Hall magnetic grid linear displacement sensor and measurement precision improving method thereof

Abstract

The Hall magnetic grid linear displacement sensor comprises a shell, a guide rod, a magnetic grid sliding block and a circuit board, the magnetic grid sliding block is arranged on the shell in a sliding mode, the guide rod is connected with the magnetic grid sliding block, a plurality of N poles and S poles which are distributed at equal intervals are recorded on the magnetic grid sliding block, and the circuit board is fixedly arranged on the shell. A plurality of Hall sensor chips are uniformly arranged on the circuit board at intervals along a first direction; and the guide rod can push the magnetic grid slide block to move above the Hall sensor chips along the first direction. The measurement precision improving method comprises the steps that a guide rod pushes a magnetic grid sliding block to move above a Hall sensor chip in a first direction, so that the Hall sensor chip generates periodic sine wave voltage signals or cosine wave voltage signals; the MCU converts the periodic sine wave voltage signal or cosine wave voltage signal into two orthogonal square wave signals A and B; and the MCU accumulates pulses of the square wave signals A and B to calculate the displacement variation of the magnetic grid sliding block. The detection precision is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of linear displacement sensors, and particularly relates to a Hall magnetic grating linear displacement sensor and a method for improving its measurement accuracy. Background Art

[0002] Linear displacement sensors are divided into two categories: contact type and non-contact type. Currently, the main contact-type products on the market are resistance rulers. The main disadvantages are as follows: contact type is prone to wear, has a short service life, and requires regular maintenance and replacement. It has incremental output. When powered off and restarted, it is necessary to find the zero point and recalibrate. The response speed is slow. There is no digital output, and the output accuracy is low.

[0003] To solve the above disadvantages, the low-cost Hall non-contact technology has become the first choice for replacing resistance rulers. Currently, for the non-contact Hall technology, in order to solve the problem of multi-Hall chip positioning and achieve high-precision measurement methods, it is divided into two categories: active technology and passive technology. The active carbon film resistor technology requires attaching the carbon film resistor to the circuit board, performing equidistant resistor engraving through a laser engraving machine, and connecting it to the circuit board circuit. The equipment investment is relatively large, the production process is complex, and the cost is high. The positioning accuracy needs to be achieved by the active carbon film resistor. No matter how the laser-engraved carbon film resistor is made, it will be restricted by mechanical processing, and there are slightly different resistance values, which affect the actual measurement accuracy and can only achieve relative accuracy.

[0004] However, there is no mature solution for passive technology. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a Hall magnetic grating linear displacement sensor and a method for improving its measurement accuracy to improve the detection accuracy of the linear displacement sensor in view of the deficiencies of the prior art.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A Hall magnetic grating linear displacement sensor includes a housing, a guide rod, a magnetic grating slider, and a circuit board. The magnetic grating slider is slidably arranged on the housing. The guide rod is connected to the magnetic grating slider. A plurality of N poles and S poles are engraved on the magnetic grating slider at equidistant intervals. The circuit board is fixedly arranged on the housing. A plurality of Hall sensor chips are evenly spaced along a first direction on the circuit board. The guide rod can push the magnetic grating slider to move along the first direction above the Hall sensor chips.

[0008] To better implement the present invention, further optimization is made in the above structure. End caps and a tail cap are arranged on both sides of the housing, and a connector is arranged on the end cap.

[0009] To better implement the present invention, further optimization is made in the above structure. A display screen is also arranged on the housing.

[0010] A method for improving the measurement accuracy of a Hall magnetic grating linear displacement sensor, comprising the following steps:

[0011] S1. The guide rod pushes the magnetic grating slider to move above the Hall sensor chip along the first direction, so that the Hall sensor chip generates a periodic sine wave voltage signal or cosine wave voltage signal;

[0012] S2. The MCU converts the periodic sine wave voltage signal or cosine wave voltage signal into two orthogonal square wave signals A and B;

[0013] S3. The MCU calculates the change in the displacement of the magnetic grating slider by accumulating the pulses of the two square wave signals A and B.

[0014] To better implement the present invention, further optimization is made in the above structure. The MCU judges the displacement direction of the magnetic grating slider by distinguishing the change order of the two orthogonal square wave signals A and B.

[0015] To better implement the present invention, further optimization is made in the above structure. All Hall sensor chips are mounted by SMT mounter.

[0016] To better implement the present invention, further optimization is made in the above structure. The MCU uses a laser interferometer or a grating ruler as a reference to calibrate and compensate the distance between all Hall sensor chips, eliminating the error generated by the patch mounting.

[0017] To better implement the present invention, further optimization is made in the above structure. The magnetic grating slider takes the position of the first Hall sensor chip as the initial reference point.

[0018] To better implement the present invention, further optimization is made in the above structure. An independent magnet is also arranged on the magnetic grating slider. When the Hall sensor chip detects the magnetic field change of the independent magnet, the MCU will generate an index signal to locate the position of the magnetic grating slider.

[0019] The present invention has the following beneficial effects compared with the prior art:

[0020] 1. Compared with the prior art, the Hall magnetic grating linear displacement sensor provided by the present invention replaces a single magnet with a magnetic grating slider, which can form a periodic sine wave or cosine wave magnetic field change. At the junction of the two Hall chips, the problem that it is difficult to judge which chip is closer by using the voltage comparison interpolation algorithm with a single magnet is solved, and the detection accuracy of the linear displacement sensor can be further improved.

[0021] 2. The method for improving the measurement accuracy of the Hall magneto-grating linear displacement sensor provided by the present invention utilizes a plurality of N poles and S poles engraved on the magneto-grating slider at equidistant intervals, which cooperate with a plurality of Hall sensor chips arranged at uniform intervals to generate a regularly changing magnetic field, thereby generating corresponding voltage signals. By converting them into square wave signals and calculating the change in the displacement of the magneto-grating slider, the change in displacement can be accurately measured, improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 is a schematic diagram of the external structure of the Hall magneto-grating linear displacement sensor of the present invention;

[0024] Figure 2 is a schematic diagram of the internal structure of the Hall magneto-grating linear displacement sensor of the present invention;

[0025] Figure 3 is a schematic diagram of the cooperation structure between the magneto-grating slider and the Hall sensor chip in the present invention.

[0026] In the figure:

[0027] 1 - housing, 2 - guide rod, 3 - magneto-grating slider, 4 - circuit board, 5 - Hall sensor chip, 6 - end cover, 7 - tail cover, 8 - connector, 9 - display screen. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that unless otherwise specified, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention 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 construed as a limitation on the present invention. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0030] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] Embodiment 1:

[0032] Please refer to Figures 1 - 3 , a Hall magnetic grating linear displacement sensor provided by the present invention includes a housing 1, a guide rod 2, a magnetic grating slider 3, and a circuit board 4. The magnetic grating slider 3 is slidably disposed on the housing 1. The guide rod 2 is connected to the magnetic grating slider 3. A plurality of N poles and S poles are engraved on the magnetic grating slider 3 at equidistant intervals. The circuit board 4 is fixedly disposed on the housing 1. A plurality of Hall sensor chips 5 are evenly spaced along a first direction on the circuit board 4. Since the magnetic grating slider 3 generally can only be a very short section (within 10 cm), the measurement distance cannot exceed the distance of the magnetic grating slider 3 (within 10 cm), which cannot meet the requirements of customers for long-distance detection. By combining a plurality of equidistant Hall sensor chips 5, the measurement distance is extended, and the displacement change amount is accurately measured. Through a high-precision positioning method, long-distance measurement is achieved. The guide rod 2 can push the magnetic grating slider 3 to move along the first direction above the Hall sensor chips 5. End caps 6 and a tail cap 7 are provided on both sides of the housing 1. A connector 8 is provided on the end cap 7. A display screen 9 is also provided on the housing 1.

[0033] Compared with the prior art, by replacing a single magnet or multiple magnets with a magnetic grating slider 3 that burns a periodically changing magnetic signal, the magnetic field signal of the magnetic grating slider can be a sine wave, a cosine wave, a square wave, etc. The Hall sensor chip converts the periodic sine wave or cosine wave magnetic field change into a periodic sine wave or cosine wave voltage signal through the magnetic grating slider. By the method of pulse signal accumulation at the junction of two Hall chips by the MCU, the problem that it is difficult to judge which chip is closer by using a single magnet or multiple magnets through the voltage comparison interpolation algorithm is solved, and the detection accuracy of the linear displacement sensor can be further improved.

[0034] Embodiment 2:

[0035] The present invention also provides a method for improving the measurement accuracy of a Hall magnetic grating linear displacement sensor, including the following steps:

[0036] S1. The guide rod 2 pushes the magnetic grating slider 3 to move in the first direction above the Hall sensor chip 5, so that the Hall sensor chip 5 generates a periodic sine wave voltage signal or cosine wave voltage signal;

[0037] S2. The MCU converts the periodic sine wave voltage signal or cosine wave voltage signal into two orthogonal square wave signals A and B;

[0038] S3. The MCU calculates the change amount of the displacement of the magnetic grating slider 3 by accumulating the pulses of the two square wave signals A and B.

[0039] In this embodiment, the MCU judges the displacement direction of the magnetic grating slider 3 by distinguishing the change order of the two orthogonal square wave signals A and B.

[0040] In order to distinguish the moving direction of the Hall sensor chip 5 on the magnetic grating slider 3, usually two sets of Hall sensor chips 5 with a spacing of (m ± 1 / 4)λ (where m is any positive integer) are adopted, and their output voltages are:

[0041]

[0042] In this embodiment, a sine wave voltage signal is adopted. U1 and U2 are two signals with a 90° phase difference. According to the lead or lag of the output signals of the two Hall sensor chips 5, the moving direction of the magnetic head can be discriminated. By the algorithm of accumulating the pulses of the two signals, the displacement amount can be accurately calculated.

[0043] Where: Uo--induced voltage coefficient;

[0044] λ--magnetization signal pitch of the magnetic grating slider;

[0045] X--displacement amount of the Hall sensor chip on the magnetic grating slider;

[0046] ω--Angular frequency of the exciting current.

[0047] There are two specific implementation methods for high-precision positioning of multi-Hall sensor chips: incremental and absolute.

[0048] Incremental type:

[0049] Before measurement, the magnetic grating slider 3 is moved above the first Hall sensor chip 5 for positioning.

[0050] According to the specific number of Hall sensor chips arranged on the circuit board, the MCU software system will automatically detect the number of Hall sensor chips for setting, and arrange the Hall sensor chips in order from the starting position as No. 0. At this time, the No. 0 Hall sensor chip will be used as the initial reference point.

[0051] After the sensor is powered on, the magnetic grating slider 3 is moved to the position of the No. 0 Hall sensor chip for calibration. Taking the No. 0 Hall sensor chip as the reference, when the magnetic grating slider 3 moves above the Hall sensor chip, a regularly changing magnetic field is generated, and a corresponding voltage signal is generated. These voltage signals are initially sine waves or cosine waves, but after passing through the signal processing circuit, they are converted into square wave signals, forming two orthogonal square wave signals A and B. By distinguishing the change order of signals A and B, the MCU system can judge the displacement direction, and by accumulating the pulses of signals A and B, the displacement of the magnetic grating slider 3 relative to the starting point can be obtained.

[0052] Absolute type:

[0053] An independent magnet is also set on the magnetic grating slider 3. When the Hall sensor chip 5 detects the magnetic field change of the independent magnet, the MCU will generate an index signal to locate the position of the magnetic grating slider 3.

[0054] According to the specific number of Hall sensor chips arranged on the circuit board, the MCU software system will automatically detect the number of Hall sensor chips for setting. There is also a magnetic field configuration of a special independent magnet on the magnetic grating slider 3. When the Hall sensor chip detects this unique magnetic field change, the MCU system will generate an index signal through the voltage change to accurately mark the position of the Hall sensor chips arranged at this time.

[0055] At this time, the magnetic grating slider 3 is between the No. 5 and No. 6 Hall sensor chips. After the sensor is powered on, through the special magnetic field on the magnetic grating slider 3, the voltage changes of the No. 5 and No. 6 Hall sensor chips will be detected, and the position will be quickly locked between the No. 5 and No. 6 Hall sensor chips. Then, using the voltage signals generated by the magnetic fields of multiple groups of equidistant N and S poles as references, rapid positioning is achieved through software algorithms. Therefore, after power-off, the sensor does not need to find the zero point again and can achieve absolute value output.

[0056] All Hall sensor chips 5 in this application are mounted by an SMT mounter. To reduce measurement errors and further improve measurement accuracy, for example, adjacent Hall sensor chips 5 are arranged at a distance of 10 mm. When the circuit board is being mounted, there will be a slight offset between each Hall sensor chip 5 due to the error of the SMT mounter, resulting in the distance between two actually adjacent Hall sensor chips 5 not being exactly 10 mm. Therefore, the MCU uses a laser interferometer or a grating ruler as a reference to calibrate and compensate the distances between all Hall sensor chips 5, and eliminates the SMT mounting error through software algorithm compensation, so as to obtain a high-precision displacement measurement sensor and eliminate the error generated by the mounting.

[0057] This application realizes high-precision linear displacement measurement of multiple Hall chips through the above method.

[0058] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A Hall magnetic grating linear displacement sensor, characterized in that: It includes a housing (1), a guide rod (2), a magnetic grating slider (3) and a circuit board (4). The magnetic grating slider (3) is slidably arranged on the housing (1). The guide rod (2) is connected to the magnetic grating slider (3). A plurality of N poles and S poles are engraved on the magnetic grating slider (3) at equidistant intervals. The circuit board (4) is fixedly arranged on the housing (1). A plurality of Hall sensor chips (5) are evenly arranged at intervals along a first direction on the circuit board (4). The guide rod (2) can push the magnetic grating slider (3) to move along the first direction above the Hall sensor chips (5).

2. The Hall magnetic grating linear displacement sensor according to claim 1, characterized in that: End caps (6) and a tail cap (7) are arranged on both sides of the housing (1). A connector (8) is arranged on the end cap (7).

3. A Hall magnetic grating linear displacement sensor according to claim 1, characterized in that: A display screen (9) is also arranged on the housing (1).

4. A method for improving the measurement accuracy of a Hall magnetic grating linear displacement sensor according to any one of claims 1-3, characterized in that: It includes the following steps: S1. The guide rod (2) pushes the magnetic grating slider (3) to move along the first direction above the Hall sensor chips (5), so that the Hall sensor chips (5) generate periodic sine wave voltage signals or cosine wave voltage signals. S2. The MCU converts the periodic sine wave voltage signal or cosine wave voltage signal into two orthogonal square wave signals A and B. S3. The MCU calculates the change amount of the displacement of the magnetic grating slider (3) by accumulating the pulses of the two square wave signals A and B.

5. The method for improving the measurement accuracy of a Hall magnetic grating linear displacement sensor according to claim 4, wherein: The MCU judges the displacement direction of the magnetic grating slider (3) by distinguishing the change order of the two orthogonal square wave signals A and B.

6. The method for improving the measurement accuracy of a Hall magnetic grating linear displacement sensor according to claim 5, characterized in that: All the Hall sensor chips (5) are mounted by SMT pick-and-place machines.

7. A method for improving the measurement accuracy of a Hall magnetic grating linear displacement sensor according to claim 6, characterized in that: The MCU uses a laser interferometer or a grating ruler as a reference to calibrate and compensate the distances between all the Hall sensor chips (5) to eliminate the errors caused by the pick-and-place mounting.

8. A method for improving the measurement accuracy of a Hall magnetic grating linear displacement sensor according to claim 4, characterized in that: The magnetic grating slider (3) takes the position of the first Hall sensor chip (5) as the initial reference point.

9. A method for improving the measurement accuracy of a Hall magnetic grating linear displacement sensor according to claim 4, characterized in that: An independent magnet is also arranged on the magnetic grating slider (3). When the Hall sensor chip (5) detects the magnetic field change of the independent magnet, the MCU will generate an index signal to locate the position of the magnetic grating slider (3).

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