Eccentric target structure for magnetic suspension bearing and high-precision speed measurement system

Abstract

The application relates to the technical field of magnetic suspension bearing detection, and discloses a high-precision speed measurement system and eccentric target structure for a magnetic suspension bearing, which comprises an eccentric target, a central hole and a target shaft sleeve; the geometric center of the central hole is the rotation center after the central hole is assembled to a rotor shaft; the geometric center of the outer cylindrical surface of the target shaft sleeve and the geometric center of the central hole have a set radial eccentricity; the whole eccentric target is in a continuous and smooth ring shape, and the surface is free of gaps, so that mechanical stress concentration in a high-speed rotating state of the rotor is completely eliminated; when the speed measurement system works, the air gap distance sensed by a sensor probe continuously and periodically changes in a sine mode with the rotation of the rotor shaft. The application effectively avoids magnetic field mutation and high-order harmonic interference caused by a traditional slotted target, completely eliminates signal distortion from the source by combining a rear-end signal processing link, and realizes high-precision rotation speed and phase detection of a magnetic suspension system.

Description

Technical Field

[0001] This invention relates to the field of magnetic levitation bearing testing technology, specifically to an eccentric target structure for magnetic levitation bearings and a high-precision speed measurement system. Background Technology

[0002] During operation, the suspension bearing system requires real-time acquisition of rotor speed and phase signals to achieve spindle levitation and drive control. Existing speed measurement solutions typically use inductive or eddy current sensors in conjunction with a target mounted on the rotor for detection. Traditional targets often employ grooves, teeth, or protrusions machined onto the surface of a metal cylinder. This discontinuous physical structure easily leads to mechanical stress concentration at the edges of the grooves or teeth when the rotor is rotating at high speed, limiting the structural strength and fatigue life of the target and making it difficult to meet the system's requirements for high dynamic balance. Furthermore, when the sensor probe sweeps across the discontinuous edges of the target surface, the abrupt change in the air gap spacing causes a nonlinear change in the magnetic field, resulting in the original analog signal output by the sensor being mixed with more high-order harmonics, distorting the signal waveform.

[0003] In subsequent signal processing, existing speed measurement systems mostly rely on conventional single-threshold comparators to convert analog signals into digital square waves. Due to the prevalence of electromagnetic interference and random vibrations during mechanical operation in industrial environments, the low-frequency detection signals output by sensors are often superimposed with noise. When the noise-laden analog signal fluctuates around the comparison threshold, the single-threshold comparator is prone to frequent state flips, leading to level jitter, miscounting, or pulse loss in the output square wave pulse. The signal source distortion caused by the mechanical structure design, combined with the insufficient anti-interference capability of the processing circuit, can cause errors in the system's output speed and phase feedback signals, thus affecting the synchronization accuracy and overall operational stability of the subsequent magnetic levitation multi-loop control system. Summary of the Invention

[0004] The technical problem solved by this invention is that existing targets for speed measurement of magnetic levitation bearings mostly adopt a structure with grooves or notches on the surface. Under high-speed rotation conditions, such structures are prone to stress concentration, reducing the fatigue life of the structure. Moreover, abrupt changes in geometric characteristics can lead to abrupt changes in magnetic flux and induce high-order harmonic interference. In addition, the signal shaping stage of conventional speed measurement systems mostly uses a single threshold comparison mechanism. Under low-speed conditions, it is prone to pulse loss due to environmental noise and signal waveform distortion. Under high-speed conditions, it is prone to speed sampling errors due to waveform edge blurring. It is difficult to meet the high-precision anti-interference speed measurement requirements of magnetic levitation systems.

[0005] To address the above problems, the present invention provides the following technical solution:

[0006] The first aspect of the present invention provides an eccentric target structure for a magnetic levitation bearing, comprising: an eccentric target, a central hole, and a target bushing.

[0007] The geometric center of the central hole is the rotation center after it is assembled to the rotor shaft, and there is a set radial eccentricity between the geometric center of the outer cylindrical surface of the target bushing and the geometric center of the central hole.

[0008] Furthermore, the eccentric target is in the shape of a continuous and smooth ring, with no grooves, notches, or sharp corners on its surface. The eccentric target is fixed to the shaft end or shoulder of the rotor. The radial wall thickness of the target bushing is set to 3mm to 5mm. The radial eccentricity is set to 0.15mm to 0.3mm.

[0009] Furthermore, the eccentric target is manufactured by laminating silicon steel sheets with high magnetic permeability and low eddy current loss or by integral machining of high magnetic permeability alloy. The outer cylindrical surface of the target bushing is mirror-polished, and the roundness error of the outer circle is less than or equal to 0.005mm. The center hole and the rotor shaft adopt an interference fit with an H7 tolerance grade. The overall mass of the eccentric target is uniformly distributed and there is no stress concentration. The overall dynamic balance grade reaches G1 or above.

[0010] The second aspect of the present invention provides a high-precision speed measurement system, including the eccentric target structure for magnetic levitation bearings as described in the first aspect of the present invention, and further including: an inductive sensor probe, the end face of which is radially aligned with the outer cylindrical surface of the target bushing, for sensing the continuous periodic change of the air gap spacing with the rotation angle of the shaft, and outputting an inductance change signal.

[0011] A signal processing link is electrically connected to the inductive sensor probe. The signal processing link includes a signal conditioning circuit and a waveform shaping circuit connected in sequence. The signal conditioning circuit is used to convert the inductance change signal into a low-frequency analog voltage signal. The waveform shaping circuit has a built-in dual-threshold hysteresis mechanism. The dual-threshold hysteresis mechanism is set with an upper limit trigger voltage and a lower limit reset voltage as the level flip boundary. The difference between the two is the hysteresis voltage, which is used to flip the level state of the low-frequency analog voltage signal and output the final square wave pulse signal.

[0012] Furthermore, it includes multiple inductive sensor probes and multiple signal processing links; the multiple inductive sensor probes are equidistantly arranged along the circumference of the eccentric target to form a redundant detection architecture with primary and backup functions, and each inductive sensor probe is independently connected to a dedicated signal processing link; the circumferential installation angle error between adjacent probes is less than or equal to 0.2°, and the static error of analog signal phase consistency between each independent link due to mechanical installation is less than or equal to 0.5°.

[0013] Furthermore, the signal conditioning circuit includes an excitation signal generation unit that provides high-frequency alternating excitation, and a differential inductor bridge circuit, a low-noise instrumentation amplifier, a second-order active low-pass filter, and a phase-sensitive detector circuit that are connected thereto in sequence.

[0014] Furthermore, the differential inductor bridge circuit is used to convert the acquired inductance change signal into an amplitude-modulated differential voltage signal; the low-noise instrumentation amplifier is used to suppress system common-mode interference, and the gain is set to 20 to 50 times; the cutoff frequency of the second-order active low-pass filter is set to 2.5 kHz; the frequency of the high-frequency sinusoidal excitation current supplied to the probe's internal coil is set to 20 kHz to 25 kHz; the phase-sensitive detection circuit uses a reference signal that is in phase and frequency with the front-end excitation signal for demodulation, and outputs a smooth low-frequency sinusoidal analog voltage signal that retains amplitude and phase information, has a signal-to-noise ratio greater than or equal to 30 dB, and a bandwidth of 0 to 2 kHz.

[0015] Furthermore, the waveform shaping circuit employs a CMOS integrated Schmitt trigger. The internal circuit switching condition of the Schmitt trigger is defined as follows: when the low-frequency analog voltage signal rises over time and crosses the upper limit trigger voltage for the first time, the output square wave pulse signal changes from a low output level to a high output level. Subsequently, even if superimposed noise causes voltage fluctuations in the input signal and crosses the upper limit trigger voltage multiple times, as long as the local trough voltage does not drop to the lower limit reset voltage, the square wave pulse signal maintains the stable state of the high output level, and filters out random interference noise with an amplitude less than or equal to 5% of the effective signal amplitude.

[0016] Furthermore, the internal circuit switching condition of the Schmitt trigger also includes: when the low-frequency analog voltage signal decreases over time and crosses the lower limit reset voltage for the first time, the output square wave pulse signal undergoes a state switching again; during this period, if noise causes the voltage fluctuation of the input signal to cross the lower limit reset voltage multiple times, as long as the local peak voltage does not rise back to the upper limit trigger voltage, the square wave pulse signal will maintain the stable low-level output state; the signal processing link is equipped with a temperature compensation circuit unit, which controls the amplitude fluctuation of the entire link signal to less than or equal to 2% within the operating temperature range of 0 to 80℃ and the ambient humidity range of 5% to 95%.

[0017] Furthermore, the hysteresis voltage is set to 0.3V to 0.5V; the duty cycle of the final output square wave pulse is stabilized at 50%, the rise time and fall time of the square wave pulse are both less than or equal to 1μs, the speed measurement error of the high-precision speed measurement system is kept within ±0.1%, the internal dynamic phase offset error is less than or equal to 0.01°, and the conditioned analog signal adopts differential transmission mode, relying on low impedance shielded cable to achieve distortion-free transmission over a distance of greater than or equal to 60 meters.

[0018] This invention provides an eccentric target structure for magnetic levitation bearings and a high-precision speed measurement system. It offers the following advantages: 1. This invention employs a continuous, smooth, and groove-free annular eccentric target. By setting a radial eccentricity, the air gap spacing changes sinusoidally and periodically. This structure avoids harmonic interference caused by sudden changes in the magnetic field from the source, ensuring the linearity of the induced signal. At the same time, it eliminates structural stress concentration under high-speed rotation, significantly improving the fatigue life and dynamic balance performance of the target under high-speed conditions.

[0019] 2. The signal conditioning circuit of this invention combines a differential inductor bridge, an instrumentation amplifier, and a low-pass filter, effectively suppressing common-mode interference and specifically filtering out high-frequency noise generated by the motor drive. Combined with the same-frequency, same-phase demodulation technology of the phase-sensitive detector circuit, the system can stably extract a high signal-to-noise ratio analog voltage signal in complex oil and electromagnetic interference environments.

[0020] 3. This invention introduces a Schmitt triggering mechanism with hysteresis voltage during the waveform shaping stage. This mechanism effectively filters out small-amplitude random noise and completely eliminates signal level jitter and false flips caused by environmental noise near the zero-crossing point. The final output square wave pulse has steep edges and a stable state, avoiding pulse loss and sampling errors, and fully ensuring the speed measurement accuracy and phase consistency of the subsequent control system. Attached Figure Description

[0021] Figure 1 This is a perspective view of the present invention; Figure 2 This is a waveform timing diagram of the dual threshold hysteresis mechanism of the present invention.

[0022] Among them, 1. Eccentric target; 2. Center hole; 3. Target bushing. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see the appendix Figure 1 The present invention provides an eccentric target structure for a magnetic levitation bearing, comprising an eccentric target 1, a central hole 2, and a target bushing 3; The eccentric target 1 is a continuous and smooth ring shape. The surface of the structure is free of grooves, notches and sharp corners, which eliminates the stress concentration of the structure under high speed rotation and effectively improves the structural strength and fatigue life of the target under high speed conditions.

[0025] The geometric center of the center hole 2 is the rotation center after being assembled to the rotor shaft. The eccentric target 1 is fixed as a whole at the shaft end or shoulder of the rotor, achieving high-precision coaxial assembly with the shaft. The geometric center of the outer cylindrical surface of the target bushing 3 has a set radial eccentricity between it and the geometric center of the center hole 2.

[0026] In terms of specific parameters, the radial wall thickness of the target bushing 3 is set to 3mm to 5mm, and the radial eccentricity is set to 0.15mm to 0.3mm. The wall thickness parameter is used to prevent the eccentric target 1 from becoming magnetically saturated in the working magnetic field environment and to limit the additional rotational inertia it adds to the rotor system; the eccentricity parameter is used to provide the speed measurement system with an inductive air gap change that meets the amplitude requirements, so that the air gap distance between the sensor probe and the outer cylindrical surface of the target bushing 3 changes in a standard sinusoidal periodic manner, avoiding the high-order harmonic interference caused by the sudden change of the magnetic field of the traditional grooved target, and at the same time limiting the centrifugal unbalanced force caused by the eccentric mass under high-speed rotation conditions.

[0027] In terms of material selection and manufacturing, the eccentric target 1 is made of silicon steel sheets with high magnetic permeability and low eddy current loss through lamination or is made of high magnetic permeability alloy as a whole. Utilizing the skin effect and electromagnetic induction principle of inductive sensors, the selected material has stable magnetic permeability, which can ensure that the change in air gap and the change in inductance have a strict linear correspondence, avoid nonlinear distortion of the signal, and improve the linearity of the signal response in the low frequency to 2kHz bandwidth.

[0028] The outer cylindrical surface of the target bushing 3 is mirror-polished to reduce surface eddy current dissipation and magnetic field scattering caused by the skin effect under high-frequency magnetic fields. This reduces interference from the reverse magnetic field of the eddy currents on the target surface to the probe coil, ensuring that the change in magnetic flux of the inductor coil strictly follows the eccentric rotation law, providing a mechanical structural basis for the output of a pure sinusoidal induction signal. The center hole 2 and the rotor shaft adopt an interference fit with an H7 tolerance grade to ensure rotational concentricity. The eccentricity of the eccentric target 1 is controlled within ±0.02mm, and the roundness error of the outer circle of the target bushing 3 is less than or equal to 0.005mm.

[0029] Ultimately, the eccentric target 1 has a uniform mass distribution and no stress concentration, and its overall dynamic balance level reaches G1 or above. Combined with the system limit protection, it meets the requirements for long-term safe operation under maintenance-free and non-replaceable conditions such as nuclear power and heavy-duty industrial environments.

[0030] See appendix Figure 2This embodiment provides a high-precision speed measurement system. The speed measurement system includes the eccentric target 1 as shown in Embodiment 1, and also includes multiple inductive sensor probes and correspondingly configured multiple signal processing links.

[0031] In terms of hardware configuration and installation, multiple inductive sensor probes are equidistantly arranged along the circumference of the eccentric target. The system reserves a positioning reference for the equidistant installation of multiple sensors to ensure the air gap consistency and signal phase synchronization of the multiple probes, forming a redundant detection architecture with primary and backup functions. Each inductive sensor probe is independently connected to a dedicated signal processing link, and the component parameters of each sensor and its corresponding signal conditioning and waveform shaping circuit are completely identical. This achieves dual backup (i.e., signal redundancy and circuit redundancy) for physical detection acquisition, electrical signal conditioning, and Schmitt trigger shaping, meeting the system's redundancy switching and fault tolerance requirements.

[0032] Each probe end face is radially aligned with the outer cylindrical surface of the target bushing 3, maintaining a standard detection gap with the outer cylindrical surface. This strictly controls the uniqueness of the air gap change cycle per revolution, ensuring that the inductive sensor probe outputs a single-cycle standard sinusoidal voltage signal per revolution, with no phase shift or amplitude fluctuation, perfectly matching the measurement input requirements of the downstream differential inductive bridge circuit. The circumferential installation angle error between adjacent probes is less than or equal to 0.2°, and the static error of analog signal phase consistency between independent links due to mechanical installation is less than or equal to 0.5°, meeting the synchronization requirements of subsequent multi-closed-loop control systems.

[0033] In terms of circuit processing, the front end of the signal processing link is a signal conditioning circuit, including an excitation signal generation unit that provides high-frequency alternating excitation, and a differential inductor bridge circuit (i.e., a differential Wheatstone bridge) connected in sequence thereto, a low-noise instrumentation amplifier, a second-order active low-pass filter, and a phase-sensitive detector circuit. The differential inductor bridge circuit is used to convert weak inductance changes into voltage signals; the instrumentation amplifier relies on a differential amplification mechanism to suppress common-mode interference in the system, with a gain set to 20 to 50 times; the cutoff frequency of the second-order active low-pass filter is set to 2.5kHz, specifically filtering out high-frequency noise generated by the motor PWM drive and random interference signals caused by oil and dust in the working environment. Combined with the physical advantage of the large continuous metal sensing surface of the target, the system's resistance to oil, dust, and moisture is greatly enhanced. The conditioned analog signal adopts a differential transmission mode, relying on low-impedance shielded cables to achieve distortion-free transmission over distances of 60 meters or more, adapting to scenarios with strong electromagnetic interference such as nuclear power plants and high-temperature reactor main helium blowers, as well as long wiring scenarios inside equipment compartments, eliminating signal attenuation and phase lag during transmission.

[0034] The back end of the signal processing link includes a waveform shaping circuit electrically connected to the output of the phase-sensitive detector circuit. The waveform shaping circuit uses a CMOS integrated Schmitt trigger (such as CD40106). Unlike ordinary single-threshold comparators, the Schmitt trigger internally sets an upper limit trigger voltage VUT and a lower limit reset voltage VLT, the difference of which is the hysteresis voltage. The hysteresis voltage is set to 0.3V to 0.5V, adapting to the amplitude range of the sinusoidal signal of this invention and compatible with signal shaping requirements under different eccentricity and air gap conditions. The output of the Schmitt trigger directly transmits a digital square wave signal to the subsequent control system. The output square wave level is compatible with the control system's 3.3V or 5V logic level standard, eliminating the need for an additional level conversion circuit.

[0035] In addition, a temperature compensation circuit unit is provided in the signal processing link. This unit combines the temperature characteristics of the selected target material and acts on the differential bridge network or front-end amplifier circuit to counteract the thermal drift of the sensor components. Within the operating temperature range of 0 to 80°C and the ambient humidity range of 5% to 95%, the amplitude fluctuation of the entire link signal is controlled to be less than or equal to 2%, so that the speed measurement accuracy is always maintained within ±0.1%.

[0036] In the overall system workflow, during normal operation, the rotor drives the eccentric target 1 to rotate synchronously. A high-frequency sinusoidal excitation current of 20kHz to 25kHz is passed through the coil inside the probe, generating an alternating magnetic field. According to Faraday's law of electromagnetic induction, the continuous change in the air gap causes a synchronous change in the magnetic flux of the probe coil, which is then converted into periodic fluctuations in inductance. A differential inductor bridge circuit collects the changes in the probe's inductance, converts it into an amplitude-modulated differential voltage signal, amplifies it through an instrumentation amplifier, and filters out noise through a second-order active low-pass filter. The filtered signal is input to a phase-sensitive detector circuit, demodulated using a reference signal that is in phase and frequency with the front-end excitation signal, and outputs a smooth low-frequency sinusoidal analog voltage signal that retains amplitude and phase information, has a signal-to-noise ratio greater than or equal to 30dB, and a bandwidth of 0 to 2kHz.

[0037] Combination Figure 2 As shown, the horizontal axis t represents time, and the vertical axis represents voltage amplitude. The demodulated low-frequency analog voltage signal (input signal vI in the figure) is superimposed with random noise and is input to a Schmitt trigger for waveform shaping. The square wave pulse signal output by the Schmitt trigger (output signal vO in the figure) is shaped at the positive saturation voltage Vsat and the negative saturation voltage... Switching between Vsat and Vsat. When the input signal vI rises with time t and first crosses the upper trigger voltage VUT, the output signal vO switches from a low level. The output signal transitions from Vsat to a high level (Vsat). Afterward, even if superimposed noise causes voltage fluctuations in the input signal, repeatedly crossing the upper trigger voltage, the output signal remains stable at a high level as long as the local trough voltage does not drop to the lower reset voltage (VLT). Similarly, when the input signal decreases over time and first crosses the lower reset voltage (VLT), the output signal flips again. During this period, if noise causes voltage fluctuations in the input signal, repeatedly crossing the lower reset voltage, the output signal remains stable at a low level as long as the local peak voltage does not rise back to the upper trigger voltage (VUT).

[0038] This dual-threshold hysteresis mechanism effectively filters out random interference noise with an amplitude less than or equal to 5% of the effective signal amplitude, eliminating output level jitter, false triggering, and false counting problems caused by noise near the zero-crossing point of the front-end sinusoidal signal. After passing through the positive feedback circuit inside the Schmitt trigger, the gently edged analog voltage signal is converted into a steep square wave pulse with both rise and fall times less than or equal to 1μs, and the duty cycle of the final output square wave pulse is stabilized at 50%.

[0039] The shaped, regularized square wave pulse signal is directly connected to the counter and phase closed-loop module of the magnetic levitation control system. Under the speed measurement bandwidth of 0 to 2 kHz, the speed measurement error of the speed measurement system remains within ±0.1%, and the internal dynamic phase offset error of the multi-channel output square wave signal after circuit processing is less than or equal to 0.01°, effectively ensuring the high-speed steady-state operation of the magnetic levitation system.

Claims

1. An eccentric target structure for a magnetic levitation bearing, characterized in that, include: Eccentric target (1), center hole (2) and target bushing (3); The geometric center of the central hole (2) is the rotation center after it is assembled to the rotor shaft. The geometric center of the outer cylindrical surface of the target bushing (3) and the geometric center of the central hole (2) have a set radial eccentricity.

2. The eccentric target structure for magnetic levitation bearings according to claim 1, characterized in that, The eccentric target (1) is a continuous and smooth ring shape with no grooves, notches and sharp corners on its surface. The eccentric target (1) is fixed to the shaft end or shoulder of the rotor. The radial wall thickness of the target bushing (3) is set to 3mm to 5mm. The radial eccentricity is set to 0.15mm to 0.3mm.

3. The eccentric target structure for magnetic levitation bearings according to claim 1, characterized in that, The eccentric target (1) is made of silicon steel sheets with high magnetic permeability and low eddy current loss, or is integrally machined with high magnetic permeability alloy. The outer cylindrical surface of the target bushing (3) is mirror-polished, and the roundness error of the outer circle is less than or equal to 0.005mm. The center hole (2) and the rotor shaft adopt an interference fit with an H7 tolerance grade. The overall mass of the eccentric target (1) is uniformly distributed and there is no stress concentration. The overall dynamic balance grade reaches G1 or above.

4. A high-precision speed measurement system, characterized in that, The structure includes the eccentric target for magnetic levitation bearing as described in any one of claims 1 to 3, and further includes: an inductive sensor probe with its end face radially facing the outer cylindrical surface of the target bushing (3), used to sense the continuous periodic change in air gap spacing as the shaft rotates, and to output an inductance change signal; and a signal processing link electrically connected to the inductive sensor probe. The signal processing link includes a signal conditioning circuit and a waveform shaping circuit connected in sequence. The signal conditioning circuit is used to convert the inductance change signal into a low-frequency analog voltage signal. The waveform shaping circuit has a built-in dual-threshold hysteresis mechanism. The dual-threshold hysteresis mechanism is set with an upper limit trigger voltage and a lower limit reset voltage as the level flip boundary. The difference between the two is the hysteresis voltage, which is used to flip the level state of the low-frequency analog voltage signal and output the final square wave pulse signal.

5. The high-precision speed measurement system according to claim 4, characterized in that, It includes multiple inductive sensor probes and multiple signal processing links; the multiple inductive sensor probes are arranged at equal intervals along the circumference of the eccentric target (1) to form a redundant detection architecture with primary and backup functions, and each inductive sensor probe is independently connected to a dedicated signal processing link; the circumferential installation angle error between adjacent probes is less than or equal to 0.2°, and the static error of analog signal phase consistency between each independent link due to mechanical installation is less than or equal to 0.5°.

6. The high-precision speed measurement system according to claim 4, characterized in that, The signal conditioning circuit includes an excitation signal generation unit that provides high-frequency alternating excitation, and a differential inductor bridge circuit, a low-noise instrumentation amplifier, a second-order active low-pass filter, and a phase-sensitive detector circuit that are connected in sequence.

7. The high-precision speed measurement system according to claim 6, characterized in that, The differential inductor bridge circuit is used to convert the acquired inductance change signal into an amplitude-modulated differential voltage signal; the low-noise instrumentation amplifier is used to suppress system common-mode interference, and the gain is set to 20 to 50 times; the cutoff frequency of the second-order active low-pass filter is set to 2.5 kHz; the frequency of the high-frequency sinusoidal excitation current passed through the coil inside the probe is set to 20 kHz to 25 kHz; the phase-sensitive detection circuit uses a reference signal that is in phase and frequency with the front-end excitation signal for demodulation, and outputs a smooth low-frequency sinusoidal analog voltage signal that retains amplitude and phase information, has a signal-to-noise ratio greater than or equal to 30 dB, and a bandwidth of 0 to 2 kHz.

8. The high-precision speed measurement system according to claim 4, characterized in that, The waveform shaping circuit uses a CMOS integrated Schmitt trigger. The internal circuit switching condition of the Schmitt trigger is limited as follows: when the low-frequency analog voltage signal rises with time and crosses the upper limit trigger voltage for the first time, the output square wave pulse signal changes from a low level to a high level. Thereafter, even if the superimposed noise causes the input signal to fluctuate and cross the upper limit trigger voltage multiple times, as long as the local trough voltage does not drop to the lower limit reset voltage, the square wave pulse signal will maintain the output high level and remain stable, and will filter random interference noise with an amplitude less than or equal to 5% of the effective signal amplitude.

9. The high-precision speed measurement system according to claim 8, characterized in that, The internal circuit switching condition of the Schmitt trigger also includes: when the low-frequency analog voltage signal decreases over time and crosses the lower limit reset voltage for the first time, the output square wave pulse signal will switch states again; during this period, if noise causes the voltage fluctuation of the input signal to cross the lower limit reset voltage multiple times, as long as the local peak voltage does not rise back to the upper limit trigger voltage, the square wave pulse signal will maintain the stable low-level output state; the signal processing link is equipped with a temperature compensation circuit unit, which controls the amplitude fluctuation of the entire link signal to less than or equal to 2% within the operating temperature range of 0 to 80℃ and the ambient humidity range of 5% to 95%.

10. The high-precision speed measurement system according to claim 8, characterized in that, The hysteresis voltage is set to 0.3V to 0.5V; the duty cycle of the final output square wave pulse is stabilized at 50%, and the rise time and fall time of the square wave pulse are both less than or equal to 1μs. The speed measurement error of the high-precision speed measurement system is kept within ±0.1%, the internal dynamic phase offset error is less than or equal to 0.01°, and the conditioned analog signal adopts differential transmission mode, relying on low impedance shielded cable to achieve distortion-free transmission over a distance of 60 meters or more.

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