A helicopter flight performance optimization method based on active twist rotor

Abstract

The application discloses a helicopter flight performance optimization method based on active twist rotors, and relates to the technical field of helicopter performance optimization. The method comprises the following steps: obtaining a flight performance index of a target helicopter; and performing parameter optimization on the target helicopter by using a coordinate circulation method and the flight performance index, so as to obtain an active twist control scheme when the flight performance index is maximized. The coordinate circulation method is constructed according to a rotor flight performance calculation module and a rotor aeroelastic response coupling analysis framework. The rotor flight performance calculation module is used for calculating a target flight performance parameter. The rotor aeroelastic response coupling analysis framework comprises a first-stage calculation module and a second-stage calculation module which are connected in sequence. The first-stage calculation module is used for calculating rigid blade structure response. The second-stage calculation module is used for calculating elastic blade structure response. The helicopter active twist control scheme when the flight performance index is maximized can be obtained.

Description

Technical Field

[0001] This invention relates to the field of helicopter performance optimization technology, and in particular to a method for optimizing helicopter flight performance based on an active twist rotor. Background Technology

[0002] Helicopters, due to their flexible flight capabilities, have been active in various air transport fields since their invention. However, the high-speed rotation of the rotor that provides lift for helicopters, especially in forward flight, results in the rotor blades being constantly exposed to a periodically changing incoming flow velocity environment. Combined with the trim pitch control required for flight and the blade motion and deformation response, the blade profiles at different spanwise positions experience oscillating aerodynamic load states, which limits the improvement of various flight performance aspects of helicopters.

[0003] To address the limitations on improving helicopter flight performance, active control rotor technology has gradually emerged with the development of smart materials and structural technologies. Among them, active torsional rotor technology employs a scheme of continuous active torsional deformation of the blades, actively changing the torsion angle distribution along the blade spanwise to improve the control effect of rotor aerodynamic load distribution, ultimately enhancing helicopter flight performance.

[0004] However, the following shortcomings still exist in active twist rotor technology: a lack of efficient design and analysis methods for rotor aeroelastic loads in optimizing active twist rotor control schemes; and a lack of analytical methods to study the impact of active twist control on rotor aerodynamic performance and aerodynamic loads. Due to the lack of these two types of aeroelastic analysis, it is currently impossible to obtain an active twist control scheme for helicopters that maximizes flight performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for optimizing helicopter flight performance based on an active twist rotor, which can obtain an active twist control scheme for maximizing the helicopter's flight performance indicators.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A method for optimizing helicopter flight performance based on an active twisting rotor includes:

[0008] Obtain the flight performance indicators of the target helicopter; the flight performance indicators include helicopter parameters, rotor blade parameters, engine parameters, and active control parameters;

[0009] Using the coordinate cyclic method and the flight performance indicators, the parameters of the target helicopter are optimized to obtain an active torque control scheme that maximizes the flight performance indicators; the active torque control scheme includes the target flight performance parameters after optimization calculation of each of the optimized parameters;

[0010] The coordinate cyclic method is constructed based on the rotor flight performance calculation module; the rotor flight performance calculation module is constructed based on the rotor aeroelastic response coupling analysis framework; the rotor flight performance calculation module is used to calculate the target flight performance parameters; the rotor aeroelastic response coupling analysis framework includes a first-level calculation module and a second-level calculation module connected in sequence; the first-level calculation module is used to calculate the rigid blade structure response; the second-level calculation module is used to calculate the elastic blade structure response; the rigid blade structure response and the elastic blade structure response are used to calculate the rotor steady-state aeroelastic response under the control of the target flight performance parameters.

[0011] Optionally, the helicopter parameters include: rotor radius, blade width, flapping hinge extension, effective aerodynamic position spanwise starting point of the blades, number of blades, angular velocity, and helicopter cabin drag coefficient;

[0012] The blade parameters include: blade structural data and blade aerodynamic data; the blade structural data includes blade axial tensile stiffness, moment of inertia in flapping and flaring directions, torsional stiffness constant, shear modulus of blade beam, polar moment of inertia of blade beam section, and blade pre-torsion angle distribution data; the blade aerodynamic data includes blade airfoil distribution and lift-drag characteristic curve data of each airfoil.

[0013] The engine parameters include: power transfer coefficient characteristic curve data of the engine at different altitudes and different advance ratios; the active control parameters include: active control rate amplitude limit data.

[0014] Optionally, the step of optimizing the parameters of the target helicopter using the coordinate cyclic method and the flight performance indicators to obtain an active torsion control scheme that maximizes the flight performance indicators specifically includes:

[0015] Set basic cycle parameters; the basic cycle parameters include: using the harmonic component coefficient of the active torsional rate as the optimization variable, and setting the highest order to 5;

[0016] Based on the basic loop parameters, the optimization variables are changed sequentially to obtain the updated optimization variables for the current order;

[0017] Based on the updated and optimized variables of the current order and the rotor flight performance calculation module, the flight performance index of the target helicopter under active twist control is calculated to obtain the target flight performance parameters of the current order.

[0018] The calculation stops when the value of the updated optimization variable in the current order remains unchanged from the value in the previous order, or when the optimization order exceeds the highest order. The active torsional control scheme that maximizes the flight performance index is then determined based on the target flight performance parameters of the current order.

[0019] Optionally, based on the updated and optimized variables of the current order and the rotor flight performance calculation module, the flight performance index of the target helicopter under active twist control is calculated to obtain the target flight performance parameters of the current order, specifically including:

[0020] The flight conditions are input into the rotor aeroelastic response coupling analysis framework for calculation, and rotor trim calculation is performed to obtain the required power of the rotor under the flight conditions; the flight conditions are the flight conditions of the target helicopter at the midpoint between the upper and lower limits of the set flight performance.

[0021] The available power of the rotor is calculated based on the engine parameters in the flight performance indicators. The remaining power of the helicopter is obtained by subtracting the required power from the available power. The upper and lower limits of the set flight performance are adjusted based on the remaining power of the helicopter. The process returns to the step "inputting the flight conditions into the rotor aeroelastic response coupling analysis framework for calculation and performing rotor trim calculation to obtain the required power of the rotor under the flight conditions".

[0022] When the absolute value of the helicopter's remaining power is less than the set convergence threshold or the number of iterations exceeds the set number of iterations, the calculation of flight performance indicators is stopped, and the target flight performance parameters for the current order are obtained.

[0023] Optionally, the flight conditions are input into the rotor aeroelastic response coupling analysis framework for calculation, and rotor trim calculation is performed to obtain the required power of the rotor under the flight conditions, specifically including:

[0024] The flight conditions are sequentially input into the first-level calculation module and the second-level calculation module to perform time-domain integration of the second aeroelastic response, and the rotor trim is calculated using the six-degree-of-freedom equilibrium equations under steady straight flight of the helicopter to obtain the required power of the rotor under the stated flight conditions.

[0025] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] This invention discloses a method for optimizing helicopter flight performance based on an active twist rotor. The method includes obtaining the flight performance indicators of a target helicopter; optimizing the parameters of the target helicopter using a coordinate cyclic method and the flight performance indicators to obtain an active twist control scheme that maximizes the flight performance indicators; wherein the coordinate cyclic method is constructed based on a rotor flight performance calculation module and a rotor aeroelastic response coupling analysis framework; the rotor flight performance calculation module is used to calculate the target flight performance parameters; the rotor aeroelastic response coupling analysis framework includes a first-level calculation module and a second-level calculation module connected in sequence; the first-level calculation module is used to calculate the rigid blade structure response; the second-level calculation module is used to calculate the elastic blade structure response. This invention can obtain an active twist control scheme for helicopters that maximizes their flight performance indicators. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart illustrating the helicopter flight performance optimization method of the present invention;

[0029] Figure 2 This is a logical schematic diagram of the rotor flight performance calculation module in this embodiment;

[0030] Figure 3 This is a logical schematic diagram of the rotor aeroelastic response coupling analysis framework in this embodiment;

[0031] Figure 4 This is a logical diagram of the first-level computing module and the second-level computing module in this embodiment. Detailed Implementation

[0032] 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The purpose of this invention is to provide a method for optimizing helicopter flight performance based on an active twist rotor, which can obtain an active twist control scheme for maximizing the helicopter's flight performance indicators.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, this invention provides a method for optimizing helicopter flight performance based on an active twist rotor, comprising:

[0036] S100: Obtain the flight performance indicators of the target helicopter; the flight performance indicators include helicopter parameters, rotor blade parameters, engine parameters, and active control parameters.

[0037] S200: Using the coordinate cyclic method and the flight performance index, the parameters of the target helicopter are optimized to obtain an active torque control scheme that maximizes the flight performance index; the active torque control scheme includes the target flight performance parameters after optimization calculation of each of the optimized parameters.

[0038] The coordinate cyclic method is constructed based on the rotor flight performance calculation module; the rotor flight performance calculation module is constructed based on the rotor aeroelastic response coupling analysis framework; the rotor flight performance calculation module is used to calculate the target flight performance parameters; the rotor aeroelastic response coupling analysis framework includes a first-level calculation module and a second-level calculation module connected in sequence; the first-level calculation module is used to calculate the rigid blade structure response; the second-level calculation module is used to calculate the elastic blade structure response; the rigid blade structure response and the elastic blade structure response are used to calculate the rotor steady-state aeroelastic response under the control of the target flight performance parameters.

[0039] In this embodiment, the helicopter parameters include: rotor radius, blade width, flapping hinge overhang, effective aerodynamic position spanwise starting point of the blade, number of blades, angular velocity, and helicopter cabin drag coefficient; the blade parameters include: blade structural data and blade aerodynamic data; the blade structural data includes blade axial tensile stiffness, moment of inertia in flapping and flaring directions, torsional stiffness constant, shear modulus of the blade beam, polar moment of inertia of the blade beam section, and blade pre-torsion angle distribution data; the blade aerodynamic data includes blade airfoil distribution and lift-drag characteristic curve data for each airfoil; the engine parameters include: power transfer coefficient characteristic curve data of the engine at different altitudes and different advance ratios; the active control parameters include: active control rate amplitude limit data.

[0040] One specific implementation scheme of S200 includes:

[0041] S210: Set the basic cycle parameters; the basic cycle parameters include: using the harmonic component coefficient of the active torsional rate as the optimization variable, and setting the highest order to 5.

[0042] S220: Based on the basic loop parameters, the optimization variables are changed sequentially to obtain the updated optimization variables for the current order.

[0043] S230: Based on the updated and optimized variables of the current order and the rotor flight performance calculation module, calculate the flight performance index of the target helicopter under active twist control to obtain the target flight performance parameters of the current order.

[0044] S240: When the value of the updated optimization variable of the current order is unchanged from the value of the previous order, or when the optimization order exceeds the highest order, the calculation is stopped, and an active torsional control scheme for maximizing the flight performance index is determined based on the target flight performance parameters of the current order.

[0045] As a specific implementation of S230, it specifically includes:

[0046] S231: Input the flight conditions into the rotor aeroelastic response coupling analysis framework for calculation, and perform rotor trim calculation to obtain the required power of the rotor under the flight conditions; the flight conditions are the flight conditions of the target helicopter at the midpoint between the upper and lower bounds of the set flight performance; specifically including:

[0047] The flight conditions are sequentially input into the first-level calculation module and the second-level calculation module to perform time-domain integration of the second aeroelastic response, and the rotor trim is calculated using the six-degree-of-freedom equilibrium equations under steady straight flight of the helicopter to obtain the required power of the rotor under the stated flight conditions.

[0048] S232: Calculate the available power of the rotor based on the engine parameters in the flight performance index, subtract the required power from the available power to obtain the remaining power of the helicopter, adjust the upper and lower limits of the set flight performance based on the remaining power of the helicopter, and return to step S231.

[0049] S233: When the absolute value of the helicopter's remaining power is less than the set convergence threshold or the number of iterations is greater than the set number of iterations, stop the calculation of flight performance indicators and obtain the target flight performance parameters for the current order.

[0050] Based on the above technical solution, the following embodiments are provided.

[0051] The process of optimizing flight performance indicators using the coordinate cyclic method, such as... Figure 2 As shown. First, set the harmonic component coefficients A0 and A1 of the active torsional rate. ic A is As optimization variables, the highest order i is taken as 5, and the active twist rate and active twist angle of the blade are expressed as follows:

[0052]

[0053]

[0054] in, This indicates that the blade is at a direction angle of... Active torsional rate at time, in ° / m; The value represents the magnitude of the active twist angle of the blade at the center x, in degrees; x represents the spanwise coordinate of the blade profile, in meters; i represents the harmonic order; A0, A ic A is The variable is a dimensionless optimization variable.

[0055] The coordinate cyclic method modifies only one optimization variable at a time, calling the rotor flight performance calculation module to calculate until the optimization variable maximizes the target flight performance result. Then, it calculates the optimal value for the next optimization variable. After all variables have undergone one round of optimization, the next round of optimization begins from the first optimization variable, and the calculation stops when the value of the optimization variable remains unchanged from the previous round or the number of optimization rounds exceeds the user-defined upper limit. This yields the active torsional optimization control law for the target flight performance.

[0056] The aforementioned rotor flight performance calculation module, such as Figure 3 As shown, firstly, the upper and lower bounds of the helicopter's target flight performance are set. The flight condition at the midpoint is input into the rotor aeroelastic response coupling analysis framework for calculation, and rotor trim calculation is performed to obtain the rotor's required power under this flight condition. Then, based on the engine's altitude characteristic curve and power transfer coefficient, the rotor's available power is obtained. The remaining power of the helicopter is obtained by subtracting the required power from the available power. If the remaining power is greater than 0, the lower bound is raised to the midpoint value; if it is less than 0, the upper bound is lowered to the midpoint value. The calculation is then repeated from step one. The calculation stops when the absolute value of the remaining power is less than the user-set convergence threshold or the number of calculations exceeds the user-set number. The flight condition at this point represents the target flight performance parameters.

[0057] The above-mentioned rotor aeroelastic response coupling analysis framework, such as Figure 4 As shown, firstly, the blade is assumed to be a rigid beam retaining only the degrees of freedom of yaw and flapping. The rotor dynamics model is simplified to retain only the first-order yaw and first-order flapping modes, resulting in a simplified dynamics model of the rigid blade assumption, containing only two degrees of freedom: flapping angle β and yaw angle ξ. Then, the aeroelastic response time-domain integral is performed until the calculation results converge. The time-domain integral equation is as follows:

[0058]

[0059]

[0060]

[0061]

[0062] Where q is the vector of calculated degrees of freedom; M, C, K and F are the mass matrix, damping matrix, stiffness matrix and load vector of the blade dynamics equation, respectively; γ and β are integration parameters. When γ = 0.5 and β = 0.25, the average acceleration method is used, which has good numerical stability; h is the time-domain integration step size; and S is the predicted mass matrix.

[0063] The convergence determination of time-domain integral calculation is to calculate the difference in the elastic displacement response of the blades within the rotation cycle of two adjacent blades. If the difference is lower than the set residual convergence threshold, the response is determined to have converged to the steady-state periodic response.

[0064] Then, the aeroelastic response calculation results of the rigid blade dynamics model are used as the initial values ​​for the elastic blade dynamics model. A second time-domain integration of the aeroelastic response is performed to obtain the rotor's steady-state aeroelastic response and output the required power of the blade. This two-stage analysis method can effectively improve computational efficiency and make the calculation easier to converge.

[0065] The rotor trim calculations described above utilize the six-degree-of-freedom equilibrium equations for steady linear flight of a helicopter.

[0066]

[0067] Among them, F D F LAT With F T Respectively, the rotor's rearward force, lateral force, and thrust; M X0 M Y0 With M Z0 These are the rotor roll moment, pitch moment, and torque, respectively; W G For gravity; F Tail For tail rotor thrust; D fuse For fuselage drag; α s With Φ s These are the main shaft tilt angle and main shaft sideslip angle of the rotor shaft, respectively; X CG With Z CG These are the coordinates of the fuselage gravity and drag points in the fixed coordinate system of the propeller hub; X Tail The tail rotor coordinates are given in the fixed coordinate system of the rotor hub.

[0068] The six-component load mean of the rotor is obtained using a coupled aeroelastic response analysis framework. To simplify the calculation, it is assumed that the tail rotor thrust can balance the helicopter's yaw moment, reducing the trim equation to five degrees of freedom. The trim variables are the collective pitch angle θ0 and the longitudinal periodic pitch angle θ. 1s Lateral periodic pitch angle θ 1c α, spindle tilt angles and spindle tilt angle Φ s :

[0069] Using Newton's iterative method, the fifth-order control derivative matrix of the rotor's five-degree-of-freedom forces and moments with respect to the five trim variables is first obtained using the rotor aeroelastic response coupling analysis framework under a specific control input, and the inverse matrix is ​​then calculated. Subsequently, in the trim calculation, initial values ​​for the trim variables are set, and the resultant force vector of the five degrees of freedom is solved using the rotor aeroelastic response coupling analysis framework. The trim correction is then solved using the inverse matrix of the control derivatives. The corrected trim vector is input into the rotor aeroelastic response coupling analysis framework for recalculation. This process is repeated until the five-degree-of-freedom force vector falls below a set threshold, at which point the loop exits. This yields the rotor aeroelastic response after trim calculation and the required power.

[0070] This embodiment proposes a helicopter flight performance optimization method based on active rotor twist. It can calculate the active twist control scheme that maximizes the flight performance index based on given helicopter parameters through a rotor aeroelasticity calculation framework, and output the optimized performance improvement result.

[0071] The following beneficial effects exist: (1) It can realize the active torsion control optimization design for different flight performance indicators; (2) It establishes an efficient analysis method for the time-domain nonlinear aeroelastic steady-state periodic response suitable for active torsion rotors. A nonlinear aeroelastic dynamic model of active torsion rotor is established, and combined with a simplified dynamic model of rigid blade, a two-level efficient analysis method for aeroelastic steady-state periodic response is formed, which solves the problem that traditional time-domain aeroelastic response analysis methods cannot balance computational accuracy and efficiency, and meets the needs of active torsion rotor control scheme optimization design research. (3) It can output the aerodynamic load and displacement response distribution of the blade in the rotor disk plane, which can be used for subsequent research.

[0072] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0073] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for optimizing helicopter flight performance based on an active twisting rotor, characterized in that, include: Obtain the flight performance indicators of the target helicopter; the flight performance indicators include helicopter parameters, rotor blade parameters, engine parameters, and active control parameters; Using the coordinate cyclic method and the flight performance index, the parameters of the target helicopter are optimized to obtain an active torque control scheme that maximizes the flight performance index; the active torque control scheme includes the target flight performance parameters after optimization calculation of each optimized parameter; The coordinate cyclic method is executed using a rotor flight performance calculation module. This module is constructed based on a rotor aeroelastic response coupling analysis framework. The rotor flight performance calculation module is used to calculate target flight performance parameters. The rotor aeroelastic response coupling analysis framework includes a first-level calculation module and a second-level calculation module connected sequentially. The first-level calculation module is used to calculate the rigid blade structure response. The second-level calculation module is used to calculate the elastic blade structure response. The rigid blade structure response and the elastic blade structure response are used to calculate the rotor steady-state aeroelastic response under the control of the target flight performance parameters. The step of optimizing the parameters of the target helicopter using the coordinate cyclic method and the flight performance indicators to obtain an active torsion control scheme that maximizes the flight performance indicators specifically includes: Set basic cycle parameters; the basic cycle parameters include: using the harmonic component coefficient of the active torsional rate as the optimization variable, and setting the highest order to 5; Based on the basic loop parameters, the optimization variables are changed sequentially to obtain the updated optimization variables for the current order; Based on the updated and optimized variables of the current order and the rotor flight performance calculation module, the flight performance index of the target helicopter under active twist control is calculated to obtain the target flight performance parameters of the current order. The calculation stops when the value of the updated optimization variable in the current order remains unchanged from the value in the previous order, or when the optimization order exceeds the highest order. The active torsional control scheme that maximizes the flight performance index is then determined based on the target flight performance parameters of the current order.

2. The helicopter flight performance optimization method based on an active twisting rotor according to claim 1, characterized in that, The helicopter parameters include: rotor radius, blade width, flapping hinge extension, effective aerodynamic position spanwise starting point of the blades, number of blades, angular velocity, and helicopter cabin drag coefficient. The blade parameters include: blade structural data and blade aerodynamic data; the blade structural data includes blade axial tensile stiffness, moment of inertia in flapping and flaring directions, torsional stiffness constant, shear modulus of blade beam, polar moment of inertia of blade beam section, and blade pre-torsion angle distribution data; the blade aerodynamic data includes blade airfoil distribution and lift-drag characteristic curve data of each airfoil. The engine parameters include: power transfer coefficient characteristic curve data of the engine at different altitudes and different advance ratios; the active control parameters include: active control rate amplitude limit data.

3. The helicopter flight performance optimization method based on an active twisting rotor according to claim 1, characterized in that, Based on the updated and optimized variables of the current order and the rotor flight performance calculation module, the flight performance index of the target helicopter under active twist control is calculated to obtain the target flight performance parameters of the current order, specifically including: The flight conditions are input into the rotor aeroelastic response coupling analysis framework for calculation, and rotor trim calculation is performed to obtain the required power of the rotor under the flight conditions; the flight conditions are the flight conditions of the target helicopter at the midpoint between the upper and lower limits of the set flight performance. The available power of the rotor is calculated based on the engine parameters in the flight performance indicators. The remaining power of the helicopter is obtained by subtracting the required power from the available power. The upper and lower limits of the set flight performance are adjusted based on the remaining power of the helicopter. The process returns to the step "input the flight conditions into the rotor aeroelastic response coupling analysis framework for calculation and perform rotor trim calculation to obtain the required power of the rotor under the flight conditions". When the absolute value of the helicopter's remaining power is less than the set convergence threshold or the number of iterations exceeds the set number of iterations, the calculation of flight performance indicators is stopped, and the target flight performance parameters for the current order are obtained.

4. The helicopter flight performance optimization method based on an active twisting rotor according to claim 3, characterized in that, The flight conditions are input into the rotor aeroelastic response coupling analysis framework for calculation, and rotor trim calculation is performed to obtain the required power of the rotor under the stated flight conditions, specifically including: The flight conditions are sequentially input into the first-level calculation module and the second-level calculation module to perform time-domain integration of the second aeroelastic response, and the rotor trim is calculated using the six-degree-of-freedom equilibrium equations under steady straight flight of the helicopter to obtain the required power of the rotor under the stated flight conditions.

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