Platform door gap detection system and method based on acoustic collaboration

Abstract

The invention relates to the technical field of platform door gap detection, in particular to a platform door gap detection system and method based on acoustic collaboration, and the system comprises an ultrasonic transmitting unit which is arranged at one end of a platform door; the Helmholtz resonant cavity array is vertically mounted on the inner side of the platform door and is formed by connecting a plurality of Helmholtz resonant cavities in parallel, and the Helmholtz resonant cavities are arranged in a two-dimensional plane; the plurality of piezoelectric sensors are arranged in one-to-one correspondence with the plurality of Helmholtz resonant cavities and are all arranged in the closed cavity bodies of the Helmholtz resonant cavities; and the electric signal input end of the controller is connected with the electric signal output ends of the plurality of piezoelectric sensors. By utilizing the active detection capability of ultrasonic waves and the resonance enhancement characteristic of the Helmholtz resonant cavity, environmental interference can be avoided, acoustic signal amplitude changes caused by foreign matters can be screened and enhanced, particularly fine acoustic signal amplitude changes can be captured, and the detection sensitivity can be cooperatively improved, so that fine foreign matters in the gap of the subway platform door can be effectively detected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of platform door gap detection, in particular to a platform door gap detection system and method based on acoustic cooperation. BACKGROUND

[0002] In recent years, with the rapid development of society and the acceleration of urbanization process, the city continues to expand and the population continues to grow. The urban rail transit, taking the subway as the core, has become the key support to alleviate the urban traffic pressure with the advantages of large capacity, fast speed, safety and punctuality, energy saving and environmental protection, and has become the backbone of public transportation in modern large and medium-sized cities. With the in-depth operation of the rail transit network, the operation safety guarantee has become the core issue of the industry development.

[0003] In the subway safety operation system, ensuring the safety of passengers waiting and taking the train is the focus of managers and researchers. The platform door, as a key equipment to ensure the safety of passengers waiting, must have a certain gap between the train body due to the design and installation to meet the gauge requirements. This gap is not only the core area for passengers to get on and off the train, but also the high-incidence area of being caught and caught accidents, especially during the peak passenger period. The event of passengers or personal belongings being caught in the gap between the platform door and the train door often occurs. Therefore, it is very important to detect foreign objects in the gap before the train departs to ensure the safety of passengers and property and improve the efficiency of train operation.

[0004] At the same time, with the evolution of China's rail transit technology, full-automatic unmanned driving has become an important direction for future development, and the automatic foreign object detection technology of the platform door and the train door gap is a key link to support this trend, which has important practical significance.

[0005] Currently, the protective measures of the platform door control system at home and abroad mainly include physical protection technology and automatic detection technology. Among them, the physical protection technology that has been put into application includes anti-pinch baffle, anti-climb baffle and lookout light belt, etc. This kind of measure has the advantages of low cost, simple structure and easy installation, which can effectively reduce the risk of passenger injury and improve the ability of rail intrusion, but the physical protection technology has obvious limitations such as lack of active warning capability, low detection efficiency, difficulty in finding and processing small objects in the gap in time, etc., which leads to a high risk of damage to passenger accessories. Therefore, it is necessary to combine physical protection technology with intelligent monitoring technology to perfect the subway safety protection system.

[0006] The automatic detection technology of subway platform door and train door foreign matter mainly includes infrared light curtain, laser detection, laser scanning and machine vision, etc. Among them, the infrared light curtain detection forms an infrared warning line through the transmitter and receiver, and works based on the shielding alarm mechanism. However, the infrared light dispersion range is small, which is not suitable for long-distance detection, and is easily disturbed by the environment to produce false alarms, and the identification ability of small and medium-sized gap objects is limited. The principle of laser detection is similar to that of infrared light curtain, but the laser has stronger light condensation, and can realize long-distance penetrating detection. In practical application, the laser transmitter and receiver are usually installed on the ground outside the head and tail doors of the platform, and after the platform door is closed, whether the gap exists foreign matter is judged by detecting whether the laser beam is blocked. Laser scanning is based on the time-of-flight measurement principle, and is usually installed on the top of the platform door. The transmitter emits a single or multi-layer fan-shaped beam, which is reflected to the receiver through the light belt at the anti-falling gap of the platform door bottom. The transmission time is calculated to identify foreign matter. Compared with infrared and laser transmission technology, its stability is better, and it is suitable for curved platforms, but the measurement information is sparse and the cost is high, and the detection range is usually limited to within 15 meters. The detection method based on machine vision generally uses the vertical light belt at the train end door or the light belt at the anti-falling gap at the bottom of the platform door as the background reference, collects the image containing the complete light belt through the camera, analyzes the integrity of the light belt based on the image recognition algorithm to judge the foreign matter, but it is easily disturbed by environmental factors such as light and weather.

[0007] In summary, the detection of foreign matter in the gap between the subway platform door and the train is a technical difficulty in the field of urban rail transit. The existing infrared, laser and other technologies generally have the problems of large detection blind area, weak anti-environmental interference ability and high cost.

[0008] Ultrasonic wave is a high-frequency sound wave with a frequency higher than 20 kHz, which has strong directivity and energy concentration characteristics, and is widely used in distance detection and obstacle identification. In the subway environment, noise such as ventilation system, train broadcast and passenger conversation is mainly distributed in the audible sound range of 20 Hz ~ 20 kHz, which is separated from ultrasonic wave in frequency domain, so ultrasonic wave is less directly disturbed by subway environment noise. The Helmholtz resonator is a kind of acoustic structure based on acoustic resonance principle. When the frequency of sound wave is consistent with the natural frequency of the cavity, resonance will occur. This resonance characteristic can significantly amplify the sound wave of a specific frequency while suppressing other frequency components, thereby realizing narrowband filtering function.

[0009] Based on this, the present application proposes an acoustic detection method based on ultrasonic wave and Helmholtz resonator array cooperation. The ultrasonic wave is used as the "excitation source", and the Helmholtz resonator array is used as the "sensor". The active detection capability of ultrasonic wave and the resonance enhancement characteristic of Helmholtz resonator are used to realize the detection of foreign matter between the subway platform door and the train door. SUMMARY

[0010] The purpose of the present application is to provide a platform door gap detection system and method based on acoustic cooperation, which uses ultrasonic waves as the "excitation source" and a Helmholtz resonator array as the "sensor", and uses the active detection capability of ultrasonic waves and the resonance enhancement characteristics of the Helmholtz resonator to realize foreign object detection between the subway platform door and the train door, so as to solve the technical problems pointed out in the background art.

[0011] The present application is realized by the following technical scheme: a platform door gap detection system based on acoustic cooperation, comprising: An ultrasonic wave emitting unit is arranged at one end of the platform door and is configured to build a detection sound field in the platform door gap; A Helmholtz resonator array is vertically installed on the inner side of the platform door and is composed of a plurality of Helmholtz resonators arranged in a two-dimensional plane, and the openings of the plurality of Helmholtz resonators are all directed towards the detection sound field; A plurality of piezoelectric sensors are arranged one-to-one corresponding to the plurality of Helmholtz resonators and are all arranged in the closed cavities of the Helmholtz resonators; A controller is connected to the electrical signal output ends of the plurality of piezoelectric sensors through the electrical signal input end, and the signal output end of the controller is connected to the signal input end of the platform door or train door control system.

[0012] According to a preferred embodiment, the ultrasonic wave emitting unit comprises a first ultrasonic wave emitting device and a second ultrasonic wave emitting device, the first ultrasonic wave emitting device is arranged at the top of the platform door, and the second ultrasonic wave emitting device is arranged at the bottom of the platform door.

[0013] According to a preferred embodiment, the first ultrasonic wave emitting device and the second ultrasonic wave emitting device are respectively arranged in the middle of the corresponding positions and jointly build a detection sound field covering the key areas within the set range on both sides of the train door gap.

[0014] According to a preferred embodiment, the first ultrasonic wave emitting device and the second ultrasonic wave emitting device are configured to emit asynchronously.

[0015] According to a preferred embodiment, the Helmholtz resonator is composed of a cylindrical outer cavity and a cylindrical inner cavity, the cylindrical inner cavity is nested in the inside of the cylindrical outer cavity and is coaxial with the cylindrical outer cavity.

[0016] According to a preferred embodiment, the piezoelectric sensor is a piezoelectric ceramic sheet laid on the bottom of the cylindrical inner cavity.

[0017] According to a preferred embodiment, the resonance frequencies of the plurality of Helmholtz resonators all satisfy the following relationship:

[0018] In the above formula, represents the speed of sound in air, represents the volume of the cylindrical inner cavity, represents the length of the cylindrical outer cavity, represents the cross-sectional area of the cylindrical outer cavity.

[0019] According to a preferred embodiment, the resonance frequency band of the Helmholtz resonator array covers the pulse ultrasonic wave drift range of the ultrasonic wave emission unit caused by temperature.

[0020] According to a preferred embodiment, the emission frequency of the pulse ultrasonic wave is 40 kHz, and the resonance frequency band range of the Helmholtz resonator array is 38 kHz to 42 kHz.

[0021] The application also provides a platform door gap detection method based on acoustic synergy, which is applied to the platform door gap detection system based on acoustic synergy as described above, and the method comprises the following steps: Emitting a pulse ultrasonic wave of a preset frequency to scan the vehicle door area in the platform door gap to construct a detection sound field; Receiving a reflected sound wave signal in the detection sound field and converting the reflected sound wave signal into an electric signal; Comparing the amplitude change of the electric signal with a reference value to determine whether there is a foreign object in the detection sound field, and sending an alarm signal to the platform door or vehicle door control system to trigger an interlocking protection mechanism when it is determined that there is a foreign object.

[0022] The technical scheme of the platform door gap detection system and method based on acoustic synergy provided by the application has at least the following advantages and beneficial effects: (1) The ultrasonic wave frequency is higher than 20 kHz, which is separated from the audible sound noise of 20 Hz-20 kHz in the subway environment in the frequency domain, so that the platform door gap detection method is less disturbed by environmental noise and can work stably in a dark environment, and the environmental robustness is good; (2) The application utilizes the active detection capability of the ultrasonic wave and the resonance enhancement characteristics of the Helmholtz resonator, which can avoid environmental interference on one hand and screen and enhance the amplitude change of the sound signal caused by the foreign object on the other hand, especially capture the subtle amplitude change of the sound signal, and cooperatively improve the detection sensitivity, so that the small foreign object in the platform door gap of the subway can be effectively detected; (3) The technical cost of the ultrasonic wave emission technology is low, and the manufacturing technology of the Helmholtz resonator is mature and reliable, which supports batch manufacturing, so that the overall hardware cost and maintenance cost of the application are lower. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The layout schematic diagram of the platform door gap detection system based on acoustic synergy provided for the embodiment 1 of the application; Figure 2 The structure schematic diagram of the two-dimensional plane provided for the embodiment 1 of the application; Figure 3 The plan view of the platform door gap provided for the embodiment 2 of the present application; Figure 4 The flow chart of the platform door gap detection method based on acoustic synergy provided for the embodiment 4 of the present application; The figure shows that: 100-platform door gap, 200-first ultrasonic wave emitting device, 300-second ultrasonic wave emitting device, 400-Helmholtz resonator array, 410-Helmholtz resonator, 411-cylindrical outer cavity, 412-cylindrical inner cavity, 413-piezoelectric sensor, 500-door, 600-platform door, 700-critical area. DETAILED DESCRIPTION

[0024] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0025] Embodiment 1 The embodiments of the present application provide a platform door gap detection system based on acoustic synergy, Figure 1 The figure shows that: 100-platform door gap, 200-first ultrasonic wave emitting device, 300-second ultrasonic wave emitting device, 400-Helmholtz resonator array, 410-Helmholtz resonator, 411-cylindrical outer cavity, 412-cylindrical inner cavity, 413-piezoelectric sensor, 500-door, 600-platform door, 700-critical area. Figure 1 The figure shows that: 100-platform door gap, 200-first ultrasonic wave emitting device, 300-second ultrasonic wave emitting device, 400-Helmholtz resonator array, 410-Helmholtz resonator, 411-cylindrical outer cavity, 412-cylindrical inner cavity, 413-piezoelectric sensor, 500-door, 600-platform door, 700-critical area.

[0026] The ultrasonic wave emitting unit is arranged at one end of the platform door 600 as an "excitation source", which is configured to emit pulsed ultrasonic waves of a preset frequency to scan the door 500 area in the platform door gap 100, and to construct a detection sound field in the platform door gap 100.

[0027] It should be further noted that before emitting the pulsed ultrasonic waves, the emitting 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 emitting process, the pulsed ultrasonic waves can be emitted in a periodic manner to maintain the stability of the detection sound field.

[0028] In order to avoid the non-audible interference that may exist in the subway environment, the emission parameters of the pulse ultrasonic wave in the embodiment are set as follows: frequency 40 kHz, pulse width 50 μs, and pulse interval 20 ms. The emission parameters are not specifically limited here, and can be adjusted according to the actual situation of the platform door gap 100. Specifically, the ultrasonic wave frequency is higher than 20 kHz, and is separated from the audible noise of 20 Hz-20 kHz in the subway environment in the frequency domain, so it is less disturbed by the noise in the subway environment, and can work stably in a dark environment, and has good environmental robustness.

[0029] Further, the Helmholtz resonator array 400 is vertically installed on the inner side of the platform door 600. In a preferred embodiment, as shown in FIG. 4, the Helmholtz resonator array 400 is composed of a plurality of Helmholtz resonators 410 arranged in a two-dimensional plane in parallel, and the openings of the plurality of Helmholtz resonators 410 are all directed towards the detection sound field. Figure 2

[0030] As a "sensor", the Helmholtz resonator 410 is used to receive the reflected sound wave signal in the detection sound field. The embodiment utilizes the active detection capability of the ultrasonic wave and the resonance enhancement characteristics of the Helmholtz resonator 410 to jointly realize the detection of the platform door gap 100.

[0031] When the pulse ultrasonic wave propagates in the platform door gap 100, if there is no foreign matter in the platform door gap 100 at this time, the pulse ultrasonic wave will propagate to the door 500. Since the door 500 is metal, most of the pulse ultrasonic wave will be reflected by the door 500 and transmitted back to the Helmholtz resonator 410. At this time, the amplitude of the reflected sound wave obtained by the Helmholtz resonator 410 remains in a relatively stable reference state. If there is a foreign matter, such as a passenger's limbs, personal belongings, clothes, etc., in the platform door gap 100 at this time, due to the difference in acoustic resistance of different foreign matters, the reflection, scattering and absorption characteristics of the pulse ultrasonic wave when it contacts the foreign matter will change due to the material and shape of the foreign matter, resulting in a significant change in the amplitude of the reflected sound wave transmitted back to the Helmholtz resonator 410. For example, human tissues will cause a significant attenuation of the amplitude of the reflected sound wave, metal foreign matters will cause a large change in the amplitude of the reflected sound wave, and flexible fabrics will cause a large reduction in the amplitude of the reflected sound wave. The resonance enhancement characteristics of the Helmholtz resonator 410 will significantly amplify this amplitude change.

[0032] Further, a plurality of piezoelectric sensors 413 are arranged one-to-one corresponding to the plurality of Helmholtz resonators 410, and are all arranged in the closed cavities of the Helmholtz resonators 410. With the resonance amplification effect of the Helmholtz resonator 410, the ultrasonic wave energy reflected back to the closed cavity is strengthened, thereby significantly increasing the sound pressure acting on the piezoelectric sensor 413, and amplifying the amplitude of the output electric signal, effectively improving the detection sensitivity of the system. ​

[0033] The embodiment converts the reflected sound wave signal filtered and enhanced by the Helmholtz resonator 410 into an electric signal through the piezoelectric sensor 413; specifically, the reflected sound wave signal is applied to the surface of the piezoelectric sensor 413 after being enhanced by the Helmholtz resonator 410, at which time the piezoelectric sensor 413 generates an electric charge signal due to the piezoelectric effect; optionally, the electric charge signal can be further amplified by an amplifier and finally uploaded to the controller for analysis; in addition, the electric charge signal can be processed by a band-pass filter, an analog-to-digital converter, etc. to filter environmental clutter, which will not be described in detail here.

[0034] It should be noted that when there is a foreign object in the platform door gap 100, the foreign object will change the propagation characteristics of the pulsed ultrasonic wave, causing the signal amplitude of the reflected sound wave reaching the Helmholtz resonator 410 to change, and the resonance enhancement characteristics of the Helmholtz resonator 410 will significantly amplify this amplitude change, and at the same time, the electric signal amplitude output by the piezoelectric acoustic sensor will also change significantly.

[0035] Specifically, in the embodiment, the electric signal amplitude received when there is no foreign object is taken as a reference value, and the change in the real-time received electric signal amplitude is compared with the reference value, and when the electric signal amplitude change in a certain area exceeds a set threshold value, it can be judged that there is a foreign object in the platform door gap 100.

[0036] Further, in the embodiment, the electric signal input end of the controller is connected to the electric signal output end of the piezoelectric sensor 413 for obtaining the electric signal from the piezoelectric sensor 413, and the signal output end of the controller is connected to the signal input end of the platform door or vehicle door control system for feeding back the analysis result of the electric signal to trigger the interlocking protection mechanism, which will not be described in detail here.

[0037] In summary, the present application utilizes the active detection capability of ultrasonic waves and the resonance enhancement characteristics of the Helmholtz resonator 410, which can avoid environmental interference on the one hand and screen and enhance the amplitude change of the sound signal caused by foreign objects on the other hand, especially capturing subtle amplitude changes of the sound signal, thereby improving the detection sensitivity and effectively detecting small foreign objects in the platform door gap 100 of the subway. In addition, the ultrasonic wave emission technology has low technical cost, and the manufacturing technology of the Helmholtz resonator 410 is mature and reliable, supporting batch manufacturing, so the overall hardware cost and maintenance cost of the present application are lower.

[0038] Embodiment 2 The embodiment is based on the technical solution provided in embodiment 1 and describes the setting of the ultrasonic wave emission unit. In the embodiment, to ensure the effectiveness of the detection range, the ultrasonic wave emitting unit comprises a first ultrasonic wave emitting device 200 and a second ultrasonic wave emitting device 300, the first ultrasonic wave emitting device 200 is arranged on the top of the platform door 600, and the second ultrasonic wave emitting device 300 is arranged on the bottom of the platform door 600.

[0039] In an embodiment of the embodiment, the first ultrasonic wave emitting device 200 is installed on the top beam of the platform door 600, 0.1m to 0.2m away from the top of the door 500, the pulse ultrasonic wave emitted by the first ultrasonic wave emitting device 200 propagates downward in a fan shape or a specific diffusion angle to completely cover the full height range of the door 500, and preferably, the beam emission angle in the vertical direction is designed to be 30° to 45°; the second ultrasonic wave emitting device 300 is installed on the platform, and preferably, the beam emission angle in the vertical direction is designed to be 0° to 45°, and the above beam emission angle can be adjusted according to the actual platform, which is not limited here.

[0040] In addition, to avoid interference between the pulse ultrasonic waves emitted by the first ultrasonic wave emitting device 200 and the second ultrasonic wave emitting device 300, in the embodiment, the first ultrasonic wave emitting device 200 and the second ultrasonic wave emitting device 300 are configured to emit asynchronously; specifically, based on the round-robin transmitter mechanism, the interval of emission can be set to ensure that the reflected sound signal corresponding to the first ultrasonic wave emitting device 200 is received before the second ultrasonic wave emitting device 300 is emitted, to avoid time domain superposition; wherein, the timing control is realized by a timer, which is not described here.

[0041] Further, considering that the platform door gap 100 obstacles are basically caused by the platform door 600 or the door 500, as shown in FIG. 2, the first ultrasonic wave emitting device 200 and the second ultrasonic wave emitting device 300 are arranged in the middle of the corresponding position, respectively, to jointly construct a detection sound field covering the key area 700 in the set range on both sides of the door 500 gap. Figure 3

[0042] Embodiment 3 The embodiment is based on any one of the technical solutions provided in embodiments 1 to 2, and further describes the structure of the Helmholtz resonator 410: In the embodiment, the Helmholtz resonator 410 is composed of a cylindrical outer cavity 411 and a cylindrical inner cavity 412, the cylindrical inner cavity 412 is nested in the inside of the cylindrical outer cavity 411 and coaxial with the cylindrical outer cavity 411, and the opening of the cylindrical outer cavity 411 faces the detection sound field to efficiently receive the reflected sound signal.

[0043] ​The piezoelectric sensor 413 is a piezoelectric ceramic sheet arranged on the bottom of the cylindrical inner cavity 412, and is used to convert the reflected acoustic wave signal in the Helmholtz resonant cavity 410 into an electric signal related to the frequency and amplitude of the acoustic wave.

[0044] The resonant frequencies of the Helmholtz resonant cavities 410 satisfy the following relationship:

[0045] In the above formula, represents the speed of sound in air, represents the volume of the cylindrical inner cavity 412, represents the length of the cylindrical outer cavity 411, represents the cross-sectional area of the cylindrical outer cavity 411.

[0046] Further, the propagation speed of the ultrasonic wave in air is affected by the ambient temperature, and the change in temperature causes the frequency of the Helmholtz resonant cavity 410 to shift, weakening the resonance enhancement effect and affecting the detection accuracy. To eliminate the influence of temperature change on detection accuracy, the resonant frequency band of the Helmholtz resonant cavity array 400 in this embodiment covers the range of pulse ultrasonic wave drift caused by temperature, so as to realize resonance band enhancement in the full temperature range, for example, 0℃ to 40℃.

[0047] It should be noted that the temperature change of 0℃ to 40℃ will cause the resonant frequency to shift by ±1.3kHz. For example, when the temperature is 0℃, assuming that the transmission frequency of the ultrasonic wave transmission device is 40kHz, the speed of sound at this time is about 331.4m / s, and the resonant frequency at this time can be calculated by the relationship formula to be about 38.6kHz. When the temperature is 40℃, the speed of sound at this time is about 355.68m / s, and the resonant frequency at this time can be calculated by the relationship formula to be about 41.4kHz.

[0048] Assuming that 40kHz is the target frequency, the diameter of the cylindrical outer cavity 411 can be set to 1mm, the height can be set to 0.53mm, the diameter of the cylindrical inner cavity 412 can be set to 1.5mm, and the height can be set to 0.6mm. The Helmholtz resonant cavity 410 formed by the above parameters corresponds to the 40kHz transmission frequency without temperature deviation, and realizes the resonance enhancement effect of the 40kHz reflected acoustic wave signal. In this embodiment, 9 groups of Helmholtz resonant cavities 410 are provided in the Helmholtz resonant cavity array 400, and the resonant frequency band range of 38kHz to 42kHz is covered by parallel connection.

[0049] It should be noted that through the above design, on the one hand, the full height and width range of the gap between the doors 500 can be covered, and the spatial blind area of single-cavity detection can be eliminated; on the other hand, the resonance frequency band enhancement in the full temperature range is realized by using the Helmholtz resonance cavity array 400, the influence of the environmental temperature can be eliminated, and the position of the foreign matter can be accurately positioned by comparing the signal amplitude change difference of different cavities; in addition, with the superposition of the resonance enhancement effect of each cavity, the weak sound signal change caused by the foreign matter is also amplified, and the detection ability of the system for small foreign matters is significantly improved, providing clearer feature input for the signal conversion of the piezoelectric sensor 413 and the analysis of the controller.

[0050] Embodiment 4 Based on the technical solutions provided in any one of embodiments 1 to 3, the present embodiment provides a platform door gap detection method based on acoustic synergy. The method is applied to the platform door gap detection system based on acoustic synergy provided in any one of embodiments 1 to 3, as shown in Figure 4 The method includes the following steps: Step one, emit a pulse ultrasonic wave of a preset frequency to scan the door area in the platform door gap 100, and construct a detection sound field; Step two, receive the reflected sound wave signal in the detection sound field, and convert the reflected sound wave signal into an electric signal; It should be noted that since the resonance frequency band of the Helmholtz resonance cavity array 400 covers the pulse ultrasonic wave drift range caused by the temperature, when there is no foreign matter in the platform door gap 100, the Helmholtz resonance cavity 410 receives a reflected sound wave signal of a fixed frequency and amplitude, i.e., the ultrasonic wave reflected back by the door 500, and produces resonance absorption on the reflected sound wave signal; when there is a foreign matter in the platform door gap 100, the foreign matter will change the propagation characteristics of the pulse ultrasonic wave, so that the amplitude of the reflected sound wave signal reaching the Helmholtz resonance cavity 410 changes, and the resonance enhancement characteristics of the Helmholtz resonance cavity 410 will significantly amplify the amplitude change.

[0051] Step three, compare the amplitude change of the electric signal with a reference value to determine whether there is a foreign matter in the detection sound field; In this embodiment, the amplitude of the received reflected sound wave signal without foreign matter is taken as the reference value, the change of the amplitude of the real-time received reflected sound wave signal is compared with the reference value, when the amplitude change of the reflected sound wave signal in a certain area exceeds the set threshold value, it can be judged that there is foreign matter in the platform door gap 100; wherein the set threshold value can be adjusted according to the type of foreign matter and the detection accuracy requirement, so as to realize the judgment of the existence of foreign matter and determine the type of foreign matter. Regarding the setting of the reference value, in some embodiments, a plurality of groups of pulse ultrasonic waves can be continuously transmitted, the amplitude of each group of reflected sound wave signal is recorded, the average value is taken after removing the maximum value and the minimum value, which is taken as the initial reference; further, the reference value calibration is automatically triggered every certain period of time, the average value of the amplitude of the current reflected sound wave without foreign matter is compared with the initial reference value, if the difference between the two is too large, the initial reference value is updated by using the average value of the amplitude of the current reflected sound wave, so as to ensure that the reference value always matches the actual state of the platform door gap 100.

[0052] Step four, when it is determined that there is foreign matter, an alarm signal is sent to the platform door or vehicle door control system to trigger the interlocking protection mechanism to avoid the vehicle door 500 or the platform door 600 from clamping foreign matter.

[0053] In this embodiment, the amplitude of the received reflected sound wave signal without foreign matter is taken as the reference value, the change of the amplitude of the real-time received reflected sound wave signal is compared with the reference value, when the amplitude change of the reflected sound wave signal in a certain area exceeds the set threshold value, it can be judged that there is foreign matter in the platform door gap 100; wherein the set threshold value can be adjusted according to the type of foreign matter and the detection accuracy requirement, so as to realize the judgment of the existence of foreign matter and determine the type of foreign matter. Regarding the setting of the reference value, in some embodiments, a plurality of groups of pulse ultrasonic waves can be continuously transmitted, the amplitude of each group of reflected sound wave signal is recorded, the average value is taken after removing the maximum value and the minimum value, which is taken as the initial reference; further, the reference value calibration is automatically triggered every certain period of time, the average value of the amplitude of the current reflected sound wave without foreign matter is compared with the initial reference value, if the difference between the two is too large, the initial reference value is updated by using the average value of the amplitude of the current reflected sound wave, so as to ensure that the reference value always matches the actual state of the platform door gap 100.

[0054] It should be noted that the physical properties of different foreign objects, such as material, density, surface roughness, etc., will cause the amplitude of the reflected acoustic wave signal to change regularly. In some embodiments, the acoustic impedance of metal clothes is quite different from that of air, the ultrasonic reflectivity is high, the amplitude of the reflected acoustic wave is small, and the amplitude change is small. Fabric / soft foreign objects, such as clothes, plastic bags, etc., have strong ultrasonic absorption, the amplitude of the reflected acoustic wave is significantly attenuated, and the amplitude change is large. Human tissues, such as fingers, limbs, etc., have strong ultrasonic penetration, the amplitude of the reflected acoustic wave is moderately attenuated, and the amplitude change is moderate. The reflection characteristics of hard non-metals, such as plastic bottles, cards, etc., are between those of metals and fabrics, and the amplitude change is also between those of metals and fabrics. Thus, the present embodiment sets multiple threshold values, each corresponding to a different foreign object type, thereby enabling the identification of the type of foreign object while determining the presence of the foreign object.

[0055] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art without departing from the spirit and principles of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

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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