A method and apparatus for self-calibration of a magnetostrictive displacement sensor

Abstract

The application relates to the technical field of displacement measurement, and discloses a magnetostrictive displacement sensor self-calibration method and device, which comprises the following steps: acquiring an actual displacement to be measured, judging whether the distance between the displacement and double electromagnetic coils meets a safety avoidance dead zone judgment condition; when the condition is met, pulse current is applied to the first electromagnetic coil and the waveguide wire, and the first absolute propagation time is acquired within a first dynamic time window; after a forced physical delay time, pulse current is synchronously applied to the second electromagnetic coil and the waveguide wire, and the second absolute propagation time is acquired within a second dynamic time window; the flight time difference is obtained by performing difference operation on the two propagation times, and the actual measured wave velocity is calculated in combination with a pre-stored calibration distance; the calibration coefficient is obtained by calculating the ratio of the actual measured wave velocity and a reference wave velocity, the reference wave velocity is corrected by using the calibration coefficient, and the calibration coefficient is overwritten to a memory after meeting a convergence condition. The application avoids the risks of signal overlapping interference and waveform aliasing from the source, and realizes high-precision self-calibration of the sensor under temperature drift.

Description

Technical Field

[0001] This invention relates to the field of displacement measurement technology, specifically to a self-calibration method and apparatus for a magnetostrictive displacement sensor. Background Technology

[0002] A magnetostrictive displacement sensor is an industrial instrument for high-precision displacement measurement based on the time-of-flight method. Its basic working principle utilizes the magnetostrictive effect of the waveguide wire medium. When a transient pulse current emitted by the sensor encounters the local magnetic field of an external position magnet, a torsional stress wave is excited on the waveguide wire. This stress wave propagates along the waveguide wire at a certain speed towards both ends. Upon receiving the stress wave, the detection coil at each end outputs an induced voltage signal. By measuring the time span from the moment the pulse current is emitted to the moment the detection coil captures the induced signal using a high-precision timer, and combining this with the internally stored reference velocity of the stress wave propagation, the actual physical displacement of the position magnet can be calculated.

[0003] However, in practical industrial applications, the propagation speed of stress waves in waveguides is not constant but dynamically drifts with changes in ambient temperature gradients and the release of internal stress due to long-term material service. This wave speed drift directly leads to a non-negligible systematic error in the displacement calculation results. To correct this error, some sensors introduce additional electromagnetic coils for online wave speed calibration. However, existing calibration methods often fail to consider the real-time spatial state of the position vernier during startup. During normal measurement, the native stress wave excited by the position magnet is prone to physically encountering the target stress wave excited by the calibration coil on the waveguide, causing severe waveform interference and time-domain aliasing. Furthermore, existing technologies lack robust asynchronous isolation and forced physical delay mechanisms when continuously exciting multiple calibration signals, leading to internal crosstalk between calibration signals. In addition, facing high-frequency electromagnetic bursts in industrial environments, the underlying wave speed inversion algorithms generally lack fault-tolerant and boundary defense logic for abnormal time differences. When an incorrect timestamp is extracted, it can easily cause microprocessor crashes such as division-by-zero overflow, making it difficult to guarantee the robustness and calibration accuracy of sensors under complex operating conditions over long periods. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a self-calibration method and apparatus for a magnetostrictive displacement sensor, which solves the problem of wave velocity drift in existing magnetostrictive displacement sensors under long-term use and environmental temperature changes.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a self-calibration method for a magnetostrictive displacement sensor, comprising: Obtain the actual displacement to be measured, and determine whether the distance between the actual displacement to be measured and the first electromagnetic coil and the second electromagnetic coil meets the determination condition of the safe avoidance dead zone. When the determination condition is met, an excitation pulse current is applied to the first electromagnetic coil and a pulse current is applied synchronously to the waveguide wire to obtain the first absolute propagation time within the first dynamic time window; After obtaining the first absolute propagation time and after the physical delay time, an excitation pulse current is applied to the second electromagnetic coil and a pulse current is applied synchronously to the waveguide wire to obtain the second absolute propagation time within the second dynamic time window. The flight time difference is obtained by subtracting the first absolute propagation time and the second absolute propagation time. The measured wave velocity is then calculated by combining the pre-stored calibration interval with the flight time difference. The ratio of the measured wave velocity to the preset reference wave velocity is calculated to obtain the calibration compensation coefficient. The preset reference wave velocity is corrected using the calibration compensation coefficient to obtain the new calibrated wave velocity. The new calibrated wave velocity is then written to the memory after it meets the convergence condition.

[0006] Furthermore, determining whether the distance between the actual displacement to be measured and the first and second electromagnetic coils meets the criteria for determining the safe avoidance dead zone specifically includes the following steps: Extract the root mean square value of the position within multiple consecutive normal measurement cycles as the actual displacement to be measured. Calculate the absolute distance deviation between the actual displacement to be measured and the first and second electromagnetic coils respectively; The absolute distance deviation is compared with the set safe avoidance dead zone. If either absolute distance deviation is less than the safe avoidance dead zone, the judgment condition is not met and the self-calibration task is automatically suspended. If both absolute distance deviations are greater than or equal to the safe avoidance dead zone, the judgment condition is met.

[0007] Furthermore, obtaining the first absolute propagation time within the first dynamic time window and the second absolute propagation time within the second dynamic time window specifically includes the following steps: Divide the known distances from the first and second electromagnetic coils to the detector coil by the preset reference wave velocity to obtain the first prediction time and the second prediction time; and before performing the division operation, verify that the preset reference wave velocity is close to zero and forcibly overwrite it with the factory-calibrated wave velocity. The first and second prediction times are used as the center to expand the tolerance margin to both sides, and the first and second dynamic time windows are generated accordingly. Within the generated first dynamic time window, extract the extreme points that are confirmed as valid arrival times to obtain the first absolute propagation time. Within the generated second dynamic time window, extract the extreme points that are confirmed as valid arrival times to obtain the second absolute propagation time.

[0008] Furthermore, the extreme points corresponding to the confirmed valid arrival times are extracted within the first dynamic time window as the first absolute propagation time, and the extreme points corresponding to the confirmed valid arrival times are extracted within the second dynamic time window as the second absolute propagation time. This specifically includes the following steps: By using a hardware timer, a valid enable level is output only within the time interval of the first and second dynamic time windows to enable the signal acquisition channel, and an invalid level is forcibly output outside the time interval to physically cut off and shield non-target interference signals. Within the time interval of activating the signal acquisition channel, the absolute amplitude, zero-crossing slope, and continuous positive pulse width characteristics of the received induced voltage signal are simultaneously verified. When the characteristics of the three dimensions of absolute amplitude, zero-crossing slope, and continuous positive pulse width all conform to the original physical properties of the target torsional stress wave, the current extreme point is confirmed as the effective arrival time. The effective arrival times confirmed in the first dynamic time window and the second dynamic time window are respectively used as the first absolute propagation time and the second absolute propagation time.

[0009] Furthermore, after obtaining the first absolute propagation time and experiencing a physical delay time, an excitation pulse current is applied to the second electromagnetic coil and a pulse current is synchronously applied to the waveguide wire, specifically including the following steps: After the excitation pulse current is applied to the first electromagnetic coil, the internal hardware delay timer is started, and the physical delay time is inserted with the lower limit threshold being strictly greater than the quotient obtained by dividing the maximum physical total length of the waveguide wire by the minimum expected wave velocity under extreme low temperature conditions. The excitation action on the second electromagnetic coil is forcibly suspended during the physical delay time, and after the physical delay time has elapsed, the excitation pulse current is resumed to the second electromagnetic coil and the pulse current is synchronously applied to the waveguide wire.

[0010] Furthermore, the flight time difference is obtained by subtracting the first absolute propagation time and the second absolute propagation time. The measured wave velocity is then calculated by combining the pre-stored calibration interval with the flight time difference. This process includes the following steps: The flight time difference is obtained by subtracting the first absolute propagation time and the second absolute propagation time and performing absolute value calculation. Determine if the flight time difference is less than the effective time difference lower limit. The effective time difference lower limit is the quotient obtained by dividing the calibration interval by the theoretical maximum wave speed limit. If it is, the currently captured data is forcibly discarded and the wave speed calculation is exited. If not, the pre-stored calibration interval is divided by the measured flight time difference to calculate the measured wave speed.

[0011] Further, the ratio of the measured wave velocity to the preset reference wave velocity is calculated to obtain the calibration compensation coefficient. The preset reference wave velocity is then corrected using the calibration compensation coefficient to obtain the calibrated new wave velocity. After the calibrated new wave velocity meets the convergence condition, it is written to the memory. The specific steps include: The measured wave velocity is divided by the preset reference wave velocity to obtain the calibration compensation coefficient. When it is determined that the calibration compensation coefficient is within the preset constant range, the calibration compensation coefficient is multiplied by the preset reference wave velocity to obtain the new calibrated wave velocity. The new wave velocity generated after this self-calibration correction is used as a new benchmark to trigger the bottom-level self-calibration closed loop again. When the difference in calibration coefficients obtained in two consecutive rounds of calculation is less than the preset error tolerance value and approaches the constant 1.0, the self-calibration algorithm network is determined to meet the convergence condition. After the convergence condition is met, the new wave velocity after calibration is replaced and written to the specified mapping address of the non-volatile memory chip via the communication bus, and then overwritten into the memory.

[0012] A second aspect of the present invention provides a self-calibration device for a magnetostrictive displacement sensor, applicable to the self-calibration method for a magnetostrictive displacement sensor according to any one of the above claims, comprising: Waveguide assembly, which contains waveguide wires; A dual electromagnetic coil assembly includes a first electromagnetic coil and a second electromagnetic coil. The first electromagnetic coil and the second electromagnetic coil are coaxially sleeved on the outside of the waveguide wire assembly, and there is a preset calibration distance between them. Waveguide sheet, mounted at one end of the waveguide wire assembly; The detector coil is positioned at the corresponding location on the waveguide plate; The coil excitation circuit is connected to the first electromagnetic coil and the second electromagnetic coil respectively; The pulse excitation circuit is connected to the waveguide wire assembly; The signal processing module has its input terminal connected to the output terminal of the detector coil; The calculation and storage module is connected to the coil excitation circuit, pulse excitation circuit and signal processing module respectively. It is used to issue trigger commands, extract time windows, calculate wave velocity and write the calibrated new wave velocity to the internal storage unit.

[0013] Furthermore, the specific assembly structure of the first electromagnetic coil and the second electromagnetic coil includes: the outer surface of the waveguide wire assembly is covered with an insulating sleeve, a shielding layer and a protective tube from the inside out; the first electromagnetic coil and the second electromagnetic coil adopt a frameless self-adhesive winding structure and are coaxially installed on the outside of the insulating sleeve.

[0014] Furthermore, the computing and storage module integrates a hardware timer for constructing time window signal gating and filtering; the control output of the hardware timer is directly connected to the sampling enable terminal of the A / D conversion circuit inside the signal processing module.

[0015] This invention provides a self-calibration method and apparatus for a magnetostrictive displacement sensor. It offers the following advantages: 1. This invention introduces a safety avoidance dead zone determination mechanism. Before starting the self-calibration process, it uses multiple consecutive frames of position weighting to calculate the actual displacement to be measured and verifies its absolute distance deviation from the dual electromagnetic coils in real time. When the position magnet is too close to the calibration coil, the calibration task is actively suspended. This mechanism effectively prevents the original stress wave excited by normal displacement measurement from physically meeting and interfering with the calibration stress wave in the waveguide wire medium, thus ensuring the time-domain independence of the self-calibration signal and the accuracy of subsequent time point extraction from the source.

[0016] 2. This invention employs a signal filtering technique that combines dynamic time windows with underlying hardware gating. Based on theoretical wave velocity and fixed spacing, it predicts the arrival time of stress waves and uses a hardware timer to directly control the sampling enable terminal of the A / D conversion circuit. Outside the prediction time window, the capture channel is physically cut off to shield background noise, while the amplitude, slope, and pulse width of the signal are simultaneously verified within the time window. This hardware and software collaborative mechanism can absolutely isolate non-target echoes outside the solution window, improving the anti-interference capability and signal-to-noise ratio of weak target stress wave extraction in complex industrial environments.

[0017] 3. This invention sets a forced physical delay time in the dual-coil asynchronous excitation stage and configures multi-round closed-loop convergence verification and underlying error prevention logic in the wave velocity inversion stage. The forced delay time is greater than the waveguide wire's limit transmission time, completely eliminating time-domain aliasing of the two calibration stress waves; at the same time, combined with anti-zero division operation, fault tolerance time difference lower limit, and calibration coefficient boundary limit, it eliminates the risk of parameter distortion and system crash caused by single random environmental noise. This design ensures that the new wave velocity parameters finally overwritten to memory are absolutely robust, realizing high-precision autonomous online calibration of the sensor under long-term service and temperature drift. Attached Figure Description

[0018] Figure 1 This is the logic diagram of the full-process self-calibration and wave velocity inversion closed-loop control of the magnetostrictive displacement sensor of the present invention; Figure 2 This is a schematic diagram of the overall self-calibrating magnetostrictive displacement sensor of the present invention; Figure 3 for Figure 2 Enlarged structural diagram at point A in the middle.

[0019] The components include: 1. Waveguide wire; 2. Insulating sleeve; 3. Shielding layer; 4. Protective tube; 5. First electromagnetic coil; 6. Second electromagnetic coil; 7. Waveguide sheet; 8. Detector coil; 9. Pulse excitation circuit; 10. Signal processing module; 11. Calculation and storage module; 12. Coil excitation circuit; and 13. Position magnet. Detailed Implementation

[0020] 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.

[0021] See attached document Figure 2 and attached Figure 3 The present invention provides a self-calibration device and method for a magnetostrictive displacement sensor, which may include the following:

[0022] The self-calibration device for the magnetostrictive displacement sensor includes a waveguide wire 1, an insulating sleeve 2, a shielding layer 3, a protective tube 4, a first electromagnetic coil 5, a second electromagnetic coil 6, a waveguide sheet 7, a detector coil 8, a pulse excitation circuit 9, a signal processing module 10, a calculation and storage module 11, a coil excitation circuit 12, and a position magnet 13.

[0023] The waveguide wire assembly is sequentially covered by an insulating sleeve 2, a shielding layer 3, and a protective tube 4. A first electromagnetic coil 5 and a second electromagnetic coil 6 form a dual electromagnetic coil assembly. Both the first electromagnetic coil 5 and the second electromagnetic coil 6 are self-adhesive wire-wound and, after curing, coaxially sleeved on the outside of the insulating sleeve 2. A high-precision calibrated spacing exists between the first electromagnetic coil 5 and the second electromagnetic coil 6. .

[0024] Waveguide plate 7 is mounted at one end of the waveguide wire assembly. Detector coil 8 is positioned at the corresponding location on waveguide plate 7.

[0025] The coil excitation circuit 12 is connected to the first electromagnetic coil 5 and the second electromagnetic coil 6, respectively. The pulse excitation circuit 9 is connected to the waveguide wire assembly. The output terminal of the detector coil 8 is connected to the input terminal of the signal processing module 10. The signal processing module 10 is connected to the calculation and storage module 11. The calculation and storage module 11 is connected to both the coil excitation circuit 12 and the pulse excitation circuit 9, respectively.

[0026] The calculation and storage module 11 sends a trigger command to the coil excitation circuit 12. The coil excitation circuit 12 generates an excitation pulse current to provide excitation to the first electromagnetic coil 5 or the second electromagnetic coil 6, generating a local transient magnetic field at the corresponding position.

[0027] The computing and storage module 11 sends a trigger command to the pulse excitation circuit 9. The pulse excitation circuit 9 applies a pulsed current to the waveguide wire assembly. The pulsed current on the waveguide wire assembly interacts with the local transient magnetic field, exciting a torsional stress wave.

[0028] Torsional stress waves propagate along the waveguide wire assembly to the waveguide plate 7. The detector coil 8 outputs an induced voltage signal based on the inverse magnetostrictive effect.

[0029] The signal processing module 10 receives and processes the induced voltage signal output by the detector coil 8. The signal processing module 10 sends the processed signal to the calculation and storage module 11. The calculation and storage module 11 performs time window extraction, wave velocity calculation, and calibration operations.

[0030] Reference Appendix Figure 1 The overall workflow of this invention is as follows: The calculation and storage module 11 obtains the real-time distance between the magnet 13 and the detector coil 8 at the current position. The calculation and storage module 11 determines the real-time distance. Does the distance from the first electromagnetic coil 5 and the second electromagnetic coil 6 meet the requirements for safe avoidance of dead zones? If the conditions are met, the system will initiate a self-calibration process.

[0031] The coil excitation circuit 12 applies an excitation pulse current to the first electromagnetic coil 5. The pulse excitation circuit 9 applies an excitation pulse current to the waveguide wire assembly at a starting time of... The pulse current. Calculation and storage module 11 is based on the predicted arrival time. and tolerance margin A first dynamic time window is set. The signal processing module 10 extracts the actual arrival time of the first stress wave within the first dynamic time window. .

[0032] After physical delay Then, the coil excitation circuit 12 applies an excitation pulse current to the second electromagnetic coil 6. The pulse excitation circuit 9 applies an excitation pulse current to the waveguide wire assembly at a starting time of... The pulse current. Calculation and storage module 11 is based on the predicted arrival time. and tolerance margin A second dynamic time window is set. The signal processing module 10 extracts the actual arrival time of the second stress wave within the second dynamic time window. .

[0033] The computing and storage module 11 calculates based on the start time. and actual arrival time Calculate the flight time of the first stress wave. Calculation and storage module 11 calculates based on the start time. and actual arrival time Calculate the flight time of the second stress wave. The calculation and storage module 11 calculates the time difference between the first and second stress waves. .

[0034] The computing and storage module 11 is based on high-precision calibration spacing. and flight time difference Calculate the measured wave velocity .

[0035] Calculation and storage module 11 calculates the measured wave velocity. Compared with the reference wave speed The ratio of the two values ​​is used to obtain the calibration compensation coefficient. .

[0036] The calculation and storage module 11 utilizes calibration compensation coefficients For reference wave speed Make corrections to obtain the new calibrated wave velocity. .

[0037] The calculation and storage module 11 determines whether the difference in wave velocity between two consecutive inversions meets the convergence condition. If it does, the calculation and storage module 11 will calibrate the new wave velocity. Write to memory, complete wave velocity calibration, and switch to normal measurement mode.

[0038] See attached document Figure 2 and attached Figure 3 To achieve the aforementioned high-precision wave velocity inversion and error compensation, this invention provides a self-calibration device for a magnetostrictive displacement sensor, the specific structure and function implementation of which include the following:

[0039] The waveguide wire assembly includes a waveguide wire 1, an insulating sleeve 2, a shielding layer 3, and a protective tube 4. In this embodiment, the waveguide wire 1 is made of a magnetostrictive material such as iron-nickel alloy, iron-gallium alloy, or cobalt-iron-boron alloy. These materials possess high magnetostriction coefficients and good temperature stability of elastic modulus, providing a physical basis for low-loss transmission of torsional stress waves. The insulating sleeve 2 is coaxially fitted around the outside of the waveguide wire 1, providing physical assembly support while achieving electrical isolation. The first electromagnetic coil 5 and the second electromagnetic coil 6 are coaxially fitted around the outside of the insulating sleeve 2. The shielding layer 3 covers the outside of the first electromagnetic coil 5 and the second electromagnetic coil 6. The protective tube 4 is fitted around the outside of the shielding layer 3. The protective tube 4 is made of stainless steel or aluminum alloy and is used to form overall protection for the internal components.

[0040] As a preferred embodiment, the first electromagnetic coil 5 and the second electromagnetic coil 6, which are formed by a self-adhesive winding process and have no frame as described in the specification, are a specific implementation of the lower-level features of the electromagnetic coil involved in the claims. In other equivalent embodiments, the electromagnetic coil can also be mounted on the outside of the insulating sleeve 2 using a conventional winding structure with a thin-walled non-magnetic frame. The two are technically equivalent in achieving the function of generating a local axial magnetic field and exciting torsional stress waves.

[0041] The physical installation distance between the first electromagnetic coil 5 and the second electromagnetic coil 6 is calibrated during the assembly stage using precision equipment such as a laser interferometer or a coordinate measuring machine to obtain a high-precision calibrated distance. To ensure the confidence level of the wave velocity inversion formula and avoid systematic errors introduced by a single scale, high-precision calibration spacing is required. The calibration accuracy is better than ±0.01mm. This high-precision calibration spacing... It is stored in the calculation and storage module 11 and serves as the physical reference constant for calculating the measured wave velocity in the self-calibration algorithm.

[0042] A thin waveguide sheet 7 is radially welded to one end of the waveguide wire 1. A detector coil 8 is directly mounted on the waveguide sheet 7. Based on the propagation characteristics of stress waves at the interface of heterogeneous structures, when the torsional stress wave excited at the first electromagnetic coil 5 or the second electromagnetic coil 6 propagates along the waveguide wire 1 to the location of the waveguide sheet 7, the local permeability of the waveguide sheet 7 undergoes periodic changes due to the inverse magnetostriction effect, causing the induced voltage of the detector coil 8 to generate a corresponding fluctuation signal. The radially welded waveguide sheet 7 structure enables the energy convergence of the torsional stress wave, increasing the effective detection area while improving the amplitude and resolution of the detection signal.

[0043] The coil excitation circuit 12 is connected to the first electromagnetic coil 5 and the second electromagnetic coil 6, respectively, and outputs a stable excitation current to generate a controllable axial transient magnetic field in the waveguide wire 1. Based on this, the pulse excitation circuit 9 is connected to the waveguide wire 1 and applies a short-time pulse current to it. The short-time pulse current, in conjunction with the axial transient magnetic field generated by the first electromagnetic coil 5 or the second electromagnetic coil 6, excites a torsional stress wave at the corresponding coil mounting position based on the Wiedemann effect in magnetostriction.

[0044] The signal processing module 10 is connected to the output terminal of the detector coil 8. The signal processing module 10 integrates a preamplifier circuit, a bandpass filter circuit, an A / D conversion circuit, and a signal recognition circuit. The induced voltage signal output from the detector coil 8 is sequentially processed by the preamplifier circuit and the bandpass filter circuit for signal conditioning. The specific circuit topologies of the preamplifier circuit and the bandpass filter circuit can be selected and designed by those skilled in the art based on the conventional requirements for weak signal amplification; their specific circuit designs are well-known in the field and will not be elaborated upon here.

[0045] The computing and storage module 11 manages the entire self-calibration process. To achieve accurate removal of complex simultaneous interpretation interference signals, the computing and storage module 11 integrates a hardware timer, whose control output is physically connected to the sampling enable terminal of the A / D conversion circuit in the signal processing module 10. The specific coordination logic between the signal processing hardware and the gating trigger link needs to be constructed based on the theoretical expected evolution relationship of the Time-of-Flight (TOF) method. This will be explained in detail in the following steps.

[0046] The calculation and storage module 11 obtains the known distance from the first electromagnetic coil 5 to the detector coil 8. and the current storage baseline speed To prevent system crashes due to division by zero anomalies, the system verifies the baseline speed before computation. Does it meet the requirements? Under the premise that the error prevention conditions are met, the calculation and storage module 11 calculates the first prediction time of the first torsional stress wave. The calculation formula is: ; In the formula, This represents the a priori flight time required for the target stress wave to travel from the excitation point to the detector under ideal drift-free conditions. This is the nominal physical distance between the first electromagnetic coil and the detector coil; The reference propagation velocity of the stress wave is generated in the previous cycle of the system or calibrated at the factory.

[0047] After obtaining the prior flight time, the calculation and storage module 11 uses the first predicted time. Centered on the time axis, combined with a preset tolerance margin Set the first dynamic time window. The time interval of the first dynamic time window is... Tolerance margin The value of is based on the small wave velocity drift caused by the maximum expected ambient temperature gradient and the envelope width of the inherent waveform of the stress wave. It is usually set as a constant in the range of 10 to 30 microseconds. In this embodiment, based on the dispersion characteristics of the long waveguide wire 1, it is preferably 20 microseconds to ensure that the signal time shift caused by the small fluctuation of the real wave velocity can be completely covered.

[0048] The computing and storage module 11 outputs a valid enable level to the sampling enable terminal of the A / D conversion circuit within the time interval of the first dynamic time window via an internal hardware timer. The A / D conversion circuit only starts signal acquisition and analog-to-digital conversion during the period when it receives the valid enable level. Outside the time interval of the first dynamic time window, the computing and storage module 11 outputs an invalid level, and the A / D conversion circuit stops sampling. The hardware gating mechanism controlling the sampling enable terminal physically shields and filters out non-target interference echo signals falling outside the first dynamic time window, thereby achieving high signal-to-noise ratio extraction of a single target signal from multi-source aliased echo data.

[0049] After processing and storing the first signal, the calculation and storage module 11 obtains the known distance from the second electromagnetic coil 6 to the detector coil 8. Based on the same temporal evolution relationship, the computation and storage module 11 calculates and stores data according to the known distance. and reference speed Calculate the second prediction time of the second torsional stress wave. The calculation formula is: ; In the formula, The expected arrival time of the stress wave excited by the second electromagnetic coil; The nominal distance 5 between the second electromagnetic coil 6 and the detector coil 8. The first electromagnetic coil 5 is calculated and stored by the first electromagnetic coil 5 using the second prediction time. Centered on the time axis, combined with a preset tolerance margin Set a second dynamic time window. The time interval of the second dynamic time window is... .

[0050] The computing and storage module 11 uses an internal hardware timer to output a valid enable level to the sampling enable terminal of the A / D conversion circuit within the time interval of the second dynamic time window. During this interval, the system enables signal acquisition and extracts the arrival time of the second torsional stress wave.

[0051] The computation and storage module 11 described in the specification directly controls the sampling enable terminal of the A / D conversion circuit through a hardware timer to achieve a dynamic time window structure, which fully discloses the time window extraction gating technology features involved in the claims. In other equivalent embodiments, the computation and storage module 11 can also be connected to the enable terminal of the analog comparator in the signal processing module 10, and the same time interval filtering function can be achieved by controlling the working state of the analog comparator. This is a technically equivalent means and also falls within the protection scope of this invention.

[0052] Reference Appendix Figure 1 Based on the general acoustic theory of waveform interference and time-domain superposition, the system executes a measurement safety protection mechanism and position avoidance logic before the self-calibration process of the magnetostrictive displacement sensor is initiated. Since the position magnet 13 generates a high-frequency native stress wave during normal displacement measurement, if this stress wave encounters the calibration stress wave excited by the self-calibration dual electromagnetic coils on the waveguide wire, complex waveform interference and phase distortion will occur, leading to the failure of time-of-flight extraction. Based on the above physical mechanism, the specific judgment and execution logic is broken down in detail according to the following steps: S101: System status parameter acquisition and initialization. When the self-calibration command is triggered, the sensor is in normal working state or standby state, and both the first electromagnetic coil 5 and the second electromagnetic coil 6 in the dual electromagnetic coil assembly are in a power-off and idle state. The calculation and storage module 11 acquires the actual displacement to be measured from the current position magnet 13 to the detector coil 8. , where the variable Specifically, it is defined as the real-time object-embedded distance between the center point of the vernier magnet and the effective receiving end face of the detector coil. Simultaneously, the calculation and storage module 11 retrieves the known distance from the installation position of the first electromagnetic coil to the detector coil from its internal storage unit. The known distance from the installation location of the second electromagnetic coil to the detector coil and preset safety avoidance thresholds As a preferred approach, this safety avoidance threshold... This constitutes the core safety avoidance dead zone of the self-calibration operation. Its specific value is not fixed, but is determined by the physical envelope width of the inherent waveform of the stress wave and the system damping attenuation characteristics of the sensor. Generally, its value range is set to 50mm to 100mm. In this embodiment, it is preferred to set the upper limit of 100mm in combination with the attenuation coefficient of the waveguide wire 1 medium to accommodate waveform tailing interference under most extreme temperature conditions.

[0053] S102: Position Interference Risk Calculation and Judgment. The calculation and storage module 11 calculates the absolute distance deviation between the current position of the position magnet 13 and the first electromagnetic coil 5 and the second electromagnetic coil 6, respectively, based on the acquired position parameters. To avoid misjudgment of spatial position jumps caused by environmental vibration noise at a single moment, the system introduces a multi-frame position weighting judgment logic here, that is, it does not rely on a single extreme value, but selects the most recent value. The root mean square value of the position within the next normal measurement cycle is used as the current displacement to be measured. Valid input parameters are used to improve the robustness of state evaluation. The specific decision logic involves verifying whether the following inequality conditions are met: ; or ; In the formula, The actual distance to be measured for position magnet 13 is obtained under normal measurement mode; The position of the first electromagnetic coil; This is the position of the second coil; The core technical purpose of the above formula is to quantify the degree of physical interference when a dynamically moving magnet intrudes into the internal calibration buffer zone, thus setting a safety avoidance threshold.

[0054] S103: Interference Risk Handling and Self-Calibration Task Suspension. When the distance calculation result satisfies any of the above inequalities, the system determines that the position magnet 13 is too close to a calibration coil. Under this physical distance constraint, the interference stress wave excited by normal displacement measurement will enter the dynamic capture window of the self-calibration signal, thus causing waveform aliasing in the time domain with the target calibration stress wave. Based on this anti-collision determination, the calculation and storage module 11 actively postpones or suspends this self-calibration task, forcing the control system to continue maintaining the normal measurement mode. The system continuously monitors the real-time displacement of the position magnet 13 in the background. The self-calibration will be retried only after the confirmed position magnet 13 has moved out of the safety avoidance dead zone.

[0055] S104: Security release and self-calibration activation. If the computation and storage module 11 verifies... and The distance between the position magnet 13 and both calibration coils exceeds the interference dead zone limited by the safety threshold, thus determining safety. The calculation and storage module 11 is released from the suspended state, and the control coil excitation circuit 12 officially enters the electromagnetic coil excitation stage. The above avoidance logic is quantitatively explained with reference to a specific embodiment. In this embodiment, the system sets a unilateral safety avoidance dead zone. cm, distance of the first electromagnetic coil from the detector coil cm, distance of the second electromagnetic coil from the detector coil cm. When the self-calibration timer is triggered, if the currently normal measurement data is... cm. The control module performs a safety check: and ; The calculated deviations of 70cm and 30cm are both strictly greater than the 10cm safety threshold. The system determines there is no risk of waveform overlap interference and allows calibration to begin. Conversely, if a deviation is detected... cm, due to If the minimum setting limit is strictly less than 10cm, and the position magnet 13 falls into the interference dead zone of the first electromagnetic coil 5, the system will actively postpone this self-calibration operation.

[0056] Furthermore, the establishment of collision avoidance logic and the tolerance margin in the subsequent dynamic time window. The extraction is closely related. Based on the fundamental theorem of uniform propagation of sound waves in solid media, the physical calculation of the time span needs to be mapped through the division quotient of spatial displacement and propagation speed. During subsequent division operations, to prevent system initialization anomalies from causing the internally stored reference wave velocity to reach a minimum or even zero value, the calculation and storage module 11 incorporates an anomaly handling logic when the division denominator approaches 0: when an anomaly is detected... Approaching 0 (e.g., detected) When an abnormally low physical value (m / s) is encountered, the system automatically intercepts the interrupt and forces a reversal. The parameters are overridden to the factory default ideal wave speed of 2800m / s to ensure the integrity of the underlying timing operations and the ability to prevent crashes.

[0057] Known system preset reference wave velocity m / s, distance of the dead zone The formula for calculating the corresponding time span safety boundary in the time domain is: ; Among the symbols Defined as the theoretical lower bound of the time required for the interference waveform to completely cross the safe dead zone. Substituting the physical parameters, the calculation yields... To ensure that the interference echo generated by magnet 13 outside the dead zone is absolutely isolated outside the acquisition window, while effectively accommodating the time deviation caused by the slight drift of the true wave velocity, the tolerance margin of the dynamic time window is... It must be less than this time span. In this embodiment, the time window tolerance margin is precisely set to... Strictly satisfies the condition of being less than The security isolation requirements are as follows. Regarding the configuration of the underlying hardware timer for acquiring displacement data and driving subsequent time window gating, those skilled in the art can perform conventional calculations and timing writes based on the internal clock frequency of the selected microprocessor; this is well-known technology in the field and will not be elaborated upon here.

[0058] Reference Appendix Figure 1 Based on the measurement safety protection mechanism and position avoidance logic established above, the system avoids the risk of waveform overlap in extreme cases at the macroscopic timing level. As a common technique for acoustic ranging and weak signal detection, the time-gating principle aims to shield background noise and non-target echoes outside the expected arrival time using a preset time-domain mask. To thoroughly filter out the native interference echo of the position magnet 13 in the context of simultaneous interpretation at the microscopic signal extraction level, the system introduces dynamic time-window gating technology in the self-calibration process. The specific technical implementation of this core anti-interference action is disclosed and elaborated in detail through the following sub-steps: S201: Dynamic Time Window Prediction Parameter Construction. Before executing the dual electromagnetic coil excitation command, the calculation and storage module 11 calculates the theoretical time node for the target stress wave to reach the detector coil 8 based on the internally stored spatial physical dimensions and wave velocity reference. The calculation logic corresponds to the first electromagnetic coil 5 and the second electromagnetic coil 6, respectively, and the relevant underlying mathematical operation relationships are as follows: ; ; In the formula, The preset stress wave propagation reference speed in the system storage unit; The known fixed distance from the installation position of the first electromagnetic coil 5 to the detector coil; The known fixed distance from the installation position of the second electromagnetic coil 6 to the detector coil; This represents the predicted arrival time of the first stress wave based on the position parameters of the first electromagnetic coil 5. This represents the predicted arrival time of the second stress wave, established based on the position parameters of the second electromagnetic coil 6.

[0059] The physical meaning of the above formula lies in accurately mapping the theoretical time-domain coordinates of the target stress wave from a spatial scale. Regarding the division operation mentioned above, to avoid abnormal operating conditions... System division-by-zero crashes caused by data loss or register clearing are addressed by the built-in low-level out-of-bounds check logic in the computing and storage module 11: when the input parameter is checked... When the wave velocity approaches 0 or falls below the preset effective lower limit (e.g., 100 m / s), the system will forcibly retrieve the factory-calibrated wave velocity from the read-only memory as the replacement divisor, thereby ensuring the completeness and robustness of the time-domain prediction algorithm. These two prediction time parameters constitute the absolute center reference axis for the subsequent establishment of the gated time window.

[0060] S202: Tolerance Margin Extraction and Capture Interval Locking. Based on the predicted arrival time obtained above, the system introduces a tolerance margin to widen the capture window boundary. This tolerance margin is specifically defined as the tolerance half-width of the dynamic time window, and its numerical execution interval expression is as follows: ; In the formula, In the specific timing control process, the current excitation state is used as the reference. or ; This represents the preset tolerance margin. Due to temperature drift and internal physical stress changes in the waveguide wire 1 medium in actual industrial environments, the actual wave velocity relative to the theoretical reference velocity will vary. A slight offset is inevitable. The core technical purpose of introducing this tolerance half-width is to reserve a reasonable capture tolerance width to accommodate the time advance or lag of the target electromagnetic coil echo. Due to the physical constraints of the pre-avoidance logic, The value must not intrude into the time dead zone established by the safety avoidance threshold of the position magnet 13. In this embodiment, the calculation and storage module 11 calculates this tolerance margin. Precise configuration to 20 As a preferred method, the 20 The value is not determined blindly based on experience, but is calculated by combining the wave velocity limit drift (approximately ±0.5%) caused by the maximum expected temperature range of waveguide wire 1 (e.g., -40℃ to +80℃) and the system damping coefficient of the detector coil. This ensures that the target wave peak can be captured under all effective temperature conditions, while also having the highest anti-interference signal-to-noise ratio.

[0061] S203: Hardware Enable Control and Low-Level Electrical Mapping. To directly translate the abstract time-domain algorithm into physical circuit-level isolation actions to support absolute shielding against interference and noise, this embodiment employs a hardware enable level gating mechanism to implement this lower-level functional feature. When the coil excitation circuit 12 outputs a transient drive current to the designated electromagnetic coil, the microcontroller hardware timer integrated within the computing and storage module 11 synchronously starts zero-point timing. To address the alignment requirements of multi-source timing data, the sampling clock of the system's underlying analog-to-digital converter and the hardware timer are forced to share the same high-precision external crystal oscillator source, preventing time phase slippage caused by different clock sources. The computing and storage module 11 is directly electrically connected to the sampling enable terminal of the analog-to-digital converter in the signal processing module 10, or directly connected to the state control terminal of the front-end hardware comparator, through its peripheral general-purpose input / output port. During the period when the count value inside the timer is lower than the lower limit of the capture interval, this control pin is forcibly pulled low or high to output an invalid level signal. Under the continuous constraint of this invalid level, the subsequent digital quantization and feature recognition channels of the signal processing module 10 are physically cut off, and the system forcibly ignores and shields any stray voltage fluctuations of the detector coil 8 excited by the native stress wave of the position magnet 13 during this period.

[0062] S204: Target Stress Wave Extraction and Gated Lockout. As the underlying system clock source continuously accumulates, when the timer count enters the valid capture interval, the output pin of the calculation and storage module 11 immediately flips its level, inputting a valid enable level to the signal processing module 10, officially activating the signal capture channel. During this period, the signal processing module 10 pre-amplifies and identifies the weak induced voltage of the target received by the detector coil 8. To avoid the defect of a single extreme value determination logic being susceptible to random high-frequency spike noise interference, a multi-dimensional feature verification mechanism is introduced when extracting the extreme point of the actual arrival time of the target stress wave: the system not only checks in real time whether the absolute amplitude of the sampled data exceeds the preset environmental noise threshold, but also simultaneously verifies the zero-crossing slope and continuous positive pulse width of the signal envelope. Only when the characteristics of the amplitude, slope, and pulse width all conform to the original physical properties of the target torsional stress wave is the current extreme point confirmed as a valid arrival time. Once the count value exceeds the upper limit node of the interval, the enable level immediately switches back to the invalid state, and the capture channel is physically locked a second time. Based on the dual cutoff mechanism of strong correlation between the aforementioned time-domain mathematical window and the underlying hardware control pins, the self-calibration system achieves absolute filtering of non-target interference. Regarding the gain-bandwidth matching of the operational amplifier in signal processing module 10 and the setting of the front-end anti-aliasing filter frequency of the analog-to-digital converter, those skilled in the art can perform conventional table lookup and hardware parameter tuning based on the specific center frequency band of the measured signal. The circuit selection process is well-known in the field and will not be elaborated upon here.

[0063] See attached document Figure 2 This invention details the underlying execution logic of the self-calibration timing control and wave velocity inversion algorithm. Ultrasonic ranging technology based on Time-of-Flight (TOF) relies heavily on the constant propagation speed of stress waves in the transmission medium. Due to the temperature gradient distribution in industrial environments and the release of material stress from the long-term service of waveguide wire 1, the dynamic drift of wave velocity becomes the core physical bottleneck restricting the absolute measurement accuracy of the system. To eliminate this error at its source, the current real-time wave velocity must be calculated backward from a known, fixed physical spatial scale. After the dual electromagnetic coil assembly is assembled on the outside of the insulating sleeve of waveguide wire 1, the core challenge facing the system is how to avoid the mutual interference and aliasing of the two calibration stress waves in the time domain and accurately extract the time-of-flight difference to calculate the wave velocity correction parameters. To this end, this embodiment constructs an asynchronous excitation and physical delay control mechanism, and combines it with a wave velocity inversion model to achieve online self-calibration of the measurement system. The specific execution process unfolds through the following sub-steps: S301: Excitation and Absolute Propagation Time Extraction of the First Electromagnetic Coil 5. After the system completes the safety avoidance judgment and confirms no interference risk, the microprocessor inside the calculation and storage module 11 triggers the self-calibration start point. The microprocessor controls the coil excitation circuit 12 to output a transient excitation pulse current to the first electromagnetic coil 5. At the same moment, the pulse excitation circuit 9 synchronously injects a pulse current into the waveguide wire 1. Based on the magnetostrictive effect of the waveguide wire 1 material, the axial magnetic field generated by the coil interacts with the pulse current of the waveguide wire 1, exciting the first torsional stress wave at the installation position of the first electromagnetic coil 5. This stress wave propagates to both ends of the waveguide wire 1 at the reference velocity currently stored in the system. The microprocessor's underlying hardware clock capture unit synchronously records the start timestamp at the moment of excitation. In conjunction with the aforementioned dynamic time window gating capture mechanism, the signal processing module 10 accurately extracts the actual physical moment when the first stress wave arrives at the detector coil. The system calculates the absolute propagation time of the first stress wave based on this, and its underlying mathematical model is expressed as follows: ; In the formula, Characterizes the time span taken for the first stress wave to travel from the generation point of the first electromagnetic coil 5 to the detector coil; The arrival timestamp of the first stress wave obtained by the system using hardware gating measurement; To ensure a precise start timestamp for applying the excitation pulse to the first electromagnetic coil 5, a hardware timer with strict alignment is selected. and As an input parameter, it directly reflects the absolute physical causal relationship between the excitation pulse triggering and the zero-crossing response of the front-end detector voltage, eliminating measurement system deviations caused by asynchronous clock sources. Under the operating conditions given in this embodiment, the system measures the absolute propagation time of the first stress wave. for .

[0064] S302: Asynchronous Excitation Control and Forced Physical Delay. To prevent the overlap of the time-domain waveforms of the first stress wave and the subsequent second stress wave in the waveguide wire 1 medium from the physical source, the system forcibly switches to an asynchronous excitation and physical delay waiting phase. After the initial excitation action of the first electromagnetic coil 5 is completed, the calculation and storage module 11 does not immediately trigger the next coil excitation, but instead starts the internal hardware delay timer to forcibly insert a physical delay time between the two excitation actions. The setting of this delay time is mainly based on the overall length of the waveguide wire 1 and the minimum theoretical wave velocity in the medium. As a preferred method, this physical delay time... The determination of the lower limit threshold must meet the following criteria. ,in This represents the maximum total physical length of waveguide wire 1. This represents the minimum expected wave velocity under extreme low-temperature conditions. In this embodiment, the total length of waveguide wire 1 is set to 200cm. Since the maximum propagation time of the stress wave within this length range is only about 0.7ms, the control program forcibly locks the hardware delay time to 2ms. Because the 2ms delay span is much larger than the maximum possible residence time of the stress wave within the medium of waveguide wire 1, this time-domain isolation mechanism can absolutely ensure that the first stress wave has been completely transmitted to the end of waveguide wire 1 and thoroughly absorbed and dissipated by the end damping element. Regarding the selection of the damping element material and the design of the wave-absorbing structure, those skilled in the art can perform conventional selection and parameter matching based on the specific vibration frequency of waveguide wire 1. Its vibration reduction and wave absorption principle is a well-known technology in the field and will not be elaborated here.

[0065] S303: Excitation and arrival time measurement of the second electromagnetic coil 6. After the delay timer overflows, the calculation and storage module 11 is released from its suspended state, and the control coil excitation circuit 12 applies an excitation pulse current with the same electrical parameters as the first coil to the second electromagnetic coil 6. Through synchronous coordination with the pulse current of the waveguide wire 1, the system excites a second torsional stress wave at the fixed installation position of the second electromagnetic coil 6. The underlying hardware clock capture unit synchronously records the start timestamp of the second excitation. The system again calls the dynamic time window algorithm to identify and extract the actual arrival time of the second stress wave, and calculates the absolute propagation time of the second stress wave. ; In the formula, Characterizes the time span taken for the second stress wave to travel from the generation point of the second electromagnetic coil 6 to the detector coil; To ensure the effective arrival time stamp of the second stress wave captured by gating; This is the excitation start time stamp of the second electromagnetic coil 6. In this embodiment, the system measures the propagation time of the second stress wave. for .

[0066] S304: Dual-source stress wave time-of-flight calculation. After obtaining two sets of independently transmitted time parameters, the calculation and storage module 11 calculates the absolute time difference of flight of the stress wave over the physical installation distance between the two electromagnetic coils based on the core principle of the Time-of-Flight (TOF) method. The specific calculation logic for this propagation time difference is as follows: ; In the formula, This represents the measured time difference consumed by the stress wave as it travels the known distance between the first electromagnetic coil 5 and the second electromagnetic coil 6; the absolute value calculation is used to shield against sign reversal interference caused by the difference in the arrangement order of the two coils near the detector. Substituting the underlying acquisition data of this embodiment into the model, the propagation time difference is calculated. for .

[0067] S305: Wave velocity inversion and calibration compensation coefficient calculation. After obtaining high-precision time difference data, the system enters the core wave velocity inversion stage. The calculation and storage module 11 extracts the pre-stored calibration interval data in the internal non-volatile memory and, combined with the measured flight time difference, inverts the true stress wave propagation velocity under the current temperature change and stress conditions based on kinematic relationships: ; In the formula, This represents the actual propagation speed of the stress wave, calculated based on actual measurements under the current measurement environment. This refers to the actual physical installation distance between the two electromagnetic coils, calibrated and fixed using precision equipment such as laser interferometers during the factory assembly stage. This relates to the inversion model mentioned above. In the division operation stage, to avoid triggering misjudgment due to abnormal operating conditions (such as crosstalk between two signals, short circuit in front-end hardware, or sudden high-frequency electromagnetic interference), the denominator is adjusted. In the event of a microprocessor division-by-zero exception or overflow crash caused by values ​​approaching zero, the computation and storage module 11 incorporates underlying fault-tolerant takeover logic. Specifically, the system presets a lower limit threshold for the effective time difference (this threshold is based on the calibration interval). Determined in conjunction with the theoretical maximum wave speed limit, for example, preset as When the real-time solution is obtained When the value is below the lower threshold, the system forcibly determines that the captured data is invalid, discards the current sample, exits the self-calibration calculation, and maintains the original calibration parameters unchanged, thereby ensuring the integrity and robustness of the method under extreme electrical interference. Based on the actual wave velocity obtained from the effective inversion, the system needs to calculate the wave velocity calibration coefficient to quantify the drift rate of the true wave velocity relative to the system's preset reference. The formula for calculating the calibration coefficient is as follows: ; In the formula, These are dimensionless calibration coefficients used for subsequent correction of the measurement model; This is the current reference velocity for stress wave propagation used in the system storage module. Substituting the specific physical parameters of this embodiment, it is known that… cm, m / s, The floating-point arithmetic unit within the calculation and storage module 11 performs the calculation operation to obtain the calibration coefficients. .

[0068] S306: Global Parameter Update and Convergence Iteration. After calculating the wave velocity offset ratio, the system uses this calibration coefficient to compensate for the global propagation velocity in the underlying measurement model. The conversion logic for the new stress wave propagation velocity is as follows: ; In the formula, This represents the latest stress wave propagation velocity parameters generated after this dual-coil self-calibration correction. Based on the above coefficient values, the updated actual wave velocity... m / s. The calculation and storage module 11 directly overwrites the result into the internal reference velocity register, completing the hot update of the parameters. To avoid the unilateral jump in the update result caused by random noise in a single measurement, the system does not rely solely on a single extreme value calculation for the final wave velocity output, but introduces a multi-round iterative trend verification logic. The system uses this updated velocity value as a reference to trigger the self-calibration verification process again. When the difference between the calibration coefficients obtained from two consecutive closed-loop calculations is less than the preset convergence threshold (e.g., 0.1%) and approaches the constant 1.0, the system determines that the calibration network has completed convergence. In this state, the sensor's bottom layer cuts off the excitation enable channel of the dual electromagnetic coils, the overall system architecture returns to the normal displacement measurement mode, and directly calls the updated high-precision wave velocity parameters. The flight time of the execution position cursor is calculated, thereby realizing the autonomous correction of environmental drift error.

[0069] See attached document Figure 2 Based on the two sets of stress wave propagation time parameters obtained, this embodiment elaborates on the underlying execution process of parameter iteration, storage, and normal measurement mode switching. To further explain the multi-round iterative trend verification logic mentioned in step S306, this embodiment further constructs a closed-loop control mechanism for parameter iteration, validity determination, and solidified storage, ensuring the absolute reliability of the output parameters through multi-dimensional logic. This process covers processing stages such as a new round of asynchronous excitation control, wave velocity inversion calculation, parameter storage update, and system state switching. The specific execution logic is as follows.

[0070] S401: A new round of asynchronous excitation and physical delay control mechanism is executed. To avoid physical waveform aliasing and temporal interference within the waveguide wire 1 medium caused by two consecutively excited stress waves, the calculation and storage module 11 re-triggers the pulse injection to the dual electromagnetic coils based on the updated reference wave velocity, and forcibly intervenes with asynchronous excitation logic between the two excitations. The underlying hardware triggers a physical delay time through an internal timer, suspending the excitation action of the second electromagnetic coil 6.

[0071] S402: Calculation of Secondary Flight Time Difference and Wave Velocity Inversion. After the physical delay ends and the second round of stress wave capture is completed, the calculation and storage module 11, based on the core mechanism of Time-of-Flight (TOF), retrieves the secondary timestamp data stored in its internal registers and performs the mathematical calculation of the absolute time difference of stress wave propagation between the two electromagnetic coils. The specific calculation model is as follows: ; In the formula, This represents the measured time difference between the stress wave passing through the physical distance between the first electromagnetic coil 5 and the second electromagnetic coil 6 during the second iteration measurement. and These represent the absolute propagation time for the new round of acquisition. For the extraction of multi-source time data, the system's underlying architecture strictly ensures that the timestamps are aligned to a unified hardware clock source. Absolute value operations are used to physically avoid algebraic sign reversal caused by the spatial arrangement of coils. For the extraction of multi-source time data, the system's underlying architecture strictly ensures... and Reference alignment on a unified hardware clock source.

[0072] Based on the aforementioned time difference data, the calculation and storage module 11 combines the measured time difference to invert the actual stress wave propagation velocity under the second iteration, and the mapping relationship is as follows: ; In the formula, The actual propagation velocity of the stress wave is obtained from the second iteration calculation; This refers to the factory-calibrated spacing between the first electromagnetic coil 5 and the second electromagnetic coil 6 on the sensor waveguide wire 1. For the aforementioned kinematic inversion model involving division, abnormal operating conditions where the denominator approaches a limiting state must be fully considered. When the measured flight time difference... When high-frequency electromagnetic crosstalk in industrial environments or short circuits in the front-end detection circuit cause values ​​to be abnormally low, even approaching zero, the microprocessor at the system's core faces a serious risk of crashing due to division-by-zero overflow. To address this, the computing and storage module 11 incorporates anti-crash interception logic: the system is based on the calibration interval... A time difference threshold is preset between the acoustic limiting wave velocity and the lower limit threshold (which is reasonably set in this embodiment). Once detected If the data falls below the lower threshold, the system directly determines that there is a physical anomaly in the captured timestamp, discards the current dirty data, and forcibly terminates the current wave velocity calculation, maintaining the original calibration parameters to ensure the robustness of the underlying architecture.

[0073] S403: Calculation and validity determination of secondary calibration compensation coefficient. To quantify the degree of wave velocity drift caused by the combined effects of environmental temperature change and material aging, the system uses the latest wave velocity from the previous update as the denominator to calculate the secondary calibration compensation ratio: ; In the formula, It is a dimensionless calibration compensation coefficient used to reflect the relative offset ratio of the real-time wave velocity relative to the preset reference. The calculation and storage module 11 stores the currently preset stress wave propagation velocity reference value. Substituting the physical calibration parameters from this embodiment into the calculation, the calibration spacing is known. cm, initial reference wave velocity m / s, measured time difference The system calculates the calibration compensation coefficient. Based on physical principles and the inherent temperature drift limits of waveguide wire 1 (such as iron-nickel alloy), the wave velocity drift rate under reasonable operating conditions is typically subject to strict physical constraints. Therefore, the system's calculated calibration compensation coefficients... A mandatory reasonable safety boundary is set (in this embodiment, its value range is constrained to the interval |0.95, 1.05|). If the calculated... If the value exceeds the physical limit boundary, the system determines that the single extreme value distortion is unreliable and refuses to perform subsequent corrections. After obtaining a valid compensation coefficient, the system uses this coefficient to update the global propagation speed. ; In the formula, This represents the latest stress wave propagation velocity parameters generated after calibration and compensation. Based on the calculation results, the corrected actual wave velocity... m / s.

[0074] S404: Parameter Verification and Convergence Iteration. To avoid one-sided jumps in the update results due to random fluid noise or local transient vibration interference in a single measurement, the system does not rely solely on a single extreme value calculation for the final wave velocity output. Instead, it introduces a multi-round iterative trend verification logic. The calculation and storage module 11 uses the updated velocity value... As a new benchmark, the underlying self-calibration verification loop is triggered again, and new physical timestamps are collected to calculate the secondary calibration coefficients. ; In the formula, The actual wave velocity is calculated based on two independent measurement data. The latest stress wave propagation velocity is calculated in the previous iteration. The system compares the correction parameters obtained from the two consecutive calculations. When the difference is less than a preset error convergence threshold (e.g., a deviation constraint of 0.1%) and the calibration coefficient is extremely close to a constant of 1.0, the system determines at the software level that the calibration algorithm network has completed physical convergence. In the secondary verification of this embodiment, The multidimensional convergence criteria are fully met, and the final output wave velocity is 2882.04 m / s.

[0075] S405: Parameter storage update and normal measurement mode switching. After confirming robust data convergence, the system seamlessly switches the running state machine from self-calibration mode back to normal business logic. At the hardware control level, the MCU's I / O interface sends a shutdown command to the coil excitation circuit 12, cutting off the power supply enable signals of the first electromagnetic coil 5 and the second electromagnetic coil 6, causing the two sets of dedicated calibration coils to enter a power-off sleep state to save system power consumption. At the data persistence level, the computing and storage module 11 transmits high-precision stress wave propagation speed data via SPI or I2C communication bus. It is written to a specified mapped address range of an internal non-volatile memory chip such as EEPROM or Flash, statically replacing the original one. Reference value. In subsequent continuous displacement measurement tasks, when the signal processing module 10 calculates the flight time of the movable vernier corresponding to the position magnet 13, it directly calls the updated absolute wave velocity parameter in the storage area. Displacement multiplication is performed. This rigorous process ensures that the measurement system autonomously completes closed-loop compensation and online accuracy alignment for the entire set of environmental drift errors without introducing any external physical standard parts.

Claims

1. A self-calibration method for a magnetostrictive displacement sensor, characterized in that, include: Calculate the absolute distance deviation between the actual displacement to be measured and the first electromagnetic coil (5) and the second electromagnetic coil (6). When both absolute distance deviations are not less than the safe avoidance dead zone, the judgment condition is confirmed to be met. When the determination condition is met, a pulse current is synchronously applied to the first electromagnetic coil (5) and the waveguide wire (1) to obtain the first absolute propagation time within the first dynamic time window; After a physical delay time, a pulse current is synchronously applied to the second electromagnetic coil (6) and the waveguide wire (1) to obtain the second absolute propagation time within the second dynamic time window; The flight time difference is obtained by subtracting the first absolute propagation time and the second absolute propagation time, and the measured wave velocity is calculated by combining it with the pre-stored calibration interval. The ratio of the measured wave velocity to the preset reference wave velocity is calculated to obtain the calibration compensation coefficient. The preset reference wave velocity is corrected using the calibration compensation coefficient. After the convergence condition that the difference between the calibration compensation coefficients calculated in two consecutive rounds is less than the preset error convergence threshold used to characterize the convergence of wave velocity determination is met, the data is overwritten into the memory.

2. The self-calibration method for a magnetostrictive displacement sensor according to claim 1, characterized in that, The calculation of the absolute distance deviation between the actual displacement to be measured and the first electromagnetic coil (5) and the second electromagnetic coil (6), and the confirmation that the judgment condition is met when both absolute distance deviations are not less than the safe avoidance dead zone, specifically includes the following steps: The root mean square value of the position within multiple consecutive normal measurement cycles is extracted as the actual displacement to be measured. Calculate the absolute distance deviation between the actual displacement to be measured and the first electromagnetic coil (5) and the second electromagnetic coil (6); When the absolute distance deviations of the two conditions are not less than the safe avoidance dead zone, the determination condition is confirmed to be met. If any of the absolute distance deviations is less than the safe avoidance dead zone, it is determined that the determination condition is not met.

3. The self-calibration method for a magnetostrictive displacement sensor according to claim 1, characterized in that, Obtaining the first absolute propagation time within the first dynamic time window and obtaining the second absolute propagation time within the second dynamic time window specifically includes the following steps: Divide the known distances from the first electromagnetic coil (5) and the second electromagnetic coil (6) to the detector coil (8) by the preset reference wave velocity to obtain the first prediction time and the second prediction time respectively. Before performing the division operation, if the preset reference wave velocity is less than the preset effective wave velocity lower limit, it is forcibly overwritten to the factory calibrated wave velocity. The first prediction time and the second prediction time are respectively used as the center to expand the tolerance margin to both sides, and the first dynamic time window and the second dynamic time window are generated accordingly. Within the generated first dynamic time window, extract the extreme points that are confirmed as valid arrival times and obtain the first absolute propagation time. Within the generated second dynamic time window, extract the extreme points that are confirmed as valid arrival times and obtain the second absolute propagation time.

4. The self-calibration method for a magnetostrictive displacement sensor according to claim 3, characterized in that, The extreme points that are confirmed as valid arrival times within the first dynamic time window are extracted as the first absolute propagation time, and the extreme points that are confirmed as valid arrival times within the second dynamic time window are extracted as the second absolute propagation time. This process specifically includes the following steps: The signal acquisition channel is enabled by outputting a valid enable level only within the time interval of the first dynamic time window and the second dynamic time window using a hardware timer, and an invalid level is forcibly output outside the time interval to physically cut off and shield non-target interference signals. Within the time interval of activating the signal acquisition channel, the absolute amplitude, zero-crossing slope, and continuous positive pulse width characteristics of the received induced voltage signal are simultaneously verified. When the characteristics of the three dimensions of absolute amplitude, zero-crossing slope, and continuous positive pulse width all conform to the original physical properties of the target torsional stress wave, the current extreme point is confirmed as the effective arrival time. The effective arrival times confirmed in the first dynamic time window and the second dynamic time window are respectively used as the first absolute propagation time and the second absolute propagation time.

5. The self-calibration method for a magnetostrictive displacement sensor according to claim 1, characterized in that, After obtaining the first absolute propagation time and after a physical delay time, an excitation pulse current is applied to the second electromagnetic coil (6) and a pulse current is synchronously applied to the waveguide wire (1), specifically including the following steps: After the excitation pulse current is applied to the first electromagnetic coil (5), the internal hardware delay timer is started and the physical delay time is inserted, which is strictly greater than the quotient obtained by dividing the maximum physical total length of the waveguide wire (1) by the minimum expected wave velocity under extreme low temperature conditions. The excitation action on the second electromagnetic coil (6) is forcibly suspended during the physical delay time, and after the physical delay time has elapsed, the excitation pulse current is resumed to the second electromagnetic coil (6) and the pulse current is synchronously applied to the waveguide wire (1).

6. The self-calibration method for a magnetostrictive displacement sensor according to claim 1, characterized in that, The flight time difference is obtained by subtracting the first absolute propagation time and the second absolute propagation time, and the measured wave velocity is calculated by combining it with the pre-stored calibration interval. The specific steps include: The flight time difference is obtained by subtracting the first absolute propagation time and the second absolute propagation time and performing an absolute value operation. If the flight time difference is less than the effective time difference lower limit threshold, which is a threshold determined based on the calibration interval and the theoretical maximum wave speed limit, then the currently captured data is forcibly discarded and the wave speed calculation is exited; otherwise, the pre-stored calibration interval is divided by the measured flight time difference to calculate the measured wave speed.

7. The self-calibration method for a magnetostrictive displacement sensor according to claim 1, characterized in that, The calibration compensation coefficient is obtained by calculating the ratio of the measured wave velocity to the preset reference wave velocity. The preset reference wave velocity is then corrected using the calibration compensation coefficient. After the convergence condition is met—that the difference between the calibration compensation coefficients calculated in two consecutive rounds is less than the preset error convergence threshold used to characterize the convergence of wave velocity determination—the value is overwritten into the memory. The specific steps include: When it is determined that the calculated calibration compensation coefficient is within the preset reasonable safety boundary, the calibration compensation coefficient is multiplied by the preset reference wave velocity to obtain the new wave velocity after calibration. The generated new calibrated wave velocity is used as a new benchmark to trigger the underlying self-calibration closed loop again. When the difference between the calibration compensation coefficients obtained in two consecutive rounds of calculation is less than the preset error convergence threshold used to characterize the convergence of wave velocity determination, it is determined that the convergence condition is met. After the convergence condition is met, the calibrated new wave velocity is replaced and written to the designated mapping address of the non-volatile memory chip via the communication bus, and then overwritten into the memory.

8. A self-calibration device for a magnetostrictive displacement sensor, characterized in that, The self-calibration method for a magnetostrictive displacement sensor according to any one of claims 1-7 includes: Waveguide assembly, which contains a waveguide wire (1). The dual electromagnetic coil assembly includes a first electromagnetic coil (5) and a second electromagnetic coil (6). The first electromagnetic coil (5) and the second electromagnetic coil (6) are coaxially sleeved on the outside of the waveguide wire assembly, and there is a preset calibration distance between them. Waveguide sheet (7) is installed at one end of the waveguide wire assembly; A detector coil (8) is positioned at the corresponding position of the waveguide plate (7); The coil excitation circuit (12) is connected to the first electromagnetic coil (5) and the second electromagnetic coil (6) respectively; The pulse excitation circuit (9) is connected to the waveguide wire assembly; The input terminal of the signal processing module (10) is connected to the output terminal of the detector coil (8); The calculation and storage module (11) is connected to the coil excitation circuit (12), the pulse excitation circuit (9) and the signal processing module (10) respectively, and is used to issue trigger commands, extract time windows, calculate wave velocity and overwrite the calibrated new wave velocity to the internal storage unit.

9. A self-calibration device for a magnetostrictive displacement sensor according to claim 8, characterized in that, The specific assembly structure of the first electromagnetic coil (5) and the second electromagnetic coil (6) includes: The waveguide wire assembly is covered from the inside out with an insulating sleeve (2), a shielding layer (3) and a protective tube (4). The outer surface of the protective tube (4) is fitted with a position magnet (13); The first electromagnetic coil (5) and the second electromagnetic coil (6) adopt a frameless self-adhesive winding structure and are coaxially installed on the outside of the insulating sleeve (2).

10. A self-calibration device for a magnetostrictive displacement sensor according to claim 8, characterized in that, The computing and storage module (11) has an integrated hardware timer for constructing time window signal gating and filtering; The control output terminal of the hardware timer is physically connected to the sampling enable terminal of the A / D conversion circuit inside the signal processing module (10).

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