A system and method for accelerated life testing of displacement sensors under multiple operating conditions and with full parameters

Abstract

This invention discloses a multi-parameter accelerated life testing system and method for displacement sensors, belonging to the field of sensor reliability testing technology. The displacement sensor under test is mounted on a reciprocating motion stage that penetrates an environmental chamber, simultaneously subjected to temperature, humidity, vibration, and stroke reciprocating stress. The reference displacement measuring device is divided into a passive follower part that travels with the test piece and an active tracking part externally located in a controlled temperature zone. The reciprocating motion stage contacts a physical fixed point made of a material with near-zero thermal expansion in a predetermined cycle. Based on this, the reference drift is separated and subtracted within each cycle, and then the pure degradation component of the test piece is quantified using the corrected reference. This invention solves the problem of unreliable separation of degradation caused by the degradation of the test piece itself and the reference drift, and can be used for full life-cycle micro-change tracking, durability, and failure threshold assessment of displacement sensors.

Description

Technical Field

[0001] This invention relates to the field of sensor reliability testing and evaluation technology, specifically to a comprehensive testing system and method for displacement sensors to perform accelerated aging tests, synchronous monitoring of all parameters, and failure analysis under simulated real service environments. Background Technology

[0002] Displacement sensors, as core components for precision measurement and closed-loop control, are widely used in automotive electronics, industrial automation, robotics, rail transportation, and aerospace. In these applications, displacement sensors often perform critical functions such as position feedback, travel limitation, and deformation monitoring. Their reliability and stability during long-term service directly determine the safety and control accuracy of the entire system. If a displacement sensor experiences performance drift exceeding permissible limits or complete failure during service, it can lead to anything from decreased control accuracy and fluctuations in product yield to serious safety incidents. Therefore, accelerated life testing is typically required during the R&D and mass production stages of sensor products to assess their durability and determine their failure thresholds under various stress conditions. This provides a basis for product design improvements, selection, and quality control.

[0003] The basic idea of ​​accelerated life testing is to accelerate the development of the internal failure mechanism of the test object by applying stress higher than the normal service level, thereby inducing failures equivalent to long-term normal service within a shorter test time, and thus obtaining the life and reliability information of the test object within an acceptable period. To ensure that the results of accelerated testing accurately reflect the actual service life, the type of stress and stress coupling relationship applied in the test should be as close as possible to the actual service environment of the test object.

[0004] Existing displacement sensor life testing equipment is mostly based on a single environmental variable. For example, one type of equipment is a simple mechanical reciprocating wear test machine, which only applies repeated mechanical reciprocating motion to the displacement sensor under test to assess its mechanical wear resistance; another type of equipment is a separate temperature and humidity aging chamber or vibration test bench, which only applies temperature, humidity, or vibration stress to the test object. Such test schemes based on a single stress variable have several engineering limitations.

[0005] First, in the actual service environment of the displacement sensor under test, high temperature, low temperature, humidity, vibration, and mechanical reciprocating motion often act on the sensor simultaneously, and various stresses interact and couple with each other. For example, temperature changes alter the mechanical properties of materials and fit clearances, thus affecting the wear rate during mechanical reciprocating motion; humidity changes the electrical properties of the insulating medium and accelerates the deterioration of the sealing structure under vibration conditions. Testing a single stress variable cannot induce the accelerated failure modes unique to multi-factor coupling conditions, leading to discrepancies between the experimental life data and the actual service life, and even conclusions contrary to reality.

[0006] Secondly, traditional equipment often only records a few terminal results such as the on / off state of the displacement sensor being measured or the output voltage at the end, lacking the ability to synchronously acquire high-frequency data on key intermediate variables that characterize the performance degradation process, such as full-stroke linearity, dynamic response, insulation impedance, zero-point drift, and hysteresis error. Since performance degradation is usually a gradual process, recording only terminal results will miss a large amount of intermediate information reflecting early degradation, making it difficult for R&D personnel to capture performance inflection points and judge the development trend of degradation, thus creating a blind spot in the monitoring of the gradual performance change process.

[0007] Third, existing technologies also include integrated testing systems that connect multiple sensors, such as displacement sensors, temperature sensors, and force sensors, to an industrial control computer via a data acquisition card, as well as testing systems that perform in-situ measurements on the specimen while applying a load spectrum. However, it should be noted that in such integrated testing systems, the displacement sensor is always treated as a reliable measuring tool to measure the displacement or deformation of other test specimens (e.g., fatigue specimens, material samples). The displacement sensor itself is assumed to be non-degradable, and its output is assumed to be a reliable true value. In other words, in existing integrated testing systems, the displacement sensor plays the role of a "measuring instrument."

[0008] The fundamental difference lies in the accelerated life test, where the displacement sensor itself is the test object. The sensor is undergoing continuous degradation, rendering its output unreliable and unsuitable as a measure of its degradation. Introducing an additional reference displacement measurement device for comparison presents a technical challenge that existing integrated testing systems have never faced: this additional device, also immersed in a multi-stress field of temperature, humidity, and vibration, will experience zero-point drift, scaling factor drift, and accuracy degradation. Furthermore, in accelerated life tests that can last hundreds or even thousands of hours, the drift of the reference device may be on the same order of magnitude as the actual degradation of the test object. This makes it difficult to reliably separate the actual degradation of the test object from the drift of the reference device itself and transient environmental disturbances when the reference itself is also drifting.

[0009] It is evident that existing testing devices are insufficient for quantitatively tracking and mechanistic analysis of the micro-change process of displacement sensors throughout their entire lifecycle, from initial performance to complete failure, under conditions simulating real multi-field coupling environments. A new testing and analysis system is urgently needed to address this issue. Summary of the Invention

[0010] To address the aforementioned shortcomings of existing technologies, the technical problem to be solved by this invention is as follows: In accelerated life tests with simultaneous multi-stress loading, the displacement sensor under test is itself a degradation object, and its output is unreliable. The benchmark measuring device used for comparison is also immersed in the stress field and has its own drift on the same order of magnitude as the degradation under test. This makes it impossible to reliably separate the actual degradation of the test piece from the benchmark's own drift and transient environmental interference, and thus it is impossible to quantitatively track and analyze the mechanism of its micro-change process throughout its entire life cycle.

[0011] To address the aforementioned core technical issues, this invention further needs to resolve the following interrelated specific problems: First, how to maintain the reliability of the introduced reference in a multi-stress field, i.e., reduce the environmental sensitivity of the reference itself; second, how to continuously distinguish reference drift from measured degradation during long-term testing without relying on the long-term absolute accuracy of the reference; third, how to achieve synchronous acquisition of intermediate characterization parameters such as full-stroke linearity and insulation impedance without interrupting multi-stress loading; and fourth, how to transform the separated degradation information into clear failure attribution conclusions.

[0012] To address the aforementioned technical problems, this invention provides a multi-parameter, multi-condition accelerated life testing system for displacement sensors, comprising a multi-stress loading unit, a common-stroke comparison measurement unit, an in-situ fixed-point recalibration unit, a degradation-drift separation calculation unit, a parameter synchronous acquisition unit, and a failure determination and documentation unit.

[0013] The displacement sensor under test is mounted on a reciprocating motion table that runs through the environmental chamber. A multi-stress loading unit simultaneously applies temperature, humidity, vibration, and mechanical stroke reciprocating stresses to it to simulate the multi-field coupled stresses that the displacement sensor under test would experience in a real service environment.

[0014] The common stroke comparison measurement unit includes a reference displacement measuring device mechanically connected in parallel with the displacement sensor under test on the same reciprocating motion stage and subjected to the same stroke displacement. The reference displacement measuring device is divided into a passive follower part fixed to the reciprocating motion stage and subjected to various stresses along with the measured object, and an active tracer part arranged in a temperature-controlled zone outside the environmental chamber and connected to the passive follower part via a through-wall connector. Through this division, the reference side immersed in the stress field is only a passive element whose performance hardly degrades, while the active element, which is susceptible to drift due to temperature and other stresses, is isolated in the temperature-controlled zone.

[0015] The in-situ fixed-point recalibration unit includes rigid physical fixed points made of near-zero thermal expansion material, located at at least two extreme positions of the reciprocating motion stage's stroke, and control components that control the reciprocating motion stage to contact the physical fixed points in a predetermined cycle and simultaneously lock the measured reading and the reference reading at the moment of contact. Because the physical fixed points are made of near-zero thermal expansion material, their corresponding absolute positions hardly change with stress within the test temperature range, and can serve as an absolute position reference for each cycle.

[0016] The degradation-drift separation calculation unit uses the absolute position corresponding to the physical fixed point as a common reference. In each cycle, it determines and subtracts the drift of the reference by the offset of the reference reading relative to the physical fixed point. Then, it compares the reference reading after deducting the drift with the full-stroke reading of the test piece to obtain the pure degradation component of the test piece.

[0017] The parameter synchronous acquisition unit synchronously acquires the full-stroke output, reference readings, and environmental stresses of the test component at each stroke position; the failure judgment and filing unit sets thresholds for pure degradation components according to working conditions, identifies performance inflection points, classifies failure modes, and writes them into the full life cycle digital archive.

[0018] As a preferred embodiment, the passive follower can be a reflective target mirror of a laser interferometer or a grating scale fixed to a zero-expansion substrate; the near-zero thermal expansion material can be Invar, microcrystalline glass, or zero-expansion ceramic; the common stroke comparison measurement unit can also include a second reference measurement device with a different principle from the reference displacement measurement device to achieve redundant voting; the degradation-drift separation calculation unit can also use the reading difference between forward and reverse passes through the same position to separate the backlash error degradation component; the parameter synchronous acquisition unit can also include a relay matrix to time-division switch the acquisition of insulation impedance within a mechanical static window.

[0019] The beneficial effects of this invention are as follows: First, this invention splits the reference displacement measuring device into a passive follower part and an active tracer part. This ensures that the reference side immersed in the stress field consists only of passive components whose performance hardly degrades, while the easily drifting active components are isolated in a controlled temperature region. Thus, the environmental immunity of the reference comes from the structural layout, rather than simply relying on improving the accuracy level of the reference device itself. Accordingly, in a real-world service equivalent environment with multi-stress coupling, the self-drift introduced by the reference side is significantly suppressed.

[0020] Secondly, this invention establishes a physical reference point for the near-zero thermal expansion material at the limit position of the travel and controls the reciprocating stage to perform in-situ recalibration at this reference point in each cycle. This allows the system to obtain an absolute position reference that is almost unaffected by stress changes within each test cycle. Using this reference, the reference drift itself is extracted and subtracted as an observable, thus decoupling the reference drift from the actual degradation of the test piece in principle. This approach does not rely on the long-term absolute accuracy of the reference, and therefore can maintain effective separation during accelerated testing lasting hundreds or even thousands of hours, overcoming the difficulty of distinguishing between reference drift and measured degradation being of the same order of magnitude.

[0021] Third, by synchronously acquiring all parameters and switching the insulation impedance to time-division mode, this invention can synchronously track intermediate characterization parameters such as linearity of the entire stroke, dynamic response, insulation impedance, zero drift, and hysteresis error without interrupting multi-stress loading. This eliminates the monitoring blind spots caused by traditional equipment that only records terminal results and can capture early performance degradation characteristics.

[0022] Fourth, by binding degradation component characteristics to specific physical quantities and classifying them according to the correspondence between degradation component characteristics and failure modes, this invention can transform test data into failure attribution conclusions, providing engineering guidance for product reliability optimization.

[0023] It should be noted that the above-mentioned beneficial effects are derived from the working principle of the technical solution of the present invention. Those skilled in the art can implement the present invention and verify the above-mentioned effects based on the structure and method described in this specification. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the system of the present invention; Figure 2 This is a schematic diagram showing the arrangement of the passive follower part and the active tracing part of the reference device in the common stroke comparison measurement unit; Figure 3 A schematic diagram of setting physical fixed points at the limit positions of the reciprocating stroke for the in-situ fixed-point recalibration unit; Figure 4 This is a flowchart of the operation of the degradation-drift separation operation unit within a single loop; Figure 5 This is a flowchart illustrating the overall process of the testing and analysis method of this invention.

[0025] In the diagram: 1—Environmental chamber; 2—Reciprocating motion table; 3—Stroke drive mechanism; 4—Measured displacement sensor; 5—Reference displacement measuring device; 51—Passive follow-up part; 52—Active tracing part; 53—Through-wall connector; 6—Physical fixed point; 7—Parameter synchronous acquisition unit; 71—Relay matrix; 8—Degradation-drift separation calculation unit; 9—Failure judgment and filing unit. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Equivalent substitutions and improvements made without departing from the concept of this invention should be covered within the scope of protection of this invention.

[0027] Example 1: System Overall Structure like Figure 1 As shown, the displacement sensor full-parameter multi-condition accelerated life test system provided in this embodiment includes an environmental chamber 1, a reciprocating motion stage 2 that passes through the environmental chamber 1, a stroke drive mechanism 3 that drives the reciprocating motion stage 2 to reciprocate, a displacement sensor under test 4 installed on the reciprocating motion stage 2, a reference displacement measuring device 5 mechanically connected in parallel with the displacement sensor under test 4, a physical fixed point 6 set at the stroke limit position, a parameter synchronous acquisition unit 7, a degradation-drift separation calculation unit 8, and a failure judgment and filing unit 9.

[0028] The environmental chamber 1 integrates a temperature control device, a humidity control device, and a vibration excitation stage. These three components together form a multi-stress loading unit to simultaneously apply temperature stress, humidity stress, and vibration stress to the displacement sensor 4 located in the working section within the chamber. In one specific embodiment, the temperature stress is applied within a high-low temperature cycle ranging from -40 degrees Celsius to +125 degrees Celsius; the humidity stress is applied within a relative humidity range of 85% or higher; and the vibration stress is random vibration or sinusoidal sweep vibration with a predetermined frequency. The type, magnitude, and cycle mode of these stresses can be set and adjusted according to the actual service environment of the displacement sensor under test.

[0029] The stroke drive mechanism 3 uses either a servo motor to drive a ball screw or a voice coil motor for direct drive. This drives the reciprocating motion table 2 to perform reciprocating linear motion within a set stroke range, thereby applying mechanical reciprocating stress to the displacement sensor 4, which moves with the reciprocating motion table 2, simulating the wear and tear of the displacement sensor 4 during actual service. The measuring rod or mover of the displacement sensor 4 is fixedly connected to the reciprocating motion table 2, and its output signal is led out via a lead wire and connected to the parameter synchronization acquisition unit 7.

[0030] To prevent thermal drift, wear, and clearance of the stroke drive mechanism 3 from being mixed into the measured signal, the body of the stroke drive mechanism 3 is preferably located outside the environmental chamber 1, or it is insulated and vibration-damped, and connected to the reciprocating motion table 2 only through a transmission link penetrating the chamber wall. A low-friction, temperature-resistant, and sealing guide structure is provided between the reciprocating motion table 2 and the chamber wall of the environmental chamber 1, ensuring that the reciprocating motion table 2 maintains its straightness and positioning accuracy while penetrating the chamber wall. The degradation-drift separation calculation unit 8 and the failure judgment and filing unit 9 can be implemented by an industrial control computer and the calculation program running on it, or by an embedded controller with corresponding computing capabilities.

[0031] Example 2: Common Stroke Comparison Measurement Unit and its Reference Split Arrangement like Figure 2 As shown, the reference displacement measuring device 5 and the measured displacement sensor 4 are mechanically connected in parallel on the same reciprocating motion table 2, so that the two experience the same stroke displacement at every moment, thereby ensuring the homogeneity of the comparison and avoiding systematic errors introduced by the inconsistency of their strokes.

[0032] The reference displacement measuring device 5 is divided into a passive follower part 51 and an active tracking part 52. In a first embodiment, the reference displacement measuring device 5 employs a laser interferometer. Its passive follower part 51 is a reflecting target mirror fixed to the reciprocating stage 2. This reflecting target mirror is a passive optical element, and its geometric and optical properties hardly degrade under the influence of temperature, humidity, and vibration stress. Its active tracking part 52 consists of a laser source, a beam splitter, and interference fringe counting electronics, arranged in a controlled temperature zone outside the environmental chamber 1, for example, in a thermostatic enclosure where temperature fluctuations are controlled within ±0.1 degrees Celsius. The passive follower part 51 and the active tracking part 52 are connected via an optical path through-wall channel, which serves as a through-wall connector 53. The laser beam enters the environmental chamber 1 through this optical path through-wall channel, irradiates the reflecting target mirror moving with the reciprocating stage 2, and returns to the active tracking part 52. The reference displacement reading is obtained by counting the interference fringes. Thus, the reference side immersed in the multi-stress field is only a passive reflective target mirror that is almost non-degraded, while the active components such as the laser source, which is susceptible to frequency drift due to temperature, and the electronics, which are susceptible to counting errors due to temperature, are all isolated within the controlled temperature region.

[0033] In the second embodiment, the reference displacement measuring device 5 employs a grating measurement system. Its passive follower part 51 is a grating scale fixed to a near-zero expansion substrate (e.g., a microcrystalline glass substrate), which moves with the reciprocating stage 2. Its active tracking part 52 is a grating reading head and its signal processing circuit, arranged within the controlled temperature zone, and maintains a reading relationship with the grating scale inside the chamber via a flexible through-wall connector 53. This embodiment also achieves a split layout where passive components are placed in a stress field and active components are isolated within the controlled temperature zone.

[0034] As a preferred embodiment, the common-stroke comparison measurement unit may further include a second reference measurement device with a different principle from the reference displacement measurement device 5. For example, while using a laser interferometric reference, a set of capacitance micrometer references may be set in parallel. Since the failure mechanisms and drift laws of the laser interferometric principle and the capacitance micrometer principle are different under the influence of temperature, humidity, and vibration, when the offsets of the two sets of references relative to the physical fixed point 6 show significant differences, the degradation-drift separation calculation unit 8 can identify and vote on the reference measurement device that has experienced abnormal drift, thereby further improving the reliability of the reference side and avoiding undetected drift of a single reference that could contaminate the separation results.

[0035] Example 3: In-situ Fixed-point Recalibration Unit like Figure 3 As shown, at the two extreme positions of the reciprocating motion table 2, rigid physical anchor points 6 made of near-zero thermal expansion material are respectively set. The near-zero thermal expansion material can be Invar, microcrystalline glass, or zero-expansion ceramic. These materials have extremely low coefficients of linear expansion, making the change in the absolute position corresponding to the physical anchor point 6 negligible throughout the entire test temperature range. The absolute position corresponding to the physical anchor point 6 is uniquely determined by its structural dimensions. It can be calibrated once before the test using a higher-level metrological reference (e.g., a coordinate measuring machine), and the calibration result is solidified as a known constant, denoted as the absolute position of the left extreme position and the absolute position of the right extreme position.

[0036] The control unit controls the stroke drive mechanism 3, causing the reciprocating motion table 2 to contact the physical fixed point 6 once in each reciprocating cycle or every predetermined number of cycles (e.g., every 100 cycles). The physical fixed point 6 is preferably equipped with a rigid limiting surface and supplemented with a contact sensing element, such as a high-stiffness force plate or an electrical contact switch, to determine whether the reciprocating motion table 2 has truly contacted the target point. At the instant the contact is determined, the control unit triggers the parameter synchronization acquisition unit 7, simultaneously latching the readings of the displacement sensor 4 and the reference displacement measuring device 5 at that moment.

[0037] Since the absolute position of the reciprocating stage 2 at the instant of contact is equal to the calibration value of the physical fixed point 6, and this absolute position hardly changes with stress variations such as temperature, humidity, and vibration, the deviation between the measured reading and the reference reading at that moment relative to this known absolute position reflects the zero-point offset of the measured displacement sensor 4 and the reference displacement measuring device 5 relative to their initial calibration state under the current cycle and current stress state, respectively. Furthermore, since the physical fixed point 6 is set at both extreme positions, the system can obtain readings at two known absolute positions within one reciprocating cycle. The difference between the two can be used not only to calibrate the zero-point drift but also to calibrate the scale factor drift of the measured displacement sensor 4 and the reference displacement measuring device 5, i.e., the sensitivity drift, thereby achieving in-situ dual calibration of the zero point and the scale factor.

[0038] Example 4: Degradation-Drift Separation Operation like Figure 4 As shown, the degradation-drift separation operation unit 8 performs the following operations in each cycle. For ease of explanation, the known absolute position of a certain extreme position physical fixed point 6 is denoted as the reference position constant L0, the reference reading latched at the moment the cycle touches the physical fixed point is denoted as R_ref, the measured reading is denoted as R_dut, and the sampling positions of the measured displacement sensor 4 at each point along the entire stroke are denoted as position i.

[0039] The first step is to calculate the reference drift, which is obtained by subtracting the known absolute position of the physical fixed point from the reference reading at the moment of contact, resulting in the reference drift Δ_ref, which is equal to R_ref minus L0. This drift is the drift of the reference displacement measuring device 5 relative to its initial calibration state under the current stress state. Since only the passive servo part is immersed in the stress field on the reference side, this drift is usually small, but its accumulation during long-term testing is still not negligible. This step extracts it separately as an observable measurement, which is the key to achieving separation.

[0040] The second step involves comparing the readings R_dut(i) of the measured displacement sensor 4 at each sampling position i throughout the entire cycle with the baseline reading after deducting its own drift as a reliable comparison quantity. This yields the pure degradation component E(i) of the measured displacement sensor 4 at position i, which is equal to R_dut(i) minus the synchronous reading R_ref(i) of the baseline at position i (within parentheses) minus Δ_ref. In this way, the baseline drift Δ_ref is subtracted during the calculation, ensuring that the obtained pure degradation component E(i) only reflects the true degradation of the measured displacement sensor 4 itself, thus achieving decoupling between the baseline drift and the measured degradation.

[0041] The third step involves extracting various characteristic quantities representing degradation based on the pure degradation components E(i) at each position throughout the entire stroke. These include, but are not limited to: full-stroke linearity deviation (the ratio of the maximum deviation of the pure degradation component across the entire stroke to the full-scale range); zero-point drift (the pure degradation component at the zero point of the stroke); and sensitivity drift (the change in the scaling factor calculated from the difference between the pure degradation components at the two limiting points). For transient environmental interference, since the contact at the physical fixed point occurs within the mechanical static window of the stroke reversal, and the sampling is taken from the steady-state sampling window, and correlation judgment and rejection are performed in conjunction with synchronously recorded temperature, humidity, and vibration, transient interference is not mistakenly included in the degradation components.

[0042] As a preferred embodiment, the degradation-drift separation calculation unit 8 can also use the difference between the measured reading when the reciprocating motion stage 2 passes position i in the forward direction and the measured reading when it passes the same position i in the reverse direction to separate the backlash error degradation component related to the motion direction. This backlash error degradation component can be used to characterize specific direction-related failures such as loosening of the internal mechanical transmission of the displacement sensor 4 and increased hysteresis, without relying on an external absolute reference.

[0043] It should be noted that the specific values ​​of each physical quantity, the number of sampling positions, the interval of contact cycles, and other parameters in the above calculations can be determined by those skilled in the art based on the range, accuracy requirements, and test cycle of the object being measured. This invention does not impose any limitations on these parameters. The above calculation relationships are derived based on geometric positional relationships and measurement principles, and those skilled in the art can implement them through programming according to the description in this specification.

[0044] Example 5: Synchronous Parameter Acquisition and Time-Division Interconnection of Insulation Impedance The parameter synchronous acquisition unit 7 includes a multi-channel data acquisition card and a relay matrix 71. It is configured to synchronously acquire the full-stroke output, reference reading, temperature, humidity, and vibration stress of the displacement sensor 4 under test at each stroke position of the reciprocating motion table 2 at a predetermined sampling rate, and ensure that each channel is aligned in time so that each quantity can correspond one by one during subsequent calculations.

[0045] For parameters like insulation impedance, which require an independent test voltage and cannot coexist with the normal operating signal channel, the relay matrix 71 is configured to switch channels within the mechanical static window during the stroke reversal of the reciprocating stage 2. This mechanical static window refers to the time period when the reciprocating stage 2 moves to near the end of its stroke, its instantaneous speed approaches zero, and its mechanical stress is relatively stable. Within this window, the relay matrix 71 switches the measurement circuit of the displacement sensor 4 under test from the operating signal channel to the insulation impedance test channel. The insulation impedance test channel applies a specified test voltage to the displacement sensor 4 and measures its insulation impedance. After completing the insulation impedance acquisition, the relay matrix 71 switches the measurement circuit back to the operating signal channel, resuming normal displacement signal acquisition.

[0046] By employing the aforementioned time-division switching method, on the one hand, the test voltage applied during insulation impedance testing will not contaminate the operating signal during displacement signal acquisition; on the other hand, the entire switching and acquisition process is completed within the mechanical static window, without interrupting the application of temperature, humidity, and vibration stress, nor stopping the mechanical reciprocating motion, thus avoiding the drawbacks of traditional pause-based measurements that require interrupting the test and disrupting stress continuity. The acquired insulation impedance, along with the temperature, humidity, and stress records at the time, is included as one of the pure degradation components in subsequent failure mode classification.

[0047] Example 6: Failure Determination and Full Lifecycle Record Building The failure determination and documentation unit 9 sets a determination threshold for each pure degradation component output by the degradation-drift separation calculation unit 8. This threshold is dynamically mapped to the combination of operating conditions such as temperature, humidity, and vibration stress. That is, under different stress combinations, different determination thresholds are applied to the same degradation component to reflect the different tolerance limits of the same degradation component under different operating conditions. The identification of performance inflection points uses robust criteria: either the pure degradation component continuously exceeds a predetermined number of cycles (e.g., fifty consecutive cycles) or its rate of change (i.e., the degradation increment per unit cycle) exceeds a set limit. This avoids misjudgments caused by single, occasional exceedances.

[0048] The failure determination and filing unit 9 stores the correspondence between pure degradation component characteristics and failure modes, serving as the basis for classifying failure modes. The table below provides an exemplary configuration of this correspondence, which can be supplemented and adjusted by those skilled in the art according to the specific type, structure, and failure physics of the displacement sensor under test.

[0049] ; The failure assessment and documentation unit 9 writes the stress conditions of each cycle, all pure degradation components, identified performance inflection points, and categorized failure modes into a time-series digital archive, forming a traceable record of the entire process of the displacement sensor 4 from initial performance to complete failure. Based on this digital archive, the system can output the failure threshold and durability assessment conclusions of the displacement sensor 4 under various stress conditions, and can trace the entire failure development process by comparing it with the degradation curve, providing engineering guidance for product reliability optimization and design improvement.

[0050] Example 7: Test and Analysis Method Flow like Figure 5 As shown, the accelerated life test method for displacement sensors using the above system includes the following steps.

[0051] Step S1, Installation and Initialization. The displacement sensor 4 to be measured and the reference displacement measuring device 5 are mechanically connected in parallel on the reciprocating motion table 2, and the active traceability part 52 of the reference displacement measuring device 5 is placed externally in the controlled temperature zone of the environmental chamber 1; the absolute position of each physical fixed point 6 is calibrated with a higher metrological level reference, and the calibration results are solidified as known constants; the initial performance baseline of the displacement sensor 4 throughout its entire stroke is recorded in the initial state.

[0052] Step S2, apply multiple stresses. Start the multi-stress loading unit to simultaneously apply temperature, humidity, vibration and mechanical stroke reciprocating stresses to the displacement sensor 4 under test, and drive the reciprocating motion table 2 to reciprocate by the stroke drive mechanism 3.

[0053] Step S3, in-situ recalibration latch. In a predetermined cycle, the control unit controls the reciprocating motion table 2 to contact the physical fixed point 6, and simultaneously latches the reading of the measured displacement sensor 4 and the reading of the reference displacement measuring device 5 at the moment of contact.

[0054] Step S4: Separate calculation and full parameter acquisition. Using the known absolute position of physical fixed point 6 as a common reference, calculate and subtract the reference drift itself, and then compare the reference reading after drift subtraction with the full stroke reading of the displacement sensor 4 under test to obtain the pure degenerate component of the displacement sensor 4 under test; and within the mechanical static window of stroke reversal, the insulation impedance of the displacement sensor 4 under test is acquired by the relay matrix 71 in a time-division switching manner.

[0055] Step S5, Failure Determination and Attribution. Each pure degradation component is assessed for exceeding limits and its rate of change based on the dynamic threshold of the operating condition to identify performance inflection points. When the failure criteria are met, the failure mode is classified according to the correspondence between the characteristics of the pure degradation component and the failure mode.

[0056] Step S6, Record Building and Evaluation. Write the stress conditions, pure degradation components, performance inflection points, and failure modes of each cycle into the full life cycle digital file until the displacement sensor 4 under test reaches the preset failure threshold; end the test and output the durability and failure threshold evaluation conclusions of the displacement sensor 4 under test.

[0057] Other implementation methods and variations The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. For example, the types and application ranges of the multiple stresses can be increased, decreased, or adjusted according to the actual service environment of the object being measured, and are not limited to a combination of temperature, humidity, vibration, and stroke reciprocation; the reference displacement measuring device can employ measurement principles where other passive measuring elements and active signal processing stages can be spatially separated, and is not limited to laser interferometry and grating measurement; the number of physical fixed points can be more than two to provide denser gauge length information at multiple positions along the stroke, thereby improving the calibration accuracy of the scale factor drift distribution along the stroke; the degradation-drift separation calculation unit and failure determination unit can be implemented by an industrial control computer and its calculation program, or by an embedded controller or dedicated calculation circuit. All the above modifications and improvements should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A multi-parameter, multi-condition accelerated life testing system for a displacement sensor, comprising a multi-stress loading unit that simultaneously applies temperature, humidity, vibration, and mechanical stroke reciprocating stress to the displacement sensor under test, wherein the displacement sensor under test is mounted on a reciprocating motion stage penetrating an environmental chamber, characterized in that, The system further includes: a common stroke comparison measurement unit, comprising a reference displacement measuring device mechanically connected in parallel with the displacement sensor under test on the same reciprocating motion stage and subjected to the same stroke displacement; the reference displacement measuring device is divided into a passive follower part fixed to the reciprocating motion stage and subjected to the stresses along with the displacement sensor under test, and an active traceability part arranged in the temperature-controlled zone outside the environmental chamber and connected to the passive follower part via a through-wall connector; and an in-situ fixed-point recalibration unit, comprising a rigid physical fixed point made of near-zero thermal expansion material set at at least two extreme positions of the stroke of the reciprocating motion stage, and controlling the reciprocating motion stage to contact the physical fixed point in a predetermined cycle and synchronously latching the reading of the displacement sensor under test at the contact moment. The system includes: a control unit for reference readings; a degradation-drift separation calculation unit configured to use the absolute position corresponding to the physical fixed point as a common reference, determine and subtract the reference drift from the offset of the reference reading relative to the physical fixed point in each cycle, and then compare the reference reading after deducting the drift with the full-stroke reading of the displacement sensor under test to obtain the pure degradation component of the displacement sensor under test; a parameter synchronous acquisition unit configured to synchronously acquire the full-stroke output of the displacement sensor under test, the reference reading, and the temperature, humidity, and vibration stress at each stroke position of the reciprocating motion table; and a failure judgment and filing unit configured to set a threshold for the pure degradation component according to the working conditions to identify performance inflection points, classify failure modes, and write them into a full life cycle digital file.

2. The system according to claim 1, characterized in that, The passive follower part is a reflective target mirror of a laser interferometer or a grating scale fixed to a zero-expansion substrate. The active tracing part is a corresponding laser source and interference counting electronics or grating reading head signal processing circuit. The through-wall connector is an optical path through-wall channel.

3. The system according to claim 1, characterized in that, The near-zero thermal expansion material is Invar, microcrystalline glass, or zero-expansion ceramic, and the absolute position corresponding to the physical fixed point is uniquely determined by the structural dimensions.

4. The system according to claim 1, characterized in that, The common stroke comparison measurement unit also includes a second reference measurement device that is different in principle from the reference displacement measurement device. The degradation-drift separation calculation unit is further configured to identify and vote on the reference measurement device that has drifted based on the difference between the offset of the two reference measurement devices relative to the physical fixed point.

5. The system according to claim 1, characterized in that, The degradation-drift separation calculation unit is further configured to use the difference between the readings of the displacement sensor being measured when the reciprocating motion table passes through the same stroke position in the forward and reverse directions to separate the back-stroke error degradation component of the displacement sensor being measured.

6. The system according to claim 1, characterized in that, The parameter synchronous acquisition unit includes a relay matrix. The relay matrix is ​​configured to switch the measurement circuit of the displacement sensor under test from the working signal channel to the insulation impedance test channel in a time-division manner within the mechanical static window of the reciprocating motion table stroke reversal, and then switch back to the working signal channel after completing the insulation impedance acquisition.

7. The system according to claim 1, characterized in that, The failure determination and the threshold set by the filing unit are dynamically mapped with the combination of operating conditions such as temperature, humidity and vibration stress, and the performance inflection point is determined by the pure degradation component continuously exceeding the predetermined number of cycles or its rate of change exceeding the limit.

8. The system according to claim 1 or 7, characterized in that, The failure determination and filing unit stores a correspondence table between pure degradation component characteristics and failure modes. The correspondence table includes at least the following: monotonic degradation of linearity throughout the entire stroke corresponds to wear of sensitive components; decrease in insulation resistance accompanied by humidity stress corresponds to sealing failure; and a sudden increase in retrace error corresponds to mechanical loosening.

9. A method for accelerated life testing of a displacement sensor using the system described in claim 1, characterized in that, include: Temperature, humidity, vibration, and mechanical stroke reciprocating stress are simultaneously applied to the displacement sensor being measured, which is mounted on a reciprocating motion table. A reference displacement measuring device is mechanically connected in parallel on the reciprocating motion table, and the active traceability part of the device is externally placed in the temperature-controlled zone of an environmental chamber. The reciprocating motion table is controlled to contact a physical fixed point made of near-zero thermal expansion material in a predetermined cycle, and the readings of the displacement sensor being measured and the reference readings are simultaneously locked at the moment of contact. Using the absolute position corresponding to the physical fixed point as a common reference, the drift of the reference itself is determined and subtracted in each cycle. Then, the reference reading after deducting the drift is compared with the full-stroke reading of the displacement sensor under test to obtain the pure degradation component of the displacement sensor under test. The pure degradation component is set with a threshold according to the working condition to identify the performance inflection point, classify the failure mode, and write it into the full life cycle digital file.

10. The method according to claim 9, characterized in that, Within the mechanical static window of the reciprocating motion table's stroke reversal, the measurement circuit of the displacement sensor under test is switched from the working signal channel to the insulation impedance test channel in a time-division manner to collect the insulation impedance, and the collected insulation impedance is used as one of the pure degradation components to participate in the classification of the failure modes.

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