Ultralow-temperature cascade refrigeration device

Abstract

The invention discloses an ultralow-temperature cascade refrigeration device, belongs to the technical field of refrigeration devices, and solves the problems that when a low-temperature screw compressor continuously operates below-80 DEG C, organic acid generated by hydrolysis of trace moisture and ester lubricating oil and metal chips form colloidal deposition, the resistance of a slide valve is increased, displacement lag is caused, and the service life of the slide valve is prolonged. However, the sensor only feeds back an instruction signal and cannot be monitored by a control system, and finally bearing wear or energy efficiency reduction is caused. Comprising a screw compressor and a slide valve state monitoring circuit arranged in the screw compressor. The actual displacement of the slide valve is measured in real time through double-frequency laser interference, the thickness of jelly is analyzed in combination with acoustic surface wave frequency shift, the fault index is calculated after dynamic compensation, early warning is conducted when the limit is exceeded, a blind area of a traditional sensor is eliminated, diagnosis is conducted in advance, and compressor bearing abrasion is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration devices, and in particular to an ultra-low temperature cascade refrigeration device. Background Art

[0002] A super-low-temperature cascade refrigeration unit, also known as a cascade freezer, is a cryogenic device that operates through a two-stage cascade cycle of high and low temperatures. The low-temperature stage typically uses a screw or piston compressor with a refrigerant such as R23, while the high-temperature stage typically uses a screw compressor with a refrigerant such as R404A. The two stages are thermally coupled via a condenser-evaporator. Its electrical system includes a main controller, temperature and pressure sensors, a compressor inverter module, a solenoid valve assembly, and a safety interlock circuit, enabling precise control of operating parameters in both stages. Suitable for refrigeration needs ranging from -40°C to -150°C, this device is widely used in fields such as pharmaceutical freezing and cryogenic material testing. Its two-stage relay refrigeration achieves ultra-low temperature output, combining high efficiency and stability.

[0003] When the low-temperature screw compressors of cascade refrigerators operate continuously at ultra-low temperatures below -80°C, trace amounts of water remaining in the system hydrolyze with the ester synthetic lubricant, generating low-molecular-weight organic acids. These acids combine with metal debris from compressor wear to form a viscous, colloidal polymer that gradually deposits in the gap between the slide valve guide rail and the sealing surface. Over time, the colloidal polymer significantly increases the resistance to slide valve movement, causing a mechanical lag between the controller's commanded displacement and the actual displacement.

[0004] However, since the slide valve position sensor only feeds back command signals instead of actual mechanical displacement, the control system is unable to detect the displacement deviation, making the colloid deposition process an unmonitored "gray box" until abnormal wear of the compressor bearings or a significant decrease in energy efficiency is detected.

[0005] Therefore, an ultra-low temperature cascade refrigeration device is proposed to solve or alleviate the above problems. Summary of the Invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose an ultra-low temperature cascade refrigeration device.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A super-low-temperature cascade refrigeration device includes a screw compressor and a slide valve status monitoring circuit arranged in the screw compressor. The slide valve status monitoring circuit uses dual-frequency laser interferometry to detect the deviation between the actual displacement of the slide valve and the command value in real time, combines surface acoustic wave resonant frequency shift to analyze the thickness of colloid deposition, and then calculates the deposition fault index after dynamic compensation of multiple physical field parameters. When it is identified that the displacement hysteresis increases abnormally or the deposition thickness exceeds the standard, the analog warning signal is triggered in a graded manner.

[0008] Preferably, the slide valve state monitoring circuit includes a dual-frequency laser interferometer displacement module, a surface acoustic wave material analysis module, a multi-physics field compensation module, a data fusion processor module, an industrial interface module, and a power supply module; The dual-frequency laser interference displacement module is used to collect real-time phase difference signals, the surface acoustic wave material analysis module is used to collect resonant frequency signals, the multi-physics field compensation module is used to collect temperature, stress and air pressure parameters to compensate for temperature drift of the frequency signal, the data fusion processor module is used to calculate the absolute difference between the controller command displacement and the actual compensation displacement as the displacement hysteresis, calculate the difference between the compensation frequency and the fundamental frequency divided by the product of the material constant and the square of the fundamental frequency as the deposition thickness, calculate the sum of the third to fifth harmonic amplitudes and the percentage of the fundamental amplitude as the motion nonlinearity, weightedly sum the normalized displacement hysteresis, deposition thickness and nonlinearity according to the weight coefficient, dynamically adjust the weight coefficient and threshold parameter according to the running time, divide the fault state into four levels according to the fault index value range and set the judgment conditions, the industrial interface module is used to transmit the fault state to the host computer, and the power supply module supplies power to each module.

[0009] Preferably, the phase difference voltage output end of the dual-frequency laser interference displacement module is connected to the analog signal input dedicated channel of the data fusion processor module through a shielded wire, the serial peripheral interface bus of the surface acoustic wave material analysis module is connected to the synchronous clock line, serial data line, and chip enable line of the data fusion processor module through a flat cable, the analog-to-digital conversion output of the multi-physics field compensation module is connected to the clock line, data output line, and data input line of the data fusion processor module, the internal integrated circuit interface of the multi-physics field compensation module is connected to the serial clock line and serial data line of the data fusion processor module through a twisted pair cable, the digital output channel of the data fusion processor module is connected to the isolated input channel of the industrial interface module, the output end of the industrial interface module is used to connect to the host computer, and the output end of the power supply module is respectively connected to the power input end of each module.

[0010] Preferably, the dual-frequency laser interferometer displacement module includes a first distributed feedback laser DFB-1550, a second distributed feedback laser DFB-1550, a polarization beam combiner, a polarization beam splitter, a reference mirror, a measurement reflector, a balanced photodetector, and an AD8302 phase detection chip. The reference mirror is fixedly connected to the housing of the screw compressor, and the measurement reflector is fixedly connected to the slide valve push rod in the screw compressor. The positive poles of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 are connected to the output end of the power module, the negative poles of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 are grounded, and the laser output of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 is connected to the ground. The output ends are respectively connected to the first optical signal input end and the second optical signal input end of the polarization beam combiner, the combined light output end of the polarization beam combiner is connected to the optical signal input end of the polarization beam splitter, the reference light output end of the polarization beam splitter is used to connect to the incident surface of the fixed reflector, and the measurement light output end of the polarization beam splitter is used to connect to the incident surface of the slide valve reflector. The reference light signal input end of the balanced photodetector is used to connect to the reflected light path of the fixed reflector, and the measurement light signal input end of the balanced photodetector is used to connect to the reflected light path of the slide valve reflector. The in-phase signal output end of the balanced photodetector is connected to the in-phase voltage input end of the AD8302 phase detection chip, and the phase difference voltage output end of the AD8302 phase detection chip is connected to the analog signal input dedicated channel of the XC7A100T field programmable gate array chip in the data fusion processor module.

[0011] Preferably, the surface acoustic wave material analysis module includes an HMC583LP5 microwave oscillator, a circulator, a surface acoustic wave sensor, an ADL6012 detector, and an ADF4351 frequency synthesizer. The RF signal output end of the HMC583LP5 microwave oscillator is connected to the RF input port of the circulator, the RF output port of the circulator is connected to the signal input port of the surface acoustic wave sensor, the reflected signal port of the circulator is connected to the RF signal input end of the ADL6012 detector, the envelope signal output end of the ADL6012 detector is connected to the signal input end of the ADF4351 frequency synthesizer, the serial peripheral interface clock line of the ADF4351 frequency synthesizer is connected to the first clock signal end of the XC7A100T field programmable gate array chip in the data fusion processor module, and the serial data output end of the ADF4351 frequency synthesizer is connected to the first data receiving end of the XC7A100T field programmable gate array chip in the data fusion processor module.

[0012] Preferably, the multi-physics field compensation module includes a PT1000 platinum resistance temperature sensor, a REF200 constant current source chip, an AD8420 instrument amplifier, an ADS1248 analog-to-digital converter, a CEA-13 strain gauge full bridge, an HX711 bridge ADC, and a BMP388 pressure sensor. The current excitation positive terminal of the PT1000 platinum resistance temperature sensor is connected to the current output terminal of the REF200 constant current source chip, the voltage sensing positive terminal of the PT1000 platinum resistance temperature sensor is connected to the in-phase input terminal of the AD8420 instrument amplifier, the signal output terminal of the AD8420 instrument amplifier is connected to the analog input channel of the ADS1248 analog-to-digital converter, and the serial clock input terminal of the ADS1248 analog-to-digital converter is connected to the XC7A100T field programmable gate array in the data fusion processor module. The second clock signal end of the column chip, the serial data output end of the ADS1248 analog-to-digital converter is connected to the second data receiving end of the XC7A100T field programmable gate array chip in the data fusion processor module, the full bridge output end of the CEA-13 strain gauge full bridge is connected to the input end of the HX711 bridge ADC, the clock end and output end of the HX711 bridge ADC are both connected to the XC7A100T field programmable gate array chip in the data fusion processor module, the serial clock signal end of the BMP388 air pressure sensor is connected to the third clock signal end of the XC7A100T field programmable gate array chip in the data fusion processor module, and the serial data output end of the BMP388 air pressure sensor is connected to the serial data end of the XC7A100T field programmable gate array chip in the data fusion processor module.

[0013] Preferably, the data fusion processor module includes an XC7A100T field programmable gate array chip, an IS61WV102416BLL static random access memory, and a SIT5356 crystal oscillator. The address bus, data bus, and control signal of the IS61WV102416BLL static random access memory are all connected to the XC7A100T field programmable gate array chip, and the output end of the SIT5356 crystal oscillator is connected to the clock input end of the XC7A100T field programmable gate array chip.

[0014] Preferably, the industrial interface module includes an ADuM1410 digital isolator, an MCP2515 controller area network controller, and a TJA1050 controller area network transceiver. The digital signal input end of the ADuM1410 digital isolator is connected to the digital output end of the XC7A100T field programmable gate array chip in the data fusion processor module, and the digital signal output end of the ADuM1410 digital isolator is connected to the MCP2515 controller area network controller. The outgoing end of the MCP2515 controller area network controller is used to connect to the host computer through the TJA1050 controller area network transceiver.

[0015] The present invention has the following beneficial effects: The state of the sliding valve in the cascade refrigeration device of the present invention is detected in real time by dual-frequency laser interferometry to detect the nanometer-level deviation between the actual displacement of the sliding valve and the command value, and the thickness of the colloid deposition is analyzed in combination with the surface acoustic wave resonant frequency shift. After dynamic compensation of multiple physical field parameters, the deposition fault index is calculated by fusion. When an abnormal increase in displacement hysteresis or an excess of deposition thickness is detected, a graded analog warning signal is triggered, thereby identifying the problem of mechanical hysteresis monitoring blind spots caused by traditional displacement sensors only feeding back command values ​​in ultra-low temperature environments. This enables early diagnosis of colloid deposition and avoids abnormal wear of compressor bearings in the cascade refrigeration device of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a structural block diagram of the present invention.

[0018] In the figure, 1. Dual-frequency laser interferometry displacement module; 2. Surface acoustic wave material analysis module; 3. Multi-physics field compensation module; 4. Data fusion processor module; 5. Industrial interface module; 6. Power supply module. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0021] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0022] In the description of the present invention, it should be understood that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when in use, or are the orientation or position relationship commonly understood by those skilled in the art. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0023] Furthermore, the terms “first,” “second,” “third,” etc., are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0024] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0025] A super-low-temperature cascade refrigeration device includes a screw compressor and a slide valve status monitoring circuit arranged in the screw compressor. The slide valve status monitoring circuit uses dual-frequency laser interferometry to detect the deviation between the actual displacement of the slide valve and the command value in real time, combines surface acoustic wave resonant frequency shift to analyze the thickness of colloid deposition, and then calculates the deposition fault index after dynamic compensation of multiple physical field parameters. When it is identified that the displacement hysteresis increases abnormally or the deposition thickness exceeds the standard, the analog warning signal is triggered in a graded manner.

[0026] like Figure 1As shown, the slide valve state monitoring circuit includes a dual-frequency laser interference displacement module 1, a surface acoustic wave material analysis module 2, a multi-physics field compensation module 3, a data fusion processor module 4, an industrial interface module 5, and a power supply module 6. The phase difference voltage output end of the dual-frequency laser interference displacement module 1 is connected to the analog signal input dedicated channel of the data fusion processor module 4 through a shielded wire, the serial peripheral interface bus of the surface acoustic wave material analysis module 2 is connected to the synchronous clock line, serial data line, and chip enable line of the data fusion processor module 4 through a flat cable, the analog-to-digital conversion output of the multi-physics field compensation module 3 is connected to the clock line, data output line, and data input line of the data fusion processor module 4, the internal integrated circuit interface of the multi-physics field compensation module 3 is connected to the serial clock line and serial data line of the data fusion processor module 4 through a twisted pair cable, the digital output channel of the data fusion processor module 4 is connected to the isolated input channel of the industrial interface module 5, the output end of the industrial interface module 5 is used to connect to the host computer, and the output end of the power supply module 6 is respectively connected to the power input end of each module.

[0027] The dual-frequency laser interferometer displacement module 1 includes a first distributed feedback laser DFB-1550, a second distributed feedback laser DFB-1550, a polarization beam combiner, a polarization beam splitter, a reference mirror, a measuring reflector, a balanced photodetector, and an AD8302 phase detection chip. The reference mirror is fixedly connected to the housing of the screw compressor, and the measuring reflector is fixedly connected to the sliding valve push rod in the screw compressor. The positive poles of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 are connected to the output end of the power supply module 6, the negative poles of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 are grounded, and the laser output of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 is connected to the ground. The output ends are respectively connected to the first optical signal input end and the second optical signal input end of the polarization beam combiner, the combined light output end of the polarization beam combiner is connected to the optical signal input end of the polarization beam splitter, the reference light output end of the polarization beam splitter is used to connect to the incident surface of the fixed reflector, the measurement light output end of the polarization beam splitter is used to connect to the incident surface of the slide valve reflector, the reference light signal input end of the balanced photodetector is used to connect to the reflected light path of the fixed reflector, the measurement light signal input end of the balanced photodetector is used to connect to the reflected light path of the slide valve reflector, the in-phase signal output end of the balanced photodetector is connected to the in-phase voltage input end of the AD8302 phase detection chip, and the phase difference voltage output end of the AD8302 phase detection chip is connected to the analog signal input dedicated channel of the XC7A100T field programmable gate array chip in the data fusion processor module 4.

[0028] The surface acoustic wave material analysis module 2 includes an HMC583LP5 microwave oscillator, a circulator, a surface acoustic wave sensor, an ADL6012 detector, and an ADF4351 frequency synthesizer. The RF signal output end of the HMC583LP5 microwave oscillator is connected to the RF input port of the circulator, the RF output port of the circulator is connected to the signal input port of the surface acoustic wave sensor, the reflected signal port of the circulator is connected to the RF signal input end of the ADL6012 detector, the envelope signal output end of the ADL6012 detector is connected to the signal input end of the ADF4351 frequency synthesizer, the serial peripheral interface clock line of the ADF4351 frequency synthesizer is connected to the first clock signal end of the XC7A100T field programmable gate array chip in the data fusion processor module 4, and the serial data output end of the ADF4351 frequency synthesizer is connected to the first data receiving end of the XC7A100T field programmable gate array chip in the data fusion processor module 4.

[0029] Multi-physics field compensation module 3 includes a PT1000 platinum resistance temperature sensor, a REF200 constant current source chip, an AD8420 instrumentation amplifier, an ADS1248 analog-to-digital converter, a CEA-13 strain gauge full bridge, an HX711 bridge ADC, and a BMP388 pressure sensor. The current excitation positive terminal of the PT1000 platinum resistance temperature sensor is connected to the current output terminal of the REF200 constant current source chip, the voltage sensing positive terminal of the PT1000 platinum resistance temperature sensor is connected to the non-inverting input terminal of the AD8420 instrumentation amplifier, the signal output terminal of the AD8420 instrumentation amplifier is connected to the analog input channel of the ADS1248 analog-to-digital converter, and the serial clock input terminal of the ADS1248 analog-to-digital converter is connected to the XC7A100T field programmable gate array chip in the data fusion processor module 4. The second clock signal end of the ADS1248 analog-to-digital converter is connected to the second data receiving end of the XC7A100T field programmable gate array chip in the data fusion processor module 4, the full-bridge output end of the CEA-13 strain gauge full bridge is connected to the input end of the HX711 bridge ADC, the clock end and output end of the HX711 bridge ADC are both connected to the XC7A100T field programmable gate array chip in the data fusion processor module 4, the serial clock signal end of the BMP388 pressure sensor is connected to the third clock signal end of the XC7A100T field programmable gate array chip in the data fusion processor module 4, and the serial data output end of the BMP388 pressure sensor is connected to the serial data end of the XC7A100T field programmable gate array chip in the data fusion processor module 4.

[0030] The data fusion processor module 4 includes an XC7A100T field programmable gate array chip, an IS61WV102416BLL static random access memory, and a SIT5356 crystal oscillator. The address bus, data bus, and control signals of the IS61WV102416BLL static random access memory are all connected to the XC7A100T field programmable gate array chip, and the output end of the SIT5356 crystal oscillator is connected to the clock input end of the XC7A100T field programmable gate array chip.

[0031] Industrial interface module 5 includes an ADuM1410 digital isolator, an MCP2515 controller area network controller, and a TJA1050 controller area network transceiver. The digital signal input end of the ADuM1410 digital isolator is connected to the digital output end of the XC7A100T field programmable gate array chip in the data fusion processor module 4, and the digital signal output end of the ADuM1410 digital isolator is connected to the MCP2515 controller area network controller. The outgoing end of the MCP2515 controller area network controller is used to connect to the host computer through the TJA1050 controller area network transceiver.

[0032] The dual-frequency laser interferometer displacement module 1 is used to collect real-time phase difference signals, multiplying the real-time phase difference by the laser wavelength and then dividing it by four times the pi constant. The surface acoustic wave material analysis module 2 is used to collect resonant frequency signals, adding the fundamental frequency to the product of the material constant and the deposition thickness; The multi-physics field compensation module 3 is used to collect temperature, stress and air pressure parameters to perform thermal expansion compensation, stress compensation and air pressure refractive index compensation on the displacement signal, and temperature drift compensation on the frequency signal; The specific displacement compensation is the original displacement value multiplied by the compensation coefficient including the temperature deviation term, stress term and air pressure deviation term. The temperature deviation coefficient is negative nine times ten to the power of negative seven per degree Celsius, the stress coefficient is negative three times ten to the power of negative eight per microstrain, and the air pressure deviation coefficient is positive seven point six times ten to the power of negative seven per hectopascals. The specific frequency compensation is the original frequency value multiplied by one minus the product of the temperature drift coefficient and the temperature deviation. The temperature drift coefficient is ten to the power of negative six per degree Celsius. The data fusion processor module 4 is used to calculate the absolute difference between the controller command displacement and the actual compensation displacement as the displacement hysteresis, calculate the difference between the compensation frequency and the fundamental frequency divided by the product of the material constant and the square of the fundamental frequency as the deposition thickness, and calculate the percentage of the sum of the third to fifth harmonic amplitudes to the fundamental amplitude as the motion nonlinearity; The normalized displacement hysteresis, deposition thickness, and nonlinearity are weighted and summed according to the weight coefficient, and the weight coefficient and threshold parameters are dynamically adjusted according to the operating time. The deposition fault index is calculated as the quotient of the displacement hysteresis divided by its maximum threshold multiplied by a weight of 0.6, plus the quotient of the deposition thickness divided by its maximum threshold multiplied by a weight of 0.3, plus the motion nonlinearity multiplied by a weight of 0.1; the weight coefficient is dynamically optimized as the displacement hysteresis weight increases by 0.1 multiplied by the value of the hyperbolic tangent function over time, and the independent variable of the hyperbolic tangent function is 1% of the operating time; the threshold is self-tuned as the maximum displacement hysteresis threshold is initially 20 microns, and increases by 0.5 microns every thousand hours of operation; The fault state is divided into four levels according to the fault index value range and the judgment conditions are set. The specific judgment conditions are as follows: When the fault index is less than 0.3, it is considered normal, and the displacement hysteresis must be less than five microns and the deposition thickness must be less than one micron; When the fault index is greater than or equal to 0.3 and less than 0.5, it is judged to be in a warning state, and the displacement hysteresis keeps an upward trend for ten consecutive minutes; When the fault index is greater than or equal to 0.5 and less than 0.7, it is judged as a moderate fault, the deposition thickness is greater than 10 microns or the motion nonlinearity is greater than 15%; When the fault index is greater than or equal to 0.7, it is judged as a serious fault, the displacement hysteresis is greater than 15 microns and the deposition thickness is greater than 30 microns The industrial interface module 5 is used to transmit the fault status to the host computer, and the power supply module 6 provides power to each module.

[0033] More specifically, When the ultra-low temperature cascade refrigeration device continuously operates in an ultra-low temperature environment of minus 80 degrees Celsius, the first distributed feedback laser and the second distributed feedback laser in the dual-frequency laser interferometer displacement module 1 respectively emit orthogonally polarized laser beams with a wavelength of 1,550 nanometers. After being combined by the polarization beam combiner, they enter the polarization beam splitter and are divided into a reference light path and a measurement light path. The reference light path returns through the reference mirror, and the measurement light path returns through the measurement reflector magnetically adsorbed to the slide valve push rod. The two light beams generate interference in the balanced photodetector and are transmitted from the in-phase signal output terminal and the orthogonal signal output terminal to the in-phase input terminal and the orthogonal input terminal of the phase detection chip. The phase difference voltage output terminal of the phase detection chip outputs an analog signal proportional to the slide valve displacement in real time.

[0034] At the same time, the RF signal output end of the microwave oscillator in the surface acoustic wave material analysis module 2 generates a 433 MHz excitation signal which is input through the first port of the circulator and output through the second port to the RF signal port of the surface acoustic wave sensor.

[0035] When colloid is deposited on the slide valve guide rail, the surface wave velocity of the surface acoustic wave sensor changes, causing the resonant frequency of the reflected signal to shift. This signal is transmitted to the RF signal input terminal of the detector through the third port of the circulator, and its envelope signal output terminal transmits the frequency shift characteristics to the signal input port of the frequency counter.

[0036] The multi-physics field compensation module 3 collects the temperature of the sliding valve area through a platinum resistance temperature sensor. The positive end of its excitation current is connected to the positive end of the current output of the constant current source chip, and the positive end of the sensor signal is connected to the non-inverting input end of the instrument amplifier. The signal output end of the instrument amplifier sends the amplified temperature signal to the first analog input channel of the analog-to-digital converter. The strain gauge full bridge is pasted on the casing of the screw compressor, and the positive end of its full-bridge output is connected to the non-inverting input channel of the bridge ADC to monitor mechanical stress. The air pressure sensor transmits the air pressure data to the data fusion processor module 4 through the internal integrated circuit interface.

[0037] The field programmable gate array chip in the data fusion processor module 4 collects the phase difference voltage through the analog signal input dedicated channel, calculates the real-time displacement value after internal analog-to-digital conversion, and simultaneously obtains the compensation frequency output by the frequency counter through the clock line and data line of the first serial peripheral interface, and performs multi-physical field compensation in combination with the temperature, stress and air pressure parameters.

[0038] The compensation displacement is generated by applying the thermal expansion compensation coefficient of negative nine times ten to the power of negative seven per degree Celsius, the stress compensation coefficient of negative three times ten to the power of negative eight per microstrain, and the pressure refractive index compensation coefficient of positive seven point six times ten to the power of negative seven per hectopascals to the displacement value. The compensation frequency is generated by applying the temperature drift coefficient of tens to the power of negative six per degree Celsius to the surface acoustic wave frequency.

[0039] During the feature extraction stage, the field programmable gate array chip calculates the absolute difference between the controller's command displacement and the compensation displacement as the displacement lag. The deposition thickness is obtained by dividing (compensation frequency minus 433 MHz) by the product of 2.3 times 10 to the negative power and the square of the fundamental frequency. At the same time, the motion nonlinearity is calculated by analyzing the ratio of the third to fifth harmonic amplitudes of the vibration spectrum to the fundamental amplitude.

[0040] During the data fusion stage, the normalized displacement hysteresis is divided by the dynamic threshold (initial 20 microns, increasing by 0.5 microns every thousand hours), the deposition thickness is divided by the 50-micron threshold, and the motion nonlinearity value is fused with weight coefficients of 0.6, 0.3, and 0.1 to generate a deposition fault index. When the value of the deposition fault index exceeds 0.3, the fault diagnosis logic is activated: a continuous increase in the displacement hysteresis for ten consecutive minutes is judged as a warning state; when the deposition thickness is greater than 10 microns or the motion nonlinearity is greater than 15%, it is upgraded to a moderate fault; when the displacement hysteresis exceeds 15 microns and the deposition thickness exceeds 30 microns, it is judged as a serious fault.

[0041] As a result, the screw compressor in this refrigeration device can achieve early identification of colloidal deposits at the one-micron level in an environment of minus 85 degrees Celsius, and the displacement hysteresis detection accuracy is plus or minus 0.5 microns, solving the problem of mechanical hysteresis deviation monitoring blind spots caused by traditional displacement sensors only feeding back command values, and providing early warning as much as possible to avoid faults such as abnormal wear of compressor bearings.

[0042] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A super-low temperature cascade refrigeration device, characterized in that: The invention comprises a screw compressor and a slide valve status monitoring circuit arranged in the screw compressor. The slide valve status monitoring circuit detects the deviation between the actual displacement of the slide valve and the command value in real time through dual-frequency laser interference, analyzes the colloid deposition thickness in combination with the surface acoustic wave resonance frequency shift, and then calculates the deposition fault index after dynamic compensation of multi-physical field parameters. When it is identified that the displacement hysteresis increases abnormally or the deposition thickness exceeds the standard, the analog warning signal is triggered in a graded manner.

2. The ultra-low temperature cascade refrigeration device according to claim 1, characterized in that: The slide valve state monitoring circuit comprises a dual-frequency laser interference displacement module (1), a surface acoustic wave material analysis module (2), a multi-physics field compensation module (3), a data fusion processor module (4), an industrial interface module (5), and a power supply module (6); The dual-frequency laser interference displacement module (1) is used to collect real-time phase difference signals, the surface acoustic wave material analysis module (2) is used to collect resonant frequency signals, the multi-physics field compensation module (3) is used to collect temperature, stress and air pressure parameters to compensate for temperature drift of the frequency signal, the data fusion processor module (4) is used to calculate the absolute difference between the controller command displacement and the actual compensation displacement as the displacement hysteresis, calculate the difference between the compensation frequency and the fundamental frequency divided by the product of the material constant and the square of the fundamental frequency as the deposition thickness, calculate the sum of the third to fifth harmonic amplitudes and the percentage of the fundamental amplitude as the motion nonlinearity, weight the normalized displacement hysteresis, deposition thickness and nonlinearity according to the weight coefficient, dynamically adjust the weight coefficient and threshold parameter according to the running time, divide the fault state into four levels according to the fault index value range and set the judgment condition, the industrial interface module (5) is used to transmit the fault state to the host computer, and the power supply module (6) supplies power to each module.

3. The ultra-low temperature cascade refrigeration device according to claim 2, characterized in that: The phase difference voltage output end of the dual-frequency laser interference displacement module (1) is connected to the analog signal input dedicated channel of the data fusion processor module (4) through a shielded wire, the serial peripheral interface bus of the surface acoustic wave material analysis module (2) is connected to the synchronous clock line, serial data line, and chip enable line of the data fusion processor module (4) through a flat cable, the analog-to-digital conversion output of the multi-physics field compensation module (3) is connected to the clock line, data output line, and data input line of the data fusion processor module (4), the internal integrated circuit interface of the multi-physics field compensation module (3) is connected to the serial clock line and serial data line of the data fusion processor module (4) through a twisted pair cable, the digital output channel of the data fusion processor module (4) is connected to the isolated input channel of the industrial interface module (5), the output end of the industrial interface module (5) is used to connect to the host computer, and the output end of the power supply module (6) is respectively connected to the power input end of each module.

4. The ultra-low temperature cascade refrigeration device according to claim 3, characterized in that: The dual-frequency laser interference displacement module (1) comprises a first distributed feedback laser DFB-1550, a second distributed feedback laser DFB-1550, a polarization beam combiner, a polarization beam splitter, a reference mirror, a measuring reflector, a balanced photodetector, and an AD8302 phase detection chip, wherein the reference mirror is fixedly connected to the housing of the screw compressor, the measuring reflector is fixedly connected to the slide valve push rod in the screw compressor, the positive poles of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 are connected to the output end of the power supply module (6), the negative poles of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 are grounded, and the laser outputs of the first distributed feedback laser DFB-1550 and the second distributed feedback laser DFB-1550 are grounded. The output ends are respectively connected to the first optical signal input end and the second optical signal input end of the polarization beam combiner, the beam combining output end of the polarization beam combiner is connected to the optical signal input end of the polarization beam splitter, the reference light output end of the polarization beam splitter is used to connect to the incident surface of the fixed reflector, the measurement light output end of the polarization beam splitter is used to connect to the incident surface of the slide valve reflector, the reference light signal input end of the balanced photodetector is used to connect to the fixed reflector reflection light path, the measurement light signal input end of the balanced photodetector is used to connect to the slide valve reflector reflection light path, the in-phase signal output end of the balanced photodetector is connected to the in-phase voltage input end of the AD8302 phase detection chip, and the phase difference voltage output end of the AD8302 phase detection chip is connected to the analog signal input dedicated channel of the XC7A100T field programmable gate array chip in the data fusion processor module (4).

5. The ultra-low temperature cascade refrigeration device according to claim 3, characterized in that: The surface acoustic wave material analysis module (2) comprises an HMC583LP5 microwave oscillator, a circulator, a surface acoustic wave sensor, an ADL6012 detector, and an ADF4351 frequency synthesizer. The radio frequency signal output end of the HMC583LP5 microwave oscillator is connected to the radio frequency input port of the circulator, the radio frequency output port of the circulator is connected to the signal input port of the surface acoustic wave sensor, the reflected signal port of the circulator is connected to the radio frequency signal input end of the ADL6012 detector, the envelope signal output end of the ADL6012 detector is connected to the signal input end of the ADF4351 frequency synthesizer, the serial peripheral interface clock line of the ADF4351 frequency synthesizer is connected to the first clock signal end of the XC7A100T field programmable gate array chip in the data fusion processor module (4), and the serial data output end of the ADF4351 frequency synthesizer is connected to the first data receiving end of the XC7A100T field programmable gate array chip in the data fusion processor module (4).

6. The ultra-low temperature cascade refrigeration device according to claim 3, characterized in that: The multi-physics field compensation module (3) includes a PT1000 platinum resistance temperature sensor, a REF200 constant current source chip, an AD8420 instrument amplifier, an ADS1248 analog-to-digital converter, a CEA-13 strain gauge full bridge, an HX711 bridge ADC, and a BMP388 pressure sensor. The current excitation positive terminal of the PT1000 platinum resistance temperature sensor is connected to the current output terminal of the REF200 constant current source chip, the voltage sensing positive terminal of the PT1000 platinum resistance temperature sensor is connected to the in-phase input terminal of the AD8420 instrument amplifier, the signal output terminal of the AD8420 instrument amplifier is connected to the analog input channel of the ADS1248 analog-to-digital converter, and the serial clock input terminal of the ADS1248 analog-to-digital converter is connected to the first phase of the XC7A100T field programmable gate array chip in the data fusion processor module (4). The second clock signal terminal, the serial data output terminal of the ADS1248 analog-to-digital converter is connected to the second data receiving terminal of the XC7A100T field programmable gate array chip in the data fusion processor module (4), the full bridge output terminal of the CEA-13 strain gauge full bridge is connected to the input terminal of the HX711 bridge ADC, the clock terminal and the output terminal of the HX711 bridge ADC are both connected to the XC7A100T field programmable gate array chip in the data fusion processor module (4), the serial clock signal terminal of the BMP388 air pressure sensor is connected to the third clock signal terminal of the XC7A100T field programmable gate array chip in the data fusion processor module (4), and the serial data output terminal of the BMP388 air pressure sensor is connected to the serial data terminal of the XC7A100T field programmable gate array chip in the data fusion processor module (4).

7. The ultra-low temperature cascade refrigeration device according to claim 3, characterized in that: The data fusion processor module (4) includes an XC7A100T field programmable gate array chip, an IS61WV102416BLL static random access memory, and a SIT5356 crystal oscillator. The address bus, data bus, and control signal of the IS61WV102416BLL static random access memory are all connected to the XC7A100T field programmable gate array chip, and the output end of the SIT5356 crystal oscillator is connected to the clock input end of the XC7A100T field programmable gate array chip.

8. The ultra-low temperature cascade refrigeration device according to claim 3, characterized in that: The industrial interface module (5) includes an ADuM1410 digital isolator, an MCP2515 controller area network controller, and a TJA1050 controller area network transceiver. The digital signal input end of the ADuM1410 digital isolator is connected to the digital output end of the XC7A100T field programmable gate array chip in the data fusion processor module (4). The digital signal output end of the ADuM1410 digital isolator is connected to the MCP2515 controller area network controller. The outgoing end of the MCP2515 controller area network controller is used to connect to the host computer through the TJA1050 controller area network transceiver.

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