Absolute position detection system

Abstract

The invention provides an absolute position detection system. The absolute position detection system comprises a magnetic grid, a magnetic field sensing module and a position calculation module, wherein the magnetic grid is formed by alternately arranging N-S magnetic poles; in the arrangement direction of the magnetic poles, the heights of the magnetic poles of the magnetic grids are the same, and the widths form an arithmetic progression. The magnetic field sensing module is composed of four magnetic resistors which are arranged on the plane parallel to the magnetic grid at equal intervals and have the same sensing coefficient and the same sensing direction. And the position calculation module determines the position of the magnetic field sensing module relative to the starting point of the magnetic grid according to the uniqueness of output signals corresponding to different positions of the magnetic field sensing module opposite to the magnetic grid. The absolute position detection system is matched with a corresponding calculation method, absolute position measurement is achieved through a single magnetic track, the size of the absolute position detection system is greatly reduced, and the absolute position detection system can well meet the application requirement of absolute position detection in a narrow space range.

Description

Technical Field

[0001] This application relates to the technical field of position or distance measurement / sensing, and particularly relates to an absolute position detection system based on magnetic field measurement. Background Art

[0002] With the development of modern technology and the improvement of automation level, in the fields of aerospace, mechanical manufacturing, high-precision numerical control machine tools, etc., a large number of displacement sensors that can truly and reliably reflect the position information of the object to be measured are required, and it is required that the displacement sensor system has a small volume, light weight, fast response speed, and is not sensitive to the measurement environment (such as temperature, dust, light, electromagnetic interference, etc.), and can know the position of the target relative to the reference point in a timely manner at any time point during the startup and operation process of the measurement system.

[0003] The position detection system based on magnetic field is not sensitive to factors such as temperature, dust, and light in the measurement environment, and electromagnetic interference can also be cancelled by using redundant magnetoresistance and electrical connection relationships. Among them, the magnetic grating sensor is one of the most commonly used and basic digital displacement sensors. Due to its high anti-vibration and anti-shock performance, it is suitable for application in industrial environments such as water, oil, dust, and high temperature, and has a simple structure, small volume, and high precision, so it has been widely used.

[0004] The magnetic grating sensor is a displacement sensor that measures displacement based on the magnetoresistive effect. It can measure displacement by using the magnetic field interaction between the magnetic grating and the magnetic head. However, due to the periodic arrangement of the magnetic poles of the magnetic grating, the output signal of the magnetic head is also a periodic waveform, which causes the existing magnetic grating sensing system to be unable to determine the absolute position of the current magnetic head facing the magnetic grating at the first time of starting the detection system (with the starting point of the magnetic grating as the reference). In order to measure the absolute position at the first time, it is often necessary to increase the code tracks and use the uniqueness of the magnetic field formed in space between multiple code tracks to measure the absolute position (for example, a multi-code track position measurement system similar to the principle of a vernier caliper). However, doing so will increase the size of the position measurement system, which is unacceptable for application scenarios with strict restrictions on the installation space of the position detection system. Summary of the Invention

[0005] In view of the fact that the existing magnetic grating-based absolute position measurement system requires the combined action of multiple code tracks and magnetic heads, which not only increases the manufacturing difficulty of the magnetic grating but also results in an overly large size of the absolute position measurement system, making it difficult to meet specific application scenarios. Therefore, this application improves the structure of the magnetic grating and adaptively develops a corresponding position calculation method, and proposes an absolute position detection system with a single magnetic pole code track, in which the magnetic grating has a small size and low manufacturing difficulty.

[0006] The absolute position detection system provided by this application includes: a magnetic grating formed by alternately arranging N-S magnetic poles, a magnetic field sensing module (magnetic head), and a position calculation module.

[0007] Among them, the magnetic poles of the magnetic grating have the same height in its arrangement direction, and the widths form an arithmetic sequence. The magnetic field sensing module is composed of four magnetoresistors R1, R2, R3, and R4 that are equally spaced and arranged in parallel to the plane of the magnetic grating and have equal sensing coefficients. The sensing directions of the magnetoresistors R1, R2, R3, and R4 are the same, and are all parallel / antiparallel to the arrangement direction of the magnetic poles of the magnetic grating. The magnetoresistors R1 and R3 form a first sensing half-bridge, and the magnetoresistors R2 and R4 form a second sensing half-bridge; the magnetoresistors R4 and R3 are either the upper half-bridge arms or the lower half-bridge arms of the corresponding sensing half-bridges. The type of the magnetoresistor is XMR, and the XMR includes GMR, TMR, AMR, etc.

[0008] The position calculation module is used to calculate (including matching) the absolute position of the magnetic field sensing module facing the magnetic grating according to the lead-out signals V1 between the magnetoresistors R1 and R3 and the lead-out signal V2 between the magnetoresistors R2 and R4.

[0009] Preferably, the distance L between two adjacent magnetoresistors among the magnetoresistors R1, R2, R3, and R4 is less than the minimum value of the widths of the magnetic poles in the magnetic grating.

[0010] In some embodiments, the position calculation module matches the absolute position of the magnetic field sensing module facing the magnetic grating according to the detected lead-out signals V1 and V2 and the pre-stored relationship curve between the lead-out signals V1 and V2 and the absolute position. The advantage of this part of the embodiments is that the position matching process is simple and the calculation amount is small, but sufficient storage space is required to store the relationship between the lead-out signals V1 and V2 and each absolute position point on the magnetic grating.

[0011] In another part of the embodiments, the position calculation module is based on the detected lead-out signals V1 and V2 and the pre-stored ratio of the distance L between two adjacent magnetoresistors to the width of each magnetic pole on the magnetic grating calculate the absolute position of the magnetic field sensing module facing the magnetic grating; W i is the width of the i-th magnetic pole of the magnetic grating, and i is a positive integer. The calculation of the absolute position of the magnetic field sensing module facing the magnetic grating includes: based on the resistance magnetic angle formula to obtain V1 and V2:

[0012]

[0013]

[0014] Among them, is the ratio of the spacing L to the width W of the magnetic pole of the magnetic grating directly opposite the current magnetic field sensing module; A and B are respectively physical parameters corresponding to the magnetoresistance itself, and θ is the magnetic angle corresponding to the exact position of the magnetoresistance R1 closest to the starting side of the magnetic grating in the magnetoresistance directly opposite it. Construct an intermediate variable V a and V b , and a reference quantity C:

[0015]

[0016] Substitute the pre-stored one by one into the calculation formula of the reference quantity C, and take the corresponding whose value of C is closest to as the current value to further determine the absolute position of the magnetic field sensing module directly opposite the magnetic grating. Through the above steps, at least which magnetic pole or which two magnetic poles of the magnetic field sensing module directly opposite the magnetic grating can be determined.

[0017] Furthermore, in order to determine the exact position of the magnetic field sensing module at the magnetic pole directly opposite it, the following processing can also be performed: Substitute each value of the corresponding whose value of C is closest to into the inverse trigonometric function: respectively to obtain the corresponding values of θ; According to the polarities of the two magnetic poles directly opposite the magnetoresistance in the magnetic field sensing module, determine the final value of θ, and then determine the exact value of the absolute position. When there are two values of the corresponding whose value of C is closest to , and thus there are multiple values of θ obtained, the correct value of θ can be screened according to the polarity of the magnetic pole of the magnetic field sensing module directly opposite the magnetic grating determined in the previous part, and then the absolute position of the magnetic field sensing module with the starting point of the magnetic grating as the reference point can be accurately obtained.

[0018] The absolute position measurement system provided by this application is based on the special setting of the magnetic poles in a single code track, and with the corresponding algorithm, the absolute position detection can be realized. The magnetic grating structure of this absolute position measurement system is simple and small in size, and can well meet the application requirements of small installation space and low manufacturing cost for the absolute position measurement system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of this application, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0020] Figure 1 Structural schematic diagram of the absolute position detection system provided by this application..

[0021] Figure 2a Waveform schematic diagram of the outputs V1 and V2 of two sensing half - bridges in the absolute position detection system provided by this application in some embodiments.

[0022] Figure 2b For Figure 2a Graph of the outputs of two sensing half - bridges corresponding to each absolute position point in the V1, V2 two - dimensional coordinate plane in.

[0023] Figure 3 Is Figure 2b Graph of the conversion of points V1 and V2 on the curve in to V a , V b After conversion to the two - dimensional coordinate plane of V. Detailed implementation manners

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only some of the embodiments of this application, rather than all of them. The components of the embodiments of this application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of this application claimed, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative efforts belong to the scope of protection of this application.

[0026] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0027] In the description of this application, it should be noted that the orientation or positional relationship indicated by terms such as "inside", "outside", "above", "below", "vertical", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this application is usually placed during use. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of this application. In addition, terms such as "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0028] The following will describe in detail some embodiments of the present application in conjunction with the accompanying drawings. Without conflict, the features in the following embodiments can be combined with each other.

[0029] In the embodiment shown as Figure 1 below, the absolute position detection system provided by the present application includes: a magnetic grating 1 formed by alternately arranging N-S magnetic poles, a magnetic field sensing module 2 (magnetic head), and a position calculation module 3 ( Figure 1 not shown in the figure).

[0030] Among them, the magnetic poles (pitch) of the magnetic grating 1 are of the same height in its arrangement direction, and the widths form an arithmetic progression. As Figure 1 shown, the widths of the magnetic poles of the magnetic grating 1 from left to right are 0.3mm, 0.32mm, 0.34mm, 0.36mm..., that is, in this embodiment, the width difference between adjacent two magnetic poles is 0.02mm.

[0031] The magnetic field sensing module 2 (i.e., the magnetic head) is located above the magnetic grating and is separated from the plane of the magnetic grating 1 by a certain air gap. The magnetic field sensing module is composed of four magnetoresistors R1, R2, R3, and R4 that are equally spaced in parallel to the plane of the magnetic grating and have equal sensing coefficients. In Figure 1 the embodiment shown, the interval between adjacent two magnetoresistors among R1, R2, R3, and R4 is 0.25mm. The sensing directions of the magnetoresistors R1, R2, R3, and R4 are the same, and are all parallel / antiparallel to the magnetic pole arrangement direction of the magnetic grating. The magnetoresistors R1 and R3 form a first sensing half-bridge, and the magnetoresistors R2 and R4 form a second sensing half-bridge; the magnetoresistors R4 and R3 are either the upper half-bridge arms or the lower half-bridge arms of the corresponding sensing half-bridges. The types of the magnetoresistors R1, R2, R3, and R4 in the magnetic field sensing module can be XMR, and the XMR includes GMR, TMR, AMR, etc.

[0032] The position calculation module 3 is used to calculate (or match) the absolute position where the magnetic field sensing module is directly opposite to the magnetic grating according to the output signals V1 between the magnetoresistors R1 and R3 and the output signals V2 between the magnetoresistors R2 and R4.

[0033] Preferably, the distance L between adjacent two magnetoresistors among R1, R2, R3, and R4 is less than the minimum value of the widths of the magnetic poles in the magnetic grating.

[0034] Corresponding to Figure 1 the embodiment shown, the waveforms of the output signals V1 between the magnetoresistors R1 and R2 and the output signals V2 between the magnetoresistors R3 and R4 are as Figure 2aAs shown. The induced signals V1 and V2 are respectively "sine waves" with gradually increasing amplitudes, but are mutually offset. Taking the induced signals V1 and V2 as the two-dimensional coordinates of the plane, when the magnetic field sensing module 2 moves relative to the magnetic grating 1, the curve changes presented are as follows Figure 2b shown (where the units of the abscissa and ordinate are both volts (V)). It can be seen that as long as the absolute positions of the magnetic grating 1 corresponding to each coordinate point on the curve and the magnetic field sensing module 2 corresponding to each coordinate point are stored in advance, the absolute position of the current magnetic field sensing module 2 relative to the magnetic grating 1 can be directly matched by the position calculation module according to the measured induced signals V1 and V2. Therefore, in some embodiments, obtaining the absolute position through this matching method has a simple process and a small amount of calculation.

[0035] In other embodiments, an algorithm with a slightly larger amount of calculation can be used. According to the induced signals V1 and V2 and the magnetic angle formula calculate the absolute position of the magnetic field sensing module relative to the magnetic grating. This can avoid the need for a large amount of storage space to pre-store the induced signals V1 and V2 and the absolute position of the current magnetic field sensing module 2 relative to the magnetic grating 1 in the case of a long magnetic grating and many magnetic poles.

[0036] In the other embodiments, the absolute position of the magnetic field sensing module relative to the magnetic grating is calculated (or matched) based on the induced signal V1 between the magnetoresistors R1 and R2 and the induced signal V2 between the magnetoresistors R3 and R4. The specific implementation is as follows:

[0037] The position calculation module, based on the detected induced signals V1 and V2, and the ratio of the pre-stored distance L between two adjacent magnetoresistors to the width of each magnetic pole on the magnetic grating calculates the absolute position of the magnetic field sensing module relative to the magnetic grating. W i is the width of the i-th magnetic pole of the magnetic grating, and i is a positive integer. Based on the resistance magnetic angle obtain V1 and V2:

[0038]

[0039] where is the ratio of the distance L to the width W of the magnetic pole of the magnetic grating where the current magnetic field sensing module is located; A and B are physical parameters corresponding to the magnetoresistor itself, and θ is the magnetic angle corresponding to the precise position of the magnetoresistor R1 closest to the starting side of the magnetic grating in the magnetoresistor it faces.

[0040] Then, using the constructed intermediate variables V a and V b , and the constructed reference quantity C, calculate the absolute position of the magnetic field sensing module relative to the magnetic grating:

[0041]

[0042] For Figure 2b the embodiments belonging thereto, taking the intermediate variables V a and V b as the two coordinate axes of the two-dimensional plane coordinate, then V a and V b when the magnetic field sensing module 2 moves relative to the magnetic grating 1, the curve change presented is as Figure 3 shown (the coordinate unit is volt (V)).

[0043] Then, substitute the pre-stored into the calculation formula in the reference quantity C one by one, and take the corresponding with the value of C closest to as the current value to further determine the absolute position of the magnetic field sensing module facing the magnetic grating. Through the above processing steps, at least which one or two magnetic poles of the magnetic field sensing module facing the magnetic grating can be determined.

[0044] Furthermore, in order to determine the precise position of the magnetic pole that the magnetic field sensing module faces, the following additional calculations can also be performed:

[0045] Substitute each value of the corresponding with the value of C closest to into the inverse trigonometric function: respectively to obtain the corresponding values of θ; according to the polarities of the two magnetic poles that the magnetoresistance in the magnetic field sensing module faces, determine the final value of θ, and further determine the precise value of the absolute position. When there are two values of the corresponding with the value of C closest to and thus there are multiple values of θ obtained, the correct value of θ can be screened according to the polarity of the magnetic pole that the magnetic field sensing module faces the magnetic grating determined in the previous part, and thus the absolute position of the magnetic field sensing module with the starting point of the magnetic grating as the reference point can be accurately obtained.

[0046] As can be seen from the above content, the absolute position measurement system provided by the present application can achieve absolute position detection without using multiple magnetic code tracks based on the special setting of the magnetic poles in the magnetic grating and the corresponding supporting algorithms. The manufacturing process of the magnetic poles of the magnetic grating of the absolute position measurement system is simple, and the overall size of the magnetic grating is small, which can well meet the application requirements of small installation space and low manufacturing cost for the absolute position measurement system.

[0047] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various modifications and changes can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings. Once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

Claims

1. An absolute position detection system, the absolute position detection system comprising: A magnetic grid formed by alternately arranging NS magnetic poles, a magnetic field sensing module and a position calculation module; characterized in that: In the direction of magnetic pole arrangement, the height of the magnetic poles of the magnetic grid is the same, and the width forms an arithmetic progression; the magnetic field sensing module is composed of four magnetic resistors R1, R2, R3, and R4 that are arranged at equal intervals in parallel to the magnetic grid plane and have equal sensing coefficients. The sensing directions of the magnetic resistors R1, R2, R3, and R4 are the same, and are parallel / antiparallel to the arrangement direction of the magnetic poles of the magnetic grid; the magnetic resistors R1 and R3 constitute a first sensing half-bridge, and the magnetic resistors R2 and R4 constitute a second sensing half-bridge; the magnetic resistors R4 and R3 are both upper half-bridge arms of the corresponding sensing half-bridge, or are both lower bridge arms of the corresponding sensing half-bridge; The position calculation module is used to calculate the absolute position of the magnetic field sensing module facing the magnetic grid according to the lead-out signal V1 between the magnetic resistors R1 and R3 and the lead-out signal V2 between the magnetic resistors R2 and R4.

2. The absolute position detection system according to claim 1, characterized in that: The distance L between two adjacent magnetic resistors in the magnetic resistors R1, R2, R3, and R4 is smaller than the minimum value of the magnetic pole width in the magnetic grid.

3. The absolute position detection system according to claim 1 or 2, characterized in that: The position calculation module matches the absolute position of the magnetic field sensing module facing the magnetic grid according to the detected lead-out signals V1, V2 and the correspondence between the pre-stored lead-out signals V1, V2 and the absolute position.

4. The absolute position detection system according to claim 1 or 2, characterized in that: The position calculation module is based on the detected lead-out signals V1 and V2, and the ratio of the distance L between two adjacent magnetic resistors to the width of each magnetic pole on the magnetic grid. Calculating the absolute position of the magnetic field sensing module facing the magnetic grid; i is the width of the i-th magnetic pole of the magnetic grid, where i is a positive integer.

5. The absolute position detection system according to claim 4, characterized in that: The calculating of the absolute position of the magnetic field sensing module facing the magnetic grid includes: a magnetic angle formula based on magnetic resistance Get V1 and V2: in, is the ratio of the spacing L to the width W of the magnetic pole of the magnetic grid that the magnetic field sensing module is currently facing; A and B are respectively the physical parameters corresponding to the magnetic resistance itself, and θ is the magnetic angle corresponding to the precise position of the magnetic resistance R1 closest to the starting side of the magnetic grid in the magnetic resistance it is facing; Constructing the intermediate variable V a 、V b , and the reference quantity C: One by one, save the Substitute the reference quantity C into the calculation formula and make the value of C closest to The corresponding As the current value to further determine the absolute position of the magnetic field sensing module facing the magnetic grid.

6. The absolute position detection system according to claim 1, wherein: The further determining the absolute position of the magnetic field sensing module facing the magnetic grid includes: when the magnetic resistance in the magnetic field sensing module faces two magnetic poles of the magnetic grid, the value of C is closest to The corresponding When there are two values, Substitute the corresponding two values ​​into the inverse trigonometric function: The corresponding values ​​of θ are obtained respectively; the final value of θ is determined according to the polarities of the two magnetic poles facing the magnetic resistance in the magnetic field sensing module, and then the absolute position is accurately determined.

7. The absolute position detection system according to any one of claims 1 to 6, characterized in that: The type of the magnetic resistance is XMR, and the XMR includes GMR, TMR, and AMR.

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