Composite grating and absolute value displacement sensor

Abstract

The application discloses a composite grating ruler and an absolute value displacement sensor, which comprises a sensing head and a composite grating ruler. After the composite grating ruler and the sensing head are installed to a device to be measured, the sensing head can move relative to the length direction of the composite grating ruler. The composite grating ruler comprises a grating belt and a plurality of magnets. Each magnet is distributed along the length direction of the grating belt. At least two magnets have different magnetic field direction angles. The sensing head is integrated with a grating belt sensor and at least one magnetic field sensing module. During the movement of the sensing head along the length direction of the composite grating ruler, the grating belt sensor can cooperate with the grating belt to realize incremental displacement measurement, and the magnetic field sensing module can cooperate with the magnets to obtain the absolute position of the sensing head. The grating belt can cooperate with the sensing coil in the sensing head to realize displacement measurement, and the magnets can cooperate with the magnetic field sensing module in the sensing head to realize absolute value displacement measurement of displacement sensing.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically to a composite grating ruler. Background Technology

[0002] A displacement sensor is a device used to measure and record the distance moved by a moving part. Its working principle is mainly based on converting mechanical displacement into electrical signals or other forms of information output to meet the requirements of information transmission, processing, storage, display, recording and control.

[0003] Based on different measurement principles, current displacement sensors mainly include resistive displacement sensors, inductive displacement sensors, capacitive displacement sensors, photoelectric displacement sensors, and ultrasonic displacement sensors. With the continuous development of industrial automation, different fields are placing increasingly stringent requirements on the accuracy and precision of displacement sensor measurements. However, sensors based on existing measurement principles are almost all nearing their developmental limits, making it difficult to achieve significant technological breakthroughs in accuracy and precision.

[0004] To address this, the applicant has adopted a novel technical approach, developing a displacement sensor based on the principle of mutual inductance electromotive force (EMF) change in multiple coils. The physical principle of this sensor is as follows: a primary coil and a secondary coil are placed within the sensing head. When an oscillating current is applied, a mutual inductance EMF is generated between the primary and secondary coils. When a metallic target element approaches, the electromagnetic fields of the two coils are disturbed, causing a change in the mutual inductance EMF. This change is primarily related to the projected coverage area of ​​the primary and secondary coils relative to the target element. Based on this principle, if the secondary coil is printed as a function-type coil, and the target element is a long strip of grid with an array of grids on it, when the primary and secondary coils move linearly relative to the long strip of grid, the grid effectively reduces the thickness of the metal material at that location. Therefore, the mutual inductance EMF between the coils will definitely differ when the sensing head passes through gridded and non-gridded locations. Thus, as the sensing head moves along the length of the grid, the mutual inductance EMF between the coils changes according to the grid arrangement. Displacement measurement can then be obtained by calculating the displacement based on this change in mutual inductance EMF. Like other grid-type displacement sensors, grating-type displacement sensors can easily obtain absolute displacement values ​​within a small scale range, such as 0 to 10.24 mm, and then repeat this process to accumulate a large-scale incremental displacement sensing value. However, in practical applications, large-scale measurements often require absolute displacement sensing values. Therefore, it is necessary to confirm the position of the incremental displacement sensor within which grid segment it is located in order to obtain an absolute displacement sensing value.

[0005] In practical industrial applications, absolute displacement sensors are sensors that can directly measure the linear displacement of an object and output a unique digital coded signal corresponding to the displacement, finding wide applicability. In traditional products such as reflective gratings, sensing gratings, and capacitive sensors, absolute values ​​are typically measured and calculated using principles such as encoder disks, the Hall effect, and magnetoresistive effects, a relatively complex and cumbersome process. Furthermore, for sensors that measure displacement based on the change in mutual inductance electromotive force of multiple coils, there is no suitable absolute value measurement solution for large-size sensors. Therefore, it is extremely necessary to develop a new displacement sensing solution capable of acquiring absolute displacement data. Summary of the Invention

[0006] In view of this, the present invention provides a composite grating ruler, which aims to realize the absolute value measurement of displacement sensors.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A composite grating ruler, the key features of which are: a grating strip and a number of magnets, wherein the grating strip is used to cooperate with a sensing head for incremental displacement measurement, and each of the magnets is distributed along the length of the grating strip, wherein at least two of the magnets have different magnetic field direction angles, and the magnets are used to cooperate with a magnetic field sensing module for absolute position calculation.

[0009] Preferably, each magnet is assigned a serial number based on its magnetic field direction. The magnets are grouped into several magnetic groups, each group comprising at least two magnets. The serial numbers of each magnet within a group form a coding value, used as the group's identification code. This arrangement ensures a sufficient number of magnetic groups while maintaining a 20° difference in magnetic field orientation between adjacent magnets, making it easier for the magnetic field direction sensor to accurately identify the position.

[0010] Preferably, the magnetic group contains two or three magnets; and / or, at least two magnets in each magnetic group have different serial numbers.

[0011] The present invention also provides an absolute displacement sensor, including a sensing head and the composite grating. After the composite grating and the sensing head are installed on the device under test, the sensing head can move relative to the length direction of the composite grating. The sensing head integrates a grating strip sensor and at least one magnetic field sensing module. During the movement of the sensing head along the length direction of the composite grating, the grating strip sensor cooperates with the grating strip to perform incremental displacement measurement, and the magnetic field sensing module cooperates with a magnet to obtain the absolute position of the sensing head.

[0012] Using the aforementioned sensor, which integrates a grid strip and a magnet through a composite grid ruler, displacement measurement is achieved when the grid strip works in conjunction with the grid strip sensor inside the sensing head. On this basis, the magnet works in conjunction with the magnetic field sensing module inside the sensing head to identify the absolute position of the sensing head, thus realizing absolute displacement measurement of displacement sensing.

[0013] Preferably, the sensing head contains two magnetic field sensing modules, and the magnetic group contains two magnets. The distance between the two magnetic field sensing modules is less than or equal to the grid pitch of the grid strip. This design allows for the simultaneous reading of the direction values ​​of the magnetic fields of the two magnets, thereby quickly determining the segmented encoding value.

[0014] Preferably, the sensing head has four magnetic field sensing modules, and the distance between two adjacent magnetic field sensing modules is less than or equal to half of the grid pitch. This design ensures that at least two magnetic field sensors are within the effective magnetic field range of the magnet, enabling real-time segmented position determination. In this case, incremental grid positioning data is used to assist in determining which two magnetic field sensors are aligned with the magnet.

[0015] Preferably, the sensing head has 3, 4, 6 or 8 magnetic field sensing modules.

[0016] Preferably, the grid strip array along its length is provided with alternating metal segments and grids, and the grid strip sensor has at least two induction coils. When current is applied to the induction coils, mutual inductance electromotive force can be generated between the induction coils.

[0017] Preferably, the magnet is provided with a shielding cover, and the side of the shielding cover facing the magnetic field sensing module is open. This design can reduce magnetic field interference between magnets and external magnetic field interference. A magnetic field shielding cover is added to the magnet, which is open in the direction facing the magnetic direction detection chip, and provides shielding and constraint in other directions.

[0018] Preferably, the grating strip is a reflective grating, and the grating strip sensor is a photoelectric switch or a grating image sensor facing the grating grid.

[0019] Preferably, the grid strip includes a PCB board, and the metal segment is formed by printing metal foil on the PCB board; or, the grid strip is a metal strip, and the grid is a through hole or groove provided on the metal strip.

[0020] Preferably, the magnet is arranged on the back side of the grid strip and directly opposite the metal segment.

[0021] Preferably, the composite grid ruler further includes a base with an elongated structure, the upper side of which has a strip groove, each of the magnets is distributed on the bottom of the strip groove, a pad is installed in the strip groove, and the grid strip is located on the upper side of the pad.

[0022] Preferably, the metal segment and an adjacent grid form a sensing period, and each magnet is arranged in a different sensing period, and the positions of two adjacent magnets are different in the corresponding sensing period.

[0023] Preferably, the magnetic field directions of any two adjacent magnets are different.

[0024] Preferably, in the arrangement direction of each of the magnets, the angle of the magnetic field direction of the magnets changes in a monotonically increasing or decreasing manner.

[0025] Preferably, it also includes a magnetic strip with an elongated structure, wherein each of the magnets is formed by partial or intermittent magnetization of the magnetic strip.

[0026] Preferably, the magnet is arranged on the back side of the grid strip, and a magnetic permeable sheet is provided between the magnet and the grid strip.

[0027] Preferably, the magnets are arranged on both sides or the top of the grid strip.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. Using the composite grating ruler provided by this invention, by integrating the grating strip and the magnet, when performing displacement measurement, the grating strip cooperates with the sensing device in the sensing head to realize incremental displacement measurement. On this basis, the magnet cooperates with the magnetic field sensing module in the sensing head to identify the absolute position of the sensing head, thus realizing absolute displacement measurement of displacement sensing.

[0030] 2. By using the composite grid ruler provided by this invention, the magnet is arranged directly behind the metal part of the grid strip, which not only ensures that the magnetic induction intensity of the magnetic field sensing module is not affected, but also does not affect the mutual inductance electromotive force between the induction coils, thereby helping to improve the measurement accuracy and reliability of the displacement sensor.

[0031] 3. The composite grid ruler provided by this invention can be directly magnetically attached to the equipment by means of the magnetic force, making it convenient to use.

[0032] 4. By utilizing the changing dynamic relationship between the grating and the coil, a novel displacement sensing measurement method is provided, offering exceptionally high measurement accuracy. The inductive grating can achieve a resolution of up to 20nm, a crucial factor for high-quality motion control applications, such as micro-motion platforms. The inductive sensor boasts low output noise and high signal quality, resulting in an excellent overall signal-to-noise ratio. Furthermore, due to the presence of magnets within the composite grating, the magnetic field sensing module, in conjunction with the magnets, identifies the magnet the sensing module is positioned on during head movement, thereby calculating the absolute position of the sensing head and achieving absolute displacement measurement.

[0033] 5. In existing technologies, the magnetic orientation detection chip must always be directly facing the center of the magnet to detect its rotation direction. However, based on this application, the magnetic orientation detection chip can move away from the magnet. With the cooperation of another incremental sensing system, the chip can accurately measure the magnet's angle value whenever it is within an effective range near the center of the magnet. Furthermore, this range can also be determined by observing changes in the magnet's magnetic field strength.

[0034] 6. In existing technologies, the magnetic direction detection chip faces the magnet for angle measurement. However, based on this application, when the magnetic direction detection chip faces the magnet, it can measure the magnet's angle and thus determine the encoding of that segment. When the chip leaves the magnet's range, due to magnetic field weakening and adjacent intersections, the measured direction value is unreliable and will not be used for calculation. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the composite grating A.

[0036] Figure 2 This is an exploded view of composite grid ruler A.

[0037] Figure 3 This is a schematic diagram of a sensor for displacement measurement based on the variation law of mutual inductance electromotive force of multiple coils.

[0038] Figure 4 This is a schematic diagram showing the arrangement of magnet 2 relative to the grid band 1 to sense the grid period.

[0039] Figure 5 This is a schematic diagram showing the layout where the magnetic field direction of magnet 2 changes in an increasing manner.

[0040] Figure 6 This is a schematic diagram showing the arrangement of magnet 2 in 18 different orientations.

[0041] Figure 7 This is a schematic diagram of sensor head B.

[0042] Figure 8 This is a schematic diagram of the principle of an absolute value reflective grating measurement system.

[0043] Figure 9 This is a schematic diagram showing the positional relationship between magnet 2 and magnetic field sensing module 3, and between grid strip 1 and grid strip sensor m. Detailed Implementation

[0044] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0045] Example 1

[0046] like Figure 3 As shown, a displacement sensor mainly comprises two parts: a sensing head B and a composite grating A. After the composite grating A and the sensing head B are installed in the device under test, the sensing head B is arranged on one side of the composite grating A and can move relative to the length direction of the composite grating A. (See attached diagram.) Figure 2 It can be seen that the composite grating ruler A includes a grating strip 1 and a number of magnets 2. The grating strip 1 is a long strip-shaped sheet structure, with alternating metal segments 1b and grids 1a arranged along its length. Each magnet 2 is distributed along the length of the grating strip 1, and the distribution direction of the magnets 2 should be parallel to the length direction of the grating strip 1 in space. (See attached diagram.) Figure 7 As can be seen, the induction head B contains a magnetic field sensing module 3 and two induction coils a. In this embodiment, the two induction coils a are the main coil 6 and the secondary coil 7, respectively. The secondary coil 7 is a sinusoidal coil located inside the main coil 6. When an oscillating current is applied to the main coil 6, a mutual induced electromotive force can be generated between the main coil 6 and the secondary coil 7.

[0047] Based on the above structure, in practical applications, the composite grid ruler A is fixedly installed in the device under test, while the sensing head B is slidably installed within the device, ensuring that the induction coil a inside the sensing head B is directly opposite the grid strip 1. During operation, after an oscillating current is applied to the main coil 6, the sensing head B reciprocates relative to the composite grid ruler A. At the grid 1 position, the main and secondary coils have a mutual induced electromotive force (EMF). The remaining mutual EMF is shielded by the metal segment 1b. Since the secondary coil 7 is a sinusoidal coil, the mutual EMF between the main and secondary coils also exhibits a sinusoidal change during the movement of the sensing head B relative to the grid 1a. That is, the mutual EMF changes with the displacement of the grid 1a. Therefore, by calculating the displacement of the sensing head B based on the change in mutual EMF along the length of the grid strip 1 during its movement, the displacement of the sensing head B can be obtained, thus achieving displacement measurement of the target product. Based on this, since magnets 2 are distributed inside the composite grating A, during the movement of the sensing head B, the magnetic field sensing module 3 can identify which magnet 2 it is located on through the cooperation of the magnetic field sensing module 3 and the magnet 2, thereby calculating the absolute position of the sensing head B and realizing the absolute displacement measurement of displacement sensing.

[0048] There are two ways in which the magnetic field sensing module 3 and the magnet 2 can identify their location.

[0049] Method 1: Identify by layout distance relationship, please refer to the attached document. Figure 4 As shown, in the grating strip 1, a metal segment 1b and an adjacent grid 1a constitute a sensing cycle. Each magnet 2 is arranged within a different sensing cycle, and the positions of two adjacent magnets 2 within their respective sensing cycles are different. Specifically, within a sensing cycle, the cycle length data s is 0-1024, and the arrangement distance between the magnet 2 and the corresponding grating grid 1a is n. The value of n differs between adjacent magnets 2; for example, the n values ​​of two adjacent magnets 2 are 600 and 500, respectively. When the magnetic field sensing module 3 detects the center of the magnetic field, the corresponding data is 600, indicating that the current magnet center position is at sensing data 600; if the corresponding data is 500, the current magnet center position is at sensing data 500. Therefore, by querying a preset data table through the microcontroller, it can be determined which magnet 2 the sensing head B is passing through, thus completing the absolute displacement calculation. In addition, this method can also be used to determine displacement limit points and calculate calibration points.

[0050] If there is a magnet 2 in every sensing grating cycle, the corresponding data is more dense. If a magnet 2 is set at intervals of several cycles, then a certain distance needs to be traveled before the corresponding displacement data can be obtained. Once this data is obtained, the sensor can determine the specific absolute position and switch to absolute value working mode. This function allows the absolute position to be obtained without the motion returning to zero. For economic reasons, in this embodiment, a magnet 2 is arranged every three sensing grating cycles.

[0051] Method 2: Identification is achieved by varying the angles of the magnetic fields of the magnets. In this case, at least two magnets 2 have magnetic fields oriented differently. The magnetic field sensing module 3 acts as a magnetic field direction sensor. By identifying the direction of the magnetic field of the magnets 2, the specific position of the sensing head B on the composite grating can be determined, and the absolute value data can be calculated. For example, please refer to... Figure 5 As shown, the angle of the magnetic field direction of magnet 2 changes in a monotonically increasing or decreasing manner. Of course, as the simplest replacement form, in a composite scale, only the angles of the magnetic field directions of the two magnets 2 are different, which is sufficient to achieve the purpose of absolute value measurement.

[0052] Based on Method 2 above, a group coding method can also be used to locate and identify magnets. The coding arrangement is as follows: based on the difference in the magnetic field direction of magnet 2, all magnets 2 are assigned a serial number. Specifically, each direction angle corresponds to a serial number value. Then, magnets 2 are grouped into several magnetic groups, with each magnetic group containing at least two magnets 2. The serial numbers of each magnet 2 within a magnetic group form a coding value, which is used as the identification code for the magnetic group.

[0053] Example 1: Each magnetic group contains two magnets 2. The magnets 2 are numbered according to their orientation. The first magnet is numbered 0, and each subsequent magnet deflects by 20 degrees, numbered sequentially as 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, G. A practical coding arrangement is: G,0,2,1,3,0,4,1,5,0,6,1,7,0,8,1,9,0,A,1,B,0,C,1,D,0,E,1,F,0,H,1,G,2,4,3,5,2,6,3,7,2,8,3,9,2,A,3,B ,2,C,3,D,2,E,3,F,2,H,3,G,4,6,5,7,4,8,5,9,4,A,5,B,4,C,5,D,4,E,5,F,4,H,5,G,6,8,7,9,6,A,7,B,6,C,7,D,6,E,7,F,6,H,7,G,8,A,9,B,8,C,9,D,8,E,9,F,8,H,9,G,A,C,B,D,A,E,B,F,A,H,B,G,C,E,D,F,C,H,D,G,E,H,F,G,H. Then, randomly select two adjacent numbers from this to form a magnetic group. By adopting this magnet arrangement and encoding method, while ensuring a sufficient number of magnets are arranged, the difference in magnetic field orientation between adjacent magnets is also guaranteed to be 20°, thus making it easier for the magnetic field direction sensor to accurately identify the position.

[0054] Example 2: Each pair of magnets forms a group of two. Each magnet is numbered from 1 to N according to its magnetic field direction, and the numbering of the two magnets is unique. The adjacent magnets in any two groups are also unique in their numbering. For example, if the first magnet's direction code is 1 and the second is 2, the resulting number is 12. Without repetition, the second group of magnets is placed after the first group. The first magnet in the second group has a direction code of 1, and the second magnet has a direction code of 3, resulting in a number of 13. Since the first and second groups are adjacent, the consecutive numbers are 1, 2, 1, 3. Randomly selecting any two adjacent numbers yields (1, 2), (2, 1), and (1, 3), all with unique arrangements. The specific location can be determined using a magnetic field direction sensor. At this point, an incremental grating is used to determine the direction of movement, distinguishing data like (1, 2) and (2, 1) where the arrangements are different but the combination is the same.

[0055] Example 3: Each pair of magnets 2 forms a group. Each magnet 2 is numbered from 1 to N according to its magnetic field direction, and the numbering combination of two magnets 2 is unique. The numbering combination of adjacent magnets 2 between any two groups is also unique. For example, if the direction code of the first magnet 2 is 1 and the second is 2, the combined value is [1, 2]. With unique combined values, the second group of magnets 2 is arranged after the first group. The direction code of the first magnet 2 in the second group is 2, and the direction code of the second magnet 2 in the second group is 3, resulting in a combined value of [2, 3]. Since the first and second groups are adjacent, the consecutive values ​​are 1, 2, 2, 3. Randomly selecting any two adjacent values ​​yields [1, 2][2, 2][2, 3], with no repetition in the combinations. The specific location can be determined using a magnetic field direction sensor. In this case, the amount of combined data is less than that of arrangement 3, but it is not necessary to use an incremental grid to determine the direction of operation.

[0056] For example, in example 4: Group 3 magnets (2) together. Each group of magnets (2) has N=3 magnets. The first magnet (2) is fixed at a magnetic field angle of 0 degrees, serving as an index flag. The next two magnets (2) are encoded with M code values ​​based on different magnetic field directions (e.g., divided in 20-degree increments, resulting in 18 code values, M=18). However, the value 0 degrees cannot be used, as it is reserved for the index flag. Therefore, the next two magnets (2) can yield (18-1)*(18-1-1) = 272 codes. These 272 codes can then be arranged consecutively, resulting in 73712 permutations of the numbers 1-272. Combining these permutations yields 36856 combinations.

[0057] Please refer to the attached document. Figure 6 Using the width direction q of the composite grating as the baseline, the angle between the magnetic field direction of magnet 2 and the baseline is 20r°, where r is a natural number less than or equal to 17. Therefore, magnet 2 can be arranged in 18 different directions. These 18 magnets with different magnetic field directions are sequentially numbered 1, 2, 3…18. Assuming that the magnetic field orientations of two adjacent magnets 2 are different, a total of 307 permutations and combinations can be obtained. The magnet numbering, identification serial number, and corresponding segment code are shown in the table below. The identification serial number is composed of the magnet numbers corresponding to two adjacent magnets. If the latter magnet number is a single digit, a 0 is added before the serial number to ensure that the identification serial number is at least three digits.

[0058]

[0059]

[0060] Using this magnet arrangement and encoding method, similar to Example 1 above, while ensuring a sufficient number of magnets are arranged, it also guarantees that the difference in magnetic field orientation between adjacent magnets is 20°, thus making it easier for the magnetic field direction sensor to accurately identify the position.

[0061] In this embodiment, the spacing between two adjacent magnetic field sensing modules 3 is less than or equal to half the spacing between two adjacent magnets 2. This ensures that the magnetic field sensing modules 3 are arranged sufficiently closely, so that when the sensing head B is de-energized and stops at any position, there is always a magnetic field sensing module 3 facing one of the magnets 2. This ensures that upon restarting, the system can determine the absolute position within the system without moving the magnetic field sensing modules 3. A practical layout for this situation is: each incremental grid band interval is 10.24 mm, and a magnet is arranged every 10.24 mm. The magnet's size is 5×4×2, and the magnetized surface of the magnet is located on the two 5×2 mm surfaces. In this case, the effective magnetic field range is slightly larger than the magnet size, greater than 5.12 mm. Two practical layout structures are listed below:

[0062] Option 1: Simultaneously deploy two magnetic orientation detection chips, with a spacing of 5.12 mm between them. This ensures that at any given moment, at least one chip will pass through the effective magnetic field range of the magnet, measuring the encoded value of that segment. With this option, the magnetic field directions of adjacent magnets are different. If the difference is 20 degrees, it is relatively easy to distinguish, and the number of distinguishable segments is 360 ÷ 20 = 18, which is a relatively small number.

[0063] Option 2: Simultaneously deploy four magnetic orientation detection chips. The spacing between the magnetic field detection chips is 5.12 mm. This ensures that at any given time, at least two magnetic field detection chips will be aligned with the effective magnetic field range of the magnet. Since the magnet is coded according to the above pattern, the absolute value code at any position can be determined by the angle detection values ​​of two chips. This method allows for a larger number of codes and is more practical.

[0064] As for magnet 2, they don't need to be spaced too closely together; multiple incremental cycles can occur adjacent to each other. In this case, each magnet serves as a position index value. When the magnetic direction detection chip passes over this magnet, it knows the current absolute position. Since the incremental sensor is continuously working, it can perform direction determination and electronic counting. Therefore, based on this index value, the accurate absolute displacement can still be inferred through electronic counting. The disadvantage of this scheme is that after a power outage, when power is restored, the magnetic direction detection chip may not be aligned with the magnet. Therefore, the sensor head needs to move a certain distance to ensure that the absolute displacement index value is obtained. However, this only requires moving a small distance, unlike the traditional scheme which moves to the origin.

[0065] In this embodiment, the grid strip 1 and the induction coil a constitute an incremental encoder, and the magnet 2 and the magnetic field sensing module 3 constitute a magnetic absolute encoder. In particular, when multiple magnetic field sensing modules 3 are within the magnetic field range of the magnet 2, since the induction coil a is a functional coil, the cooperation between the magnetic field sensing module 3 and the induction coil a, while ensuring a sufficiently close arrangement of the magnetic field sensing modules 3, can also specifically locate and identify which magnetic field sensing module 3 is directly opposite the magnet 2, thereby significantly improving the accuracy of absolute positioning.

[0066] In other words, the magnet angle value measured by the magnetic chip is discontinuous, and it needs to be combined with the incremental sensing system b to output the final fused signal.

[0067] like Figure 1 As shown, the main body of the grid strip 1 is a PCB board, and the metal segments 1b are formed by printing metal foil on the PCB board. A grid 1a is formed between two adjacent metal segments 1b. Alternatively, the grid strip 1 can be a single metal strip, and the grid 1a can be a through hole or groove set on the metal strip.

[0068] For example Figure 2 As shown, the composite grid ruler A also includes a long strip-shaped base 4. The base 4 has a strip-shaped groove 4a on its upper side. Each of the magnets 2 is distributed on the bottom of the groove 4a. A pad 5 is installed inside the groove 4a, and the grid strip 1 is located on the upper side of the pad 5. This design provides a compact grid ruler product, and it can be directly magnetically attached to the device by means of the magnets, making it convenient to use.

[0069] In this embodiment, the magnet 2 is arranged on the back side of the grid strip 1 and directly opposite the metal segment 1b. In this way, the magnet 2 is covered behind the metal part of the grid strip, which does not affect the magnetic induction of the magnetic field sensing module 3, nor does it affect the mutual inductance electromotive force between the induction coils a, which helps to ensure the measurement accuracy and reliability of the displacement sensor.

[0070] Furthermore, a magnetic permeable sheet is provided between the magnet 2 and the grid strip 1 to weaken the magnetic field. This is suitable for situations requiring magnetic shielding and to reduce the signal impact caused by the magnetic field cutting the inductor sensor coil during high-speed operation.

[0071] Each magnet 2 can be an independent magnetic block. Alternatively, it can be a long, strip-shaped magnetic strip that is locally or intermittently magnetized to form individual magnets 2, achieving the same technical effect.

[0072] In the appendix Figure 7 In this paper, the magnetic field sensing module 3 and the induction coil a are arranged in series. It should be particularly emphasized that, in addition to the series arrangement, the oblique arrangement, side-by-side arrangement, etc., also fall within the protection scope of this application.

[0073] In the absolute displacement sensor, the magnetization direction of magnet 2 is parallel to the detection movement direction axis s, and the magnetic field direction detection surface of the magnetic field detection chip in the magnetic field sensing module 3 is also parallel to the detection movement direction axis s. Please refer to the appendix for details. Figure 9 As shown, the grid strip 1 extends along the direction axis s, and the magnets 2 are distributed below the grid strip 1 at a certain angle. During displacement detection, the magnetic field sensing module 3 and the grid strip sensor m move along the direction axis s. The magnetization direction of the magnets 2 and the magnetic field detection chip in the magnetic field sensing module 3 are parallel, and the grid strip 1 and the grid strip sensor m are parallel to each other. It is particularly important to note that, depending on different installation requirements, the absolute value detection component composed of magnets 2 and the magnetic field sensing module 3, and the incremental detection component composed of grid strip 1 and the grid strip sensor m, can be separate and arranged separately, only needing to be fixed together by connectors to maintain synchronous movement. Alternatively, the magnetic field sensing module 3 and the grid strip sensor m can be separate PCBs and circuits, simply fixed together to move synchronously in the same direction.

[0074] Example 2

[0075] like Figure 8 As shown, an absolute value reflective grating measurement system includes a sensing head B and a composite grating ruler A. After the composite grating ruler A and the sensing head B are installed on the device under test, the sensing head B can move relative to the length direction of the composite grating ruler A. A grating strip 1 has grids 8 distributed on it, and magnets 2 are distributed along the length direction of the grating strip 1. The sensing head B integrates a magnetic field sensing module 3 and a grating image sensor 9. The relative movement of the grating image sensor 9 with the grids 8 enables displacement measurement. The specific measurement principle is a mature existing technology and will not be elaborated here. Based on this, during the movement of the sensing head B along the length direction of the composite grating ruler A, the magnets 2 cooperate with the magnetic field sensing module 3 inside the sensing head to identify the absolute position of the sensing head, thus realizing the absolute displacement measurement of the reflective grating measurement system.

[0076] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A composite grid ruler (A), characterized in that: It includes a grid strip (1) and a number of magnets (2). The grid strip (1) is used to cooperate with the sensing head to perform incremental displacement measurement. Each magnet (2) is distributed along the length direction of the grid strip (1). At least two magnets (2) have different magnetic field direction angles. The magnets (2) are used to cooperate with the magnetic field sensing module to perform absolute position calculation. In each of the magnets (2), each magnet (2) is assigned a serial number according to the direction of the magnetic field; The magnets (2) are grouped into several magnetic groups, each magnetic group including at least two magnets (2). The serial numbers of each magnet (2) in the magnetic group form a coding value, which is used as the identification code of the magnetic group. The grid strip (1) is arrayed along its length with alternating metal segments (1b) and grids (1a). The grid strip sensor has at least two induction coils (a). When current is applied to the induction coils (a), mutual inductance electromotive force can be generated between the induction coils (a).

2. The composite grid ruler according to claim 1, characterized in that: The magnetic assembly contains two or three magnets (2); And / or, at least two magnets (2) in each magnetic group have different serial numbers.

3. An absolute displacement sensor, characterized in that: The device includes a sensor head (B) and a composite grating (A) as described in claim 1 or 2. After the composite grating (A) and the sensor head (B) are installed on the device under test, the sensor head (B) can move relative to the length direction of the composite grating (A). The sensing head (B) integrates a grid strip sensor and at least one magnetic field sensing module (3). As the sensing head (B) moves along the length direction of the composite grid ruler (A), the grid strip sensor cooperates with the grid strip (1) to perform incremental displacement measurement. The magnetic field sensing module (3) cooperates with the magnet (2) to obtain the absolute position of the sensing head (B).

4. The absolute displacement sensor according to claim 3, characterized in that: The sensing head (B) is provided with two magnetic field sensing modules (3), and the magnetic group contains two magnets (2). The distance between the two magnetic field sensing modules (3) is less than or equal to the grid pitch of the grid strip (1).

5. The absolute displacement sensor according to claim 3, characterized in that: The sensing head (B) is provided with four magnetic field sensing modules (3), and the distance between two adjacent magnetic field sensing modules (3) is less than or equal to half of the grid pitch of the grid strip (1).

6. The absolute displacement sensor according to claim 3, characterized in that: The sensing head (B) is equipped with 3, 4, 6 or 8 magnetic field sensing modules (3).

7. The absolute displacement sensor according to claim 6, characterized in that: The magnet is located on the back side of the metal portion of the grid strip (1).

8. The absolute displacement sensor according to claim 3, characterized in that: The grating (1) is a reflective grating, and the grating sensor is a photoelectric switch or grating image sensor facing the grating grid.

9. The absolute displacement sensor according to claim 3, characterized in that: The magnet is equipped with a shielding cover, and the side of the shielding cover facing the magnetic field sensing module is an open structure.

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