CN-121977423-A - Displacement sensor based on electromagnetic induction and displacement measurement method

CN121977423ACN 121977423 ACN121977423 ACN 121977423ACN-121977423-A

Abstract

The invention discloses a displacement sensor and a displacement measurement method based on electromagnetic induction, wherein the sensor comprises a sensing and signal generating unit, a signal conditioning and converting unit and a digital processing and resolving unit, the sensing and signal generating unit comprises a multi-channel analog switch and an LC oscillating circuit, an inductance element in the LC oscillating circuit is composed of displacement sensitive elements, the multi-channel analog switch is used for selectively connecting the displacement sensitive elements into the corresponding LC oscillating circuit, the signal conditioning and converting unit is used for shaping an oscillating signal into a digital pulse signal, and the digital processing and resolving unit can measure the frequency of the digital pulse signal by adopting an equal-precision frequency measurement method and resolve displacement according to the change of a frequency value. The invention realizes stable output amplitude and higher frequency stability in a wide frequency range, ensures the stability of signals, eliminates measurement errors in low frequency by the traditional frequency measurement method and ensures high-precision measurement in a full-range.

Inventors

PENG KAI
CHEN ZIRAN
WANG HEWEN
LIU ZHENGXIAN
CHEN LEI
WANG ZHONGXING

Assignees

重庆理工大学

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (9)

1. The displacement sensor based on electromagnetic induction is characterized by comprising a sensing and signal generating unit, a signal conditioning and converting unit and a digital processing and resolving unit, wherein the sensing and signal generating unit comprises a plurality of analog switches and at least two LC oscillating circuits, inductance elements in each LC oscillating circuit are composed of displacement sensitive elements and are used for converting displacement changes into oscillating signals with frequency changes, input ends of the plurality of analog switches are respectively and electrically connected with a plurality of groups of displacement sensitive elements, output ends of the plurality of analog switches are correspondingly and electrically connected with input ends of the at least two LC oscillating circuits and are used for selectively connecting one or more groups of displacement sensitive elements into the corresponding LC oscillating circuits, input ends of the signal conditioning and converting unit are electrically connected with output ends of the sensing and signal generating unit and are used for shaping the oscillating signals into digital pulse signals, and input ends of the digital processing and resolving unit are electrically connected with output ends of the signal conditioning and converting unit and can measure the frequency of the digital pulse signals by an equal-precision frequency measurement method and resolve the displacement according to the change of frequency values.
2. The displacement sensor based on electromagnetic induction of claim 1, wherein the LC oscillating circuit is a three-point type Western-style LC oscillating circuit, and capacitors are connected in parallel to two ends of the displacement sensitive element in the three-point type Western-style LC oscillating circuit.
3. The displacement sensor based on electromagnetic induction according to claim 2, wherein the displacement sensor in the LC oscillating circuit is further provided with an additional inductance connected in series or in parallel therewith, the additional inductance being used for increasing the Q value of the LC oscillating circuit.
4. The displacement sensor based on electromagnetic induction of claim 1, wherein the displacement sensor is a planar coil manufactured by a PCB process.
5. The displacement sensor based on electromagnetic induction according to claim 1, wherein the digital processing and resolving unit comprises a microcontroller, an equal-precision frequency measuring module is configured in the microcontroller, the equal-precision frequency measuring module comprises counting units corresponding to the number of the LC oscillating circuits, the counting units are used for counting digital pulse signals of the LC oscillating circuits of corresponding paths and high-frequency reference clocks in the microcontroller in synchronous gate time, and the frequency of the signals is calculated according to the counting values.
6. The displacement measurement method based on electromagnetic induction is characterized by comprising the following steps of: (1) Acquiring at least two LC oscillating circuits, wherein an inductance element of each LC oscillating circuit is formed by a displacement sensitive element; (2) Converting the displacement change of the displacement sensitive element into at least two paths of frequency-changing oscillation signals through at least two LC oscillation circuits; (3) Shaping the oscillation signal to obtain a digital pulse signal; (4) Synchronously measuring the frequency of the digital pulse signals by adopting an equal-precision frequency measurement method, so that the measurement starting time and the measurement ending time of each path of digital pulse signals are kept consistent; (5) The displacement is resolved from the measured frequency variation.
7. The method of claim 6, wherein in the step (1), at least two of the LC oscillating circuits are Western three-point LC oscillating circuits, and a capacitor is connected in parallel to both ends of the displacement sensor in each of the Western three-point LC oscillating circuits.
8. The method for measuring displacement based on electromagnetic induction according to claim 6, wherein in the step (4), the constant-precision frequency measurement method comprises generating a synchronous gate signal by a microcontroller, counting a digital pulse signal and a high-frequency reference clock inside the microcontroller simultaneously during gate opening, and calculating a frequency based on the counted value after gate closing.
9. The method of measuring displacement based on electromagnetic induction according to claim 6, wherein in the step (5), the displacement is an angular displacement or a linear displacement.

Description

Displacement sensor based on electromagnetic induction and displacement measurement method Technical Field The invention relates to the technical field of measurement and sensing, in particular to a displacement sensor based on electromagnetic induction and a displacement measurement method. Background An inductive encoder is a displacement sensor based on the principle of electromagnetic induction, which determines the position of a mover by detecting changes in electromagnetic coupling between coils. Conventional inductive encoders mostly employ amplitude detection or phase detection principles, i.e. resolving displacement by measuring amplitude or phase changes of induced electromotive force. The method has the inherent defects that firstly, the method is extremely sensitive to the amplitude stability of an excitation signal, any fluctuation of the excitation signal can directly introduce measurement errors, secondly, the processing process of analog quantity is easy to be subjected to external electromagnetic interference, the signal to noise ratio is reduced, and finally, the circuit complexity is higher, additional demodulation links are needed, and the cost and the power consumption are increased. In order to overcome the above problems, there are also solutions in the prior art that convert the coil inductance variation into a frequency signal. For example, a sensitive coil is connected to an LC oscillating circuit, when the inductance of the coil changes along with the displacement, the oscillating frequency changes correspondingly, and the displacement information can be obtained by measuring the frequency. However, in the prior art, a conventional direct counting method is mostly adopted for measuring the frequency signal, namely, the pulse of the measured signal is counted in a fixed gate time, but the conventional frequency measuring method has inherent + -1 counting error, and particularly, the relative error is larger in low-frequency measurement. Therefore, how to improve the measurement accuracy of the inductive encoder in the whole range, especially the measurement accuracy of the low frequency band, is a technical problem to be solved in the field. Disclosure of Invention The invention aims to solve the technical problem of providing a displacement sensor based on electromagnetic induction, which can maintain measurement accuracy in a full-scale range. In order to solve the technical problems, the invention adopts the following technical scheme: The displacement sensor based on electromagnetic induction comprises a sensing and signal generating unit, a signal conditioning and converting unit and a digital processing and resolving unit, wherein the sensing and signal generating unit comprises a plurality of analog switches and at least two LC oscillating circuits, inductance elements in each LC oscillating circuit are composed of displacement sensitive elements and are used for converting displacement changes into oscillating signals with frequency changes, input ends of the plurality of analog switches are respectively and electrically connected with a plurality of groups of displacement sensitive elements, output ends of the plurality of analog switches are correspondingly and electrically connected with input ends of the at least two LC oscillating circuits and are used for selectively connecting one or more groups of displacement sensitive elements into the corresponding LC oscillating circuits, input ends of the signal conditioning and converting unit are electrically connected with output ends of the sensing and signal generating unit and are used for shaping the oscillating signals into digital pulse signals, and input ends of the digital processing and resolving unit are electrically connected with output ends of the signal conditioning and converting unit and can measure the frequency of the digital pulse signals by an equal-precision frequency measurement method and calculate displacement according to the change of frequency values. The displacement change is converted into the frequency signal, and the frequency signal is measured by adopting the equal-precision frequency measurement method, so that the defect of the traditional frequency measurement method is overcome, meanwhile, the equal-precision frequency measurement method eliminates the inherent + -1 counting error of the traditional direct counting method, and high-precision measurement is realized in the full range (including a low frequency band). And through the cooperative configuration of the multipath analog switch and a plurality of LC oscillating circuits, the flexible switching of a plurality of groups of displacement sensitive elements is realized. As optimization, the LC oscillating circuit is a three-point type western-style LC oscillating circuit, and capacitors are connected in parallel to the two ends of the displacement sensitive element in the three-point type western-style LC oscillating circuit. When t