Method for measuring absolute stroke of ceramic piston rod

Abstract

The invention provides a method for measuring the absolute stroke of a ceramic piston rod, and the method comprises the steps: carrying out the grooving of a piston rod according to different grooving depths, so as to form a plurality of grooves; setting a plurality of sensors as array sensors for acquiring a unique code; and decoding the code according to a decoding rule to obtain absolute stroke information of the piston rod. The evenly distributed racks are arranged on the piston rod, the grooves are formed between the adjacent racks, each groove corresponds to a binary number, and the binary number is converted into stroke information of the piston rod in a coding mode. The staggered array sensor is adopted, high-precision absolute position measurement is achieved, accumulative errors are avoided, a large-range coding area does not need to be designed on the piston rod for marking, the coding mode does not need partitioning, the information density of grooving is greatly improved within the same range through the method, the detection area can be reduced, and the detection efficiency is improved. Therefore, the size of the sensor is reduced, and the sensor is also suitable for a small oil cylinder with higher integration level.

Description

Technical Field

[0001] The invention relates to the technical field of piston rod stroke measurement, and in particular to a method for measuring the absolute stroke of a ceramic piston rod. Background Art

[0002] In the fields of modern industrial automation, precision manufacturing and high-precision measurement, piston rod stroke measurement technology is crucial. Ceramic piston rods are widely used in high-precision hydraulic systems, semiconductor equipment, medical equipment, aerospace and other fields due to their excellent properties such as high strength, wear resistance, corrosion resistance and low thermal expansion coefficient. Piston rod stroke measurement is usually divided into two methods: relative measurement and absolute measurement. Relative measurement is to measure the relative displacement of the piston rod through an incremental encoder or sensor, but it requires reference point initialization and cannot directly obtain the absolute position; absolute measurement can directly obtain the absolute position of the piston rod when the system starts, which is suitable for high-precision and high-reliability application scenarios. In order to achieve piston rod stroke measurement, it is usually necessary to embed a coding mark on the surface or inside of the piston rod. Common methods include optical coding, engraving optical coding patterns on the surface of the piston rod, such as barcodes and QR codes, and reading position information through optical sensors; magnetic coding is to add magnetic materials to the piston rod and use magnetic encoders to read magnetic field changes to determine the position; capacitive coding uses the insulating properties of ceramic materials to design capacitive coding structures on the surface or inside to measure the position through capacitance changes. Coding is a commonly used digital coding method with the advantages of simplicity, easy implementation and processing. By converting the stroke of the piston rod into a code, the stroke position can be accurately represented and transmitted. Common coding methods include Gray code, BCD code, etc. These coding methods have their own advantages and disadvantages and need to be selected according to the needs of the actual application scenario. For example, Gray code can effectively reduce the error rate during data transmission because only one bit is different between two adjacent codes; Manchester code and differential Manchester code can provide synchronization information while transmitting data.

[0003] Chinese patent CN101280796B discloses an absolute stroke detection method and device used in combination with a ceramic piston rod. The method divides the piston rod detection section into multiple continuous sections along the axial direction, and sets a set of marks in each section. This set of marks can be identified by the sensor and converted into a unique set of codes. The sensor is used to read the codes of each mark at the current position, and then the code read by the sensor is decoded and identified to know the section where the sensor is located and the position offset of the sensor relative to the section where the sensor is located. The current absolute position of the sensor can be obtained by combining the section where the sensor is located with the position offset of the sensor relative to the section where the sensor is located; the sensor is an active magnetic detection type, and the marks on the piston rod are presented as a series of regular grooves and convex rings. However, this method uses convex rings and tooth positions of different widths to divide the piston rod detection section, which cannot meet the needs of larger range or more precise stroke detection. For longer strokes or higher resolutions, this encoding method may not be flexible enough. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for measuring the absolute stroke of a ceramic piston rod, so as to solve the problem that the detection area on the piston rod is too large and the encoding method needs to be partitioned, resulting in low universality of the measurement method and low information density.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for measuring the absolute stroke of a ceramic piston rod, the method comprising: S1. Grooving the piston rod to form a plurality of grooves according to different groove depths; S2, setting the multiple sensors as array sensors to obtain unique codes; S3. Decode the code according to the decoding rules to obtain the absolute stroke information of the piston rod.

[0006] In a preferred embodiment, the array sensor includes a plurality of staggered single-row sensors, which are used to obtain binary digital values; the single-row sensor includes a plurality of sensors arranged side by side, which are used to obtain binary numbers of corresponding grooves; the encoding includes a plurality of binary digital values, and each binary digital value includes a plurality of binary numbers.

[0007] In the preferred embodiment, when the single-row sensor acquires a binary digital value, the piston rod moves relatively by a complete groove, and the binary digital value before the movement is different from the binary digital value after the movement.

[0008] In the preferred embodiment, the number of bits encoded is strongly correlated with the travel distance covered, and each binary digital value is composed of 8, 12 or 16 binary digits.

[0009] In a preferred embodiment, the array sensor is arranged in parallel with the piston rod, and the sensor is located close to and aligned with the groove so that the sensor detects the groove.

[0010] In a preferred embodiment, in step S1, grooves are cut on the piston rod to obtain evenly distributed racks, and grooves are formed between adjacent racks, each groove corresponding to a binary number.

[0011] In a preferred embodiment, the grooves include shallow grooves and deep grooves, the depth of the shallow grooves is less than the depth of the deep grooves, and the shallow grooves and the deep grooves are randomly distributed and correspond to different binary numbers respectively.

[0012] In the preferred embodiment, the width of the rack and the groove is 2 mm, the depth of the shallow groove is 1 mm, and the depth of the deep groove is 2 mm.

[0013] In the preferred embodiment, the first single row of sensors is located at the bottom of the array sensor, and the other single row of sensors are arranged from bottom to top. The decoding rule is based on the position of the first single row of sensors, and the other single row of sensors are used to calibrate the positions of adjacent single row of sensors.

[0014] In the preferred solution, four single-row sensors are arranged with a 1mm offset to form an array sensor, the decoding rule is based on the first single-row sensor being in the zero position, and each single-row sensor has four consecutively acquired binary digital values ​​as a change cycle; The absolute stroke value of the piston rod is ; Wherein, M is the cycle number of the first single-row sensor, M is a positive integer; k is the position of the single-row sensor where the binary digital value changes, and the positions of the four single-row sensors are .

[0015] The present invention provides a method for measuring the absolute stroke of a ceramic piston rod. The method grooves the piston rod according to different groove depths to form multiple grooves; multiple sensors are set as array sensors to obtain unique codes; the codes are decoded according to decoding rules to obtain the absolute stroke information of the piston rod. Evenly distributed racks are provided on the piston rod, and grooves are formed between adjacent racks. Each groove corresponds to a binary number, which is converted into the stroke information of the piston rod in the form of code. The staggered array sensor is used to achieve high-precision absolute position measurement, avoid cumulative errors, and does not need to design a large-scale coding area on the piston rod for measurement, so that within the same range, the information density of the grooves carved by the coding arrangement and decoding method is greatly improved, and almost the same information density as the equidistant grooves of the pulse incremental built-in stroke detection method is achieved, which helps to reduce the detection area, thereby reducing the volume of the sensor, so that its application range is not limited to large equipment, but also suitable for small oil cylinders with higher integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 is a flow chart of the method of the present invention; Figure 2 Schematic diagram of the rack and groove of the piston rod of the present invention; Figure 3 is a schematic diagram of an array sensor of the present invention; Figure 4 is a schematic diagram of a single row sensor of the present invention; In the figure: piston rod 1; rack 2; groove 3; shallow groove 301; deep groove 302; sensor 4; single row sensor 5; array sensor 6. DETAILED DESCRIPTION

[0017] Embodiment 1: like Figures 1 to 4 As shown, a method for measuring the absolute stroke of a ceramic piston rod comprises: S1, groove the piston rod 1 to form a plurality of grooves 3 according to different groove depths; S2, setting the plurality of sensors 4 as array sensors 6 to obtain a unique code; S3. Decode the code according to the decoding rule to obtain the absolute stroke information of the piston rod 1.

[0018] According to this scheme, the piston rod 1 in this embodiment is a ceramic piston rod 1, which is provided with a ceramic material with high strength, wear resistance and good thermal stability. The piston rod 1 is grooved using precision machining technology or laser engraving technology, and grooves 3 of varying depths are obtained by precision machining, and each groove 3 corresponds to a binary number. According to the stroke measurement range required by the piston rod 1, the number of binary digits of the code is determined, and the binary numbers of the continuous grooves 3 are obtained in real time by the array sensor 6, so as to obtain a set of unique codes. The codes are decoded using a preset decoding rule, and the obtained codes are converted into the absolute stroke information of the piston rod 1. In this method, the grooves (3) are used as codes to form the stroke information of the piston rod (1), and the array sensor 6 and its coding arrangement are used to achieve high-precision absolute position measurement. It is not necessary to mark a large area of ​​the piston rod 1, and its coding method does not need to be partitioned, so that within the same measurement range, the information density of the method is greatly improved, and almost the same information density as the equidistant grooves of the pulse incremental built-in stroke detection method is achieved. Since there is no need to design a large coding area on the piston rod 1 for measurement, the detection area is greatly reduced, which means that the size of the sensor 4 is also reduced, so that its application scope is not limited to large equipment, but can also be applied to small cylinders with higher integration.

[0019] In the preferred embodiment, the array sensor 6 includes a plurality of staggered single-row sensors 5, which are used to obtain binary digital values; the single-row sensor 5 includes a plurality of sensors 4 arranged side by side, which are used to obtain the binary numbers of the corresponding grooves 3; the encoding includes a plurality of binary digital values, and each binary digital value includes a plurality of binary numbers.

[0020] According to this scheme, each sensor 4 reads a binary number corresponding to a groove 3, and multiple sensors 4 are arranged side by side to form a single-row sensor 5, and multiple binary numbers are continuously read to form a binary digital value; multiple single-row sensors 5 are arranged from bottom to top in a staggered manner to form an array sensor 6, and multiple binary digital values ​​obtained in sequence form a code, and the code includes at least one valid binary digital value. Multiple single-row sensors 5 staggered from bottom to top form an array sensor 6, which is used to improve the measurement resolution and ensure that the code obtained by the array sensor 6 is unique; adjacent single-row sensors 5 partially overlap to enhance the accuracy of the measurement and prevent errors in the reading of the groove 3 when the excitation magnetic field is too strong. Preferably, four staggered single-row sensors 5 are arranged to increase the density and information content of the code.

[0021] In the preferred embodiment, when the single-row sensor 5 obtains a binary digital value, the piston rod 1 moves a complete groove 3 relatively, and the binary digital value before the movement is different from the binary digital value after the movement. According to this scheme, each time the piston rod 1 moves a complete groove 3, the first sensor 4 reads a valid binary number, and the other sensors 4 read in turn until all the single-row sensors 5 have completed reading and formed a valid binary digital value. If the sensor 4 does not detect a complete groove 3, the binary number obtained is invalid, that is, the formed binary digital value is invalid. For example, when the piston rod 1 is at 0㎜, the binary digital value read by the single-row sensor 5 is 00000000; after the piston rod 1 moves a complete groove 3 to the right, the binary digital value read becomes 00000001.

[0022] In the preferred solution, the number of bits of the code is strongly correlated with the covered stroke, and each binary digital value is composed of 8, 12 or 16 binary bits. According to this solution, the larger the number of bits of the binary digital value, the larger the number of bits of the composed code, so that there are more permutations of the code, the stroke position that can be obtained increases exponentially, and the maximum stroke value that can be measured also increases exponentially. Preferably, when the binary digital value is composed of 8 binary bits, there are 256 permutations of the binary digital value, and the stroke covered by the single-row sensor 5 is 1.024m; when the binary digital value is composed of 12 binary bits, the stroke covered by the single-row sensor 5 is 16.384m.

[0023] Embodiment 2: Further illustrate with reference to Example 1, Figures 1 to 4 As shown, in the preferred embodiment, the array sensor 6 is arranged in parallel with the piston rod 1, and the sensor 4 is located close to and aligned with the groove 3, so that the sensor 4 detects the complete groove 3 and obtains the binary number corresponding to the groove 3. According to this scheme, the array sensor 6 is arranged on the cylinder near the piston rod 1, and a gap is provided between the array sensor 6 and the rack 2, and the stroke displacement of the piston rod 1 is detected in a non-contact manner to avoid friction and collision during movement. If the sensor 4 detects a complete groove 3 and reads the corresponding binary number as valid, a valid code is formed; if the sensor 4 detects an incomplete groove 3 and reads the corresponding binary number as invalid, an invalid code is formed. Preferably, the array sensor 6 transmits the coded information to other control systems for information conversion and monitoring control through a wired or wireless connection.

[0024] In the preferred solution, in step S1, grooves are cut on the piston rod 1 to obtain uniformly distributed racks 2, and grooves 3 are formed between adjacent racks 2, and each groove 3 corresponds to a binary number. According to this solution, precise machining technology or laser engraving technology is used to obtain uniformly distributed raised racks 2, and the spacing between adjacent racks 2 is equal, and grooves 3 of different depths are formed; each groove 3 corresponds to a binary number, so that the binary numbers corresponding to the continuous grooves 3 constitute a binary digital value. Preferably, a magnetic material is provided on the groove 3, and a Hall sensor 4 is used to measure the change in magnetic field strength. Grooves 3 of different depths will produce different changes in magnetic field strength, thereby obtaining the binary number corresponding to the groove 3.

[0025] In the preferred embodiment, the groove 3 includes a shallow groove 301 and a deep groove 302, the depth of the shallow groove 301 is less than the depth of the deep groove 302, and the shallow groove 301 and the deep groove 302 are randomly distributed, corresponding to different binary numbers. According to this scheme, the shallow groove 301 and the deep groove 302 are irregularly distributed on the piston rod 1 to increase the complexity and uniqueness of the coding. When the piston rod 1 moves a complete groove 3, the sensor 4 accurately distinguishes the shallow groove 301 and the deep groove 302 according to the depth difference between the shallow groove 301 and the deep groove 302, and reads the corresponding binary number, which is combined into a unique code to achieve the stroke measurement of the piston rod 1. Preferably, a single shallow groove 301 corresponds to the binary number 0, and a single deep groove 302 corresponds to the binary number 1. The use of binary numbers effectively reduces the redundancy of the coding and improves the measurement efficiency and accuracy.

[0026] In the preferred solution, the width of the rack 2 and the groove 3 are both 2 mm, the depth of the shallow groove 301 is 1 mm, and the depth of the deep groove 302 is 2 mm. According to this solution, the rack 2 and the groove 3 are designed with the same width, which is convenient for subsequent decoding of the code, and accurate absolute stroke information of the piston rod 1 is obtained, thereby improving universality. Accurate width setting can achieve a higher coding density while ensuring measurement accuracy.

[0027] Embodiment 3: Further explanation is given in combination with Examples 1 and 2. In the preferred solution, the first single-row sensor 5 is located at the bottom of the array sensor 6, and the other single-row sensors 5 are arranged in sequence from bottom to top. The decoding rule is based on the position of the first single-row sensor 5, and the other single-row sensors 5 are used to calibrate the positions of adjacent single-row sensors 5. According to this solution, the staggered single-row sensors 5 are used to calibrate the binary digital value of the adjacent previous single-row sensor 5, correct the actual stroke value, and avoid misreading and affecting subsequent measurements.

[0028] In the preferred solution, four single-row sensors 5 are arranged with a 1mm offset to form an array sensor 6. The decoding rule is based on the first single-row sensor 5 being in the zero position. Each single-row sensor 5 has four consecutively acquired binary digital values ​​as a change cycle. The absolute stroke value of piston rod 1 is ; Wherein, M is the cycle number of the first single-row sensor 5, M is a positive integer; k is the position of the single-row sensor 5 where the binary digital value changes, and the positions of the four single-row sensors 5 are respectively .

[0029] According to this scheme, each single-row sensor 5 takes four consecutively acquired binary digital values ​​as a change cycle. When the first single-row sensor 5 detects a complete new groove 3, the first binary digital value changes and enters a new cycle. If a single-row sensor 5 does not completely detect the groove 3, the binary digital value is marked as invalid, but it does not affect the decoding of the current code. For example, when the array sensor 6 reads 0mm, 1mm, 2mm, and 3mm, the first binary digital value obtained remains relatively unchanged, and the first single-row sensor 5 is in the first cycle; when the array sensor 6 reads 4mm, the first binary digital value changes, and the first single-row sensor 5 enters a new cycle, namely the second cycle; and so on, other single-row sensors 5 also follow the periodic changes.

[0030] If the first single-row sensor 5 is in the first cycle, the cycle number , the absolute stroke value of piston rod 1 is If the first single-row sensor 5 is in the Mth cycle, the cycle number M is a positive integer, and the absolute stroke value of the piston rod 1 is Wherein, k is the position of the single-row sensor 5 where the binary digital value changes, with the first single-row sensor 5 being at zero as the reference, that is, the position of the first single-row sensor 5 is , the second single-row sensor 5 is located at , the third single-row sensor 5 is located at , the fourth single-row sensor 5 is located at Thus, a unique set of codes can be obtained through the array sensor 6 and converted into the absolute stroke information of the piston rod 1 according to the decoding rules.

[0031] Embodiment 4: The above decoding rules are further explained in combination with Examples 1 to 3. Preferably, the array sensor 6 includes four single-row sensors 5 arranged with a 1mm offset, and each single-row sensor 5 includes eight sensors 4 arranged side by side. If there are 263 grooves 3 on the piston rod 1, the binary number corresponding to each groove 3 is: 00000000111111110111111001111110101111100011110110110111100101111000011101110110011101010111010001110011011100100111000101110000101110000 011011010110110001101010011010010110100001100110010101001000110000101100000010101010001010010000010010001000000100010000000.

[0032] The binary digital value obtained by the single-row sensor 5 consists of 8-bit binary numbers. Some binary digital values ​​of the single-row sensor 5 are shown in Table 1.

[0033] Table 1 Partial table of binary digital values ​​of single-row sensor 5

[0034] Table 2 Partial table of decoding rules

[0035] The decoding rules follow the following logic: Taking the position of the first single-row sensor 5 as a reference, the decoding rules are shown in Table 2; when the first single-row sensor 5 is at the 0mm position, the first single-row sensor 5 reads the first binary digital value as 00000000; the second, third and fourth single-row sensors 5 do not detect the complete groove 3, and the read binary digital values ​​are invalid, and the first single-row sensor 5 is in the first cycle; When the array sensor 6 reads 1mm, the first single-row sensor 5 does not detect other complete grooves 3, the first binary digital value does not change and remains 00000000; the second binary digital value changes, and the second single-row sensor 5 reads the second binary digital value as 00000000; the third and fourth single-row sensors 5 do not detect complete grooves 3, and the read binary digital values ​​are invalid; the first single-row sensor 5 is in the first cycle, and the first single-row sensor 5 and the second single-row sensor 5 are offset by 1mm; When the array sensor 6 reads 2mm, the first single-row sensor 5 does not detect other complete grooves 3, the first binary digital value does not change and remains as 00000000; the second single-row sensor 5 does not detect other complete grooves 3, the second binary digital value does not change and remains as 00000000; the third binary digital value changes, and the third single-row sensor 5 reads the third binary digital value as 00000000; the fourth single-row sensor 5 does not detect a complete groove 3, and the read binary digital value is invalid; the first single-row sensor 5 is in the first cycle, the first single-row sensor 5 and the second single-row sensor 5 are arranged with a 1mm offset, and the second single-row sensor 5 and the third single-row sensor 5 are arranged with a 1mm offset; When the array sensor 6 reads 3mm, the first single-row sensor 5 does not detect other complete grooves 3, the first binary digital value does not change and remains as 00000000; the second single-row sensor 5 does not detect other complete grooves 3, the second binary digital value does not change and remains as 00000000; the third single-row sensor 5 does not detect other complete grooves 3, the third binary digital value does not change and remains as 00000000; the fourth binary digital value changes, and the fourth single-row sensor 5 reads the fourth binary digital value as 00000000; the first single-row sensor 5 is in the first cycle, the first single-row sensor 5 and the second single-row sensor 5 are arranged with a 1mm offset, the second single-row sensor 5 and the third single-row sensor 5 are arranged with a 1mm offset, and the third single-row sensor 5 and the fourth single-row sensor 5 are arranged with a 1mm offset; When the array sensor 6 reads 4 mm, the first single-row sensor 5 detects other complete grooves 3, the first binary digital value changes, and is read as 00000001; the second single-row sensor 5 does not detect other complete grooves 3, the second binary digital value does not change, and remains as 00000000; the third single-row sensor 5 does not detect other complete grooves 3, the third binary digital value does not change, and remains as 00000000; the fourth single-row sensor 5 does not detect other complete grooves 3, the fourth binary digital value does not change, and remains as 00000000; the first single-row sensor 5 is in the second cycle; When the array sensor 6 reads 5mm, the first single-row sensor 5 detects no other complete grooves 3, the first binary digital value remains unchanged and remains 00000001; the second single-row sensor 5 detects other complete grooves 3, the second binary digital value changes and is read as 00000001; the third single-row sensor 5 detects no other complete grooves 3, the third binary digital value remains unchanged and remains 00000000; the fourth single-row sensor 5 detects no other complete grooves 3, the fourth binary digital value remains unchanged and remains 00000000; the first single-row sensor 5 is in the second cycle.

[0036] By analogy, according to the above logic, the decoding rule is obtained, and the code after the displacement of the piston rod 1 is obtained by the array sensor 6. The code is composed of four binary digital values ​​obtained by four single-row sensors 5, and each binary digital value is composed of eight binary numbers. The unique code obtained is decoded by the decoding rule, for example: If the read code consists of the first binary digital value of 00000000, the second binary digital value of 00000000, the third binary digital value of 00000000, and the fourth binary digital value of 00000000: according to the decoding rule, based on the first binary digital value of 00000000, the first single-row sensor 5 is in the first cycle, then the cycle number The fourth binary digital value changes relative to the fourth binary digital value of the previous set of codes, and the fourth single-row sensor 5 is located at , then the absolute stroke value of piston rod 1 is ; If the read code consists of the first binary digital value of 00000111, the second binary digital value of 00000111, the third binary digital value of 00000011, and the fourth binary digital value of 00000011: according to the decoding rule, based on the first binary digital value of 00000111, the first single-row sensor 5 is in the 4th cycle, then the cycle number ; The second binary digital value changes relative to the second binary digital value of the previous set of codes, and the second single-row sensor 5 is located at , then the absolute stroke value of piston rod 1 is .

[0037] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for measuring the absolute stroke of a ceramic piston rod, characterized in that: The method includes: S1, grooves are cut on the piston rod (1) to form a plurality of grooves (3) according to different groove depths; S2, setting the plurality of sensors (4) as an array sensor (6) to obtain a unique code; S3. Decode the code according to a decoding rule to obtain absolute stroke information of the piston rod (1).

2. According to claim 1, a ceramic piston rod absolute stroke measurement method is characterized by: The array sensor (6) includes a plurality of single-row sensors (5) arranged in a staggered manner, the single-row sensors (5) being used to obtain binary digital values; the single-row sensor (5) includes a plurality of sensors (4) arranged side by side, the sensors (4) being used to obtain binary numbers corresponding to the grooves (3); The code includes a plurality of binary digital values, and each binary digital value includes a plurality of binary numbers.

3. According to claim 2, a ceramic piston rod absolute stroke measurement method is characterized by: When the single-row sensor (5) acquires a binary digital value, the piston rod (1) moves relatively by a complete groove (3), and the binary digital value before the movement is different from the binary digital value after the movement.

4. According to claim 2, a ceramic piston rod absolute stroke measurement method is characterized by: The number of bits encoded is strongly related to the covered stroke, with each binary digit value consisting of 8, 12 or 16 binary bits.

5. The method for measuring the absolute stroke of a ceramic piston rod according to claim 1, characterized in that: The array sensor (6) is arranged in parallel with the piston rod (1), and the sensor (4) is located close to and aligned with the groove (3), so that the sensor (4) detects the groove (3).

6. According to claim 1, a ceramic piston rod absolute stroke measurement method is characterized in that: In step S1, grooves are cut on the piston rod (1) to obtain evenly distributed racks (2), and grooves (3) are formed between adjacent racks (2), and each groove (3) corresponds to a binary number.

7. A method for measuring the absolute stroke of a ceramic piston rod according to claim 6, characterized in that: The grooves (3) include shallow grooves (301) and deep grooves (302). The depth of the shallow grooves (301) is less than the depth of the deep grooves (302). The shallow grooves (301) and the deep grooves (302) are randomly distributed and correspond to different binary numbers.

8. A ceramic piston rod absolute stroke measurement method according to claim 7, characterized in that: The widths of the rack (2) and the groove (3) are both 2 mm, the depth of the shallow groove (301) is 1 mm, and the depth of the deep groove (302) is 2 mm.

9. A method for measuring the absolute stroke of a ceramic piston rod according to any one of claims 1 to 8, characterized in that: The first single-row sensor (5) is located at the bottom of the array sensor (6), and the other single-row sensors (5) are arranged in sequence from bottom to top. The decoding rule is based on the position of the first single-row sensor (5), and the other single-row sensors (5) are used to calibrate the positions of adjacent single-row sensors (5).

10. A ceramic piston rod absolute stroke measurement method according to claim 9, characterized in that: Arrange four single-row sensors (5) with a 1mm offset to form an array sensor (6), wherein the decoding rule is based on the first single-row sensor (5) being in the zero position, and each single-row sensor (5) has four consecutively acquired binary digital values ​​as one change cycle; The absolute stroke of the piston rod (1) is ; wherein M is the cycle number of the first single-row sensor (5), and M is a positive integer; k is the position of the single-row sensor (5) where the binary digital value changes, and the positions of the four single-row sensors (5) are respectively .

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