A method for assessing the crashworthiness and injury of a manned eVTOL passenger protection system

Abstract

The present application relates to the technical field of vertical take-off and landing aircraft passenger protection, in particular to a landing suitability and injury evaluation method of a manned eVTOL passenger protection system, comprising the following steps: establishing a finite element model: based on the ATD open source model, constructing the passenger protection system of the manned eVTOL, simplifying the geometric appearance component solid model of the protection system, and establishing a finite element model according to the solid model; selecting the average unit stress as the convergence evaluation index: adopting the independent grid convergence analysis method for the seat model. The manned eVTOL passenger landing suitability and injury evaluation method and protection system establish a finite element model suitable for analyzing the response of the simple injury scale under vertical load, and use the finite element method to study the landing suitability evaluation and passenger injury evaluation method of the manned eVTOL passenger protection system.

Description

Technical Field

[0001] This invention relates to the field of occupant protection technology for vertical takeoff and landing (eVTOL) aircraft, specifically to a crashworthiness and damage assessment method for a manned eVTOL occupant protection system. Background Technology

[0002] Electric vertical takeoff and landing (eVTOL) aircraft, as a new generation of urban air transportation, have the characteristics of vertical takeoff and landing, environmental protection and energy saving, and low noise. They have shown great potential in alleviating urban traffic congestion and promoting the development of the low-altitude economy. However, as manned eVTOLs move towards commercial operation, their safety issues are becoming increasingly prominent, especially the crashworthiness design, which has become a key technical challenge.

[0003] Fallability refers to an aircraft's ability to protect its occupants in the event of a collision or other accident. Its core is to reduce the load and acceleration exerted on the human body by a collision. This concept originated in the aviation field. Traditional aircraft fallability studies have shown that occupant protection systems play a key role in aircraft crashes. They need to work together with seat belt systems and energy-absorbing floors to minimize the risk of injury to the human body.

[0004] Existing crashworthiness studies primarily focus on helicopters and fixed-wing aircraft. These studies are typically based on years of accident analysis and experimental data, covering multiple aspects from structural design to occupant protection. For newer low-altitude aircraft such as eVTOLs, their flight characteristics, structural configurations, and operating environments differ significantly from traditional aircraft. For example, eVTOLs often feature multi-rotor designs, fly at low altitudes more frequently, and require greater awareness and avoidance capabilities of low-altitude obstacles. Furthermore, the electric propulsion system and distributed propulsion layout of eVTOLs differ from those of traditional aircraft, potentially leading to different dynamic responses and injury modes of occupants in the event of a crash.

[0005] Compared with traditional aircraft, eVTOLs have significant differences in structural form, flight profile, and operating environment, making it difficult to directly apply existing crashworthiness theories. There is an urgent need to establish crashworthiness assessment theories and methods that are suitable for the characteristics of eVTOLs.

[0006] To address the aforementioned issues, we propose an improvement method for assessing the fall suitability and damage of a manned eVTOL occupant protection system. Summary of the Invention

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] This invention provides a method for assessing the fall suitability and damage of a manned eVTOL occupant protection system, comprising the following steps:

[0009] S01. Establishing a finite element model: Construct the occupant protection system for the manned eVTOL based on the ATD open-source model, simplify the geometric shape of the protection system's three-dimensional model, and establish a finite element model based on the three-dimensional model.

[0010] S02. Selecting average element stress as the convergence evaluation index: Using an independent mesh convergence analysis method for the seat model, the average stress of the seat under different mesh densities is compared to confirm the reliability of the mesh convergence analysis results. By applying loads representing the interaction between the dummy and the seat on the seat model, the mesh sensitivity of the seat model is evaluated separately.

[0011] S03. Establish a simulation model of the aircraft seat-ATD system: including the four-point seat belt, ATD model, and seat model;

[0012] S04. Finite Element Model Verification Analysis: The finite element model is tested, simulated, and load error evaluated for peak value error (GPV), time error (GPT), and curve shape error (SG) to verify the effectiveness of the model. The simulation and test error settings are less than 13%, the prediction error for peak value is less than 2%, and the prediction error for curve shape is less than 10%.

[0013] S05. Establish a multi-site injury evaluation index system for eVTOL occupants under vertical impact load, including the head, neck, lumbar spine and legs. Use a horizontal impact slide to conduct vertical experiments. The impact experiment adopts a 60° forward horizontal deflection angle, and the experimental seat and ATD maintain a 30° angle with the impact direction.

[0014] S06. Establish an evaluation index system for the impact of loading pulse and pitch angle on occupant injury.

[0015] As a preferred embodiment of the present invention, S02 includes:

[0016] Eleven types of mesh generation and element size tests were performed in the finite element preprocessing software. When the element size was less than 2-4 mm, the average element stress output tended to be stable, that is, the calculation error between 2 mm mesh and 5 mm mesh was less than 5%.

[0017] As a preferred embodiment of the present invention, S02 includes:

[0018] The seats are made of 7075-T6 aviation aluminum, and the seat material is defined using a general nonlinear finite element program;

[0019] The seat cushion and backrest are made of polyurethane foam, and a high-compression, low-density foam material with a density of 101 kg·m³ is used for modeling. -3 The Young's modulus is 1.16 MPa.

[0020] As a preferred embodiment of the present invention, S03 includes:

[0021] The four-point seat belt model is constructed using a hybrid modeling method that combines one-dimensional elements and two-dimensional shell elements. One-dimensional elements simulate the connection between the seat belt and the connection point, while two-dimensional elements simulate the contact and constraint of the seat belt on the ATD. In a general nonlinear finite element program, the dummy's human body is set as the main contact surface, and the overall structure of the seat and the contact surfaces between the dummy and the seat, and between the seat belt and the dummy, are set as secondary contact surfaces.

[0022] The overall structure of the seat adopts the CONTACT_AUTOMATIC_SINGLE_SURFACE contact algorithm; the contact between the dummy and the seat, and between the seat belt and the dummy, adopts the CONTACT_AUTOMATIC_SURFACE_TO_SURFACE contact algorithm.

[0023] As a preferred embodiment of the present invention, S04 includes:

[0024] The effectiveness of the model was verified by comparing the motion postures of the test dummy and the simulated dummy during the impact process and comparing the loads they were subjected to.

[0025] in:

[0026]

[0027]

[0028] In the above formula The peak value of the experimental curve. The time corresponding to the peak value of the experimental curve. The peak value of the simulation curve. This represents the time corresponding to the peak value of the simulation curve;

[0029] The curve shape error was assessed using the Sprague and Geers combined error method:

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] in For the test curve, For simulation curves, For amplitude error, For phase error, This is to account for the overall curve shape error.

[0037] As a preferred embodiment of the present invention, S05 includes:

[0038] The Head Injury Criterion (HIC) is used to assess the risk of head injury. The HIC formula is as follows:

[0039]

[0040] The above Represents the initial time of integration. This represents the end time of the points accumulation period. This indicates the acceleration upon head impact.

[0041] As a preferred embodiment of the present invention, S06 includes:

[0042] The pulse duration was set to 30-70ms. While ensuring the peak acceleration of 30g and the pulse triangle shape remained unchanged, the time to reach the peak pulse was set to 25-80ms at 10ms intervals to simulate and predict the occupant injury risk of eVTOL in a collision event.

[0043] The beneficial effects of this invention are as follows: This method and protection system for assessing the fall suitability and injury of eVTOL occupants establishes a finite element model suitable for analyzing the response of a simplified injury scale under vertical load. It uses the finite element method to study the fall suitability assessment and occupant injury assessment method of the eVTOL occupant protection system, providing a reference for the fall suitability and airworthiness certification of eVTOLs. A finite element model is established based on dynamic vertical impact tests, and the effectiveness of the established model is verified through comparative tests and simulation data. Based on a simplified injury scale, the damage risk to various parts of the occupant under vertical impact load is predicted, and the damage is further studied by changing parameters. This study investigates the relationship between different initial floor deformations, impact pulse curves, and initial pitch angles upon impact on human load and acceleration response. It aims to apply analytical techniques to the crashworthiness and airworthiness assessment of occupant protection systems in manned eVTOLs. A hybrid modeling method combining one-dimensional and two-dimensional shell elements is employed to construct a four-point seatbelt model. One-dimensional elements simulate the connection between the seatbelt and the connection points, while two-dimensional elements simulate the contact and constraint of the seatbelt on the ATD (Automatic Traction Device). The seat cushion and backrest of the aircraft seat are attached to the seat frame structure using the CONTACT_TIED_SURFACE_TO_SURFACE contact algorithm to prevent them from detaching or slipping. Attached Figure Description

[0044] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0045] Figure 1 This is a schematic diagram of the finite element model verification process for the manned eVTOL occupant protection system of the present invention;

[0046] Figure 2 This is a schematic diagram of the finite element model of the manned eVTOL occupant protection system of the present invention;

[0047] Figure 3 This is a schematic diagram of the contact surface structure of the present invention;

[0048] Figure 4 This is a schematic diagram of the impact direction in the impact test of the present invention;

[0049] Figure 5 This is a schematic diagram of the target waveform and the actual impact load waveform of the present invention;

[0050] Figure 6 This is a schematic diagram of the horizontal impact test bench system of the present invention;

[0051] Figure 7 This is a schematic diagram comparing the simulated and experimental lumbar spine force data of the present invention. Detailed Implementation

[0052] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0053] Example: Figure 1-7 As shown, a method for assessing the fall suitability and damage of a manned eVTOL occupant protection system includes the following steps:

[0054] S01. Establishing a finite element model: Construct the occupant protection system for the manned eVTOL based on the ATD open-source model, simplify the geometric shape of the protection system's three-dimensional model, and establish a finite element model based on the three-dimensional model.

[0055] S02. Selecting average element stress as the convergence evaluation index: Using an independent mesh convergence analysis method for the seat model, the average stress of the seat under different mesh densities is compared to confirm the reliability of the mesh convergence analysis results. By applying loads representing the interaction between the dummy and the seat on the seat model, the mesh sensitivity of the seat model is evaluated separately.

[0056] S03. Establish a simulation model of the aircraft seat-ATD system: including the four-point seat belt, ATD model, and seat model;

[0057] S04. Finite Element Model Verification Analysis: The finite element model is tested, simulated, and load error evaluated for peak value error (GPV), time error (GPT), and curve shape error (SG) to verify the effectiveness of the model. The simulation and test error settings are less than 13%, the prediction error for peak value is less than 2%, and the prediction error for curve shape is less than 10%.

[0058] S05. Establish a multi-site injury evaluation index system for eVTOL occupants under vertical impact load, including the head, neck, lumbar spine and legs. Use a horizontal impact slide to conduct vertical experiments. The impact experiment adopts a 60° forward horizontal deflection angle, and the experimental seat and ATD maintain a 30° angle with the impact direction.

[0059] S06. Establish an evaluation index system for the impact of loading pulse and pitch angle on occupant injury.

[0060] S02 includes:

[0061] Eleven types of mesh generation and element size tests were performed in the finite element preprocessing software. When the element size was 2-4 mm, the average element stress output tended to be stable, that is, the calculation error between 2 mm mesh and 4 mm mesh was less than 5%.

[0062] The seats are made of 7075-T6 aviation aluminum, and the seat material is defined using a general nonlinear finite element program;

[0063] The seat cushion and backrest are made of polyurethane foam, and a high-compression, low-density foam material with a density of 101 kg·m³ is used for modeling. -3 The Young's modulus is 1.16 MPa.

[0064] S03 includes:

[0065] The four-point seat belt model is constructed using a hybrid modeling method that combines one-dimensional elements and two-dimensional shell elements. One-dimensional elements simulate the connection between the seat belt and the connection point, while two-dimensional elements simulate the contact and constraint of the seat belt on the ATD. In a general nonlinear finite element program, the dummy's human body is set as the primary contact surface, and the overall structure of the seat and the contact surfaces between the dummy and the seat, and between the seat belt and the dummy, are set as secondary contact surfaces. The primary contact surface is represented in blue, and the secondary contact surface is represented in red.

[0066] The overall structure of the seat adopts the CONTACT_AUTOMATIC_SINGLE_SURFACE contact algorithm; the contact between the dummy and the seat, and between the seat belt and the dummy, adopts the CONTACT_AUTOMATIC_SURFACE_TO_SURFACE contact algorithm.

[0067] S04 includes:

[0068] The effectiveness of the model was verified by comparing the motion postures of the test dummy and the simulated dummy during the impact process and comparing the loads they were subjected to.

[0069] in:

[0070]

[0071]

[0072] In the above formula The peak value of the experimental curve. The time corresponding to the peak value of the experimental curve. The peak value of the simulation curve. This represents the time corresponding to the peak value of the simulation curve;

[0073] The curve shape error was assessed using the Sprague and Geers combined error method:

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080] in For the test curve, For simulation curves, For amplitude error, For phase error, This is to account for the overall curve shape error.

[0081] S05 includes:

[0082] The Head Injury Criterion (HIC) is used to assess the risk of head injury. The HIC formula is as follows:

[0083]

[0084] The above Represents the initial time of integration. This represents the end time of the points accumulation period. This indicates the acceleration upon head impact.

[0085] The seat, test fixtures, connectors, and load sensors are weighed and installed. After weighing, the ATD is symmetrically placed in the center of the seat, with its hands on its thighs and secured by a restraint system. The launch force is calculated by the control device based on the total mass of all moving parts, namely the total weight of the ATD, seat system, fixtures, and measuring devices, and the impact acceleration waveform. Subsequently, the computer system receives the launch force and operates the test bench. The test data of the ATD seat system is collected by the data acquisition system, and the movement of the ATD is recorded by a high-speed camera.

[0086] S06 includes:

[0087] The pulse duration was set to 30-70ms. While ensuring the peak acceleration of 30g and the pulse triangle shape remained unchanged, the time to reach the peak pulse was set to 25-80ms at 10ms intervals to simulate and predict the occupant injury risk of eVTOL in a collision event.

[0088] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for assessing the fall suitability and damage of a manned eVTOL occupant protection system, characterized in that, Includes the following steps: S01. Establishing a finite element model: Construct the occupant protection system for the manned eVTOL based on the ATD open-source model, simplify the geometric shape of the protection system's three-dimensional model, and establish a finite element model based on the three-dimensional model. S02. Selecting average element stress as the convergence evaluation index: Using an independent mesh convergence analysis method for the seat model, the average stress of the seat under different mesh densities is compared to confirm the reliability of the mesh convergence analysis results. By applying loads representing the interaction between the dummy and the seat on the seat model, the mesh sensitivity of the seat model is evaluated separately. S03. Establish a simulation model of the aircraft seat-ATD system: including the four-point seat belt, ATD model, and seat model; S04. Finite Element Model Verification Analysis: The finite element model is tested, simulated, and load error evaluated for peak value error (GPV), time error (GPT), and curve shape error (SG) to verify the effectiveness of the model. The simulation and test error settings are less than 13%, the prediction error for peak value is less than 2%, and the prediction error for curve shape is less than 10%. S05. Establish a multi-site injury evaluation index system for eVTOL occupants under vertical impact load, including the head, neck, lumbar spine and legs. Use a horizontal impact slide to conduct vertical experiments. The impact experiment adopts a 60° forward horizontal deflection angle, and the experimental seat and ATD maintain a 30° angle with the impact direction. S06. Establish an evaluation index system for the impact of loading pulse and pitch angle on occupant injury.

2. The fall suitability and damage assessment method for a manned eVTOL occupant protection system according to claim 1, characterized in that, S02 includes: Eleven types of mesh generation and element size tests were performed in the finite element preprocessing software. When the element size was 2-4 mm, the average element stress output tended to be stable, that is, the calculation error between 2 mm mesh and 4 mm mesh was less than 5%.

3. The fall suitability and damage assessment method for a manned eVTOL occupant protection system according to claim 2, characterized in that, S02 includes: The seats are made of 7075-T6 aviation aluminum, and the seat material is defined using a general nonlinear finite element program; The seat cushion and backrest are made of polyurethane foam, and a high-compression, low-density foam material with a density of 101 kg·m³ is used for modeling. -3 The Young's modulus is 1.16 MPa.

4. The fall suitability and damage assessment method for a manned eVTOL occupant protection system according to claim 1, characterized in that, S03 includes: The four-point seat belt model is constructed using a hybrid modeling method that combines one-dimensional elements and two-dimensional shell elements. One-dimensional elements simulate the connection between the seat belt and the connection point, while two-dimensional elements simulate the contact and constraint of the seat belt on the ATD. In a general nonlinear finite element program, the dummy's human body is set as the main contact surface, and the overall structure of the seat and the contact surfaces between the dummy and the seat, and between the seat belt and the dummy, are set as secondary contact surfaces. The overall seat structure uses CONTACT_AUTOMATIC_SINGLE_SURFACE contact calculation. Law; The contact between the dummy and the seat, and between the seat belt and the dummy, uses the CONTACT_AUTOMATIC_SURFACE_TO_SURFACE contact algorithm.

5. The fall suitability and damage assessment method for a manned eVTOL occupant protection system according to claim 1, characterized in that, S04 includes: A unified injury scale was established to unify the definition of different types of injuries by considering factors such as the degree of life-threatening injury, the degree of permanent damage, and the treatment period. The effectiveness of the model was verified by comparing the motion posture of the test dummy and the simulated dummy during the impact process and comparing the loads they were subjected to. in: In the above formula The peak value of the experimental curve. The time corresponding to the peak value of the experimental curve. The peak value of the simulation curve. This refers to the moment corresponding to the peak value of the simulation curve; The curve shape error was assessed using the Sprague and Geers combined error method: in For the test curve, For simulation curves, For amplitude error, For phase error, This is to account for the overall curve shape error.

6. The fall suitability and damage assessment method for a manned eVTOL occupant protection system according to claim 1, characterized in that, S05 includes: The Head Injury Criterion (HIC) is used to assess the risk of head injury. The HIC formula is as follows: The above Represents the initial time of integration. This represents the end time of the points accumulation period. This indicates the acceleration upon head impact.

7. The fall suitability and damage assessment method for a manned eVTOL occupant protection system according to claim 1, characterized in that, S06 includes: The pulse duration was set to 30-70ms. While ensuring the peak acceleration of 30g and the pulse triangle shape remained unchanged, the time to reach the peak pulse was set to 25-80ms at 10ms intervals to simulate and predict the occupant injury risk of eVTOL in a collision event.

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