Composite grating ruler and absolute value displacement sensor

Abstract

The invention discloses a composite grating ruler and an absolute value displacement sensor, the composite grating ruler comprises an inductive head and a composite grating ruler, after the composite grating ruler and the inductive head are installed on a device to be measured, the inductive 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, the magnets are distributed in the length direction of the grating belt, the magnetic field direction angles of at least two magnets are different, the inductive head is integrated with a grating belt sensor and at least one magnetic field sensing module, and in the process that the inductive head moves in the length direction of the composite grating ruler, the magnetic field direction angles of the magnets are different. The grid belt sensor is matched with the grid belt to carry out incremental displacement measurement, and the magnetic field sensing module is matched with the magnet to obtain the absolute position of the inductive head. The beneficial effects are that the grating belt is matched with the induction coil in the induction head to realize displacement measurement, and the magnet is matched with the magnetic field sensing module in the induction head to realize absolute value displacement measurement of displacement sensing.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly relates to a composite grating scale. Background Art

[0002] A displacement sensor is a component used to measure and record the moving distance of a moving part. Its working principle is mainly based on converting mechanical displacement into an electrical signal or other forms of information output to meet requirements such as 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, optoelectronic displacement sensors, ultrasonic displacement sensors, etc. With the continuous development of industrial automation, more stringent requirements have been put forward for the measurement accuracy and precision of displacement sensors in different fields. However, sensors based on the existing measurement principles have almost reached the development limit, and it is difficult to achieve obvious technological breakthroughs in terms of accuracy and measurement precision.

[0004] Therefore, the applicant has developed a new type of displacement sensor that detects based on the principle of the change in mutual inductance electromotive force of multiple coils by taking a different technical route. The physical principle of such a sensor is as follows: a primary coil and a secondary coil are arranged in the induction head. When an oscillating current is applied, a mutual inductance electromotive force will be generated between the primary and secondary coils. When a metal target element approaches, due to the disturbance of the electromagnetic fields of the two coils, the mutual inductance electromotive force changes. This change is mainly 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 into a functional coil and the target element uses a long strip grating scale with grids arranged in an array on the grating scale, when the primary and secondary coils linearly move relative to the long strip grating scale, since the grid is equivalent to reducing the thickness of the metal material of the grating scale at that position, the mutual inductance electromotive force between the induction coils will definitely be different when the induction head passes through the grid position and the non-grid position. Therefore, during the movement of the induction head along the length direction of the grating scale, the mutual inductance electromotive force between the induction coils can change according to the arrangement rule of the grids, and then by performing displacement conversion on the change rule of the mutual inductance electromotive force, the displacement measurement can be obtained. Similar to other grating type displacement sensors, the inductive grating displacement sensor can easily obtain an absolute displacement value within a relatively small scale range, such as 0 to 10.24 millimeters, and then repeat continuously to accumulate a large-scale incremental displacement sensing value. However, in actual applications, large scales often require absolute displacement sensing values. Therefore, it is necessary to confirm the position of the incremental displacement sensor on which section of the grid to obtain the absolute displacement sensing value.

[0005] In actual industrial applications, an absolute displacement sensor is a sensor that can directly measure the linear displacement of an object and output a unique digital encoded signal corresponding to the displacement, and has a large number of usage scenarios. In traditional products such as reflective gratings, inductive gratings, and capacitive sensors, the absolute value is usually measured and calculated using principles such as encoding disks, Hall effects, and magnetoresistive effects, and the process is relatively complex and cumbersome. At the same time, for sensors that measure displacement based on the change in the mutual inductance electromotive force of multiple coils, there is no good absolute value measurement scheme for large sizes. Therefore, it is extremely necessary to re-develop a displacement sensing scheme that can obtain absolute displacement data. Summary of the Invention

[0006] In view of this, the present invention provides a composite grating scale, aiming to achieve the absolute value measurement of a displacement sensor.

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

[0008] A composite grating scale, characterized in that: it includes a grating tape and a plurality of magnets, the grating tape is used to cooperate with an induction head for incremental displacement measurement, and each of the magnets is distributed along the length direction of the grating tape, 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, in each of the magnets, according to the different magnetic field directions, each magnet is assigned a serial number; the magnets are grouped into several magnet groups, and each magnet group includes at least two magnets, and the serial numbers of the magnets in each magnet group form a coded value, which is used as the identification code of the magnet group. By adopting the above arrangement method, on the basis of satisfying the arrangement of sufficient magnet groups, it also ensures that the difference in the magnetic field directions between adjacent magnets is 20°, so that the magnetic field direction sensor can more easily and accurately identify the position.

[0010] Preferably, there are two or three magnets in each magnet group; and / or, at least two of the magnets in each magnet group have different corresponding serial numbers.

[0011] The present invention also provides an absolute displacement sensor, including an induction head and the above-mentioned composite grating scale. After the composite grating scale and the induction head are installed on the device to be measured, the induction head can move relative to the length direction of the composite grating scale; the induction head is integrated with a grating tape sensor and at least one magnetic field sensing module. During the process of the induction head moving along the length direction of the composite grating scale, the grating tape sensor can cooperate with the grating tape to perform incremental displacement measurement, and the magnetic field sensing module can cooperate with the magnets to obtain the absolute position of the induction head.

[0012] With the above-mentioned sensor, the grating strip and the magnet are integrated through the composite grating scale. When measuring displacement, the grating strip cooperates with the grating strip sensor in the sensing head to enable 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 and achieve absolute displacement measurement of displacement sensing.

[0013] Preferably, there are two magnetic field sensing modules in the sensing head, and there are two magnets in the magnetic group. The distance between the two magnetic field sensing modules is less than or equal to the grating pitch of the grating strip. With such a design, the direction values of the magnetic fields of the two magnets can be read simultaneously, so as to quickly determine the segmented coding value.

[0014] Preferably, the sensing head is provided with four magnetic field sensing modules, and the distance between two adjacent magnetic field sensing modules is less than or equal to half of the grating pitch of the grating strip. With such a design, it can be ensured that at least two magnetic field sensors are within the effective magnetic field range of the magnet to achieve real-time segmented position judgment. At this time, the positioning data of the incremental grating strip is used to assist in judging which two magnetic field sensors are aligned with the magnet.

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

[0016] Preferably, the grating strip is arranged with metal segments and grids alternately distributed in the length direction. The grating strip sensor has at least two induction coils. When current is applied to the induction coils, mutual inductance electromotive forces can be generated between the induction coils.

[0017] Preferably, a shielding cover is provided outside the magnet, and the side of the shielding cover facing the magnetic field sensing module is an open structure. With such a design, the magnetic field interference between the magnets and the external magnetic field interference can be reduced. A magnetic field shielding cover is installed on the magnet, and the shielding cover is opened in the direction facing the magnetic direction detection chip, and the rest of the directions are shielded and restricted.

[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 grating strip includes a PCB board, and the metal segments are formed by printing metal foils on the PCB board; or, the grating strip is a metal strip, and the grids are through holes or grooves provided on the metal strip.

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

[0021] Preferably, the composite grating scale further includes a base with a long strip structure. The upper side of the base has a strip-shaped groove, and each of the magnets is distributed on the bottom of the strip-shaped groove. A cushion layer is installed in the strip-shaped groove, and the grating tape is located above the cushion layer.

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

[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 angles of the magnetic field directions of the magnets change regularly in a monotonically increasing or decreasing manner.

[0025] Preferably, it further includes a magnetic strip with a long strip structure, and each of the magnets is formed after being locally magnetized or intermittently magnetized by the magnetic strip.

[0026] Preferably, the magnets are arranged on the back side of the grating tape, and a magnetic conduction sheet is provided between the magnets and the grating tape.

[0027] Preferably, the magnets are arranged on both sides or the upper side of the grating tape.

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

[0029] 1. By using the composite grating scale provided by the present invention, through the integration of the grating tape and the magnets, when measuring displacement, the grating tape cooperates with the sensing device in the sensing head, and incremental displacement measurement can be achieved. On this basis, the magnets cooperate with the magnetic field sensing module in the sensing head, and the absolute position where the sensing head is located can be identified, realizing absolute displacement measurement of displacement sensing.

[0030] 2. By using the composite grating scale provided by the present invention, by arranging the magnets directly behind the metal part of the grating tape, not only is the magnetic induction intensity of the magnetic field sensing module not affected, but also the mutual inductance electromotive force between the induction coils is not affected, thereby helping to improve the measurement accuracy and reliability of the displacement sensor.

[0031] 3. By using the composite grating scale provided by the present invention, it can be directly magnetically attracted to the device by means of the suction force of the magnets during use, and the usability is good.

[0032] 4. Displacement measurement is carried out based on the variation law between the grating scale and the mutual inductance electromotive force of the coil, providing a new type of displacement sensing measurement method with extremely excellent measurement accuracy. The resolution of the inductive grating scale can reach up to 20 nm at most, which is a very important factor for some applications of high-quality motion control, such as the micro-motion platform. The output noise of the inductive sensor is low, and at the same time, the output signal quality is good, and its overall signal-to-noise ratio is extremely excellent. On this basis, since there are magnets distributed in the composite grating scale, during the movement of the sensing head, through the cooperative action of the magnetic field sensing module and the magnet, it is possible to identify which magnet the magnetic field sensing module is located in, thereby calculating the absolute position where the sensing head is located and realizing the absolute displacement measurement of displacement sensing.

[0033] 5. In the existing technical solution, the magnetic direction detection chip needs to always face the center of the magnet to detect the rotation direction of the magnet. Based on this application, the magnetic direction detection chip can move away from the magnet. With the cooperative action of another incremental sensing system, as long as the detection chip is within the effective range near the center area of the magnet, the correct magnetic angle value of the magnet can be measured. In addition, this range can also be determined by the change in the magnetic field intensity of the magnet itself.

[0034] 6. In the existing technical solution, the magnetic direction detection chip faces the magnet for angle measurement. Based on this application, when the magnetic direction detection chip faces the magnet, the angle of the magnet can be measured, and then the encoding of this section can be determined. When leaving the magnet range, due to the weakening of the magnetic field and adjacent intersections, the measured direction value is not credible and will not be used for calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic structural diagram of the composite grating scale A.

[0036] Figure 2 It is an exploded schematic diagram of the composite grating scale A.

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

[0038] Figure 4 It is a schematic layout diagram of the magnet 2 relative to the induction grating period of the grating strip 1.

[0039] Figure 5 It is a schematic layout diagram of the magnetic field orientation of the magnet 2 showing an increasing change.

[0040] Figure 6 It is a schematic sorting diagram of the magnet 2 in 18 orientations.

[0041] Figure 7 It is a schematic diagram of the sensing head B.

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

[0043] Figure 9 It is a schematic diagram of the positional relationship between the magnet 2 and the magnetic field sensing module 3, and between the grating strip 1 and the grating strip sensor m. Specific embodiments

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

[0045] Embodiment 1

[0046] As Figure 3 shown, a displacement sensor mainly involves two parts, an induction head B and a composite grating ruler A. After the composite grating ruler A and the induction head B are installed in the device to be measured, the induction head B is arranged on one side of the composite grating ruler A and can move relative to the length direction of the composite grating ruler A. Combining the attached 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, and metal segments 1b and gratings 1a are alternately arranged in sequence in its length direction. Each magnet 2 is distributed along the length direction of the grating strip 1, and the distribution direction of the magnet 2 only needs to be parallel to the length direction of the grating strip 1 in space. Combining the attached Figure 7 It can be seen that the magnetic field sensing module 3 and two induction coils a are arranged in the induction head B. In this embodiment, the two induction coils a are respectively a main coil 6 and a secondary coil 7. The secondary coil 7 is a sine coil and is located inside the main coil 6. When an oscillating current is applied to the main coil 6, a mutual inductance electromotive force can be generated between the main coil 6 and the secondary coil 7.

[0047] Based on the above structure, when the displacement sensor is actually applied, the composite grating ruler A is installed in the device to be measured in a fixed manner, and the induction head B is installed in the device to be measured in a sliding manner, and it is necessary to ensure that the induction coil a in the induction head B is facing one side of the grating strip 1. During operation, after passing an oscillating current through the main coil 6, during the reciprocating movement of the induction head B relative to the composite grating ruler A, there is a mutual inductance electromotive force at the position of the grid 1 between the main and secondary coils, and the mutual inductance electromotive force of the remaining parts will be shielded by the metal section 1b. Also, since the secondary coil 7 is a sine coil, during the movement of the induction head B relative to the grid 1a, the mutual inductance electromotive force between the main and secondary coils will also change in a sine law. That is, the mutual inductance electromotive force changes with the displacement of the grid 1a. Therefore, during the movement of the induction head B along the length direction of the grating strip 1, by performing displacement conversion on the change law of the mutual inductance electromotive force, the displacement of the induction head B can be obtained, thereby realizing the displacement measurement of the target product. On this basis, since there are magnets 2 distributed in the composite grating ruler A, during the movement of the induction head B, through the cooperative action of the magnetic field sensing module 3 and the magnet 2, it is possible to identify which magnet 2 the magnetic field sensing module 3 is located in, and thus calculate the absolute position of the induction head B, realizing the absolute displacement measurement of displacement sensing.

[0048] There are the following two ways for the magnetic field sensing module 3 to cooperate with the magnet 2 to identify its position.

[0049] Method 1: Identify through the layout distance relationship. Please refer to the attached Figure 4 As shown, in the grating strip 1, a metal section 1b and an adjacent grid 1a form a sensing grating period. Each magnet 2 is arranged in a different sensing grating period, and the positions of two adjacent magnets 2 in the corresponding sensing grating period are different. Specifically, within a sensing grating period, the period length data s is 0 - 1024, the arrangement distance between the magnet 2 and the grid 1a of the corresponding sensing grating period is n, and the n values between adjacent magnets 2 are different. For example, the n values of two adjacent magnets 2 are 600 and 500 respectively. When the magnetic field sensing module 3 detects the magnetic field center, if the corresponding data is 600, it is determined that the current magnetic field center position is at the sensing grating data 600, and if the corresponding data is 500, it is determined that the current magnetic field center position is at the sensing grating data 500. Thus, by querying the preset data table through the single-chip microcomputer, it is possible to determine which magnet 2 the induction head B is passing by, and complete the absolute displacement calculation. In addition, based on this method, it can also be used to determine the limit points and calibration point calculations of the displacement.

[0050] If there is a magnet 2 in each grating period, the corresponding data is denser. If a magnet 2 is set every few periods, the corresponding displacement data can be obtained only after running a certain distance. Once this data is obtained, the sensor can know the specific absolute position and switch to the absolute value working mode. This function enables the movement to obtain the absolute position without returning to zero. Considering economy, in this embodiment, a magnet 2 is arranged every three grating periods.

[0051] Method 2: Identify by the different angles of the magnetic field of the magnets. Among the magnets 2, at least two magnets 2 have different magnetic field orientations. At this time, the magnetic field sensing module 3 is a magnetic field direction sensor. By identifying the magnetic field direction of the magnet 2, the specific position of the induction head B on the composite grating scale can be judged, and the absolute value data can be calculated. For example, please refer to Figure 5 As shown, the angles of the magnetic field directions of the magnets 2 change in a monotonically increasing or decreasing pattern. Of course, as the simplest replacement form, in the composite grating scale, as long as the magnetic field direction angles of only two magnets 2 are different, the purpose of absolute value measurement can be achieved.

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

[0053] Example 1: There are two magnets 2 in each magnetic group. The directions of the magnets 2 are numbered. The first magnet is numbered 0, and each subsequent magnet is deflected 20 degrees more in turn. The numbers are 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, G in sequence. The 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, any two adjacent numbers are taken to form a magnetic group. With such an arrangement and coding method of the magnets, on the basis of arranging a sufficient number of magnets, the difference in the magnetic field directions between adjacent magnets is guaranteed to be 20°, making it easier for the magnetic field direction sensor to accurately identify the position.

[0054] Example 2: Every two magnets 2 form a group. Each magnet is numbered from 1 to N according to different magnetic field directions, and the number arrangements of the two magnets do not repeat. Between any two groups, the number arrangements of adjacent magnets also do not repeat. For example, if the direction code of the first magnet is 1 and the second is 2, the arrangement value is 12. Without repeating the arrangement value, the second group of magnets is arranged after the first group. The direction code of the first magnet in the second group is 1, and the direction code of the second magnet in the second group is 3, so the arrangement value is 13. Since the first group and the second group are adjacent, the consecutive values are 1, 2, 1, 3. Arbitrarily select two adjacent values, and we get (1, 2), (2, 1), (1, 3), and the arrangements are all non-repeating. Through the magnetic field direction sensor, the specific position can be distinguished. At this time, the incremental grating belt is used to judge the running direction to distinguish data such as (1, 2) and (2, 1) that have different arrangements but the same combination.

[0055] Example 3: Every two magnets 2 form a group. Each magnet 2 is numbered from 1 to N according to different magnetic field directions, and the number combinations of the two magnets 2 do not repeat. Between any two groups, the number combinations of adjacent magnets 2 also do not repeat. For example, if the direction code of the first magnet 2 is 1 and the second is 2, the combined value is [1, 2]. Without repeating the 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, so the combined value is [2, 3]. Since the first group and the second group are adjacent, the consecutive values are 1, 2, 2, 3. Arbitrarily select two adjacent values to get [1, 2][2, 2][2, 3], and the combinations do not repeat. Through the magnetic field direction sensor, the specific position can be distinguished. At this time, the amount of combined data is less than the permutation method of weight 3, but there is no need to use an incremental grating tape to judge the running direction.

[0056] Example 4: Every 3 magnets 2 form a group. The magnets 2 are grouped, with the number of each group N = 3. The first magnet 2 is fixed at a magnetic field angle of 0 degrees as the index flag bit. For the following two magnets 2, they are encoded with M code values in different magnetic field directions (for example, divided by 20 degrees, there are 18 code values, M = 18), but the value of 0 degrees cannot be used because 0 degrees is dedicated to the index flag bit. Therefore, for these two magnets 2 following, (18 - 1) * (18 - 1 - 1) = 272 kinds of encodings can be obtained. Then arrange these 272 kinds of encodings continuously, that is, arrange the numbers 1 - 272, there are 73712 kinds of permutations, and if combined, there are 36856 kinds of combinations.

[0057] Please refer to the attached Figure 6 , taking the width direction q of the composite grating scale as the reference line, the included angle between the magnetic field direction of the magnet 2 and the reference line is equal to 20r°, where r is a natural number less than or equal to 17. Then the magnet 2 can obtain 18 arrangement directions, and the magnets with 18 different magnetic field directions are sequentially numbered as 1, 2, 3... 18. On the basis of ensuring that the magnetic field orientations of adjacent magnets 2 are different, a total of 307 permutations and combinations can be obtained. The magnet serial numbers, identification serial numbers, and corresponding segment codes are shown in the following table. Among them, the identification serial number is composed of the magnet serial numbers corresponding to two adjacent magnets arranged. If the serial number of the latter magnet is a single digit, a 0 is added before the serial number to make the identification serial number at least three digits.

[0058]

[0059]

[0060] Adopting this magnet arrangement and coding method, similar to Example 1 above, on the basis of arranging a sufficient number of magnets, it also ensures that the difference in the magnetic field orientations between adjacent magnets is 20°, so that the magnetic field direction sensor can more easily and accurately identify the position.

[0061] In this embodiment, the distance between two adjacent magnetic field sensor modules 3 is less than or equal to one-half of the distance between two adjacent magnets 2. In this way, it can be ensured that the magnetic field sensor modules 3 are arranged closely enough so that when the sensing head B stops at any position after power failure, there is a magnetic field sensor module 3 facing one of the magnets 2, ensuring that when the system is restarted, it can complete the judgment of the absolute position in the system without moving the magnetic field sensor module 3. The practical layout of this situation is: each incremental grid band interval period is 10.24 mm, and a magnet is arranged every 10.24 mm. The size of the magnet is 5×4×2, and the magnetized surface of the magnet is located on the two surfaces of 5×2 mm. At this time, the effective magnetic field range is slightly larger than the magnet size, greater than 5.12 mm. The following are two practical layout structures:

[0062] Solution 1: Two magnetic direction detection chips are arranged at the same time, and the interval between the magnetic direction detection chips is 5.12 mm. In this way, at any time, there will always be at least one magnetic direction detection chip passing through the effective magnetic field range of the magnet to measure the encoding value of the segment. In this solution, the magnetic field directions between adjacent magnets are different. If the difference is 20 degrees, it is relatively easy to distinguish. The number of segments that can be distinguished is 360÷20=18, which is a small number of segments.

[0063] Solution 2: Arrange four magnetic direction detection chips at the same time. The interval between magnetic field detection chips is 5.12 mm. In this way, at any time, there will always be at least two magnetic field detection chips aligned with the effective magnetic field range of the magnet. Since the magnets are coded and arranged according to the above rules, the absolute value code at any position can be determined by the angle detection values ​​of the two chips. This code has a larger number and is more practical.

[0064] As for magnet 2, they do not need to be spaced too closely, and multiple incremental cycles can be adjacent in between. In this case, each magnet is used as a position index value. When the magnetic direction detection chip passes through this magnet, the current absolute position is known. Since the incremental sensor is working continuously, it can perform direction judgment and electronic counting. Therefore, based on the index value, the accurate absolute displacement can still be inferred through electronic counting. The disadvantage of this solution is that after power failure, when power is turned on again, 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, and does not require moving to the origin like the traditional solution.

[0065] In this embodiment, the grating strip 1 and the induction coil a together form an incremental encoder, and the magnet 2 and the magnetic field sensing module 3 together form a magnetic absolute encoder. In particular, when there are multiple magnetic field sensing modules 3 within the magnetic field range of the magnet 2, since the induction coil a is a functional coil, through the cooperation of the magnetic field sensing module 3 and the induction coil a, on the basis of ensuring that the magnetic field sensing modules 3 are arranged closely enough, it is also possible to specifically locate and identify which magnetic field sensing module 3 is directly opposite to the magnet 2, thereby significantly improving the accuracy of absolute positioning.

[0066] That is to say, the magnetic angle value measured by the magnetic chip is discontinuous, and it is necessary to combine with the incremental sensing system b to output the final fused signal.

[0067] As Figure 1 shown, the main body of the grating strip 1 is a PCB board, and the metal segments 1b are formed by printing metal foils on the PCB board, and a grid 1a is formed between adjacent two metal segments 1b. In addition, the grating strip 1 can also directly be a metal strip, and the grid 1a is a through hole or a groove provided on the metal strip.

[0068] Again, as Figure 2 shown, the composite grating ruler A further includes a base 4 with a long strip structure. The upper side of the base 4 has a strip-shaped groove 4a, and each of the magnets 2 is distributed on the bottom of the strip-shaped groove 4a. A cushion layer 5 is installed in the strip-shaped groove 4a, and the grating strip 1 is located above the cushion layer 5. Designed in this way, a compact grating ruler product can be provided, and it can be directly magnetically adsorbed and installed on the device by means of the suction force of the magnet, which is convenient to use.

[0069] In this embodiment, the magnet 2 is arranged on the back side of the grating strip 1 and directly opposite to the metal segment 1b. Considering this way, the magnet 2 is covered behind the metal part of the grating strip, which neither affects the magnetic induction of the magnetic field sensing module 3 nor affects the mutual inductance electromotive force between the induction coils a, helping to ensure the measurement accuracy and reliability of the displacement sensor.

[0070] Furthermore, a magnetic conduction sheet is provided between the magnet 2 and the grating strip 1, which plays a role in weakening the magnetic field, is suitable for situations where magnetic shielding is required, and can reduce the signal influence caused by the magnetic field cutting the inductor coil during high-speed operation.

[0071] Each of the magnets 2 can be an independent magnetic block. Or it can be a long strip-shaped magnetic strip, and after local magnetization or spaced magnetization of the magnetic strip, each of the magnets 2 is formed, and the same technical effect can also be achieved.

[0072] In the appendix Figure 7 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 method, the use of diagonal arrangement, side-by-side arrangement and other methods all fall within the protection scope of this application.

[0073] In an absolute displacement sensor, the magnetization direction of the magnet 2 is parallel to the detection moving 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 moving direction axis s. For details, please refer to the appendix Figure 9 As shown, the grid belt 1 extends along the direction axis s, and the magnets 2 are distributed under the grid belt 1 according to a certain angular pattern. During displacement detection, the magnetic field sensing module 3 and the grid belt sensor m move along the direction axis s. The magnetization direction of the magnet 2 and the magnetic field detection chip in the magnetic field sensing module 3 are in a parallel relationship, and the grid belt 1 and the grid belt sensor m are in a parallel relationship. It should be emphasized that according to different installation requirements, the absolute detection component composed of the magnet 2 and the magnetic field sensing module 3 and the incremental detection component composed of the grid belt 1 and the grid belt sensor m can be arranged separately instead of being integrated together. They only need to be fixed together by a connecting piece to maintain synchronous movement. It can also be understood that the magnetic field sensing module 3 and the grid belt sensor m can be discrete PCBs and circuits, which are only fixedly connected together to move in the same direction synchronously.

[0074] Embodiment 2

[0075] As Figure 8 shown, an absolute reflection grating measurement system includes an induction head B and a composite grating ruler A. After the composite grating ruler A and the induction head B are installed on the device to be measured, the induction head B can move relative to the length direction of the composite grating ruler A. Grids 8 are distributed on the grid belt 1, and magnets 2 are distributed along the length direction of the grid belt 1. The induction head B is integrated with a magnetic field sensing module 3 and a grating image sensor 9. The relative movement between the grating image sensor 9 and the grids 8 can realize displacement measurement. The specific measurement principle is a mature existing technology and will not be elaborated here. On this basis, during the movement of the induction head B along the length direction of the composite grating ruler A, the magnet 2 cooperates with the magnetic field sensing module 3 in the induction head to identify the absolute position where the induction head is located, realizing the absolute displacement measurement of the reflection grating measurement system.

[0076] Finally, it should be noted that the above description is only the preferred embodiment of the present invention. Under the inspiration of the present invention, those of ordinary skill in the art can make various similar representations without departing from the purpose and claims of the present invention. Such transformations all fall within the protection scope of the present invention.

Claims

1. A composite scale (A), characterized in that: The invention comprises a grid strip (1) and a plurality of magnets (2), wherein the grid strip (1) is used to cooperate with a sensing head to perform incremental displacement measurement, and each of the magnets (2) is distributed along the length direction of the grid strip (1), wherein at least two of the magnets (2) have magnetic field directions and angles that are different, and the magnets (2) are used to cooperate with a magnetic field sensing module to perform absolute position calculation.

2. The composite scale according to claim 1, characterized in that: In each of the magnets (2), each magnet (2) is assigned a serial number according to the different directions of the magnetic field; The magnets (2) are grouped into a plurality of magnet groups, each of which comprises at least two magnets (2). The serial numbers of the individual magnets (2) in the magnet group form a coding value, which is used as an identification code of the magnet group.

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

4. An absolute displacement sensor, characterized in that: A device comprising a sensing head (B) and a composite scale (A) according to any one of claims 1 to 3, wherein after the composite scale (A) and the sensing head (B) are mounted on the device to be tested, the sensing head (B) can move relative to the length direction of the composite scale (A); The sensing head (B) is integrated with a belt sensor and at least one magnetic field sensing module (3); when the sensing head (B) moves along the length direction of the composite scale (A), the belt sensor cooperates with the belt (1) to perform incremental displacement measurement, and the magnetic field sensing module (3) cooperates with the magnet (2) to obtain the absolute position of the sensing head (B).

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

6. The absolute displacement sensor according to claim 5, characterized in that: The induction 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 one half of the grid pitch of the grid band (1).

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

8. The absolute displacement sensor according to claim 4, characterized in that: The grid strip (1) is provided with metal segments (1b) and grids (1a) arranged in an array in the length direction thereof, and the grid strip sensor has at least two induction coils (a). When current is passed through the induction coils (a), mutual induction electromotive force can be generated between the induction coils (a).

9. The absolute displacement sensor according to claim 8, characterized in that: The magnet is located on the back side of the metal part of the grid strip (1).

10. The absolute displacement sensor according to claim 4, characterized in that: The grating strip (1) is a reflective grating, and the grating strip sensor is a photoelectric switch or a grating image sensor facing the grating grid.

11. The absolute displacement sensor according to claim 4, characterized in that: A shielding cover is arranged outside the magnet, and a side of the shielding cover facing the magnetic field sensor module is an open structure.

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