Laser measurement device and method for displacement of piston of liquid-driven compressor

Abstract

The invention relates to the technical field of compressors, and discloses a laser measuring device and method for displacement of a hydraulic-driven compressor piston, the laser measuring device for displacement of the hydraulic-driven compressor piston comprises a lens cone and a laser sensor module, a reflector is fixed on the inner wall of the bottom of the lens cone, and an included angle of 45 degrees is formed between the reflector and the axis of the lens cone; a lens cone indication mark is fixed to the outer wall of the lens cone and right faces the reflector, the bottom of the lens cone is movably connected to a detection interface of a hydraulic drive compressor air cylinder, the laser sensor module is movably connected to the top of the lens cone in an inserted mode, and the direction of laser emitted by the laser sensor module is consistent with the axis of the lens cone. The laser is reflected by the reflector, irradiates the metal part of the piston and then is reflected back to the laser sensor module to obtain the position of the piston. The measuring device can accurately and visually reflect displacement, is small in installation space, is high in repeatability, is suitable for different occasions, and meets the requirements of production safety and explosion prevention.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and particularly to a laser measurement device and method for the piston displacement of a liquid-driven compressor. Background Art

[0002] A liquid-driven compressor is a special equipment dedicated to the compression field. Its core feature is to achieve high-pressure compression of gas through a hydraulic drive system (usually the working pressure ≥ 45 MPa), and it is widely used in hydrogen refueling stations, hydrogen energy storage systems, chemical hydrogen production, natural gas compression in the petrochemical industry, and liquid-driven argon compression for hot isostatic pressing, etc.

[0003] The main body of the liquid-driven compressor consists of four major parts: a hydraulic drive system, a compression cylinder system, a piston linkage mechanism, and a cooling system. The hydraulic drive system adopts a closed-loop control strategy, real-time monitors the piston dead center position through a high-precision dead center sensor, and intelligently controls the hydraulic reversing valve via a PLC control system to achieve precise switching of the direction of the hydraulic oil circuit. The piston linkage mechanism includes a crosshead, a piston rod, and a piston: when the hydraulic drive system inputs hydraulic oil to push the crosshead, the piston rod rigidly connected to the crosshead moves in the same direction. Since the piston and the piston rod usually adopt a non-rigid connection method, the piston rod drives the piston to complete the compression action through a thrust force during the movement.

[0004] Poor anti-interference ability of non-contact detection: Although the non-contact detection scheme based on ultrasonic or magnetic induction principle avoids mechanical contact wear, the strong vibration (>300Hz) during the operation of the compressor will seriously interfere with the signal stability, resulting in a decrease in detection accuracy by more than 40%, making it difficult to meet the requirements of high-precision control. Insufficient reliability of contact sensors: Traditional contact displacement sensors (such as LVDT) are prone to failure under high temperature (>120°C), oil pollution, and high pressure (>20MPa) working conditions, with an average service life of less than 2000 hours. At the same time, limited by the structure of the hydraulic cylinder, the installation position of the sensor is restricted, and the measurement range is difficult to cover the full stroke of the piston, resulting in insufficient data integrity. For the measurement of the piston displacement of a hydraulic drive compressor, most use a contact detection method to detect the piston displacement by detecting the flow of hydraulic oil. This is because when the crosshead moves in the oil cavity, the volume of the oil in the oil cavity will change. At this time, by detecting the transient flow of the hydraulic oil, the position of the crosshead in the oil cavity can be known, and thus the position of the piston can be reflected. However, this method does not consider the compressibility of the oil and the fact that the piston and the crosshead are not rigidly connected by the piston rod. There is usually some air mixed in the hydraulic oil, which will make the measurement of the hydraulic oil flowmeter inaccurate. Moreover, due to the non-rigid connection, the transient flow of this oil can only reflect the position of the crosshead in the oil cavity and cannot accurately reflect the position of the piston in the cylinder. There is also a part that uses a non-contact detection method, such as installing a signal sensor in the cylinder to detect the position of the piston. This method is applicable when the pressure is low, the installation space is satisfied, and the requirements for the production environment safety are not high. For most hydraulic drive compressor systems, the internal pressure of the cylinder is very high, the structure is compact, there is not enough installation space, and the requirements for the production safety environment are very high. Therefore, it is not suitable to arrange components with a large spatial volume and prone to production safety accidents. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a laser measurement device and method for the piston displacement of a hydraulic drive compressor, which can accurately and intuitively reflect the displacement, have a small installation space, strong repeatability, and can adapt to different occasions and meet the requirements of production safety and explosion protection.

[0006] The first aspect of the present invention provides a laser measurement device for the piston displacement of a hydraulic drive compressor, including: a lens barrel and a laser sensor module. A reflecting mirror is fixed to the inner wall of the bottom of the lens barrel, and the reflecting mirror forms a 45° angle with the axis of the lens barrel. A lens barrel indication mark is fixed to the outer wall of the lens barrel, and the lens barrel indication mark is directly opposite to the reflecting mirror. The bottom of the lens barrel is movably connected to the detection interface of the hydraulic drive compressor cylinder, and the laser sensor module is movably inserted into the top of the lens barrel. The laser direction emitted by the laser sensor module is consistent with the axis of the lens barrel. The laser is reflected by the reflecting mirror and then irradiates on the metal part of the piston and is reflected back to the laser sensor module to obtain the piston position.

[0007] Optionally, a sensor indication mark is fixed on the outer wall of the laser sensor module, and the orientation of the sensor indication mark is consistent with that of the lens barrel indication mark.

[0008] Optionally, the inner wall of the bottom of the lens barrel has an inclined surface, and the inclined surface forms a 45° angle with the axis of the lens barrel, and the reflecting mirror is fixed on the inclined surface.

[0009] Optionally, the inner wall of the bottom of the lens barrel has a flat surface, the flat surface extends along the axis of the lens barrel, and a reflecting mirror is fixed on the flat surface, and the reflecting mirror is a triangular prism smooth surface reflecting mirror.

[0010] Optionally, the outer wall of the bottom of the lens barrel has an external thread, and the external thread is in threaded fit with the detection interface of the cylinder of the liquid-driven compressor, and the two are fixed by a lens barrel locking nut.

[0011] Optionally, the outer wall of the top of the lens barrel has an internal thread, and the laser sensor module is in threaded fit with the lens barrel, and the two are fixed by a sensor locking nut.

[0012] The second aspect of the present invention provides a laser measurement method for the piston displacement of a liquid-driven compressor, using any one of the above laser measurement devices for the piston displacement of a liquid-driven compressor, including the following steps: Keep the indication direction of the lens barrel indication mark in the same plane as the longitudinal central section of the cylinder of the liquid-driven compressor, and keep the lens barrel indication mark and the cylinder of the liquid-driven compressor on the same side. The laser sensor module emits laser light, and the laser light is reflected by the reflecting mirror and then emitted in a direction perpendicular to the axis of the lens barrel and irradiates the metal part of the piston; The light reflected by the metal part of the piston is reflected by the reflecting mirror again into the laser sensor module to obtain the piston position.

[0013] Optionally, it further includes performing noise filtering on the data obtained by the laser sensor module using a vibration and noise suppression algorithm with adaptive characteristics, and then performing smoothing processing to obtain a smooth curve of the relationship between the voltage value and time.

[0014] Optionally, it further includes predicting the displacement trajectory of the piston corresponding to the blind area part of the laser sensor module, including: dividing the blind area according to the blind area distance of the laser sensor module, and at the same time obtaining the actual up and down stroke distances of the piston, obtaining the voltage value of the commutation point near the lower stroke part, and then fitting this part using a cubic function curve.

[0015] Optionally, fitting this part using a cubic function curve: fitting the cubic function curve according to the sampling point sequence and voltage value at the blind area boundary point, the slope value at that point, the peak serial number and the corresponding voltage value, and the distance between the actual installation position and the piston at the top and bottom dead centers to obtain a continuous and smooth displacement characteristic curve.

[0016] The technical solution provided by the embodiment of the present invention has the following advantages compared with the prior art: The present invention provides a laser measurement device and method for the piston displacement of a liquid-driven compressor. By detachably connecting the bottom of the lens barrel to the detection interface of the cylinder of the liquid-driven compressor, it can be installed on a narrow detection hole, meeting the characteristics of a small installation space and high repeatability. The laser sensor module at the top of the lens barrel emits laser, and the mirror reflection of the 45° mirror can accurately and intuitively reflect the piston position. The threaded and lock nut method is adopted, and the movable connection between the lens barrel and the detection interface of the cylinder of the liquid-driven compressor can finely adjust the insertion length and direction of the mirror, meeting the high-precision requirements. Moreover, the whole device has low power and adopts a sealed space form, which can meet the production safety and explosion-proof requirements. For the problem of the blind area of the laser sensor, theoretically, the distance between the laser sensor module and the mirror can be adjusted by adjusting the movable insertion position of the laser sensor module to avoid the blind area at the source. In addition, the device of the present invention has a long reusable time, reduces production costs and ensures the stable operation of production tests. It adopts a non-contact form, which can avoid mechanical wear and improve the service life of the product. Description of the Drawings

[0017] Figure 1 The method for reflecting the piston position through the oil transient flow in the prior art 1; Figure 2 The installation and working schematic diagram of the signal sensor in the hydraulic cylinder in the prior art 2; Figure 3 The process of reflecting the target displacement by two signal waves in the prior art 2; Figure 4 The structural schematic diagram of the laser measurement device for the piston displacement of the liquid-driven compressor provided by the embodiment of the present invention; Figure 5 The cross-sectional view of the laser measurement device for the piston displacement of the liquid-driven compressor provided by the first embodiment of the present invention; Figure 6 The cross-sectional view of the laser measurement device for the piston displacement of the liquid-driven compressor provided by the second embodiment of the present invention; Figure 7 The data processing and blind area prediction optimization algorithm process provided by the embodiment of the present invention; Figure 8 The original data curve measured by the laser sensor module provided by the embodiment of the present invention and the corresponding filtering and smoothing processing; Figure 9 The data curve after the original data is filtered and smoothed and the data comparison curve after the blind area is optimized provided by the embodiment of the present invention.

[0018] Explanation of the reference numerals: 1. Laser sensor module; 2. Sensor locking nut; 3. Lens barrel; 4. Lens barrel locking nut; 5. Reflecting mirror; 6. Sensor indication mark; 7. Lens barrel indication mark; 8. Plane. Detailed implementation manner

[0019] The following combines with the attached drawings to describe in detail a specific implementation manner of the present invention. However, it should be understood that the protection scope of the present invention is not limited by the specific implementation manner.

[0020] In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the attached drawings. It is only for the convenience of describing the technical solution of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0021] In a traditional liquid-driven compressor system, the piston is the core moving component. The accurate acquisition of its position information directly determines the compression ratio control accuracy, the accuracy of volumetric efficiency evaluation, and the system operation safety. However, there are still significant technical bottlenecks in the current piston position detection, mainly manifested as the following problems:

[0022] (1) Large indirect measurement error: Existing systems mostly rely on indirect parameters such as hydraulic pressure and flow rate to calculate the piston position. However, due to signal transmission lag, system dynamic response delay, and parameter coupling effects, there are large cumulative errors in the calculation results. Especially when abnormal conditions such as gas-liquid mixture or seal wear occur in the system, the position calculation error can exceed 15%, seriously affecting the control accuracy.

[0023] (2) Insufficient reliability of contact sensors: Traditional contact displacement sensors (such as LVDT) are prone to failure under high temperature (>120°C), oil pollution, and high pressure (>20 MPa) working conditions, and the average service life is less than 2000 hours. At the same time, restricted by the structure of the hydraulic cylinder, the installation position of the sensor is limited, and the measurement range is difficult to cover the full stroke of the piston, resulting in insufficient data integrity.

[0024] (3) Poor anti-interference ability of non-contact detection: Non-contact detection schemes based on ultrasonic or magnetic induction principles avoid mechanical contact wear. However, the strong vibration (>300 Hz) during the operation of the compressor will seriously interfere with the signal stability, resulting in a decrease in detection accuracy of more than 40%, making it difficult to meet the high-precision control requirements.

[0025] (4) Lack of visual monitoring means: The current system lacks an intuitive piston position feedback mechanism. Maintenance personnel need to frequently disassemble the equipment to verify the actual position of the piston, increasing the single maintenance time by 2 - 3 hours and resulting in low operation and maintenance efficiency.

[0026] (5) Safety hazards under high - pressure conditions: In an ultra - high - pressure (>30 MPa) environment, the installation of invasive sensors may damage the sealing structure of the hydraulic cylinder, posing a leakage risk, not meeting the safety production specifications, and at the same time affecting the reliability of experimental data. Two existing technologies are listed below for illustration.

[0027] Existing technology one: As Figure 1 shown, a hydraulic cylinder with displacement measurement function and a displacement measurement method relate to the field of hydraulic cylinders. The hydraulic cylinder includes: a cylinder body for containing liquid and a piston pushed by the liquid to move. The hydraulic cylinder further includes: a signal generator stationary relative to the cylinder body, which is used to emit and receive a first signal wave passing through the liquid to a target point stationary relative to the cylinder body, and the signal generator is also used to emit and receive a second signal wave passing through the liquid to the contact surface between the piston and the liquid; a timer for respectively recording the propagation times of the first signal wave and the second signal wave; a data processor for calculating the propagation speed according to the first distance between the first signal generator and the target point and the propagation time of the first signal wave, and calculating the second distance between the second signal generator and the piston according to the propagation time and propagation speed of the second signal wave.

[0028] Existing technology two: As Figure 2 and Figure 3 shown, a non - destructive monitoring device and method for the indicator diagram of a liquid - driven piston compressor relate to the technical field of liquid - driven piston compressors. The method includes: obtaining in real - time the circumferential strain data at the cylinder end - cover and the instantaneous flow rate data of the oil in the oil circuit between the oil cavity and the oil pump at the same moment; respectively calculating the real - time dynamic pressure in the cylinder and the real - time volume of the cylinder according to the circumferential strain data and the instantaneous flow rate data obtained in real - time; synchronously intercepting the real - time dynamic pressure and the real - time volume of the cylinder within a compression cycle, and performing non - dimensionalization processing on the intercepted real - time dynamic pressure and the real - time volume of the cylinder within a compression cycle to obtain the indicator diagram during the operation of the compressor, which can be used to monitor the operation state of the compressor in real - time.

[0029] Based on the above problems, the present invention will be described below through several specific embodiments. To keep the following description of the embodiments of the present invention clear and concise, the detailed description of known functions and known components may be omitted. When any component of the embodiments of the present invention appears in more than one drawing, the component can be represented by the same reference numeral in each drawing.

[0030] Refer to Figure 4 andFigure 5 , Figure 4 This is a schematic structural diagram of a laser measurement device for piston displacement of a liquid-driven compressor provided by an embodiment of the present invention. Figure 5 This is a cross-sectional view of a laser measurement device for piston displacement of a liquid-driven compressor provided by the first embodiment of the present invention. As Figure 4 and Figure 5 shown, the first part of the embodiment of the present invention provides a laser measurement device for piston displacement of a liquid-driven compressor, including: a lens barrel 3 and a laser sensor module 1. A reflecting mirror 5 is fixed to the inner wall of the bottom of the lens barrel 3, and the reflecting mirror 5 forms a 45° angle with the axis of the lens barrel 3. Since the direction and position of the bottom reflecting mirror 5 of the lens barrel 3 are hidden in the detection hole during the installation process of the lens barrel 3, a mark is needed to reflect the real-time position and direction of the reflecting mirror 5 inside the closed lens barrel 3. Therefore, a lens barrel indication mark 7 is fixed to the outer wall of the lens barrel 3, and the lens barrel indication mark 7 faces the reflecting mirror 5 directly. The bottom of the lens barrel 3 is movably connected to the detection interface of the liquid-driven compressor cylinder, and the laser sensor module 1 is movably inserted into the top of the lens barrel 3. The laser emission direction of the laser sensor module 1 is consistent with the axis of the lens barrel 3. The laser is reflected by the reflecting mirror 5 and then irradiates on the metal part of the piston and is reflected back to the laser sensor module 1 to obtain the piston position.

[0031] Regarding the optical path calibration: The lens barrel 3 forms a rigid connection with the detection interface of the liquid-driven cylinder. Based on the principle of the best specular reflection of the laser beam, to ensure that the emission axis of the laser sensor module 1 is perpendicular to the piston movement trajectory, and the specular reflection optical path of the reflecting mirror 5 is consistent with the piston movement direction, the spatial orientation of the reflecting mirror 5 can be precisely adjusted by using the lens barrel indication mark 7, so that the laser emitted by the laser sensor module 1 can be reflected by the reflecting mirror 5 and then irradiate on the piston metal part and be reflected back. Finally positioning the lens barrel 3 and the detection interface of the liquid-driven compressor cylinder can ensure the above requirements.

[0032] Regarding the experimental detection process: The laser sensor module 1 emits laser light that shines on the reflecting mirror 5. After being reflected by the reflecting mirror 5, a horizontal optical path is reflected onto the piston metal part. The light reflected by the piston is then reflected by the reflecting mirror 5 again and enters the laser sensor module 1 for distance calculation, and a corresponding voltage value is output to reflect the piston position.

[0033] The present invention provides a laser measurement device and method for the piston displacement of a liquid-driven compressor. By detachably connecting the bottom of the lens barrel to the detection interface of the cylinder of the liquid-driven compressor, it can be installed on a narrow detection hole, meeting the characteristics of a small installation space and high repeatability. The laser sensor module at the top of the lens barrel emits laser light, and the mirror reflection of the 45° mirror can accurately and intuitively reflect the piston position. The threaded and lock nut method is adopted, and the movable connection between the lens barrel and the detection interface of the cylinder of the liquid-driven compressor can finely adjust the insertion length and direction of the mirror, meeting the high-precision requirements, with low power consumption of the entire device and in the form of a closed space, which can meet the production safety and explosion-proof requirements. For the problem of the blind area of the laser sensor, theoretically, the distance between the laser sensor module and the mirror can be adjusted by adjusting the movable insertion position of the laser sensor module, avoiding the blind area from the root cause. In addition, the device of the present invention has a long reusable time, reduces production costs and ensures the stable operation of production tests. The non-contact form can avoid mechanical wear and improve the service life of the product.

[0034] As an alternative solution, a sensor indication mark 6 is fixed on the outer wall of the laser sensor module 1, and the sensor indication mark 6 is in the same orientation as the lens barrel indication mark 7.

[0035] Regarding the installation of the laser sensor module 1: The laser sensor module 1 is connected to the lens barrel 3 to achieve axial coupling. The orientation is calibrated through the sensor indication mark 6, and the direction indicated by the sensor indication mark 6 is corresponding to the direction indicated by the lens barrel indication mark 7. Subsequently, the laser sensor module 1 and the lens barrel 3 are fixed to complete the module fixation. Through the corresponding design of the direction indicated by the sensor indication mark 6 and the direction indicated by the lens barrel indication mark 7, the laser sensor module 1 and the mirror 5 can be fixed at the best angle to achieve the best measurement effect.

[0036] Refer again to Figure 5 , as an alternative solution, the inner wall of the bottom of the lens barrel 3 has an inclined surface, and the inclined surface forms a 45° angle with the axis of the lens barrel 3, and the mirror 5 is fixed on the inclined surface.

[0037] During machining, a 45° inclined plane can be machined inside the circular bottom of the lens barrel 3, and then the corresponding plane mirror, that is, the mirror 5, is attached to this inclined surface, such as in the form of glue or other forms that generate a rigid connection.

[0038] Refer to Figure 6 , Figure 6 is a cross-sectional view of the laser measurement device for the piston displacement of a liquid-driven compressor provided by the second embodiment of the present invention. As shown in Figure 6 , as another alternative solution, the inner wall of the bottom of the lens barrel 3 has a plane 8, the plane 8 extends along the axis of the lens barrel 3, and a mirror 5 is fixed on the plane 8. The mirror 5 is a triangular prism smooth surface mirror.

[0039] First, a flat plane 8 can be machined inside the circular bottom of the lens barrel 3, and then a 45° reflecting prism module, such as a triangular prism smooth surface reflecting mirror, is used to connect the plane 8 with the flat part of the 45° reflecting prism module. Adopting this flat plane 8 can reduce the difficulty of machine processing and save time and other benefits.

[0040] Optionally, the outer wall of the bottom of the lens barrel 3 has an external thread, which is threadedly engaged with the detection interface thread of the liquid-driven compressor cylinder, and the two are fixed by the lens barrel locking nut 4. In this way, on the one hand, the length of the lens barrel 3 extending into the liquid-driven compressor cylinder can be adjusted with high precision. In the actual process, because when the thread is machined, it cannot be guaranteed that when it is screwed to the bottom, the laser measuring device for the piston displacement of the liquid-driven compressor is exactly facing the correct direction. Therefore, the lens barrel locking nut 4 is needed to rigidly connect the laser measuring device for the piston displacement of the liquid-driven compressor with the hydraulic cylinder on the premise of ensuring the correct direction and appropriate extension length.

[0041] Optionally, the outer wall of the top of the lens barrel 3 has an internal thread, and the laser sensor module 1 is threadedly engaged with the lens barrel 3, and the two are fixed by the sensor locking nut 2.

[0042] Regarding the installation of the laser sensor module 1: The laser sensor module 1 realizes axial coupling through the external thread and the internal thread of the lens barrel 3, and the azimuth is calibrated through the sensor indication mark 6. The direction indicated by the sensor indication mark 6 is corresponding to the direction indicated by the lens barrel indication mark 7, and then the module is fixed by using the sensor locking nut 2; Regarding the optical path calibration: The lens barrel 3 forms a rigid connection with the detection interface of the liquid-driven cylinder through the external thread. Based on the principle of the best specular reflection of the laser beam, to ensure that the emission axis of the laser sensor module 1 is perpendicular to the piston movement trajectory, and the specular reflection optical path is consistent with the piston movement direction, the spatial azimuth of the reflecting mirror 5 can be accurately adjusted by using the lens barrel indication mark 7, so that the laser emitted by the laser sensor module 1 can be reflected by the reflecting mirror 5 and then shine on the metal part of the piston and be reflected back. The final positioning of the components is achieved through the lens barrel locking nut 4, and the above requirements can be ensured. By the above method, the reflecting mirror 5 can be ensured to be installed in place, and the rationality of the optical path can be ensured.

[0043] This dual-stage fastening method design not only ensures the structural stability of the laser measurement device, but also realizes the precise control of the spatial orientation of the optical elements through a dual-indication calibration system, providing a reliable guarantee for obtaining high-precision displacement measurement data. By using the design of the sensor locking nut 2 and the lens barrel locking nut 4, the relative position between the laser sensor module 1 and the mirror 5 can be finely adjusted, so that in theory, the measurement of the blind area can be avoided, and the requirement for the mirror 5 with different insertion lengths can be adjusted to adapt to the required insertion lengths in different scenarios, improving the applicability of the product in multiple scenarios, and reducing the experimental cost on the basis of ensuring the safety of experimental production and the accuracy of measurement.

[0044] The second part of the embodiments of the present invention provides a laser measurement method for the piston displacement of a liquid-driven compressor. Using any of the above laser measurement devices for the piston displacement of a liquid-driven compressor, the method includes the following steps: Keep the indication direction of the lens barrel indication mark 7 in the same plane as the longitudinal central section of the cylinder of the liquid-driven compressor, and keep the lens barrel indication mark 7 on the same side as the cylinder of the liquid-driven compressor. The laser sensor module 1 emits laser light, and the laser light is reflected by the mirror 5 and then emitted in a direction perpendicular to the axis of the lens barrel 3 and irradiates the metal part of the piston. The light reflected by the metal part of the piston is reflected by the mirror 5 again and then enters the laser sensor module 1 to obtain the position of the piston.

[0045] Optionally, it further includes performing noise filtering on the data obtained by the laser sensor module 1 using a vibration noise suppression algorithm with adaptive characteristics, and then performing smoothing processing to obtain a smooth curve of the corresponding relationship between the voltage value and time.

[0046] Since the amount of data collected by the original signal of the laser sensor module 1 is large and has noise signals, in order to obtain a smooth curve, it is necessary to perform filtering on the original signal. By using the low-pass filtering principle of the FFT filter and setting the cut-off frequency in real time, a satisfactory signal curve can be obtained. Then, by using the Savitzky-Golay method for smoothing curve processing and setting the corresponding window points and polynomial orders, the filtered signal curve can be smoothed. The vibration noise suppression algorithm with adaptive characteristics establishes a model of piston displacement and the voltage value of the laser sensor module 1 by collecting sensor signals in real time, and can dynamically adjust the signal filtering parameters to ensure that the displacement detection error is stably controlled within the allowable range under conditions such as the start-stop of the compressor and sudden changes in load.

[0047] Optionally, it further includes predicting the displacement trajectory of the piston corresponding to the blind area part of the laser sensor module 1, including: dividing the blind area according to the blind area distance of the laser sensor module 1, and at the same time determining the actual up and down stroke distance of the piston to obtain the voltage value of the commutation point near the lower stroke part, and then fitting this part with a cubic function curve. During measurement, the stroke size of the piston and the distance between the installation position and the bottom dead center need to be known. Through these geometric parameters, this data can be obtained. The data correction of this part is for the blind area part, and the curves of other parts are the same as the original filtered curve.

[0048] Regarding the experimental detection process: The laser sensor module 1 emits laser light that shines on the reflector 5. After being reflected by the reflector 5, a horizontal light path is reflected onto the metal part of the piston. The light reflected by the piston is then reflected by the reflector 5 again and enters the laser sensor module 1 for distance calculation, and the corresponding voltage value is output to reflect the piston position. Since the laser sensor module 1 usually has a blind area of a certain distance, theoretically, the distance between the laser sensor module 1 and the reflector 5 can be adjusted to solve the blind area part at the source. However, in actual operation, a blind area optimization algorithm can also be used to predict the displacement trajectory of the piston in the blind area part.

[0049] Optionally, fitting this part with a cubic function curve: According to the sampling point sequence and voltage value at the blind area boundary point, the slope value at that point, the peak serial number and the corresponding voltage value, as well as the distance between the actual installation position and the piston at the top and bottom dead centers, fit the cubic function curve to obtain a continuous and smooth displacement characteristic curve.

[0050] The blind area data reconstruction technology is adopted. Aiming at the problem of the physical measurement blind area of the laser displacement sensor, a displacement curve prediction algorithm based on the kinematic model is constructed: using a cubic function curve to fit the data, combined with the piston displacement threshold judgment, and outputting a continuous and smooth displacement characteristic curve to make the integrity of the displacement data meet the experimental requirements, providing a data basis for accurately drawing the in-cylinder P-V diagram.

[0051] Reference Figure 7 , Figure 7 is the data processing and blind area prediction optimization algorithm flow provided by the embodiment of the present invention. As Figure 7 shown, the second part of the embodiment of the present invention provides a laser measurement method for the piston displacement of a liquid-driven compressor, and the specific process is as follows: Regarding the data processing and blind area algorithm optimization part: First, perform noise filtering processing on the collected voltage value data as Figure 8As shown, after smoothing, a smooth curve is obtained. Then, according to the blind zone distance of the sensor module 1, the blind zone ratio is divided, and at the same time, the actual up and down stroke distance of the piston is determined to obtain the voltage value of the commutation point near the lower stroke part. Then, a cubic function curve is used to fit this part. The fitting curve needs to fit the cubic function curve according to the sampling point sequence and voltage value at the blind zone boundary point and the slope value at that point. Finally, a smooth curve that conforms to the actual situation is obtained, such as Figure 9 shown.

[0052] Collect the corresponding data, take a fixed period, set the data set of voltage values as A, and set its corresponding serial number as a. Then, the voltage value corresponding to the data with serial number a is denoted as A(a).

[0053] Find the peak and valley values in each period of the data set. Here, taking one period as an example, that is, the process of the piston moving from the bottom dead center to the top dead center and then back from the top dead center to the bottom dead center. The valley voltage is:

[0054] , Take the found as the bottom dead center signal, set the initial point corresponding to the signal sequence collected at this point, denoted as , then the initial point can be denoted as , The peak voltage in one period is: , And find the serial number corresponding to its maximum voltage value as , and denote this point as , Determine the lower blind zone distance of the device in space, denoted as: , and the distance between the installation detection hole position and the bottom dead center of the piston's lower stroke, denoted as , Then the actual size of the blind zone range is: , Confirm the stroke size of the piston in the whole space, denoted as , Obtain the corresponding blind zone space ratio: , According to the corresponding blind zone space ratio, divide the blind zone area that needs to be optimized and predicted within one period of the collected voltage values. The blind zone part of the first half cycle sequence is:

[0055] , According to the division of the blind area, the voltage values of the corresponding sequences at the boundary can be obtained, denoted as: , where is the serial number of this point at the boundary, is the voltage value of this point at the boundary.

[0056] According to the linear proportional correlation, the following method can be used to correct and process the voltage value at the bottom dead center.

[0057] , Through this method, the corrected voltage value at the bottom dead center can be obtained .

[0058] Based on the data coordinates at the bottom dead center and the data coordinates at the blind area boundary points obtained, a cubic function curve fitting is performed.

[0059] The corrected data coordinates at the bottom dead center are , Since the piston movement has symmetry and smooth transition, it can be known that at the bottom dead center, its slope is 0.

[0060] The data coordinates of the blind area boundary points are: , To ensure the smooth transition of the curve, it is necessary to optimize the slope at the blind area boundary points. Take the first and second data points in the non-blind area close to the data boundary points of the blind area, denoted as:

[0061] , , Then the magnitude of the slope at this point is: , Therefore, in order to keep the curve smooth, the slope at the blind area boundary point is the k corresponding to the above formula.

[0062] Using the cubic function for curve fitting again, assume the function curve is: , where is the cubic term coefficient, n is the quadratic term coefficient, p is the linear term coefficient, is the constant term.

[0063] Substitute the data coordinates and slopes of the above bottom dead center and blind area boundary points into the above formula, and it can be solved through a linear equation, , , By solving the above linear equations, the coefficient magnitudes of the corresponding m, n, p, and t can be obtained.

[0064] According to the common sense of experiments and actual laws, it can be known that the cubic function curve must be monotonic in the blind area. Therefore, it is necessary to restrict the monotonicity of the function curve to be fitted. In the following way, within this area, the first derivative function of the function should be greater than 0.

[0065] , Judging from the above operations, the fitted curve conforms to the actual situation, thus correcting and predicting the curve for the blind area part.

[0066] The above are only several specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A laser measurement device for the piston displacement of a liquid-driven compressor, characterized in that, Comprising: A lens barrel (3) with a reflecting mirror (5) fixed to the inner wall of the bottom. The reflecting mirror (5) forms a 45° angle with the axis of the lens barrel (3). An indicating mark (7) of the lens barrel is fixed to the outer wall of the lens barrel (3), and the indicating mark (7) of the lens barrel is aligned with the reflecting mirror (5). The bottom of the lens barrel (3) is movably connected to the detection interface of the liquid-driven compressor cylinder. A laser sensor module (1) is movably inserted into the top of the lens barrel (3). The laser emitted by the laser sensor module (1) has the same direction as the axis of the lens barrel (3). The laser is reflected by the reflecting mirror (5) and then irradiates on the metal part of the piston and is reflected back to the laser sensor module (1) to obtain the piston position.

2. The laser measurement device for piston displacement of a liquid-driven compressor according to claim 1, characterized in that An indicating mark (6) of the sensor is fixed to the outer wall of the laser sensor module (1), and the indicating mark (6) of the sensor is in the same orientation as the indicating mark (7) of the lens barrel.

3. The laser measurement device for piston displacement of a liquid-driven compressor according to claim 1, characterized in that, The inner wall of the bottom of the lens barrel (3) has an inclined surface that forms a 45° angle with the axis of the lens barrel (3), and the reflecting mirror (5) is fixed to the inclined surface.

4. The laser measuring device for piston displacement of a liquid-driven compressor according to claim 1, wherein The inner wall of the bottom of the lens barrel (3) has a flat surface (8) that extends along the axis of the lens barrel (3), and the reflecting mirror (5) is fixed on the flat surface (8). The reflecting mirror (5) is a triangular prism smooth surface reflecting mirror.

5. The laser measurement device for piston displacement of a liquid-driven compressor according to claim 1, characterized in that, The outer wall of the bottom of the lens barrel (3) has an external thread that is threadedly engaged with the detection interface of the liquid-driven compressor cylinder, and the two are fixed by a lens barrel locking nut (4).

6. The laser measurement device for piston displacement of a liquid-driven compressor according to claim 1, characterized in that, The outer wall of the top of the lens barrel (3) has an internal thread, and the laser sensor module (1) is threadedly engaged with the lens barrel (3), and the two are fixed by a sensor locking nut (2).

7. A laser measurement method for the piston displacement of a liquid-driven compressor, using the laser measurement device for the piston displacement of a liquid-driven compressor according to any one of claims 1 to 6, characterized in that, Including the following steps: Keep the indicating direction of the indicating mark (7) of the lens barrel in the same plane as the longitudinal central section of the liquid-driven compressor cylinder, and keep the indicating mark (7) of the lens barrel on the same side as the liquid-driven compressor cylinder. The laser sensor module (1) emits laser, and the laser is reflected by the reflecting mirror (5) and then emits in a direction perpendicular to the axis of the lens barrel (3) and irradiates on the metal part of the piston. The light reflected by the metal part of the piston is reflected by the reflecting mirror (5) again and into the laser sensor module (1) to obtain the piston position.

8. The laser measurement method for piston displacement of a liquid-driven compressor according to claim 7, characterized in that, It also includes using an adaptive vibration and noise suppression algorithm to perform noise filtering on the data obtained by the laser sensor module (1), and then through smoothing processing to obtain a smooth curve of the corresponding relationship between voltage value and time.

9. The laser measurement method for piston displacement of a liquid-driven compressor according to claim 7, characterized in that, It also includes predicting the displacement trajectory of the piston corresponding to the blind area part of the laser sensor module (1), including: dividing the blind area according to the blind area distance of the laser sensor module (1), and at the same time obtaining the actual up and down stroke distances of the piston, obtaining the voltage value of the commutation point near the lower stroke part, and then fitting this part with a cubic function curve.

10. The laser measurement method for the piston displacement of a liquid-driven compressor according to claim 9, characterized in that, The fitting of this part with a cubic function curve: According to the sampling point sequence and voltage value at the blind area boundary point, the slope value at that point, the peak serial number and the corresponding voltage value, and the distance between the actual installation position and the piston at the top and bottom dead centers, fit the cubic function curve to obtain the continuous and smooth displacement characteristic curve.

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