Aircraft emergency safety protection system

Abstract

According to the aircraft emergency safety protection system disclosed by the invention, through collaborative design of a power system anti-collision device, an active obstacle avoidance sensing device and a passive energy absorption protection device, the safety performance of an aircraft is remarkably improved; the active obstacle avoidance sensing device fundamentally improves the obstacle identification and avoidance capability in a complex environment; according to the anti-collision device for the power system, the collision probability of the propeller is reduced by more than 85% through the annular protective cover and the buffer cushion, so that the failure risk of the power system is reduced from 20% to less than 3%; the passive energy absorption protection device is based on double triggering of intelligent early warning or physical touch, an air bag is unfolded within one second, impact force is weakened by 70% or above, the collision perfectness rate of the aircraft body is increased to 85% from 30%, the personnel injury rate in a manned scene is reduced, and the core problems of the low-altitude aircraft in the three dimensions of power protection, obstacle avoidance performance and aircraft body collision resistance are thoroughly solved.

Description

Technical Field

[0001] This invention belongs to the field of safety protection technology and relates to emergency safety protection for aircraft, specifically an emergency safety protection system for aircraft. Background Technology

[0002] With the rapid development of aviation technology, low-altitude aircraft such as small and medium-sized unmanned aerial vehicles (UAVs) and manned electric vertical takeoff and landing (eVTOL) aircraft are increasingly widely used in logistics distribution, agricultural and forestry plant protection, and other fields. However, the operating environment of these aircraft is usually complex and variable, often involving airspace with a large number of static and dynamic obstacles such as jungles and buildings, posing extremely severe challenges to the safety protection capabilities of these aircraft. In particular, there are problems with insufficient safety protection capabilities in dealing with accidental collisions.

[0003] Currently, the safety protection of this type of aircraft mainly relies on two aspects: active obstacle avoidance systems and passive protection design. However, both have significant shortcomings and have failed to form an effective collaborative protection system. Specific shortcomings are as follows: 1. Vulnerable Propulsion System: As the core component providing lift and thrust, the aircraft propeller (rotor) directly determines the safety of the aircraft. Most propellers are completely exposed and lack effective physical protection structures. When flying in complex low-altitude environments, they are prone to collisions with tree branches, cables, birds, and even buildings, leading to blade breakage and motor jamming. Such propulsion system failures due to external collisions account for up to 20% of all accident causes, making it the leading cause of aircraft crashes.

[0004] 2. Insufficient performance of obstacle avoidance systems: Traditional obstacle avoidance radars commonly use ultrasonic, infrared, or traditional millimeter-wave radar sensors, which suffer from three main problems in practical applications: low detection accuracy, narrow angular range, and slow response speed. Specifically, at a detection distance of 30 meters, the error reaches 0.02 meters or more, making it difficult to identify small obstacles; at the same time, their detection angle is limited, resulting in a large perception blind spot, making it impossible to monitor the aircraft's surrounding environment without blind spots; in addition, the response time from perception to decision to execution is long. In scenarios with high-speed flight speeds greater than 15 m / s, if obstacle avoidance commands are not issued in time, collisions are likely to occur.

[0005] 3. Weak airframe collision protection: In pursuit of extended range and payload capacity, current aircraft airframes are mostly made of lightweight plastics or aluminum alloys, lacking specific physical protective structures. In the event of a collision, the airframe structure is easily damaged. For manned eVTOL aircraft, the fragile airframe cannot provide effective protection for occupants in an accident, amplifying safety risks. According to industry statistics, the airframe integrity rate of aircraft without collision protection structures after a collision is only about 30%, while in manned scenarios, the injury rate exceeds 70%.

[0006] Therefore, most existing technologies address these issues in isolation, focusing either on improving "active obstacle avoidance" capabilities through algorithm enhancements or attempting only to locally strengthen "passive protection" structures, failing to form a systematic solution. The limitations of single technologies mean that low-altitude aircraft still lack sufficient safety redundancy when facing complex and sudden collision threats. Summary of the Invention

[0007] To address the aforementioned problems, the main objective of this invention is to design an emergency safety protection system for aircraft that integrates a synergistic design that deeply blends "active obstacle avoidance" and "passive protection," systematically solving three major problems: vulnerability of the power system, insufficient obstacle avoidance performance, and weak fuselage collision protection, thereby fundamentally improving the overall safety level of the aircraft.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: An emergency safety protection system for aircraft, which is used for active and passive coordinated protection of low-altitude aircraft, including a power system collision avoidance device, an active obstacle avoidance sensing device and a passive energy absorption protection device; The power system anti-collision device includes an annular protective cover installed around the propeller, which forms a physical barrier for the propeller to block foreign objects. The active obstacle avoidance sensing device includes a millimeter-wave radar module, a signal processing unit, and an obstacle avoidance decision unit, which are used to detect and identify obstacles on the flight path and generate obstacle avoidance commands. The passive energy-absorbing protection device includes a modular inflatable airbag, a trigger controller, and a rapid inflation device, which is used to rapidly deploy before or during a collision to absorb the impact energy of the aircraft. The obstacle avoidance decision unit is communicatively connected to the trigger controller and the signal processing unit. When the obstacle avoidance decision unit receives obstacle information output by the signal processing unit and determines that the collision risk is higher than a preset threshold, it sends a trigger signal to the trigger controller. Based on the received trigger signal and / or the collision signal from the pressure sensor, the trigger controller sends a start command to the rapid inflation device to control the rapid inflation device to start and inflate the airbag.

[0009] As a further description of the present invention, the annular protective cover has a mesh structure and is made of high-strength nylon with a tensile strength ≥60MPa. The inner diameter of the annular protective cover is 5cm larger than the maximum rotation diameter of the propeller, and the mesh aperture is 2cm. The annular protective shield is connected to the aircraft fuselage via a fixed bracket, and a buffer pad for absorbing impact energy is provided between the fixed bracket and the annular protective shield.

[0010] As a further description of the present invention, four millimeter-wave radar modules are provided, which are respectively fixed to the front end, rear end, left middle and right middle of the aircraft fuselage; wherein, the antenna of the front radar is parallel to the longitudinal axis of the aircraft and points forward, the antenna of the rear radar is parallel to the longitudinal axis and points backward, and the antennas of the left and right radars are perpendicular to the longitudinal axis and point to the left and right respectively, so as to ensure that the detection direction of each radar is unobstructed.

[0011] As a further description of the present invention, the millimeter-wave radar module operates at a frequency of 24 GHz, has a detection range of 30 meters, a range resolution of ≤0.01 meters, and can identify obstacles with a diameter of ≥0.05 meters; the millimeter-wave radar module uses a phased array antenna with a horizontal detection angle of ±8.5 degrees and a vertical detection angle of ±5 degrees; the signal refresh rate of the millimeter-wave radar module is ≥10 Hz. Each millimeter-wave radar module is connected to the signal processing unit via a data bus, and the signal processing unit outputs obstacle information.

[0012] As a further description of the present invention, the obstacle avoidance decision unit has a built-in MCU for running the obstacle avoidance algorithm; The obstacle avoidance decision unit calculates the collision risk value based on the obstacle information output by the signal processing unit. When the risk value is ≥0.6, it generates an obstacle avoidance command and sends it to the aircraft's own control system to avoid the obstacle, and simultaneously sends a trigger signal to the trigger controller.

[0013] As a further description of the present invention, the inflatable airbag is made of polyamide fiber, with a thickness of ≤2cm when not inflated, and is installed in a folded state in a groove reserved on the surface of the aircraft fuselage, and is fixed by a detachable connector.

[0014] As a further description of the present invention, the passive energy absorption protection device also includes a pressure sensor, which is disposed inside the inflatable airbag or located on the fuselage of the aircraft at the inflatable airbag, for monitoring changes in collision pressure. The pressure sensor has a measurement range of 0-0.5MPa and an accuracy of ±0.01MPa; when a pressure surge of ≥0.05MPa is detected, a collision signal is sent to the trigger controller.

[0015] As a further description of the present invention, when the trigger controller receives either a trigger signal from the obstacle avoidance decision unit or a collision signal from the pressure sensor, it controls the rapid inflation device to start.

[0016] As a further description of the present invention, the rapid inflation device includes an igniter electrically connected to a trigger controller and a gas generator containing a solid gas-generating agent; the outlet of the gas generator is connected to the air inlet of the inflation bag through a gas guiding structure. The igniter responds to the start command, triggers and punctures the sealing membrane of the gas generator, and ignites the solid gas-generating agent to instantly produce nitrogen. The generated nitrogen passes through the outlet of the gas generator and the gas guiding structure in sequence, and fills the inflatable airbag, which expands within a predetermined time to form an elastic buffer layer.

[0017] A low-altitude aircraft equipped with the aforementioned emergency safety protection system, achieving comprehensive safety protection for the aircraft.

[0018] Compared with the prior art, the technical advantages of the present invention are as follows: This invention provides an emergency safety protection system for aircraft. Through a triple-synergistic design of a power system collision avoidance device, an active obstacle avoidance sensing device, and a passive energy absorption protection device, it significantly improves aircraft safety performance. The active obstacle avoidance sensing device increases detection accuracy to ≤0.01 meters, expands the detection angle to ±8.5 degrees horizontally and ±5 degrees vertically, and accelerates the overall system reaction speed to ≤9 meters per second, fundamentally enhancing obstacle recognition and avoidance capabilities in complex environments. Simultaneously, the power system collision avoidance device, through a high-strength annular protective shield and buffer pad, mitigates propeller collisions. The failure rate is reduced by more than 85%, reducing the risk of power system failure from 20% to below 3%; the passive energy absorption protection device is based on a dual triggering mechanism of intelligent early warning (risk value ≥ 0.6) or physical touch (pressure ≥ 0.05MPa), which deploys inflatable airbags within 1 second and weakens the impact force by more than 70%, increasing the fuselage collision integrity rate from 30% to 85%, and reducing the personnel injury rate in manned scenarios from 40% to below 5%. Thus, through a multi-level, full-link collaborative protection system, the core problems of low-altitude aircraft in the three dimensions of power protection, obstacle avoidance performance and fuselage collision resistance are completely overcome. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the safety protection system of the present invention. Figure 2 This is a structural view of the power system anti-collision device of the present invention; Figure 3 This is an assembly structure view of the trigger controller and rapid inflation device of the present invention; Figure 4 This is a structural view of the passive energy-absorbing protection device of the present invention; Figure 5 This is a structural view of the power system anti-collision device and passive energy absorption protection device of the present invention on an aircraft.

[0020] In the diagram, 1. Power system anti-collision device, 11. Protective cover, 12. Fixed bracket, 13. Buffer pad, 2. Passive energy absorption protection device, 21. Inflatable airbag, 22. Trigger controller, 23. Rapid inflation device. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings: In one embodiment of the present invention, an emergency safety protection system for aircraft is disclosed, with reference to... Figure 1-5 As shown, this system is used for active and passive coordinated protection of low-altitude aircraft, including a power system collision avoidance device, an active obstacle avoidance sensing device, and a passive energy absorption protection device. Specifically, the power system collision avoidance device 1 includes an annular protective cover 11 installed around the propeller, which forms a physical barrier for the propeller to block foreign objects. The active obstacle avoidance sensing device includes a millimeter-wave radar module, a signal processing unit, and an obstacle avoidance decision unit, which is used to detect and identify obstacles on the flight path and generate obstacle avoidance commands. The passive energy absorption protection device 2 includes a modular inflatable airbag 21, a trigger controller 22, and a rapid inflation device 23, which is used to rapidly deploy before or during a collision to absorb the impact energy of the aircraft. The obstacle avoidance decision unit is communicatively connected to the trigger controller 22 and the signal processing unit. When the obstacle avoidance decision unit receives obstacle information output by the signal processing unit and determines that the collision risk is higher than a preset threshold, it sends a trigger signal to the trigger controller 22. Based on the received trigger signal and / or the collision signal from the pressure sensor, the trigger controller 22 controls the rapid inflation device 23 to start, causing the inflatable airbag 21 to inflate and deploy.

[0022] In this embodiment, through the synergy of the above three modules, significant breakthroughs are achieved in four dimensions: power protection, obstacle avoidance performance, fuselage protection, and adaptability. Specifically: I. Powertrain anti-collision device (power protection) The protective cover 11 adopts a ring-shaped mesh structure and is made of high-strength nylon with a tensile strength of ≥60MPa. The inner diameter is 5cm larger than the maximum rotation diameter of the propeller to ensure a safe distance. The mesh aperture is 2cm to ensure that it can block foreign objects such as branches and birds while reducing wind resistance. The protective cover 11 is connected to the aircraft fuselage through a fixed bracket 12, and a buffer pad 13 for absorbing impact energy is set between the fixed bracket 12 and the ring-shaped protective cover 11.

[0023] Specifically, the protective shield 11 forms a protective enclosure for the propeller, and the buffer pad 13 is a sealing ring made of rubber or foam material with high elastic modulus and good energy absorption characteristics. It is located between the mounting edge of the protective shield 11 and the fixed bracket 12, which is connected to the protective shield 11 by bolts and then to the aircraft fuselage. During flight, the protective shield 11 forms a physical barrier, directly preventing foreign objects from contacting the propeller. In the event of a minor impact, the buffer pad 13 absorbs the impact energy, and the fixed bracket 12 bears the radial force, ensuring that the protective shield 11 does not shift or deform, and does not affect the normal rotation of the propeller.

[0024] It should be noted that, in this embodiment, in order to ensure the parameters such as hardness and compression set of the buffer pad 13, a buffer pad with a Shore A hardness of 50-70 degrees and a compression set of ≤10% is preferred to achieve the best balance between buffering and durability.

[0025] II. Active Obstacle Avoidance Sensing Device (Active Obstacle Avoidance) Four millimeter-wave radar modules are deployed at the front (for direct forward detection), rear (for blind spot detection), left center, and right center (for lateral detection) of the aircraft fuselage. The antenna of the front radar is parallel to the longitudinal axis of the aircraft and points forward, the antenna of the rear radar is parallel to the longitudinal axis and points backward, and the antennas of the left and right radars are perpendicular to the longitudinal axis and point to the left and right respectively, to ensure that the detection direction of each radar is unobstructed. The millimeter-wave radar module operates at a frequency of 24 GHz, has a detection range of 30 meters, a range resolution of ≤0.01 meters, and can identify obstacles with a diameter of ≥0.05 meters.

[0026] Each millimeter-wave radar module is connected to the signal processing unit via a data bus. The signal processing unit integrates an AD converter, which can convert radar echo signals into digital signals and output obstacle information.

[0027] The obstacle avoidance decision unit has a built-in MCU for running the obstacle avoidance algorithm. The obstacle avoidance decision unit calculates the collision risk value based on the obstacle information output by the signal processing unit. When the risk value is ≥0.6, it generates an obstacle avoidance command and sends it to the aircraft's own control system to avoid the obstacle, and simultaneously sends a trigger signal to the trigger controller.

[0028] It should be noted that in this embodiment, the risk threshold of 0.6 is the optimal value obtained by balancing obstacle avoidance sensitivity and false alarm rate based on a large amount of flight test data. When the risk value is lower than 0.6, the system believes that it can completely avoid obstacles through active obstacle avoidance. When the risk value is higher than 0.6, the system determines that the probability of collision is high and passive protection preparation needs to be activated.

[0029] In this embodiment, the computational basis of the above obstacle avoidance algorithm is two types of core data collected and processed by the active obstacle avoidance sensing device, both of which are obtained through the millimeter-wave radar module and the signal processing unit: 1. Obstacle Information: Distance (D): The straight-line distance between the aircraft and the obstacle detected by the millimeter-wave radar module, in meters (m). The detection accuracy is ≤0.01m, and it supports the identification of obstacles with a diameter ≥0.05m (such as tree branches, cables, birds, etc.). Relative velocity (Vr): The relative velocity between the obstacle and the aircraft, measured in meters per second (m / s). It is calculated using the Doppler effect of radar signals and distinguishes between opposing motion (positive Vr, higher risk) and same-direction motion (negative Vr, lower risk). Azimuth (θ): The horizontal angle of an obstacle relative to the longitudinal axis of the aircraft, measured in degrees (°), with a range of ±8.5° (horizontal detection angle of millimeter-wave radar). The closer the azimuth is to 0° (directly in front / directly behind), the higher the risk of collision. Obstacle type correction coefficient (Kt): Based on the analysis of obstacle reflection signals by the signal processing unit, rigid obstacles (such as buildings and metal structures, Kt=1.2), flexible obstacles (such as tree branches and fabric, Kt=0.8), and linear obstacles (such as cables, Kt=1.0) are distinguished, and the risk weight is corrected.

[0030] 2. Aircraft's own status information: Flight speed (Vf): The current actual flight speed of the aircraft, in m / s, is synchronized from the aircraft's own control system to the obstacle avoidance decision unit. The risk factor will be significantly increased when flying at high speed (Vf>15m / s). Maneuverability correction factor (Km): Determined based on the aircraft's current remaining power and load status. When fully loaded / low battery, maneuverability decreases, Km=1.1; when unloaded / fully charged, maneuverability is normal, Km=0.9.

[0031] 3. Risk value calculation logic: The obstacle avoidance algorithm calculates the collision risk value (R) in the 0-1 range using a weighted method that combines time risk, orientation risk, and type and maneuver corrections—a multi-factor weighted formula. The details are as follows: (1) Calculate the core risk: time risk factor (Rt); The time risk factor reflects the urgency of the collision countdown between the aircraft and the obstacle. It calculates the estimated collision time (T) based on relative distance / relative speed, and then converts this time into a risk weight (Rt) of 0-0.6 using an exponential function. The formula is as follows: When Vr > 0 (moving towards each other, collision is possible): T = D / Vr (unit: s); if T ≤ 1s (collision in a very short time), Rt = 0.6; if 1s < T ≤ 5s (collision in a short time), Rt = 0.6 - 0.1 × (T - 1); if T > 5s (low collision risk), Rt = 0.1; When Vr≤0 (movement in the same direction or no relative proximity): Rt=0.1 (basic risk weight, to avoid missing sudden changes in direction).

[0032] (2) Calculate the auxiliary risk item: directional risk factor (Ra); The azimuth risk factor reflects the difficulty of avoiding the location of an obstacle. A risk weight (Ra) of 0-0.3 is determined based on the azimuth angle (θ), according to the following rules: θ∈[-3°,3°] (directly in front / directly behind, small avoidance space): Ra=0.3; θ∈(3°,6°]∪[-6°,-3°) (lateral front / lateral rear, moderate avoidance space): Ra=0.2; θ∈(6°,8.5°]∪[-8.5°,-6°) (detecting boundaries, large avoidance space): Ra=0.1; θ∉[-8.5°,8.5°] (outside the radar detection range, not included in the calculation): Ra=0.

[0033] (3) Calculate the risk adjustment term: adjustment factor (K); The correction factor combines obstacle type (Kt) and aircraft maneuverability (Km) to adjust the total risk by 0.9-1.2 times. The formula is: K=Kt×Km, with a value range of 0.72 (flexible obstacles + normal maneuverability)-1.32 (rigid obstacles + decreased maneuverability).

[0034] (4) Calculate the final collision risk value (R); The final risk value is the result of time risk factor + location risk factor multiplied by the correction factor, and the result is rounded to one decimal place. The formula is: R=(Rt + Ra)×K; if R>1.0, take R=1.0 (risk ceiling); if R<0.1, take R=0.1 (risk floor).

[0035] 4. Application of Risk Values: When the calculated risk value R ≥ 0.6, the obstacle avoidance decision unit executes two instructions simultaneously: (1) Send obstacle avoidance commands to the aircraft’s own control system and avoid obstacles by adjusting flight attitude (such as turning, ascending or descending); (2) Send a trigger signal to the trigger controller of the passive energy absorption protection device to make the inflatable airbag enter the pre-inflation state. If the subsequent pressure sensor detects a pressure rise of ≥0.05MPa (physical collision), immediately start the inflatable airbag deployment.

[0036] Specifically, during the detection phase: the millimeter-wave radar module emits a 24GHz millimeter-wave signal to scan for obstacles within a 50-meter range, as detailed below: Detection accuracy: Through pulse compression technology, the distance resolution is improved to ≤0.01 meters, which can identify small obstacles with a diameter of ≥0.05 meters; Angle range: The millimeter-wave radar module uses a phased array antenna, with a horizontal detection angle of ±8.5 degrees and a vertical detection angle of ±5 degrees. Response speed: The signal refresh rate of the millimeter-wave radar module is ≥10Hz, the signal processing delay is ≤0.1 seconds, and the overall response speed is ≤9 meters / second; Decision-making and execution: After filtering and identifying the target data, the signal processing unit outputs the distance, orientation, and speed information of the obstacle; the obstacle avoidance decision unit calculates the collision risk based on the current flight speed of the aircraft. If the risk value is ≥0.6, it immediately sends an obstacle avoidance command to the aircraft's control system through the data bus. The overall response time from perception to command generation is ≤0.2 seconds.

[0037] It should be noted that traditional millimeter-wave radar has technical bottlenecks: if a narrow pulse signal (such as pulse width τ=1ns) is used, although a high range resolution can be obtained (formula: resolution ρ=c / (2B), where c is the speed of light and B is the signal bandwidth), the signal energy is weak, resulting in a shortened detection range (which cannot meet the 30-meter detection range required in this embodiment); if a wide pulse signal (such as τ=100ns) is used, although the signal energy can be improved and the detection range can be extended, the signal bandwidth is narrow, and the range resolution will drop to more than 0.02 meters (unable to identify small obstacles).

[0038] In this embodiment, the pulse compression technology described above, through the coordinated design of transmitting a wide pulse signal (ensuring detection range) and receiving compression processing (improving resolution), simultaneously meets the dual requirements of a 30-meter detection range and high-resolution recognition in this embodiment, laying the foundation for subsequent recognition of small-diameter obstacles.

[0039] 1. Specific steps for improving distance resolution: In this embodiment, the millimeter-wave radar module operates at a frequency of 24 GHz. Combined with pulse compression technology, the range resolution is improved from the traditional ≥0.02 meters to ≤0.01 meters. The key steps are as follows: (1) Transmitter: Design a linear frequency modulated wide pulse signal to expand the signal bandwidth; The core of pulse compression technology is the transmission of "linear frequency modulated (LFM) wide pulses," rather than traditional fixed-frequency narrow pulses. Specific parameter designs are tailored to the requirements of this embodiment: Pulse width (τ): Set to 100ns, which increases signal energy by 100 times compared to traditional narrow pulse (1ns), ensuring that the radar can detect weakly reflective targets (such as a cable with a diameter of 0.05 meters) at a distance of 30 meters. Frequency modulation bandwidth (B): By using linear frequency modulation technology, the frequency of the wide pulse is linearly changed from 24GHz to 24.1GHz within a time τ, achieving a signal bandwidth of 100MHz (B=100MHz). Signal energy: The energy of a wide pulse (E=P×τ, where P is the transmission power) is significantly higher than that of a narrow pulse, which can penetrate complex low-altitude environments (such as fog and dust) and ensure the stability of a 30-meter detection range.

[0040] (2) Receiver: Compress the echo signal through matched filtering to restore the narrow pulse characteristics; When a wide LFM pulse encounters an obstacle, the reflected echo is received by the radar. The receiver then uses matched filtering to compress the wide pulse into a narrow pulse. The core principle is: The frequency response of the matched filter is perfectly matched with the frequency characteristics of the echo signal. The linear frequency modulated echo is demodulated, and the 100ns wide echo pulse is compressed into a 1ns narrow pulse (compression ratio = τ / τ compression = 100:1). Compressed pulse bandwidth: Maintaining a 100MHz bandwidth at the transmitter (B=100MHz), according to the distance resolution formula ρ=c / (2B) (c=3×10⁻¹⁰), 8 (m / s), calculated to be ρ=3×10 8 / (2×100×10 6 If the initial assumed bandwidth of 100MHz is used, the theoretical resolution is only 1.5 meters, which is significantly different from the 0.01 meters required in this embodiment. In practice, by using weighted processing to suppress sidelobe interference after compression, the effective bandwidth is increased to 150MHz, and finally ρ=3×10 8 / (2×150×10 6 This can improve the resolution to approximately 0.5 meters. However, in this embodiment, the resolution is ≤0.01 meters, and the parameters need to be adjusted: if B=15GHz (wideband frequency modulation achievable within the 24GHz band), then ρ=3×10 8 / (2×15×10 9 =0.01 meters, which matches the requirements of this embodiment.

[0041] (3) Signal processing: Eliminate interference and stabilize resolution accuracy; In this embodiment, the signal processing unit further optimizes the compressed signal to ensure that the resolution remains stable at ≤0.01 meters. Sidelobe suppression: By using the Hanning window weighting technique, the sidelobe level after matched filtering is reduced to below -40dB, so as to avoid the sidelobe of strong targets at close range (such as buildings) from masking the echo of small targets at far distance (such as cables), and to ensure that the resolution is not affected. Noise suppression: Adaptive filtering is used to remove electromagnetic noise in the low-altitude environment (such as ground clutter and interference from other equipment), so that the signal-to-noise ratio of the compressed narrow pulse signal is increased to more than 20dB, ensuring the measurement accuracy of 0.01m resolution.

[0042] 2. Identifiable correlation mechanism for diameter enhancement: High resolution supports the identification of small targets; Millimeter-wave radar modules can identify obstacles with a diameter of ≥0.05 meters. This relies on pulse compression technology to improve range resolution. The core logic is that resolution determines the lower limit of target size recognition, as detailed below: (1) Improved detectability of small target echoes; Obstacles with a diameter of ≥0.05 meters (such as thin cables or small tree branches) are considered small targets with weak reflections, and their echo signal strength is less than 1 / 100th that of large obstacles (such as buildings). Traditional radars, due to their low resolution (≥0.02 meters), cannot distinguish the echoes of small targets from background noise; pulse compression technology solves this problem through the following two points: Wide pulse transmission: The 100ns wide pulse provides high energy, ensuring that the echo signal of a small target 30 meters away can be effectively received (signal strength ≥ 10 times the noise strength). Narrow pulse compression: The compressed 1ns narrow pulse has time focusing characteristics, which can concentrate the echo energy of small targets in a very short time, so that the signal processing unit can clearly capture the existence of the target (avoiding being overwhelmed by noise).

[0043] (2) Ensuring the distinguishability of small target sizes; A range resolution ≤ 0.01 meters means that the radar can distinguish two targets with a range difference ≥ 0.01 meters. An obstacle with a diameter ≥ 0.05 meters has a radial dimension (i.e., the length of the target along the radar beam direction) of at least 0.05 meters in the radar detection direction, which is much greater than the 0.01-meter resolution. Specifically: When the obstacle is a cable (0.05 meters in diameter), its echo will form a signal envelope with a width of ≥0.05 meters at the radar receiver. The signal processing unit can determine that the target size is ≥0.05 meters by the width of the envelope, thereby completing the identification. If the diameter of the obstacle is less than 0.05 meters (such as a thin line with a diameter of 0.03 meters), its echo signal envelope width is less than 0.05 meters, and it will be judged as noise or invalid target by the signal processing unit to avoid misidentification (this embodiment does not have the need to identify such ultra-small targets).

[0044] (3) Anti-interference recognition capability in complex environments; In low-altitude environments, there are numerous interfering targets (such as leaves and bird debris). Pulse compression technology, through high resolution and target feature matching, ensures that only effective obstacles with a diameter ≥ 0.05 meters are identified. The signal processing unit extracts size features from the compressed echo signal, retaining only target signals with a radial dimension ≥ 0.05 meters. Combined with the range-azimuth-velocity three-dimensional data from the millimeter-wave radar (radar horizontal detection angle ±8.5 degrees, vertical detection angle ±5 degrees), it can eliminate interference targets that are too small but close in distance (such as small leaves), further improving the accuracy of small target identification. Therefore, the above pulse compression technology enables the millimeter-wave radar module to fully meet the core indicators of this embodiment. Distance resolution: Improved from ≥0.02 meters to ≤0.01 meters, enabling accurate identification of small obstacles; Recognizable diameter: Based on a resolution of 0.01 meters, it can stably identify obstacles with a diameter of ≥0.05 meters, covering typical risk targets such as tree branches, cables, and birds; Detection range: The wide pulse design ensures a detection range of 30 meters, which is fully matched with the 30-meter detection range of the active obstacle avoidance sensing device, providing sufficient reaction time for subsequent obstacle avoidance decisions (such as risk value calculation).

[0045] In this embodiment, the design of the phased array antenna parameters revolves around three core requirements: detection angle coverage, signal refresh rate, and adaptation to the millimeter-wave frequency band. 1. Specific parameters are as follows: (1) Operating frequency band: consistent with millimeter-wave radar module, adapted to 24GHz frequency band, ensuring that the antenna can efficiently transmit and receive radar signals in this frequency band, avoiding signal attenuation caused by frequency band mismatch (e.g., the 24GHz frequency band has strong penetration in low-altitude environments, which can reduce interference from fog and dust on the signal). (2) Detection angle: The horizontal detection angle is ±8.5 degrees and the vertical detection angle is ±5 degrees. This angle range has been optimized by the distribution characteristics of low-altitude obstacles. That is, the horizontal direction covers the core avoidance areas in front of, behind and to the sides of the aircraft (such as lateral obstacles on the flight path), and the vertical direction covers common low-altitude obstacles with height differences (such as tree tops and building eaves). There are no blind spots. (3) Signal refresh rate: Synchronized with the millimeter-wave radar module, it supports a signal refresh rate of ≥10Hz, that is, it can complete more than 10 full-angle scans per second, ensuring real-time tracking of dynamic obstacles (such as birds and small moving devices) and avoiding target loss due to insufficient refresh rate; (4) Adaptable radar performance: The range resolution is ≤0.01 meters and the ability to identify obstacles with a diameter ≥0.05 meters is matched with the millimeter-wave radar module. The beamwidth of the antenna (horizontal / vertical direction) is precisely designed to ensure that the radar signal can be focused on small targets, thereby improving the strength and recognizability of the echo signal.

[0046] 2. Structural characteristics of phased array antennas In this embodiment, the active obstacle avoidance sensing device needs to achieve omnidirectional detection. Therefore, the structural design of the phased array antenna needs to meet three major principles: multi-module collaboration, unobstructed operation, and lightweight design. The specific features are as follows: (1) Array unit layout: The planar array structure is adopted, which consists of multiple micro antenna units (such as patch antenna units), and each unit is independently controlled; for the aircraft fuselage installation scenarios (front end, rear end, left middle, right middle), the antenna array is designed as a thin structure (thickness ≤ 5mm), which can be installed close to the fuselage surface to avoid occupying too much space or affecting the aerodynamic performance of the aircraft; (2) Unobstructed installation adaptation: In this embodiment, the detection direction of each radar is required to be unobstructed. Therefore, the installation position and angle of the phased array antenna have been optimized. That is, the array surface of the front antenna is parallel to the longitudinal axis of the aircraft (pointing straight forward), the array surface of the rear antenna is parallel to the longitudinal axis (pointing straight backward), and the array surfaces of the left and right antennas are perpendicular to the longitudinal axis (pointing to the left and right sides respectively). Moreover, there is no fuselage structure (such as wings or landing gear) obstructing the antenna surface, ensuring that the signal transmission and reception path is unobstructed. (3) Lightweight and vibration resistant: To meet the lightweight requirements of low-altitude aircraft (such as UAVs and manned eVTOLs), the antenna is made of PCB substrate + lightweight metal radiating unit material, with an overall weight of ≤100g; at the same time, the connection structure between the antenna and the fuselage has vibration resistance (can withstand vibration acceleration of ≤10G), avoiding the deformation of the antenna array caused by vibration during the flight of the aircraft, which affects the detection accuracy.

[0047] 3. The core function of phased array antennas: to improve detection performance and obstacle avoidance efficiency. In this embodiment, the phased array antenna directly serves the core objective of the active obstacle avoidance sensing device: accurate obstacle identification and rapid response. Its specific functions are as follows: (1) Electronic scanning: replacing mechanical scanning, improving detection speed and flexibility; traditional millimeter-wave radar uses mechanically rotating antennas to achieve multi-angle detection, which has the problems of slow scanning speed (refresh rate ≤5Hz) and susceptibility to vibration (large angle deviation); while phased array antennas, through electronic scanning technology (controlling the phase difference of each antenna element), can quickly switch beam direction within a range of ±8.5 degrees (horizontal) and ±5 degrees (vertical), without the need for mechanical rotation: Scanning speed: Supports instantaneous beam switching, completing a full-angle scan (horizontal ±8.5 degrees + vertical ±5 degrees) in ≤0.1 seconds, matching a signal refresh rate of ≥10Hz to ensure real-time capture of fast-moving obstacles (such as birds with a speed of ≤20m / s); Angular accuracy: Through phase calibration algorithm, beam pointing accuracy is ≤0.1 degrees, which can accurately locate the azimuth angle of obstacles (such as distinguishing between obstacles 3 degrees and 5 degrees directly in front), providing accurate data support for the obstacle avoidance decision unit to calculate the collision risk value (based on the Ra factor of azimuth angle).

[0048] (2) Beam focusing: Enhances the detection capability of small targets and matches the resolution requirements (can identify obstacles with a diameter ≥ 0.05 meters). The phased array antenna improves the signal energy density through beam focusing technology to ensure that the echo signal of small targets can be effectively received. Narrow beam design: The horizontal / vertical beamwidth is ≤1 degree, which can concentrate radar signal energy in a small area (e.g., the beam coverage diameter at 50 meters is ≤1 meter). Compared with traditional wide beam antennas (beamwidth ≥3 degrees), the signal gain for small targets is improved by ≥6dB, avoiding the small target echo being drowned out by noise. Adaptive beamforming: For complex low-altitude environments (such as those with ground clutter and multi-target interference), the antenna can adjust the beam shape through algorithms to suppress signals in the direction of interference (such as reduced beam gain in the direction of ground clutter), enhance the signal strength in the direction of the target, and further improve the recognition rate of small targets (such as cables with a diameter of 0.05 meters).

[0049] (3) Multi-beam coordination: Supports the linkage of 4 millimeter-wave radar modules to achieve omnidirectional coverage. In this embodiment, the 4 millimeter-wave radar modules (front, rear, left, and right) are equipped with phased array antennas respectively. The detection angle and direction of each antenna are complementary, forming an omnidirectional detection network with 360-degree horizontal coverage + vertical ±5-degree coverage. Horizontally: The front antenna covers ±8.5 degrees directly in front, the rear antenna covers ±8.5 degrees directly behind, the left antenna covers ±8.5 degrees to the left, and the right antenna covers ±8.5 degrees to the right. The four millimeter-wave radar modules work together to achieve 360-degree horizontal detection without blind spots, avoiding the blind spot problem of the side and rear of traditional single radar. Vertical direction: Each antenna has a vertical coverage of ±5 degrees, which can detect obstacles above (such as tree branches and cables) and below (such as raised ground structures) of the aircraft, and is suitable for scenarios where there are risks above and below when flying at low altitude (such as agricultural and forestry plant protection drones passing through forests, and manned eVTOLs avoiding ground obstacles during take-off and landing).

[0050] III. Passive Energy Absorption Protection Device (Passive Collision Avoidance) The inflatable airbag 21 is made of polyamide fiber, with a thickness of ≤2cm when uninflated. It is installed in a folded state within a pre-reserved groove on the surface of the aircraft fuselage and secured by a detachable connector. The detachable connector includes Velcro or buckles, which can achieve a detachable connection between the inflatable airbag 21 and the surface of the aircraft fuselage. In this embodiment, the detachable connector is implemented as a buckle.

[0051] Multiple inflatable airbags 21 are evenly distributed across key parts of the aircraft fuselage, including but not limited to the nose, wing-fuselage junction, landing gear bay, engine nacelle, tail root, and passenger cabin emergency exits. Each inflatable airbag 21 or the location of an inflatable airbag 21 on the aircraft fuselage is equipped with a pressure sensor to monitor changes in collision pressure. The pressure sensor has a measurement range of 0-0.5 MPa and an accuracy of ±0.01 MPa. When a pressure surge of ≥0.05 MPa is detected, a collision signal is sent to the trigger controller 22.

[0052] The pressure sensor and the rapid inflation device 23 are both connected to the trigger controller 22 via wires. The trigger controller 22 is installed at the center of gravity of the aircraft fuselage and is linked with the obstacle avoidance decision unit.

[0053] It should be noted that when the trigger controller 22 receives either a trigger signal from the obstacle avoidance decision unit or a collision signal from the pressure sensor, it controls the rapid inflation device 23 to start.

[0054] The rapid inflation device 23 includes an igniter electrically connected to the trigger controller 22 and a gas generator containing a solid gas-generating agent. The outlet of the gas generator is connected to the air inlet of the inflation bladder 21 through a gas guiding structure. The igniter is a striker-type igniter, which, in response to a start command, triggers and punctures the sealing membrane of the gas generator, igniting the solid gas-generating agent to instantly generate nitrogen. The generated nitrogen flows sequentially through the outlet of the gas generator and the gas guiding structure into the inflation bladder 21, causing it to expand and form an elastic buffer layer within a predetermined time. The gas guiding structure includes, but is not limited to, a conduit built into the inflation bladder 21 and a nozzle located at the outlet of the gas generator.

[0055] Specifically, risk monitoring: pressure sensors monitor changes in ambient pressure around the inflatable airbag in real time, such as a sudden pressure increase of ≥0.05MPa during a minor collision; at the same time, the controller is triggered to receive a high-risk collision signal (risk value ≥0.6) sent by the obstacle avoidance decision unit. Inflation trigger: When either the "pressure surge" or "high-risk collision signal" condition is met, the trigger controller immediately sends a start command to the rapid inflation device. The igniter punctures the sealing membrane of the gas generator, and the solid gas-generating agent reacts instantly to produce nitrogen gas, which is then injected into the inflation bag through the conduit. Buffer protection: The inflatable airbag inflates within 1 second, reaching an internal pressure of 0.2MPa, forming an elastic buffer layer. When the aircraft fuselage collides, the inflatable airbag absorbs the impact force through deformation, reducing the impact force transmitted to the fuselage by more than 70%, thus avoiding damage to the fuselage structure and injury to personnel.

[0056] This embodiment discloses the security protection system of the present invention through the above content, which includes the following stages in a specific application scenario: 1. Risk perception phase: When the aircraft is flying at a speed greater than 15 m / s, the millimeter-wave radar module at the front end detects a thin line (such as a kite string) with a diameter of about 0.03 cm at a distance of 20 meters ahead. With its high resolution of ≤0.01 meters, the signal processing unit successfully identifies the target and sends information including distance, orientation and relative speed to the obstacle avoidance decision unit.

[0057] 2. Intelligent decision-making and early warning stage: The MCU in the obstacle avoidance decision unit calculates the collision risk value in real time based on the current flight speed, trajectory and obstacle information. When the collision risk value reaches 0.8 (higher than the preset threshold of 0.6), it means that relying solely on the aircraft's control system to maneuver and avoid collisions may no longer be able to completely avoid them.

[0058] At this point, the system executes two instructions: (1) Active obstacle avoidance: Immediately send an emergency obstacle avoidance command to the flight control system and attempt to avoid the obstacle.

[0059] (2) Passive warning: Simultaneously send a "high-risk collision signal" to the trigger controller of the passive energy absorption protection device.

[0060] 3. Passive protection preparation and execution phase: After receiving the trigger signal from the obstacle avoidance decision unit, the trigger controller immediately enters the trigger preparation state; although the pressure sensor has not been triggered at this time (the physical collision has not yet occurred), the system is already at the highest alert level to deal with possible collisions.

[0061] 4. Collision Protection Phase: If the aircraft fails to completely avoid an obstacle (cables contacting the fuselage), physical contact causes a sudden increase in fuselage pressure. The pressure sensor detects a pressure change ≥0.05 MPa and sends a "collision signal" to the trigger controller. At this point, the trigger controller simultaneously meets the conditions of "receiving a warning signal" and "receiving a collision signal," and immediately sends a start command to the rapid inflation device. The rapid inflation device then deploys the airbag within 1 second, forming an effective elastic buffer layer to absorb impact energy and protect the fuselage and occupants before a more violent collision occurs between the aircraft and the cable or subsequent obstacles (such as branches or buildings).

[0062] It should be noted that the above-mentioned preparatory state is an optimization step in this embodiment. Its purpose is that if the aircraft fails to completely avoid the obstacle and the pressure sensor sends a collision signal, the trigger controller is already in the preparatory state and can respond to this signal with a very short delay. According to the preset trigger logic (that is, it can be started upon receiving either the trigger signal or the collision signal), the trigger controller immediately sends a start command to the rapid inflation device.

[0063] The above content discloses the safety protection system of the present invention. Compared with the prior art, the present invention achieves significant breakthroughs in four dimensions: power protection, obstacle avoidance performance, fuselage protection, and adaptability, through an "active + passive" collaborative protection design. Its advantages are as follows: 1. Significantly improved power system safety: The protective shield around the propeller forms a physical isolation barrier, reducing the probability of the propeller colliding with foreign objects by 85% without affecting the propeller's aerodynamic performance. The risk of power system failure is reduced from 20% to less than 3%, fundamentally reducing the risk of aircraft crashes caused by propeller damage. 2. Improved obstacle avoidance performance: Detection accuracy has been improved from ≥0.02 meters to ≤0.01 meters, enabling precise identification of low-reflectivity obstacles such as small cables and tree branches with a diameter greater than 0.05 meters; the horizontal detection field of view has been expanded from ±6.5 degrees to ±8.5 degrees, effectively eliminating blind spots and achieving more comprehensive monitoring of the aircraft's circumferential environment; the overall system response speed has been accelerated from ≥25 m / s to ≤9 m / s, enabling timely issuance of obstacle avoidance commands in high-speed flight scenarios with speeds greater than 15 m / s, increasing the obstacle avoidance success rate to over 98%. 3. Enhanced airframe collision protection and personnel protection capabilities: Inflatable airbags cover critical areas and can rapidly inflate and deploy within 1 second in the event of a collision, effectively absorbing impact energy and reducing the impact force transmitted to the airframe by more than 70%; increasing the structural integrity rate of the aircraft after a collision from 30% without protection to 85%; especially in manned eVTOL scenarios, significantly reducing the personnel injury rate from 40% to below 5%, greatly ensuring the safety of life and property and significantly improving operational safety; 4. Significant adaptability and economy: The modular design allows for flexible selection and installation of propeller shields, millimeter-wave radar modules, and inflatable airbags according to the size and requirements of different aircraft models, without requiring structural modifications to the aircraft fuselage, thus broadening the application range; each protective module can be independently disassembled and replaced, and in the event of damage, there is no need to replace the entire protective system or the main fuselage structure, reducing maintenance costs by 60% and demonstrating significant economic benefits.

[0064] In another embodiment of the invention, a low-altitude aircraft is also included, which is an electric vertical takeoff and landing aircraft, comprising a fuselage, wings, a power system, landing gear, and a flight control system. The improvement lies in that the aircraft integrates the aforementioned emergency safety protection system, including a power system collision avoidance device, an active obstacle avoidance sensing device, and a passive energy absorption protection device, to achieve comprehensive and coordinated safety protection from power and sensing to the fuselage; such as Figure 5 The diagram shows the protective effect of the inflatable airbags on the aircraft after they are deployed.

[0065] Power system collision avoidance device: The annular protective cover is directly installed on the end of the power nacelle or motor support arm of the aircraft through its fixed bracket, completely enclosing each propeller; for multi-rotor UAVs or manned eVTOLs, each independent propeller unit is equipped with one of the aforementioned power system collision avoidance devices.

[0066] Active obstacle avoidance sensing device: The signal processing unit and obstacle avoidance decision unit are located in the fuselage. There are four millimeter-wave radar modules, located at the front, rear, left middle and right middle of the aircraft fuselage respectively. The millimeter-wave radar modules are all connected to the signal processing unit. The obstacle avoidance decision unit communicates with the aircraft control system through the aircraft bus.

[0067] Passive energy absorption protection device: Inflatable airbags are specifically arranged according to the most common collision sites of low-altitude aircraft, including but not limited to the nose, the junction of the wing and fuselage, the landing gear bay, the engine nacelle, the tail root, and the emergency exit of the cabin; the trigger controller is installed at the center of gravity of the aircraft fuselage, and the control lines of the pressure sensor and the rapid inflation device are connected to the trigger controller.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. An emergency safety protection system for aircraft, characterized in that, This system is used for active and passive coordinated protection of low-altitude aircraft, including a power system collision avoidance device, an active obstacle avoidance sensing device, and a passive energy absorption protection device. The power system anti-collision device includes an annular protective cover installed around the propeller, which forms a physical barrier for the propeller to block foreign objects. The active obstacle avoidance sensing device includes a millimeter-wave radar module, a signal processing unit, and an obstacle avoidance decision unit, which are used to detect and identify obstacles on the flight path and generate obstacle avoidance commands. The passive energy-absorbing protection device includes a modular inflatable airbag, a trigger controller, and a rapid inflation device, which is used to rapidly deploy before or during a collision to absorb the impact energy of the aircraft. The obstacle avoidance decision unit is communicatively connected to the trigger controller and the signal processing unit. When the obstacle avoidance decision unit receives obstacle information output by the signal processing unit and determines that the collision risk is higher than a preset threshold, it sends a trigger signal to the trigger controller. Based on the received trigger signal and / or the collision signal from the pressure sensor, the trigger controller sends a start command to the rapid inflation device to control the rapid inflation device to start and inflate the airbag.

2. The aircraft emergency safety protection system according to claim 1, characterized in that: The annular protective cover has a mesh structure and is made of high-strength nylon with a tensile strength of ≥60MPa. The inner diameter of the annular protective cover is 5cm larger than the maximum rotation diameter of the propeller, and the mesh aperture is 2cm. The annular protective shield is connected to the aircraft fuselage via a fixed bracket, and a buffer pad for absorbing impact energy is provided between the fixed bracket and the annular protective shield.

3. The aircraft emergency safety protection system according to claim 1, characterized in that: The millimeter-wave radar module is configured with four units, which are fixed to the front, rear, left middle, and right middle of the aircraft fuselage, respectively. The antenna of the front radar is parallel to the longitudinal axis of the aircraft and points forward, the antenna of the rear radar is parallel to the longitudinal axis and points backward, and the antennas of the left and right radars are perpendicular to the longitudinal axis and point to the left and right, respectively, to ensure that the detection direction of each radar is unobstructed.

4. The aircraft emergency safety protection system according to claim 3, characterized in that: The millimeter-wave radar module operates at a frequency of 24 GHz, has a detection range of 30 meters, a range resolution of ≤0.01 meters, and can identify obstacles with a diameter of ≥0.05 meters. Furthermore, the millimeter-wave radar module uses a phased array antenna with a horizontal detection angle of ±8.5 degrees and a vertical detection angle of ±5 degrees. The signal refresh rate of the millimeter-wave radar module is ≥10 Hz. Each millimeter-wave radar module is connected to the signal processing unit via a data bus, and the signal processing unit outputs obstacle information.

5. The aircraft emergency safety protection system according to claim 1, characterized in that: The obstacle avoidance decision unit has a built-in MCU for running the obstacle avoidance algorithm; The obstacle avoidance decision unit calculates the collision risk value based on the obstacle information output by the signal processing unit. When the risk value is ≥0.6, it generates an obstacle avoidance command and sends it to the aircraft's own control system to avoid the obstacle, and simultaneously sends a trigger signal to the trigger controller.

6. The aircraft emergency safety protection system according to claim 1, characterized in that: The inflatable airbag is made of polyamide fiber, with a thickness of ≤2cm when not inflated. It is installed in a folded state in a groove reserved on the surface of the aircraft fuselage and fixed by a detachable connector.

7. An aircraft emergency safety protection system according to claim 1 or 6, characterized in that: The passive energy absorption protection device also includes a pressure sensor, which is located inside the inflatable airbag or at the location of the inflatable airbag on the aircraft fuselage, and is used to monitor changes in collision pressure. The pressure sensor has a measurement range of 0-0.5MPa and an accuracy of ±0.01MPa; when a pressure surge of ≥0.05MPa is detected, a collision signal is sent to the trigger controller.

8. The aircraft emergency safety protection system according to claim 1, characterized in that: When the trigger controller receives either a trigger signal from the obstacle avoidance decision unit or a collision signal from the pressure sensor, it controls the rapid inflation device to start.

9. The aircraft emergency safety protection system according to claim 1, characterized in that: The rapid inflation device includes an igniter electrically connected to a trigger controller and a gas generator containing a solid gas-generating agent; the outlet of the gas generator is connected to the air inlet of the inflation bag through a gas guiding structure. The igniter responds to the start command, triggers and punctures the sealing membrane of the gas generator, and ignites the solid gas-generating agent to instantly produce nitrogen. The generated nitrogen passes through the outlet of the gas generator and the gas guiding structure in sequence, and fills the inflatable airbag, which expands within a predetermined time to form an elastic buffer layer.

10. A low-altitude aircraft, characterized in that, It is equipped with an emergency safety protection system as described in any one of claims 1 to 9.

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