A planar capacitive encoder

Abstract

The present invention relates to the field of encoder technology, and more particularly to a planar capacitive encoder comprising a stationary scale, a movable plate, an X-axis signal generator, a Y-axis signal generator, an X-axis incremental processing module, a Y-axis incremental processing module, and a control module. The present invention inputs phase-modulated X-axis excitation signals and Y-axis excitation signals to the X-axis electrode strips and the Y-axis electrode strips, respectively. When the movable plate and the stationary scale move relative to each other, the modulated signals undergo a phase shift. The phase-modulated signals of the X-axis read head assembly and the Y-axis read head assembly are sampled and demodulated, thereby outputting X-axis and Y-axis displacement information.

Description

Technical Field

[0001] The present invention relates to the technical field of encoders, and in particular to a planar capacitive encoder. Background Art

[0002] Linear encoders are widely used displacement sensors, particularly in machine tools and automation equipment. However, commonly used optical and magnetic grating encoders suffer from a significant drawback: they typically only output position information for one axis. For planar motion, requiring simultaneous X and Y position information, two linear encoders are required, arranged orthogonally. However, due to the displacement limitations of linear encoders in non-measurement directions—for example, the read head of an X-axis encoder is limited to a few millimeters in the Y direction, while the read head of a Y-axis encoder is limited to a few millimeters in the X direction—this solution is largely unsuitable for planar motion measurement. Summary of the Invention

[0003] The object of the present invention is to provide a planar capacitive encoder in view of the above-mentioned deficiencies in the prior art.

[0004] The object of the present invention is achieved by the following technical solution: A planar capacitive encoder includes a static scale, a movable plate, an X-direction signal generator, a Y-direction signal generator, an X-direction incremental processing module, a Y-direction incremental processing module and a control module;

[0005] The static scale is provided with M parallel and equally spaced X-direction electrode strips along the X-axis direction, and every N consecutive strip electrodes constitute an X-direction period;

[0006] The static scale is provided with m parallel and equally spaced Y-direction electrode strips along the Y-axis direction, and every n consecutive strip electrodes constitute a Y-direction period;

[0007] The X-direction signal generator is used to provide an X-direction excitation signal to the X-direction electrode strips; the Y-direction signal generator is used to provide a Y-direction excitation signal to the Y-direction electrode strips;

[0008] The movable plate is provided with an X-direction read head assembly and a Y-direction read head assembly; the X-direction incremental processing module is used to collect the sensing signal of the X-direction read head assembly and output a signal of a change in the incremental position of the X-direction read head assembly in the X-axis direction; the Y-direction incremental processing module is used to collect the sensing signal of the Y-direction read head assembly and output a signal of a change in the incremental position of the Y-direction read head assembly in the Y-axis direction;

[0009] The controller determines the incremental position of the movable plate according to the output of the X-direction incremental processing module and the output of the Y-direction incremental processing module.

[0010] The present invention is further configured such that a same Y-direction electrode strip is divided by M X-direction electrode strips; and the Y-direction electrode strips are spaced apart from the X-direction electrode strips.

[0011] The present invention is further configured such that the X-direction read head assembly includes a first X-direction read head and a second X-direction read head arranged antisymmetrically; a sinusoidal X-direction gap is provided between the first X-direction read head and the second X-direction read head; and the length of the X-direction gap is the same as the length of the X-direction period;

[0012] The Y-direction read head assembly includes a first Y-direction read head and a second Y-direction read head arranged antisymmetrically; a Y-direction gap in a sine wave shape is provided between the first Y-direction read head and the second Y-direction read head; the length of the Y-direction gap is the same as the length of the Y-direction period.

[0013] The present invention is further configured such that the X-direction incremental processing module includes an X-direction amplification module, an X-direction demodulation module, and an X-direction filtering module;

[0014] The sensing signal of the first X-direction read head and the sensing signal of the second X-direction read head are input to the X-direction amplification module; the X-direction amplification module outputs the X-direction mixed signal to the X-direction demodulation module; the X-direction demodulation module multiplies and demodulates the X-direction excitation signal and the X-direction mixed signal to obtain an X-direction demodulated signal; the X-direction filtering module performs low-pass filtering on the X-direction demodulated signal to obtain a change signal of the incremental position of the X-direction read head assembly in the X-axis direction;

[0015] The present invention is further configured such that the Y-direction incremental processing module includes a Y-direction amplification module, a Y-direction demodulation module, and a Y-direction filtering module;

[0016] The sensing signal of the first Y-direction read head and the sensing signal of the second Y-direction read head are input to the Y-direction amplification module; the Y-direction amplification module outputs the Y-direction mixed signal to the Y-direction demodulation module; the Y-direction demodulation module multiplies and demodulates the Y-direction excitation signal and the Y-direction mixed signal to obtain a Y-direction demodulation signal; the Y-direction filtering module performs low-pass filtering on the Y-direction demodulation signal to obtain a change signal of the incremental position of the Y-direction read head component in the Y-axis direction.

[0017] The present invention is further configured such that the static scale is provided with a plurality of X-direction excitation lines and a plurality of Y-direction excitation lines; the X-direction signal generator is connected to the X-direction electrode strips via the X-direction excitation lines; and the Y-direction signal generator is connected to the Y-direction electrode strips via the Y-direction excitation lines.

[0018] The present invention is further configured as follows: the static scale includes a first plate layer and a second plate layer; the X-direction electrode strips and the Y-direction electrode strips are both arranged on the first plate layer; the X-direction excitation lines and multiple Y-direction excitation lines are both arranged on the second plate layer; the X-direction electrode strips and the X-direction excitation lines are connected through metal through-holes; the Y-direction electrode strips and the Y-direction excitation lines are connected through metal through-holes.

[0019] The present invention is further configured such that the number of the X-direction excitation lines is 2N, and the lines are evenly divided into groups of N first X-direction excitation lines and second X-direction excitation lines; the first X-direction excitation lines and the second X-direction excitation lines are respectively located above and below the X-direction electrode strips.

[0020] The present invention is further configured such that the number of the X-direction excitation lines is 2n and they are evenly divided into n groups of first Y-direction excitation lines and second Y-direction excitation lines; the first Y-direction excitation lines and the second Y-direction excitation lines are respectively located to the left and right of the Y-direction electrode strips.

[0021] The present invention is further configured such that the movable plate is provided with a first encoding head and a second encoding head; the planar capacitive encoder also includes a first absolute processing module and a second absolute processing module; the first absolute processing module is used to output a signal of a binary code string of the absolute position of the first encoding head; the second absolute processing module is used to output a signal of a binary code string of the absolute position of the second encoding head; the controller determines the incremental position of the movable plate based on the output of the absolute position of the first encoding head and the output of the absolute position of the second encoding head.

[0022] Beneficial effects of the present invention: The present invention inputs phase-modulated X-direction excitation signals and Y-direction excitation signals to the X-direction electrode strips and the Y-direction electrode strips respectively. When the movable plate and the static scale move relative to each other, the phase of the modulated signal changes. The phase modulated signals of the X-direction read head assembly and the Y-direction read head assembly are sampled and demodulated respectively, and the displacement information in the X-direction and Y-direction directions can be output. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention is further described with reference to the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the invention. A person skilled in the art can obtain other drawings based on the following drawings without making any creative effort.

[0024] Figure 1 Schematic diagram of the structure of the static scale of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of the static scale, X-axis read head assembly and Y-axis read head assembly of the present invention;

[0026] Figure 3 It is a structural schematic diagram of the movable plate of the present invention;

[0027] Figure 4 is a system block diagram of the present invention;

[0028] Figure 5 It is a system block diagram of the X-direction incremental processing module of the present invention;

[0029] Figure 6 It is a system block diagram of the Y-axis incremental processing module of the present invention;

[0030] Figure 7 This is a schematic diagram of the structure of the static scale after binary coding of the present invention;

[0031] Wherein: 1. static scale; 11. X-axis electrode strips; 12. Y-axis electrode strips; 2. movable plate; 21. first X-axis reader; 22. second X-axis reader; 23. first Y-axis reader; 24. second Y-axis reader; 25. first encoding reader; 26. second encoding reader; 3. X-axis signal generator; 4. Y-axis signal generator; 5. X-axis incremental processing module; 51. X-axis amplification module; 52. X-axis demodulation module; 53. X-axis filtering module; 6. Y-axis incremental processing module; 61. Y-axis amplification module; 62. Y-axis demodulation module; 63. Y-axis filtering module; 71. X-axis excitation line; 711. first X-axis excitation line; 712. second X-axis excitation line; 72. Y-axis excitation line; 721. first Y-axis excitation line; 722. second Y-axis excitation line; 8. controller; 91. first absolute processing module; 92. second absolute processing module. DETAILED DESCRIPTION

[0032] The present invention is further described with reference to the following examples.

[0033] Depend on Figures 1 to 7 It can be seen that the planar capacitive encoder described in this embodiment includes a static scale 1, a movable plate 2, an X-direction signal generator 3, a Y-direction signal generator 4, an X-direction incremental processing module 5, a Y-direction incremental processing module 6, and a control module;

[0034] The static scale 1 is provided with M parallel and equally spaced X-direction electrode strips 11 along the X-axis direction, and each X-direction electrode strip 11 has the same dimensions; each N consecutive strip electrodes constitute an X-direction period; wherein M is an integer greater than or equal to 4, and N is an integer greater than or equal to 1;

[0035] The static scale 1 is provided with m parallel and equally spaced Y-direction electrode strips 12 along the Y-axis direction. The Y-direction electrode strips 12 are arranged perpendicular to the X-direction electrode strips 11. The dimensions of each Y-direction electrode strip 12 are the same. Every n consecutive strip electrodes constitute a Y-direction period. Wherein m is an integer greater than or equal to 4, and n is an integer greater than 1.

[0036] The X-direction signal generator 3 is used to provide an X-direction excitation signal to the X-direction electrode strips 11; the Y-direction signal generator 4 is used to provide a Y-direction excitation signal to the Y-direction electrode strips 12;

[0037] The movable plate 2 is provided with an X-direction read head assembly and a Y-direction read head assembly; the X-direction incremental processing module 5 is used to collect the sensing signal of the X-direction read head assembly and output a signal of a change in the incremental position of the X-direction read head assembly in the X-axis direction; the Y-direction incremental processing module 6 is used to collect the sensing signal of the Y-direction read head assembly and output a signal of a change in the incremental position of the Y-direction read head assembly in the Y-axis direction;

[0038] The controller 8 determines the incremental position of the movable plate 2 according to the output of the X-direction incremental processing module 5 and the output of the Y-direction incremental processing module 6 .

[0039] Specifically, for the convenience of description, the planar capacitive encoder described in this embodiment sets the number of M to 12, the number of N to 4, the number of m to 12, and the number of n to 4. That is, by providing 12 X-direction electrode strips 11 and 12 Y-direction electrode strips 12, 4 adjacent X-direction electrode strips 11 form an X-direction period, and 4 adjacent Y-direction electrode strips 12 form an X-direction period;

[0040] The X-direction excitation signal is evenly divided into several phase shifts according to the X-direction period. Taking four X-direction electrode strips 11 as an example to form one period, the phase shifts corresponding to the excitation signal on each X-direction electrode strip 11 are 0, 90, 180 and 270 degrees respectively, that is, each phase shift is 90 degrees;

[0041] Similarly, the Y-direction excitation signal is evenly divided into several phase offsets according to the Y-direction period. Taking four Y-direction electrode strips 12 as an example to form a period, the phase offsets corresponding to the excitation signal on each Y-direction electrode strip 12 are 0, 90, 180 and 270 degrees, that is, each phase differs by 90 degrees.

[0042] During the movement of the movable plate 2, the X-direction read head assembly outputs a sensing signal, and the X-direction incremental processing module 5 is used to collect the sensing signal of the X-direction read head assembly and output a signal of a change in the incremental position of the X-direction read head assembly in the X-axis direction; the Y-direction read head assembly outputs a sensing signal, and the Y-direction incremental processing module 6 is used to collect the sensing signal of the Y-direction read head assembly and output a signal of a change in the incremental position of the Y-direction read head assembly in the Y-axis direction. The controller 8 can determine the incremental position of the movable plate 2 based on the output of the X-direction incremental processing module 5 and the output of the Y-direction incremental processing module 6.

[0043] In this embodiment, phase-modulated X-direction excitation signals and Y-direction excitation signals are input to the X-direction electrode strips 11 and the Y-direction electrode strips 12, respectively. When the movable plate 2 and the static scale 1 move relative to each other, the phase of the modulated signals changes. The phase modulated signals of the X-direction read head assembly and the Y-direction read head assembly are sampled and demodulated, respectively, to output the displacement information in the X and Y directions.

[0044] In the planar capacitive encoder described in this embodiment, a single Y-axis electrode strip 12 is divided by M X-axis electrode strips 11; the Y-axis electrode strips 12 and the X-axis electrode strips 11 are spaced apart. By dividing the single Y-axis electrode strip 12 by M X-axis electrode strips 11, the Y-axis electrode strips 12 and the X-axis electrode strips 11 can be arranged on the same plane, facilitating signal sensing by the X-axis read head assembly and the Y-axis read head assembly. The spaced apart Y-axis electrode strips 12 and the X-axis electrode strips 11 ensure that the Y-axis electrode strips 12 and the X-axis electrode strips 11 are not short-circuited with each other.

[0045] In the present embodiment, a planar capacitive encoder is described, wherein the X-direction read head assembly includes a first X-direction read head 21 and a second X-direction read head 22 arranged antisymmetrically; a sinusoidal X-direction gap is provided between the first X-direction read head 21 and the second X-direction read head 22; the length of the X-direction gap is the same as the length of the X-direction period; the Y-direction read head assembly includes a first Y-direction read head 23 and a second Y-direction read head 24 arranged antisymmetrically; a sinusoidal Y-direction gap is provided between the first Y-direction read head 23 and the second Y-direction read head 24; the length of the Y-direction gap is the same as the length of the Y-direction period. In the planar capacitive encoder described in this embodiment, the X-direction incremental processing module 5 includes an X-direction amplification module 51, an X-direction demodulation module 52, and an X-direction filtering module 53; the sensing signal of the first X-direction read head 21 and the sensing signal of the second X-direction read head 22 are input to the X-direction amplification module 51; the X-direction amplification module 51 outputs an X-direction mixed signal to the X-direction demodulation module 52; the X-direction demodulation module 52 multiplies and demodulates the X-direction excitation signal and the X-direction mixed signal to obtain an X-direction demodulated signal; the X-direction filtering module 53 performs low-pass filtering on the X-direction demodulated signal to obtain a signal of a change in the incremental position of the X-direction read head assembly in the X-axis direction; In the planar capacitive encoder described in this embodiment, the Y-direction incremental processing module 6 includes a Y-direction amplification module 61, a Y-direction demodulation module 62, and a Y-direction filtering module 63. The sensing signal of the first Y-direction read head 23 and the sensing signal of the second Y-direction read head 24 are input to the Y-direction amplification module 61. The Y-direction amplification module 61 outputs a Y-direction mixed signal to the Y-direction demodulation module 62. The Y-direction demodulation module 62 multiplies and demodulates the Y-direction excitation signal and the Y-direction mixed signal to obtain a Y-direction demodulation signal. The Y-direction filtering module 63 performs low-pass filtering on the Y-direction demodulation signal to obtain a signal indicating the change in the incremental position of the Y-direction read head assembly in the Y-axis direction. In the planar capacitive encoder described in this embodiment, the static scale 1 is provided with multiple X-direction excitation lines 71 and multiple Y-direction excitation lines 72. The X-direction signal generator 3 is connected to the X-direction electrode strips 11 via the X-direction excitation lines 71. The Y-direction signal generator 4 is connected to the Y-direction electrode strips 12 via the Y-direction excitation lines 72.

[0046] Specifically, for the convenience of description, the planar capacitive encoder described in this embodiment sets the number of M to 12, the number of N to 4, the number of m to 12, and the number of n to 4. That is, by providing 12 X-direction electrode strips 11 and 12 Y-direction electrode strips 12, 4 adjacent X-direction electrode strips 11 form an X-direction period, and 4 adjacent Y-direction electrode strips 12 form an X-direction period;

[0047] The X-direction excitation signal is evenly divided into several phase offsets according to the X-direction period. Taking four X-direction electrode strips 11 as an example to form a period, the phase offsets corresponding to the excitation signal on each X-direction electrode strip 11 are 0, 90, 180, and 270 degrees, that is, each phase difference is 90 degrees. The four X-direction excitation lines 71 are connected to every four X-direction electrode strips 11. On the one hand, these four excitation signals are transmitted to the corresponding X-direction electrode strips 11 through the X-direction excitation lines 71 on the static scale 1. On the other hand, the sinusoidal signals with phases of 0 and 90 degrees (i.e., sine and cosine signals) are simultaneously transmitted to the X-direction demodulation module 52.

[0048] Similarly, the Y-direction excitation signal is evenly divided into several phase offsets according to the Y-direction period. Taking four Y-direction electrode strips 12 as an example to form a period, the phase offsets corresponding to the excitation signal on each Y-direction electrode strip 12 are 0, 90, 180 and 270 degrees, that is, each phase difference is 90 degrees. The four Y-direction excitation lines 72 are connected to every four Y-direction electrode strips 12.

[0049] by Figure 1 Schematic static scale 1: X-axis electrode strip 11 is represented by blue, and the color depth changes from dark to light as X1, X2, X3, and X4 are connected. Four is a cycle, and the number of cycles can be increased according to the length. X1 to X4 are connected by X-axis excitation signals with the same frequency fx and a phase difference of 90°, which can be expressed by a sine function:

[0050] X1: sin(2πfx*t);

[0051] X2: sin(2πfx*t+90°)

[0052] X3: sin(2πfx*t+180°)

[0053] X4: sin(2πfx*t+270°);

[0054] The Y-direction electrode strips 12 are represented by green and occupy the blank spaces between the X-direction electrode strips 11. Similarly, the color depth changes from dark to light as Y1, Y2, Y3, and Y4 are connected. Four constitute a cycle, and the number of cycles can be increased according to the length. Y1 to Y4 are connected by the Y-direction excitation signal with the same frequency fy and a 90° phase difference, which can be expressed by a sine function:

[0055] Y1: sin(2πfy*t);

[0056] Y2: sin(2πfy*t+90°)

[0057] Y3: sin(2πfy*t+180°)

[0058] Y4: sin(2πfy*t+270°).

[0059] In order to realize differential signal sampling, the X-direction read head assembly adopts a first X-direction read head 21 and a second X-direction read head 22 with anti-symmetric shapes, such as Figure 3 The first X-axis read head 21 (with a + sign marked in the pattern area) and the second X-axis read head 22 (with a - sign marked in the pattern area) shown are each capable of inducing charge through the corresponding area of ​​the electrode strips on the static scale 1; a sinusoidal X-axis gap is provided between the first X-axis read head 21 and the second X-axis read head 22, and the length of the X-axis gap is the same as the length of the X-axis period, so that the sinusoidal X-axis gap is the same as the period of the X-axis electrode strips 11. When the X-axis read head assembly has a relative displacement with the static scale 1, without loss of generality, this displacement can be converted into a phase angle within one period.

[0060] The sensing signal that can be sensed by the first X-direction reading head 21 is:

[0061] ; Where fx is the frequency of the X-direction excitation signal, K is a constant, The first X-direction read head 21 performs an angular phase shift on the X-direction excitation signal of frequency fx; It can be considered that the first X-direction read head 21 multiplies the Y-direction excitation signal by a position-related function Y(x,y);

[0062] The sensing signal of the second X-direction reading head 22 is:

[0063] ; Where fx is the frequency of the X-direction excitation signal, K is a constant, The second X-direction read head 22 performs an angular phase shift on the X-direction excitation signal of the frequency fx; It can be considered that the second X-direction read head 22 multiplies the Y-direction excitation signal by a position-related function Y'(x, y).

[0064] The X-direction amplification module 51 converts the signal With signal After subtraction and mixing, a mixed signal is obtained; then the sine excitation signal and the cosine excitation signal of the X-direction excitation signal are multiplied with the mixed signal for demodulation, and finally low-pass filtering is performed to obtain the signal and signals .

[0065] In this embodiment, the two differentially modulated signals A and A* are transmitted to the X-axis amplification module 51. Due to their weak signal amplitude, differential amplification is required to suppress common-mode noise and increase the signal amplitude to hundreds to thousands of millivolts. The X-axis demodulation module 52 receives this amplified modulated signal and multiplies it with the excitation signal to separate the excitation signal and the displacement signal. The result of multiplication with the sinusoidal excitation signal includes the trigonometric function of twice the frequency of the excitation signal and the displacement signal. The cosine function (i.e. ), compared with a signal with twice the frequency of the excitation signal, is a DC quantity. Using a low-pass filter to remove the high-frequency component, we get Similarly, the amplified modulated signal is multiplied by the cosine excitation signal, and the resulting signal consists of a trigonometric function of twice the frequency of the excitation signal and a shift The sine function (i.e. ), compared with a signal with twice the frequency of the excitation signal, is a DC quantity. Using a low-pass filter to remove the high-frequency component, we get .

[0066] Get displacement After receiving the sine and cosine signals, the displacement of the movable plate 2 in the X-axis direction can be calculated by various methods. Some products on the market can directly accept this sine and cosine signal as the output of the encoder. This technology is quite mature, so this invention will not elaborate on how to convert the sine and cosine signals into displacement signals.

[0067] Similarly, in order to realize differential signal sampling, the Y-direction read head assembly adopts a first Y-direction read head 23 and a second Y-direction read head 24 with an anti-symmetric shape, as shown in FIG. Figure 3 The first Y-direction read head 23 (with a + sign marked in the pattern area) and the second Y-direction read head 24 (with a - sign marked in the pattern area) shown are shown. Each read head can induce charge through the corresponding area of ​​the electrode strip on the static scale 1. A sinusoidal Y-direction gap is provided between the first Y-direction read head 23 and the second Y-direction read head 24. The length of the Y-direction gap is the same as the length of the Y-direction period, so that the sinusoidal Y-direction gap is the same as the period of the Y-direction electrode strip 12. When the Y-direction read head assembly and the static scale 1 have a relative displacement, without loss of generality, this displacement can be converted into a phase angle in one period.

[0068] The sensing signal that can be sensed by the first Y-direction reading head 23 is:

[0069] ; Where fy is the frequency of the Y-direction excitation signal, k is a constant, The first Y-direction read head 23 performs an angular phase shift on the Y-direction excitation signal of frequency fy; It can be considered that the first Y-direction read head 23 multiplies the X-direction excitation signal by a position-related function X(x,y)

[0070] The sensing signal of the second Y-direction reading head 24 is:

[0071] ; Where fy is the frequency of the Y-direction excitation signal, K is a constant, The second Y-direction read head 24 performs an angular phase shift on the X-direction excitation signal of frequency fy; It can be considered that the second Y-direction read head 24 multiplies the X-direction excitation signal by a position-related function X'(x, y).

[0072] The Y-direction amplifying module 61 converts the signal With signal After subtraction and mixing, a mixed signal is obtained; then the sine excitation signal and the cosine excitation signal of the Y direction excitation signal are multiplied with the mixed signal for demodulation, and finally low-pass filtering is performed to obtain the signal and signals .

[0073] Get displacement After receiving the sine and cosine signals, the displacement of the movable plate 2 in the Y-axis direction can be calculated by various methods. Some products on the market can directly accept this sine and cosine signal as the output of the encoder. This technology is quite mature, so this invention will not elaborate on how to convert the sine and cosine signals into displacement signals.

[0074] In this embodiment of a planar capacitive encoder, the static scale 1 comprises a first plate layer and a second plate layer; the X-axis electrode strips 11 and the Y-axis electrode strips 12 are both provided on the first plate layer; the X-axis excitation lines 71 and the plurality of Y-axis excitation lines 72 are both provided on the second plate layer; the X-axis electrode strips 11 and the X-axis excitation lines 71 are connected via metal through-holes; and the Y-axis electrode strips 12 and the Y-axis excitation lines 72 are also connected via metal through-holes. This arrangement makes the overall structure more stable and reliable.

[0075] In the planar capacitive encoder described in this embodiment, the number of X-direction excitation lines 71 is 2N, and they are evenly divided into groups of N first X-direction excitation lines 711 and second X-direction excitation lines 712; the first X-direction excitation lines 711 and second X-direction excitation lines 712 are located above and below the X-direction electrode strips 11, respectively. In the planar capacitive encoder described in this embodiment, the number of X-direction excitation lines 71 is 2n, and they are evenly divided into groups of n first Y-direction excitation lines 721 and second Y-direction excitation lines 722; the first Y-direction excitation lines 721 and second Y-direction excitation lines 722 are located to the left and right of the Y-direction electrode strips 12, respectively. In the planar capacitive encoder described in this embodiment, the movable plate 2 is provided with a first encoding head 25 and a second encoding head 26; the planar capacitive encoder further includes a first absolute processing module 91 and a second absolute processing module 92; the first absolute processing module 91 is used to output a signal of a binary code string of the absolute position of the first encoding head 25; the second absolute processing module 92 is used to output a signal of a binary code string of the absolute position of the second encoding head 26; the controller 8 determines the incremental position of the movable plate 2 based on the output of the absolute position of the first encoding head 25 and the output of the absolute position of the second encoding head 26.

[0076] like Figure 7 As shown, to implement the absolute value mode, each X-direction electrode strip 11 is binary-coded. This can be distinguished by whether it is connected to the first X-direction excitation line 711 and the second X-direction excitation line 712 on the bottom or top. For example, a certain X-direction electrode strip 11 connected to the second X-direction excitation line 712 on the bottom is coded as 1, while a connection to the first X-direction excitation line 711 on the top is coded as 0. If the X4 excitation signals in the first cycle are connected from the top, the corresponding coding values ​​of the four X-direction electrode strips 11 in the first cycle are 1110, and so on. The coding value of the segment of X-direction electrode strips 11 shown in the figure is 111011010111.

[0077] Similarly, the first Y-direction excitation line 721 and the second Y-direction excitation line 722 can be respectively arranged on the left and right sides of the Y-direction electrode strip 12, so as to perform binary encoding of the Y-direction electrode strip 12. When connected to the first Y-direction excitation line 721 on the left, the encoding value of the Y-direction electrode strip 12 is 1, and when connected to the second Y-direction excitation line 722 on the right, the encoding value of the Y-direction electrode strip 12 is 0. As shown in the figure, the encoding of this segment of the Y-direction capacitance gate strip is 101101101011.

[0078] The first encoder reader 25 is used to read the code values ​​of the X-axis electrode strips 11. In principle, the first encoder reader 25 should correspond to one cycle of the X-axis electrode strips 11, that is, the pattern of four X-axis electrode strips 11. Its length and width can be slightly smaller than the width of the four X-axis electrode strips 11. For example, if the width of the cycle from X1 to X4 is 8 mm, the width of the first encoder reader 25 can be designed to be 7.5 mm.

[0079] When powered on, the order in which the excitation signals are loaded is controlled, with the lower X1 signal first passed through, followed by the upper X1 signal. If the first encoder reader 25 detects the lower excitation signal, it deems the barrier bar code value to be 1. If it detects the upper excitation signal, it deems the barrier bar code value to be 0. After X1 is passed, X2 is passed through, and this sequence is repeated until all four channels are passed through, at which point a four-bit code value can be detected.

[0080] The code value of the Y-direction electrode strip 12 can be obtained by the second code reader 26 in the same way. In this case, the left and right side excitation signals of Y1, Y2, Y3, and Y4 are passed in sequence to obtain the corresponding Y-direction code value.

[0081] In addition to the incremental mode, this embodiment performs binary encoding on the electrode strips of the static scale 1. The first encoding reader 25 and the second encoding reader 26 can detect the X-direction and Y-direction encoding of the corresponding position. When the system is powered on, the X-direction and Y-direction binary encoding of the corresponding position is detected, and the X-direction and Y-direction absolute positions corresponding to the encoding are found by looking up the table, thereby realizing absolute position output, which is the absolute addressing mode of the encoder.

[0082] After obtaining the absolute positions in the X and Y directions, the encoder switches to incremental mode, thus solving the problem of two-dimensional absolute position output for planar motion.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A planar capacitive encoder, characterized in that: It comprises a static scale (1), a movable plate (2), an X-direction signal generator (3), a Y-direction signal generator (4), an X-direction incremental processing module (5), a Y-direction incremental processing module (6) and a controller (8); The static grating ruler (1) is provided with M parallel X-direction electrode strips (11) arranged at equal intervals along the X-axis direction, and each N consecutive strip electrodes constitute an X-direction period; The static grating ruler (1) is provided with m parallel and equally spaced Y-direction electrode strips (12) along the Y-axis direction, and every n consecutive strip electrodes constitute a Y-direction period; The X-direction signal generator (3) is used to provide an X-direction excitation signal to the X-direction electrode strip (11); the Y-direction signal generator (4) is used to provide a Y-direction excitation signal to the Y-direction electrode strip (12); The movable plate (2) is provided with an X-direction reading head assembly and a Y-direction reading head assembly; the X-direction incremental processing module (5) is used to collect the sensing signal of the X-direction reading head assembly and output a signal indicating a change in the incremental position of the X-direction reading head assembly in the X-axis direction; the Y-direction incremental processing module (6) is used to collect the sensing signal of the Y-direction reading head assembly and output a signal indicating a change in the incremental position of the Y-direction reading head assembly in the Y-axis direction; The controller (8) determines the incremental position of the movable plate (2) according to the output of the X-direction incremental processing module (5) and the output of the Y-direction incremental processing module (6); The same Y-direction electrode strip (12) is divided and arranged by M X-direction electrode strips (11); the Y-direction electrode strip (12) and the X-direction electrode strip (11) are arranged at intervals; The X-direction reading head assembly comprises a first X-direction reading head (21) and a second X-direction reading head (22) that are arranged in an antisymmetrical manner; a sinusoidal X-direction gap is provided between the first X-direction reading head (21) and the second X-direction reading head (22); the length of the X-direction gap is the same as the length of the X-direction period; The Y-direction reading head assembly comprises a first Y-direction reading head (23) and a second Y-direction reading head (24) that are arranged in an antisymmetrical manner; a Y-direction gap in a sine wave shape is provided between the first Y-direction reading head (23) and the second Y-direction reading head (24); and the length of the Y-direction gap is the same as the length of the Y-direction period.

2. A planar capacitive encoder according to claim 1, characterized in that: The X-direction incremental processing module (5) includes an X-direction amplification module (51), an X-direction demodulation module (52), and an X-direction filtering module (53); The sensing signal of the first X-direction reading head (21) and the sensing signal of the second X-direction reading head (22) are input to an X-direction amplification module (51); the X-direction amplification module (51) outputs an X-direction mixed signal to an X-direction demodulation module (52); the X-direction demodulation module (52) multiplies and demodulates the X-direction excitation signal and the X-direction mixed signal to obtain an X-direction demodulation signal; the X-direction filtering module (53) performs low-pass filtering on the X-direction demodulation signal to obtain a change signal of the incremental position of the X-direction reading head component in the X-axis direction.

3. The planar capacitive encoder according to claim 1, wherein: The Y-direction incremental processing module (6) includes a Y-direction amplification module (61), a Y-direction demodulation module (62) and a Y-direction filtering module (63); The sensing signal of the first Y-direction reading head (23) and the sensing signal of the second Y-direction reading head (24) are input to a Y-direction amplification module (61); the Y-direction amplification module (61) outputs a Y-direction mixed signal to a Y-direction demodulation module (62); the Y-direction demodulation module (62) multiplies and demodulates the Y-direction excitation signal and the Y-direction mixed signal to obtain a Y-direction demodulation signal; the Y-direction filtering module (63) performs low-pass filtering on the Y-direction demodulation signal to obtain a change signal of the incremental position of the Y-direction reading head component in the Y-axis direction.

4. The planar capacitive encoder according to claim 1, wherein: The static grating scale (1) is provided with a plurality of X-direction excitation lines (71) and a plurality of Y-direction excitation lines (72); the X-direction signal generator (3) is connected to the X-direction electrode strip (11) via the X-direction excitation lines (71); and the Y-direction signal generator (4) is connected to the Y-direction electrode strip (12) via the Y-direction excitation lines (72).

5. A planar capacitive encoder according to claim 4, characterized in that: The static grating ruler (1) comprises a first plate layer and a second plate layer; the X-direction electrode strips (11) and the Y-direction electrode strips (12) are both arranged on the first plate layer; the X-direction excitation lines (71) and a plurality of Y-direction excitation lines (72) are both arranged on the second plate layer; the X-direction electrode strips (11) and the X-direction excitation lines (71) are connected via metal through-holes; the Y-direction electrode strips (12) and the Y-direction excitation lines (72) are connected via metal through-holes.

6. The planar capacitive encoder according to claim 5, wherein: The number of the X-direction excitation lines (71) is 2N, and the lines are evenly divided into groups of N first X-direction excitation lines (711) and second X-direction excitation lines (712); the first X-direction excitation lines (711) and the second X-direction excitation lines (712) are respectively located above and below the X-direction electrode strips (11).

7. The planar capacitive encoder according to claim 6, wherein: The number of the Y-direction excitation lines (72) is 2n, and they are evenly divided into n groups of first Y-direction excitation lines (721) and second Y-direction excitation lines (722); the first Y-direction excitation lines (721) and the second Y-direction excitation lines (722) are respectively located to the left and to the right of the Y-direction electrode strip (12).

8. The planar capacitive encoder according to claim 7, wherein: The movable plate (2) is provided with a first encoding head (25) and a second encoding head (26); the planar capacitive encoder further comprises a first absolute processing module (91) and a second absolute processing module (92); the first absolute processing module (91) is used to output a binary code string signal of the absolute position of the first encoding head (25); the second absolute processing module (92) is used to output a binary code string signal of the absolute position of the second encoding head (26); the controller (8) determines the incremental position of the movable plate (2) based on the output of the absolute position of the first encoding head (25) and the output of the absolute position of the second encoding head (26).

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