Planar capacitive encoder

Abstract

The invention relates to the technical field of encoders, in particular to a planar capacitive encoder which comprises a static grid ruler, a movable plate, an X-direction signal generator, a Y-direction signal generator, an X-direction increment processing module, a Y-direction increment processing module and a control module. An X-direction excitation signal and a Y-direction excitation signal which are subjected to phase modulation are input into an X-direction electrode strip and a Y-direction electrode strip respectively, when a movable plate and a static grid ruler move relatively, the phase of the modulation signals changes, the phase modulation signals of an X-direction reading head assembly and a Y-direction reading head assembly are sampled and demodulated respectively, and the phase modulation signals of the X-direction reading head assembly and the Y-direction reading head assembly are demodulated. And displacement information in the X direction and the Y direction can be output.

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, especially in machine tools and automation equipment. However, commonly used grating and magnetic grating encoders have an obvious shortcoming and problem, that is, they can generally only output the position displacement information of one axis. If it is a planar motion, that is, the position displacement information of X and Y needs to be output simultaneously, two sets of linear encoders are required to be arranged orthogonally. However, due to the displacement limitation of the linear encoder in the non-measurement direction, for example, the read head of the X-axis encoder is allowed to displace only a few millimeters in the Y direction, and the read head of the Y-axis encoder is allowed to displace only a few millimeters in the X direction, resulting in this solution basically cannot meet the requirements of 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 solutions: A planar capacitive encoder comprises 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 grating ruler is provided with M parallel and equally spaced X-direction electrode strips along the X-axis direction, and each N continuous strip electrodes constitute an X-direction period;

[0006] The static grating ruler 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 reading head assembly and a Y-direction reading head assembly; the X-direction incremental processing module is used to collect the sensing signal of the X-direction reading head assembly and output the change signal of the incremental position of the X-direction reading head assembly in the X-axis direction; the Y-direction incremental processing module is used to collect the sensing signal of the Y-direction reading head assembly and output the change signal of the incremental position of the Y-direction reading 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 the same Y-direction electrode strip is divided and arranged 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 reading head assembly comprises a first X-direction reading head and a second X-direction reading head which are arranged in an anti-symmetrical manner; a sinusoidal X-direction gap is provided between the first X-direction reading head and the second X-direction reading 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 which are arranged in an antisymmetrical manner; 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; and 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 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 reading head and the sensing signal of the second X-direction reading 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 the X-direction demodulation signal; the X-direction filtering module performs low-pass filtering on the X-direction demodulation signal to obtain the change signal of the incremental position of the X-direction reading head component in the X-axis direction;

[0015] The present invention is further configured 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 the Y-direction excitation signal and the Y-direction mixed signal to obtain the Y-direction demodulation signal; the Y-direction filtering module performs low-pass filtering on the Y-direction demodulation signal to obtain the 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 through the X-direction excitation lines; and the Y-direction signal generator is connected to the Y-direction electrode strips through 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 are connected to the X-direction excitation lines through metal through-holes; the Y-direction electrode strips are connected to the Y-direction excitation lines through metal through-holes.

[0019] The present invention is further configured such that the number of the X-direction excitation lines is 2N, and they 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 groups of n 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 according to 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 grating scale move relative to each other, the modulation signal undergoes a phase change, and the phase modulation signals of the X-direction reading head assembly and the Y-direction reading head assembly are sampled and demodulated respectively, so as to output displacement information in the X-direction and Y-direction directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention is further described using 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 creative work.

[0024] Figure 1 It is a schematic diagram of the structure of the static scale of the present invention;

[0025] Figure 2 It is a schematic diagram of the structure of the static scale, the X-axis reading head assembly and the Y-axis reading 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 grating ruler after binary coding of the present invention;

[0031] Wherein: 1. static scale; 11. X-axis electrode strip; 12. Y-axis electrode strip; 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 in conjunction with 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 grating ruler 1 is provided with M parallel X-direction electrode strips 11 arranged at equal intervals along the X-axis direction, and each X-direction electrode strip 11 has the same dimensions; each N continuous 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 grating ruler 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, and each Y-direction electrode strip 12 has the same dimensions, and each n continuous 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 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 the change signal of 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 the change signal of the incremental position of the Y-direction reading 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 setting 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 differs by 90 degrees;

[0041] Similarly, the Y-direction excitation signal is evenly divided into several phase shifts according to the Y-direction period. Taking four Y-direction electrode strips 12 constituting one period as an example, the phase shifts corresponding to the excitation signal on each Y-direction electrode strip 12 are 0, 90, 180 and 270 degrees respectively, 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 according to 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 modulation signal undergoes a phase change. The phase modulation signals of the X-direction read head assembly and the Y-direction read head assembly are sampled and demodulated respectively, and the displacement information of the X-direction and Y-direction can be output.

[0044] In the planar capacitive encoder described in this embodiment, the same Y-direction electrode strip 12 is divided and arranged by M X-direction electrode strips 11; the Y-direction electrode strip 12 is spaced apart from the X-direction electrode strip 11. By dividing the same Y-direction electrode strip 12 by M X-direction electrode strips 11, the Y-direction electrode strip 12 and the X-direction electrode strip 11 can be arranged on the same plane, which facilitates the X-direction read head assembly and the Y-direction read head assembly to sense signals; by spaced apart from the X-direction electrode strip 11, it is ensured that the Y-direction electrode strip 12 and the X-direction electrode strip 11 are not short-circuited with each other.

[0045] In the planar capacitive encoder described in this embodiment, the X-direction read head assembly includes a first X-direction read head 21 and a second X-direction read head 22 which are 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 which are 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 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 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 reader 23 and the sensing signal of the second Y-direction reader 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 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 of a change in the incremental position of the Y-direction reader assembly in the Y-axis direction. In the planar capacitive encoder described in this embodiment, the static 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 through the X-direction excitation line 71; the Y-direction signal generator 4 is connected to the Y-direction electrode strip 12 through the Y-direction excitation line 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 setting 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 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, that is, each phase difference is 90 degrees, and the four X-direction excitation lines 71 are connected to every four X-direction electrode strips 11 respectively; on the one hand, the 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, and on the other hand, the sinusoidal signals (i.e., sine and cosine signals) with phases of 0 and 90 degrees are simultaneously transmitted to the X-direction demodulation module 52;

[0048] Similarly, the Y-direction excitation signal is evenly divided into several phase shifts according to the Y-direction period. Taking four Y-direction electrode strips 12 constituting one period as an example, the phase shifts 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 respectively.

[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 with X1, X2, X3, and X4. Four is a cycle, and the number of cycles can be increased according to the length; X1 to X4 pass the X-axis excitation signal with the same frequency fx and a phase difference of 90°, which is represented 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 strip 12 is represented by green, occupying the blank gap between the X-direction electrode strips 11. Similarly, the color depth changes from dark to light with Y1, Y2, Y3, and Y4. Four constitute a cycle, and the number of cycles can be increased according to the length. Y1 to Y4 pass the Y-direction excitation signal with the same frequency fy and a phase difference of 90°, which is represented 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 of anti-symmetric shape, 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 in the figure can each induce charge through the corresponding area of ​​the electrode strip on the static grating 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 strip 11, and when the X-axis read head assembly has a relative displacement with the static grating scale 1, without loss of generality, this displacement can be converted into a phase angle in 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-axis excitation signal, K is a constant, The first X-direction reading head 21 performs an angular phase shift on the X-direction excitation signal of the frequency fx; It can be considered that the first X-direction reading 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-axis excitation signal, K is a constant, The second X-direction reading 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 reading 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 subtracting 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 the signal .

[0065] In this embodiment, the two differential modulation signals A and A* are transmitted to the X-direction amplification module 51. Since the signal amplitude is weak, differential amplification is required to suppress common mode noise and increase the signal amplitude to hundreds of millivolts to thousands of millivolts. The X-direction demodulation module 52 receives the amplified modulation signal and multiplies it with the excitation signal to separate the excitation signal and the displacement signal. The signal result 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. By 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 includes trigonometric functions of twice the frequency of the excitation signal and a displacement The sine function (i.e. ), compared with a signal with twice the frequency of the excitation signal, is a DC quantity. By using a low-pass filter to remove the high-frequency component, we get .

[0066] Get displacement After the sine and cosine signals are obtained, the displacement of the movable plate 2 in the X-axis direction can be solved 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 the present invention will not repeat how to convert the sine and cosine signals into displacement signals.

[0067] Similarly, in order to realize differential signal sampling, the Y-direction reading head assembly adopts a first Y-direction reading head 23 and a second Y-direction reading head 24 with an anti-symmetric shape, such as Figure 3 The first Y-axis read head 23 (with a + sign marked in the pattern area) and the second Y-axis read head 24 (with a - sign marked in the pattern area) shown in the figure can each induce charge through the corresponding area of ​​the electrode strip on the static grating scale 1; a sinusoidal Y-axis gap is provided between the first Y-axis read head 23 and the second Y-axis read head 24, and the length of the Y-axis gap is the same as the length of the Y-axis period, so that the sinusoidal Y-axis gap is the same as the period of the Y-axis electrode strip 12, and when the Y-axis read head assembly has a relative displacement with the static grating scale 1, 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-axis excitation signal, k is a constant, The first Y-direction reading head 23 performs an angular phase shift on the Y-direction excitation signal of the frequency fy; It can be considered that the first Y-direction read head 23 multiplies the X-direction excitation signal by a position-dependent 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-axis excitation signal, K is a constant, The second Y-direction reading 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 amplification module 61 converts the signal With signal After subtracting 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 the signal .

[0073] Get displacement After the sine and cosine signals are obtained, the displacement of the movable plate 2 in the Y-axis direction can be solved 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 the present invention will not repeat how to convert the sine and cosine signals into displacement signals.

[0074] In the planar capacitive encoder described in this embodiment, the static scale 1 includes 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 the plurality of Y-direction excitation lines 72 are both arranged on the second plate layer; the X-direction electrode strips 11 are connected to the X-direction excitation lines 71 through metal through-holes; the Y-direction electrode strips 12 are connected to the Y-direction excitation lines 72 through metal through-holes. The above arrangement makes the overall structure more stable and reliable.

[0075] In the planar capacitive encoder described in this embodiment, the number of the X-direction excitation lines 71 is 2N, and they are evenly divided into a first X-direction excitation line 711 and a second X-direction excitation line 712 in each group of N; the first X-direction excitation line 711 and the second X-direction excitation line 712 are respectively located above and below the X-direction electrode strip 11. In the planar capacitive encoder described in this embodiment, the number of the X-direction excitation lines 71 is 2n, and they are evenly divided into a first Y-direction excitation line 721 and a second Y-direction excitation line 722 in each group of n; the first Y-direction excitation line 721 and the second Y-direction excitation line 722 are respectively located to the left and to the right of the Y-direction electrode strip 12. 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 also 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 according to 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, in order to realize the absolute value mode, each X-direction electrode strip 11 is binary-coded, and can be distinguished by connecting the first X-direction excitation line 711 and the second X-direction excitation line 712 at the bottom or the top. For example, it is stipulated that a certain X-direction electrode strip 11 is connected to the second X-direction excitation line 712 at the bottom as code 1, and is connected to the first X-direction excitation line 711 at the top as code 0. The X4 excitation signal in the first cycle is connected from the top, and the corresponding code value of the four X-direction electrode strips 11 in the first cycle is 1110, and so on. The code 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 encoding head 25 is used to read the encoding value of the X-direction electrode strip 11. In principle, the first encoding head 25 should correspond to a pattern of one cycle of the X-direction electrode strip 11, that is, four X-direction electrode strips 11, and its length and width can be slightly smaller than the width of the four X-direction electrode strips 11. For example, the width of the cycle from X1 to X4 is 8 mm, and the width of the first encoding head 25 can be designed to be 7.5 mm.

[0079] When powered on, the order of loading the excitation signal is controlled, first the lower X1 signal is passed and then the upper X1 signal is passed. If the first encoding reader 25 detects the lower excitation signal, it considers that the barrier bar code value is 1. If it detects that the upper excitation signal is passed, it considers that the barrier bar code value is 0. After passing X1, pass X2, and continue in this order until all four channels are passed and a four-bit code value can be detected.

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

[0081] In addition to the incremental mode, the electrode strips of the static scale 1 are binary-encoded in this embodiment. The first encoding reader 25 and the second encoding reader 26 can detect the X-direction and Y-direction encodings of the corresponding positions. When the system is powered on, the X-direction and Y-direction binary encodings of the corresponding positions are detected, and the X-direction and Y-direction absolute positions corresponding to the encodings are found by looking up the table, so that the absolute position output can be realized, that 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 solution 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 solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution 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 control module; 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 continuous strip electrodes constitute an X-direction period; The static grating ruler (1) is provided with m parallel Y-direction electrode strips (12) arranged at equal intervals 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 the signal of the change of 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 the signal of the change of 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).

2. A planar capacitive encoder according to claim 1, characterized in that: 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.

3. A planar capacitive encoder according to claim 1, characterized in that: The X-direction reading head assembly comprises a first X-direction reading head (21) and a second X-direction reading head (22) which are arranged in an anti-symmetrical 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) which are arranged in an anti-symmetrical 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.

4. A planar capacitive encoder according to claim 3, characterized in that: The X-direction incremental processing module (5) comprises 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) performs multiplication demodulation on the X-direction excitation signal and the X-direction mixed signal to obtain an X-direction demodulation signal; and the X-direction filtering module (53) performs low-pass filtering on the X-direction demodulation signal to obtain a signal indicating a change in the incremental position of the X-direction reading head component in the X-axis direction.

5. A planar capacitive encoder according to claim 3, characterized in that: The Y-direction incremental processing module (6) comprises 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) performs multiplication demodulation on 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 a change in the incremental position of the Y-direction reading head component in the Y-axis direction.

6. A planar capacitive encoder according to claim 1, characterized in that: The static grating ruler (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).

7. A planar capacitive encoder according to claim 6, 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; and the Y-direction electrode strips (12) and the Y-direction excitation lines (72) are connected via metal through-holes.

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

9. A planar capacitive encoder according to claim 8, characterized in that: The number of the X-direction excitation lines (71) is 2n, and they are evenly divided into groups of n first Y-direction excitation lines (72) and second Y-direction excitation lines (72); the first Y-direction excitation lines (72) and the second Y-direction excitation lines (72) are respectively located on the left and right of the Y-direction electrode strips (12).

10. A planar capacitive encoder according to claim 9, characterized in that: The movable plate (2) is provided with a first encoding head (25) and a second encoding head (26); the planar capacitive encoder also 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 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) according to 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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