A two-degree-of-freedom linear displacement sensor and a method of measurement

Abstract

The application discloses a two-degree-of-freedom linear displacement sensor and a measuring method, and belongs to the technical field of measurement and sensing. The sensor comprises a dynamic ruler base body and a fixed ruler base body, the fixed ruler base body is provided with parallelogram excitation electrodes arranged along an x direction, and the dynamic ruler base body is provided with parallelogram sensing electrodes arranged along the x direction. The excitation electrodes and the sensing electrodes are arranged at a certain angle with the length direction of the fixed ruler base body; the displacement value solved by the output signal of the sensing electrodes is inversely deduced through a trigonometric function, and the real displacement value of the dynamic ruler base body when moving along the x direction and the y direction can be obtained. The excitation electrodes and the sensing electrodes are both arranged obliquely, the displacement values of the two rows of sensing electrodes are solved through a trigonometric function, and the displacement in the x direction and the y direction can be measured simultaneously. The sensor has a simple structure, one reading head can measure two directions simultaneously, and the offset error caused by linear measurement is effectively reduced.

Description

Technical Field

[0001] This invention relates to precision displacement measurement, specifically to a two-degree-of-freedom linear displacement sensor and measurement method, belonging to the field of measurement and sensing technology. Background Technology

[0002] Two-degree-of-freedom linear displacement measurement is a key fundamental technology in precision manufacturing, CNC machine tools, semiconductor equipment, and precision testing, and is widely used in scenarios such as table positioning, motion trajectory control, and multi-axis collaborative measurement. As equipment manufacturing develops towards higher precision, longer stroke, and higher reliability, higher requirements are placed on displacement sensors that can simultaneously achieve high-precision measurement in two orthogonal linear directions.

[0003] Currently, sensors used for two-degree-of-freedom linear displacement measurement mainly include grating sensors and magnetic grating sensors. Grating sensors acquire displacement information by etching periodic lines on a grating ruler and utilizing photoelectric conversion. They offer advantages such as high resolution and measurement accuracy. However, their measurement performance is limited by the grating manufacturing process, making it difficult to further improve the grating period and subdivision accuracy. Furthermore, the optical system has high requirements for installation accuracy and the working environment, and is susceptible to factors such as dust, oil, vibration, and temperature changes, leading to decreased system stability and reliability. In two-degree-of-freedom measurement applications, the integration of multi-channel optical systems further increases system complexity and assembly difficulty. Magnetic grating sensors achieve displacement measurement by utilizing the magnetic field change between a magnetic scale and a magnetic sensing element. They offer advantages such as simple structure and strong resistance to contamination. However, their measurement accuracy is limited by the magnetic pole period, magnetic field uniformity, and the performance of the magnetic sensing device, making it difficult to meet the requirements of high-precision two-degree-of-freedom displacement measurement. They are also susceptible to external magnetic field interference and temperature changes. Furthermore, in two-degree-of-freedom linear displacement measurement, existing grating and magnetic grating sensors typically require multiple sets of measurement units to work together, which not only increases the system size and cost, but also places high demands on installation parallelism and orthogonality, limiting their application in large-stroke, high-precision measurement applications.

[0004] In recent years, my country has developed an electric field-type time-grating linear displacement sensor based on a single-row multilayer structure (publication number CN103822571B). This sensor uses a high-frequency clock pulse as the measurement reference and obtains the required electric traveling wave signal through direct coupling with an alternating electric field constructed by a parallel plate capacitor, thereby extracting displacement information. This type of sensor possesses advantages such as non-contact measurement and high resolution to a certain extent, enabling high-precision displacement measurement over a relatively large range. However, the aforementioned displacement sensor still has certain shortcomings in practical applications. First, the sensor is susceptible to large-range errors due to installation limitations, and it cannot perform two-degree-of-freedom measurements, requiring large-range calibration correction using calibration equipment to reduce measurement errors.

[0005] In summary, existing two-degree-of-freedom linear displacement sensors still have shortcomings in terms of measurement accuracy, environmental adaptability, system complexity, and large stroke applications. There is an urgent need for a new sensor solution that is simple in structure, highly reliable, and suitable for two-degree-of-freedom linear displacement measurement. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a two-degree-of-freedom linear displacement sensor and measurement method. The sensor of this invention has a simple structure, can realize linear displacement measurement in the x-direction, and can also detect displacement value in the y-direction. It has high measurement accuracy, and one reading head can measure two directions simultaneously, effectively reducing the offset error caused by linear measurement.

[0007] The technical solution of this invention is implemented as follows:

[0008] A two-degree-of-freedom linear displacement sensor includes a movable scale base and a fixed scale base arranged parallel to each other with a gap between them. A row of excitation electrodes is uniformly arranged along the length direction on the upper surface of the fixed scale base. All excitation electrodes in this row are of the same shape and size, forming several phase excitation electrode groups. A row of sensing electrodes is uniformly arranged along the length direction on the lower surface of the movable scale base. All sensing electrodes in this row are of the same shape and size. The row of sensing electrodes on the movable scale base is directly opposite the row of excitation electrodes on the fixed scale base. All excitation electrodes in this row are parallelograms, with their base sides parallel to the length direction of the fixed scale base and a width of W1, a spacing of I1, and an angle α between adjacent sides of the excitation electrode's base and the length direction of the fixed scale base. All sensing electrodes in this row are parallelograms, with their base sides parallel to the length direction of the fixed scale base and a width of W. T1 The row of sensing electrodes contains at least two sensing electrodes, and the positions of two adjacent sensing electrodes differ by 2(W1+I1). The adjacent side of the bottom edge of the sensing electrode forms a certain angle with the length direction of the fixed-length base.

[0009] Furthermore, a second row of excitation electrodes is uniformly arranged along the length direction on the upper surface of the fixed-length substrate, and all excitation electrodes in the second row have the same shape and size; this row of excitation electrodes forms several phase excitation electrode groups; a second row of induction electrodes is uniformly arranged along the length direction on the lower surface of the moving-length substrate, and all induction electrodes in the second row have the same shape and size; the second row of induction electrodes on the moving-length substrate is directly opposite to the second row of excitation electrodes on the fixed-length substrate;

[0010] All excitation electrodes in the second row are parallelograms. The base of the second row of excitation electrodes is parallel to the length direction of the fixed-length substrate and has a width of W2. The spacing between them is I2. The angle between the adjacent sides of the base of the second row of excitation electrodes and the length direction of the fixed-length substrate is β. All induction electrodes in the second row are parallelograms. The base of the second row of induction electrodes is parallel to the length direction of the fixed-length substrate and has a width of W2. T2 In the second row of sensing electrodes, there are at least two sensing electrodes and the positions of two adjacent sensing electrodes differ by 2 (W2+I2). The adjacent side of the bottom edge of the sensing electrode forms a certain angle with the length direction of the fixed-length base.

[0011] Furthermore, the range of angles α and β is -180° to 180° and α-β≠kπ, where k is a positive integer.

[0012] Furthermore, the number of cycles of the two rows of excitation electrodes are coprime to achieve absolute positioning for displacement detection.

[0013] For a two-degree-of-freedom linear displacement sensor with only one row of excitation electrodes, during measurement, the same-frequency, equal-amplitude excitation signals with a phase difference of φ are sequentially and periodically applied to the same row of excitation electrodes on the fixed-scale base. At this time, the excitation electrodes on the fixed-scale base and the sensing electrodes on the moving-scale base form a capacitive structure. When the moving-scale base moves relative to the fixed-scale base, the sensing electrodes output a traveling wave signal related to the displacement. After the output traveling wave signal is processed by a signal processing circuit and the corresponding displacement is calculated, the displacement value x output by the sensing electrodes is obtained. 12 The direction is perpendicular to the adjacent side of the bottom edge of the excitation electrode in that row;

[0014] When the moving scale base moves relative to the fixed scale base along the x-direction, the displacement value X in the x-direction is obtained according to trigonometric relationships:

[0015]

[0016] When the moving scale base moves relative to the fixed scale base along the y-direction, the displacement value Y in the y-direction is obtained according to trigonometric relationships:

[0017]

[0018] For a two-degree-of-freedom linear displacement sensor with two rows of excitation electrodes, during measurement, excitation signals are applied to the two rows of excitation electrodes on the fixed scale base. At this time, the excitation electrodes on the fixed scale base and the corresponding sensing electrodes on the moving scale base form a capacitor structure. When the moving scale base moves relative to the fixed scale base, the two rows of sensing electrodes output traveling wave signals related to the displacement. After the two output traveling wave signals are processed by the signal processing circuit and the corresponding displacement calculation is performed, the displacement value x output by the first row of sensing electrodes is obtained. 12 The displacement value x output by the second row of sensing electrodes 21The directions are all perpendicular to the adjacent side of the bottom edge of the corresponding row excitation electrode;

[0019] Let the actual planar displacement d of the moving scale base relative to the fixed scale base be:

[0020]

[0021] X and Y are the displacement values ​​of the moving scale base relative to the fixed scale base along the x-direction and along the y-direction, respectively;

[0022] The displacement value x output by the first row of induction electrodes is obtained using trigonometric relationships. 12 The displacement value x output by the second row of sensing electrodes 21 for:

[0023]

[0024] Written in matrix form:

[0025]

[0026]

[0027] Solving the system of linear equations yields the displacement X along the x-direction and the displacement Y along the y-direction of the moving scale base relative to the fixed scale base:

[0028]

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] In this invention, both the excitation electrode and the sensing electrode are tilted. The displacement in the x and y directions can be measured separately through a single row of sensing electrodes. The sensor has a simple structure and can realize linear displacement measurement in the x direction as well as detect displacement value in the y direction. One reading head can measure two directions at the same time, effectively reducing the offset error caused by linear measurement.

[0031] In this invention, both the excitation electrode and the sensing electrode are arranged in two rows, which is equivalent to setting up two sets of displacement sensors. The excitation electrode and the sensing electrode of the two sensors share the corresponding fixed scale base and the moving scale base, and share the same set of processing circuits. The displacement value output by each row of sensing electrodes has a specific trigonometric function relationship with their respective displacements in the x and y directions. By solving the equations formed by the two sets of trigonometric function relationships, the final displacement values ​​of the sensor probe in the x and y directions can be obtained. In this way, the displacement calculation in the x and y directions can be realized when the moving scale moves in any direction, without significantly increasing the complexity of the sensor. Attached Figure Description

[0032] Figure 1This is a schematic diagram of the installation of the fixed-length base and the movable-length base in Example 1.

[0033] Figure 2 This is a schematic diagram showing the spatial correspondence between the fixed-length base and the movable-length base in Example 1.

[0034] Figure 3 This is a schematic diagram of the fixed-length base of Example 1.

[0035] Figure 4 This is a schematic diagram of the moving scale base of Example 1.

[0036] Figure 5 The displacement value x output by the two rows of inductive electrodes in Example 1 12 x 21 Diagram showing the x and y directions.

[0037] Figure 6 This is a schematic diagram of the spatial vector displacement calculation in the x and y directions of Example 1.

[0038] Figure 7 This is a schematic diagram of the moving ruler base in Example 2.

[0039] Figure 8 This is a schematic diagram of the fixed-length base of Example 3.

[0040] Figure 9 This is a schematic diagram of the moving ruler base in Example 4.

[0041] Figure 10 This is a schematic diagram of the fixed-length base of Example 5.

[0042] Figure 11 This is a schematic diagram of the moving ruler base in Example 6.

[0043] Figure 12 This is a schematic diagram showing the relationship between the number of two rows of excitation electrodes on the fixed-length substrate in Example 7.

[0044] Figure 13 This is a schematic diagram showing the relationship between the number of two rows of excitation electrodes on the fixed-length substrate in Example 8.

[0045] Figure 14 This is a schematic diagram showing the relationship between the number of two rows of excitation electrodes on the fixed-length substrate in Example 9.

[0046] Wherein, 1-fixed scale substrate; 1-1 excitation electrode; 2-moving scale substrate; 2-1 induction electrode. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0048] This invention discloses a two-degree-of-freedom linear displacement sensor, comprising a movable scale base 2 and a fixed scale base 1 arranged parallel to each other with a gap between them. A row of excitation electrodes 1-1 is uniformly arranged along the length direction on the upper surface of the fixed scale base 1, and all excitation electrodes in this row are of the same shape and size; this row of excitation electrodes forms several phase excitation electrode groups. A row of sensing electrodes 2-1 is uniformly arranged along the length direction on the lower surface of the movable scale base 2, and all sensing electrodes in this row are of the same shape and size; this row of sensing electrodes on the movable scale base is directly opposite to the row of excitation electrodes on the fixed scale base. All excitation electrodes 1-1 in this row of excitation electrodes are parallelograms, with their base sides parallel to the length direction of the fixed scale base and a width of W1, and a spacing of I1. The angle between the adjacent sides of the base of the excitation electrodes and the length direction of the fixed scale base is α; where α is -180° to 180°. All sensing electrodes 2-1 in this row of sensing electrodes are parallelograms, with their base sides parallel to the length direction of the fixed scale base and a width of W1. T1 The row of sensing electrodes contains at least two sensing electrodes, and the bottom edge width W of a single sensing electrode is... T1 The sum of the gaps between two adjacent sensing electrodes (also known as the position difference between two adjacent sensing electrodes) is equal to 2(W1+I1), and the adjacent side of the bottom edge of the sensing electrode forms a certain angle with the length direction of the fixed-length substrate.

[0049] During measurement, excitation signals of the same frequency and equal amplitude with a phase difference of φ are sequentially and periodically applied to the excitation electrodes on the fixed scale substrate. At this time, the excitation electrodes on the fixed scale substrate and the induction electrodes on the moving scale substrate form a capacitor structure. When the moving scale substrate moves relative to the fixed scale substrate, the induction electrodes output a traveling wave signal related to the displacement. The output traveling wave signal is then processed by a signal processing circuit, and after corresponding displacement calculations, the displacement value x output by the induction electrodes is obtained. 12 The direction is perpendicular to the adjacent side of the bottom edge of the excitation electrode in that row.

[0050] When the moving scale base moves relative to the fixed scale base along the x-direction, the displacement value X in the x-direction is obtained according to trigonometric relationships:

[0051]

[0052] When the moving scale base moves relative to the fixed scale base along the y-direction, the displacement value Y in the y-direction is obtained according to trigonometric relationships:

[0053]

[0054] This invention features parallelogram-shaped excitation and sensing electrodes arranged at an angle. Based on trigonometric function analysis, displacement in both the x and y directions can be measured using a single row of sensing electrodes. The sensor has a simple structure, enabling linear displacement measurement in the x-direction as well as detection of displacement in the y-direction. A single reading head can measure both directions simultaneously, effectively reducing offset errors introduced during linear measurements.

[0055] Since a single row of excitation and sensing electrodes can only measure displacement in a specific direction (i.e., along the x-direction or along the y-direction), to expand the sensor's adaptability and facilitate absolute positioning, the excitation electrodes on the fixed-scale substrate are further arranged in two rows, and the sensing electrodes on the movable-scale substrate are also arranged in two corresponding rows. Theoretically, the two rows of excitation and sensing electrodes are unrelated and perform displacement calculations independently. The displacement value output by each row of sensing electrodes has a specific trigonometric function relationship with its displacement in the x and y directions. By solving the system of equations formed by the two sets of trigonometric function relationships, the final displacement values ​​of the sensor probe along the x and y directions can be obtained. This allows for displacement calculation in the x and y directions when the movable scale moves in any direction without significantly increasing the complexity of the sensor. In addition, from the perspective of ease of manufacturing, the two rows of excitation electrodes and the two rows of sensing electrodes are identical in shape and number. Under the same conditions, there are two specific arrangement methods: Method 1: Symmetrically arranged relative to the centerline of the length direction of the fixed-scale substrate or the movable-scale substrate. Method 2: Two rows of excitation electrodes are arranged in parallel, spaced at a predetermined distance relative to the width of the fixed-length substrate and symmetrically positioned relative to the geometric center of the fixed-length substrate; two rows of induction electrodes are also arranged in parallel, spaced at a predetermined distance relative to the width of the moving-length substrate and symmetrically positioned relative to the geometric center of the moving-length substrate. Method 2 involves vertical translation.

[0056] The following example further illustrates the specific arrangement of the two rows of excitation electrodes and sensing electrodes. For details, please refer to [link to relevant documentation]. Figures 1-13 .

[0057] Example 1: As Figure 1 and Figure 2 As shown, a two-degree-of-freedom linear displacement sensor includes two parts: a fixed-scale base 1 and a movable-scale base 2. The movable-scale base and the fixed-scale base are installed in parallel with a certain gap.

[0058] like Figure 3 As shown, two rows of parallelogram-shaped excitation electrodes 1-1 of equal length and height are arranged on the fixed-length base 1, with equal spacing between each excitation electrode. The first row consists of n1 excitation electrodes, each with a width of W1 and a spacing of I1. The side of the excitation electrode in the first row forms an angle α with the horizontal (α is positive and its absolute value is less than 90°). Figure 3In the first row, α equals 45°; the second row consists of n2 excitation electrodes, each with a width of W2 and a spacing of I2. The side of the excitation electrode in the second row forms an angle β with the horizontal (β is negative and its absolute value is less than 90°). Figure 3 (where β equals -45°), where the number of excitation electrodes in the first row n1 on the fixed-length substrate is equal to the number of excitation electrodes in the second row n2, i.e., n1=n2=36.

[0059] like Figure 4 As shown, two rows of parallelogram-shaped sensing electrodes 2-1 of equal length and height are arranged on the moving ruler base 2. The first row has at least two sensing electrodes with a position difference of 2 (W1+I1), and each sensing electrode has a width of W. T1 The first row of sensing electrodes has a side edge that forms an angle α with the horizontal (α is positive and its absolute value is less than 90°); the second row has at least two sensing electrodes positioned 2(W² + I²) apart, each sensing electrode having a width of W. T2 The angle between the side of the second row of sensing electrodes and the horizontal is β (β is negative and its absolute value is less than 90°).

[0060] In Example 1, the excitation electrode and the sensing electrode are arranged in the manner described in Method 1.

[0061] In this invention, the length direction of the fixed-length substrate is referred to as the x-direction, the width direction as the y-direction, and the side of the excitation electrode parallel to the length direction of the fixed-length substrate is called the base side, with the side edge being the adjacent side of the base side. The width of the excitation electrode mentioned in the embodiments refers to the length of the base side of the parallelogram. The horizontal angle is the angle between the adjacent side and the length direction of the fixed-length substrate. The related terms and definitions of the induction electrode are the same as those of the excitation electrode.

[0062] During measurement, two rows of excitation electrodes on the ruler substrate are sequentially and periodically subjected to excitation signals of the same frequency and equal amplitude with a phase difference of φ. For example, the phase difference φ can be 90°, that is, the signals applied sequentially are Asin(ωt), Acos(ωt), -Asin(ωt), and -Acos(ωt), where A is the voltage amplitude, ω is the angular frequency, and t is the time. At this point, the excitation electrodes are arranged periodically in groups of four, with a total of 9 excitation electrode cycles, i.e., M1=M2=4, N1=N2=9, and φ=360° / 4=90°. The phase difference φ can also be 120°, i.e., the signals applied sequentially are Asin(ωt), Asin(ωt+120°), and Asin(ωt+240°). In this case, the excitation electrodes are arranged periodically in groups of three, with a total of 12 excitation electrode cycles, i.e., M1=M2=3, N1=N2=12, and φ=360° / 3=120°. The application methods for other excitation signals follow the same pattern (the above description of the phase difference φ is an example of the excitation signal application method and is not a limitation on actual parameters). At this point, the excitation electrodes on the fixed-scale base and the induction electrodes on the moving-scale base form a capacitor structure. When the moving scale base moves relative to the fixed scale base, the two rows of induction electrodes output traveling wave signals related to the displacement. After the output traveling wave signals are processed by signal processing circuits and the corresponding displacement calculations are performed, the displacement values ​​x corresponding to the two rows of induction electrodes are obtained respectively. 12 and x 21 The direction is perpendicular to the adjacent side of the bottom edge of the excitation electrode in that row.

[0063] like Figure 5 and Figure 6 As shown, the positive direction of x is defined as horizontal to the right, and the positive direction of y is vertically upward. The measurement value of the induction electrode is perpendicular to the adjacent side, and the positive direction of the measurement value is counterclockwise from the adjacent side. The angle between the adjacent side and the horizontal direction is positive counterclockwise and negative clockwise, that is, α is greater than or equal to 0 and β is less than or equal to 0. When the moving scale base moves relative to the fixed scale base in the two-dimensional plane, the displacement value x output by the two rows of induction electrodes can be obtained according to trigonometric function relationships. 12 x 21 The functional relationship between the actual displacement values ​​in the x and y directions is as follows:

[0064]

[0065] Written in matrix form:

[0066]

[0067] Solving the system of linear equations yields the actual displacement values ​​X and Y of the moving scale base relative to the fixed scale base:

[0068]

[0069] The above equation shows that the condition for A to be invertible holds true, and the condition for invertibility is:

[0070]

[0071] Right now k is a positive integer, and geometrically it means that the two rows of excitation electrodes must have a certain angle between them and cannot be collinear (parallel).

[0072] Example 2: This example describes a two-degree-of-freedom linear displacement sensor. Its measurement principle and most of its structure are the same as in Example 1, except that: Figure 7 As shown, the first row of sensing electrodes 2-1 on the moving ruler base 2 has a positive angle α between its side and the horizontal, with an absolute value greater than 90°, while the second row of sensing electrodes has a negative angle β between its side and the horizontal, with an absolute value greater than 90°. In Example 2, the sensing electrodes are arranged symmetrically vertically as in Method 1.

[0073] Example 3: This example describes a two-degree-of-freedom linear displacement sensor. Its measurement principle and most of its structure are the same as in Example 1, except that: Figure 8 As shown, the side of the first row of excitation electrodes 1-1 on the fixed-length substrate 1 forms a positive angle α with the horizontal, with an absolute value greater than 90°, while the side of the second row of excitation electrodes forms a negative angle β with the horizontal, with an absolute value less than 90°. In Example 3, the excitation electrodes are arranged in the manner of Method 2, i.e., they are shifted vertically.

[0074] Example 4: This example describes a two-degree-of-freedom linear displacement sensor. Its measurement principle and most of its structure are the same as in Example 1, except that: Figure 9 As shown, the first row of sensing electrodes 2-1 on the moving ruler base 2 has a positive angle α between its side and the horizontal, with an absolute value less than 90°, while the second row of sensing electrodes has a negative angle β between its side and the horizontal, with an absolute value greater than 90°. In Example 4, the sensing electrodes are arranged in the manner of Method 2, i.e., they are moved vertically.

[0075] Example 5: This example describes a two-degree-of-freedom linear displacement sensor. Its measurement principle and most of its structure are the same as in Example 1, except that: Figure 10 As shown, the excitation electrodes are all special parallelograms, i.e., rectangles. The long side of the first row of excitation electrodes 1-1 on the fixed-length base 1 has a positive angle α with the horizontal, and the absolute value is equal to 90°. The long side of the second row of excitation electrodes has a negative angle β with the horizontal, and the absolute value is equal to 180°.

[0076] Example 6: This example describes a two-degree-of-freedom linear displacement sensor. Its measurement principle and most of its structure are the same as in Example 1, except that: Figure 11As shown, the sensing electrodes are all special parallelograms, i.e., rectangles. The long side of the first row of sensing electrodes 2-1 on the moving ruler base 2 makes a positive angle α with the horizontal, with an absolute value of 90°. The long side of the second row of sensing electrodes makes a negative angle β with the horizontal, with an absolute value of 180°.

[0077] Example 7: This example describes a two-degree-of-freedom linear displacement sensor. Its measurement principle and most of its structure are the same as in Example 1, except that: Figure 12 As shown, the number of excitation electrodes in the first row n1 and the number of excitation electrodes in the second row n2 on the fixed-length substrate 1 are not equal, that is, n1≠n2≠0, and the number of cycles N1 of the first row of excitation electrodes differs from the number of cycles N2 of the second row of excitation electrodes by 1. In Example 7, n1 and n2 are n1=36 and n2=32 respectively (M1=M2=4, N1=9, N2=8).

[0078] Example 8: This example describes a two-degree-of-freedom linear displacement sensor. Its measurement principle and most of its structure are the same as in Example 1, except that: Figure 13 As shown, the number of excitation electrodes in the first row n1 and the number of excitation electrodes in the second row n2 on the fixed-length substrate 1 are not equal, i.e., n1≠n2≠0, and the number of cycles N1 of the first row of excitation electrodes and the number of cycles N2 of the second row of excitation electrodes are coprime numbers. In Example 8, n1 and n2 are n1=36 and n2=28 respectively (M1=M2=4, N1=9, N2=7).

[0079] Example 9: This example describes a two-degree-of-freedom linear displacement sensor. Its measurement principle and most of its structure are the same as in Example 1, except that: Figure 14 As shown, the number of excitation electrodes in the first row n1 and the number of excitation electrodes in the second row n2 on the fixed-length substrate 1 are not equal, i.e., n1≠n2≠0, and the number of cycles N1 of the first row of excitation electrodes is greater than or equal to 3, while the number of cycles N2 of the second row of excitation electrodes is equal to 1. In Example 9, n1 and n2 are n1=36 and n2=4 respectively (M1=M2=4, N1=9, N2=1).

[0080] Figure 12 The two rows of excitation electrodes 1-1 shown each consist of four electrodes forming one excitation cycle, with cycle numbers of 9 and 8 respectively, differing by one cycle. At any two positions along the length of the fixed-length base 1, the difference in displacement values ​​calculated by both methods is unique; that is, the difference in displacement values ​​uniquely corresponds to a single movement position of the moving scale base relative to the fixed-length base. Therefore, combining the two methods can achieve absolute displacement positioning. Similarly, Figure 13 The two rows of excitation electrodes 1-1 shown each consist of four electrodes forming one excitation cycle, with cycle numbers of 9 and 7 respectively. The cycle numbers of the two electrodes are coprime, and their combination can also achieve absolute displacement positioning. Figure 14The two rows of excitation electrodes 1-1 shown each have four electrodes forming one excitation cycle, with the number of cycles being 9 and 1 respectively. One row of both has only one cycle. The combination of the two can also achieve absolute displacement positioning.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the applicant has described the present invention in detail with reference to preferred embodiments, those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A two-degree-of-freedom linear displacement sensor, comprising a movable scale base and a fixed scale base arranged parallel to each other with a gap between them; a row of excitation electrodes is uniformly arranged along the length direction on the upper surface of the fixed scale base, all excitation electrodes in the row having the same shape and size; the row of excitation electrodes forms several phase excitation electrode groups; a row of sensing electrodes is uniformly arranged along the length direction on the lower surface of the movable scale base, all sensing electrodes in the row having the same shape and size; the row of sensing electrodes on the movable scale base is directly opposite the row of excitation electrodes on the fixed scale base; characterized in that: All excitation electrodes in this row are parallelograms, with their bases parallel to the length of the fixed-length substrate and a width of W1. The spacing between them is I1, and the angle between the adjacent sides of the excitation electrode's base and the length of the fixed-length substrate is α. Similarly, all induction electrodes in this row are parallelograms, with their bases parallel to the length of the fixed-length substrate and a width of W. T1 The row of sensing electrodes contains at least two sensing electrodes, and the bottom edge width W of a single sensing electrode is... T1 The sum of the gaps between two adjacent sensing electrodes is equal to 2(W1+I1), and the adjacent side of the bottom edge of the sensing electrode forms a certain angle with the length direction of the fixed-length substrate.

2. A two-degree-of-freedom linear displacement sensor according to claim 1, characterized in that: A second row of excitation electrodes is uniformly arranged along the length direction on the upper surface of the fixed-length substrate. All excitation electrodes in the second row have the same shape and size. This row of excitation electrodes forms several phase excitation electrode groups. A second row of induction electrodes is uniformly arranged along the length direction on the lower surface of the moving-length substrate. All induction electrodes in the second row have the same shape and size. The second row of induction electrodes on the moving-length substrate is directly opposite to the second row of excitation electrodes on the fixed-length substrate. All excitation electrodes in the second row are parallelograms. The base of the second row of excitation electrodes is parallel to the length direction of the fixed-length substrate and has a width of W2. The spacing between them is I2. The angle between the adjacent sides of the base of the second row of excitation electrodes and the length direction of the fixed-length substrate is β. All induction electrodes in the second row are parallelograms. The base of the second row of induction electrodes is parallel to the length direction of the fixed-length substrate and has a width of W2. T2 The second row of sensing electrodes contains at least two sensing electrodes, and the bottom edge width W of a single sensing electrode is... T1 The sum of the gaps between two adjacent sensing electrodes is equal to 2(W1+I1), and the adjacent side of the bottom edge of the sensing electrode forms a certain angle with the length direction of the fixed-length substrate.

3. A two-degree-of-freedom linear displacement sensor according to claim 2, characterized in that: The angles α and β are in the range of -180° to 180° and α-β≠kπ, where k is a positive integer.

4. A two-degree-of-freedom linear displacement sensor according to claim 2, characterized in that: The two rows of excitation electrodes are identical in shape and number, and are symmetrically arranged relative to the center line of the fixed-length substrate. Correspondingly, the two rows of induction electrodes are identical in shape and number, and are symmetrically arranged relative to the center line of the moving-length substrate.

5. A two-degree-of-freedom linear displacement sensor according to claim 2, characterized in that: The two rows of excitation electrodes are identical in shape and number, with the four sides of any row of excitation electrodes corresponding to and parallel to the four sides of the other row of excitation electrodes; the two rows of excitation electrodes are spaced apart by a set distance relative to the width of the fixed-length substrate and are symmetrically arranged relative to the geometric center of the fixed-length substrate; correspondingly, the two rows of sensing electrodes are identical in shape and number, with the four sides of any row of sensing electrodes corresponding to and parallel to the four sides of the other row of sensing electrodes; the two rows of sensing electrodes are spaced apart by a set distance relative to the width of the moving scale substrate and are symmetrically arranged relative to the geometric center of the moving scale substrate.

6. A two-degree-of-freedom linear displacement sensor according to claim 2, characterized in that: The two rows of excitation electrodes each have M1 and M2 excitation electrodes per cycle, with corresponding cycle numbers N1 and N2, respectively. The number of excitation electrodes in the two rows are n1 = M1 × N1 and n2 = M2 × N2, respectively. The number of excitation electrodes in one cycle corresponds to the number of excitation electrode groups formed by the excitation electrodes. The number of excitation electrode groups formed by the two rows of excitation electrodes may be the same or different. The phase difference of the same frequency and equal amplitude excitation signal periodically applied to each row of excitation electrodes is φ, where φ = 360° / M, and M is the number of excitation electrodes in one cycle.

7. A two-degree-of-freedom linear displacement sensor according to claim 2, characterized in that: The number of cycles of the two rows of excitation electrodes are coprime to achieve absolute positioning for displacement detection.

8. A method for measuring two-degree-of-freedom linear displacement, characterized in that: A two-degree-of-freedom linear displacement sensor as described in claim 1 is obtained in advance; During measurement, excitation signals of the same frequency and equal amplitude with a phase difference of φ are sequentially and periodically applied to the excitation electrodes on the fixed scale substrate. At this time, the excitation electrodes on the fixed scale substrate and the induction electrodes on the moving scale substrate form a capacitor structure. When the moving scale substrate moves relative to the fixed scale substrate, the induction electrodes output a traveling wave signal related to the displacement. The output traveling wave signal is then processed by a signal processing circuit, and after corresponding displacement calculations, the displacement value x output by the induction electrodes is obtained. 12 The direction is perpendicular to the adjacent side of the bottom edge of the excitation electrode in that row; When the moving scale base moves relative to the fixed scale base along the x-direction, the displacement value X in the x-direction is obtained according to trigonometric relationships: When the moving scale base moves relative to the fixed scale base along the y-direction, the displacement value Y in the y-direction is obtained according to trigonometric relationships:

9. A method for measuring two-degree-of-freedom linear displacement, characterized in that: A two-degree-of-freedom linear displacement sensor as described in claim 2 is obtained in advance; During measurement, excitation signals are applied to the two rows of excitation electrodes on the fixed scale base. At this time, the excitation electrodes on the fixed scale base and the corresponding induction electrodes on the moving scale base form a capacitor structure. When the moving scale base moves relative to the fixed scale base, the two rows of induction electrodes output traveling wave signals related to displacement. These two traveling wave signals are then processed by signal processing circuits, and after corresponding displacement calculations, the displacement value x output by the first row of induction electrodes is obtained. 12 The displacement value x output by the second row of sensing electrodes 21 The directions are all perpendicular to the adjacent side of the bottom edge of the corresponding row excitation electrode; Let the actual planar displacement d of the moving scale base relative to the fixed scale base be: X and Y are the displacement values ​​of the moving scale base relative to the fixed scale base along the x-direction and along the y-direction, respectively; The displacement value x output by the first row of induction electrodes is obtained using trigonometric relationships. 12 The displacement value x output by the second row of sensing electrodes 21 for: Written in matrix form: Solving the system of linear equations yields the displacement X along the x-direction and the displacement Y along the y-direction of the moving scale base relative to the fixed scale base:

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