown. Two rows of interleaved coupling poles 203 and 204 are provided on the fixed grating 200. The coupling poles 203 and 204 are electrically connected to their respective reflecting poles 201 and 202. Alternatively, the reflecting poles 201 and 202 are a single elongated electrode. Since the two rows of coupling poles are interleaved, capacitors can be formed with the emitter 103 respectively, that is, the two rows of coupling poles share the emitter 103. When the moving grating 100 is positioned in the horizontal direction and moves relative to the fixed grating 200, in the vertical direction perpendicular to the horizontal direction, the coupling poles 203 and 204 are always covered by the emitter 103, the reflecting pole 201 is always covered by the receiving pole 101, and the reflecting pole 202 is always covered by the receiving pole 102. Thus, when the ASIC 30 provides a driving signal to the emitter 103, a coupling signal can be generated on the coupling poles 203 and 204. Through the corresponding reflecting poles 201 and 202, this coupling signal further generates further coupling signals on the receiving poles 101 and 102 respectively, so as to reflect the driving signal from the emitter 103 to the receiving poles 101 and 102 via the coupling poles 203 and 204, the reflecting poles 201 and 202 respectively. The chip 30 receives the first signal and the second signal from the receiving poles 101 and 102 respectively for signal processing.

[0057] In the embodiment of the present invention, the pitches of the two rows of coupling poles are different. Therefore, the first signal and the second signal received by the chip are also different, and these signals all reflect the positional relationship between the moving grating and the fixed grating. Based on the comparison of these two signals, the absolute position of the moving grating relative to the fixed grating can be determined. At the physical level, different pitches are encoded and distinguished according to the positions where the coupling poles are located. For pitches with different encodings, the relative position deviation amounts of the two rows of coupling poles are also different. Electrically, the electrical coupling of each pitch has a relatively fixed coupling electrical phase difference. Therefore, based on the analysis of the first signal and the second signal, the pitch encoding number where it is located can be known.

[0058] For example, continue to refer to Figure 3 , in this first embodiment, the coupling poles 203 and 204 are triangular. The pitch between the coupling poles 203 is L1, and the pitch between the coupling poles 204 is L2, L1≠L2, P0, P1, P2, P3, P4, P5, P6, P7, P8… etc. ( Figure 1 P0, P1, P2, P3 are not marked in

[0059] In one implementation of this embodiment, L1 = L + 2Δ, L2 = L, and 2Δ is the deviation of the pitch of the coupling pole 203 compared to the standard pitch. In particular, in order to reduce the impact of excessive deviation of the coupling pole 203 on the linear error, in another implementation of this embodiment, L1 = L + Δ, L2 = L - Δ. Two-way reverse equal deviation arrangement is adopted, that is, one way is arranged at equal intervals with a +Δ deviation compared to the standard pitch L, and the other way is arranged at equal intervals with a -Δ deviation compared to the standard pitch L. For the two-way coupling poles, under the coupling of the common standard pitch emitter, relatively stable and uniform pitch identification data can be obtained, and the pitch code can be identified through simple calculation.

[0060] In the embodiment of the present invention, considering the interference between the two-way coupling poles, the pitch deviation of the two-way coupling poles cannot be too large. Preferably, it cannot exceed approximately 25% of the standard pitch, and more preferably, it does not exceed approximately 2% of the standard pitch. Considering the recognition degree again, the pitch deviation of the two-way coupling poles cannot be too small. Preferably, it is not less than approximately 1% of the standard pitch. For example, if a standard pitch corresponds to 512 counting pulses, that is, 512cp, then the pitch difference between the two-way coupling poles is preferably between 5cp and 128cp, and more preferably between 5cp and 10cp. Of course, when the processing accuracy of the sensor is relatively high (including the optimization and correction of the gate shape), it is not restricted by the above.

[0061] In the embodiment of the present invention, the emitter 103, the coupling pole 203, the reflector 201, and the receiver 101 form a first capacitive grating sensor, and the emitter 103, the coupling pole 204, the reflector 202, and the receiver 102 form a second capacitive grating sensor. The first capacitive grating sensor and the second capacitive grating sensor are two incremental capacitive grating sensors with a common emitter. Therefore, the existing phase discrimination type capacitive grating sensor signal processing technology can be used to process the two-way measurements respectively.

[0062] Figure 4 and Figure 5The structural block diagrams of the ASIC chip 30 and the single-chip microcomputer 40 of the capacitive grid sensor measuring device according to an embodiment of the present invention are respectively shown. The ASIC chip 30 integrates a crystal oscillator circuit 21, a clock frequency division circuit 22, a multi-channel driving and analog switch signal generation circuit 23 (hereinafter, the 8-channel driving and analog switch signal generation circuit is taken as an example for description. It should be noted that, in this embodiment, the 8-channel driving signals are used to drive the first capacitive grid sensor 11 and the second capacitive grid sensor 12), and two capacitive grid signal demodulation, amplification, filtering and comparison circuits (hereinafter also simply referred to as capacitive grid signal processing circuits or signal processing circuits) 301 and 302 (i.e., capacitive grid signal demodulation, amplification, filtering and comparison circuit 1 and capacitive grid signal demodulation, amplification, filtering and comparison circuit 2); the two capacitive grid signal processing circuits 301 and 302 respectively receive the output signal CSI1 from the first capacitive grid sensor 11 and the output signal CSI2 from the second capacitive grid sensor 12, and respectively output ADSO1 signal and ADSO2 signal to Figure 5 the single-chip microcomputer 40 therein; in addition, the clock frequency division circuit 22 outputs a square wave signal (referred to as CLK512 signal in the present invention) to Figure 5 the single-chip microcomputer 40 therein, which has the same period as the 8-channel driving signals out1-out8 (for example, 512T, where 1T represents the reciprocal of the chip operating frequency) and has a fixed phase difference with any one of the driving signals.

[0063] Figure 5 The single-chip microcomputer 40 therein includes two identical timers 401 and 402 (i.e., timer 1 and timer 2), a counting clock 42, a CPU 43, a RAM 44, a ROM 47, a display unit 45 and a serial port 46. Among them, the timer also includes a buffer ( Figure 5 not shown in the figure). The timer 401 receives the ADSO1 signal from the capacitive grid signal processing circuit 301 and the CLK512 signal from the clock frequency division circuit 22, and the timer 402 receives the ADSO2 signal from the capacitive grid signal processing circuit 302 and the CLK512 signal from the clock frequency division circuit 22.

[0064] The working process of the first capacitive grid sensor 11 is discussed below. The working process of the second capacitive grid sensor 12 is the same as that of the first one. The specific working process is as follows:

[0065] 1) In the ASIC chip 30, a clock signal is generated by the crystal oscillator circuit 21 and sent to the clock frequency division circuit 22; the clock frequency division circuit 22 performs frequency division processing on the clock signal and sends the generated clock signal to the 8-channel driving and analog switch signal generation circuit 23. The clock frequency division circuit 22 also outputs a square wave signal (CLK512 signal) with the same period as the 8-channel driving signals and a fixed phase difference from any one of the driving signals; the 8-channel driving and analog switch signal generation circuit 23 receives the signals from the clock frequency division circuit, and generates and outputs 8-channel driving signals for driving the first capacitive grid sensor 11.

[0066] After the 8-channel driving and analog switch signal generation circuit 23 outputs the 8-channel driving signals, the first capacitive grid sensor 11 performs the following processing:

[0067] The 8 emitter plates of the first capacitive grid sensor 11 respectively receive the 8-channel driving signals from the ASIC chip 30, and modulate the output voltage to generate periodic signals with different amplitudes (i.e., CSI1 signal) via the grid capacitance of the first capacitive grid sensor 11. Then, the first capacitive grid sensor 11 inputs the CSI1 signal into the ASIC chip 30.

[0068] 2) In the ASIC chip 30, the capacitive grid signal processing circuit 301 receives the CSI1 signal from the first capacitive grid sensor 11, and converts the CSI1 signal into an ADSO1 square wave signal (this square wave signal has the same signal period as the CLK 512 signal and an electrical phase angle related to the grid position) related to the position of the grid of the first capacitive grid sensor 11 (in this embodiment, it refers to the vertical projection position of the emitter 103 and the coupling pole 203) through demodulation, amplification, filtering and comparison operations, and outputs the ADSO1 signal. Those skilled in the art should understand that when the ADSO1 signal is phase-shifted by 360° electrical phase angle, it corresponds to one pitch in the first capacitive grid sensor 11 in space.

[0069] 3) In the single-chip microcomputer 40, the timer 401 of the single-chip microcomputer 40 receives the ADSO1 signal from the capacitive grid signal processing circuit 301 and the CLK512 signal from the clock frequency division circuit 22. In this embodiment, the timer 401 in the single-chip microcomputer 40 uses the clock frequency provided by the counting clock 42 as the counting frequency (i.e., counts the number of pulses of the counting clock 42), and counts according to the ADSO1 signal and the CLK512 signal. In this first embodiment (see Figure 6 ), the working process of the single-chip microcomputer is as follows:

[0070] 31) The timer 401 of the single-chip microcomputer 40 receives the ADSO1 signal and the CLK512 signal. When the timer 401 detects the rising edge of the CLK512 signal, it clears the count; when the timer 401 detects the rising edge of the ADSO1 signal, it writes the current count into the buffer, generates an interrupt flag signal at the same time and sends the interrupt flag signal to the CPU 43.

[0071] See Figure 7 The schematic diagram of the equivalent pulse width modulation square wave modulated by the ADSO signal mapped by the CLK512 signal and the ADSO signal (including the ADSO1 signal or the ADSO2 signal) as shown. The count written by the timer 401 into the buffer corresponds to a modulation pulse width of the equivalent pulse width modulation square wave (such as Figure 7 A1, A2... shown), and this count represents the position data of the gate of the first capacitive grating sensor 11 within one pitch, preferably the position equivalent. In addition, since the timer 401 / 402 counts at the clock frequency provided by the counting clock 42, different position equivalents with different resolutions can be obtained by setting different clock frequencies for the counting clock 42. For example, assuming that the clock frequency of the single-chip microcomputer 40 is 6 MHz and the operating frequency of the ASIC chip 30 is 153.6 KHz, the duration of the 512T signal period corresponding to one pitch of the first capacitive grating sensor 11 is 512x1 / 153.6x10 -3 seconds = 10 / 3x10 -3 seconds. Within this duration, the maximum count value of the timer 401 of the single-chip microcomputer 40 is (10 / 3x10 -3 ) / (1 / 6x10 -6 ) = 20000. Therefore, the position equivalent subdivision is increased by about 40 times compared with the original (i.e., 512). Assuming that one pitch of the capacitive grating sensor is 5.08 mm, the obtained position equivalent subdivision is 5.08 / 20000 = 0.000254 mm. Since the clock frequency in the single-chip microcomputer 40 can be set as needed, the position equivalent subdivision can be made several times to hundreds of times that of the original, so as to achieve the purpose of high resolution.

[0072] 32) After receiving the interrupt flag signal, the CPU 43 reads the data in the buffer, that is, the position equivalent of the gate of the first capacitive grating sensor 11 within one pitch, which is called the "first position equivalent", and this first position equivalent corresponds to the pitch position data of the first capacitive grating sensor 11.

[0073] Based on the same working process, the CPU 43 can read the position equivalent of the gate of the second capacitive grating sensor 11 within one pitch, which is called the "second position equivalent", and this second position equivalent corresponds to the pitch position data of the second capacitive grating sensor 12.

[0074] In the embodiment of the capacitive grating sensor measuring device described above, when the timer 401 / 402 generates an interrupt flag signal upon detecting the rising edge of the ADSO1 / ADSO2 signal and sends the interrupt flag signal to the CPU 43. Those skilled in the art should understand that the timer 401 / 402 can also generate an interrupt flag signal and send it to the CPU 43 when detecting the falling edge of the ADSO1 / ADSO2 signal or when detecting the rising edge or falling edge of the CLK512 signal. Therefore, in another embodiment, after receiving the interrupt flag signal triggered by the falling edge of the ADSO1 / ADSO2 signal, the rising edge of the CLK512, or the falling edge of the CLK512, the CPU 43 reads the data in the buffer and converts it into the absolute displacement value of the gate of the capacitive grating sensor 11 / 12 within one pitch.

[0075] In the embodiment of the capacitive grating sensor measuring device described above, the timer 401 / 402 controls the counting based on the rising edges of the CLK512 signal and the ADSO1 / ADSO2 signal. That is, when the timer 401 / 402 detects the rising edge of the CLK512 signal, the count is cleared; and when the timer 401 / 402 detects the rising edge of the ADSO1 / ADSO2 signal, the current count of the timer 401 / 402 is written into the buffer. However, Figure 7 It can be seen that in another embodiment, the timer 401 / 402 can also control the counting based on the falling edges of the CLK512 signal and the ADSO1 / ADSO2 signal. That is, when detecting the falling edge of the CLK512 signal, the count is cleared; when the timer 401 / 402 detects the falling edge of the ADSO1 / ADSO2 signal, the current count of the timer is written into the buffer. In this way, the position equivalent of the gate of the capacitive grating sensor 11 / 12 within one pitch can also be obtained. In the case of adopting this implementation method, the CPU 43 can read the data in the buffer according to the interrupt flag signal triggered by the rising edge / falling edge of the ADSO1 / ADSO2 signal or the rising edge / falling edge of the CLK512 signal and convert it into the absolute displacement value of the gate of the capacitive grating sensor 11 / 12 within one pitch.

[0076] In the embodiment of the capacitive grating sensor measuring device described above, the timers 401 / 402 in the single-chip microcomputer 40 continuously count at the clock frequency provided by the counting clock 42. In another embodiment, a timer can be used which starts counting from zero at the rising edge of the CLK512 signal at the clock frequency provided by the counting clock 42 and ends counting and writes the current count into the buffer when the rising edge of the ADSO1 / ADSO2 signal is detected (it should be understood that the counting can also be controlled according to the falling edges of the CLK512 signal and the ADSO1 / ADSO2 signal). The CPU 43 can read the data in the buffer according to the interrupt flag signal triggered by the rising edge / falling edge of the ADSO1 / ADSO2 signal or the rising edge / falling edge of the CLK512 signal and convert it into the absolute displacement value of the grating of the capacitive grating sensors 11 / 12 within one pitch. In yet another embodiment, a timer can be used which starts timing from zero when the rising edge of the CLK512 signal is detected and writes the current time into the buffer when the rising edge of the ADSO1 / ADSO2 signal is detected (alternatively, starts timing from zero when the falling edge of the CLK512 signal is detected and writes the current time into the buffer when the falling edge of the ADSO1 / ADSO2 signal is detected). After receiving the interrupt flag signal, the CPU 43 reads the data in the buffer, obtains the position equivalent of the grating of the capacitive grating sensors 11 / 12 within one pitch according to this data and the clock frequency (for example, multiplying the current time in the buffer by the clock frequency), and converts the position equivalent of the grating of the capacitive grating sensors 11 / 12 within one pitch into the absolute displacement value of the grating of the capacitive grating sensors 11 / 12 within one pitch. In yet another embodiment, a timer can also be used which writes the current count into the buffer when the rising edge of the CLK512 signal is detected, simultaneously generates an interrupt flag signal and sends the interrupt flag signal to the CPU 43, and the CPU 43 reads the data in the buffer after receiving the interrupt flag signal triggered by the rising edge of the CLK512 signal; when the rising edge of the ADSO1 / ADSO2 signal is detected, writes the current count into the buffer, also generates an interrupt flag signal and sends this interrupt flag signal to the CPU 43, and the CPU 43 reads the data in the buffer after receiving the interrupt flag signal triggered by the rising edge of the ADSO1 / ADSO2 signal, and subtracts these two data, so that the position equivalent of the grating of the capacitive grating sensors 11 / 12 within one pitch can also be obtained.

[0077] In the embodiment of the capacitive grating sensor measuring device described above, the timers 401 / 402 include buffers for temporarily storing counts. In another embodiment, the timers 401 / 402 may not use buffers. When the rising edge of the CLK512 signal is detected, the timers 401 / 402 clear the count; when the rising edge of the ADSO1 / ADSO2 signal is detected, the timers 401 / 402 directly send the current count to the CPU 43, and the CPU 43 converts this data into the absolute displacement value of the grating of the capacitive grating sensors 11 / 12 within one pitch.

[0078] Although not described in detail above, those skilled in the art should understand that the RAM 44 in the single-chip microcomputer 40 can be used to store the data used by the CPU 43 in the calculation process. For example, after receiving the interrupt flag signal, the CPU 43 stores the data in the buffer into the RAM 44; or stores the data directly sent by the timers 401 / 402 into the RAM 44, and then processes the data stored in the RAM 44 (for example, converts it into the absolute displacement value of the grating of the capacitive grating sensors 11 / 12 within one pitch). In the case of using an ARM single-chip microcomputer, the DMA path can directly store the data in the buffer into the RAM 44, and the CPU 43 can extract the most recently stored data from the RAM 44 according to the received interrupt flag signal for conversion processing.

[0079] When the clock frequency provided by the counting clock 42 is relatively high (that is, the resolution of the position equivalent of the grating of the capacitive grating sensors 11 / 12 obtained is relatively high), the position equivalent data obtained by timing or counting may be unstable and fluctuate. To reduce the influence of this fluctuation, in a further embodiment, the CPU 43 can perform digital filtering processing on the position equivalent before performing the conversion operation (for example, perform digital filtering by averaging 8 sets of data. For example, extract and average the 8 sets of position equivalents of the grating of the capacitive grating sensors 11 / 12 that were most recently stored from the RAM 44), so as to obtain relatively stable data at a high resolution, and then convert the data after performing the digital filtering processing to obtain the absolute position value of the grating of the capacitive grating sensors 11 / 12 within one pitch.

[0080] The above obtains the position data of two capacitive grating sensors within one pitch through sampling by the timer of the single-chip microcomputer. Those skilled in the art can understand that the position data within one pitch can also be obtained by reading the data output by the internal processing circuit of the chip. For example, a phase discrimination and counting circuit is set in the chip 30 for sampling. See Figure 8Schematic diagram of the structure of a capacitive grating sensor absolute position measurement device according to another embodiment of the present invention, including a moving grating plate 8100, a fixed grating plate 8200, a chip 830, and a single-chip microcomputer 840, which performs phase discrimination counting sampling in the chip 830.

[0081] If the displacement of the gate of the capacitive grating sensor 11 / 12 exceeds one pitch, in order to obtain absolute position data, it is necessary to add the current pitch encoding number × pitch equivalent on the basis of the absolute position value within the previous pitch. Therefore, obtaining the current pitch encoding number is the problem to be solved below. In the embodiment of the present invention, the fixed grating pitch coupling pole is encoded starting from 0. Then, the coupling pole encoding that is coupled to the moving grating emitter at that time is the current pitch encoding. In one implementation manner of this first embodiment, the CPU 43 obtains the corresponding encoding of the pitch position by looking up a lookup table pre-stored in the ROM 47 based on the first position equivalent and the second position equivalent, and obtains the total absolute position equivalent L through calculation. n . Specifically, refer to Figure 9 the flowchart shown.

[0082] Step S410: Read the aforementioned first position equivalent A n and the second position equivalent B m .

[0083] Step S420: Read the lookup table pre-stored in the ROM 47. In this first embodiment, the coupling poles on the fixed grating plate include two reverse triangular electrodes, and the pitches of these two triangular electrodes are not equal. Therefore, as the pitch encoding increases, the distance between the two coupling poles also increases, as shown in Figure 3 . Based on this, the theoretical values of the position equivalents of the two-channel data at different pitches can be obtained through actual measurement of the positions segmented within each pitch during the production process. An example of the lookup table is shown in Table 1 below.

[0084] Table 1

[0085]

[0086] This lookup table is a two-dimensional table. The abscissa in the table is the value of channel 1 (i.e., the data of the sensor of channel 1), and the ordinate is the value of channel 2 (i.e., the data of the sensor of channel 2). When the moving grating is at the pitch position encoded as 0 and the output of channel 1 is A1, the output data of channel 2 is recorded as B1 at the same time, and the corresponding pitch encoding is 0; when the moving grating is at the pitch position encoded as 1 and the output of channel 1 is A1, the output data of channel 2 is recorded as B2 at the same time, and the corresponding pitch encoding is 1; and so on, until the pitch encoding data corresponding to channels 1 and 2 in the entire measurement range. A1, A2,..., A nare the position values of each position point within a single pitch with a pitch of 1, such as 0, 1, 2... 511, (or an equal number of intervals are taken). B1, B2, etc. are the output position values of the second path corresponding to the positions of A1, A2. In the embodiments of the present invention, for the first path sensor and the second path sensor, if the offset amounts of the coupling pole pitches of the two path sensors compared with the standard pitch are equal, any one of the sensors is arbitrarily designated as the first path sensor, and the other is the second path sensor; if the offset amounts of the coupling pole pitches of the two path sensors compared with the standard pitch are not equal, the sensor with the smaller offset amount is used as the first path sensor.

[0087] During actual measurement, the column number is determined by comparing the measured first position equivalent data with the abscissa data in the table (if tabulated at a large interval, rounding or interpolation processing is required), and the row number is determined by comparing the measured second position equivalent data with the ordinate data in the table (if tabulated at a large interval, rounding or compensation processing according to the interpolation number of the first path is required) to take the closest value. The data at the intersection of the row and column is the pitch encoding number N corresponding to the moving grating measurement position n , that is, the number of pitches by which the grating moves.

[0088] In another implementation manner of this first embodiment, the CPU 43 obtains the pitch position encoding number by means of formula calculation.

[0089] 1) Obtaining the formula: By reading the position values of each position point of the two path sensors within each pitch in the entire measurement range, and using the values of one path for pitch division. For example, taking the output value of the first path as the pitch resolution period, calculating the difference array of the positions with the same output value of the second path within the period, and then obtaining the approximate formula of the difference spline curve (a polynomial equation of one variable) by means of spline fitting according to the difference array. Each pitch has a corresponding difference formula. The formulas are numbered in the order of pitch arrangement and stored in the ROM 47 of the single-chip microcomputer 40.

[0090] 2) Obtaining by encoding recognition using the formula: According to the two path position point data read, calculating the actual difference between the two path position values within the period, and then inputting the values of the first path into each pitch formula to calculate the theoretical difference at this position of each pitch. Comparing the theoretical difference with the actual difference, taking the formula number corresponding to the theoretical difference when the deviation is the smallest, and the pitch position encoding can be obtained according to the formula number. In actual application, since the movement and change of the pitch are carried out in an orderly manner, the method of using the formula of the previous number and the formulas of the previous and next numbers for substitution can be adopted to quickly obtain the formula number corresponding to the theoretical difference when the deviation is the smallest, reducing the computing amount of the single-chip microcomputer.

[0091] Step S430: According to the pitch encoding number N n and the first position equivalent A n, perform the following calculations to obtain the absolute displacement equivalent L for more than one pitch n :

[0092] L n = A n + N n × M (1)

[0093] where M represents the resolution equivalent corresponding to each pitch (as described above, when the clock frequency provided by the counting clock 42 is 6 MHz, M = 20000).

[0094] Step S440: Convert the absolute displacement equivalent L of the gate of the capacitive grating sensor 10 n into an actual position value (or absolute position value).

[0095] Step S450: Correct the absolute position value. In the embodiment of the present invention, since the two-channel sensors have the same measurement parameter accuracy, the relative change data of the two channels (which should theoretically not differ much) can be compared to perform a certain average correction. For example, for the change data of the first position equivalent A n and the second position equivalent B m perform algebraic analysis processing, such as averaging or preferably selecting.

[0096] In a further embodiment, after obtaining the absolute position value, the CPU 43 also performs deviation correction on the absolute position value. For example, by using a standard measuring device for position calibration, sectional or point-by-point deviation correction can be performed to eliminate the influence of non-linear errors and moving grating manufacturing errors, so as to achieve high-precision measurement in the entire measurement range. For example, when the resolution equivalent within one pitch (i.e., the maximum count value of the timer within one pitch) is 20000, for a 5.08 mm pitch, the resolution reaches 0.000254 mm, that is, 254 nm. After linear coefficient interpolation correction in 8 equal segments (0.635 mm), estimated according to 4 times the uncertainty error, the accuracy can be within the range of 1 um, which is 10 times that of the original. According to needs, the same method can be used to correct all pitches within the measurement range respectively to obtain high-precision position values for the entire measurement range. (The correction compensation data is detected and obtained by a calibrator and stored in the storage unit of the single-chip microcomputer, and the measured actual position value is corrected for deviation according to the correction compensation data during measurement)

[0097] Step S460: Output the absolute position value to the display unit 45 and the serial port 46 for output by the display unit 45 and the serial port 46. In this way, high-resolution and high-precision large-range displacement measurement is achieved.

[0098] Second Embodiment

[0099] In the second embodiment, the shapes of the coupling poles 203 and 204 are improved. In the aforementioned first embodiment, the shape of the coupling pole is designed as a triangle in order to create space for movement in the measurement direction, facilitating the change of the physical position of the coupling pole relative to the standard position, thereby avoiding the overlapping interference of the two-way coupling pole pieces. Based on the triangular coupling poles arranged in reverse with different pitches for the two paths, a theoretical look-up table or calculation formula can be obtained. Based on this concept, in this second embodiment, the shape of the coupling pole is designed as a sine curve (as shown in Figure 10 ), or a trapezoid (as shown in Figure 11 ). Other designs are the same as those in the first embodiment and will not be elaborated here. The sine curve-shaped coupling pole and the trapezoid-shaped coupling pole have the same properties as the triangular coupling pole, except that the linearity of the position values coupled to is different (the change amount is not linear when measuring at different positions), and the offsettable position amounts are different. For example, the position offset amount of the triangle is relatively large, but the linearity is worse. The position offset amount of the sine curve is smaller, but the linearity is better. In practical applications, the shape of the coupling pole can be selected according to needs.

[0100] Third Embodiment

[0101] In this third embodiment, the emitter 103, the receivers 101 - 102, the coupling poles 203 - 204, and the reflectors 201 - 202 shown in Figures 1-3 are fabricated on a circular grid plate, such as the circular moving grid plate 910 and the circular fixed grid plate 920 shown in Figure 12 . The moving grid plate 910 is provided with an emitter 9103 and receivers 9101 and 9102 arranged outside and inside the emitter 9103 respectively and electrically isolated from it. The angular pitch (also referred to as "pitch" in the present invention) of the emitter 9103 is Λ, the shape of the emitter is a sector ring, and all the sector ring-shaped emitters are concentric. Refer to the enlarged view of a part of the moving grid plate 910 shown in Figure 13 . The emitter 9103 receives multiplexed drive signals from the chip 30. The fixed grid plate 920 is provided with two concentric sector ring-shaped coupling poles 9203 and 9204 arranged in reverse and staggered. In the embodiments of the present invention, "concentric" sector rings mean that the arcs of all sector rings are concentric. The pitches of the two-way coupling poles are not equal. The coupling poles 9203 and 9204 are electrically connected to the reflectors 9201 and 9202 respectively, and the numbers 1 - 15 are pitch codes. In this embodiment, the reflectors 9201 and 9202 are respectively entire circular ring electrodes. Those skilled in the art can understand that the reflectors 9201 and 9202 can also be divided into reflector arrays as in the first embodiment, and each reflector in the array is respectively connected to a coupling pole. In particular, for a capacitive grating sensor with a non-integral circle, it is easier to distinguish by dividing the reflector into an array. For the sake of understanding, Figure 14 provides Figure 12An enlarged view of a part of the fixed grating plate 920 shown, where the coupling poles 9203 and 9204 are distinguished by different shadings respectively. It can be seen that the two circular arcs of the coupling pole 9203 and the two circular arcs of the coupling pole 9204 are concentric. The long arc of the coupling pole 9203 and the short arc of the coupling pole 9204 are distributed near the same arc, and the short arc of the coupling pole 9203 and the long arc of the coupling pole 9204 are distributed near another same arc. Therefore, in this embodiment, the shapes of the two paths of coupling poles are not exactly the same, but similar. When the moving grating plate 910 rotates relative to the fixed grating plate 920, the areas where the coupling poles 9203 and 9204 are located are always covered by the area where the emitter 9103 is located, the area where the reflector 9201 is located is always covered by the area where the receiver 9101 is located, and the area where the reflector 9202 is located is always covered by the area where the receiver 9102 is located. Thus, when the ASIC 30 provides a driving signal to the emitter 9103, coupling signals can be generated on the coupling poles 9203 and 9204. The coupling signals are reflected to the receivers 9101 and 9102 through the reflectors 9201 and 9202 respectively. In this third embodiment, two circular-shaped grating sensors with a common emitter are adopted. The pitch (angular pitch) design of the grating poles of the two paths of circular-shaped grating sensors is similar to the pitch design of the grating poles in the first and second embodiments. For example, a circumference of 360° is divided into 16 pitches, and each standard pitch is 22.5°. The pitches of the two paths of coupling poles in this third embodiment deviate based on the standard pitch of 22.5° so that the pitches of the two paths of coupling poles are different. For example, the pitch of the first path of coupling pole remains the standard pitch of 22.5°, while the pitch of the second path of coupling pole is offset to 22.7°. Or, the pitches of the two paths of coupling poles are offset in the opposite direction. For example, the pitch of the first path of coupling pole is 22.4° and the pitch of the second path of coupling pole is 22.6°. Based on such a design, the 16 pitches can be numbered, and a look-up table or a calculation formula can be obtained in advance and stored in the single-chip microcomputer. The chip 30 receives signals from the receivers 9101 and 9102 for signal processing, thereby obtaining the absolute angular position. Its specific working process is similar to the foregoing and will not be elaborated here.

[0102] According to other embodiments of the present invention, the grating plate provided with the coupling pole and the reflector is the moving grating plate, and the grating plate provided with the emitter and the receiver is the fixed grating plate.

[0103] The absolute position measuring device of the present invention has a unique value at each position and will not be lost due to power-off or movement during non-measurement. Based on a phase-detection type capacitive grating sensor, it applies a multi-channel active driving technology, adopts a common emitter driving, two-way staggered electrode coupling, and then reflects to two receiving electrodes respectively in a double-path reflective electrode coupling structure, forming two incremental capacitive grating sensors with a common emitter. By improving the shape of the coupling plates, such as isosceles triangles, trapezoids, sine curves, sector rings, etc., and arranging two identical or similar-shaped coupling plates in a variable pitch and misaligned manner in the measurement direction, different pitches are encoded and distinguished according to the position where the coupling plates are located at the physical level. Electrically, the electrical coupling of each pitch has a relatively fixed coupling electrical phase difference. Then, through the implementation means of large-scale integrated circuits, the phase signals within the pitch of the two incremental sensors are obtained respectively in a phase-detection manner and compared with the pitch measurement period. Utilizing the technical feature that the pitch phase signal has a one-to-one correspondence with the pitch displacement change amount of the capacitive grating, a processing unit with high-resolution sampling ability, such as a single-chip microcomputer, is used to perform equivalent fine decomposition and demodulation on the phase signal, obtain the position quantity corresponding to the sensor within a single pitch, and compare the two-way position quantity data with the theoretical data through the single-chip microcomputer to identify the pitch code. According to the combination of the pitch code and the position value within the current pitch, the absolute position data of the measurement is obtained, realizing absolute measurement within the measurement range. The two-way processing signals are precisely matched, with small errors, the processing method is simple, and the volume is small.

[0104] Those skilled in the art should understand that although the internal counting clock 42 of the single-chip microcomputer is used to implement the timing and counting of the timer in the above text, in other embodiments, the external clock of the single-chip microcomputer can also be used to provide the clock frequency. Additionally, although the ASIC chip and the single-chip microcomputer are described as examples above, that is, they are described as two separate components, in other embodiments, the single-chip microcomputer can also be integrated in the ASIC chip, or the ASIC chip can be integrated on the single-chip microcomputer, or the two can be integrated together, which can be integrated on the same chip or on multiple chips.

[0105] Those skilled in the art should also understand that in addition to the single-chip microcomputer, other digital processing devices with computing functions can also be used to implement the present invention.

[0106] In addition, although the present invention has been described above by taking a capacitive grating sensor that receives multiple (8-channel) drive signals as an example, it should be noted that a displacement sensor that receives one drive signal is also applicable to the present invention. In this case, the drive signal generation circuit 23 can only output one drive signal, and the CLK512 signal output by the clock frequency division circuit 22 has the same period and the same phase as the drive signal. In a further embodiment, the period or phase of the CLK512 signal and the drive signal may not be exactly the same. For example, the periods can be in a multiple relationship, the phases can be opposite, or have other corresponding relationships.

[0107] It should be noted that some exemplary methods are depicted as flowcharts. Although the flowcharts depict operations as being performed in sequence, it can be understood that many operations can be performed in parallel, simultaneously, or synchronously. Additionally, the order of the operations can be rearranged. The processing can terminate when the operations are completed, but can also have additional steps that are not included in the figures or embodiments.

[0108] The above methods can be implemented by hardware, software, firmware, middleware, pseudocode, hardware description language, or any combination thereof. When implemented in software, firmware, middleware, or pseudocode, the program code or code segments used to perform the tasks can be stored in a computer-readable medium, such as a storage medium, and the processor can execute the tasks.

[0109] It should be understood that exemplary embodiments implemented in software are typically encoded on some form of program storage medium or implemented on some type of transmission medium. The program storage medium can be any non-transitory storage medium, such as a disk (e.g., a floppy disk or a hard disk) or an optical disk (e.g., a compact disk read-only memory or "CD ROM"), and can be read-only or random access. Similarly, the transmission medium can be a twisted pair, a coaxial cable, an optical fiber, or some other suitable transmission medium known in the art.

[0110] Although the present invention has been described by way of preferred embodiments, the present invention is not limited to the embodiments described herein, and various changes and variations are also included without departing from the scope of the present invention.

Claims

1. A capacitive grating sensor, comprising: A first grating plate, on which a first coupling pole array with a first pitch including a plurality of first coupling poles, a first reflecting pole electrically connected to the plurality of first coupling poles, a second coupling pole array with a second pitch including a plurality of second coupling poles, and a second reflecting pole electrically connected to the plurality of second coupling poles are provided, and A second grating plate, on which an emitter array with a standard pitch including a plurality of emitter sub-arrays and a first receiving pole and a second receiving pole arranged on both sides of the emitter array and electrically isolated from it are provided. The emitter sub-array includes a plurality of emitter sheets. The first receiving pole is spatially opposite to the first reflecting pole, and the second receiving pole is spatially opposite to the second reflecting pole. Wherein, one of the first grating plate and the second grating plate is a fixed grating plate, and the other is a moving grating plate. The moving grating plate is configured to be able to move relative to the fixed grating plate. The shapes of the first coupling pole and the second coupling pole are the same or similar. The first coupling pole array and the second coupling pole array are arranged in a reverse interleaved manner and are opposite to the emitter array in space. The first pitch is not equal to the second pitch.

2. The capacitive grating sensor according to claim 1, wherein, The first reflecting pole includes an array composed of a plurality of first reflecting pole sheets, and the second reflecting pole includes an array composed of a plurality of second reflecting pole sheets. The plurality of first reflecting pole sheets are electrically connected to the plurality of first coupling poles in one-to-one correspondence, and the plurality of second reflecting pole sheets are electrically connected to the plurality of second coupling poles in one-to-one correspondence.

3. The capacitive grid sensor according to claim 1, wherein, The first pitch is the standard pitch, and the second pitch is offset based on the standard pitch.

4. The capacitive grid sensor according to claim 1, wherein, The first pitch and the second pitch are respectively increased and decreased by the same amount based on the standard pitch.

5. The capacitive grating sensor according to any one of claims 1-4, wherein, The difference between the first pitch and the second pitch is not less than 1% of the standard pitch and not greater than 25% of the standard pitch.

6. The capacitive grating sensor according to claim 5, wherein The difference between the first pitch and the second pitch is not greater than 2% of the standard pitch.

7. The capacitive grating sensor according to any one of claims 1-4, wherein, The first grating plate and the second grating plate are rectangular plates, and the second grating plate is configured to translate relative to the first grating plate.

8. The capacitive grating sensor according to claim 7, wherein, The emitter array includes a plurality of elongated emitters.

9. The capacitive grating sensor according to claim 8, wherein, The first coupling pole and the second coupling pole are triangular, sinusoidal or trapezoidal.

10. The capacitive grating sensor according to any one of claims 1-4, wherein, The first grating plate and the second grating plate are circular plates, and the second grating plate is configured to rotate relative to the first grating plate.

11. The capacitive grating sensor according to claim 10, wherein, The emitter array includes a plurality of concentric fan-shaped ring emitters.

12. The capacitive grid sensor according to claim 11, wherein, The first coupling pole is a first fan-shaped ring, the second coupling pole is a second fan-shaped ring, and the first fan-shaped ring and the second fan-shaped ring are concentric.

13. An absolute position measuring device, comprising the capacitive grating sensor according to any one of claims 1-12, further comprising: A drive signal generation circuit for providing a drive signal to the emitter; A first signal processing circuit for receiving the signal from the first receiving pole and outputting a first signal; A second signal processing circuit for receiving the signal from the second receiving pole and outputting a second signal; And A computing device is configured to convert the first signal and the second signal into first position data and second position data of the emitter array within one pitch respectively, and determine an absolute position of the moving grating relative to the fixed grating based on the first position data and the second position data.

14. The absolute position measuring device according to claim 13, wherein, The computing device includes a memory in which a look-up table or a calculation formula is pre-stored.

15. The absolute position measuring device according to claim 14, wherein, The look-up table is obtained by segmentally measuring the positions within each pitch of the first coupling pole and the second coupling pole during the production process.

16. The absolute position measuring device according to claim 14, wherein, The calculation formula is a difference spline curve approximation formula, which is obtained based on the position data of the two-way sensors at each position point within each pitch of the first coupling pole and the second coupling pole during the production process.

17. The absolute position measuring device according to claim 14 further includes a processor configured to obtain a pitch encoded number based on the first position data, the second position data, and the look-up table or calculation formula, and calculate the absolute position data L through the following formula n :[[]]END]] L n = A n + N n × M, Among them, A n is the first position data, N n is the pitch encoding number, and M represents the absolute displacement data of one pitch.

18. The absolute position measuring device according to claim 17, wherein, The processor is further configured to convert the absolute position data into an absolute position value.

19. The absolute position measuring device according to claim 18, wherein, The processor is further configured to correct the absolute position value.

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