Posture stabilizing device for parachute landing stage of electric vertical take-off and landing aircraft and analysis method

Abstract

The invention discloses an attitude stabilizing device for a parachute landing stage of an electric vertical take-off and landing aircraft and an analysis method. The attitude stabilizing device mainly comprises a shell, a guide plate, a fixing bolt, a friction adjusting clamp, a friction plate and a delay rope cutter. The device can save the time for pulling out the canopy at the initial stage of opening the parachute; and in the stable landing stage, on the premise that the appearance of the canopy is not affected, the swing angles of the parachute and the electric vertical take-off and landing aircraft are effectively reduced, the attitude stability is improved, it is guaranteed that the electric vertical take-off and landing aircraft touches the ground in a safe attitude, and the aircraft body is prevented from overturning. The attitude stability performance numerical analysis method provided by the invention not only provides a parameter design basis for an attitude stabilization device, but also evaluates the use effect after the device is adopted, and meanwhile, solves the technical difficulty of real-time adjustment of the length of a lifting belt of a simulation group.

Description

Technical Field

[0001] The invention relates to the technical field of emergency life-saving of electric vertical take-off and landing aircraft, and in particular to an attitude stabilizing device and an analysis method for an electric vertical take-off and landing aircraft in a parachute landing phase. Background Art

[0002] With the rapid development of electric vertical take-off and landing vehicles (eVTOL), their flight safety, especially emergency rescue after a failure in the air, has become a research hotspot at home and abroad. As a typical aerospace deceleration and life-saving device, parachutes have been widely used in emergency rescue of various small fixed-wing aircraft. However, electric vertical take-off and landing aircraft have the characteristics of complex surrounding flight environment and low flight altitude, which determines that they have higher requirements for the whole machine parachute. Compared with general whole machine parachutes, parachutes for vertical take-off and landing aircraft require the attitude of the parachute and the vertical take-off and landing aircraft to be stable, avoid scratches with the surrounding environment, ensure that the aircraft touches the ground at a safer attitude angle, and require a shorter parachute opening time.

[0003] In response to the above problems, different designers have proposed corresponding solutions, such as adding ribs (Xu Zhishuai, Wang Caiyi. A complete parachute. ZL202323142070.4). Although it can effectively reduce the swing angle and improve the attitude stability, the ribs will affect the inflation of the canopy, resulting in the occurrence of asymmetric inflation, which in turn increases the parachute opening time, while increasing the difficulty and cost of parachute manufacturing. By increasing the length of the parachute rope, the swing angle of the system can also be effectively reduced. In actual engineering, the group lifting belt is usually increased to increase the distance between the parachute and the decelerated object (Ewing. Recovery System Design Guide. Aviation Industry Press, 1988), but it will also increase the time to straighten the canopy, indirectly prolong the parachute opening time and increase the uncertainty of the inflation shape. The existing technology cannot solve the contradiction between the parachute opening time and attitude stability.

[0004] In summary, the field of emergency rescue research of electric vertical take-off and landing aircraft urgently needs an attitude stabilization device and analysis method for the parachute landing phase of an electric vertical take-off and landing aircraft, which will not affect the parachute opening speed while greatly improving the stability of the parachute and the electric vertical take-off and landing aircraft. Summary of the invention

[0005] The purpose of the present invention is to provide an attitude stabilization device and analysis method for an electric vertical take-off and landing aircraft during the parachute landing phase, which solves the problem of shortening the canopy straightening time while reducing the swing angle of the electric vertical take-off and landing aircraft and improving the ground contact stability.

[0006] The present invention adopts the following technical solution to solve the above technical problems: an attitude stabilizing device for an electric vertical take-off and landing aircraft during parachute landing, comprising a housing, a guide plate, a friction adjustment clamp, a friction plate and a delayed rope cutter, wherein:

[0007] The shell is a structure without a bottom and partially opened at the top, and is fixed to the top plate of the electric vertical take-off and landing aircraft by fixing bolts of ear plates on both sides;

[0008] The guide plate is L-shaped, with a long strip friction plate fixed on the upper part, and the two guide plates are symmetrically fixed at the local opening on the top of the shell by overlapping;

[0009] One end of the friction adjustment clamp is connected by a friction adjustment clamp connecting hinge, and the other end is used to adjust the gap of the friction adjustment clamp by an adjusting bolt, and the friction adjustment clamp is sleeved on two guide plates to fix the friction plate position;

[0010] The delayed rope cutter is fixed to one side of the housing;

[0011] The main assembly lifting strap is placed in the outer shell in a stacked manner, one end of which is connected to the top plate of the electric vertical take-off and landing aircraft through a main assembly lifting strap fixing ring, and one end of which is connected to the parachute rope and the auxiliary assembly lifting strap through a total connecting ring after passing through a gap between two friction plates; one end of the auxiliary assembly lifting strap is connected to the top plate of the electric vertical take-off and landing aircraft through a auxiliary assembly lifting strap fixing ring, and one end of which is connected to the parachute rope and the main assembly lifting strap through a total connecting ring after passing through a delayed rope cutter.

[0012] Furthermore, after the parachute is opened, the delayed rope cutter will cut After starting, the secondary group strap is cut off, and under the influence of the tension of the parachute rope, the main group strap is pulled out of the housing of the attitude stabilizer at a speed v drag Pull it out to stabilize the attitude by increasing the distance between the parachute and the electric vertical take-off and landing aircraft.

[0013] Furthermore, the delay t cut It is obtained by experiments or numerical simulations, where the experiments or numerical values ​​are carried out without the delayed rope cutter being activated, and the time t required for the electric vertical take-off and landing aircraft to enter a stable landing after the parachute is opened at n different wind speeds and different postures is recorded. n And the distance h dropped in this process n , n=1,2,3....., then the delay time t cut =max(t1,t2....t n ).

[0014] Furthermore, the pull-out speed v drag According to the formula v drag =(v max -v average )·f safe Definition, where v max is the maximum vertical impact speed that the electric vertical take-off and landing aircraft can withstand, v average is the average speed of the electric vertical take-off and landing aircraft in the steady landing stage after the parachute is opened, f safe is the safety factor, and f safe <0.9.

[0015] Furthermore, by adjusting the bolts, the gap between the two friction plates is increased or decreased, thereby adjusting the main assembly belt pulling friction and pulling speed v drag .

[0016] Furthermore, the pull-out speed v drag The corresponding relationship between the friction plate clearance and the friction plate clearance is obtained through the ground gravity pull-out test.

[0017] The present invention also provides a method for numerically analyzing the attitude stability performance of an electric vertical take-off and landing aircraft during the parachute landing phase, which is implemented based on the above device and is used to determine the length of the main assembly strap. The method comprises the following steps:

[0018] Step 1: Establish the parachute model, main assembly belt model, electric vertical take-off and landing aircraft model and flow field model in the steady landing stage, and assemble them. One end of the main assembly belt model is directly connected to the parachute rope of the parachute model, and the other end is directly connected to the top plate of the electric vertical take-off and landing aircraft model. The whole main assembly belt model is in a completely straightened state, and the initial length is l initial <0.2m, use n bar The rod units are evenly discretized;

[0019] Step 2: Define the initial speed of the parachute and electric vertical take-off and landing aircraft as the average speed v in the steady landing phase average , define a fixed calculation time step length Δt, and set the number of time steps m = 0;

[0020] Step 3: According to the formula Calculate the modified stress of each main assembly strap element Where E is the elastic modulus of the main group strap model, and the corrected stress is used as the initial stress of each rod element;

[0021] Step 4: In each time step, the model described in step 1 is calculated using an explicit finite element method based on fluid-solid coupling, and then proceed to step 5;

[0022] Step 5: Let m = m + 1, if m·Δt < t end Return to step 3, otherwise end the calculation and go to step 6, where t end To calculate the end time;

[0023] Step 6: Through post-processing software analysis, obtain the time-varying curve of the swing angle θ of the electric vertical take-off and landing aircraft model, and record the maximum change amplitude of the swing angle θ lower than the safe touchdown angle θ of the electric vertical take-off and landing aircraft design The time t θ ;

[0024] Step 7: Calculate the descent distance h of the VTOL aircraft during the pull-out phasedarg =h min -h lost -h safe , where h min is the minimum parachute opening altitude of vertical take-off and landing aircraft, h lost is the height lost from parachute opening to steady descent, h lost =max(h1,h2....h n ), h safe is the safety margin;

[0025] Step 8: Use formula t h =h darg / (v average +v drag ) Calculate the descent distance h of the vertical take-off and landing aircraft in the steady landing phase darg Time required h ;

[0026] Step 9: Calculate the length of the main strap l main = l initial +v drag ·min(t θ ,t h ).

[0027] Furthermore, the flow field model in step 1 moves along with the movement of the parachute model in the explicit calculation.

[0028] Furthermore, the electric vertical take-off and landing aircraft model in step 1 is a rigid body model and does not participate in fluid-solid coupling calculations.

[0029] Furthermore, the explicit finite element method based on fluid-solid coupling in step 4 is an ALE algorithm.

[0030] Compared with the prior art, the present invention has the following technical effects: while reducing the parachute opening time, the present invention reduces the swing angle of the electric vertical take-off and landing aircraft by adjusting the length of the main assembly strap, thereby improving stability and ensuring that the electric vertical take-off and landing aircraft touches the ground in a safer posture. The numerical analysis method of attitude stability performance can not only provide a design basis for the design of the stabilizing device, but also evaluate the stabilizing effect, which can save a lot of manpower and financial resources compared with traditional test methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the overall front view of the attitude stabilizer.

[0032] Figure 2 It is the overall left view of the attitude stabilizer.

[0033] Figure 3 It is a schematic diagram of the guide plate and friction plate.

[0034] Figure 4 It is a top view of the assembly of the attitude stabilizer housing and the guide plate.

[0035] Figure 5 Schematic diagram of the friction adjustment clamp.

[0036] Figure 6 It is a partial top view of the assembly of the friction adjustment clamp and the guide plate.

[0037] Figure 7 It is a schematic diagram of the attitude stabilization device in which the main assembly strap is pulled out by the tension of the parachute rope after the delayed rope cutter is activated.

[0038] Figure 8 It is a model of a parachute in a stable landing state, a main assembly carrying strap and an electric vertical take-off and landing aircraft.

[0039] Fig. 9 It is a model that is submitted for calculation after the structural domain (parachute, main assembly carrying belt and electric vertical take-off and landing aircraft) is assembled with the flow field model.

[0040] Fig.10 This is a schematic diagram of the model changes after the 600,000th step of calculation.

[0041] Fig.11 This is a schematic diagram of the model changes after the 1.6 millionth step of calculation.

[0042] Fig.12 It is a schematic diagram of the swing angle change curve of the electric vertical take-off and landing aircraft in the steady landing stage before and after the main assembly strap extension strategy is adopted.

[0043] In the figure, 1-friction adjustment clamp, 2-shell, 3-main assembly lifting strap, 4-electric vertical take-off and landing aircraft top plate, 5-fixing bolt, 6-parachute rope, 7-secondary assembly lifting strap, 8-delay rope cutter, 9-main assembly lifting strap fixing ring, 10-secondary assembly lifting strap fixing ring, 11-total connecting ring, 12-guide plate, 13-friction adjustment clamp connecting hinge, 14-adjusting bolt, 15-friction plate, 16-parachute model, 17-main assembly lifting strap model, 18-electric vertical take-off and landing aircraft model, 19-flow field model. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention. At the same time, it can be understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of ordinary technicians in the field to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and unless defined as here, will not be interpreted with an idealized or overly formal meaning.

[0045] The present invention provides an attitude stabilizing device for an electric vertical take-off and landing aircraft during the parachute landing phase. Figure 1 and Figure 2 As shown, the device includes a housing 2, a guide plate 12, a fixing bolt 5, a friction adjustment clamp 1, a friction plate 15 and a delayed rope cutter 8. The housing 2 is a structure without a bottom and partially opened at the top, and is fixed to the top plate 4 of the electric vertical take-off and landing aircraft through four fixing bolts 5 on the ear plates on both sides, and the delayed rope cutter 8 is fixed to one side of the housing 2.

[0046] like Figure 3 and Figure 4 As shown, the guide plate 12 is L-shaped, with a long strip friction plate 15 fixed on the upper part, and two guide plates 12 are symmetrically fixed at the local opening at the top of the housing 2 by overlapping. The bottom of the L-shaped guide plate is flush with the top of the housing 2, and can be connected by welding or bolts.

[0047] like Figure 5 and Figure 6 As shown, one end of the friction adjustment clamp 1 is connected by a friction adjustment clamp connecting hinge 13, and the other end is used to adjust the gap of the friction adjustment clamp 1 through an anti-loosening adjustment bolt 14, and a fixed friction plate 15 is arranged on the inner side of the two guide plates 12, and the friction adjustment clamp 1 is sleeved on the outer side of the position of the fixed friction plate 15 of the two guide plates 12. The friction plate 15 is a rubber friction plate.

[0048] Before using the device, Figure 1 As shown, the length of the main group handle 1 is l main , whose value is obtained by the numerical analysis method of attitude stability performance described later, is placed in the housing 2 in a stacked manner, one end of which is connected to the top plate 4 of the electric vertical take-off and landing aircraft through the main assembly lifting belt fixing ring 9, and one end of which passes through the gap between the two friction plates 15 and is connected to the parachute rope 6 and the auxiliary assembly lifting belt 7 through the main connecting ring 11. One end of the auxiliary assembly lifting belt 7 is connected to the top plate 4 of the electric vertical take-off and landing aircraft through the auxiliary assembly lifting belt fixing ring 10, and one end of which passes through the delayed rope cutting device 8 and is connected to the parachute rope 6 and the main assembly lifting belt 3 through the main connecting ring 11. Figure 6As shown, by adjusting the bolt 14, the gap between the two friction plates 15 is increased or decreased, thereby adjusting the friction force and the pulling speed v of the main assembly lifting belt 3 pulled out from the posture stabilizing device. drag . The pulling speed v drag The corresponding relationship between the gap between the friction plate 15 and the corresponding friction plate 15 needs to be obtained in advance through a ground gravity pull-out test.

[0049] When the device is used, Figure 7 As shown, the delayed rope cutter 8 passes through the delay time t cut After starting, the secondary group carrying strap 7 is cut off, and under the influence of the tension of the parachute rope 6, the main group carrying strap 3 is pulled out of the housing 2 of the attitude stabilizing device at a speed v drag Pull it out to stabilize the attitude by increasing the distance between the parachute and the electric vertical take-off and landing aircraft.

[0050] Among them, the delay time t cut The time t required for the electric vertical take-off and landing aircraft to enter a stable landing after the parachute is opened at n different wind speeds and different postures is recorded. n (n=1,2,3.....) and the descending distance h in this process n (n=1,2,3.....), then the delay time t cut =max(t1,t2....t n ).

[0051] As shown in Table 1, this implementation case uses a numerical method to calculate the time t required for a certain type of single-person electric vertical take-off and landing aircraft and its supporting parachute to enter a stable landing. n And the distance h dropped in this process n (For parachute type, please refer to: Xu Zhishuai, Wang Caiyi. A complete parachute. ZL202323142070.4; for numerical calculation method, please refer to: H Cheng L Wei, B Zhou, Q He, P Xiao. Numerical study of lateral wind effect on parachute dropping based on finite element method. MECHANIKA, 2017, 23(1): 126-131.), then the delay time t cut =max(t1,t2....t n ) = t 43 =3.6s.

[0052] Table 1. Time required to enter steady state n And the distance h dropped in this process n

[0053]

[0054]

[0055] The speed v at which the main assembly carrying strap 3 is pulled out from the housing 2 drag , calculated by formula (1):

[0056] v drag =(v max -v average )·f safe (1)

[0057] Among them, v max is the maximum vertical impact speed that the electric vertical take-off and landing aircraft can withstand, v average is the average speed of the electric vertical take-off and landing aircraft in the steady landing stage after the parachute is opened, f safe is the safety factor, and f safe <0.9.

[0058] Taking the above-mentioned single-person electric vertical take-off and landing aircraft as an example, v max is 6.5m / s, and the steady descent speed v of the aircraft equipped with a parachute is average The pull-out speed v can be calculated according to formula 1. drag It is 1.275m / s.

[0059] The single-person electric vertical take-off and landing aircraft is also used as an example to illustrate the numerical analysis method of attitude stability performance:

[0060] Step 1: If Figure 8 and Fig. 9 As shown, a parachute model 16, a main assembly lifting strap model 17, an electric vertical take-off and landing aircraft model 18 and a flow field model 19 in the steady landing stage are established and assembled, wherein one end of the main assembly lifting strap model 17 is directly connected to the parachute rope of the parachute model 16, and the other end is directly connected to the top plate of the electric vertical take-off and landing aircraft model 18. The whole main assembly lifting strap model 17 is in a completely straightened state, and the initial length is l initial <0.2m, use n bar The rod units are uniformly discretized, and the electric vertical take-off and landing aircraft model 18 is a rigid body model and does not participate in the fluid-solid coupling calculation. initial The value is 0.15m, n bar The value is 10.

[0061] Step 2: Define the initial speed of the parachute and electric vertical take-off and landing aircraft as the average speed v in the steady landing phase average , define a fixed calculation time step length Δt, set the time step number m=0, and in this implementation case, Δt takes the value of 5e-6s.

[0062] Step 3: Calculate the modified stress of each main assembly strap unit according to formula (2):

[0063]

[0064] Wherein, E is the elastic modulus of the main group strap model 17, and in this embodiment, E is 3e8Pa. When m=0, the modified stress of each unit is The corrected stress is 12750Pa, and the corrected stress is used as the initial stress of each rod element, and the process goes to step 4.

[0065] Step 4: In each time step, the model described in step 1 is calculated using an explicit finite element method based on fluid-solid coupling to obtain the motion trajectory, attitude change and other results of the electric vertical take-off and landing aircraft. Among them, the fluid-solid coupling algorithm adopts the ALE algorithm, and the flow field model 19 moves with the parachute model 16 in the explicit calculation (for specific algorithms, please refer to: HCheng L Wei, B Zhou, Q He, P Xiao. Numerical study of lateral wind effect on parachute dropping based on finite element method. MECHANIKA, 2017, 23 (1): 126-131.), and then proceed to step 5.

[0066] Step 5: Let m = m + 1, if m·Δt < t end Return to step 3, otherwise end the calculation and go to step 6, where t end is the calculation end time. In this implementation case, t end The value is 10s.

[0067] like Fig.10 and Fig.11 As shown, through the cyclic calculation from step 3 to step 5, the length change of the main assembly carrying strap model 17 at different times, as well as the changes in the postures of the parachute model 16 and the electric vertical take-off and landing aircraft model 18 can be obtained. It can be obviously found that with the extension of the main assembly carrying strap, the swing angle of the electric vertical take-off and landing aircraft model gradually decreases.

[0068] Step 6: Through post-processing software analysis, obtain the time-varying curve of the swing angle θ of the electric vertical take-off and landing aircraft model 18, and record the maximum change amplitude of the swing angle θ lower than the safe touchdown angle θ of the electric vertical take-off and landing aircraft design The time t θ .

[0069] like Fig.12As shown in the figure, after adopting the extension strategy of the main assembly strap, the swing angle of the electric vertical take-off and landing aircraft model gradually becomes smaller, and the frequency of change is decreasing. The electric vertical take-off and landing aircraft will touch the ground in a more favorable posture. After 2.58s, the maximum change of the swing angle θ is lower than the safe touchdown angle θ design (In this implementation case, θ design Take the value of 15°), that is, t θ =2.58s. At the same time, Fig.12 It can also be found that in the comparative example that does not adopt the extension strategy of the main assembly strap, the swing angle of the electric vertical take-off and landing aircraft model is large and no convergence trend is observed.

[0070] Step 7: Calculate the descent distance h of the vertical take-off and landing aircraft in the pull-out phase according to formula (3) darg :

[0071] h darg =h min -h lost -h safe (3)

[0072] Among them, h min is the minimum parachute opening altitude of vertical take-off and landing aircraft, h lost is the loss height from parachute opening to steady descent, i.e. h lost =max(h1,h2....h n ), h safe It is a safety margin and its value is 2m.

[0073] In this implementation case, min The value is 50m,h min It can be seen from Table 1 that h lost =max(h1,h2....h n )=h 43 =24.6m, h can be calculated by formula (3) darg =50-24.6-2=23.4m.

[0074] Step 8: Calculate the descent distance h of the vertical take-off and landing aircraft in the steady landing phase according to formula (4) darg Time required h :

[0075] t h =h darg / (v average +v drag )(4)

[0076] In this implementation case, it can be known from the formula that t h =23.4 / (5+1.275)=3.729s.

[0077] Step 9: Calculate the main assembly strap length l according to formula (5) main :

[0078] l main = l initial +v drag ·min(t θ ,t h )(5)

[0079] In this embodiment, the length of the main group strap l can be known by this formula main =0.15+1.275·min(2.58,3.729)=3.44m.

[0080] In summary, the device provided by the present invention can realize the main group carrying strap length strategy at different stages: in the early stage of opening the parachute, a shorter length is used to save the time of pulling out the canopy; in the steady landing stage, an automatic extension strategy is adopted to effectively reduce the swing angle of the parachute and the electric vertical take-off and landing aircraft without affecting the shape of the canopy, improve the attitude stability, and reduce the probability of the parachute-carrying system scratching the external environment, while ensuring that the electric vertical take-off and landing aircraft touches the ground in a better attitude to prevent the body from overturning. The numerical analysis method of attitude stability performance provided by the present invention is also effective and accurate, which not only provides a parameter design basis for the attitude stabilization device, but also evaluates the use effect after adopting the device. More importantly, while saving manpower, financial resources and time costs, it solves the technical difficulties of real-time adjustment of the length of the simulation group carrying strap.

[0081] Based on the same technical solution, the present invention also provides an electronic device, comprising one or more processors, one or more memories and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing the construction of a marine environment impact database.

[0082] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0083] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0084] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0085] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0086] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technology can understand and think of any changes or substitutions within the technical scope disclosed by the present invention, which should be included in the scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An attitude stabilizing device for an electric vertical take-off and landing aircraft during parachute landing, characterized in that: It comprises a housing (2), a guide plate (12), a friction adjustment clamp (1), a friction plate (15) and a delayed rope cutter (8), wherein: The housing (2) is a structure without a bottom and with a partially open top, and is fixed to the top plate (4) of the electric vertical take-off and landing aircraft by fixing bolts (5) of ear plates on both sides; The guide plate (12) is L-shaped, with a long strip friction plate (15) fixed on the upper part, and the two guide plates (12) are symmetrically fixed at the local opening on the top of the housing (2) by overlapping. One end of the friction adjustment clamp (1) is connected by a friction adjustment clamp connecting hinge (13), and the other end is used to adjust the gap of the friction adjustment clamp (1) through an adjusting bolt (14). The friction adjustment clamp (1) is sleeved on the two guide plates (12) to fix the friction plate (15). The delayed rope cutter (8) is fixed on one side of the housing (2); The main assembly lifting belt (3) is stacked and placed in the housing (2), one end of which is connected to the top plate (4) of the electric vertical take-off and landing aircraft through a main assembly lifting belt fixing ring (9), and one end of which passes through the gap between two friction plates (15) and is connected to the parachute rope (6) and the auxiliary assembly lifting belt (7) through a general connecting ring (11); one end of the auxiliary assembly lifting belt (7) is connected to the top plate (4) of the electric vertical take-off and landing aircraft through a auxiliary assembly lifting belt fixing ring (10), and one end of which passes through a delayed rope cutting device (8) and is connected to the parachute rope (6) and the main assembly lifting belt (3) through a general connecting ring (11).

2. The attitude stabilizing device for an electric vertical take-off and landing aircraft during parachute landing according to claim 1, characterized in that: After the parachute is opened, the delayed rope cutter (8) is turned off after a delay time t cut After starting, the secondary group carrying strap (7) is cut off, and under the influence of the tension of the parachute rope (6), the main group carrying strap (3) is pulled out from the housing (2) of the attitude stabilizing device at a speed v drag Pull it out to stabilize the attitude by increasing the distance between the parachute and the electric vertical take-off and landing aircraft.

3. The attitude stabilizing device for an electric vertical take-off and landing aircraft during parachute landing according to claim 2, characterized in that: The delay t cut The time t required for the electric vertical take-off and landing aircraft to enter a stable landing after the parachute is opened at n different wind speeds and different postures is recorded. n And the distance h dropped in this process n , n=1,2,3....., then the delay time t cut =max(t1,t2....t n ).

4. The attitude stabilizing device for an electric vertical take-off and landing aircraft during parachute landing according to claim 2, characterized in that: The pull-out speed v drag According to the formula v drag =(v max -v average )·f safe Definition, where v max is the maximum vertical impact speed that the electric vertical take-off and landing aircraft can withstand, v average is the average speed of the electric vertical take-off and landing aircraft in the steady landing stage after the parachute is opened, f safe is the safety factor, and f safe <0.

9.

5. The attitude stabilizing device for parachuting of an electric vertical take-off and landing aircraft according to claim 1, 2 or 4, characterized in that: By adjusting the bolt (14), the gap between the two friction plates (15) is increased or decreased, thereby adjusting the pulling friction force and pulling speed v of the main assembly lifting belt (3). drag .

6. The attitude stabilizing device for an electric vertical take-off and landing aircraft during parachute landing according to claim 5, characterized in that: The pull-out speed v drag The corresponding relationship between the clearance of the friction plate (15) and the corresponding friction plate (15) is obtained through a ground gravity pull-out test.

7. A numerical analysis method for attitude stability performance of an electric vertical take-off and landing aircraft during parachute landing phase, characterized in that: The method is implemented based on the device described in any one of claims 1 to 4 and is used to determine the length of the main group handle. The method comprises the following steps: Step 1: Establish a parachute model (16), a main assembly lifting strap model (17), an electric vertical take-off and landing aircraft model (18) and a flow field model (19) in the steady landing stage, and assemble them, wherein one end of the main assembly lifting strap model (17) is directly connected to the parachute rope of the parachute model (16), and the other end is directly connected to the top plate of the electric vertical take-off and landing aircraft model (18). The whole main assembly lifting strap model (17) is in a completely straightened state, and the initial length is l initial <0.2m, use n bar The rod units are evenly discretized; Step 2: Define the initial speed of the parachute and electric vertical take-off and landing aircraft as the average speed v in the steady landing phase average , define a fixed calculation time step length Δt, and set the number of time steps m = 0; Step 3: According to the formula Calculate the modified stress of each main assembly strap element Where E is the elastic modulus of the main group strap model, and the corrected stress is used as the initial stress of each rod element; Step 4: In each time step, the model described in step 1 is calculated using an explicit finite element method based on fluid-solid coupling, and then proceed to step 5; Step 5: Let m = m + 1, if m·Δt < t end Return to step 3, otherwise end the calculation and go to step 6, where t end To calculate the end time; Step 6: Through post-processing software analysis, obtain the time-varying curve of the swing angle θ of the electric vertical take-off and landing aircraft model, and record the maximum change amplitude of the swing angle θ lower than the safe touchdown angle θ of the electric vertical take-off and landing aircraft design The time t θ ; Step 7: Calculate the descent distance h of the VTOL aircraft during the pull-out phase darg =h min -h lost -h safe , where h min is the minimum parachute opening altitude of vertical take-off and landing aircraft, h lost is the height lost from parachute opening to steady descent, h lost =max(h1,h2....h n ), h safe is the safety margin; Step 8: Use formula t h =h darg / (v average +v drag ) Calculate the descent distance h of the vertical take-off and landing aircraft in the steady landing phase darg Time required h ; Step 9: Calculate the length of the main strap l main = l initial +v drag ·min(t θ ,t h ).

8. The method according to claim 7, characterized in that The flow field model (19) in the step 1 moves along with the movement of the parachute model (16) in the explicit calculation.

9. The method according to claim 7, characterized in that: The electric vertical take-off and landing aircraft model (18) in step 1 is a rigid body model and does not participate in the fluid-solid coupling calculation.

10. The method according to claim 7, characterized in that The explicit finite element method based on fluid-solid coupling in step 4 is the ALE algorithm.

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