An absolute linear displacement sensor implementation method, structure and working method

Abstract

This invention discloses a method, structure, and operating method for implementing an absolute linear displacement sensor. The method combines two incremental linear displacement sensors with mutually prime periods. Absolute displacement measurement is achieved by utilizing the unique correspondence between the traveling wave phase relationship and spatial displacement output by the two incremental linear displacement sensors. The two incremental linear displacement sensors share a single sensing signal interface. By controlling the operating state of the two sensors as needed, power consumption is reduced and the hardware system is simplified while meeting functional requirements. This design not only has a simple structure and low manufacturing requirements and costs, but also achieves absolute displacement measurement without cumulative measurement errors. It also allows for compact / miniaturized products, adapting to installations in more confined spaces and reducing power consumption.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, specifically to a method for implementing an absolute linear displacement sensor, its structure, and its working method. Background Technology

[0002] A displacement sensor, also known as a linear sensor, is a sensing device that converts a measured physical quantity into an electrical signal. Displacement sensors can be categorized into linear displacement sensors and angular displacement sensors based on the mode of motion, converting linear displacement (distance) and angular displacement (angle) into electrical signals, respectively. Currently, displacement sensors on the market are mainly divided into absolute displacement sensors and incremental displacement sensors according to their measurement methods. Incremental displacement sensors are simpler in principle and have lower manufacturing requirements and costs compared to absolute displacement sensors. Absolute displacement sensors, compared to incremental displacement sensors, have advantages such as the ability to achieve absolute displacement measurement and the absence of cumulative measurement errors, thus gaining wider application. Currently, there are various types of sensors capable of absolute displacement measurement, with capacitive absolute displacement sensors and optical encoder absolute displacement sensors being among the most widely used.

[0003] Capacitive absolute displacement sensors typically possess advantages such as strong anti-interference capability, simple structure, and low manufacturing cost. However, because they use an electric field as the sensing medium, they are susceptible to edge effects and parasitic capacitance, thus limiting further improvements in measurement accuracy. Grating ruler absolute displacement sensors, on the other hand, offer advantages such as long lifespan, strong anti-interference capability, and high resolution, and are widely used as positioning sensors in high-precision measurement fields such as high-performance CNC machine tools. However, the measurement accuracy of the grating depends on the grating spacing, and the measurement range depends on the manufacturing dimensions of the grating ruler. Higher grating ruler precision requires more precise grating lines. As the size increases, the manufacturing difficulty also increases. Furthermore, absolute grating rulers require complex encoding and image processing techniques for decoding to achieve absolute positioning. Therefore, there is an urgent need to propose a method for developing an absolute linear displacement sensor that is low in manufacturing difficulty and cost, while possessing high measurement accuracy and capable of absolute displacement measurement. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the existing technology, the technical problem to be solved by the present invention is: how to provide an absolute linear displacement sensor with simple structure, low manufacturing requirements and manufacturing cost, low power consumption, and the ability to achieve absolute displacement measurement without cumulative measurement error.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] An absolute linear displacement sensor implementation method is proposed, which combines two incremental linear displacement sensors, wherein the period numbers of the two incremental linear displacement sensors are coprime numbers, so as to realize absolute displacement measurement by utilizing the traveling wave phase relationship and the unique correspondence between the spatial displacement output by the two incremental linear displacement sensors respectively.

[0007] The working principle of this invention is as follows: This scheme utilizes two incremental linear displacement sensors with coprime period numbers to output traveling wave signals U respectively. O1 and U O2 Then, through phase processing, the corresponding phase values ​​are obtained respectively. and The absolute number of cycles is determined by the phase relationship between two incremental linear displacement sensors, where the absolute number of cycles refers to the number of cycles based on a set zero point. Then, the displacement within the absolute number of cycles is determined based on a single incremental linear displacement sensor. Finally, the absolute displacement measurement of the absolute linear displacement sensor is achieved by combining the absolute number of cycles and the displacement within the absolute number of cycles.

[0008] In summary, this scheme employs two incremental linear displacement sensors to achieve absolute displacement measurement, offering advantages such as simple structure, low manufacturing requirements, and low manufacturing cost. Secondly, by using two incremental linear displacement sensors with mutually prime measurement cycle numbers as components of the absolute linear displacement sensor, the absolute displacement value is calculated using an absolute positioning method based on the phase relationship of the traveling wave signals output by the two incremental linear displacement sensors. This positioning method features simple encoding and decoding, a large positioning error limit, easier achievement of absolute positioning, and high measurement accuracy. Furthermore, the two incremental linear displacement sensors operate in a time-sharing manner, ensuring high-precision displacement measurement while effectively reducing the power consumption of the entire sensor circuit. In addition, combining the two incremental linear displacement sensors and sharing a single induction signal processing interface reduces the need for a separate induction signal processing device, thus reducing cost and circuit space.

[0009] An absolute linear displacement sensor structure includes an excitation module, a first incremental linear displacement sensor, a second incremental linear displacement sensor, a switching circuit, and a sensing signal processing module. The first incremental linear displacement sensor includes a first movable scale and a first fixed scale arranged parallel to each other, with a gap between them. The first movable scale includes a first movable scale base and a first sensing electrode assembly disposed on the first movable scale base. The first fixed scale includes a first fixed scale base and a first excitation electrode assembly disposed on the first fixed scale base for N measurement cycles. The first excitation electrode assembly and the first sensing electrode assembly are signal coupled. The second incremental linear displacement sensor includes a second movable scale and a second fixed scale arranged parallel to each other. There is a gap between the ruler and the second fixed ruler. The second movable ruler includes a second movable ruler base and a second sensing electrode assembly disposed on the second movable ruler base. The second fixed ruler includes a second fixed ruler base and a second excitation electrode assembly disposed on the second fixed ruler base for M measurement cycles. The second excitation electrode assembly and the second sensing electrode assembly are signal coupled, and N and M are coprime numbers. The excitation module inputs excitation signals to the first excitation electrode assembly and the second excitation electrode assembly respectively through the switching circuit. The first sensing electrode assembly and the second sensing electrode assembly share a set of sensing signal processing interfaces connected to the sensing signal processing module. The sensing signal processing module obtains absolute displacement data based on the received sensing signals to realize absolute displacement measurement.

[0010] Thus, in operation, the absolute linear displacement sensor structure of this invention first inputs a sinusoidal excitation signal to the second excitation electrode assembly (or the first excitation electrode assembly) of the second incremental linear displacement sensor (or the first incremental linear displacement sensor). Direct signal coupling occurs between the second sensing electrode assembly (or the first sensing electrode assembly) and the second excitation electrode assembly (or the first excitation electrode assembly), causing the second sensing electrode assembly (or the first sensing electrode assembly) to generate a second sensing signal (or a first sensing signal), which is then input to the sensing signal processing module. Next, the excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly (or the second excitation electrode assembly) of the first incremental linear displacement sensor (or the second incremental linear displacement sensor). Due to electric field coupling, the first sensing electrode assembly (or the second sensing electrode assembly) generates a first sensing signal (or a second sensing signal), which is then input to the sensing signal processing module. The sensing signal processing module processes the first and second sensing signals to obtain absolute displacement data, thereby achieving the purpose of absolute displacement measurement. The sensing electrode assemblies of the two incremental linear displacement sensors share a set of sensing signal processing interfaces, reducing the number of sensing signal processing devices and decreasing cost and circuit space.

[0011] Preferably, the first excitation electrode assembly includes a plurality of first excitation electrodes, the width of the first excitation electrode is W1, the spacing between two adjacent first excitation electrodes is I1, and four adjacent first excitation electrodes sequentially constitute a first measurement cycle, then the length of the first measurement cycle is W. T1 The calculation formula is: W T1 = 4*W1+4*I1, the total length of the first excitation electrode assembly of the first incremental linear displacement sensor is L1, and L1=W T1 *N=(4*W1+4*I1)*N;

[0012] The second excitation electrode assembly includes multiple second excitation electrodes. The width of each second excitation electrode is W2, the spacing between two adjacent second excitation electrodes is I2, and four adjacent second excitation electrodes sequentially form a second measurement cycle. The length W of the second measurement cycle is... T2 The calculation formula is: W T2 = 4*W2 + 4*I2, the total length of the second excitation electrode assembly of the second incremental linear displacement sensor is L2, and L2 = W T2 *M = (4*W² + 4*I²)*M;

[0013] And L1 = L2;

[0014] The first sensing electrode assembly includes two double sinusoidal first sensing electrodes, both of which have a width of W. T1 / 2, both with a height of H1, and the distance between the center lines of the two double sinusoidal first sensing electrodes is W. T1 / 2;

[0015] The second sensing electrode assembly includes two double sinusoidal second sensing electrodes, both of which have a width of W. T2 / 2, both with a height of H2, and the distance between the center lines of the two said double sinusoidal second sensing electrodes is W. T2 / 2.

[0016] Preferably, the two dual sinusoidal first sensing electrodes form a differential structure, and the phase difference between the induced signals output by the two dual sinusoidal first sensing electrodes is π. The output signal U is obtained by calculating the difference between the induced signals output by the two dual sinusoidal first sensing electrodes. O1 , and U O1 The calculation formula is:

[0017]

[0018] In the formula: M1 is the amplitude of the traveling wave signal of the first incremental linear displacement sensor;

[0019] x1 is the relative displacement value between the first moving scale and the first fixed scale of the first incremental linear displacement sensor in a single measurement cycle;

[0020] W T1 The length of the first measurement cycle of the first incremental linear displacement sensor;

[0021] ω is the angular frequency of the excitation signal emitted by the excitation module;

[0022] t represents time.

[0023] In this way, the differential structure can eliminate common-mode interference while doubling the strength of the sensing signal, thereby improving the signal-to-noise ratio.

[0024] Preferably, the two dual sinusoidal second sensing electrodes form a differential structure, and the phase difference between the induced signals output by the two dual sinusoidal second sensing electrodes is π. The output signal U is obtained by calculating the difference between the induced signals output by the two dual sinusoidal second sensing electrodes. O2 , and U O2 The calculation formula is:

[0025]

[0026] In the formula: M2 is the amplitude of the traveling wave signal of the second incremental linear displacement sensor;

[0027] x2 represents the relative displacement value between the second moving scale and the second fixed scale of the second incremental linear displacement sensor within a single measurement cycle;

[0028] W T2 The length of the second measurement cycle of the second incremental linear displacement sensor;

[0029] ω is the angular frequency of the excitation signal emitted by the excitation module;

[0030] t represents time.

[0031] A method for operating an absolute linear displacement sensor, employing the aforementioned absolute linear displacement sensor structure, includes the following steps:

[0032] Step 1) The excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor. The second sensing electrode assembly and the second excitation electrode assembly are directly coupled. The second sensing electrode assembly generates a second sensing signal and inputs it to the sensing signal processing module.

[0033] Step 2) The excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through the switching circuit. The first sensing electrode assembly and the first excitation electrode assembly are directly coupled. The first sensing electrode assembly generates a first sensing signal and inputs it to the sensing signal processing module.

[0034] Step 3) The induction signal processing module processes the first induction signal and the second induction signal to obtain absolute displacement data.

[0035] Preferably, the excitation module applies excitation in a time-segmented manner, inputting sinusoidal excitation signals to the first incremental linear displacement sensor and the second incremental linear displacement sensor.

[0036] In step 1), when the excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor, the first incremental linear displacement sensor does not work.

[0037] In step 2), when the excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through the switching circuit, the second incremental linear displacement sensor does not work.

[0038] Preferably, the first excitation electrode assembly includes a plurality of first excitation electrodes, and four adjacent first excitation electrodes sequentially constitute a first measurement cycle. The 4n1+1th first excitation electrode is connected to a group through the A1 phase excitation signal line to form an A1 excitation phase, the 4n1+2th first excitation electrode is connected to a group through the B1 phase excitation signal line to form a B1 excitation phase, the 4n1+3th first excitation electrode is connected to a group through the C1 phase excitation signal line to form a C1 excitation phase, and the 4n1+4th first excitation electrode is connected to a group through the D1 phase excitation signal line to form a D1 excitation phase, wherein n1 takes all integers from 0 to N in sequence.

[0039] The second excitation electrode assembly includes multiple second excitation electrodes, with four adjacent second excitation electrodes sequentially forming a second measurement cycle; and the 4n2+1th second excitation electrode is connected to a group through the A2 phase excitation signal line to form the A2 excitation phase, the 4n2+2nd second excitation electrode is connected to a group through the B2 phase excitation signal line to form the B2 excitation phase, the 4n2+3rd second excitation electrode is connected to a group through the C2 phase excitation signal line to form the C2 excitation phase, and the 4n2+4th second excitation electrode is connected to a group through the D2 phase excitation signal line to form the D2 excitation phase, wherein n2 sequentially takes all integers from 0 to M;

[0040] In step 1), the excitation module inputs four sinusoidal excitation signals with phases successively differing by π / 2 to the second excitation electrode assembly of the second incremental linear displacement sensor, and the A1 excitation phase input sinusoidal excitation signal U S+ B1 excitation phase input sinusoidal excitation signal U C+ C1 is the input sinusoidal excitation signal U S- D1 excitation phase input sinusoidal excitation signal U C- , and U S+ =Esinωt,U C+ =Ecosωt,U S- =-Esinωt,U C- = -Ecosωt;

[0041] In step 2), the excitation module inputs four sinusoidal excitation signals with phases successively differing by π / 2 to the first excitation electrode assembly of the first incremental linear displacement sensor, and the A2 excitation phase inputs the sinusoidal excitation signal U. S+ B2 excitation phase input sinusoidal excitation signal U C+ C2 excitation phase input sinusoidal excitation signal U S- D2 excitation phase input sinusoidal excitation signal U C- .

[0042] Preferably, in step 3), when the excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor and the first incremental linear displacement sensor is not working, the sensing signal processing module processes the sensing signal of the second incremental linear displacement sensor to obtain and store the second phase value. When the excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through the switching circuit and the second incremental linear displacement sensor is not working, the sensing signal processing module processes the sensing signal of the first incremental linear displacement sensor to obtain and store the first phase value. The sensing signal processing module is based on the second phase value. and the first phase value The absolute displacement value is calculated.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. This invention combines two incremental linear displacement sensors, employing a method where the number of periods are coprime. The absolute number of periods is obtained through the phase relationship between the two incremental linear displacement sensors. Then, the displacement within the absolute number of periods is obtained using a single incremental linear displacement sensor. Thus, absolute displacement measurement is achieved by utilizing the unique correspondence between the traveling wave phase relationship output by the two incremental linear displacement sensors and the spatial displacement. Therefore, this solution reduces manufacturing requirements and costs while achieving absolute positioning, and also offers advantages such as absolute displacement measurement and no cumulative measurement error. This makes the linear displacement sensor applicable to more situations, greatly improving its versatility.

[0045] 2. In this invention, the first sensing electrode assembly of the first incremental linear displacement sensor and the second sensing electrode assembly of the second incremental linear displacement sensor share a common sensing signal processing interface and are connected to the same sensing signal processing module. This reduces the number of sensing signal processing modules, thereby reducing circuit space and making it suitable for installation in more confined spaces. Simultaneously, the first and second incremental linear displacement sensors operate in time-sharing phases, avoiding the need for the second incremental linear displacement sensor to apply excitation in real time, thus reducing power consumption.

[0046] 3. In this invention, the first incremental linear displacement sensor adopts a through-beam signal transmission method, that is, the first excitation electrode assembly and the first sensing electrode assembly directly couple the signals. The second incremental linear displacement sensor also adopts a through-beam signal transmission method, that is, the second excitation electrode assembly and the second sensing electrode assembly directly couple the signals. This allows the signal to be reflected without passing through an additional sensing structure, which can effectively improve the coupling signal strength, improve the signal-to-noise ratio, and enhance the anti-interference capability.

[0047] 4. In this invention, the two double sinusoidal first sensing electrodes of the first incremental linear displacement sensor form a differential structure, and the two double sinusoidal second sensing electrodes of the second incremental linear displacement sensor also form a differential structure. The differential structure can eliminate common-mode interference and double the sensing signal strength, thereby improving the signal-to-noise ratio.

[0048] 5. In this invention, the first incremental linear displacement sensor and the second incremental linear displacement sensor adopt a positioning method with coprime cycle numbers. This means that if the cycle number N of the first incremental linear displacement sensor remains unchanged, and the cycle number N of the first incremental linear displacement sensor and the cycle number M of the second incremental linear displacement sensor are coprime, the cycle number M of the second incremental linear displacement sensor can be appropriately reduced to increase the positioning error limit. This allows the sensor of this invention to achieve absolute positioning more easily while maintaining high precision. Attached Figure Description

[0049] Figure 1This is a connection diagram of the absolute linear displacement sensor structure of the present invention;

[0050] Figure 2 This is a schematic diagram of the structure of the first incremental linear displacement sensor in the absolute linear displacement sensor structure of the present invention;

[0051] Figure 3 This is a schematic diagram of the structure of the second incremental linear displacement sensor in the absolute linear displacement sensor structure of the present invention;

[0052] Figure 4 This is a schematic diagram illustrating the principle of the absolute linear displacement sensor structure of the present invention.

[0053] Explanation of reference numerals in the attached figures: First excitation electrode 1, First sensing electrode 2, Second excitation electrode 3, Second sensing electrode 4. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0055] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" mean that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0056] Firstly, this specific embodiment provides a method for implementing an absolute linear displacement sensor, which combines two incremental linear displacement sensors, wherein the number of periods of the two incremental linear displacement sensors are mutually prime numbers (two non-zero natural numbers with only 1 as their common factor are mutually prime numbers), so as to realize absolute displacement measurement by utilizing the traveling wave phase relationship and the unique correspondence between the spatial displacement output by the two incremental linear displacement sensors respectively.

[0057] The working principle of this invention is as follows: This scheme utilizes two incremental linear displacement sensors with coprime period numbers to output traveling wave signals U respectively. O1 and U O2 Then, through phase processing, the corresponding phase values ​​are obtained respectively. and The absolute number of cycles is determined by the phase relationship between two incremental linear displacement sensors, where the absolute number of cycles refers to the number of cycles based on a set zero point. Then, the displacement within the absolute number of cycles is determined based on a single incremental linear displacement sensor. Finally, the absolute displacement measurement of the absolute linear displacement sensor is achieved by combining the absolute number of cycles and the displacement within the absolute number of cycles.

[0058] In summary, this scheme employs two incremental linear displacement sensors to achieve absolute displacement measurement, offering advantages such as simple structure, low manufacturing requirements, and low manufacturing cost. Secondly, by using two incremental linear displacement sensors with mutually prime measurement cycle numbers as components of the absolute linear displacement sensor, the absolute displacement value is calculated using an absolute positioning method based on the phase relationship of the traveling wave signals output by the two incremental linear displacement sensors. This positioning method features simple encoding and decoding, a large positioning error limit, easier achievement of absolute positioning, and high measurement accuracy. Furthermore, the two incremental linear displacement sensors operate in a time-sharing manner, ensuring high-precision displacement measurement while effectively reducing the power consumption of the entire sensor circuit. In addition, combining the two incremental linear displacement sensors and sharing a single induction signal processing interface reduces the need for a separate induction signal processing device, thus reducing cost and circuit space.

[0059] Secondly, this specific embodiment also provides an absolute linear displacement sensor structure, as shown in the attached figure. Figure 1 As shown, it includes an excitation module, a first incremental linear displacement sensor, a second incremental linear displacement sensor, a switching circuit, and a sensing signal processing module, as attached. Figure 2As shown, the first incremental linear displacement sensor includes a first movable scale and a first fixed scale arranged in parallel and facing each other, with a gap d between them. The first movable scale includes a first movable scale base and a first sensing electrode assembly disposed on the first movable scale base. The first fixed scale includes a first fixed scale base and a first excitation electrode assembly disposed on the first fixed scale base for N measurement cycles. The first excitation electrode assembly and the first sensing electrode assembly are coupled together, as shown in the attached figure. Figure 3 As shown, the second incremental linear displacement sensor includes a second moving scale and a second fixed scale arranged in parallel and facing each other, with a gap between them. The second moving scale includes a second moving scale base and a second sensing electrode assembly disposed on the second moving scale base. The second fixed scale includes a second fixed scale base and a second excitation electrode assembly disposed on the second fixed scale base for M measurement cycles. The second excitation electrode assembly and the second sensing electrode assembly are signal coupled, and N and M are coprime numbers. In specific implementation, the first fixed scale and the second fixed scale can be located on the same base or on different bases, and the first moving scale and the second moving scale can be located on the same base or on different bases. The excitation module inputs excitation signals to the first excitation electrode assembly and the second excitation electrode assembly respectively through a switching circuit. The first sensing electrode assembly and the second sensing electrode assembly share a set of sensing signal processing interfaces connected to the sensing signal processing module. The sensing signal processing module is used to receive the sensing signals from the first sensing electrode assembly and the second sensing electrode assembly to obtain absolute displacement data based on the received sensing signals, thereby realizing absolute displacement measurement.

[0060] Thus, in operation, the absolute linear displacement sensor structure of the present invention first inputs a sinusoidal excitation signal to the second excitation electrode assembly (first excitation electrode assembly) of the second incremental linear displacement sensor (first incremental linear displacement sensor). Direct signal coupling occurs between the second sensing electrode assembly (first sensing electrode assembly) and the second excitation electrode assembly (first excitation electrode assembly), causing the second sensing electrode assembly (first sensing electrode assembly) to generate a second sensing signal (first sensing signal) which is then input to the sensing signal processing module. Next, the excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly (second excitation electrode assembly) of the first incremental linear displacement sensor (second incremental linear displacement sensor). Due to electric field coupling, the first sensing electrode assembly (second sensing electrode assembly) generates a first sensing signal (second sensing signal) which is then input to the sensing signal processing module. The sensing signal processing module processes the first and second sensing signals to obtain absolute displacement data, thereby achieving the purpose of absolute displacement measurement.

[0061] For example, see appendix. Figure 2As shown, in this embodiment, the first excitation electrode assembly includes a plurality of first excitation electrodes 1. The width of the first excitation electrode 1 is W1, the spacing between two adjacent first excitation electrodes 1 is I1, and four adjacent first excitation electrodes 1 sequentially constitute a first measurement cycle. The length W of the first measurement cycle is... T1 The calculation formula is: W T1 = 4*W1+4*I1; The total length of the first excitation electrode assembly of the first incremental linear displacement sensor is L1, and L1 = W T1 *N=(4*W1+4*I1)*N;

[0062] The first sensing electrode assembly includes two double sinusoidal first sensing electrodes 2, each with a width of W. T1 / 2, both with a height of H1, and the centerline spacing of the two double sinusoidal first sensing electrodes 2 is W. T1 / 2;

[0063] For example, see appendix. Figure 3 As shown, the second excitation electrode assembly includes multiple second excitation electrodes 3. The width of each second excitation electrode 3 is W2, the spacing between two adjacent second excitation electrodes 3 is I2, and four adjacent second excitation electrodes 3 sequentially form a second measurement cycle. The length W of the second measurement cycle is... T2 The calculation formula is: W T2 = 4*W2 + 4*I2; The total length of the second excitation electrode assembly of the second incremental linear displacement sensor is L2, and L2 = W T2 *M = (4*W² + 4*I²)*M; and L1 = L2;

[0064] The second sensing electrode assembly includes two double sinusoidal second sensing electrodes 4, each with a width of W. T2 / 2, both with a height of H2, and the centerline spacing of the two double sinusoidal second sensing electrodes 4 is W. T2 / 2.

[0065] In this embodiment, the two double sinusoidal first sensing electrodes 2 form a differential structure, and the phase difference of the sensing signals output by the two double sinusoidal first sensing electrodes 2 is π. Considering the interference E caused by external factors and the interference E caused by the inconsistent potential intensity generated by the first excitation electrodes 1 at different positions... S (x1)sinωt and E C (x1)cosωt, and the output signals of the two first sensing electrodes 2 are U 01+ and U O1- ,but:

[0066]

[0067]

[0068] Introducing the aforementioned interference will cause the phase of the sensor output signal to lag or lead, resulting in a large intra-period error. To solve this problem, a differential sensing electrode structure is proposed, which adds a first sensing electrode 2 to the original structure. The spatial positions of the two first sensing electrodes 2 differ by W. T1 / 2, the phase difference of the output induced signal is π, then the induced signal U output by the two double sinusoidal first induction electrodes 2 01+ and U O1- The difference is used to obtain the output signal U. O1 , and U O1 The calculation formula is:

[0069]

[0070] In the formula: M1 is the amplitude of the traveling wave signal of the first incremental linear displacement sensor;

[0071] x1 is the relative displacement value between the first moving scale and the first fixed scale of the first incremental linear displacement sensor in a single measurement cycle;

[0072] W T1 The length of the first measurement cycle of the first incremental linear displacement sensor;

[0073] ω is the angular frequency of the excitation signal emitted by the excitation module;

[0074] t represents time.

[0075] As can be seen from the above formula, the differential structure formed by the two double sinusoidal first sensing electrodes 2 can eliminate common-mode interference while doubling the sensing signal strength and improving the signal-to-noise ratio.

[0076] In this embodiment, the two double sinusoidal second sensing electrodes 4 form a differential structure, and the phase difference of the sensing signals output by the two double sinusoidal second sensing electrodes 4 is π. Considering the interference E caused by external factors and the interference E caused by the inconsistent potential intensity generated by the second excitation electrodes 3 at different positions... S (x2)sinωt and E C (x2)cosωt, and the output signals of the two second sensing electrodes 4 are respectively U 02+ and U O2- ,but:

[0077]

[0078]

[0079] Introducing the aforementioned interference will cause the phase of the sensor output signal to lag or lead, resulting in a large intra-period error. To solve this problem, a differential sensing electrode structure is proposed, which adds a second sensing electrode 4 to the original structure. The spatial positions of the two second sensing electrodes 4 differ by W. T2 / 2, the phase difference of its output induced signal is π, then the induced signal U output by the two double sinusoidal second induction electrodes 4 02+ and U O2- The difference is used to obtain the output signal U. O2 , and U O2 The calculation formula is:

[0080]

[0081] In the formula: M2 is the amplitude of the traveling wave signal of the second incremental linear displacement sensor;

[0082] x2 represents the relative displacement value between the second moving scale and the second fixed scale of the second incremental linear displacement sensor within a single measurement cycle;

[0083] W T2 The length of the second measurement cycle of the second incremental linear displacement sensor;

[0084] ω is the angular frequency of the excitation signal emitted by the excitation module;

[0085] t represents time.

[0086] In this way, the differential structure can eliminate common-mode interference while doubling the strength of the sensing signal, thereby improving the signal-to-noise ratio.

[0087] Finally, this specific embodiment also provides a method for operating an absolute linear displacement sensor, which employs the above-described absolute linear displacement sensor structure and includes the following steps:

[0088] Step 1) The excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor. The second sensing electrode assembly and the second excitation electrode assembly are directly coupled. The second sensing electrode assembly generates a second sensing signal and inputs it to the sensing signal processing module.

[0089] Step 2) The excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through the switching circuit. The first sensing electrode assembly and the first excitation electrode assembly are directly coupled. The first sensing electrode assembly generates a first sensing signal and inputs it to the sensing signal processing module.

[0090] Step 3) The sensing signal processing module processes the first and second sensing signals to obtain absolute displacement data. Specifically, in step 1), a sinusoidal excitation signal can be first input to the first excitation electrode assembly of the first incremental linear displacement sensor, and in step 2), a sinusoidal excitation signal can be input to the second excitation electrode assembly of the second incremental linear displacement sensor. In this scheme, "first" and "second" are merely used to distinguish between the two incremental linear displacement sensors and do not specifically refer to any particular incremental linear displacement sensor.

[0091] In this embodiment, the excitation module applies excitation in time intervals to input sinusoidal excitation signals to the first incremental linear displacement sensor and the second incremental linear displacement sensor;

[0092] In step 1), when the excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor, the first incremental linear displacement sensor does not work.

[0093] In step 2), when the excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through the switching circuit, the second incremental linear displacement sensor does not work.

[0094] In this embodiment, the first excitation electrode assembly includes a plurality of first excitation electrodes 1. Four adjacent first excitation electrodes 1 sequentially constitute a first measurement cycle. The 4n1+1th first excitation electrode 1 is connected to form a group through the A1 phase excitation signal line to form the A1 excitation phase. The 4n1+2th first excitation electrode 1 is connected to form a group through the B1 phase excitation signal line to form the B1 excitation phase. The 4n1+3th first excitation electrode 1 is connected to form a group through the C1 phase excitation signal line to form the C1 excitation phase. The 4n1+4th first excitation electrode 1 is connected to form a group through the D1 phase excitation signal line to form the D1 excitation phase. Here, n1 takes all integers from 0 to N in sequence.

[0095] The second excitation electrode assembly includes multiple second excitation electrodes 3, with four adjacent second excitation electrodes 3 sequentially forming a second measurement cycle; and the 4n2+1th second excitation electrode 3 is connected to form a group through the A2 phase excitation signal line to form the A2 excitation phase, the 4n2+2nd second excitation electrode 3 is connected to form a group through the B2 phase excitation signal line to form the B2 excitation phase, the 4n2+3rd second excitation electrode 3 is connected to form a group through the C2 phase excitation signal line to form the C2 excitation phase, and the 4n2+4th second excitation electrode 3 is connected to form a group through the D2 phase excitation signal line to form the D2 excitation phase, wherein n2 sequentially takes all integers from 0 to M;

[0096] In step 1), the excitation module inputs four sinusoidal excitation signals with phases successively differing by π / 2 to the second excitation electrode assembly of the second incremental linear displacement sensor, and the A1 excitation phase input sinusoidal excitation signal U S+ B1 excitation phase input sinusoidal excitation signal U C+ C1 is the input sinusoidal excitation signal U S- D1 excitation phase input sinusoidal excitation signal U C- , and U S+ =Esinωt,U C+ =Ecosωt,U S- =-Esinωt,U C- = -Ecosωt;

[0097] In step 2), the excitation module inputs four sinusoidal excitation signals with phases successively differing by π / 2 to the first excitation electrode assembly of the first incremental linear displacement sensor, and the A2 excitation phase inputs the sinusoidal excitation signal U. S+ B2 excitation phase input sinusoidal excitation signal U C+ C2 excitation phase input sinusoidal excitation signal U S- D2 excitation phase input sinusoidal excitation signal U C- .

[0098] In this embodiment, in step 3), when the excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor and the first incremental linear displacement sensor is not working, the sensing signal processing module processes the sensing signal of the second incremental linear displacement sensor to obtain and store the second phase value. When the excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through the switching circuit and the second incremental linear displacement sensor is not working, the sensing signal processing module processes the sensing signal of the first incremental linear displacement sensor to obtain and store the first phase value. The sensing signal processing module based on the second phase value and the first phase value The absolute displacement value is calculated.

[0099] The specific working principle of this solution is as follows, as shown in the attached document. Figure 4 As shown, the first incremental linear displacement sensor and the second incremental linear displacement sensor (attached) Figure 4 The output signals of the sensors are all input to the sensing signal processing module for processing. The sensing signal processing module includes a subtraction circuit, a filtering and shaping circuit, and an FPGA signal processing system. The sensing signals of the first and second sensing electrode components are transmitted to the Q1 and Q2 interfaces through leads, and then input to the subtraction circuit of the sensing signal processing module. The subtraction circuit obtains the output signal U of the first sensing electrode component.O1 The output signal U of the second sensing electrode assembly O2 and U O1 and U O2 The output is fed to a filtering and shaping circuit, which uses a zero-crossing comparator to convert the sinusoidal signal into a square wave signal and outputs it to the FPGA signal processing system. The FPGA signal processing system includes a phase measurement function, which is used to obtain the first phase value from the square wave signal. Second phase value Then, the time difference of each square wave signal is measured using a high-frequency clock pulse interpolation method. Finally, the absolute displacement value is accurately obtained through unit conversion and output to realize the measurement of the absolute displacement value.

[0100] This invention combines two incremental linear displacement sensors, employing a method where the number of periods are coprime. The absolute number of periods is obtained through the phase relationship between the two sensors. Then, the displacement within that absolute number of periods is obtained using a single incremental linear displacement sensor. Thus, absolute displacement measurement is achieved by utilizing the unique correspondence between the traveling wave phase relationship output by the two sensors and the spatial displacement. Therefore, this solution reduces manufacturing requirements and costs while achieving absolute positioning, and offers advantages such as absolute displacement measurement and no cumulative measurement error. This makes the linear displacement sensor applicable to more situations, greatly improving its versatility. In this invention, the first sensing electrode assembly of the first incremental linear displacement sensor and the second sensing electrode assembly of the second incremental linear displacement sensor share a common sensing signal processing interface and are connected to the same sensing signal processing module, thereby reducing one set of sensing signal processing modules and thus reducing circuit space. Simultaneously, the first and second incremental linear displacement sensors operate in time-sharing phases, avoiding real-time excitation of the second sensor and reducing power consumption. In this invention, the first incremental linear displacement sensor employs a through-beam signal transmission method, meaning the first excitation electrode assembly and the first sensing electrode assembly directly couple their signals. The second incremental linear displacement sensor also employs a through-beam signal transmission method, meaning the second excitation electrode assembly and the second sensing electrode assembly directly couple their signals. This eliminates the need for signal reflection through additional sensing structures, effectively improving the coupled signal strength, increasing the signal-to-noise ratio, and enhancing anti-interference capabilities. In this invention, the two double-sinusoidal first sensing electrodes 2 of the first incremental linear displacement sensor form a differential structure, and the two double-sinusoidal second sensing electrodes 4 of the second incremental linear displacement sensor also form a differential structure. This differential structure eliminates common-mode interference while doubling the sensing signal strength, thereby improving the signal-to-noise ratio. In this invention, the first incremental linear displacement sensor and the second incremental linear displacement sensor adopt a positioning method with coprime cycle numbers. This means that if the cycle number N of the first incremental linear displacement sensor remains unchanged, and the cycle number N of the first incremental linear displacement sensor and the cycle number M of the second incremental linear displacement sensor are coprime, the cycle number M of the second incremental linear displacement sensor can be appropriately reduced to increase the positioning error limit. This allows the sensor of this invention to achieve absolute positioning more easily while maintaining high precision.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. 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 method for implementing an absolute linear displacement sensor, characterized in that, Two incremental linear displacement sensors are combined, and the number of cycles of the two incremental linear displacement sensors are coprime numbers, so as to realize absolute displacement measurement by utilizing the traveling wave phase relationship and the unique correspondence between the spatial displacement output by the two incremental linear displacement sensors respectively. A first incremental linear displacement sensor includes a first movable scale and a first fixed scale arranged in parallel and facing each other, with a gap between them. The first movable scale includes a first movable scale base and a first sensing electrode assembly disposed on the first movable scale base. The first fixed scale includes a first fixed scale base and a first excitation electrode assembly disposed on the first fixed scale base for N measurement cycles. The first excitation electrode assembly and the first sensing electrode assembly are signal-coupled. A second incremental linear displacement sensor includes a second movable scale and a second fixed scale arranged in parallel and facing each other, with a gap between them. The second movable scale includes a second movable scale base and a second sensing electrode assembly disposed on the second movable scale base. The second fixed scale includes a second fixed scale base and a second excitation electrode assembly disposed on the second fixed scale base for M measurement cycles. The second excitation electrode assembly and the second sensing electrode assembly are signal-coupled, and N and M are coprime numbers. The excitation module inputs excitation signals to the first excitation electrode assembly and the second excitation electrode assembly respectively through a switching circuit. The first sensing electrode assembly and the second sensing electrode assembly share a set of sensing signal processing interfaces and are connected to the sensing signal processing module. With the number of cycles N of the first incremental linear displacement sensor remaining unchanged, the number of cycles M of the second incremental linear displacement sensor is reduced to increase the positioning error limit, thereby making it easier to achieve absolute positioning while maintaining high accuracy.

2. An absolute linear displacement sensor structure, characterized in that, The system includes an excitation module, a first incremental linear displacement sensor, a second incremental linear displacement sensor, a switching circuit, and a sensing signal processing module. The first incremental linear displacement sensor includes a first moving scale and a first fixed scale arranged parallel to each other, with a gap between them. The first moving scale includes a first moving scale base and a first sensing electrode assembly disposed on the first moving scale base. The first fixed scale includes a first fixed scale base and a first excitation electrode assembly disposed on the first fixed scale base for N measurement cycles. The first excitation electrode assembly and the first sensing electrode assembly are signal-coupled. The second incremental linear displacement sensor includes a second moving scale and a second fixed scale arranged parallel to each other. There is a gap between them. The second movable ruler includes a second movable ruler base and a second sensing electrode assembly disposed on the second movable ruler base. The second fixed ruler includes a second fixed ruler base and a second excitation electrode assembly disposed on the second fixed ruler base for M measurement cycles. The second excitation electrode assembly and the second sensing electrode assembly are signal coupled, and N and M are coprime numbers. The excitation module inputs excitation signals to the first excitation electrode assembly and the second excitation electrode assembly respectively through the switching circuit. The first sensing electrode assembly and the second sensing electrode assembly share a set of sensing signal processing interfaces connected to the sensing signal processing module. The sensing signal processing module obtains absolute displacement data based on the received sensing signals to realize absolute displacement measurement.

3. The absolute linear displacement sensor structure according to claim 2, characterized in that, The first excitation electrode assembly includes a plurality of first excitation electrodes. The width of each first excitation electrode is W1, the spacing between two adjacent first excitation electrodes is I1, and four adjacent first excitation electrodes sequentially constitute a first measurement cycle. The length of the first measurement cycle is W. T1 The calculation formula is: W T1 =4*W1+4*I1, the total length of the first excitation electrode assembly of the first incremental linear displacement sensor is L1, and L1=W T1 *N = (4*W1 + 4*I1)*N; The second excitation electrode assembly includes multiple second excitation electrodes. The width of each second excitation electrode is W2, the spacing between two adjacent second excitation electrodes is I2, and four adjacent second excitation electrodes sequentially form a second measurement cycle. The length W of the second measurement cycle is... T2 The calculation formula is: W T2 =4*W2+4*I2, the total length of the second excitation electrode assembly of the second incremental linear displacement sensor is L2, and L2=W T2 *M = (4*W² + 4*I²)*M; And L1 = L2.

4. The absolute linear displacement sensor structure according to claim 3, characterized in that, The first sensing electrode assembly includes two double sinusoidal first sensing electrodes, both of which have a width of W. T1 / 2, both with a height of H1, and the distance between the center lines of the two double sinusoidal first sensing electrodes is W. T1 / 2; The second sensing electrode assembly includes two double sinusoidal second sensing electrodes, both of which have a width of W. T2 / 2, both with a height of H2, and the distance between the center lines of the two said double sinusoidal second sensing electrodes is W. T2 / 2.

5. The structure of the absolute linear displacement sensor according to claim 4, characterized in that, The two sinusoidal first sensing electrodes form a differential structure, and the phase difference between the induced signals output by the two sinusoidal first sensing electrodes is π. The output signal U is obtained by calculating the difference between the induced signals output by the two sinusoidal first sensing electrodes. O1 , and U O1 The calculation formula is: ； In the formula: M1 is the amplitude of the traveling wave signal of the first incremental linear displacement sensor; x1 is the relative displacement value between the first moving scale and the first fixed scale of the first incremental linear displacement sensor in a single measurement cycle; W T1 The length of the first measurement cycle of the first incremental linear displacement sensor; ω is the angular frequency of the excitation signal emitted by the excitation module; t represents time.

6. The structure of the absolute linear displacement sensor according to claim 4, characterized in that, The two sinusoidal second sensing electrodes form a differential structure, and the phase difference between the induced signals output by the two sinusoidal second sensing electrodes is π. The output signal U is obtained by calculating the difference between the induced signals output by the two sinusoidal second sensing electrodes. O2 , and U O2 The calculation formula is: ； In the formula: M2 is the amplitude of the traveling wave signal of the second incremental linear displacement sensor; x2 represents the relative displacement value between the second moving scale and the second fixed scale of the second incremental linear displacement sensor within a single measurement cycle; W T2 The length of the second measurement cycle of the second incremental linear displacement sensor; ω is the angular frequency of the excitation signal emitted by the excitation module; t represents time.

7. A method for operating an absolute linear displacement sensor, characterized in that, The absolute linear displacement sensor structure as described in claim 2 includes the following steps: Step 1) The excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor. The second sensing electrode assembly and the second excitation electrode assembly are directly coupled. The second sensing electrode assembly generates a second sensing signal and inputs it to the sensing signal processing module. Step 2) The excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through a switching circuit. The first sensing electrode assembly and the first excitation electrode assembly are directly coupled. The first sensing electrode assembly generates a first sensing signal and inputs it to the sensing signal processing module. Step 3) The induction signal processing module processes the first induction signal and the second induction signal to obtain absolute displacement data.

8. The method for operating an absolute linear displacement sensor according to claim 7, characterized in that, The excitation module applies excitation in time intervals to input sinusoidal excitation signals to the first incremental linear displacement sensor and the second incremental linear displacement sensor. In step 1), when the excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor, the first incremental linear displacement sensor does not work. In step 2), when the excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through the switching circuit, the second incremental linear displacement sensor does not work.

9. The method for operating an absolute linear displacement sensor according to claim 7, characterized in that, The first excitation electrode assembly includes multiple first excitation electrodes. Four adjacent first excitation electrodes sequentially constitute a first measurement cycle. The 4n1+1th first excitation electrode is connected to a group through the A1 phase excitation signal line to form the A1 excitation phase. The 4n1+2th first excitation electrode is connected to a group through the B1 phase excitation signal line to form the B1 excitation phase. The 4n1+3th first excitation electrode is connected to a group through the C1 phase excitation signal line to form the C1 excitation phase. The 4n1+4th first excitation electrode is connected to a group through the D1 phase excitation signal line to form the D1 excitation phase. Here, n1 takes all integers from 0 to N. The second excitation electrode assembly includes multiple second excitation electrodes, with four adjacent second excitation electrodes sequentially forming a second measurement cycle; and the 4n2+1th second excitation electrode is connected to a group through the A2 phase excitation signal line to form the A2 excitation phase, the 4n2+2nd second excitation electrode is connected to a group through the B2 phase excitation signal line to form the B2 excitation phase, the 4n2+3rd second excitation electrode is connected to a group through the C2 phase excitation signal line to form the C2 excitation phase, and the 4n2+4th second excitation electrode is connected to a group through the D2 phase excitation signal line to form the D2 excitation phase, wherein n2 sequentially takes all integers from 0 to M; In step 1), the excitation module inputs four sinusoidal excitation signals with phases successively differing by π / 2 to the second excitation electrode assembly of the second incremental linear displacement sensor, and the A1 excitation phase input sinusoidal excitation signal U S+ B1 excitation phase input sinusoidal excitation signal U C+ C1 is the excitation phase input sinusoidal excitation signal U S- D1 excitation phase input sinusoidal excitation signal U C- , and U S+ =Esin t, U C+ = Ecos t, U S− = −Esin t, U C− = −Ecos t; ω is the angular frequency of the excitation signal emitted by the excitation module; t is time; In step 2), the excitation module inputs four sinusoidal excitation signals with phases successively differing by π / 2 to the first excitation electrode assembly of the first incremental linear displacement sensor, and the A2 excitation phase inputs the sinusoidal excitation signal U. S+ B2 excitation phase input sinusoidal excitation signal U C+ C2 excitation phase input sinusoidal excitation signal U S- D2 excitation phase input sinusoidal excitation signal U C- .

10. The method for operating an absolute linear displacement sensor according to claim 7, characterized in that, In step 3), when the excitation module inputs a sinusoidal excitation signal to the second excitation electrode assembly of the second incremental linear displacement sensor and the first incremental linear displacement sensor is not working, the sensing signal processing module processes the sensing signal of the second incremental linear displacement sensor to obtain and store the second phase value ∆φ2. When the excitation module inputs a sinusoidal excitation signal to the first excitation electrode assembly of the first incremental linear displacement sensor through the switching circuit and the second incremental linear displacement sensor is not working, the sensing signal processing module processes the sensing signal of the first incremental linear displacement sensor to obtain and store the first phase value ∆φ1. The sensing signal processing module calculates the absolute displacement value based on the second phase value ∆φ2 and the first phase value ∆φ1.

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