Inductance type linear absolute position measuring device

Abstract

The invention discloses an inductance type linear absolute position measuring device, and relates to the field of linear position measurement. The inductance type linear absolute position measuring device comprises a single-code-channel grating ruler and a reading head, and the reading head comprises a substrate, a single-code-channel grating ruler, a single-code-channel grating ruler and a single-code-channel grating ruler, the induction coil is drawn on the substrate, the induction coil comprises an S coil array and an R coil array, each coil array comprises n independent complementary coils, and each independent complementary coil is composed of two reversely wound sub-coils which are connected in series; the excitation coil surrounds the induction coil, and the excitation coil is a multi-turn closed coil which is connected in series; and the hardware processing circuit is arranged on the substrate and comprises an excitation signal driving circuit, a selective switch circuit, a demodulation circuit, an operational amplifier circuit and a programmable logic device. Compared with the prior art, the inductance type linear absolute position measuring device provided by the invention is smaller in size, high in reliability, high in measuring precision and stable and accurate in measurement.

Description

Technical Field

[0001] The invention relates to the field of linear position measurement, and in particular to an inductive linear absolute position measurement device. Background Art

[0002] In the field of sensors, inductive linear absolute position sensors are widely used in various types of equipment that require precise measurement of linear positions. Conventional sensors of this type are mainly composed of a scale and a reader, in which the scale adopts a dual-channel design. Its working mechanism is as follows: the first group of inductive sensing coils on the main control board moves above the first channel, and the induced eddy current signal generates an absolute digital signal; the second group of inductive sensing coils slides above the second channel, inducing an incremental analog signal, and finally the processing chip on the main control board, such as a single-chip microcomputer, performs a comprehensive solution on these two signals to obtain high-resolution absolute position data. However, this dual-channel design has obvious disadvantages. On the one hand, the dual-channel setting increases the overall size of the scale, which is not conducive to the development of equipment towards miniaturization and integration; on the other hand, the complex structure of the two channels reduces the reliability of the product. Although the existing single-channel inductive linear absolute position sensor has simplified its structure to a certain extent, its fault tolerance performance is poor. Since it relies only on a single channel to obtain position information, once the copper foil on the channel is partially damaged or contaminated, or is subject to strong external electromagnetic interference during the measurement process, it is very likely to cause abnormal sensing signals, and thus the position data cannot be accurately obtained, seriously affecting the stability and accuracy of the measurement. In addition, the existing single-channel design lacks an effective response mechanism when dealing with position measurements under complex working conditions, and it is difficult to meet the needs of high-precision and high-reliability measurements. Summary of the invention

[0003] In view of the above problems, the present invention aims to provide an inductive single-track linear absolute position measurement device to reduce the size of the scale, improve product reliability, and at the same time enhance the fault tolerance and measurement accuracy of the measurement device.

[0004] The present invention discloses an inductive linear absolute position measuring device, comprising a single-track scale and a reader, the reader comprising: a substrate; an induction coil drawn on the substrate, the induction coil comprising an S coil array and an R coil array, the coil arrays each comprising n independent complementary coils, each of the independent complementary coils being composed of two reversely wound sub-coils connected in series; an excitation coil surrounding the induction coil, the excitation coil being a multi-turn closed coil connected in series; a hardware processing circuit arranged on the substrate, comprising an excitation signal driving circuit, a selection switch circuit, a demodulation circuit, an operational amplifier circuit and a programmable logic device; the excitation signal driving circuit is used to generate an alternating current; the excitation coil receives the alternating current , generating an alternating magnetic field B1 to act on the single-track scale; the single-track scale generates eddy current under the action of the alternating magnetic field B1, and the eddy current generates an alternating magnetic field B2 to act on the induction coil; the S coil array and the R coil array of the induction coil generate S signals and R signals under the action of the alternating magnetic field B2, and the phase difference between the S signal and the R signal is one quarter of a cycle; the selection switch circuit selects to connect the S signal and the R signal; the demodulation circuit receives the S signal and the R signal to output a modulation signal; the operational amplifier circuit receives the modulation signal to generate a coded waveform signal; the programmable logic device receives the coded waveform signal, generates coding information, and outputs position information.

[0005] Preferably, the single-track scale adopts one of the specially designed code values ​​such as continuous displacement code, binary code, M-sequence code, etc.

[0006] Preferably, the sub-coil is wound in a multi-turn U-shaped or multi-turn sinusoidal half-wave pattern.

[0007] Preferably, the S signal and the R signal both include two complementary signals with a phase difference of 180°.

[0008] Preferably, the excitation signal driving circuit can generate a 2.5 MHz square wave.

[0009] Preferably, the single-track scale adopts a printed circuit board, and the surface of the printed circuit board has block copper foils arranged according to a specific code system.

[0010] Preferably, the excitation coil is connected to a frequency-selective capacitor to form an LC circuit.

[0011] Preferably, the excitation coil comprises 2n multi-turn closed coils connected in series, each of the closed coils surrounds each independent complementary coil.

[0012] Preferably, the programmable logic device is a single chip microcomputer with multi-channel ADC.

[0013] Compared with the prior art, the inductive linear absolute position measuring device provided by the present invention can meet the requirements. Compared with the conventional double-track scale, the scale size is reduced, which is conducive to the miniaturization design of the product. The code value signal can be accurately output through the S coil array and the R coil array with a quarter cycle phase difference of the two output signals. At the same time, the S coil array and the R coil array can be subdivided and modulated within each code value to further output high-resolution information.

[0014] In addition, since n independent complementary coils can independently output analog signals for calculating high-resolution position information, according to the design of specific sequence code values, it can be ensured that two independent coils simultaneously output analog signals for calculating high-resolution position information, so that the above-mentioned redundant analog signals can generate high-resolution position information with mutual error correction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of an inductive linear absolute position measurement device.

[0016] Figure 2 The invention is a circuit principle block diagram of an inductive linear absolute position measuring device.

[0017] Figure 3 The signal diagram of the induction coil of an inductive linear absolute position measuring device is shown in FIG.

[0018] Figure 4 The present invention is a schematic diagram of the encoding waveform of an inductive linear absolute position measurement device.

[0019] Description of reference numerals: Reading head, 11, induction coil, 12, excitation coil, 13, selection switch circuit, 14, demodulation circuit, 15, operational amplifier circuit, 16, single chip microcomputer, 17, excitation signal driving circuit; Scale, 21 copper foil. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0021] An embodiment of the present invention discloses an inductive linear absolute position measuring device comprising a read head 1 and a scale 2. Figure 1 , Figure 2 .

[0022] Sixteen excitation coils 12 are evenly spaced on the substrate of the reader 1 (not shown in the figure). Each excitation coil 12 is a rectangle formed by winding multiple turns and surrounds the induction coil 11. The induction coils 11 are independent of each other, including an S coil array composed of S1 to S8 and an R coil array composed of R1 to R8. Each induction coil 11 includes two multi-turn sine half-waveform wound sub-coils. The two sub-coils are wound in opposite directions and are centrally symmetrical to form complementary coils. The induction coils 11 are arranged horizontally and in parallel, wherein the distance from the center point of the S coil array and the R coil to the center point of the next coil is λ, that is, the distance from the center point of the S1 coil to the center point of the S2 coil is λ, the distance from the center point of the S2 coil to the center point of the S3 coil is λ, and so on. The distance from the center point of the R7 coil to the center point of the R8 coil is λ, but the distance between the S8 coil and the R1 coil is (1+1 / 2)λ.

[0023] The substrate is also provided with a hardware circuit, including a selection switch circuit 13 , a demodulation circuit 14 , an operational amplifier circuit 15 , a single chip microcomputer 16 and an excitation signal driving circuit 17 .

[0024] The scale 2 is a PCB board, on which a block copper foil 21 is etched according to a pre-designed 8-bit displacement continuous code.

[0025] When the inductive linear absolute position measuring device is running, that is, the scale 2 moves in the reading head 1, the copper foil 21 moves above the excitation coil 12, and the excitation signal driving circuit 17 generates an alternating current to drive the excitation coil 12, so that the excitation coil 12 radiates an alternating magnetic field. Since the excitation coil 12 surrounds the induction coil 11, the induction coil 11 is affected by the alternating magnetic field, thereby generating an alternating current inside the induction coil 11; the excitation signal driving circuit is a circuit that can generate a 2.5MHz square wave, and outputs the same frequency sine and cosine in the square wave through the LC circuit composed of the excitation coil 12 and the frequency selection capacitor.

[0026] refer to Figure 3 , Figure 4When the induction coil 11 is affected by the excitation coil 12 and generates an alternating current, since it is composed of complementary coils, when there is no conductor outside, the alternating current of the induction coil 11 is in a hedging balance state, so the alternating current value is 0. When the metal copper foil 21 appears below the induction coil 11, the metal copper foil 21 is affected by the excitation coil 12 and generates an eddy current effect, which breaks the current hedging balance state formed by the complementary effect of the induction coil 11, so that the alternating current inside the induction coil 11 changes with the change of the projection area of ​​the metal copper foil 21 on the induction coil 11. In order to prevent the copper foil 21 and the induction coil 11 from being in a symmetrical state, that is, the areas of the copper foil 21 corresponding to the two sub-coils of the complementary coil are equal, this special state will cause the current inside the entire induction coil 11 to be in a hedging balance state, resulting in a code value jump when the output signal is resolved. Therefore, it is necessary to design an S coil array composed of S1 to S8 and an R coil array composed of R1 to R8. Since the S coil and the R coil are both composed of independent complementary coils, each coil array generates a waveform separately. Each time coils S[1:8] and R[1:8] output a complete single cycle waveform, the corresponding scale 2 travels 2λ in the reading head 1. Since the R coil array lags behind the S coil array by 1 / 2λ, the two coil arrays output two sets of envelope carrier signals with a phase difference of one quarter of a cycle, namely the R signal and the S signal.

[0027] When the inductive linear absolute position measuring device is running, that is, the coded scale 2 moves in the reading head 1, the R signal and the S signal are generated by 8 independent complementary coils respectively. It can be seen on the time axis that the waveforms of 2 different coils are changing during operation. Each selection switch circuit 13 selects to connect an independent complementary coil of the S coil array and the R coil array. The R signal and the S signal generated by the S coil array and the R coil array are amplitude modulated by the demodulation circuit 14, that is, the carrier signal is filtered out, and the outer envelope sine and cosine signals are demodulated and input into the operational amplifier circuit 15 to form an amplitude-amplified sine and cosine signal. The ADC module of the single-chip microcomputer circuit 16 samples the amplitude-amplified sine and cosine signal, and then it is filtered and solved by the algorithm. During the operation of the inductive linear absolute position measuring device on the scale, a complete high-resolution absolute value signal is quickly obtained, and finally the position information is output.

[0028] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. An inductive linear absolute position measuring device, comprising a single-track scale and a read head, characterized in that: The reading head comprises: substrate; An induction coil is drawn on the substrate, the induction coil comprises an S coil array and an R coil array, the coil arrays each comprise n independent complementary coils, and each independent complementary coil is composed of two reversely wound sub-coils connected in series; An excitation coil, surrounding the induction coil, wherein the excitation coil is a multi-turn closed coil connected in series; A hardware processing circuit is arranged on the substrate, comprising an excitation signal driving circuit, a selection switch circuit, a demodulation circuit, an operational amplifier circuit and a programmable logic device; The excitation signal driving circuit is used to generate an alternating current; The excitation coil receives the alternating current to generate an alternating magnetic field B1 acting on the single-track scale; The single-track scale generates eddy current under the action of the alternating magnetic field B1, and the eddy current generates an alternating magnetic field B2 acting on the induction coil; The S coil array and the R coil array of the induction coil generate an S signal and an R signal under the action of the alternating magnetic field B2, and the phase difference between the S signal and the R signal is one quarter of a cycle; The selection switch circuit selects to connect the S signal and the R signal; The demodulation circuit receives the S signal and the R signal and outputs a modulated signal; The operational amplifier circuit receives the modulation signal to generate a coded waveform signal; The programmable logic device receives the coded waveform signal, generates coded information, and outputs position information.

2. The inductive linear absolute position measuring device according to claim 1, characterized in that: Single track scales use one of the specially designed code values ​​such as continuous displacement code, binary code, M-sequence code, etc.

3. The inductive linear absolute position measuring device according to claim 1, characterized in that: The sub-coil is wound in a multi-turn U-shaped or multi-turn sinusoidal half-wave pattern.

4. The inductive linear absolute position measuring device according to claim 1, characterized in that: The S signal and the R signal each include two complementary signals with a phase difference of 180°.

5. The inductive linear absolute position measuring device according to claim 1, characterized in that: The excitation signal driving circuit can generate a 2.5 MHz square wave.

6. The inductive linear absolute position measuring device according to claim 1, characterized in that: The single-track scale adopts a printed circuit board, and the surface of the printed circuit board has block copper foils arranged according to a specific code system.

7. The inductive linear absolute position measuring device according to claim 1, characterized in that: The excitation coil is connected to a frequency-selective capacitor to form an LC circuit.

8. The inductive linear absolute position measuring device according to claim 1, characterized in that: The excitation coil includes 2n multi-turn closed coils connected in series, each of which surrounds each independent complementary coil.

9. The inductive linear absolute position measuring device according to claim 1, characterized in that: The programmable logic device is a single chip microcomputer with multi-channel ADC.

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