Tunnel entrance lighting adaptive control method

Abstract

The application discloses a tunnel entrance lighting adaptive control method, comprising: acquiring the atmospheric transmissivity and the atmospheric light curtain brightness of a tunnel entrance, calculating the scattering efficiency compensation factor according to the atmospheric transmissivity and the scattering correction coefficient; combining the scattering efficiency compensation factor, the threshold brightness coefficient, the atmospheric transmissivity, the light curtain reduction factor, the external background brightness and the atmospheric light curtain brightness to calculate the entrance section threshold brightness target value; determining the entrance section threshold brightness of different working conditions according to the entrance section threshold brightness target value, and determining the entrance section threshold brightness of the current working condition; setting the spatial length of each lighting partition of the tunnel entrance, combining the entrance section threshold brightness and the middle section brightness of the transition section to calculate the transition section equivalent gradient; taking the transition section equivalent gradient as a constraint, constructing the brightness curve of the tunnel entrance by using an interpolation method according to the target brightness of each lighting partition boundary point; and discretely sampling the brightness curve based on the lamp installation position to obtain a target brightness instruction sequence for controlling the tunnel lighting.

Description

Technical Field

[0001] This invention relates to the field of light source control technology in response to determined parameters, and more specifically to an adaptive control method for tunnel entrance lighting. Background Technology

[0002] Due to their unique enclosed spatial structure, highway tunnels exhibit a significant difference in brightness between the inside and outside. Drivers entering a tunnel must undergo a visual adaptation process from a high-brightness environment to a low-brightness environment. If this transition is not handled properly, it can easily induce the "black hole effect"—that is, drivers near the tunnel entrance are unable to discern road conditions inside because their pupils have not yet completed their pupillary contraction adaptation—thus becoming a major cause of traffic accidents.

[0003] Therefore, the current "Detailed Specifications for Lighting Design of Highway Tunnels" (JTG / TD70 / 2-01) and related standards have clearly stipulated the requirements for tunnel entrance lighting. These specifications require the establishment of approach, entrance, and transition sections at the tunnel entrance. The lighting brightness of each section is determined by referring to tables based on the background brightness outside the tunnel and the design driving speed. The dimming commands for the luminaires are then calculated using a fixed ratio after actual measurement with a luminance meter, forming a simple open-loop or single closed-loop control strategy. This technical approach is reasonable under standard operating conditions with clear weather and good visibility, but it has revealed several systemic defects in actual engineering operations, restricting the safety assurance capability of tunnel entrance lighting under complex weather conditions.

[0004] Current control strategies, when sensing a decrease in ambient brightness outside the tunnel, tend to increase the illuminance at the tunnel entrance by increasing the power of the lamps to compensate for the driver's perceived insufficient brightness. The existing control logic uses the ambient brightness measured by a luminance meter as the sole input parameter, implicitly assuming that atmospheric transmittance is at an ideal value, meaning that light does not experience any attenuation or scattering as it travels through the air. However, when low-visibility weather occurs, such as smog, dust storms, or heavy rain, the concentration of suspended particulate matter in the atmosphere increases sharply, leading to a significant increase in the atmospheric extinction coefficient. The energy attenuation of light along its propagation path decreases exponentially according to Beer-Lambert's law.

[0005] Meanwhile, dense fog droplets exhibit strong Mie scattering characteristics for visible light. When lighting fixtures illuminate the fog at high power, the scattered light accumulates significantly in the driver's line of sight, forming a bright white curtain covering the entire field of vision (i.e., the "light curtain effect"). This light curtain not only fails to improve the driver's ability to recognize the road surface and obstacles, but also further deteriorates the visual contrast of targets due to the obscuring effect of its high-brightness background, creating a more dangerous visual closure than having the lights off. Existing control systems lack the ability to quantitatively assess scattering risks and lack corresponding active peak brightness suppression logic, making it impossible to achieve a reasonable trade-off between the need for increased brightness and the need for scattering suppression in foggy weather. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes an adaptive control method for tunnel entrance lighting, which can ensure driver visual safety while avoiding the light curtain effect. The specific technical solution is as follows: An adaptive control method for tunnel entrance lighting is provided. In a first implementable manner, it includes: The atmospheric transmittance and atmospheric light curtain brightness at the tunnel entrance are obtained. The scattering efficiency compensation factor is calculated based on the atmospheric transmittance and scattering correction coefficient. The specific calculation formula is as follows: ; in, This is the scattering efficiency compensation factor. Atmospheric transmittance. This is the scattering correction factor; Combining the scattering efficiency compensation factor, threshold brightness coefficient, atmospheric transmittance, light curtain reduction factor, external background brightness, and atmospheric light curtain brightness, the target value of the threshold brightness at the tunnel entrance is calculated. The specific calculation formula is as follows: ; in, The threshold brightness target value for the entrance segment. The threshold brightness coefficient, For external background brightness without atmospheric attenuation, The light curtain reduction factor. The brightness of the atmospheric light curtain superimposed along the line of sight when the driver observes from a certain distance from the tunnel entrance; Based on the target value of the threshold brightness of the entrance section, determine the threshold brightness of the entrance section corresponding to different working conditions, and determine the threshold brightness of the entrance section under the current working condition of the tunnel entrance; The spatial length of each lighting zone at the tunnel entrance is set, and the equivalent gradient of the transition section is calculated by combining the threshold brightness of the entrance section and the brightness of the middle section of the transition section. Using the equivalent gradient of the transition section as a constraint, and based on the target brightness corresponding to the boundary points of each lighting zone at the tunnel entrance, an interpolation method is used to construct the brightness curve of the tunnel entrance. The brightness curve is sampled and discretized based on the installation location of the lighting fixtures inside the tunnel entrance to obtain the corresponding target brightness command sequence for lighting control.

[0007] In the second feasible method, in conjunction with the first feasible method, the atmospheric transmittance at the tunnel entrance is obtained, including: Atmospheric visibility at the tunnel entrance is collected, and the atmospheric extinction coefficient is calculated by combining it with the set minimum brightness contrast threshold. The atmospheric transmittance is determined based on the atmospheric extinction coefficient and a set reference distance.

[0008] In the third feasible method, in conjunction with the first feasible method, the brightness of the atmospheric light curtain at the tunnel entrance is obtained, including: Atmospheric visibility and sky background brightness at the tunnel entrance are collected, and the atmospheric extinction coefficient is calculated based on the atmospheric visibility and the set minimum brightness contrast threshold. The brightness of the atmospheric curtain is determined based on the atmospheric extinction coefficient, the brightness of the sky background, and the actual observation path length.

[0009] In conjunction with the first feasible method, the fourth feasible method determines the threshold brightness of the inlet section under different operating conditions based on the target value of the threshold brightness of the inlet section, including: Obtain the visual risk index corresponding to the tunnel entrance, and calculate the peak brightness cutoff value corresponding to the extremely low visibility condition by combining the peak brightness of the entrance section lighting under standard clear weather conditions. By combining the peak brightness cutoff value and the target value of the inlet segment threshold brightness, the inlet segment threshold brightness corresponding to different operating conditions is determined, specifically as follows: ; in, The threshold brightness of the inlet segment. The threshold brightness target value for the entrance segment. As a visual risk index, This serves as the normalized upper limit for the visual risk index. This is the critical threshold for the visual risk index. Atmospheric visibility, This is the critical threshold for atmospheric visibility. This represents the peak brightness of the entrance section lighting under standard clear weather conditions. This represents the peak compression ratio.

[0010] Combining the fourth feasible method, the fifth feasible method obtains the visual risk index corresponding to the tunnel entrance, including: The visual contrast is calculated based on the atmospheric light curtain brightness, atmospheric extinction coefficient, and target background brightness, combined with the set inherent contrast and target background brightness. Based on visual contrast and minimum contrast threshold, safe parking sight distance and atmospheric visibility, atmospheric light curtain brightness and external background brightness, the degree of visual contrast attenuation, sight distance adequacy and relative intensity of the light curtain are calculated respectively. The visual risk index of the tunnel entrance is assessed by evaluating the degree of visual contrast attenuation, the adequacy of the viewing distance, and the relative intensity of the light curtain.

[0011] In conjunction with the first feasible method, the sixth feasible method sets the spatial length of each lighting zone, including: The fixed space length corresponding to each lighting zone is determined based on the tunnel's design speed, and the visual risk index corresponding to the tunnel entrance is obtained. Based on the fixed space length corresponding to each lighting zone, and combined with the set risk elasticity coefficient and visual risk index of each lighting zone, the space length corresponding to each lighting zone is calculated.

[0012] In the seventh feasible method, in conjunction with the first feasible method, an interpolation method is used to construct the brightness curve corresponding to the tunnel entrance, including: When the equivalent gradient of the transition segment is lower than the minimum brightness gradient threshold, a brightness step with a certain spatial width is inserted at the brightness curve corresponding to the end of the transition segment.

[0013] In conjunction with the first feasible method, the eighth feasible method employs an interpolation method to construct the brightness curve corresponding to the tunnel entrance, including: Based on the driver's physiological accommodation limit, static sensitivity, and real-time speed, the maximum allowable value of the brightness gradient at different locations at the tunnel entrance is calculated. Using the maximum allowable value of the brightness gradient and the equivalent gradient of the transition section as constraints, the brightness curve of the tunnel entrance is constructed by interpolation based on the target brightness corresponding to the boundary points of each lighting zone at the tunnel entrance.

[0014] In conjunction with the first feasible method, the ninth feasible method employs an interpolation method to construct the brightness curve corresponding to the tunnel entrance, including: The brightness curve corresponding to the tunnel entrance is constructed using a piecewise cubic Hermite interpolation polynomial method.

[0015] In conjunction with the first feasible method, the tenth feasible method involves lighting control based on a target brightness command sequence, including: Based on the target brightness of the lighting fixtures in the target brightness command sequence and the road surface brightness of the lighting fixtures at rated power, the dimming ratio of the lighting fixtures is calculated. Based on the dimming ratio and target brightness, the lighting fixtures are controlled using a discrete PI control method according to the set closed-loop sampling period.

[0016] Beneficial Effects: The adaptive control method for tunnel entrance lighting of this invention, by introducing a scattering efficiency compensation factor calculated based on atmospheric transmittance and scattering correction coefficients, and combining atmospheric light curtain brightness and light curtain reduction factor, calculates the target value of the threshold brightness for the entrance section. This ensures that drivers have the same visual recognition ability under adverse weather conditions as in clear weather, guaranteeing driver visual safety. By adding a peak brightness upper limit cutoff to the target value of the entrance section threshold brightness, the threshold brightness of the entrance section under different operating conditions is determined, avoiding the light curtain effect caused by strong light irradiation under extreme conditions. Finally, using the equivalent gradient of the transition section calculated based on the spatial length of each lighting zone and the threshold brightness of the entrance section under the current operating conditions as a constraint, an interpolation method is used to construct the brightness curve of the tunnel entrance. By sampling and discretizing the brightness curve, the corresponding target brightness command sequence can be obtained for lighting control. This ensures that the driver's visual safety in the tunnel entrance area is guaranteed throughout the process under low visibility adverse weather conditions such as fog, haze, and heavy rain, while avoiding the light curtain effect caused by strong light irradiation under extreme conditions. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly described below. In all the drawings, the elements or parts are not necessarily drawn to scale.

[0018] Figure 1 This is a flowchart of an adaptive control method for tunnel entrance lighting provided in an embodiment of the present invention. Detailed Implementation

[0019] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0020] like Figure 1 The flowchart shown illustrates an adaptive control method for tunnel entrance lighting, which includes: Step 1: Obtain the atmospheric transmittance and atmospheric light curtain brightness at the tunnel entrance, and calculate the scattering efficiency compensation factor based on the atmospheric transmittance and scattering correction coefficient. Step 2: Calculate the target value of the threshold brightness of the tunnel entrance section by combining the scattering efficiency compensation factor, threshold brightness coefficient, atmospheric transmittance, light curtain reduction factor, external background brightness, and atmospheric light curtain brightness. Step 3: Determine the threshold brightness of the entrance section corresponding to different working conditions based on the target value of the threshold brightness of the entrance section, and determine the threshold brightness of the entrance section under the current working condition of the tunnel entrance; Step 4: Set the spatial length of each lighting zone at the tunnel entrance, and calculate the equivalent gradient of the transition section by combining the threshold brightness of the entrance section and the brightness of the middle section of the transition section. Step 5: Using the equivalent gradient of the transition section as a constraint, construct the brightness curve of the tunnel entrance using an interpolation method based on the target brightness corresponding to the boundary points of each lighting zone at the tunnel entrance. Step 6: Based on the installation position of the lighting fixtures inside the tunnel entrance, the brightness curve is sampled and discretized to obtain the corresponding target brightness command sequence for lighting control.

[0021] Specifically, firstly, existing methods can be used to obtain the atmospheric transmittance and atmospheric light curtain brightness at the tunnel entrance. For example, the atmospheric transmittance and atmospheric light curtain brightness at the tunnel entrance can be retrieved from remote sensing satellite images, or the atmospheric transmittance and atmospheric light curtain brightness at the tunnel entrance can be measured directly using a transmissometer and a luminance meter, respectively. Based on the atmospheric transmittance and a set scattering correction coefficient, the scattering efficiency compensation factor can be calculated, as shown in the following formula: ; in, This is the scattering efficiency compensation factor. Atmospheric transmittance. This is the scattering correction factor. The scattering correction factor reflects the degree to which fog concentration reduces the effective utilization of light. The scattering correction factor degenerates to 1 on clear days and decreases monotonically as atmospheric transmittance decreases, reflecting the weakening effect of fog on the efficiency of light utilization.

[0022] Then, under low visibility conditions, the external background brightness of the tunnel reaches the driver's eyes after atmospheric attenuation. Simultaneously, the brightness of the light curtain introduced by atmospheric scattering is also superimposed on the background brightness, reducing effective visual contrast. To ensure that drivers have the same visual recognition capability under adverse weather conditions as in clear weather, the target brightness of the entrance lighting can be redefined after considering fog scattering correction.

[0023] In this embodiment, the target value of the threshold brightness at the tunnel entrance section can be calculated by combining the scattering efficiency compensation factor, threshold brightness coefficient, atmospheric transmittance, light curtain reduction factor, external background brightness, and atmospheric light curtain brightness. The specific calculation formula is as follows: ; in, The threshold brightness target value for the entrance segment. The threshold brightness coefficient, For external background brightness without atmospheric attenuation, The light curtain reduction factor. This refers to the brightness of the atmospheric light curtain superimposed along the line of sight when the driver observes from a certain distance from the tunnel entrance.

[0024] The threshold brightness coefficient reflects the relationship between speed and required brightness, mapping the vehicle's current speed information to the baseline coefficient of the threshold brightness at the tunnel entrance. A scattering efficiency compensation factor compensates for the lighting brightness baseline required to maintain equivalent visual perception under low visibility conditions, ensuring driver visual safety in the tunnel entrance area during adverse weather conditions. Since the light curtain itself provides a certain increase in background brightness, the lighting fixtures do not need to compensate for this additional brightness. Introducing a light curtain reduction factor avoids excessive illumination that exacerbates scattering and triggers a light curtain effect. In this way, the physical process of light transmission in the real atmospheric medium can be fully incorporated into the control decision, fundamentally solving the systemic discrepancy between the lighting brightness setpoint and the driver's actual visual perception under adverse weather conditions.

[0025] Subsequently, to prevent a light curtain effect caused by strong light under extremely low visibility conditions, a peak brightness cap can be applied to the target threshold brightness value of the entrance section to determine the threshold brightness of the entrance section corresponding to extreme conditions. During the control process, the appropriate threshold brightness of the entrance section can be determined based on the current conditions at the tunnel entrance. When encountering extremely low visibility conditions, the peak brightness of the entrance section can be actively suppressed to a safe capping level, thereby ensuring the driver's visual safety in the tunnel entrance area throughout the entire process, while avoiding a light curtain effect caused by strong light under extreme conditions.

[0026] Then, based on the threshold brightness of the entrance section adapted to the current working conditions at the tunnel entrance, combined with the pre-set spatial lengths of the entrance section and the transition section, as well as the brightness of the middle section of the transition section, the equivalent gradient of the transition section can be calculated. The specific calculation formula is as follows: ; The equivalent gradient for the transition section, The threshold brightness of the inlet segment. For mid-range brightness, The spatial length of the transition section. , The minimum guaranteed brightness value specified for the lighting system.

[0027] Then, the equivalent gradient of the transition section can be used as a constraint. Based on the pre-set target brightness of each lighting zone boundary point at the tunnel entrance, the existing interpolation method can be used to determine the target brightness at different positions between each boundary point, thereby constructing the brightness curve of the tunnel entrance.

[0028] The equivalent gradient of the transition section characterizes the overall brightness decay rate of the tunnel entrance transition section. Using the equivalent gradient of the transition section as the slope constraint or rate of change constraint in interpolation modeling can ensure that the constructed brightness curve can smoothly transition the brightness of the entrance section to the target brightness of the subsequent partitions in space, without the occurrence of sudden drops, rises or changes in local brightness. This ensures that the overall decrease in brightness curve matches the segment length, the local changes are coordinated with the visual adaptation law, and the brightness distribution at boundary points and intermediate positions is continuous and controllable. This makes the target brightness command sequence obtained by discrete sampling according to the installation position of the lamps executable and visually safe.

[0029] Finally, the brightness curve can be discretized and sampled according to the installation position of each lighting fixture in the tunnel entrance to obtain the target brightness command sequence corresponding to the tunnel entrance. Based on the target brightness corresponding to each installation position in the target brightness command sequence, the corresponding lighting fixtures can be controlled.

[0030] In this embodiment, optionally, in step 1, obtaining the atmospheric transmittance at the tunnel entrance includes: Atmospheric visibility at the tunnel entrance is collected, and the atmospheric extinction coefficient is calculated by combining it with the set minimum brightness contrast threshold. The atmospheric transmittance is determined based on the atmospheric extinction coefficient and a set reference distance.

[0031] Specifically, when obtaining the atmospheric transmittance at the tunnel entrance, it can be directly measured using a transmissometer. In this embodiment, atmospheric visibility can also be collected in real time using a scattering visibility meter deployed outside the tunnel entrance, and the atmospheric extinction coefficient at the tunnel entrance can be calculated according to Koschmieder's visibility theorem. The specific calculation formula is as follows: ; in, Atmospheric extinction coefficient, The minimum brightness contrast threshold required for the human eye to identify a target object against a uniform background. For atmospheric visibility. The minimum brightness contrast threshold can be preset based on existing visual experiments, standard literature or empirical values. In the application of Koschmieder's theorem, the empirical value of the contrast threshold for human eye recognition of daytime targets is usually adopted, such as the commonly used 0.05.

[0032] By combining the atmospheric extinction coefficient and the established reference distance, the atmospheric transmittance can be calculated according to the Beer-Lambert law. The specific calculation formula is as follows: ; in, This serves as a reference benchmark distance. Because atmospheric transmittance exhibits path dependence, different propagation distances correspond to different transmittance levels for the same atmospheric extinction coefficient. Therefore, this invention introduces a reference benchmark distance to convert the extinction coefficient into a comparable and uniformly applicable standardized transmittance index. In this embodiment, the typical line-of-sight path length when a driver identifies a target at the tunnel entrance can be selected as the reference benchmark distance. Alternatively, the safe stopping sight distance, typical sight distance during approach, or warning decision distance can be selected as the reference benchmark distance.

[0033] Scattering visibility meters are mature technologies used in highway traffic environments, and their equipment cost, installation complexity, and maintenance difficulty are all lower than those of long-baseline transmission meters, lidar, and multispectral systems. Moreover, this invention is a lighting control method that requires continuous, real-time, and stable parameter updates. The high output frequency of the visibility meter makes it suitable for direct integration into the control system.

[0034] Furthermore, by first calculating the atmospheric extinction coefficient using Koschmieder's visibility theorem and then using Beer-Lambert's law to calculate the transmittance, the physical meaning is clear, making it easy to explain the relationship between atmospheric transmittance and driver visual perception. It also avoids the long optical path issues associated with directly measuring transmittance, making it suitable for complex site conditions at tunnel entrances.

[0035] In this embodiment, optionally, obtaining the atmospheric light curtain brightness at the tunnel entrance includes: Atmospheric visibility and sky background brightness at the tunnel entrance are collected, and the atmospheric extinction coefficient is calculated based on the atmospheric visibility and the set minimum brightness contrast threshold. The brightness of the atmospheric curtain is determined based on the atmospheric extinction coefficient, the sky background brightness, and the actual observation path length.

[0036] Specifically, when acquiring the brightness of the atmospheric light curtain at the tunnel entrance, a luminance meter or imaging luminance meter can be used to directly collect the field-of-view brightness along the driver's line of sight, and then combined with a reference target or existing background subtraction algorithm to separate the atmospheric light curtain brightness. Alternatively, based on camera images and atmospheric scattering models, the scene brightness can be decomposed into direct light attenuation components and air light components to estimate the atmospheric light curtain brightness.

[0037] In this embodiment, the atmospheric extinction coefficient at the tunnel entrance can be determined first using the same method described above. The background brightness of the sky at the tunnel entrance is then collected in real time using a luminance meter deployed outside the tunnel entrance. Finally, combining the atmospheric extinction coefficient, the background brightness of the sky, and the set actual observation path length, the atmospheric light curtain brightness at the tunnel entrance is calculated. The specific calculation formula is as follows: ; in, Brightness of the sky background The actual observation path length can be selected as the safe stopping sight distance in this embodiment. This is because the brightness of the atmospheric light curtain has a path-dependent cumulative scattering effect on the driver's line of sight, and the most critical visual task for the driver at the tunnel entrance is to identify, react to, and brake within a safe range after detecting an obstacle ahead.

[0038] The safe stopping sight distance comprehensively reflects vehicle speed, driver reaction time, and road surface adhesion conditions, corresponding to the observation distance range most sensitive to driving safety and of greatest engineering practical significance. Therefore, using the safe stopping sight distance as the actual observation path length allows the calculated atmospheric light curtain brightness to directly correspond to the actual visual interference faced by the driver when completing a safe stop, thus ensuring consistency between the light curtain brightness assessment results and the tunnel entrance lighting control targets. Furthermore, the safe stopping sight distance is a mature parameter in traffic engineering, easily set based on real-time vehicle speed and road conditions, possessing clear physical meaning, good feasibility, and safety conservatism.

[0039] In this embodiment, the safe stopping sight distance can be set by comprehensively considering the driver's reaction time and braking distance. The specific calculation formula is as follows: ; in, For safe parking visibility, The average driving speed at the tunnel entrance. The average perception reaction time of the driver. The road surface adhesion coefficient, This is the acceleration due to gravity.

[0040] The brightness of the atmospheric light curtain essentially originates from the accumulation of air light introduced by atmospheric scattering along the line of sight, and its magnitude is directly related to the atmospheric scattering intensity, the incident background brightness, and the length of the line of sight path. Therefore, the physical interpretation of the atmospheric light curtain brightness algorithm of this invention is the most direct. Moreover, this invention has already obtained the atmospheric extinction coefficient through atmospheric visibility, and by collecting the sky background brightness, the atmospheric light curtain brightness can be further calculated, resulting in a continuous parameter chain and avoiding the repeated deployment of complex sensors. Luminometers and visibility meters are both relatively mature road field equipment, which are easier to implement in engineering than directly separating the light curtain components, using lidar modeling, and image depth inversion.

[0041] In this embodiment, optionally, determining the threshold brightness of the inlet section under different operating conditions based on the target value of the threshold brightness of the inlet section includes: Obtain the visual risk index corresponding to the tunnel entrance, and calculate the peak brightness cutoff value corresponding to the extremely low visibility condition by combining the peak brightness of the entrance section lighting under standard clear weather conditions. By combining the peak brightness cutoff value and the target value of the inlet segment threshold brightness, the inlet segment threshold brightness corresponding to different operating conditions is determined, specifically as follows: ; in, The threshold brightness of the inlet segment. The threshold brightness target value for the entrance segment. As a visual risk index, This serves as the normalized upper limit for the visual risk index. This is the critical threshold for the visual risk index, used to determine whether the current working condition has entered a high visual risk state. Atmospheric visibility, This is the critical threshold for atmospheric visibility, used to determine whether the current operating conditions are extremely low visibility. This represents the peak brightness of the entrance section lighting under standard clear weather conditions. This represents the peak compression ratio.

[0042] Specifically, to prevent a light curtain effect caused by strong light illumination in extremely low visibility conditions, this invention introduces a peak brightness cap truncation mechanism for extreme conditions such as extremely low visibility, based on the calculated target value of the threshold brightness at the entrance section. When extreme conditions occur, the calculated target value of the threshold brightness at the entrance section is suppressed to the upper limit of the peak brightness, thereby avoiding a light curtain effect caused by excessive threshold brightness at the entrance section under extreme conditions.

[0043] Specifically, the existing visual risk index assessment method is first used to evaluate the visual risk index of the current tunnel entrance. Then, based on the visual risk index or the atmospheric visibility at the tunnel entrance, it is determined whether the tunnel entrance is currently under extreme conditions. If not, the calculated threshold brightness target value of the entrance section is used as the threshold brightness of the entrance section for subsequent brightness curve construction. Conversely, the peak brightness cutoff value can be calculated based on the visual risk index and the peak brightness of the entrance section lighting under standard clear weather conditions, as shown in the following formula: ; This is the peak brightness cutoff value.

[0044] When the peak brightness upper limit truncation mechanism is triggered, the peak brightness truncation value is compared with the target value of the entry segment threshold brightness, and the minimum value between the two is selected as the entry segment threshold brightness for subsequent brightness curve construction.

[0045] In this embodiment, optionally, obtaining the visual risk index corresponding to the tunnel entrance includes: The visual contrast is calculated based on the atmospheric light curtain brightness, atmospheric extinction coefficient, and target background brightness, combined with the set inherent contrast and target background brightness. Based on visual contrast and minimum contrast threshold, safe parking sight distance and atmospheric visibility, atmospheric light curtain brightness and external background brightness, the degree of visual contrast attenuation, sight distance adequacy and relative intensity of the light curtain are calculated respectively. The visual risk index of the tunnel entrance is assessed by evaluating the degree of visual contrast attenuation, the adequacy of the viewing distance, and the relative intensity of the light curtain.

[0046] Specifically, most existing visual risk assessment methods do not consider the potential risks of the light curtain effect. They follow the monotonous logic of "the darker it is, the more light you need" when visibility is reduced, continuously increasing the lighting power, and lack identification and response mechanisms for the light curtain shading effect caused by fog scattering.

[0047] Therefore, based on the atmospheric light curtain brightness, atmospheric extinction coefficient, and target background brightness, combined with the set inherent contrast and target background brightness, the driver's actual perceived visual contrast of the target object (such as an obstacle or vehicle ahead) after atmospheric scattering and attenuation can be calculated. This fully incorporates the physical process of light transmission in the real atmospheric medium into the visual risk index assessment. The specific calculation formula is as follows: ; in, For visual contrast, The inherent contrast of the target object under clear, non-scattering conditions. The target object's background brightness is defined as the brightness contrast of the target object relative to its background under clear, fog-free conditions with no significant scattering interference. The target object's background brightness is the brightness of the background area where the target object is located in the driver's line of sight.

[0048] Inherent contrast can be obtained through a clear-sky calibration measurement method. This involves selecting typical targets such as obstacles, vehicles, and their corresponding background areas under reference conditions with no or weak scattering. Using a luminance meter or imaging luminance meter, the brightness of the target object and the background are measured respectively. The inherent contrast is then calculated based on the contrast relationship between the target object and the background brightness. The specific calculation formula is as follows: ; in, For reference, the brightness of the target object under the operating conditions, The brightness of the background area where the target object is located is used as a reference under certain working conditions.

[0049] The background brightness of the target object can be obtained by direct measurement, that is, by using a luminance meter or imaging luminance meter to collect the brightness of the background area adjacent to the target object along the driver's line of sight, and taking the average brightness of the area as the background brightness of the target object.

[0050] Then, the degree of visual contrast attenuation can be assessed based on visual contrast ratio and minimum contrast threshold; the visibility adequacy can be assessed based on the actual observation path length and atmospheric visibility. The relative intensity of the light curtain can be calculated based on the brightness of the atmospheric light curtain and the brightness of the external background. Finally, taking into account the degree of visual contrast attenuation, visibility adequacy, and relative intensity of the light curtain, the current visual risk index at the tunnel entrance can be assessed, as calculated using the following formula: ; in, The lowest contrast threshold that the human eye can recognize. It is a positive part function. To prevent the denominator from being a strange, tiny positive number. , , These are the weighting coefficients corresponding to the degree of visual contrast attenuation, viewing distance adequacy, and relative intensity of the light curtain, respectively.

[0051] The degree of visual contrast attenuation characterizes the extent to which fog reduces target recognition capability; when visual contrast is less than or equal to 0, target recognition capability reaches a dangerous state. Visibility margin characterizes the degree of match between braking requirements and visibility assurance; when the safe stopping visibility exceeds atmospheric visibility, it indicates that visibility is insufficient to support safe stopping. The relative intensity of the light curtain characterizes the degree of pollution the light curtain causes to the visual background, directly reflecting the potential risks of the light curtain effect.

[0052] In this embodiment, optionally, the spatial length of each lighting zone is set, including: The fixed space length corresponding to each lighting zone is determined based on the tunnel's design speed, and the visual risk index corresponding to the tunnel entrance is obtained. Based on the fixed space length corresponding to each lighting zone, and combined with the set risk elasticity coefficient and visual risk index of each lighting zone, the space length corresponding to each lighting zone is calculated.

[0053] Specifically, current design specifications determine the spatial length of each lighting zone (approach section, entrance section, transition section) based on the design speed. These spatial lengths are written into the control program as fixed parameters after project completion and remain unchanged throughout the entire operating cycle. However, traffic practice shows that drivers will significantly reduce their speed in low-visibility weather conditions such as fog, haze, and heavy rain due to safety instincts, with actual operating speeds potentially only 40%-60% of the design speed. At low speeds, the time required for drivers to traverse fixed-length, highly illuminated zones is significantly increased, resulting in a large amount of ineffective lighting energy consumption that exceeds the actual needs of visual adaptation.

[0054] Furthermore, if the design length of the transition section is based on high-speed driving calibration, the driver will spend too much time in the transition section at low speeds. The rate of brightness drop at the end of the transition section will be too gradual relative to the travel speed, which may lead to abnormal monotonicity in brightness perception at certain critical speeds, failing to guarantee the smooth and continuous visual adaptation process. Therefore, fixing the spatial length of the lighting zone will cause the lighting control system to be severely mismatched in scenarios where traffic flow characteristics dynamically change with weather conditions.

[0055] To address this, the spatial length of each lighting zone can be modeled as an elastic variable that dynamically changes with real-time driving speed and the overall level of visual risk, ensuring that the spatial coverage of lighting resources always precisely matches the driver's current visual adaptation process. This eliminates the ineffective energy consumption caused by excessive extension of high-brightness areas in low-speed congestion conditions, while also ensuring that drivers have sufficient visual transition time under high-risk weather conditions.

[0056] Specifically, firstly, the fixed spatial length of each lighting zone can be calculated based on the tunnel's design speed. The specific calculation formula is as follows: ; ; in, The fixed spatial length of the entrance section. The fixed spatial length of the transition section To design vehicle speed, , These are the times required for a vehicle to pass through the entrance section and the transition section at its designed speed, respectively.

[0057] Then, based on the fixed spatial lengths of the entrance and transition sections, the risk elasticity coefficients corresponding to the transition and entrance sections and the visual risk index of the tunnel entrance are introduced to dynamically adjust the spatial lengths of the entrance and transition sections. The specific calculation formula is as follows: ; ; in, , These are the spatial lengths of the entrance section and the transition section, respectively. For real-time vehicle speed, , These are the risk elasticity coefficients for the entry section and the transition section, respectively. For the amplitude limiting function, , These are the minimum and maximum engineering constraint boundaries for the entrance section. , These are the minimum and maximum engineering constraint boundaries for the transition section.

[0058] The risk elasticity coefficient can be used to characterize the sensitivity of the spatial length of each lighting zone to changes in the visual risk index, and can be obtained through pre-calibration. Specifically, based on typical operating conditions such as different visibility, vehicle speed, background brightness, and light curtain intensity, combined with the driver's visual adaptation needs, methods such as simulation analysis, real vehicle testing, driving simulation experiments, or regression analysis of historical operating data can be used to establish the correspondence between the visual risk index and the required length adjustment of each lighting zone, thereby determining the risk elasticity coefficients corresponding to the entrance section and transition section. When the visual risk index increases, the risk elasticity coefficient can be used to determine the extent to which the length of each lighting zone should be adjusted.

[0059] Using real-time vehicle speed instead of design speed as the length calculation benchmark allows the spatial length of the lighting zones to shrink synchronously with vehicle speed. At low speeds, this automatically compresses the coverage of high-brightness areas, eliminating ineffective lighting energy consumption in low-speed congestion. Simultaneously, by introducing a visual risk index gain term, the transition section length is appropriately extended when visual risk increases. This provides drivers with a more ample visual adaptation process under adverse weather conditions, ensuring that the spatial coverage of lighting resources always precisely matches the driver's current visual adaptation process. This eliminates the ineffective energy consumption caused by excessive extension of high-brightness areas in low-speed congestion while ensuring sufficient visual transition time for drivers in high-risk weather conditions.

[0060] In this embodiment, optionally, an interpolation method is used to construct the brightness curve of the tunnel entrance, including: When the equivalent gradient of the transition segment is lower than the minimum brightness gradient threshold, a brightness step with a certain spatial width is inserted at the brightness curve corresponding to the end of the transition segment.

[0061] Specifically, the equivalent gradient of the transition segment represents the rate of brightness decrease along the spatial length of the transition segment, from the threshold brightness of the entrance segment to the brightness of the middle segment. The equivalent gradient of the transition segment can be used to constrain and implement the gradual change of light intensity in the interpolation algorithm, thereby ensuring a smooth visual transition that conforms to the physiological accommodation rate of the human eye and avoiding dizziness or insufficient adaptation caused by excessive brightness jumps.

[0062] Furthermore, the equivalent gradient of the transition segment also reflects the impact of the extended transition segment length after peak truncation on visual adaptation requirements. When the equivalent gradient of the transition segment is too gentle, it will be difficult to provide sufficient constriction driving force for the pupil. Therefore, the calculated equivalent gradient of the transition segment can be compared with a set minimum luminance gradient threshold. If the equivalent gradient of the transition segment is lower than the minimum luminance gradient threshold, a luminance step of a certain width can be inserted at the luminance curve corresponding to the end of the transition segment to provide sufficient constriction driving force for the pupil. The formula for calculating the amplitude of the luminance step is as follows: ; in, The amplitude of the brightness step. The minimum luminance gradient threshold required to maintain visual adaptation. The width of the brightness step is an integer multiple of the installation spacing of the lighting fixtures.

[0063] The minimum luminance gradient threshold is used to characterize the minimum intensity of luminance change required to maintain continuous visual adaptation of the driver within the transition range. Essentially, it is a lower limit parameter to ensure that the pupil can continuously produce an effective contraction response.

[0064] Different brightness gradient transition lighting scenarios can be set up in driving simulators, closed test tracks, or actual tunnel test sections. Indicators such as changes in pupil diameter, target recognition accuracy, reaction time, and subjective comfort of the driver when passing through the transition section can be collected. Then, based on the collected indicators, the minimum brightness gradient that allows the driver to maintain continuous visual adaptation without adaptation lag or significant decline in recognition ability can be selected as the minimum brightness gradient threshold.

[0065] Alternatively, a small brightness gradient may result in insufficient brightness change per unit time, making it difficult to provide enough constriction driving force for the pupil. Therefore, the minimum brightness gradient threshold can be derived by inversely calculating the static sensitivity of the human pupil to brightness changes and the minimum effective rate of change required for the pupil to maintain effective accommodation. In other words, the minimum allowable brightness gradient can be derived as the minimum brightness gradient threshold by using the pupil's ability to continuously generate an effective accommodation response as a constraint and combining the relationship between vehicle speed and the rate of change of brightness.

[0066] Because a small brightness step is added only at the end of the transition segment, the overall brightness curve remains within a controlled and gradual transition. This compensation is localized and limited, designed to maintain the natural response of the visual system without introducing large, transient jumps. This brightness step compensation step works in conjunction with the aforementioned peak brightness truncation and brightness curve construction methods, compensating for the shortened visual adaptation drive caused by the peak value reduction by flexibly extending the transition segment coverage length. This achieves a synergistic optimization of suppressing the scattered light curtain and ensuring sufficient adequacy in the adaptation process.

[0067] In this embodiment, optionally, an interpolation method is used to construct the brightness curve of the tunnel entrance, including: Based on the driver's physiological accommodation limit, static sensitivity, and real-time speed, the maximum allowable value of the brightness gradient at different locations at the tunnel entrance is calculated. Using the maximum allowable value of the brightness gradient and the equivalent gradient of the transition section as constraints, the brightness curve of the tunnel entrance is constructed by interpolation based on the target brightness corresponding to the boundary points of each lighting zone at the tunnel entrance.

[0068] Specifically, when a driver passes through the transition zone at the tunnel entrance, their visual system undergoes a continuous dynamic process of light and dark adaptation. The diameter of the human eye pupil changes with the ambient brightness according to specific physiological response laws, and its adjustment rate has a clear physiological upper limit.

[0069] Current dimming strategies use the lamp's permissible dimming range as the sole constraint boundary. When setting target brightness values ​​for each segment, they do not consider whether the rate of brightness change experienced by the driver per unit time along the direction of travel at a given actual vehicle speed exceeds the instantaneous accommodation limit of the pupil. When sudden changes in weather conditions trigger a rapid switching of lighting modes, or when the driver passes through the boundary of multiple lighting zones with significant brightness differences at high speeds, the drastic brightness jump is highly likely to exceed the upper limit of the pupil's accommodation rate, leading to temporary blind spots and dizziness, posing a significant safety risk in high-speed traffic scenarios. Therefore, when constructing the brightness curve, constraints based on human visual physiology can be introduced to ensure that the rate of brightness change along the direction of travel does not exceed the upper limit of the driver's instantaneous pupil's accommodation capacity at any point.

[0070] Specifically, the steady-state relationship between the diameter of the human eye pupil and the ambient brightness can be described first using the classic Moon-Spencer model. The specific expression of the model is as follows: ; in, The diameter of the human eye pupil, This refers to ambient light.

[0071] By differentiating the pupil diameter with respect to ambient brightness, we can obtain the static sensitivity of the pupil diameter to brightness. Based on the driver's real-time speed, the rate of change of ambient brightness over time can be calculated using the following formula: ; Correspondingly, the rate of change of pupil diameter over time is: ; To ensure that drivers do not experience visual dizziness or temporary blind spots, the absolute value of the rate of change of pupil diameter is specified to not exceed the physiological accommodation limit of the human eye. ,Right now: ; The illumination luminance gradient at position can be derived. The maximum allowable value of the brightness gradient at a given location is calculated using the following formula: ; The maximum permissible value of the brightness gradient is larger in higher brightness regions, such as the entrance segment, and relatively smaller in lower brightness regions, such as the end of the transition segment. This closely matches the physiological characteristics of the human eye, where the pupil is less sensitive to brightness changes in high-brightness environments and more sensitive in low-brightness environments, demonstrating the adaptive rationality of this constraint. Therefore, the following constraints can also be introduced when constructing the brightness curve: .

[0072] in, For position The target brightness at that location.

[0073] In this way, this physiological constraint can be embedded as an insurmountable hard boundary into the construction process of the lighting transition curve, ensuring that the driver will not experience a brightness jump that exceeds the visual neural adjustment limit under any combination of driving speed and weather conditions, thus achieving inherent safety in lighting control from a visual physiological perspective.

[0074] In this embodiment, optionally, an interpolation method is used to construct the brightness curve of the tunnel entrance, including: The brightness curve corresponding to the tunnel entrance is constructed using a piecewise cubic Hermite interpolation polynomial method.

[0075] Specifically, after determining the maximum allowable value of the brightness gradient and the equivalent gradient of the transition segment, the maximum allowable value of the brightness gradient can be used as a local slope constraint, and the equivalent gradient of the transition segment can be used as an overall trend constraint of the transition segment. Both are used together to generate the brightness curve to obtain a continuous, smooth brightness distribution that satisfies visual physiological constraints. In this embodiment, a smooth brightness curve can be generated using a piecewise cubic Hermite interpolation polynomial method under the constraints of the maximum allowable value of the brightness gradient and the equivalent gradient of the transition segment.

[0076] The equivalent gradient of the transition segment is used to constrain the overall descent rate of the brightness curve of the transition segment. When determining the target brightness of each boundary point in the transition segment, setting the intermediate control points of the transition segment, and constructing the interpolation curve between adjacent nodes, it is necessary to ensure that the secant slope of adjacent boundary points in the transition segment or the weighted average of the secant slopes of each interval in the transition segment is consistent with the equivalent gradient of the transition segment, or that the deviation between the two does not exceed a preset threshold, so as to ensure that the generated brightness curve meets the expected overall decay trend in the transition segment.

[0077] Based on this, a maximum allowable value constraint on the brightness gradient is further applied to the slope of each interpolation node. Specifically, the coordinates and target brightness of the boundary points of lighting zones such as the entrance section and transition section are set, and a sequence of boundary coordinate points is generated. and target brightness sequence Between two adjacent boundary points The brightness curve can be represented as: ; in, For normalization parameters, ; ; ; ; .

[0078] The node slope, determined using the PCHIP harmonic mean method, ensures that the constructed brightness curve remains monotonic and shape-preserving overall, avoiding local overshoot or oscillations. The specific calculation formula is as follows: ; .

[0079] The brightness curve can be constructed based on the node slope constraint. Specifically, if the absolute value of the calculated node slope is greater than the maximum allowable value of the brightness gradient, the node slope is truncated to the maximum allowable value of the brightness gradient, and the piecewise cubic Hermite interpolation polynomial method is used again for interpolation to ensure that the rate of change of brightness within any local interval of the brightness curve does not exceed the upper limit allowed by the driver's visual adaptation process. Finally, a tunnel entrance brightness curve that satisfies the equivalent gradient constraint of the transition section and the maximum allowable value constraint of the brightness gradient is obtained.

[0080] The final generated tunnel entrance brightness curve can simultaneously satisfy the overall attenuation trend defined by the equivalent gradient of the transition section, and the local rate of change constraint defined by the maximum allowable value of the brightness gradient, while maintaining monotonicity and C throughout the entire process. 1 The continuity ensures that the generated brightness curve balances visual comfort, controllability, and driving safety.

[0081] If the equivalent gradient of the transition segment is lower than the minimum brightness gradient threshold, a brightness step with a preset spatial width can be inserted at the end of the transition segment. In this way, the final generated brightness curve can possess both full monotonicity and C-value. 1 Compliance with continuity and pupil change rate constraints.

[0082] In this embodiment, optionally, lighting control based on a target brightness command sequence includes: Based on the target brightness of the lighting fixtures in the target brightness command sequence and the road surface brightness of the lighting fixtures at rated power, the dimming ratio of the lighting fixtures is calculated. Based on the dimming ratio and target brightness, the lighting fixtures are controlled using a discrete PI control method according to the set closed-loop sampling period.

[0083] Specifically, after constructing the brightness curve at the tunnel entrance, the brightness curve can be sampled and discretized according to the installation position of each lighting fixture in the tunnel entrance, thereby obtaining the target brightness corresponding to each lighting fixture and generating the corresponding target brightness instruction sequence.

[0084] The target brightness in the target brightness command sequence can be converted into a stepless dimming ratio signal for each lighting fixture driver. The lighting fixtures can be driven through a digital addressable lighting interface protocol to achieve continuous and smooth dimming. The dimming ratio constraint prevents flicker and premature loss.

[0085] Specifically, the target brightness is first converted into the dimming ratio of the lighting fixtures, as shown in the following formula: ; in, The target brightness corresponding to the lighting fixtures. The road surface brightness produced by lighting fixtures at their rated power can be calculated based on the optical parameters of the lighting fixtures, their installation height, and elevation angle. The specific calculation formula is as follows: ; in, The luminance coefficient of the road surface is used to characterize the reflective properties of the road surface in converting illuminance into luminance. The illuminance produced by a lighting fixture at its rated power at a target road surface point. The elevation angle of the target road surface point relative to the lighting fixture. This refers to the installation height of the lighting fixtures.

[0086] Then, with As a closed-loop sampling period, a discrete PI control method is used to control the lighting fixtures. The correction for the brightness feedback inside the cave is as follows: ; ; in, This represents the real-time measured average brightness of the area illuminated by the lighting fixture. For lighting fixtures Real-time brightness tracking error, , These are the proportional coefficient and the integral coefficient, respectively, which can be tuned using the Ziegler-Nichols method based on the luminaire's response characteristics.

[0087] Specifically, the luminaire can first be operated at a stable operating point, and a step disturbance can be applied to the control input to collect the brightness response curve of the corresponding illuminated area. Then, a first-order inertial pure time-delay model of the luminaire can be obtained by fitting the brightness response curve to determine the process gain. Pure delay time and time constant ; The proportional gain and integral time constant were then determined according to the Ziegler-Nichols open-loop tuning rule. Furthermore, according to Determine the integral coefficients , .

[0088] To verify the technical effectiveness of the adaptive control method for tunnel entrance lighting proposed in this invention, an experimental platform was built in a six-lane, two-way highway tunnel (design speed 100 km / h, tunnel entrance facing due east) for a 12-month all-weather comparative test. The experiment employed the controlled variable method, conducting a comprehensive comparative evaluation of the method of this invention (hereinafter referred to as the "adaptive method") and the traditional open-loop lookup table control method (hereinafter referred to as the "traditional method") specified in the current "Highway Tunnel Lighting Design Specifications" (JTG / TD70 / 2-01) under four typical meteorological conditions: clear day standard condition, light fog condition (visibility 200-500 m), moderate fog / haze condition (visibility 50-200 m), and extremely low visibility condition (visibility < 50 m).

[0089] (1) Comparison of threshold brightness setting accuracy in the entrance section This experiment uses the driver's actual visual perception of equivalent brightness as a benchmark to evaluate the brightness setting errors of the two methods under different operating conditions. The specific comparison results are shown in Table 1 below: Table 1 Comparison of Threshold Brightness Setting Values ​​and Ideal Reference Brightness for Different Meteorological Inlet Sections (Unit: cd / m²) 2 ) As shown in Table 1 above, the traditional method, when visibility decreases, systematically overestimates its setpoints due to the lack of scattering efficiency compensation and light curtain reduction factors. In extremely low visibility conditions, the deviation reaches as high as 410%, far exceeding the actual needs of drivers and significantly exacerbating the light curtain effect. The adaptive method of this invention controls the error to within 5% under all operating conditions, demonstrating a significant advantage in accuracy.

[0090] (2) Comparison of light curtain effect suppression capabilities The light curtain brightness gain ratio is defined as the ratio of the increase in the measured light curtain brightness in the driver's direction after the lighting is turned on to the baseline value when the lights are off. The lower this value, the better the suppression of the light curtain effect. The comparison results of the light curtain effect suppression capabilities of the traditional method and the present invention are shown in Table 2 below: Table 2 Comparison of light curtain brightness gain ratio under different operating conditions (%) As shown in Table 2, under extremely low visibility conditions, traditional methods, by continuously increasing the power output of the luminaires, result in a light curtain luminance gain ratio as high as 142.6%, leading to a severe light curtain obstruction effect. This invention, through a peak luminance cutoff mechanism and a light curtain reduction factor, suppresses the light curtain luminance gain ratio to 23.7%, achieving an improvement of 83.4%, significantly avoiding the light curtain effect under extreme conditions.

[0091] (3) Comparison of the continuity and smoothness of the brightness curve The quality of the target brightness command sequences generated by the two methods was compared using the number of maximum local gradient exceedances and the C1 continuity compliance rate as indicators. Table 3 below shows the comparison results of the continuity and smoothness of the brightness curves between the traditional method and the present invention: Table 3 Comparison of Continuity and Smoothness Indicators of Brightness Curve As shown in Table 3, under smoggy conditions, the traditional method resulted in 24.7% of the lamp control points exceeding the driver's visual physiological adjustment limit due to excessively large jumps in the target brightness values ​​at the zone boundaries. The C1 continuity compliance rate was only 48.2%, easily causing temporary visual discomfort for the driver. This invention employs piecewise cubic Hermite interpolation and a brightness step compensation mechanism, eliminating all gradient exceedance events. The C1 continuity compliance rate reached 100%, and the driver's subjective comfort score improved by 40.3%.

[0092] (4) Comparison of system lighting energy consumption The annual average lighting energy consumption under different operating conditions (normalized based on the annual operating electricity cost of the standard tunnel entrance section) is compared with the lighting energy consumption of the system of the present invention using the traditional method. The results are shown in Table 4 below. Table 4 Comparison of Annual Average Lighting Energy Consumption As shown in Table 4 above, this invention achieves energy savings of 11.0% under comprehensive annual operating conditions through precise threshold brightness calculation and dynamic lighting zone length adjustment. The energy-saving effect is even more significant under smog and extremely low visibility conditions, reaching up to 66.5%. This is because traditional methods tend to over-supplement the light under low visibility conditions, while this invention effectively controls ineffective high-power output through peak cutoff and scattering suppression mechanisms.

[0093] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. An adaptive control method for tunnel entrance lighting, characterized in that, include: The atmospheric transmittance and atmospheric light curtain brightness at the tunnel entrance are obtained. The scattering efficiency compensation factor is calculated based on the atmospheric transmittance and scattering correction coefficient. The specific calculation formula is as follows: ； in, This is the scattering efficiency compensation factor. Atmospheric transmittance. This is the scattering correction factor; Combining the scattering efficiency compensation factor, threshold brightness coefficient, atmospheric transmittance, light curtain reduction factor, external background brightness, and atmospheric light curtain brightness, the target value of the threshold brightness at the tunnel entrance is calculated. The specific calculation formula is as follows: ； in, The threshold brightness target value for the entrance segment. The threshold brightness coefficient, For external background brightness without atmospheric attenuation, The light curtain reduction factor. The brightness of the atmospheric light curtain superimposed along the line of sight when the driver observes from a certain distance from the tunnel entrance; Based on the target value of the threshold brightness of the entrance section, determine the threshold brightness of the entrance section corresponding to different working conditions, and determine the threshold brightness of the entrance section under the current working condition of the tunnel entrance; The spatial length of each lighting zone at the tunnel entrance is set, and the equivalent gradient of the transition section is calculated by combining the threshold brightness of the entrance section and the brightness of the middle section of the transition section. Using the equivalent gradient of the transition section as a constraint, and based on the target brightness corresponding to the boundary points of each lighting zone at the tunnel entrance, an interpolation method is used to construct the brightness curve of the tunnel entrance. The brightness curve is sampled and discretized based on the installation location of the lighting fixtures inside the tunnel entrance to obtain the corresponding target brightness command sequence for lighting control.

2. The adaptive control method for tunnel entrance lighting according to claim 1, characterized in that, Obtain the atmospheric transmittance at the tunnel entrance, including: Atmospheric visibility at the tunnel entrance is collected, and the atmospheric extinction coefficient is calculated by combining it with the set minimum brightness contrast threshold. The atmospheric transmittance is determined based on the atmospheric extinction coefficient and a set reference distance.

3. The adaptive control method for tunnel entrance lighting according to claim 1, characterized in that, Obtain the brightness of the atmospheric light curtain at the tunnel entrance, including: Atmospheric visibility and sky background brightness at the tunnel entrance are collected, and the atmospheric extinction coefficient is calculated based on the atmospheric visibility and the set minimum brightness contrast threshold. The brightness of the atmospheric curtain is determined based on the atmospheric extinction coefficient, the brightness of the sky background, and the actual observation path length.

4. The adaptive control method for tunnel entrance lighting according to claim 1, characterized in that, The threshold brightness of the inlet section is determined based on the target value of the threshold brightness of the inlet section for different operating conditions, including: Obtain the visual risk index at the tunnel entrance, and combine it with the peak brightness of the entrance section lighting under standard clear weather conditions to calculate the peak brightness cutoff value corresponding to the extremely low visibility condition. By combining the peak brightness cutoff value and the target value of the inlet segment threshold brightness, the inlet segment threshold brightness corresponding to different operating conditions is determined, specifically as follows: ； in, The threshold brightness of the inlet segment. The threshold brightness target value for the entrance segment. As a visual risk index, This serves as the normalized upper limit for the visual risk index. This is the critical threshold for the visual risk index. Atmospheric visibility, This is the critical threshold for atmospheric visibility. This represents the peak brightness of the entrance section lighting under standard clear weather conditions. This represents the peak compression ratio.

5. The adaptive control method for tunnel entrance lighting according to claim 4, characterized in that, Obtain the visual risk index corresponding to the tunnel entrance, including: The visual contrast is calculated based on the atmospheric light curtain brightness, atmospheric extinction coefficient, and target background brightness, combined with the set inherent contrast and target background brightness. Based on visual contrast and minimum contrast threshold, safe parking sight distance and atmospheric visibility, atmospheric light curtain brightness and external background brightness, the degree of visual contrast attenuation, sight distance adequacy and relative intensity of the light curtain are calculated respectively. The visual risk index of the tunnel entrance is assessed by evaluating the degree of visual contrast attenuation, the adequacy of the viewing distance, and the relative intensity of the light curtain.

6. The adaptive control method for tunnel entrance lighting according to claim 1, characterized in that, Define the spatial length of each lighting zone, including: The fixed space length corresponding to each lighting zone is determined based on the tunnel's design speed, and the visual risk index corresponding to the tunnel entrance is obtained. Based on the fixed space length corresponding to each lighting zone, and combined with the set risk elasticity coefficient and visual risk index of each lighting zone, the space length corresponding to each lighting zone is calculated.

7. The adaptive control method for tunnel entrance lighting according to claim 1, characterized in that, The brightness curve corresponding to the tunnel entrance is constructed using interpolation methods, including: When the equivalent gradient of the transition segment is lower than the minimum brightness gradient threshold, a brightness step with a certain spatial width is inserted at the brightness curve corresponding to the end of the transition segment.

8. The adaptive control method for tunnel entrance lighting according to claim 1, characterized in that, The brightness curve corresponding to the tunnel entrance is constructed using interpolation methods, including: Based on the driver's physiological accommodation limit, static sensitivity, and real-time speed, the maximum allowable value of the brightness gradient at different locations at the tunnel entrance is calculated. Using the maximum allowable value of the brightness gradient and the equivalent gradient of the transition section as constraints, the brightness curve of the tunnel entrance is constructed by interpolation based on the target brightness corresponding to the boundary points of each lighting zone at the tunnel entrance.

9. The adaptive control method for tunnel entrance lighting according to claim 1, characterized in that, The brightness curve corresponding to the tunnel entrance is constructed using interpolation methods, including: The brightness curve corresponding to the tunnel entrance is constructed using a piecewise cubic Hermite interpolation polynomial method.

10. The adaptive control method for tunnel entrance lighting according to claim 1, characterized in that, Lighting control is performed according to the target brightness command sequence, including: Based on the target brightness of the lighting fixtures in the target brightness command sequence and the road surface brightness of the lighting fixtures at rated power, the dimming ratio of the lighting fixtures is calculated. Based on the dimming ratio and target brightness, the lighting fixtures are controlled using a discrete PI control method according to the set closed-loop sampling period.

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