A method for calculating the shipboard roll stability of a helicopter taking into account the compression of the landing gear

Abstract

The present application belongs to the overall field of helicopters, and relates to a method for calculating the stability of a helicopter in a shipboard roll considering the compression of the landing gear. The method comprises: considering the ship sway motion factors and wind load factors to which the helicopter is subjected, determining the changes in the compression of the landing gear on both sides after the landing gear is affected by the above factors; calculating the new center of gravity coordinates of the helicopter after the landing gear is affected according to the changes in the compression of the landing gear on both sides; calculating the stability moment and the overturning moment of the helicopter according to the new center of gravity coordinates; and comparing the stability moment and the overturning moment to determine whether the helicopter is rolled over.

Description

Technical Field

[0001] This invention belongs to the field of helicopters and relates to a method for calculating the rollover stability of a helicopter on board a ship, taking into account the landing gear compression. Background Technology

[0002] The existing technology discloses a method for calculating the stability of a helicopter freely parked on a ship deck, which calculates the overturning stability and sideslip stability of the helicopter deck. However, it does not consider the impact of the helicopter landing gear compression on the rollover, which makes the calculation results unrealistic. Calculating according to this method will lead to the risk of the helicopter rolling over on the ship. Summary of the Invention

[0003] The purpose of this invention is to take into account the influence of helicopter landing gear compression, so that the calculation results are closer to reality.

[0004] The technical solution of the present invention:

[0005] A method for calculating the rollover stability of a helicopter on board a ship, considering landing gear compression, includes:

[0006] Considering the ship's rolling motion and wind load factors affecting the helicopter, determine the changes in the compression on both sides of the helicopter landing gear after being affected by the above factors.

[0007] Based on the changes in compression on both sides, calculate the new center of gravity coordinates of the helicopter after being affected by the landing gear;

[0008] Calculate the stabilizing moment and overturning moment of the helicopter based on the new center of gravity coordinates;

[0009] By comparing the stabilizing moment and the overturning moment, it can be determined whether the helicopter has rolled over.

[0010] To determine if a helicopter has rolled over to one side, the ship's rolling motion and wind load factors are considered. The changes in compression on both sides of the helicopter landing gear after being affected by these factors are determined, including:

[0011] For this iteration, based on the grounding point coordinates of the main landing gear and auxiliary landing gear on this side obtained in the previous iteration, the distances from the main landing gear to the auxiliary landing gear are calculated respectively.

[0012] A force analysis was performed on the vertical loads borne by the main and auxiliary landing gear on the pressure side during the critical overturning state, and equilibrium equations based on the tilt axis on that side were established. The equilibrium equations are as follows:

[0013]

[0014] Where Fz is the resultant vertical force acting on the helicopter, and Mp is the torque of the helicopter about the p-axis, which is perpendicular to the tilt axis; F fuzuTo assist the vertical support reaction force of the landing gear, F zhu Main landing gear vertical support reaction force; M windp Let n be the torque of the wind load about the p-axis. z For vertical inertial overload, d zf d is the distance from the main landing gear to the auxiliary landing gear on that side. p F is the horizontal distance from the center of gravity to the p-axis. windz Let d be the vertical component of the wind load. h n is the height of the center of gravity; xy_p The horizontal overload is perpendicular to the p-axis and points towards the p-axis; the tilt axis is the line connecting the main landing gear touchdown point and the auxiliary landing gear touchdown point on this side; M is the mass of the helicopter, and g is the acceleration due to gravity.

[0015] Based on the above equilibrium equations, solve for the vertical support reaction force of the auxiliary landing gear and the vertical support reaction force of the main landing gear on this side;

[0016] Using the known static pressure curves of the landing gear buffer strut and tires on that side, the compression of the main landing gear and auxiliary landing gear on that side is calculated, thereby calculating the new center of gravity coordinates of the helicopter and the new touchdown coordinates of each landing gear.

[0017] Calculating the new center of gravity coordinates of the helicopter includes:

[0018] When one main landing gear is compressed, the helicopter deflects. With the auxiliary landing gear contact point as the center of rotation, let the longitudinal deflection angle be α and the lateral deflection angle be β.

[0019] Based on the compression of the main landing gear and auxiliary landing gear on that side, calculate the coordinates of the touchdown points of each landing gear before deflection in the ship's coordinate system.

[0020] Calculate α and β, assuming that the vertical coordinates of the contact points of the two front landing gears are 0 after the rotation in the ship's coordinate system.

[0021] Based on α, β, the original center of gravity coordinates, and the touchdown point coordinates of the main and auxiliary landing gears obtained in the previous iteration, the new center of gravity coordinates after deflection are calculated.

[0022] Calculate α and β, including:

[0023] Substituting the above conditions and the coordinates of the touchdown points of each landing gear before deflection in the ship's coordinate system into the following formula, we obtain α and β, as shown in the following formula:

[0024]

[0025]

[0026]

[0027] The coordinates of the touchdown point of the left landing gear before deflection; The coordinates of the touchdown point of the left landing gear after deflection are given; T is the transformation matrix. The coordinates of the touchdown point of the right landing gear before deflection; These are the coordinates of the touchdown point of the right landing gear after deflection.

[0028] The formulas for calculating the new coordinates of the center of gravity and the new coordinates of the touchdown points of each landing gear after deflection are as follows:

[0029] Coord G new =T(Coord) G -Coord fuzu_d )+Coord fuzu_d ;

[0030] Coord left new =T(Coord) left_d -Coord fuzu_d )+Coord fuzu_d ;

[0031] Coord right new =T(Coord) right_d -Coord fuzu_d )+Coord fuzu_d ;

[0032] Coord fuzu new =Coord fuzu_d ;

[0033] Among them, Coord G new For the new center of gravity coordinates, Coord left new Coord provides the new coordinates for the touchdown point of the left landing gear. right new Coord provides the new coordinates for the touchdown point of the right landing gear. fuzu new To assist in determining the new coordinates of the landing gear's touchdown point, Coord left_d Coord right_d Coord fuzu_d These are the coordinates of the grounding points of the left, right, and auxiliary landing gear obtained from the previous iteration.

[0034] After calculating the new coordinates of the helicopter's center of gravity and the new coordinates of the touchdown points of each landing gear, the method further includes:

[0035] The iteration stops when the difference between the new centroid coordinates and the original centroid coordinates is less than a preset threshold.

[0036] Regarding the judgment of left-leaning

[0037] n xy_p =-n x cosθ-n y sinθ;

[0038] M windp =M wind_x sinθ-M wind_y cosθ;

[0039]

[0040] Where, x f y f To assist in the landing gear coordinates, x l y l Let n be the coordinates of the left landing gear. x For longitudinal overload of the helicopter, n y For helicopter lateral overload, M wind_x For longitudinal wind load, M wind_y This refers to lateral wind load.

[0041] Regarding the judgment of right-leaning

[0042] n xy_p =-n x cosθ+n y sinθ;

[0043] M windp =-M wind_x sinθ-M wind_y cosθ;

[0044] Attached Figure Description

[0045] Figure 1a This is a schematic diagram of the helicopter's overturning axis.

[0046] Figure 1b This is a schematic diagram of the helicopter's overturning axis.

[0047] Figure 1c This is a schematic diagram of the helicopter's overturning axis.

[0048] Figure 2 This is a schematic diagram of the stabilizing force.

[0049] Figure 3 This is a schematic diagram of the overturning force.

[0050] Figure 4a This is a schematic diagram of load synthesis.

[0051] Figure 4b This is a schematic diagram of the load torque synthesis.

[0052] Figure 5a This is a schematic diagram of load synthesis.

[0053] Figure 5b This is a schematic diagram of the load torque synthesis.

[0054] Figure 6 This is a diagram illustrating the shift in the center of gravity caused by the different compression levels of the left and right tires.

[0055] Figure 7 This is a schematic diagram of the forces acting on the body in the critical state of overturning.

[0056] Figure 8 This is a schematic diagram of the coordinate system. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0058] 1. Calculation of initial compression of landing gear

[0059] The landing gear compression is obtained by calculating the landing gear support reaction force, and then the coordinates of the center of gravity after the offset are calculated based on the geometric compatibility relationship. The specific calculation method is as follows.

[0060] (1) Calculation of support reaction force in shutdown state

[0061] The equilibrium equations are as follows:

[0062]

[0063] It can be solved.

[0064]

[0065]

[0066] F fuzu =mg-F left -F right ;

[0067] In the formula, F fuzu To assist the vertical support reaction force of the landing gear, F left F is the vertical support reaction force of the left main landing gear. right This represents the vertical support reaction force of the right main landing gear.f y f To assist in the landing gear coordinates, x l y l Let x be the coordinates of the left landing gear. r y r The coordinates are for the right landing gear.

[0068] Solve for the support reaction force F fuzu F left and F right Then, the compression of the buffer support is obtained through the static pressure curve.

[0069] (2) Calculation of landing gear compression at the critical overturning state:

[0070] The vertical load is borne by the main landing gear and auxiliary landing gear on the pressure side. See the force diagram below. Figure 7 Establish the equilibrium equation:

[0071]

[0072] In the formula, M windp Let n be the torque of the wind load about the p-axis (perpendicular to the tilt axis). z For z-axis inertial overload, d zf The distance d from the main landing gear to the auxiliary landing gear p F is the horizontal distance from the center of gravity to the p-axis (perpendicular to the tilt axis). windz Let d be the z-axis component of the wind load. h This is the height of the center of gravity. xy_p This is a horizontal overload perpendicular to the p-axis, with the direction pointing towards the p-axis.

[0073] d p d zf n xy_p M windp Calculate using the following formula:

[0074]

[0075]

[0076]

[0077] When tilting to the right,

[0078] n xy_p =-n x cosθ+n y sinθ

[0079] M windp =-M wind_x sinθ-M wind_y cosθ

[0080] When tilting to the left,

[0081] n xy_p =-n x cosθ-n y sinθ

[0082] M windp =M wind_x sinθ-M wind_y cosθ

[0083] Solve for the support reaction force F zhu F fuzu Then, the landing gear compression is obtained through the static pressure curve.

[0084] 2. Tilting Angle Calculation

[0085] For ease of calculation, such as Figure 8 As shown, the coordinate systems used are:

[0086] a) Initial body coordinate system O o -x o y o z o The coordinate system under normal shutdown conditions;

[0087] b) Coordinate system O with the auxiliary landing gear compression touchdown point as the origin m -x m y m z m The coordinate axes point in the same direction as the body coordinate system.

[0088] When the compression of the two main landing gears is inconsistent, the helicopter deflects. With the auxiliary landing gear contact point as the center of rotation, let the longitudinal rotation angle be α and the lateral rotation angle be β.

[0089] In the O-xyz body coordinate system, the coordinates of the landing gear's contact point after compression are as follows:

[0090] Coord fuzu_d =Coord fuzu +[0 0L fuzu ] T

[0091] Coord left_d =Coord left +[0 0L left ] T

[0092] Coord right_d =Coord right +[0 0L right ] T

[0093] In the formula, Coord left Coord right Coord fuzu These are the coordinates of the touchdown points of the left main landing gear, right main landing gear, and auxiliary landing gear in their natural extension states, respectively, in the fuselage coordinate system. (L) fuzu L left L right This refers to the landing gear compression.

[0094] For rocker-arm landing gear, the offset of the x-coordinate is considered, and the x-coordinate is taken as the value after the landing gear is compressed.

[0095] For ease of calculation, a coordinate system O is established with the auxiliary landing gear compression point as the origin. m -x m y m z m .

[0096] O m -x m y m z m In the coordinate system, the coordinates of the lowest point of the auxiliary landing gear, the lowest point of the left main landing gear, and the lowest point of the right main landing gear after compression are as follows:

[0097]

[0098]

[0099]

[0100] The uneven compression of the two main landing gears caused the fuselage to rotate around the auxiliary landing gear. After rotation, the main landing gear touchdown point was at O. m -x m y m z m The coordinates in the coordinate system are:

[0101]

[0102]

[0103]

[0104] In the formula, T is the coordinate transformation matrix.

[0105] The z-coordinates of the left and right main grounding points are at O m -x m y m z m It should be 0 in the coordinate system, that is

[0106]

[0107] By iteratively solving the above nonlinear equations using numerical calculation methods, the longitudinal rotation angle α and the lateral rotation angle β caused by the compression can be obtained.

[0108] 3. Calculation of coordinates of center of gravity and landing gear touchdown point after offset

[0109] After the offset, the center of gravity and the landing gear touchdown point are in the initial body coordinate system O. o -x o y o z o The coordinates below are calculated using the following formula:

[0110] Coord G new =T(Coord) G -Coord fuzu_d )+Coord fuzu_d

[0111] Coord left new =T(Coord) left_d -Coord fuzu_d )+Coord fuzu_d

[0112] Coord right new =T(Coord) right_d -Coord fuzu_d )+Coord fuzu_d

[0113] Coord fuzu new =Coord fuzu_d

[0114] 4-coordinate iterative update

[0115] Because the initial coordinates were used when calculating the landing gear support reactions, the calculation results were somewhat biased. To make the results as accurate as possible, the initial coordinates were replaced with offset coordinates and updated iteratively.

[0116] 5. Calculation of stabilizing moment

[0117] z provides a stabilizing torque to the inertial overload, as shown in the diagram below. Figure 2 As shown.

[0118] The stabilizing moment is calculated as follows:

[0119] M s =n z Mg×d xy

[0120] In the formula, n z Let M be the inertial overload in the z-direction, and d be the mass of the helicopter. xy The horizontal distance from the center of gravity to the tilt axis is calculated using the following formula:

[0121]

[0122] In the formula, x z y z Let x be the coordinate of the main landing gear in the overturning direction. f y f To assist in the landing gear coordinates, x G y G These are the coordinates of the center of gravity. When tilting to the left, use the coordinates of the left main landing gear; when tilting to the right, use the coordinates of the right main landing gear.

[0123] 6. Calculation of overturning moment

[0124] When a helicopter tilts, it tilts along the line connecting the main landing gear touchdown point and the tail landing gear touchdown point, as shown below. Figure 6 As shown, the tilt axis is as follows Figures 1a-1c As shown. The left tilt axis ql is the line connecting the left main engine wheel and the tail wheel, and the right tilt axis qr is the line connecting the right main engine wheel and the tail wheel.

[0125] When a helicopter is in a critical overturning state, the loads it experiences include: the reaction force of one main landing gear, the reaction force of the tail landing gear, inertial overload at the center of gravity, and wind load. Among these, the z-axis inertial overload provides a stabilizing torque M. s xy provides overturning moment M to inertial overload and wind load. o .

[0126] xy provides overturning moments for inertial overload and wind load, as illustrated in the diagram of the overturning force. Figure 3 As shown.

[0127] When tilting to the right, the overturning moment is calculated as follows:

[0128] M o =(n xy Mg+F wind_xy )×d h +F wind_z ×d xy -M windq

[0129] When tilting to the left, the overturning moment is calculated as follows:

[0130] M o =-(n xy Mg+F wind_xy )×d h +F wind_z ×dxy +M windq

[0131] In the formula, n xy For horizontal overload perpendicular to the tilt axis, F windxy For the horizontal wind load perpendicular to the tilt axis, d h M is the height of the center of gravity. windq This represents the component of the wind load moment about the tilt axis.

[0132]

[0133] When tilting to the right, n xy F wind_xy M windq The load synthesis diagram is shown below, calculated using the following formula. Figures 4a-4b :

[0134] n xy =n x sinθ+n y cosθ;

[0135] F wind_xy =F wind_x sinθ+F wind_y cosθ;

[0136] M windq =M x cosθ-M y sinθ.

[0137] When tilting to the left, n xy F wind_xy M windq The load synthesis diagram is shown below, calculated using the following formula. Figures 5a-5b :

[0138] n xy =-n x sinθ+n y cosθ;

[0139] F wind_xy =-F wind_x sinθ+F wind_y cosθ;

[0140] M windq =M x cosθ+M y sinθ.

[0141] 7. Calculation of stabilizing moment

[0142] z provides a stabilizing torque to the inertial overload, as shown in the diagram below. Figure 2 As shown.

[0143] The stabilizing moment is calculated as follows:

[0144] M s =n z Mg×d xy

[0145] In the formula, n z Let M be the inertial overload in the z-direction, and d be the mass of the helicopter. xy The horizontal distance from the center of gravity to the tilt axis is calculated using the following formula:

[0146]

[0147] In the formula, x z y z Let x be the coordinate of the main wheel in the overturning direction. f y f Let x be the coordinate of the tail wheel. G y G These are the coordinates of the center of gravity. When tilting to the left, use the coordinates of the left main engine wheel; when tilting to the right, use the coordinates of the right main engine wheel.

[0148] 8. Assessment of overturning stability

[0149] When the steady torque M s Less than the overturning moment M o At that moment, the helicopter overturned.

[0150] Define the ratio M of the stabilizing moment to the overturning moment. s / M o The absolute value is the stability coefficient C. q When C q When C > 1, the helicopter does not capsize. q When the time is less than 1, the helicopter overturns.

[0151] The above description is merely a specific embodiment of the present invention, providing a detailed description of the invention. Parts not covered herein are conventional techniques. However, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for calculating the rollover stability of a helicopter on a ship considering landing gear compression, characterized in that, include: Considering the ship's rolling motion and wind load factors affecting the helicopter, determine the changes in the compression on both sides of the helicopter landing gear after being affected by the above factors. Based on the changes in compression on both sides, calculate the new center of gravity coordinates of the helicopter after being affected by the landing gear; Calculate the stabilizing moment and overturning moment of the helicopter based on the new center of gravity coordinates; By comparing the stabilizing moment and the overturning moment, it can be determined whether the helicopter has rolled over. To determine if a helicopter has rolled over to one side, the ship's rolling motion and wind load factors are considered. The changes in compression on both sides of the helicopter landing gear after being affected by these factors are determined, including: For this iteration, based on the grounding point coordinates of the main landing gear and auxiliary landing gear on this side obtained in the previous iteration, the distances from the main landing gear to the auxiliary landing gear are calculated respectively. A force analysis was performed on the vertical loads borne by the main and auxiliary landing gear on the pressure side during the critical overturning state, and equilibrium equations based on the tilt axis on that side were established. The equilibrium equations are as follows: ； in, The vertical net force acting on the helicopter. Let p be the torque of the helicopter about the p-axis, which is perpendicular to the tilt axis; To assist the vertical support reaction force of the landing gear, The vertical support reaction force of the main landing gear; Let be the torque of the wind load about the p-axis. For vertical inertial overload, This is the distance from the main landing gear to the auxiliary landing gear on that side. The horizontal distance from the center of gravity to the p-axis. For the vertical component of wind load, The height of the center of gravity; The horizontal overload is perpendicular to the p-axis and points towards the p-axis; the tilt axis is the line connecting the main landing gear touchdown point and the auxiliary landing gear touchdown point on this side; M is the mass of the helicopter, and g is the acceleration due to gravity. Based on the above equilibrium equations, solve for the vertical support reaction force of the auxiliary landing gear and the vertical support reaction force of the main landing gear on this side; Using the known static pressure curves of the landing gear buffer strut and tires on that side, the compression of the main landing gear and auxiliary landing gear on that side is calculated, thereby calculating the new center of gravity coordinates of the helicopter and the new touchdown coordinates of each landing gear. Calculating the new center of gravity coordinates of the helicopter includes: When one main landing gear is compressed, the helicopter deflects. With the auxiliary landing gear contact point as the center of rotation, let the longitudinal deflection angle be α and the lateral deflection angle be β. Based on the compression of the main landing gear and auxiliary landing gear on that side, calculate the coordinates of the touchdown points of each landing gear before deflection in the ship's coordinate system. Calculate α and β, assuming that the vertical coordinates of the touchdown points of the two front landing gears are 0 after deflection in the ship's coordinate system. Based on α, β, the original center of gravity coordinates, and the touchdown point coordinates of the main and auxiliary landing gears obtained in the previous iteration, the new center of gravity coordinates after deflection are calculated. Calculate α and β, including: Substituting the above conditions and the coordinates of the touchdown points of each landing gear before deflection in the ship's coordinate system into the following formula, we obtain α and β, as shown in the following formula: ； ； ； The coordinates of the touchdown point of the left landing gear before deflection; These are the coordinates of the touchdown point of the left landing gear after deflection; This is the transformation matrix; The coordinates of the touchdown point of the right landing gear before deflection; These are the coordinates of the touchdown point of the right landing gear after deflection; The formulas for calculating the new coordinates of the center of gravity and the new coordinates of the touchdown points of each landing gear after deflection are as follows: ； ； ； ； in, For the new center of gravity coordinates, The new coordinates for the touchdown point of the left landing gear. The new coordinates for the touchdown point of the right landing gear. To assist in determining the new coordinates of the landing gear's touchdown point, , , These are the coordinates of the grounding points of the left, right, and auxiliary landing gear obtained from the previous iteration.

2. The method according to claim 1, characterized in that, After calculating the new coordinates of the helicopter's center of gravity and the new coordinates of the touchdown points of each landing gear, the method further includes: The iteration stops when the difference between the new centroid coordinates and the original centroid coordinates is less than a preset threshold.

3. The method according to claim 1, characterized in that, Regarding the judgment of left-leaning ； ； ； in, , To assist in the landing gear coordinates, , The coordinates of the left landing gear are... For longitudinal overload of helicopter, For helicopter lateral overload, For longitudinal wind load, This refers to lateral wind load.

4. The method according to claim 3, characterized in that, Regarding the judgment of right-leaning ； ； 。

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