A platform door gap detection system and method based on acoustic collaboration

Abstract

The present application relates to the technical field of platform door gap detection, and particularly relates to a platform door gap detection system and method based on acoustic cooperation, which comprises: an ultrasonic wave transmitting unit arranged at one end of a platform door; a Helmholtz resonator array vertically installed on the inner side of the platform door, which is composed of a plurality of Helmholtz resonators arranged in a two-dimensional plane in parallel; a plurality of piezoelectric sensors corresponding to the plurality of Helmholtz resonators one by one, and all arranged in the closed cavities of the Helmholtz resonators; and a controller, with the electrical signal input end of the controller connected to the electrical signal output end of the plurality of piezoelectric sensors. The present application utilizes the active detection capability of ultrasonic waves and the resonance enhancement characteristics of Helmholtz resonators, can avoid environmental interference, screen and enhance the amplitude change of the sound signal caused by foreign matters, especially capture the subtle amplitude change of the sound signal, and cooperatively improve the detection sensitivity, so as to effectively detect the small foreign matters in the platform door gap of the subway.

Description

Technical Field

[0001] This invention relates to the field of platform screen door gap detection technology, and more specifically, to a platform screen door gap detection system and method based on acoustic coordination. Background Technology

[0002] In recent years, with rapid social development and accelerated urbanization, cities have continued to expand and populations have grown. Urban rail transit, with subways at its core, has become a key support for alleviating urban traffic pressure due to its advantages such as large capacity, high speed, safety, punctuality, energy conservation, and environmental protection. It has become the backbone of public transportation in modern large and medium-sized cities. As the network operation of rail transit deepens, operational safety has also become a core issue for the industry's development.

[0003] In the subway safety operation system, ensuring passenger safety while waiting for and riding the train is a key focus for managers and researchers. Platform screen doors, as crucial equipment for ensuring passenger safety, inevitably have a gap between themselves and the train body due to design and installation requirements that must meet clearance standards. This gap is not only a core area for passenger boarding and alighting but also a high-risk zone for accidents involving people or belongings getting caught, especially during peak travel periods. Incidents of passengers or their belongings getting stuck in the gap between the platform screen doors and train doors are frequent. Therefore, conducting foreign object detection in this gap before train departure is crucial for ensuring passenger safety and property security, and improving train operation efficiency.

[0004] Meanwhile, with the evolution of my country's rail transit technology, fully automated driverless operation has become an important direction for future development. The automatic foreign object detection technology between platform screen doors and train doors is a key link supporting this trend, and its research has important practical significance.

[0005] Currently, the protective measures of platform screen door control systems both domestically and internationally are mainly divided into two categories: physical protection technology and automatic detection technology. Physical protection technologies already in use include anti-pinch barriers, anti-climb barriers, and observation light strips. These measures generally have the advantages of low cost, simple structure, and ease of installation, effectively reducing the risk of passenger pinching and improving track intrusion prevention capabilities. However, physical protection technologies have significant limitations, such as a lack of proactive early warning capabilities, low detection efficiency, and difficulty in timely detection and handling of small objects in the gaps, leading to a higher risk of damage to passengers' belongings. Therefore, it is necessary to combine physical protection technology with intelligent monitoring technology to improve the subway safety protection system.

[0006] Automatic foreign object detection technologies for subway platform doors and train doors mainly include infrared light curtains, laser detection, laser scanning, and machine vision. Infrared light curtain detection uses a transmitter and receiver to form an infrared warning line, operating based on an obstruction alarm mechanism. However, its infrared light dispersion range is small, making it unsuitable for long-distance detection, and it is susceptible to environmental interference, leading to false alarms. Its ability to identify small objects in gaps is also limited. Laser detection works on a similar principle to infrared light curtains, but lasers have stronger focusing capabilities, enabling long-distance through-hole detection. In practical applications, laser transmitters and receivers are typically installed on the ground outside the doors at both ends of the platform. After the platform door closes, the presence of foreign objects in the gap is determined by detecting whether the laser beam is blocked. Laser scanning is based on the time-of-flight measurement principle and is often installed on the top of the platform door. The transmitter emits a single or multiple fan-shaped beam, which is reflected by the LED strip at the bottom of the platform door's anti-slip rubber strip to the receiver. Foreign objects are identified by calculating the emission time. Compared to infrared and laser beam-based technologies, it offers better stability and is suitable for curved platforms, but the measurement information is sparse and the cost is high, with a detection range typically limited to within 15 meters. Machine vision-based detection methods typically use vertical light strips on train end doors or anti-slip rubber strips at the bottom of platform doors as background references. Images containing complete light strips are captured by cameras, and image recognition algorithms are used to analyze the integrity of the light strips to identify foreign objects. However, these methods are easily affected by environmental factors such as lighting and weather.

[0007] In summary, foreign object detection between subway platform doors and trains is a technical challenge in the field of urban rail transit. Existing technologies such as infrared and laser generally suffer from problems such as large detection blind spots, weak resistance to environmental interference, and high costs.

[0008] Ultrasonic waves are high-frequency sound waves with frequencies above 20kHz. They are characterized by strong directionality and concentrated energy, and are widely used in distance detection and obstacle recognition. However, in a subway environment, noise from ventilation systems, train announcements, and passenger conversations is mainly distributed within the audible range of 20Hz to 20kHz, which is frequency-separated from ultrasonic waves. Therefore, ultrasonic waves are less directly affected by subway environmental noise. A Helmholtz resonant cavity is an acoustic structure based on the principle of acoustic resonance. When the frequency of a sound wave matches the natural frequency of the cavity, resonance occurs. This resonance characteristic can significantly amplify sound waves of a specific frequency while suppressing other frequency components, thus achieving narrowband filtering.

[0009] Based on this, the present invention proposes an acoustic detection method that combines ultrasound and Helmholtz resonant cavity array. Ultrasound is used as the "excitation source" and the Helmholtz resonant cavity array is used as the "sensor". By utilizing the active detection capability of ultrasound and the resonance enhancement characteristics of the Helmholtz resonant cavity, foreign object detection between subway platform doors and train doors can be achieved. Summary of the Invention

[0010] The purpose of this invention is to provide a platform screen door gap detection system and method based on acoustic coordination, which uses ultrasonic waves as the "excitation source" and a Helmholtz resonant cavity array as the "sensor". By utilizing the active detection capability of ultrasonic waves and the resonance enhancement characteristics of the Helmholtz resonant cavity, foreign objects between subway platform screen doors and train doors can be detected, thereby solving the technical problems pointed out in the background art.

[0011] This invention is achieved through the following technical solution: a platform screen door gap detection system based on acoustic coordination, comprising:

[0012] An ultrasonic transmitting unit is located at one end of the platform screen door and is configured to construct a detection sound field in the gap between the platform screen door and the platform screen door.

[0013] The Helmholtz resonant cavity array is vertically installed on the inside of the platform door. It consists of several Helmholtz resonant cavities arranged in a two-dimensional plane, with the openings of the Helmholtz resonant cavities all facing the sound field being detected.

[0014] Several piezoelectric sensors are arranged one-to-one with several of the Helmholtz resonant cavities, and are all located in the closed cavity of the Helmholtz resonant cavity.

[0015] The controller has its electrical signal input terminal connected to the electrical signal output terminals of several piezoelectric sensors, and its signal output terminal connected to the signal input terminal of the platform door or train door control system.

[0016] According to a preferred embodiment, the ultrasonic transmitting unit includes a first ultrasonic transmitting device and a second ultrasonic transmitting device, wherein the first ultrasonic transmitting device is disposed at the top of the platform door and the second ultrasonic transmitting device is disposed at the bottom of the platform door.

[0017] According to a preferred embodiment, the first ultrasonic transmitter and the second ultrasonic transmitter are respectively located in the middle of their corresponding positions, jointly constructing a detection sound field covering a key area within a set range on both sides of the door gap.

[0018] According to a preferred embodiment, the first ultrasonic transmitter and the second ultrasonic transmitter are configured to transmit asynchronously.

[0019] According to a preferred embodiment, the Helmholtz resonant cavity is composed of a cylindrical outer cavity and a cylindrical inner cavity, wherein the cylindrical inner cavity is nested inside the cylindrical outer cavity and is coaxial with the cylindrical outer cavity.

[0020] According to a preferred embodiment, the piezoelectric sensor is a piezoelectric ceramic sheet laid at the bottom of a cylindrical inner cavity.

[0021] According to a preferred embodiment, the resonant frequencies of the plurality of Helmholtz resonators all satisfy the following relationship:

[0022]

[0023] In the above formula, This indicates the speed of sound in air. This represents the volume of the hollow cavity inside the cylinder. Indicates the length of the cylindrical outer cavity. This represents the cross-sectional area of ​​the cylindrical outer cavity.

[0024] According to a preferred embodiment, the resonant frequency band of the Helmholtz resonant cavity array covers the range of ultrasonic pulse ultrasonic drift caused by temperature in the ultrasonic transmitting unit.

[0025] According to a preferred embodiment, the pulsed ultrasound is emitted at a frequency of 40 kHz, and the resonant frequency band of the Helmholtz resonant cavity array is from 38 kHz to 42 kHz.

[0026] This invention also provides a method for detecting platform screen door gaps based on acoustic coordination, applied to the platform screen door gap detection system based on acoustic coordination as described above. The method includes the following steps:

[0027] The system emits pulsed ultrasonic waves at a preset frequency to scan the door area in the gap between the platform doors, thus constructing a detection sound field.

[0028] Receive the reflected sound wave signal within the detection sound field and convert the reflected sound wave signal into an electrical signal;

[0029] The amplitude change of the electrical signal is compared with the reference value to determine whether there are foreign objects in the detection sound field. When a foreign object is found, a warning signal is sent to the platform door or train door control system to trigger the interlocking protection mechanism.

[0030] The technical solution of the platform door gap detection system and method based on acoustic coordination provided by the present invention has at least the following advantages and beneficial effects: (1) The ultrasonic frequency is higher than 20kHz, which is separated from the audible noise of 20Hz-20kHz in the subway environment in the frequency domain. Therefore, the platform door gap detection method is less affected by environmental noise and can work stably in the dark environment with good environmental robustness; (2) The present invention utilizes the active detection capability of ultrasonic waves and the resonance enhancement characteristics of the Helmholtz resonant cavity. On the one hand, it can avoid environmental interference, and on the other hand, it can screen and enhance the changes in the amplitude of the sound signal caused by foreign objects, especially capturing subtle changes in the amplitude of the sound signal, and synergistically improving the detection sensitivity, thereby effectively detecting small foreign objects in the gap of subway platform doors; (3) The technical cost of ultrasonic emission technology is low, and the manufacturing technology of Helmholtz resonant cavity is mature and reliable, supporting mass production. Therefore, the overall hardware cost and maintenance cost of the present invention are lower. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the deployment of the platform door gap detection system based on acoustic coordination provided in Embodiment 1 of the present invention;

[0032] Figure 2 This is a schematic diagram of a two-dimensional plane structure provided in Embodiment 1 of the present invention;

[0033] Figure 3 This is a top view of the platform door clearance provided in Embodiment 2 of the present invention;

[0034] Figure 4 This is a flowchart illustrating the acoustic coordination-based platform door gap detection method provided in Embodiment 4 of the present invention.

[0035] Reference numerals: 100-Platform door gap, 200-First ultrasonic transmitter, 300-Second ultrasonic transmitter, 400-Helmholtz resonant cavity array, 410-Helmholtz resonant cavity, 411-Cylindrical outer cavity, 412-Cylindrical inner cavity, 413-Piezoelectric sensor, 500-Car door, 600-Platform door, 700-Critical area. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0037] Example 1

[0038] This invention provides an acoustically coordinated platform door gap detection system. Figure 1 See the schematic diagram of the deployment of the acoustically coordinated platform screen door gap detection system. Figure 1 As shown, the acoustically coordinated platform door gap detection system includes an ultrasonic transmitting unit, a Helmholtz resonant cavity array 400, several piezoelectric sensors 413, and a controller.

[0039] The ultrasonic transmitting unit is located at one end of the platform door 600 and serves as an "excitation source". It is configured to transmit pulsed ultrasonic waves of a preset frequency to scan the area of ​​the vehicle door 500 in the platform door gap 100 and construct a detection sound field in the platform door gap 100.

[0040] It should also be noted that before emitting pulsed ultrasonic waves, the emission angle needs to be adjusted according to the height and width of the platform door gap 100 to ensure that the pulsed ultrasonic waves can completely cover the platform door gap 100. During the emission process, the pulsed ultrasonic waves can be emitted periodically to maintain the stability of the detection sound field.

[0041] To avoid potential non-audible interference in the subway environment, this embodiment sets the transmission parameters of the pulsed ultrasound to a frequency of 40kHz, a pulse width of 50μs, and a pulse interval of 20ms. No specific limitations are imposed on these transmission parameters; they can be adjusted based on the actual situation of a 100mm platform screen door gap. Specifically, an ultrasonic frequency higher than 20kHz is frequency-separated from the 20Hz-20kHz audible noise in the subway environment, thus minimizing interference from subway noise and allowing for stable operation in dark environments, demonstrating excellent environmental robustness.

[0042] Furthermore, the Helmholtz resonant cavity array 400 is vertically mounted inside the platform screen door 600; in a preferred embodiment, see... Figure 2 As shown, the Helmholtz resonant cavity array 400 is composed of several Helmholtz resonant cavities 410 arranged in a two-dimensional plane connected in parallel, and the openings of several Helmholtz resonant cavities 410 all face the sound field being detected.

[0043] As a "sensor", the Helmholtz resonant cavity 410 is used to receive reflected sound wave signals in the detection sound field. In this embodiment, the active detection capability of ultrasound and the resonance enhancement characteristics of the Helmholtz resonant cavity 410 are used together to realize the detection of the platform door gap 100.

[0044] When a pulsed ultrasonic wave propagates within the platform screen door gap 100, if there are no foreign objects in the gap, the wave will propagate to the door 500. Since the door 500 is metal, most of the pulsed ultrasonic waves will be reflected and transmitted back to the Helmholtz resonator 410. At this time, the amplitude of the reflected sound wave acquired by the Helmholtz resonator 410 remains relatively stable. However, if there are foreign objects in the platform screen door gap 100, such as passenger limbs, personal belongings, or clothing, the reflection, scattering, and absorption characteristics of the pulsed ultrasonic wave will change depending on the material and shape of the object due to the difference in acoustic impedance. This will cause a significant change in the amplitude of the reflected sound wave transmitted back to the Helmholtz resonator 410. For example, human tissue will significantly attenuate the amplitude of the reflected sound wave, metallic foreign objects will cause a large change in the amplitude of the reflected sound wave, and flexible fabrics will significantly reduce the amplitude of the reflected sound wave. The resonance enhancement characteristics of the Helmholtz resonator 410 will significantly amplify this amplitude change.

[0045] Furthermore, a number of piezoelectric sensors 413 are arranged one-to-one with a number of Helmholtz resonant cavities 410, and are all located within the closed cavity of the Helmholtz resonant cavity 410. With the help of the resonant amplification effect of the Helmholtz resonant cavity 410, the ultrasonic energy reflected back to the closed cavity is enhanced, thereby significantly increasing the sound pressure acting on the piezoelectric sensor 413, amplifying the amplitude of the output electrical signal, and effectively improving the detection sensitivity of the system.

[0046] In this embodiment, the reflected sound wave signal, after being filtered and enhanced by the Helmholtz resonant cavity 410, is converted into an electrical signal by a piezoelectric sensor 413. Specifically, after being enhanced by the Helmholtz resonant cavity 410, the reflected sound wave signal acts on the surface of the piezoelectric sensor 413, at which time the piezoelectric sensor 413 generates a charge signal due to the piezoelectric effect. Optionally, this charge signal can be further amplified by an amplifier and finally uploaded to the controller for analysis. In addition, bandpass filters, analog-to-digital converters, etc. can be used to process the charge signal to filter out environmental noise, which will not be elaborated on here.

[0047] It should be noted that when there are foreign objects in the platform door gap 100, the foreign objects will change the propagation characteristics of the pulsed ultrasonic waves, causing the signal amplitude of the reflected sound waves reaching the Helmholtz resonant cavity 410 to change. The resonance enhancement characteristics of the Helmholtz resonant cavity 410 will significantly amplify this amplitude change, and at the same time, it will also cause a significant change in the amplitude of the electrical signal output by the piezoelectric acoustic sensor.

[0048] Specifically, in this embodiment, the amplitude of the electrical signal received when there are no foreign objects is used as the reference value. The change in the amplitude of the electrical signal received in real time is compared with the reference value. When the change in the amplitude of the electrical signal in a certain area exceeds the set threshold, it can be determined that there are foreign objects in the platform door gap 100.

[0049] Furthermore, in this embodiment, the electrical signal input terminal of the controller is connected to the electrical signal output terminals of several piezoelectric sensors 413 to obtain electrical signals from the piezoelectric sensors 413. The signal output terminal of the controller is connected to the signal input terminal of the platform door or train door control system to provide feedback on the analysis results of the electrical signals, thereby triggering the interlocking protection mechanism. Further details are omitted here.

[0050] In summary, this invention utilizes the active detection capability of ultrasound and the resonant enhancement characteristics of the Helmholtz resonator 410. On the one hand, it can avoid environmental interference, and on the other hand, it can filter and enhance the changes in acoustic signal amplitude caused by foreign objects, especially capturing subtle changes in acoustic signal amplitude, thereby synergistically improving detection sensitivity. This enables the effective detection of small foreign objects in the gap 100 of the subway platform door. In addition, the technical cost of ultrasonic emission technology is low, and the manufacturing technology of the Helmholtz resonator 410 is mature and reliable, supporting mass production. Therefore, the overall hardware and maintenance costs of this invention are lower.

[0051] Example 2

[0052] This embodiment describes the configuration of the ultrasonic transmitting unit based on the technical solution provided in Embodiment 1:

[0053] In this embodiment, to ensure the effectiveness of the detection range, the ultrasonic transmitting unit includes a first ultrasonic transmitting device 200 and a second ultrasonic transmitting device 300. The first ultrasonic transmitting device 200 is located at the top of the platform door 600, and the second ultrasonic transmitting device 300 is located at the bottom of the platform door 600.

[0054] In one specific embodiment of this invention, the first ultrasonic transmitter 200 is installed on the top beam of the platform door 600, 0.1m to 0.2m from the top of the door 500. The pulsed ultrasonic waves emitted by the first ultrasonic transmitter 200 propagate downwards in a fan shape or at a specific diffusion angle to completely cover the entire height of the door 500. Preferably, its beam emission angle is designed to be 30° to 45° in the vertical direction. The second ultrasonic transmitter 300 is installed on the platform. Preferably, its beam emission angle is designed to be 0° to 45° in the vertical direction. The above beam emission angles can be adaptively adjusted according to the actual platform conditions, and no specific limitation is made here.

[0055] Furthermore, to avoid interference between the pulsed ultrasonic waves emitted by the first ultrasonic transmitter 200 and the second ultrasonic transmitter 300, in this embodiment, the first ultrasonic transmitter 200 and the second ultrasonic transmitter 300 are configured to emit asynchronously. Specifically, based on a polling emission mechanism, the emission interval can be set to ensure that the reflected sound wave signal corresponding to the first ultrasonic transmitter 200 is received before the second ultrasonic transmitter 300 is emitted, thus avoiding time domain superposition. The timing control is implemented by a timer, which will not be elaborated on here.

[0056] Furthermore, considering that almost all obstacles within the 100mm gap between platform screen doors are caused by objects being caught between the platform screen door 600mm or the train door 500mm, see [reference needed]. Figure 3As shown, the first ultrasonic transmitter 200 and the second ultrasonic transmitter 300 are respectively placed in the middle of their corresponding positions to jointly construct a detection sound field covering the key area 700 within a set range on both sides of the gap of the car door 500.

[0057] Example 3

[0058] This embodiment further illustrates the structure of the Helmholtz resonant cavity 410 based on the technical solution provided in any one of Embodiments 1 to 2:

[0059] In this embodiment, the Helmholtz resonant cavity 410 is composed of a cylindrical outer cavity 411 and a cylindrical inner cavity 412. The cylindrical inner cavity 412 is nested inside the cylindrical outer cavity 411 and is coaxial with the cylindrical outer cavity 411. The opening of the cylindrical outer cavity 411 faces the detection sound field to efficiently receive reflected sound wave signals.

[0060] The piezoelectric sensor 413 is a piezoelectric ceramic sheet laid at the bottom of the cylindrical inner cavity 412, used to convert the reflected sound wave signal in the Helmholtz resonant cavity 410 into an electrical signal related to the sound wave frequency and amplitude.

[0061] The resonant frequencies of several of the Helmholtz resonators 410 satisfy the following relationship:

[0062]

[0063] In the above formula, This indicates the speed of sound in air. This represents the volume of the cylindrical internal cavity 412. This indicates the length of the cylindrical outer cavity 411. This represents the cross-sectional area of ​​the cylindrical outer cavity 411.

[0064] Furthermore, the propagation speed of ultrasound in the air is affected by the ambient temperature. Temperature changes cause the frequency of the Helmholtz resonant cavity 410 to shift, weakening its resonance enhancement effect and thus affecting the detection accuracy. To eliminate the impact of temperature changes on detection accuracy, the resonant frequency band of the Helmholtz resonant cavity array 400 in this embodiment covers the range of ultrasonic pulse ultrasonic drift caused by temperature, so as to achieve resonance frequency band enhancement across the entire temperature range, for example, from 0°C to 40°C.

[0065] It should be noted that a temperature change from 0℃ to 40℃ will cause the resonant frequency to shift by ±1.3kHz. For example, at a temperature of 0℃, assuming the ultrasonic transmitter's emission frequency is 40kHz, the speed of sound is approximately 331.4m / s, and the resonant frequency can be calculated from the formula to be approximately 38.6kHz. When the temperature is 40℃, the speed of sound is approximately 355.68m / s, and the resonant frequency can be calculated from the formula to be approximately 41.4kHz.

[0066] Assuming a target frequency of 40kHz, the diameter of the cylindrical outer cavity 411 can be set to 1mm and the height to 0.53mm, while the diameter of the cylindrical inner cavity 412 can be set to 1.5mm and the height to 0.6mm. The Helmholtz resonant cavity 410 formed by these parameters corresponds to a 40kHz transmission frequency without temperature deviation, achieving a resonance enhancement effect for the 40kHz reflected sound wave signal. In this embodiment, based on 5℃, the Helmholtz resonant cavity array 400 is provided with a total of 9 sets of Helmholtz resonant cavities 410, which cover the resonance frequency band from 38kHz to 42kHz through parallel connection.

[0067] It should be noted that, through the above design, on the one hand, the full height and width range of the 500mm gap in the car door can be covered, eliminating the spatial blind spot of single-cavity detection; on the other hand, the Helmholtz resonant cavity array 400 is used to achieve full-temperature range resonant frequency band enhancement, which can eliminate the influence of ambient temperature. By comparing the differences in signal amplitude changes of different cavities, the location of foreign objects can be accurately located; in addition, by superimposing the resonant enhancement effects of each cavity, the weak acoustic signal changes caused by foreign objects are amplified, significantly improving the system's ability to detect small foreign objects, and providing clearer feature input for subsequent signal conversion of the piezoelectric sensor 413 and controller analysis.

[0068] Example 4

[0069] This embodiment, based on the technical solutions provided in any one of embodiments 1 to 3, provides a method for detecting platform screen door gaps based on acoustic coordination. This method is applied to the platform screen door gap detection system based on acoustic coordination provided in any one of embodiments 1 to 3. (See also...) Figure 4 As shown, the method includes the following steps:

[0070] Step 1: Transmit pulsed ultrasonic waves of a preset frequency to scan the door area within the platform door gap 100 to construct a detection sound field;

[0071] Step 2: Receive the reflected sound wave signal within the detection sound field and convert the reflected sound wave signal into an electrical signal;

[0072] It should be noted that, since the resonant frequency band of the Helmholtz resonant cavity array 400 covers the range of ultrasonic pulse ultrasonic drift caused by temperature, when there are no foreign objects in the platform door gap 100, the Helmholtz resonant cavity 410 receives the reflected sound wave signal with a fixed frequency and amplitude, that is, the ultrasonic frequency and amplitude reflected back through the door 500, and resonates and absorbs the reflected sound wave signal; however, when there are foreign objects in the platform door gap 100, the foreign objects will change the propagation characteristics of the pulse ultrasonic waves, causing the amplitude of the reflected sound wave signal reaching the Helmholtz resonant cavity 410 to change, and the resonance enhancement characteristics of the Helmholtz resonant cavity 410 will significantly amplify this amplitude change.

[0073] Step 3: Compare the amplitude change of the electrical signal with the reference value to determine whether there are foreign objects in the detection sound field;

[0074] In this embodiment, the amplitude of the reflected sound wave signal received when there are no foreign objects is used as the reference value. The changes in the amplitude of the reflected sound wave signal received in real time are compared with the reference value. When the change in the amplitude of the reflected sound wave signal in a certain area exceeds a set threshold, it can be determined that there are foreign objects in the platform door gap 100. The set threshold can be adjusted according to the type of foreign object and the detection accuracy requirements. Thus, while determining the presence of foreign objects, the type of foreign object can also be determined. Regarding the setting of the reference value, in some embodiments, several sets of pulsed ultrasonic waves can be continuously emitted, the amplitude of each set of reflected sound wave signals can be recorded, and the average value after removing the maximum and minimum values ​​can be taken as the initial reference. Furthermore, the reference value is automatically calibrated at regular intervals. The average amplitude of the reflected sound wave when there are no foreign objects is compared with the initial reference value. If the difference between the two is too large, the initial reference value is updated using the current average amplitude of the reflected sound wave to ensure that the reference value always matches the actual state of the platform door gap 100.

[0075] Step 4: When a foreign object is confirmed to be present, send a warning signal to the platform door or train door control system to trigger the interlocking protection mechanism and prevent the foreign object from being caught in the train door 500 or platform door 600.

[0076] In this embodiment, the amplitude of the reflected sound wave signal received when there are no foreign objects is used as the reference value. The changes in the amplitude of the reflected sound wave signal received in real time are compared with the reference value. When the change in the amplitude of the reflected sound wave signal in a certain area exceeds a set threshold, it can be determined that there are foreign objects in the platform door gap 100. The set threshold can be adjusted according to the type of foreign object and the detection accuracy requirements. Thus, while determining the presence of foreign objects, the type of foreign object can also be determined. Regarding the setting of the reference value, in some embodiments, several sets of pulsed ultrasonic waves can be continuously emitted, the amplitude of each set of reflected sound wave signals can be recorded, and the average value after removing the maximum and minimum values ​​can be taken as the initial reference. Furthermore, the reference value is automatically calibrated at regular intervals. The average amplitude of the reflected sound wave when there are no foreign objects is compared with the initial reference value. If the difference between the two is too large, the initial reference value is updated using the current average amplitude of the reflected sound wave to ensure that the reference value always matches the actual state of the platform door gap 100.

[0077] Regarding the determination of foreign object types, it should be noted that the physical properties of different foreign objects, such as material, density, and surface roughness, will cause the amplitude changes of reflected sound waves to exhibit regular differences. In some embodiments, metallic clothing has a large difference in acoustic impedance compared to air, resulting in high ultrasonic reflectivity, small amplitude attenuation, and small amplitude changes in reflected sound waves. Fabric / flexible foreign objects, such as clothing and plastic bags, have strong ultrasonic absorption, resulting in significant attenuation of reflected sound wave amplitude and large amplitude changes. Human tissues, such as fingers and limbs, have strong ultrasonic penetration, resulting in moderate amplitude attenuation and moderate amplitude changes in reflected sound waves. Hard non-metallic materials, such as plastic bottles and cards, have reflectivity between metal and fabric, and their amplitude changes also fall between those of metal and fabric. Therefore, this embodiment sets multiple threshold levels, each corresponding to a different type of foreign object, thereby enabling the differentiation of foreign object types while simultaneously determining their presence.

[0078] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A platform screen door gap detection system based on acoustic coordination, characterized in that, include: An ultrasonic transmitting unit is located at one end of the platform door (600) and is configured to construct a detection sound field in the platform door gap (100); The Helmholtz resonant cavity array (400) is vertically installed on the inside of the platform door (600) and is composed of several Helmholtz resonant cavities (410) arranged in a two-dimensional plane connected in parallel. The openings of several Helmholtz resonant cavities (410) all face the sound field being detected. A number of piezoelectric sensors (413) are arranged one-to-one with a number of Helmholtz resonant cavities (410), and are all located in the closed cavity of the Helmholtz resonant cavity (410). The controller has an electrical signal input terminal connected to the electrical signal output terminals of several piezoelectric sensors (413), and the signal output terminal of the controller is connected to the signal input terminal of the platform door or vehicle door control system.

2. The platform screen door gap detection system based on acoustic coordination as described in claim 1, characterized in that, The ultrasonic transmitting unit includes a first ultrasonic transmitting device (200) and a second ultrasonic transmitting device (300). The first ultrasonic transmitting device (200) is located at the top of the platform door (600), and the second ultrasonic transmitting device (300) is located at the bottom of the platform door (600).

3. The platform screen door gap detection system based on acoustic coordination as described in claim 2, characterized in that, The first ultrasonic transmitter (200) and the second ultrasonic transmitter (300) are respectively located in the middle of their respective positions, and together they construct a detection sound field covering the key area (700) within a set range on both sides of the gap of the car door (500).

4. The platform screen door gap detection system based on acoustic coordination as described in claim 3, characterized in that, The first ultrasonic transmitter (200) and the second ultrasonic transmitter (300) are configured to emit asynchronously.

5. The platform screen door gap detection system based on acoustic coordination as described in any one of claims 1 to 4, characterized in that, The Helmholtz resonant cavity (410) is composed of a cylindrical outer cavity (411) and a cylindrical inner cavity (412). The cylindrical inner cavity (412) is nested inside the cylindrical outer cavity (411) and is coaxial with the cylindrical outer cavity (411).

6. The platform screen door gap detection system based on acoustic coordination as described in claim 5, characterized in that, The piezoelectric sensor (413) is a piezoelectric ceramic sheet laid at the bottom of the cylindrical inner cavity (412).

7. The platform screen door gap detection system based on acoustic coordination as described in claim 5, characterized in that, The resonant frequencies of several of the Helmholtz resonators (410) satisfy the following relationship: In the above formula, This indicates the speed of sound in air. This represents the volume of the cylindrical internal cavity (412). This indicates the length of the cylindrical outer cavity (411). This represents the cross-sectional area of ​​the cylindrical outer cavity (411).

8. The platform screen door gap detection system based on acoustic coordination as described in claim 7, characterized in that, The resonant frequency band of the Helmholtz resonant cavity array (400) covers the range of ultrasonic pulse ultrasonic drift caused by temperature in the ultrasonic transmitting unit.

9. The platform screen door gap detection system based on acoustic coordination as described in claim 8, characterized in that, The pulsed ultrasound is emitted at a frequency of 40 kHz, and the resonant frequency band of the Helmholtz resonant cavity array (400) is from 38 kHz to 42 kHz.

10. A method for detecting platform screen door gaps (100) based on acoustic coordination, characterized in that, The method, applied to the acoustically coordinated platform door gap detection system as described in any one of claims 1 to 9, comprises the following steps: Transmit pulsed ultrasonic waves of a preset frequency to scan the door area in the gap (100) between the platform doors and construct a detection sound field; Receive the reflected sound wave signal within the detection sound field and convert the reflected sound wave signal into an electrical signal; The amplitude change of the electrical signal is compared with the reference value to determine whether there are foreign objects in the detection sound field. When a foreign object is found, a warning signal is sent to the platform door or train door control system to trigger the interlocking protection mechanism.

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