CN120212844A - A composite scale and absolute displacement sensor - Google Patents
A composite scale and absolute displacement sensor Download PDFInfo
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- CN120212844A CN120212844A CN202510504308.8A CN202510504308A CN120212844A CN 120212844 A CN120212844 A CN 120212844A CN 202510504308 A CN202510504308 A CN 202510504308A CN 120212844 A CN120212844 A CN 120212844A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
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Abstract
The invention discloses a composite grating ruler and an absolute value displacement sensor, which comprise a sensing head and a composite grating ruler, wherein the sensing head can move relative to the length direction of the composite grating ruler after being mounted on equipment to be tested, the composite grating ruler comprises a grating belt and a plurality of magnets, the magnets are distributed along the length direction of the grating belt, the magnetic field directions of at least two magnets are different in angle, the sensing head is integrated with the grating belt sensor and at least one magnetic field sensing module, and in the process of moving the sensing head along the length direction of the composite grating ruler, the grating belt sensor is matched with the grating belt to perform incremental displacement measurement, and the magnetic field sensing module is matched with the magnets to acquire the absolute position of the sensing head. The magnetic field sensor has the beneficial effects that the grating belt is matched with the induction coil in the induction head, so that displacement measurement can be realized, and the magnet is matched with the magnetic field sensing module in the induction head, so that absolute value displacement measurement of displacement sensing can be realized.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a composite grid ruler.
Background
The displacement sensor is a component for measuring and recording the moving distance of a moving part, and the working principle is mainly based on the conversion of mechanical displacement into an electric signal or other forms of information output so as to meet the requirements of information transmission, processing, storage, display, recording, control and the like.
Based on the difference of measurement principles, the current displacement sensor mainly comprises a resistance type displacement sensor, an inductance type displacement sensor, a capacitance type displacement sensor, a photoelectric type displacement sensor, an ultrasonic displacement sensor and the like. With the continuous development of industrial automation, the accuracy and precision of the displacement sensor measurement in different fields also put more stringent requirements. The sensors based on the existing measurement principle almost approach the development limit, and obvious technical breakthroughs are difficult to obtain in the aspects of accuracy and measurement precision.
Therefore, the applicant opens up another technical route and develops a novel displacement sensor for detecting based on the principle of multi-coil mutual inductance electromotive force change. The physical principle of the sensor is that a main coil and a secondary coil are arranged in an induction head, and when an oscillating current is applied, mutual inductance electromotive force is generated between the main coil and the secondary coil. When a metallic target element approaches, the electromagnetic fields of the two coils are disturbed, and the mutual inductance electromotive force changes, and the change is mainly related to the projection coverage area of the main coil and the secondary coil relative to the target element. Based on the principle, if the secondary coil is printed into a functional coil, the target element adopts a long bar-shaped grating ruler, and the grating ruler is provided with gratings in an array mode, when the main coil and the secondary coil linearly move relative to the long bar-shaped grating ruler, the thickness of the metal material of the grating ruler at the position is reduced by the grating, so that the mutual inductance electromotive force between the induction coils is definitely different when the induction head passes through the grating position and the non-grating position. Therefore, in the process that the induction head moves along the length direction of the grid ruler, the mutual inductance electromotive force between each induction coil can change along with the arrangement rule of the grid, and then displacement measurement can be obtained by carrying out displacement conversion on the mutual inductance electromotive force change rule. Like other grid-type displacement sensors, the grid-type displacement sensor can easily obtain absolute displacement values, such as 0 to 10.24 mm, in a smaller scale range, and then repeatedly accumulate to obtain large-size incremental displacement sensing values. However, in practical applications, the large size often requires an absolute displacement sensor value, and therefore, it is necessary to confirm which section of the grid the incremental displacement sensor is located in, so as to obtain the absolute displacement sensor value.
In practical industrial application, the absolute value displacement sensor is a sensor capable of directly measuring the linear displacement of an object and outputting a unique digital code signal corresponding to the displacement, and has a large number of use scenes. In the traditional products such as reflective gratings, sensing gratings and capacitive sensors, the absolute value is usually measured and calculated by adopting the principles of a coding disc, a Hall effect, a magnetic resistance effect and the like, and the process is relatively complex and cumbersome. Meanwhile, for a sensor for displacement measurement based on multi-coil mutual inductance electromotive force change, a good absolute value measurement scheme is not available for large size. Therefore, it is extremely necessary to newly develop a displacement sensing scheme capable of acquiring absolute value displacement data.
Disclosure of Invention
In view of the above, the present invention provides a composite grating ruler, which aims to realize the absolute value measurement of a displacement sensor.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
The composite grating ruler is characterized by comprising a grating belt and a plurality of magnets, wherein the grating belt is used for carrying out incremental displacement measurement in cooperation with an induction head, the magnets are distributed along the length direction of the grating belt, the magnetic field direction angles of at least two magnets are different, and the magnets are used for carrying out absolute position calculation in cooperation with a magnetic field sensing module.
Preferably, each magnet is assigned a serial number according to the difference of magnetic field directions, the magnets are grouped into a plurality of magnetic groups, each magnetic group at least comprises two magnets, and the serial numbers of the magnets in the magnetic groups form a coding value and serve as identification codes of the magnetic groups. By adopting the arrangement mode, on the basis of meeting the arrangement requirement of enough magnetic groups, the difference of the magnetic field orientations between adjacent magnets is 20 degrees, so that the magnetic field direction sensor can accurately identify the position more easily.
Preferably, two or three magnets are arranged in each magnetic group, and/or at least two magnets in each magnetic group have different corresponding serial numbers.
The invention also provides an absolute value displacement sensor, which comprises a sensing head and the composite grating ruler, wherein the sensing head can move relative to the length direction of the composite grating ruler after being mounted on equipment to be measured, the sensing head is integrated with a grating belt sensor and at least one magnetic field sensing module, the grating belt sensor is matched with the grating belt to perform incremental displacement measurement in the process of moving the sensing head along the length direction of the composite grating ruler, and the magnetic field sensing module is matched with a magnet to acquire the absolute position of the sensing head.
By adopting the sensor, the grid belt and the magnet are integrated through the composite grid ruler, when displacement measurement is carried out, the grid belt is matched with the grid belt sensor in the induction head, so that displacement measurement can be realized, on the basis, the magnet is matched with the magnetic field sensing module in the induction head, the absolute value position of the induction head can be identified, and the absolute value displacement measurement of displacement sensing is realized.
Preferably, two magnetic field sensing modules are arranged in the induction head, two magnets are arranged in the magnetic group, and the distance between the two magnetic field sensing modules is smaller than or equal to the grid distance of the grid belt. So designed, the direction values of the magnetic fields of the two magnets are read at the same time, and thus the segment coding value is rapidly determined.
Preferably, the induction 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 one half of the grid distance of the grid belt. By the design, at least two magnetic field sensors can be guaranteed to be in the effective magnetic field range of the magnet, and real-time segmentation position judgment can be realized. At this time, the positioning data of the incremental grating belt is used to assist in judging which two magnetic field sensors are aligned with the magnet.
Preferably, the induction head is provided with 3, 4, 6 or 8 magnetic field sensing modules.
Preferably, the grid belt length direction array is provided with metal segments and grids which are alternately distributed in sequence, and the grid belt sensor is provided with at least two induction coils, and when current is applied to the induction coils, mutual inductance electromotive force can be generated between the induction coils.
Preferably, a shielding cover is arranged outside the magnet, and one side of the shielding cover facing the magnetic field sensing module is of an open structure. By the design, magnetic field interference between the magnets and external magnetic field interference can be reduced, a magnetic field shielding cover is additionally arranged on the magnets, and the shielding cover is opened in the direction facing the magnetic direction detection chip to shield and restrict other directions.
Preferably, the grating belt is a reflective grating, and the grating belt sensor is a photoelectric switch facing the grating grid or a grating image sensor.
Preferably, the grid belt comprises a PCB board, the metal sections are printed on the PCB board by metal foil, or the grid belt is a metal belt, and the grid is a through hole or a groove arranged on the metal belt.
Preferably, the magnets are arranged on the back side of the grid strap opposite to the metal segments.
Preferably, the composite grating ruler further comprises a base with a long strip-shaped structure, wherein strip-shaped grooves are formed in the upper side of the base, the magnets are distributed on the bottoms of the strip-shaped grooves, cushion layers are arranged in the strip-shaped grooves, and the grating strips are located on the upper sides of the cushion layers.
Preferably, the metal section and the adjacent one of the grids are one sensing grid period, each magnet is respectively arranged in different sensing grid periods, and the positions of the adjacent two magnets in the corresponding sensing grid periods are different.
Preferably, the magnetic field directions of any two adjacent magnets are different.
Preferably, in the arrangement direction of the magnets, the angle of the magnetic field direction of the magnets changes in a monotonically increasing or decreasing rule.
Preferably, the magnetic strip structure further comprises a strip-shaped magnetic strip, and each magnet is formed by local magnetization or interval magnetization of the magnetic strip.
Preferably, the magnet is arranged on the back side of the grid belt, and a magnetic guide piece is arranged between the magnet and the grid belt.
Preferably, the magnets are arranged on both sides or on the upper side of the grid belt.
Compared with the prior art, the invention has the beneficial effects that:
1. By integrating the grating belt and the magnet, the composite grating ruler provided by the invention can realize incremental displacement measurement by matching the grating belt with the sensing device in the sensing head when displacement measurement is carried out, and on the basis, the magnet is matched with the magnetic field sensing module in the sensing head, so that the absolute value position of the sensing head can be identified, and absolute value displacement measurement of displacement sensing is realized.
2. By arranging the magnet right behind the metal part of the grating belt, the composite grating ruler not only ensures that the magnetic induction intensity of the magnetic field sensing module is not influenced, but also can not influence the mutual inductance electromotive force between the induction coils, thereby being beneficial to improving the measurement precision and reliability of the displacement sensor.
3. The composite grating ruler provided by the invention can be directly magnetically attracted on equipment by means of the attraction force of the magnet when in use, and is good in use convenience.
4. The displacement measurement is carried out through the change rule between the grid ruler and the coil mutual inductance motor, a novel displacement sensing measurement mode is provided, and the measurement accuracy is extremely excellent. The resolution of the inductive grating ruler can be up to 20nm, which is a very important factor for some high quality motion control applications, such as micro-motion platforms. The inductive sensor has low output noise and good output signal quality, and the overall signal-to-noise ratio is very excellent. On the basis, as the magnets are distributed in the composite grating ruler, in the moving process of the induction head, the magnet body in which the magnetic field sensing module is positioned can be identified through the cooperation of the magnetic field sensing module and the magnet body, so that the absolute value position of the induction head is calculated, and the absolute value displacement measurement of displacement sensing is realized.
5. In the prior art, the magnetic direction detecting chip is required to be always opposite to the center of the magnet to detect the rotation direction of the magnet. Based on the application, the magnetic direction detection chip can move away from the magnet, and under the cooperation of the other incremental sensing system, the detection chip is in an effective range near the central area of the magnet, and can detect the correct angle value of the magnet. In addition to this, this range can also be aided by the variation of the magnetic field strength of the magnet itself.
6. In the prior art, the magnetic direction detection chip is opposite to the magnet for angle measurement. Based on the application, when the magnetic direction detection chip is opposite to the magnet, the angle of the magnet can be measured, and then the code of the section can be determined. Upon leaving the magnet range, the direction measurement is not trusted and cannot be used for calculation due to field weakening and adjacent crossings.
Drawings
Fig. 1 is a schematic structural view of a composite grating ruler a.
Fig. 2 is an exploded schematic view of the composite grid ruler a.
Fig. 3 is a schematic structural diagram of a sensor for measuring displacement based on a change rule of multi-coil mutual inductance electromotive force.
Fig. 4 is a schematic diagram of the arrangement of the magnet 2 with respect to the grating zone 1 for a grating period.
Fig. 5 is a schematic diagram of the layout of the magnetic field of the magnet 2 with increasing variation in orientation.
Fig. 6 is a schematic diagram of the ordering of the magnets 2 in 18 orientations.
Fig. 7 is a schematic diagram of the induction head B.
Fig. 8 is a schematic diagram of an absolute value reflection type grating measuring system.
Fig. 9 is a schematic diagram of the positional relationship between the magnet 2 and the magnetic field sensing module 3, and between the grating 1 and the grating sensor m.
Detailed Description
The invention is further described below with reference to examples and figures.
Example 1
As shown in fig. 3, a displacement sensor mainly relates to a sensing head B and a composite grating ruler a, wherein after the composite grating ruler a and the sensing head B are installed in a device to be measured, the sensing head B is arranged at one side of the composite grating ruler a and can move relative to the length direction of the composite grating ruler a. As can be seen from fig. 2, the composite grating ruler a comprises a grating belt 1 and a plurality of magnets 2, wherein the grating belt 1 is of a strip-shaped sheet structure, and metal sections 1b and gratings 1a which are alternately distributed in sequence are arranged in an array manner in the length direction of the grating belt 1. The magnets 2 are distributed along the length direction of the grid belt 1, and the distribution direction of the magnets 2 is parallel to the length direction of the grid belt 1 in space. As can be seen from fig. 7, the magnetic field sensing module 3 and two induction coils a are arranged in the induction head B, and in this embodiment, the two induction coils a are a main coil 6 and a secondary coil 7, respectively, and the secondary coil 7 is a sinusoidal coil, which is located in the main coil 6. When an oscillating current is supplied to the main coil 6, a mutual inductance electromotive force can be generated between the main coil 6 and the secondary coil 7.
Based on the above structure, when the displacement sensor is in practical application, the composite grating ruler A is fixedly arranged in the equipment to be measured, the induction head B is slidably arranged in the equipment to be measured, and the induction coil a in the induction head B is required to be ensured to be opposite to one side of the grating belt 1. When the induction head is in operation, after the oscillating current is supplied to the main coil 6, in the reciprocating movement process of the induction head B relative to the composite grid ruler A, the main coil and the secondary coil have mutual inductance electromotive force at the position of the grid 1, the mutual inductance electromotive force of the rest part can be shielded by the metal section 1B, and in the movement process of the induction head B relative to the grid 1a, the mutual inductance electromotive force between the main coil and the secondary coil can also change in a sine rule because the secondary coil 7 is a sine coil. I.e. the mutual inductance electromotive force varies with the displacement of the grid 1 a. Therefore, in the process of moving the induction head B along the length direction of the grid belt 1, the displacement of the induction head B can be obtained by carrying out displacement conversion on the mutual inductance electric change rule, so that the displacement measurement of a target product is realized. On the basis, as the magnets 2 are distributed in the composite grating ruler A, in the moving process of the induction head B, the magnetic field sensing module 3 and the magnets 2 are matched to identify which magnet 2 the magnetic field sensing module 3 is positioned on, so that the absolute value position of the induction head B is calculated, and the absolute value displacement measurement of displacement sensing is realized.
The magnetic field sensing module 3 is matched with the magnet 2 to identify the position of the magnetic field sensing module.
In the first mode, as shown in fig. 4, in the grid belt 1, one metal segment 1b and one adjacent grid 1a are one sensing grid period, each magnet 2 is respectively arranged in different sensing grid periods, and the positions of two adjacent magnets 2 in the corresponding sensing grid periods are different. Specifically, in one sensing grid period, the period length data s is 0-1024, the arrangement distance between the magnet 2 and the corresponding sensing grid period grid 1a is n, n values between the adjacent magnets 2 are different, for example, n values of the adjacent two magnets 2 are 600 and 500 respectively, when the magnetic field sensing module 3 detects the magnetic field center, the corresponding data is 600, the current magnet center position is judged to be at the sensing grid data 600, the corresponding data is 500, the current magnet center position is judged to be at the sensing grid data 500, and therefore, by inquiring a preset data table through the singlechip, it can be determined which magnet 2 the sensing head B is passing through, and absolute value displacement calculation is completed. In addition, based on this method, the method can also be used for determining the limit point of displacement and calculating the calibration point.
If there is a magnet 2 for each grating period, the corresponding data is more dense, and if one magnet 2 is arranged at intervals of a plurality of periods, the corresponding displacement data can be obtained after a certain distance of operation is needed. Once the data is obtained, the sensor can know the specific absolute position and switch to the absolute value working mode. This function allows the absolute position to be obtained without zeroing out the motion. In this embodiment, one magnet 2 is arranged every three grating periods in terms of economy.
The second mode is to identify through the difference of the magnetic field angles of the magnets, and in each magnet 2, the magnetic field directions of at least two magnets 2 are different, at this time, the magnetic field sensing module 3 is a magnetic field direction sensor, and the specific position of the induction head B at the composite grating ruler can be judged through identifying the magnetic field directions of the magnets 2, so that absolute value data is obtained through calculation. For example, referring to fig. 5, the angle of the magnetic field direction of the magnet 2 changes in a monotonically increasing or decreasing manner. Of course, as the simplest alternative, in the composite grating ruler, the absolute value measurement can be achieved only by the fact that the magnetic field direction angles of the two magnets 2 are different.
Based on the second mode, the magnets can be positioned and identified by adopting a block coding mode. The coding arrangement mode is that a serial number is assigned to all the magnets 2 according to the difference of the magnetic field directions of the magnets 2, specifically, each direction angle corresponds to a serial number value. Then the magnets 2 are grouped into a plurality of magnet groups, the magnet groups at least comprise two magnets 2, and the serial numbers of the magnets 2 in the magnet groups form coding values which are used as identification codes of the magnet groups.
For example, 1, two magnets 2 in each magnet group are numbered, the direction of the magnet 2 is numbered 0, then each magnet is sequentially deflected by 20 degrees, the numbers are sequentially 1,2,3,4,5,6,7,8,9, A, B, C, D, E, F and G, the practical codes are arranged to be :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., and then two adjacent numbers are arbitrarily taken from the magnets to form one magnet group. By adopting the magnet arrangement and coding mode, on the basis of meeting the requirement of arranging a sufficient number of magnets, the difference of the magnetic field orientations between adjacent magnets is 20 degrees, so that the magnetic field direction sensor can accurately identify the position more easily.
For example, 2, every two magnets 2 are in a group, each magnet is numbered 1 to N according to the direction of the magnetic field, and the numbered arrangement of the two magnets is not repeated. Between any two groupings, the adjacent magnet numbering arrangements are not repeated. For example, the direction code of the 1 st magnet is 1, the second is 2, the arrangement value is 12, in the case that the arrangement value is not repeated, after the second group of magnets is arranged in the first group, the direction code of the second group of the 1 st magnets is 1, the direction code of the second group of the 2 nd magnets is3, the arrangement value is 13, and since one group and two groups are adjacent, the continuous value is 1,2,1,3, and the adjacent two values are arbitrarily selected, thus obtaining (1, 2) (2, 1) (1, 3), and the arrangement is not repeated. The specific position can be distinguished by the magnetic field direction sensor. At this time, the running direction is judged by the incremental gate belt to distinguish the data of the arrangement of (1, 2) and (2, 1) which are different but the same as a combination.
For example 3, every two magnets 2 are in a group, each magnet 2 is numbered 1 to N according to the magnetic field direction, and the numbered combination of the two magnets 2 is not repeated. Between any two groupings, adjacent magnet 2 numbering combinations are not repeated. For example, the direction code of the 1 st magnet 2 is 1, the second is 2, the combined value is [1,2], in the case that the combined value is not repeated, after the second group of magnets 2 is arranged in the first group, the direction code of the second group of the 1 st magnets 2 is 2, the direction code of the second group of the 2 nd magnets 2 is3, the combined value is [2,3], and since one group and two groups are adjacent, the continuous value is 1,2, 3, two adjacent values are arbitrarily selected, and the combination is not repeated. The specific position can be distinguished by the magnetic field direction sensor. At this time, the combined data amount is smaller than the arrangement of the weights 3, but the running direction is not required to be judged by the incremental gate belt.
For example 4, one set for every 3 magnets 2. The magnets 2 are grouped, each group number n=3, the first magnet 2 is fixed as a magnetic field angle of 0 degrees, as an index marker bit, the last two magnets 2 are coded as M code values (for example, divided by 20 degrees, 18 code values, m=18) with different magnetic field directions, but the value of 0 degrees cannot be used because 0 degrees is the index marker bit exclusive. Thus, the latter two magnets 2 can give (18-1) ×18-1-1) =272 codes. The 272 codes are then arranged consecutively, i.e. the numbers 1-272 are arranged, there are 73712 arrangements, if combined, there are 36856 combinations.
Referring to fig. 6, with the width direction q of the composite grid ruler as a reference line, the included angle of the magnetic field direction of the magnet 2 relative to the reference line is equal to 20r degrees, wherein r is a natural number less than or equal to 17, then 18 arrangement directions of the magnet 2 can be obtained, and the magnets with 18 different magnetic field directions are sequentially numbered 1, 2 and 3. On the basis of ensuring that the magnetic fields of two adjacent magnets 2 are oriented differently, 307 kinds of permutation and combination can be obtained in total. The magnet sequence number, the identification sequence number and the corresponding segment code are shown in the following table. The identification serial number is formed by arranging magnet serial numbers corresponding to two adjacent magnets, and if the magnet serial number is a single digit, 0 is added before the serial number so that the identification serial number is at least three digits.
By adopting the magnet arrangement and coding mode, the difference of the magnetic field orientations between the adjacent magnets is 20 degrees on the basis of meeting the requirement of arranging a sufficient number of magnets, so that the magnetic field direction sensor can more easily and accurately identify the position.
In this embodiment, the distance between two adjacent magnetic field sensing modules 3 is less than or equal to one half of the distance between two adjacent magnets 2, so that it is considered that the magnetic field sensing modules 3 can be guaranteed to be arranged tightly enough, so that when the induction head B is stopped at any position when power failure occurs, the magnetic field sensing modules 3 are opposite to one of the magnets 2, and the absolute value position of the system can be judged on the premise that the magnetic field sensing modules 3 are not moved when the system is restarted. The practical layout is that each incremental grating band interval period is 10.24 mm, every 10.24 mm, one magnet is uniformly distributed, the size of the magnet is 5 multiplied by 4 multiplied by 2, the magnetizing surface of the magnet is positioned on the two surfaces of 5 multiplied by 2mm, and the effective magnetic field range is slightly larger than the size of the magnet and is larger than 5.12 mm. The following list two practical arrangements:
In the first scheme, two magnetic direction detection chips are arranged at the same time, and the interval between the magnetic direction detection chips is 5.12 millimeters. Thus, at any moment, at least one magnetic direction detection chip always passes through the effective magnetic field range of the magnet to measure the code value of the segment. In this scheme, the magnetic field directions of adjacent magnets are different, if the difference is 20 degrees, the resolution is easy, the number of distinguishable segments is 360/20=18, and the number of segments is small.
And in the second scheme, four magnetic direction detection chips are arranged at the same time. The spacing between the magnetic field sensing chips was 5.12 mm. Thus, at any one time, there will always be at least two magnetic field detection chips aligned with the effective magnetic field range of the magnet. The magnets are arranged in a coding way according to the rule, and the absolute value coding of any position can be determined through the angle detection values of the two chips. Such a number of codes is larger and more practical.
As for the magnet 2, it is not necessary to space too closely, and a plurality of incremental cycle periods may be adjacent in between, in which case each magnet is used as a position index value, and when the magnetic direction detection chip passes the magnet, the current absolute position is known, and since the incremental sensor is continuously operating, direction judgment and electronic counting can be performed, and therefore, on the basis of the index value, accurate absolute value displacement can still be inferred by electronic counting. The disadvantage of such a solution is that the magnetic direction detection chip does not have to be aligned with the magnet when re-powered after power-off, and therefore the sensor head needs to be moved a distance to ensure that the absolute displacement index value is obtained. But this only requires a small distance to move, and not to the origin as in conventional solutions.
In this embodiment, the grating strip 1 and the induction coil a form a set of incremental encoders, and the magnet 2 and the magnetic field sensing module 3 form a set of magnetic absolute encoders. In particular, when a plurality of magnetic field sensing modules 3 are positioned in the magnetic field range of the magnet 2, the induction coil a is a functional coil, so that the magnetic field sensing modules 3 and the induction coil a are matched for application, and on the basis of ensuring that the magnetic field sensing modules 3 are arranged tightly enough, the magnetic field sensing modules 3 can be positioned and identified in a specific way, and the accuracy of absolute value positioning is improved obviously.
That is, the magnet angle value measured by the magnet chip is intermittent, and the final fused signal can be output only by combining the incremental sensing system b.
As shown in fig. 1, the main body of the grid belt 1 is a PCB board, the metal sections 1b are printed on the PCB board by metal foil, and a grid 1a is formed between two adjacent metal sections 1 b. In addition, the grid strap 1 may be a metal strap directly, and the grid 1a is a through hole or a groove provided on the metal strap.
As shown in fig. 2, the composite grid ruler a further comprises a base 4 with a long strip-shaped structure, a strip-shaped groove 4a is formed in the upper side of the base 4, the magnets 2 are distributed on the bottom of the strip-shaped groove 4a, a cushion layer 5 is installed in the strip-shaped groove 4a, and the grid belt 1 is located on the upper side of the cushion layer 5. By the design, the grid ruler product with a compact structure can be provided, and the grid ruler product can be directly magnetically installed on equipment by means of the attraction force of the magnet, so that the grid ruler product is convenient to use.
In this embodiment, the magnet 2 is disposed on the back side of the grid belt 1 and opposite to the metal section 1b, so that it is considered that the magnet 2 is covered behind the metal section of the grid belt, which does not affect the magnetic induction of the magnetic field sensing module 3, but also the mutual inductance electromotive force between the induction coils a, and helps to ensure the measurement accuracy and reliability of the displacement sensor.
Further, be equipped with the magnetic guide piece between magnet 2 and the bars area 1, play the effect of weakening magnetic field, be applicable to the circumstances that needs the magnetic shielding to and under high-speed operation, weaken the signal influence that the magnetic field cutting inductance sensor coil caused.
Each magnet 2 may be a separate magnet block. Or a strip-shaped magnetic strip is used for forming each magnet 2 after being magnetized locally or at intervals, and the equivalent technical effect can be achieved.
In fig. 7, the magnetic field sensing module 3 and the induction coil a are arranged in series, and it should be emphasized that, except for the serial arrangement, the magnetic field sensing module and the induction coil a are arranged in an oblique direction, and arranged side by side, which falls into the protection scope of the present application.
In the absolute value displacement sensor, the magnetization direction of the 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. Referring to fig. 9 specifically, the grating belt 1 extends along a direction axis s, the magnets 2 are distributed under the grating belt 1 according to a certain angle rule, the magnetic field sensing module 3 and the grating belt sensor m move along the direction axis s during displacement detection, the magnetizing direction of the magnets 2 and the magnetic field detection chip in the magnetic field sensing module 3 are in parallel relation, and the grating belt 1 and the grating belt sensor m are in parallel relation. It is emphasized in particular that, according to different installation requirements, the absolute value detection assembly formed by the magnet 2 and the magnetic field sensing module 3, and the incremental detection assembly formed by the grating strip 1 and the grating strip sensor m, may not be integrated together, but only need to be fixed together by a connecting piece to keep synchronous movement. It will also be appreciated that the magnetic field sensing module 3 and the grid band sensor m may be separate PCBs and circuits, but are simply affixed together for synchronous movement in the same direction.
Example two
As shown in fig. 8, an absolute value reflection type grating measurement system comprises a sensing head B and a composite grating ruler a, wherein after the composite grating ruler a and the sensing head B are mounted on a device to be measured, the sensing head B can move relative to the length direction of the composite grating ruler a, a grating 8 is distributed on a grating belt 1, a magnet 2 is distributed on the length direction of the grating belt 1, the sensing head B is integrated with a magnetic field sensing module 3 and a grating image sensor 9, displacement measurement can be realized by relatively moving the grating image sensor 9 and the grating 8, and the specific measurement principle is the existing mature technology and is not repeated herein. On the basis, in the process that the induction head B moves along the length direction of the composite grating ruler A, the magnet 2 is matched with the magnetic field sensing module 3 in the induction head, so that the absolute value position of the induction head can be identified, and the absolute value displacement measurement of the reflection type grating measurement system is realized.
Finally, it should be noted that the above description is only a preferred embodiment of the present invention, and that many similar changes can be made by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (11)
1. The composite grating ruler (A) is characterized by comprising a grating belt (1) and a plurality of magnets (2), wherein the grating belt (1) is used for carrying out incremental displacement measurement in cooperation with an induction head, the magnets (2) are distributed along the length direction of the grating belt (1), the magnetic field direction angles of at least two magnets (2) are different, and the magnets (2) are used for carrying out absolute position calculation in cooperation with a magnetic field sensing module.
2. The composite grid ruler according to claim 1, wherein in each magnet (2), each magnet (2) is assigned a serial number according to the difference of the magnetic field direction;
The magnets (2) are arranged into a plurality of magnetic groups in groups, the magnetic groups at least comprise two magnets (2), and the serial numbers of the magnets (2) in the magnetic groups form coding values and are used as identification codes of the magnetic groups.
3. The composite grid ruler according to claim 2, wherein two or three magnets (2) are arranged in the magnetic group;
And/or, at least two magnets (2) in each magnetic group are different in corresponding serial numbers.
4. An absolute displacement sensor, characterized by comprising a sensing head (B) and the composite grating ruler (A) of any one of claims 1 to 3, wherein the sensing head (B) can move relative to the length direction of the composite grating ruler (A) after the composite grating ruler (A) and the sensing head (B) are installed on equipment to be tested;
The sensor is characterized in that the sensor head (B) is integrated with a grating belt sensor and at least one magnetic field sensing module (3), the grating belt sensor is matched with the grating belt (1) to perform incremental displacement measurement in the moving process of the sensor head (B) along the length direction of the composite grating ruler (A), and the magnetic field sensing module (3) is matched with the magnet (2) to obtain the absolute position of the sensor head (B).
5. The absolute value displacement sensor according to claim 4, wherein 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 smaller than or equal to the grid distance of the grid belt (1).
6. The absolute value displacement sensor according to claim 5, wherein 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 distance of the grid belt (1).
7. The absolute value displacement sensor according to claim 4, characterized in that the induction head (B) is provided with 3, 4, 6 or 8 magnetic field sensing modules (3).
8. The absolute value displacement sensor according to claim 4, wherein the grid belt (1) is provided with metal segments (1 b) and grids (1 a) which are alternately distributed in sequence in a length direction array, and the grid belt sensor is provided with at least two induction coils (a), and when current is supplied to the induction coils (a), mutual inductance electromotive force can be generated between the induction coils (a).
9. The absolute value displacement sensor according to claim 8, characterized in that the magnet is located on the backside of the metal part of the grating strip (1).
10. The absolute value displacement sensor according to claim 4, wherein the grating strip (1) is a reflective grating, and the grating strip sensor is a photoelectric switch facing the grating or a grating image sensor.
11. The absolute value displacement sensor of claim 4, wherein a shielding cover is arranged outside the magnet, and one side of the shielding cover facing the magnetic field sensing module is of an open structure.
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CN202510504308.8A CN120212844A (en) | 2025-04-22 | 2025-04-22 | A composite scale and absolute displacement sensor |
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CN202510504308.8A CN120212844A (en) | 2025-04-22 | 2025-04-22 | A composite scale and absolute displacement sensor |
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