A hydraulic system oil leakage detection method based on a press

Abstract

The application discloses a hydraulic system oil leakage detection method based on a press, relates to the technical field of hydraulic system oil leakage detection, and realizes accurate detection through high-emissivity reference plate auxiliary radiation inversion and contrast verification. The high-emissivity reference plate is arranged beside the detected target, the surface temperature of the reference plate is obtained, the equivalent radiation of the reference plate is calculated according to the Stefan-Boltzmann law, the image of the detected target is collected by using an infrared thermal imager, the target is divided into regions, and the equivalent radiation of the target is calculated; the above measurement is repeated after the temperature of the reference plate is changed, equations are established by using two groups of radiation data, and the equivalent emissivity of the detected target and the real surface temperature of the target are solved. The dry metal surface without oil is set as a dry contrast area, the equivalent emissivity of the dry contrast area is calculated, a difference value of the reflection coefficient is obtained through comparison, a leakage suspicious area is marked in combination with a temperature underestimation and an environmental temperature, a leakage positioning list is generated by taking a schematic diagram of a hydraulic system loop corresponding to the suspicious area, and whether external leakage exists is determined according to the leakage positioning list.

Description

Technical Field

[0001] This invention relates to the field of hydraulic system oil leakage detection technology, and specifically to a method for detecting oil leakage in a hydraulic system based on a press. Background Technology

[0002] Presses are widely used in industrial fields such as food processing, metallurgical forging, and building material forming. Their hydraulic systems, as the core of power transmission and control, integrate key components such as pump stations, valves, pipelines, and cylinders, and need to operate continuously under high-speed cyclic conditions. This system is constantly exposed to a complex environment of humidity and heat, cleaning agent residue, mechanical vibration, and dust corrosion, which can easily lead to aging of seals and loosening of pipeline joints, resulting in external leakage of hydraulic oil. Leakage often manifests as minor oil seepage or oil mist.

[0003] The demand for leak detection in the field is focused on speed and non-contact methods. Currently, the mainstream technology is infrared thermography. However, traditional infrared thermography has a core bottleneck in this scenario: leaking hydraulic oil forms an ultra-thin oil film on the metal surface, significantly altering the infrared radiation characteristics of the measured area. This dynamically reduces apparent emissivity and enhances environmental radiation reflection. Traditional methods rely on fixed empirical emissivity for temperature inversion, failing to distinguish the proportion of self-emission and environmental reflection in the radiation signal, and also unable to quantify oil film interference. This leads to a systematic underestimation of the true temperature at the leak location, causing initial, minute leaks to be masked and missed. Furthermore, the detection results rely on subjective human judgment, resulting in poor stability and difficulty in achieving system-level leak location and accurate determination across multiple components, thus failing to meet the accuracy and reliability requirements of on-site detection. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a method for detecting oil leaks in hydraulic systems based on presses, solving the problem of difficulty in accurately locating and determining system-level leaks in multiple components.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A high emissivity reference plate is placed next to the target under inspection, so that the infrared radiation of the high emissivity reference plate is projected onto the surface of the target under inspection. The high emissivity reference plate is a material with an emissivity close to 1. The surface temperature of the high emissivity reference plate is obtained and the equivalent radiation of the reference plate is calculated according to the Stefan-Boltzmann law. The apparent temperature of the target under inspection is obtained and the equivalent radiation of the target under inspection is calculated according to the Stefan-Boltzmann law.

[0007] Change the surface temperature of the high emissivity reference plate, and then recalculate the reference plate equivalent radiation and the target equivalent radiation of the inspected target after changing the surface temperature of the high emissivity reference plate.

[0008] Based on the Stefan-Boltzmann law, a simultaneous equation is established for the equivalent radiation of the two sets of reference plates and the equivalent radiation of the target before and after changing the surface temperature of the high emissivity reference plate. The equivalent emissivity and the true surface temperature of the target under test are then solved by the simultaneous equation.

[0009] The oil-free and dry metal surface of the target under inspection is set as the dry control area, and the equivalent emissivity of the target in the dry control area is obtained.

[0010] Furthermore, the difference between the target equivalent emissivity in the dry control area and the target equivalent emissivity of the inspected target is marked as the reflection coefficient difference, and the difference between the target's actual surface temperature and the target's apparent temperature is marked as the temperature underestimation. The ambient temperature parameter of the environment where the inspected target is located is obtained. When the reflection coefficient difference and the temperature underestimation of the inspected target are both greater than zero, and the target's actual surface temperature is greater than the ambient temperature parameter, the inspected target is marked as a suspected leakage area.

[0011] Furthermore, the surface temperature of the high-emissivity reference plate was measured and marked as the first reference plate temperature. Based on the Stefan-Boltzmann law, the equivalent radiation of the high-emissivity reference plate was calculated, as follows:

[0012] L ref,1 =σ(T A +273.15) 4 ;

[0013] Where L ref,1 The equivalent radiation of the first reference plate, σ is the Stefan-Boltzmann constant, and T A This is the temperature of the first reference plate.

[0014] Furthermore, an infrared thermal imager acquires the first frame of the target under inspection, and this first frame is marked as the first target temperature map. The target under inspection is divided into n regions from the first target temperature map, and the apparent temperature of the first target in each region is read. Based on the apparent temperature of the first target, the equivalent radiation of the first target is calculated according to the Stefan-Boltzmann law. The specific calculation method is: Equivalent radiation of the first target = σ(apparent temperature of the first target + 273.15). 4 .

[0015] Furthermore, after changing the surface temperature of the high emissivity reference plate, the surface temperature of the high emissivity reference plate was measured again, and the surface temperature of the high emissivity reference plate measured this time was marked as the second reference plate temperature T. B And again, based on the Stefan-Boltzmann law and the temperature T of the second reference plate. B The equivalent radiation L of the second reference plate was calculated. ref,2 ;

[0016] After changing the surface temperature of the high emissivity reference plate, the second frame image of the target under inspection is acquired again by the infrared thermal imager and marked as the second target temperature map. The target under inspection is divided into n regions from the second target temperature map. The apparent temperature of the second target in each region is read and the equivalent radiation of the second target is calculated based on the Stefan-Boltzmann law according to the apparent temperature of the second target.

[0017] The number of regions divided into the inspected target in the second instance is the same as the number of regions divided into the inspected target in the first instance.

[0018] Furthermore, based on the Stefan-Boltzmann law, a simultaneous equation is established for the equivalent radiation of the first reference plate, the second reference plate, the first target, and the second target. The simultaneous equation consists of two equations, as follows:

[0019] L1=ɛ·σ(T s +273.15) 4 +(1-ɛ)·L ref,1 ;

[0020] L2=ɛ·σ(T s +273.15) 4 +(1-ɛ)·L ref,2 ;

[0021] Where L1 is the equivalent radiation of the first target, ɛ is the equivalent emissivity of the target and 0 < ɛ < 1, σ is the Stefan-Boltzmann constant, and T s For the target true surface temperature, L ref,1 Let L1 be the equivalent radiation of the first reference plate, (1-ɛ) be the target reflection coefficient, and L2 be the equivalent radiation of the second target. ref,2 Equivalent radiation for the second reference plate;

[0022] The equivalent emissivity ɛ of the target is obtained by solving a series of equations, as follows:

[0023] ɛ=1-(L2-L1) / (L ref,2 -L ref,1 );

[0024] Substitute the obtained target equivalent emissivity ɛ into L1=ɛ·σ(T) s +273.15) 4 +(1-ɛ)·L ref,1 The true surface temperature T of the target can be obtained by solving the problem. s The details are as follows:

[0025] ;

[0026] Output the target's equivalent emissivity α and the target's true surface temperature T s.

[0027] Furthermore, before changing the surface temperature of the high emissivity reference plate, the target equivalent radiation of the dry control area is calculated, and the target equivalent radiation of the dry control area is marked as the third target equivalent radiation;

[0028] After changing the surface temperature of the high emissivity reference plate, the target equivalent radiation in the dry control area was calculated again and marked as the fourth target equivalent radiation.

[0029] The equivalent emissivity of the target in the dry control area was calculated based on the equivalent radiation of the third target and the equivalent radiation of the fourth target, as follows:

[0030] ɛ d =1-(L4-L3) / (L ref,2 -L ref,1 );

[0031] Among them, ɛ d L4 represents the equivalent emissivity of the target in the dry control area, L5 represents the equivalent radiation of the fourth target, and L3 represents the equivalent radiation of the third target.

[0032] Furthermore, the target reflection coefficient is calculated based on the target's equivalent emissivity ɛ, specifically: 1-ɛ=W, where W is the target reflection coefficient;

[0033] Based on the equivalent emissivity α of the target in the dry control area d The reflection coefficient of the dry area is calculated as follows: 1-ɛ d =W d W d The reflectance coefficient of the dry area;

[0034] Subtract the reflectance of the dry area from the reflectance of the target being inspected. d The resulting difference is labeled as the reflection coefficient difference.

[0035] When the difference in reflectance coefficient of the i-th region of the inspected target is greater than 0, the underestimation of temperature is greater than 0, and the actual surface temperature of the target is greater than the ambient temperature parameter, the i-th region of the inspected target is marked as a suspected leakage region, and all suspected leakage regions are combined into a suspected leakage region set.

[0036] Furthermore, a schematic diagram of the hydraulic system circuit of the press was obtained. The schematic diagram of the hydraulic system circuit of the press marked the location and name of physical parts such as pump stations, valves, pipelines, and oil cylinders. Each suspected leakage area in the set of suspected leakage areas was mapped to the physical location of the hydraulic system circuit diagram of the press.

[0037] Furthermore, a leak location list is generated, in which the name of the corresponding part of each suspected leak area is listed line by line, and the target equivalent emissivity, target true surface temperature, temperature underestimation, target reflection coefficient and reflection coefficient difference are listed for that part.

[0038] If the leak location list contains at least one suspected leak area, the hydraulic system of the press is determined to have an external leak. If the leak location list is empty, the hydraulic system of the press is determined to have no external leak.

[0039] Compared with existing technologies, it has the following advantages:

[0040] This paper proposes a method for detecting oil leaks in the hydraulic system of a press. Through a combined design of controllable background reflection, radiation inversion, and comparative verification, it addresses the core pain points of traditional infrared thermal imaging in press hydraulic systems. Firstly, this method overcomes the limitation of traditional infrared thermal imaging relying on fixed empirical emissivity, achieving accurate inversion of target radiation characteristics with true temperature. Traditional detection methods often suffer from temperature underestimation and hotspot obscuration due to their inability to adapt to dynamic apparent emissivity changes caused by oil film. This method, however, places a high-emissivity reference plate next to the target under inspection, altering its surface temperature to obtain two sets of equivalent radiation data for the reference plate and the target. Then, based on the Stefan-Boltzmann law, a simultaneous equation is established to directly solve for the target's equivalent emissivity and true surface temperature. This process does not require preset emissivity, effectively eliminating interference from environmental reflected radiation and accurately restoring the temperature of leak hotspots obscured by the oil film, avoiding missed detections caused by temperature misjudgment in traditional techniques.

[0041] By setting up a dry control zone, the objective quantification of leak detection is achieved, eliminating the reliance on subjective human intervention in traditional detection. This method designates the oil-free and dry metal surface of the target as the dry control zone, simultaneously calculating its equivalent emissivity. Then, by comparing the difference in reflection coefficients between the target and the dry control zone, the impact of the oil film on surface reflection characteristics is quantified. Combining the underestimation of the target's true surface temperature with its apparent temperature, and using a reflection coefficient difference greater than zero, a temperature underestimation greater than zero, and a true surface temperature greater than the ambient temperature as the judgment criteria, the screening of suspected leak areas has a clear physical basis. This avoids judgment biases caused by experience differences in traditional manual thermal imaging, improving the objectivity and consistency of the detection results.

[0042] This method possesses system-level leak location and data traceability capabilities, adapting to the actual maintenance needs of industrial sites. Traditional detection methods can only roughly indicate abnormal areas, making it difficult to accurately pinpoint specific components of the hydraulic system. This solution, however, generates a leak location list by mapping suspected leak areas to physical components such as pumps, valves, pipelines, and cylinders in the hydraulic system circuit diagram of the press. The list not only includes the names of each suspected component but also records key parameters such as the target's equivalent emissivity, the target's true surface temperature, and the underestimation of temperature. This clearly identifies the leak location and provides complete data support for subsequent fault analysis and maintenance, overcoming the limitations of traditional detection methods. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0044] Figure 2 This is a schematic diagram of the process for solving simultaneous equations in this invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] First Embodiment

[0047] This application provides a method for detecting oil leakage in a hydraulic system based on a press.

[0048] As an embodiment of this application, the method specifically includes:

[0049] A high emissivity reference plate is placed next to the target under inspection, so that the infrared radiation of the high emissivity reference plate is projected onto the surface of the target under inspection. The high emissivity reference plate is a material with an emissivity close to 1. The surface temperature of the high emissivity reference plate is obtained and the equivalent radiation of the reference plate is calculated according to the Stefan-Boltzmann law. The apparent temperature of the target under inspection is obtained and the equivalent radiation of the target under inspection is calculated according to the Stefan-Boltzmann law.

[0050] Change the surface temperature of the high emissivity reference plate, and then recalculate the reference plate equivalent radiation and the target equivalent radiation of the inspected target after changing the surface temperature of the high emissivity reference plate.

[0051] Based on the Stefan-Boltzmann law, a simultaneous equation is established for the equivalent radiation of the two sets of reference plates and the equivalent radiation of the target before and after changing the surface temperature of the high emissivity reference plate. The equivalent emissivity and the true surface temperature of the target under test are then solved by the simultaneous equation.

[0052] The oil-free and dry metal surface of the target under inspection is set as the dry control area, and the equivalent emissivity of the target in the dry control area is obtained.

[0053] Second Embodiment

[0054] As a second embodiment of this application, this embodiment is implemented based on the first embodiment. Please refer to [link / reference]. Figure 1 The method provided in this embodiment includes the following steps:

[0055] Step 1: Use a thermometer to directly measure the ambient temperature of the target location, such as the hydraulic system of the press, and record the measured temperature as the ambient temperature parameter.

[0056] A high emissivity reference plate is placed next to the target being inspected, such as near the joints, valve bodies, or cylinder ports of a press's hydraulic system. The infrared radiation from the reference plate is projected onto the target surface at a suitable angle, such as a non-perpendicular angle, so that the reflected radiation from the reference plate is captured by the infrared thermal imager lens. In other words, when the thermal imager photographs the target, it receives the reflected infrared radiation from the reference plate. Specifically, emissivity measures an object's ability to emit infrared radiation close to that of a blackbody, i.e., an ideal radiator with an emissivity of 1. The term "emissivity" refers to the physical quantity of light intensity. A high emissivity reference plate is a plate with an emissivity close to 1. In this example, a high emissivity reference plate with an emissivity above 0.95 is selected. A high emissivity reference plate approximates a blackbody, stably and predictably emitting infrared radiation. Its own radiation characteristics, such as the quantitative relationship between emissivity, temperature, and radiation, are known and stable. Placing the reference plate beside the target under inspection, which can be observed for reflection, ensures that the target reflects the radiation from the high emissivity reference plate, so that the target radiation acquired by the thermal imager includes the reflection contribution from the reference plate with known emissivity and temperature. Subsequently, by changing the temperature of the high emissivity reference plate, two sets of target radiation data under different reflected radiation backgrounds can be obtained.

[0057] The surface temperature of the high emissivity reference plate was measured using a contact thermometer, and this measured surface temperature was marked as the first reference plate temperature T. A ;

[0058] According to the Stefan-Boltzmann law, the equivalent radiation of the high-emissivity reference plate is calculated as follows: L ref,1 =σ(T A +273.15) 4 TA L is the temperature of the first reference plate. ref,1 Let σ be the equivalent radiation of the first reference plate, and σ be the Stefan-Boltzmann constant. Specifically, the Stefan-Boltzmann law describes the physical law that radiative exitance is proportional to the fourth power of thermodynamic temperature, and the zero point of thermodynamic temperature is absolute zero. The temperature corresponding to absolute zero is -273.15 degrees Celsius. If we directly use the Celsius temperature, since the zero point of the Celsius temperature is not absolute zero, the physical relationship that radiation is strictly proportional to the fourth power of temperature cannot be satisfied, and the formula will not hold. Therefore, we must convert the temperature of the first reference plate (Celsius temperature) to Kelvin temperature before substituting it into the Stefan-Boltzmann law to accurately calculate the equivalent radiation of the reference plate.

[0059] The first frame image of the target under inspection is acquired by a radiation-thermometric infrared thermal imager and marked as the first target temperature map. The target is then divided into n regions from the first target temperature map. The apparent temperature of each region is read, and the equivalent radiation of the first target is calculated based on the apparent temperature. Specifically, the target in the first target temperature map can be divided into n regions according to a certain number of pixels. Since different targets require different regions, specific division rules are set according to the actual situation. After dividing into n regions, the apparent temperature of the target region can be directly read from the display temperature of the thermal imager under default settings. Then, based on the apparent temperature, the equivalent radiation of the target region is calculated using the Stefan-Boltzmann law. The calculation method for the equivalent radiation of the target is the same as that for the reference plate, i.e., L = σ × (target apparent temperature + 273.15). 4 Where L is the target equivalent radiation, the temperature parameter is the target apparent temperature, and the calculation method of the second target equivalent radiation in the subsequent steps is the same as that of the first target equivalent radiation. The temperature parameter used in the calculation of the second target equivalent radiation is the second target apparent temperature.

[0060] Specifically, the target apparent temperature is the temperature value directly displayed by the radiation-thermometric infrared thermal imager on the inspected part of the hydraulic system of the press under the default emissivity setting. However, due to the ultra-thin oil film spread caused by the wet and cold metal surface and surfactants, which alters the local apparent emissivity, this temperature is not the true surface temperature of the target. It is merely an apparent misjudgment result inverted by the thermal imager based on the default emissivity. The target apparent temperature serves as both a benchmark for the degree of misjudgment, allowing subsequent calculations of the temperature underestimation caused by shading to quantify the impact of oil film shading, and an input for radiation conversion, since thermal imagers often directly input... To obtain the temperature, the target's apparent temperature needs to be converted using the Stefan-Boltzmann law to obtain the target's equivalent radiation, which has the same dimensions as the reference plate's equivalent radiation. The target's equivalent radiation represents the total radiative energy per unit area per unit time when the target radiates at the thermal imager's default emissivity. The target's equivalent radiation obtained in this step is used as the first set of target radiation inputs. Subsequent steps, after changing the reference plate temperature, will obtain the second set of target equivalent radiation. Combining the two sets of equivalent radiation from the reference plate, the thermal imaging energy conservation equation can be solved to obtain the target's true surface temperature and equivalent emissivity, thus eliminating oil film shading interference.

[0061] Step Two: Change the surface temperature of the high emissivity reference plate by flipping it over (utilizing the thermal differences between different surfaces of the reference plate), rapid heating (e.g., using a small electric heating device), or natural heat dissipation (allowing the reference plate to slowly change with the ambient temperature). After changing the surface temperature of the high emissivity reference plate, measure the surface temperature of the high emissivity reference plate again using a contact thermometer, and mark the measured surface temperature of the high emissivity reference plate as the second reference plate temperature T. B And again, based on the Stefan-Boltzmann law and the temperature T of the second reference plate. B The equivalent radiation L of the second reference plate was calculated. ref,2 Specifically, by providing a second set of reference plates with altered reflective background radiation, subsequent steps can be performed using the initial reflective background L. ref,1 With new reflective background L ref,2 By comparing the results, the unknown terms of the target's own emitted radiation are eliminated by solving the simultaneous equations, thereby inverting the equivalent emissivity and true surface temperature of the inspected target.

[0062] After changing the surface temperature of the high emissivity reference plate, a second frame image of the target under inspection is acquired again using a radiation thermometry infrared thermal imager and marked as the second target temperature map. The target under inspection is divided into n regions from the second target temperature map, and the apparent temperature of the second target in each region is read. The equivalent radiation of the second target is calculated based on the apparent temperature of the second target. Specifically, when acquiring the image of the target under inspection for the second time, the parameters of the thermal imager and the position and attitude of the target under inspection must remain completely unchanged. At the same time, the number of n regions into which the target under inspection is divided for the second time must be equal to the number of n regions into which the target under inspection is divided for the first time. Finally, the equivalent radiation of the second target is calculated. The equivalent radiation of the second target is obtained by acquiring the radiation data of the target under inspection in the new reflection background. It forms two sets of radiation measurements with the equivalent radiation of the first target, which are the same target but with different reflection backgrounds. This provides the necessary second set of target inputs for the two-equation inversion in the subsequent steps, ensuring that the simultaneous equations are solvable.

[0063] Step 3: Please refer to Figure 2 Since the radiation of the target under test mainly consists of its own emitted radiation and ambient radiation mainly reflected from the reference plate, the following equation is established for the equivalent radiation of the first target:

[0064] L1=ɛ·σ(T s +273.15) 4 +(1-ɛ)·L ref,1 ;

[0065] Where L1 is the equivalent radiation of the first target, ɛ is the equivalent emissivity of the target, 0 < ɛ < 1, σ is the Stefan-Boltzmann constant, and T s The target is the actual surface temperature, 273.15 is the conversion value of Celsius to Kelvin, L ref,1 Let (1-ɛ) be the equivalent radiation of the first reference plate, and (1-ɛ) be the target reflection coefficient.

[0066] Specifically, the radiation detected by the infrared thermal imager consists of two parts: the target's own emitted radiation and the ambient radiation mainly reflected from a high-emissivity reference plate. Therefore, the above equation is established for the equivalent radiation of the first target, where the target's equivalent emissivity α is a physical quantity reflecting how close the actual infrared radiation capability of the target is to an ideal blackbody, and the target's true surface temperature T... s The surface temperature of the target when it is not obscured by an oil film is its actual surface temperature. The target reflectivity (1-ɛ) represents the ability of the target surface to reflect external radiation. The first equivalent radiation of the target detected by the thermal imager in the first target temperature map is equal to the target's equivalent emissivity ɛ and the target's true surface temperature T. sThe sum of the self-emitted radiation and the equivalent radiation reflected by the target through the reference plate and the first reference plate (with the target's reflectivity coefficient (1-ɛ)) is used to quantify the contribution of the target's self-emitted radiation and reflected environmental radiation to the thermal imager's detection results. Subsequently, combining this with another set of similar equations after changing the reference plate temperature in the second target temperature map, the unknown term of self-emitted radiation can be eliminated, thus revealing the true surface temperature T of the target affected by the oil film. s The equivalent emissivity α of the target is used to eliminate the misleading effect of thermal oil film masking on temperature detection, providing a basis for reliably determining whether there is external leakage in the hydraulic system. Thermal oil film masking refers to the phenomenon that when there is a wet and cold metal surface in the hydraulic system of a press and there is a surfactant, the leaked hydraulic oil will spread in the form of an ultra-thin oil film. This ultra-thin oil film will significantly reduce the apparent emissivity of the local area and enhance the reflectivity of the ambient radiation. As a result, when the infrared thermal imager inverts the temperature of the area, it will systematically underestimate its true temperature, so that the micro-leakage area is faded or even masked in the thermal image, interfering with the detection of external leakage in the hydraulic system.

[0067] Simultaneously, the following equation is established for the equivalent radiation of the second target:

[0068] L2=ɛ·σ(T s +273.15) 4 +(1-ɛ)·L ref,2 ;

[0069] Where L2 is the equivalent radiation of the second target, L ref,2 Equivalent radiation for the second reference plate;

[0070] Solving the two equations for the equivalent radiation of the first and second targets simultaneously yields the target's equivalent emissivity ɛ, as follows:

[0071] ɛ=1-(L2-L1) / (L ref,2 -L ref,1 );

[0072] Substitute the ɛ obtained after solving the simultaneous equations into L1=ɛ·σ(T) s +273.15) 4 +(1-ɛ)·L ref,1 Solve for the true surface temperature T of the target s The details are as follows:

[0073] ;

[0074] Finally, the equivalent emissivity α and the true surface temperature T of the target can be obtained by solving the above equations simultaneously. sSpecifically, the method proposes dual reflection and two-equation inversion, achieving self-consistent radiation inversion by simultaneously eliminating variables from two sets of on-site radiation measurements. This directly solves for the target's true radiation characteristics and temperature, eliminating temperature interference from the thermal imaging oil film shielding effect. The calculated equivalent emissivity α and true surface temperature T of the target are then used to determine these parameters. s It can overcome the limitations of traditional thermal imaging that relies on empirical emissivity, directly reproducing real hotspots hidden by oil films. The target's equivalent emissivity α can be compared with the emissivity of a dry control area in the same scene to determine whether the target exhibits radiation anomalies due to the oil film, and the target's true surface temperature T. s It can clearly identify the actual temperature level at the leak point, and combine this with logic such as whether it is higher than the ambient temperature to reliably determine whether there is an external leak in the hydraulic system. This provides a core basis for subsequent leak location and conclusion output, thereby eliminating the misleading effect of oil film shielding on detection.

[0075] Within the field of view of the thermal imager, select an oil-free and dry metal surface from the target under inspection. This oil-free and dry metal surface is in the same environmental conditions as the target under inspection, such as the joints and valve bodies of a hydraulic system, such as the same temperature and humidity, and is not affected by leaking oil film and surfactants. Mark this oil-free and dry metal surface as the dry control area.

[0076] Before changing the surface temperature of the high emissivity reference plate, the target equivalent radiation calculation steps described above are performed on the dry control area to obtain the target equivalent radiation of the dry control area, which is then labeled as the third target equivalent radiation. Similarly, after changing the surface temperature of the high emissivity reference plate, the target equivalent radiation of the dry control area is calculated again and labeled as the fourth target equivalent radiation. Based on the third and fourth target equivalent radiations, the target equivalent emissivity α of the dry control area is calculated. d =1-(L4-L3) / (L ref,2 -L ref,1 ), where ɛ d L4 represents the equivalent emissivity of the target in the dry control area, L3 represents the equivalent radiation of the fourth target, and L4 represents the equivalent radiation of the third target.

[0077] Specifically, the step of calculating the target equivalent radiation of the dry control area is synchronized with the process of calculating the target equivalent radiation of the inspected target; therefore, L in the calculation formula... ref,2 and L ref,1 The values ​​of L1 and L2 in the inspected target area are constant. L1 and L2 represent the equivalent radiation of areas where oil film leakage may exist, and these values ​​will change due to the thermal imaging oil film shielding effect. L3 and L4 in the dry control area represent the equivalent radiation of an oil-free and dry metal surface in the same image frame, reflecting the inherent radiation characteristics of the metal surface when there is no oil film interference. Therefore, after substituting into the formula, the equivalent emissivity α of the inspected target and the equivalent emissivity α of the dry control area are... dThere will be differences, and these differences are the basis for subsequent steps to determine whether the oil film causes abnormal emissivity in the tested area.

[0078] Step 4: Calculate the target reflection coefficient based on the target equivalent emissivity ɛ, specifically: 1-ɛ=W, where W is the target reflection coefficient. The target reflection coefficient is a dimensionless value that reflects the ability of the surface of the inspected target to reflect radiation from the external environment. The emissivity of an ideal blackbody is 1, meaning it emits completely and reflects almost nothing. The smaller the emissivity, the weaker the ability of the object to emit radiation. Therefore, the lower the target equivalent emissivity ɛ, the higher the target reflection coefficient, indicating that the reflection characteristics of the surface of the inspected target are closer to those of a mirror. This is completely consistent with the thermal imaging oil film shielding effect after the ultra-thin oil film is spread, which reduces the emissivity and enhances the reflection of the surface of the inspected target.

[0079] Similarly, based on the equivalent emissivity α of the target in the dry control area d The reflection coefficient of the dry area is calculated as follows: 1-ɛ d =W d W d The dry area reflectance is a dimensionless value that reflects the ability of a metal surface to reflect environmental radiation when there is no oil film interference. The dry area reflectance serves as a benchmark for reflectance when there is no oil film interference and is used to compare with the reflectance of the target area to determine whether the target area has abnormal reflectance due to the oil film.

[0080] Subtract the dry area reflectance W from the target reflectance W. d The difference obtained is then labeled as the reflection coefficient difference. The reflection coefficient difference can quantify the difference between the reflectivity of the target area and the reflectivity of the dry area. It is used to determine whether the target under test is more likely to reflect radiation than the dry area due to the oil film. If the reflection coefficient difference is >0, it means that the target area is more capable of reflecting external radiation than the dry metal without an oil film. This is consistent with the effect of enhanced surface reflection after the oil film is spread in an ultra-thin manner. Therefore, the reflection coefficient difference can be used to determine whether the target area has abnormal reflection characteristics due to the oil film.

[0081] Obtain the first target apparent temperature, and then set the target's true surface temperature T. s The difference obtained by subtracting the apparent temperature of the first target is marked as the temperature underestimation. The temperature underestimation reflects the degree of temperature underestimation caused by the thermal imaging oil film shielding effect. If the temperature underestimation is >0, it means that the actual temperature of the target is higher than the temperature shown by the thermal imager, which verifies the phenomenon that the shielding effect makes the leakage hot spot faded.

[0082] When the difference in reflectance coefficient of the i-th region of the inspected target is greater than 0, the underestimation of temperature is greater than 0, and the actual surface temperature of the target is greater than the ambient temperature parameter, the i-th region of the inspected target is marked as a suspected leakage region, and all suspected leakage regions are combined into a suspected leakage region set.

[0083] Specifically, when the difference in reflectance coefficient of the i-th region of the inspected target is greater than 0, it indicates that the reflectance coefficient of the target is greater than that of the dry region. Since the oil film in the target region is closer to the mirror surface, it conforms to the radiation effect of the ultra-thin oil film spreading. When the temperature underestimation is greater than 0, it indicates that the actual temperature is higher than the apparent temperature. This indicates that there is a temperature underestimation caused by the thermal oil film shielding effect. The real hot spot is covered by the oil film. When the actual surface temperature of the target is greater than the ambient temperature parameter, it indicates that the actual temperature of the target is higher than the ambient temperature. This conforms to the physical rationality of the leak hot spot, that is, the characteristic that the local temperature will rise due to friction of the leaking oil or heat dissipation of the system. Therefore, the suspected leak area obtained based on these three parameter conditions can indicate that there is a high probability that the area is leaking oil, thereby avoiding missed or false detections caused by scene changes and improving the objectivity and reliability of leak identification.

[0084] Step 5: Obtain the hydraulic system circuit diagram of the press. The hydraulic system circuit diagram of the press marks the location and name of physical parts such as pump station, valve, pipeline, and oil cylinder. Map each suspected leakage area in the set of suspected leakage areas to the physical location on the hydraulic system circuit diagram of the press. For example, a certain suspected leakage area corresponds to a specific part such as the pump station outlet joint or the oil cylinder piston rod seal.

[0085] Generate a leak location list, listing the name of each suspected leak area and the corresponding part, as well as the target equivalent emissivity α, the target true surface temperature, the temperature underestimation, the target reflection coefficient, and the reflection coefficient difference for each part.

[0086] If the leak location list contains at least one location corresponding to a suspected leak area, it means that the leak location list is not empty. In this case, the hydraulic system of the press is determined to have an external leak, and all leak locations are clearly listed. If the leak location list is empty, the hydraulic system of the press is determined to have no external leak.

[0087] Specifically, the suspected leakage area is mapped to the physical location on the hydraulic system circuit diagram of the press, and the leakage location list is used to determine whether an oil leak has occurred. This intuitively and completely shows the three core issues of whether the hydraulic system is leaking oil, where the leak is located, and the extent of the leak, thus meeting the system-level testing requirements of the press hydraulic system.

[0088] The above embodiments are only used to illustrate the technical methods of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of the present invention without departing from the spirit and scope of the technical methods of the present invention.

Claims

1. A method for detecting oil leakage in a hydraulic system based on a press, characterized in that, include: A high emissivity reference plate is placed next to the target under inspection, so that the infrared radiation of the high emissivity reference plate is projected onto the surface of the target under inspection. The high emissivity reference plate is a material with an emissivity close to 1. The surface temperature of the high emissivity reference plate is obtained and the equivalent radiation of the reference plate is calculated according to the Stefan-Boltzmann law. The apparent temperature of the target under inspection is obtained and the equivalent radiation of the target under inspection is calculated according to the Stefan-Boltzmann law. Change the surface temperature of the high emissivity reference plate, and then recalculate the reference plate equivalent radiation and the target equivalent radiation of the inspected target after changing the surface temperature of the high emissivity reference plate. Based on the Stefan-Boltzmann law, a simultaneous equation is established for the equivalent radiation of the two sets of reference plates and the equivalent radiation of the target before and after changing the surface temperature of the high emissivity reference plate. The equivalent emissivity and the true surface temperature of the target under test are then solved by the simultaneous equation. The oil-free and dry metal surface of the target under inspection is set as the dry control area, and the target equivalent emissivity of the dry control area is obtained. The difference between the target equivalent emissivity in the dry control area and the target equivalent emissivity of the inspected target is marked as the reflection coefficient difference. The difference between the target's actual surface temperature and the target's apparent temperature is marked as the temperature underestimation. The ambient temperature parameter of the environment where the inspected target is located is obtained. When the reflection coefficient difference and the temperature underestimation of the inspected target are both greater than zero, and the target's actual surface temperature is greater than the ambient temperature parameter, the inspected target is marked as a suspected leakage area. Based on the Stefan-Boltzmann law, a simultaneous equation is established for the equivalent radiation of the first reference plate, the second reference plate, the first target, and the second target. The simultaneous equation consists of two equations, as follows: L1= ·σ(T s +273.15) 4 +(1- )·L ref,1 ; L2= ·σ(T s +273.15) 4 +(1- )·L ref,2 ; Where L1 is the equivalent radiation of the first target, The target equivalent emissivity and 0 < <1, σ is the Stefan-Boltzmann constant, T s For the target true surface temperature, L ref,1 For the equivalent radiation of the first reference plate, (1- L1 is the target reflection coefficient, L2 is the equivalent radiation of the second target, and L3 is the reflection coefficient of the target. ref,2 Equivalent radiation for the second reference plate; The equivalent emissivity of the target is obtained by solving a series of equations. The details are as follows: =1-(L2-L1) / (L ref,2 -L ref,1 ); The target equivalent emissivity obtained after solving Substitute L1= ·σ(T s +273.15) 4 +(1- )·L ref,1 The true surface temperature T of the target can be obtained by solving the problem. s The details are as follows: ； Output target equivalent emissivity and the target true surface temperature T s .

2. The method for detecting oil leakage in a hydraulic system based on a press according to claim 1, characterized in that, include: The surface temperature of the high-emissivity reference plate was measured and marked as the first reference plate temperature. Based on the Stefan-Boltzmann law, the equivalent radiation of the high-emissivity reference plate was calculated. The specific calculation method is as follows: L ref,1 =σ(T A +273.15) 4 ; Where L ref,1 The equivalent radiation of the first reference plate, σ is the Stefan-Boltzmann constant, and T A This is the temperature of the first reference plate.

3. The method for detecting oil leakage in a hydraulic system based on a press according to claim 2, characterized in that, include: The first frame image of the target under inspection is acquired using an infrared thermal imager and marked as the first target temperature map. The target under inspection is divided into n regions from the first target temperature map, and the apparent temperature of the first target in each region is read. Based on the apparent temperature of the first target, the equivalent radiation of the first target is calculated according to the Stefan-Boltzmann law. The specific calculation method is: Equivalent radiation of the first target = σ(apparent temperature of the first target + 273.15). 4 .

4. The method for detecting oil leakage in a hydraulic system based on a press according to claim 3, characterized in that, include: After changing the surface temperature of the high emissivity reference plate, the surface temperature of the high emissivity reference plate was measured again, and this measured surface temperature was marked as the second reference plate temperature T. B And again, based on the Stefan-Boltzmann law and the temperature T of the second reference plate. B The equivalent radiation L of the second reference plate was calculated. ref,2 ; After changing the surface temperature of the high emissivity reference plate, the second frame image of the target under inspection is acquired again by the infrared thermal imager and marked as the second target temperature map. The target under inspection is divided into n regions from the second target temperature map. The apparent temperature of the second target in each region is read and the equivalent radiation of the second target is calculated based on the Stefan-Boltzmann law according to the apparent temperature of the second target. The number of regions divided into the inspected target in the second instance is the same as the number of regions divided into the inspected target in the first instance.

5. The method for detecting oil leakage in a hydraulic system based on a press according to claim 1, characterized in that, include: Before changing the surface temperature of the high emissivity reference plate, the target equivalent radiation of the dry control area is calculated, and the target equivalent radiation of the dry control area is marked as the third target equivalent radiation; After changing the surface temperature of the high emissivity reference plate, the target equivalent radiation in the dry control area was calculated again and marked as the fourth target equivalent radiation. The equivalent emissivity of the target in the dry control area was calculated based on the equivalent radiation of the third target and the equivalent radiation of the fourth target, as follows: d =1-(L4-L3) / (L ref,2 -L ref,1 ); in, d L4 represents the equivalent emissivity of the target in the dry control area, L5 represents the equivalent radiation of the fourth target, and L3 represents the equivalent radiation of the third target.

6. The method for detecting oil leakage in a hydraulic system based on a press according to claim 5, characterized in that, include: Target equivalent emissivity based on the inspected target The target reflectance coefficient is calculated as follows: 1- =W, where W is the target reflection coefficient; Based on the equivalent emissivity of the target in the dry control area d The reflection coefficient of the dry area is calculated as follows: 1- d =W d W d The reflectance coefficient of the dry area; Subtract the reflectance of the dry area from the reflectance of the target being inspected. d The resulting difference is labeled as the reflection coefficient difference. When the difference in reflectance coefficient of the i-th region of the inspected target is greater than 0, the underestimation of temperature is greater than 0, and the actual surface temperature of the target is greater than the ambient temperature parameter, the i-th region of the inspected target is marked as a suspected leakage region, and all suspected leakage regions are combined into a suspected leakage region set.

7. The method for detecting oil leakage in a hydraulic system based on a press according to claim 6, characterized in that, include: The hydraulic system circuit diagram of the press machine was obtained. The diagram marked the location and name of physical parts such as pump stations, valves, pipelines, and oil cylinders. Each suspected leakage area in the set of suspected leakage areas was mapped to the physical location on the hydraulic system circuit diagram of the press machine.

8. The method for detecting oil leakage in a hydraulic system based on a press according to claim 7, characterized in that, include: Generate a leak location list, listing the name of each suspected leak area and the corresponding part for each part, and listing the target equivalent emissivity, target true surface temperature, temperature underestimation, target reflection coefficient and reflection coefficient difference for that part. If the leak location list contains at least one suspected leak area, the hydraulic system of the press is determined to have an external leak. If the leak location list is empty, the hydraulic system of the press is determined to have no external leak.

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