A calculation method for the hydraulic flow demand of a flight control system based on flight quality requirements

Abstract

The present invention relates to the technical field of hydraulic flow demand calculation for flight control systems, and discloses a method for calculating the hydraulic flow demand of a flight control system based on flight quality requirements. This method selects flight qualities related to hydraulic flow, constructs a target aircraft model, gives the transfer function of the target aircraft according to the equivalent fitting formulas of short-period pitch angle rate and normal overload, and based on the inverse function from the aircraft body to the aircraft response parameters, inversely solves the rudder surface commands required to achieve these response parameters. According to the rate limit of the rudder surface actuator model, it calculates the rate value required for the rudder surface and the power required for all rudder surface actuators of the flight control system to move simultaneously, conducts an analysis of the combined rudder surface movement based on actual flight tests, analyzes the division of flight phases and control actions during actual flight tests, and in combination with flight quality flight test items, selects the cases where the combined rudder surface conditions are relatively severe, calculates the final hydraulic flow demand of the hydraulic source, and provides a reference for the optimal design of the aircraft.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic flow demand calculation for flight control systems, and specifically to a method for calculating the hydraulic flow demand of a flight control system based on flight quality requirements. Background Art

[0002] Hydraulic energy is one of the important energies on an aircraft. The aircraft drives the actuators through the hydraulic system to achieve the required functions. The main users of the hydraulic system include the flight control system and the landing gear system. Among them, the flight control system drives the control surfaces through hydraulic energy.

[0003] When designing the hydraulic system, it is necessary to calculate the required hydraulic power or flow according to the power or flow demand of the user, and determine the rated flow of the hydraulic pump of the hydraulic system according to the working state of the engine. Therefore, the flight control system, as the main user, can put forward accurate hydraulic flow demand, which is the key input for the hydraulic system to complete the design. If the required flow rate proposed by the flight control system is too large, it will lead to an increase in the weight, volume, etc. of the hydraulic system, and ultimately reduce the effective payload of the aircraft. If the required flow rate is too small, it cannot meet the movement requirements of the control surfaces, thus affecting the normal operation of the aircraft. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] Aiming at the deficiencies of the prior art, the present invention provides a method for calculating the hydraulic flow demand of a flight control system based on flight quality requirements. It has the ability to select flight qualities related to hydraulic flow, construct a target aircraft model according to the selected flight qualities, give the transfer function of the target aircraft according to the equivalent fitting formula of the short-period pitch angle rate and normal overload, and according to the inverse function from the aircraft body to the aircraft response parameters, inversely solve the control surface command required to achieve the response parameters. According to the rate limit of the control surface actuator model, calculate the required rate value of the control surface The power required for all control surface actuators of the flight control system to move simultaneously, compared with the control surface combination calculation method for all original control surfaces to move simultaneously, conducts an analysis of the control surface combination movement based on actual flight tests, analyzes the division of flight phases and control actions during actual flight tests, and combines flight quality flight test items to select situations where the control surface combination is relatively severe, including tight turns, decelerating turns, maximum roll and pitch combined maneuvers, coordinated sideslips, lateral and directional control under asymmetric thrust, and takeoffs and landings in strong crosswinds. Calculate the hydraulic flow demand based on the configuration of the control surface energy, including the hydraulic flow RT_Q required for the j-th control surface for the i-th hydraulic source i[j] The final hydraulic flow rate requirement of the i-th set of hydraulic sources is subjected to control system simulation analysis through a control model with hydraulic flow rate calculation to obtain the flow rate requirement at any time, verify the requirements put forward in the project demonstration stage and the preliminary design stage, provide reference for the optimal design of the aircraft. Through the above method, the flight control system can provide accurate hydraulic flow rate requirement input for the hydraulic system design, without wasting the flow rate of the hydraulic system on the premise of meeting the requirements of the flight control system, achieving the optimal overall design index of the aircraft and solving the above problems.

[0006] (II) Technical Solution

[0007] To achieve the above object, the present invention provides the following technical solution: A method for calculating the hydraulic flow rate requirement of a flight control system based on flight quality requirements, comprising the following steps:

[0008] S1. Select the flight quality related to the hydraulic flow rate;

[0009] Construct a target aircraft model according to the selected flight quality, and give the transfer function of the target aircraft according to the equivalent fitting formula of the short-period pitch angle rate and the normal overload in the longitudinal direction of the aircraft;

[0010] According to the inverse function from the aircraft body to the aircraft response parameter, inversely solve the rudder surface command required to achieve this response parameter;

[0011] Calculate the required motion rate value of the rudder surface according to the rate limit of the rudder surface actuator model And the power required for all the rudder surface actuators of the flight control system to move simultaneously;

[0012] S2. Compare with the rudder surface combination calculation method for all the original rudder surfaces moving simultaneously, conduct an analysis of the rudder surface combination movement based on actual flight tests, analyze the division of flight phases and control actions in actual flight tests, and combine with the flight quality flight test items to select the cases where the rudder surface combination is relatively severe, including tight turning, decelerating turning, maximum roll and pitch combination control, coordinated sideslip, lateral-directional control under asymmetric thrust, and takeoff and landing in strong crosswinds;

[0013] S3. Calculate the hydraulic flow rate requirement based on the configuration of the rudder surface energy source, including the hydraulic flow rate RT_Q required by the j-th rudder surface for the i-th set of hydraulic sources i [j] And the final hydraulic flow rate requirement of the i-th set of hydraulic sources;

[0014] S4. Through a control model with hydraulic flow rate calculation, conduct control system simulation analysis to obtain the flow rate requirement at any time, verify the requirements put forward in the project demonstration stage and the preliminary design stage, and provide reference for the optimal design of the aircraft.

[0015] Preferably, in S1, before selecting the flight quality related to the hydraulic flow rate, at a specified deflection speed, calculate the maximum power required to operate the control surface to overcome the hinge moment, and the formula is as follows:

[0016]

[0017] In the formula, N max represents the maximum power required for the movement of a certain control surface of the flight control system, K represents the coefficient of the working characteristics of different control surface actuators, and M max represents the maximum hinge moment of the control surface, represents the required movement rate of the control surface.

[0018] Preferably, in S1, for the short-period pitch rate criterion in the longitudinal direction of the aircraft, its flight quality response has the following characteristics:

[0019] (1) The effective delay time t1 is in the following range:

[0020] Level 1: t1 ≤ 0.12 s;

[0021] Level 2: t1 ≤ 0.17 s;

[0022] Level 3: t1 ≤ 0.21 s;

[0023] (2) The transient peak ratio Δω2 / Δω1 meets the following requirements:

[0024] Level 1: less than or equal to 0.3;

[0025] Level 2: less than or equal to 0.6;

[0026] Level 3: less than or equal to 0.85;

[0027] (3) The effective rise time Δt is in the following range:

[0028] ① Non-terminal flight phase:

[0029] Level 1: 29.6 / V T ≤ t1 ≤ 1645 / V T ;

[0030] Level 2: 10.5 / V T ≤ t1 ≤ 5263 / V T ;

[0031] ② Terminal flight phase:

[0032] Level 1: 29.6 / V T ≤ t1 ≤ 658 / V T ;

[0033] Level 2: 10.5 / V T≤t1≤2122 / V T ;

[0034] In the formula, V T represents the true airspeed.

[0035] Preferably, in the above S1, for the short-period normal overload criterion in the longitudinal direction of the aircraft, its flight quality response has the following characteristics:

[0036] For V 表 ≥1.5V 表机动 when, the rise time t yss to reach the overload value of 0.95*n r shall not exceed:

[0037] Level 1: 1.5 s;

[0038] Level 2: 2.0 s;

[0039] Level 3: 2.5 s;

[0040] For V 表机动 ≤V 表 ≤1.5V 表机动 when, the rise time t yss to reach the overload value of 0.95*n r shall not exceed:

[0041] Level 1: 2.0 s;

[0042] Level 2: 2.5 s;

[0043] Level 3: 3.0 s;

[0044] For V 表 ≥1.5V 表机动 when, the overload overshoot (n ymax -n yss ) / n yss shall not exceed:

[0045] Level 1: 10%;

[0046] Level 2: 20%;

[0047] Level 3: 30%;

[0048] The number of oscillations when the overload response decays to plus or minus 5%n yss shall not be greater than 3 times. In the formula, V 表 is the indicated airspeed; V 表机动 refers to the minimum indicated airspeed for the maneuvering flight of the aircraft, n yss is the steady-state overload, and n ymax is the maximum overload.

[0049] Preferably, in S1, a target aircraft model is constructed according to the selected flight quality, and the transfer function of the target aircraft is given according to the equivalent fitting formula of the short-period pitch angle rate and the normal overload, where the equivalent fitting formula is the Laplace transform formula, as shown below:

[0050]

[0051]

[0052] In the formula, s is the Laplace operator, represents the transfer function of the pitch angle rate with respect to the stick force or stick displacement, is the molecular proportionality coefficient of the pitch angle rate transfer function, τ ω is the equivalent delay time of the pitch angle rate, ε n1 is the short-period equivalent damping ratio, ω n1 is the short-period equivalent frequency; represents the transfer function of the normal overload with respect to the stick force or stick displacement, is the molecular proportionality coefficient of the normal overload transfer function, τ n is the overload equivalent delay time, Tθ represents the molecular time constant of the short period, and e is the base of the natural logarithm.

[0053] Preferably, in S1, according to the rate limit of the actuator model of the control surface, the required rate value of the control surface is calculated The calculation process is as follows:

[0054] Taking the response parameters of the longitudinal short-period pitch angle rate criterion and the normal overload criterion of the aircraft as inputs, according to the inverse function from the aircraft body to each response parameter, the control surface command δ required to achieve the pitch angle rate and the normal overload response parameters is inversely solved cmd ; Input the control surface command δ cmd into the actuator model with rate limit, and then simulate through the aircraft body model, output the response parameters of the pitch angle rate and the normal overload, and compare them with the response parameters of the longitudinal short-period pitch angle rate criterion and the normal overload criterion. If the flight quality meets the criterion requirements, further reduce the rate limit value until it does not meet the requirements. At this time, the rate limit value is the required motion rate value

[0055] Preferably, in S1, according to the rate limit of the actuator model of the control surface, the power required for all the control surface actuators of the flight control system to move simultaneously is calculated. The calculation formula is as follows:

[0056]

[0057] In the formula, N represents the power required for all the actuators of the flight control system, Nmax represents the maximum power required for the movement of a certain control surface of the flight control system represents the power loss coefficient

[0058] Preferably, according to different requirements of the flight mission, S2 clearly divides each stage of the flight test, including takeoff, climb, cruise, approach, landing, etc. Each stage will correspond to different control actions and control surface combination requirements, and each stage is quantitatively calibrated through speed, altitude, and attitude parameters

[0059] Preferably, in S3, the hydraulic flow demand is calculated based on the configuration of the control surface energy source, including the hydraulic flow RT_Q i [j] required by the j-th control surface for the i-th set of hydraulic sources. The calculation formula is as follows

[0060]

[0061] In the formula, RT_Q i [j] represents the hydraulic flow required by the j-th control surface for the i-th set of hydraulic sources represents the movement speed of the j-th control surface, SQ[j] represents the conversion coefficient from the control surface movement speed to the flow rate, which is calculated through the connecting rod length and piston area of the actuator, ST[j] represents the usage state of the j-th control surface for the i-th set of hydraulic sources, 0 means not in use, and 1 means in use

[0062] Preferably, in S3, the hydraulic flow demand is calculated based on the configuration of the control surface energy source. The calculation formula for the final hydraulic flow demand of the i-th set of hydraulic sources is as follows

[0063]

[0064] In the formula, H_Q i represents the final hydraulic flow demand of the i-th set of hydraulic sources, RT_Q i [j] represents the hydraulic flow required by the j-th control surface for the i-th set of hydraulic sources, and n represents the number of hydraulic sources

[0065] Compared with the prior art, the present invention provides a method for calculating the hydraulic flow demand of a flight control system based on flight quality requirements, and has the following beneficial effects

[0066] The present invention selects the flight quality related to the hydraulic flow, constructs the target aircraft model according to the selected flight quality, gives the transfer function of the target aircraft according to the equivalent fitting formula of the short-period pitch angle rate and the normal overload, and according to the inverse function from the aircraft body to the aircraft response parameters, inversely solves the control surface command required to achieve the response parameters, and calculates the required rate value of the control surface according to the rate limit of the control surface actuator model The power required for the simultaneous movement of all the control surface actuators of the flight control system is analyzed for the control surface combination movement based on actual flight tests, compared with the calculation method of the control surface combination for the simultaneous movement of all the original control surfaces. The flight phases and control actions during actual flight tests are analyzed, and combined with the flight quality flight test items, the cases with relatively strict control surface combinations are selected, including tight turns, decelerated turns, maximum roll and pitch combination controls, coordinated sideslips, lateral-directional controls under asymmetric thrust, and takeoffs and landings in strong crosswinds. The hydraulic flow requirements are calculated based on the configuration of the control surface energy sources, including the hydraulic flow RT_Q i [j] required by the j-th control surface for the i-th hydraulic source and the final hydraulic flow requirements for the i-th hydraulic source. Through the control model with hydraulic flow calculation, the control system simulation analysis is carried out to obtain the flow requirements at any time, verify the requirements proposed in the scheme demonstration stage and the preliminary design stage, and provide a reference for the optimal design of the aircraft. Through the above method, the flight control system can provide accurate hydraulic flow requirement inputs for the hydraulic system design, without wasting the flow of the hydraulic system under the premise of meeting the requirements of the flight control system, and achieve the optimal overall design index of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the method steps of the present invention;

[0068] Figure 2 It is a schematic diagram of the closed-loop control principle of the flight control system;

[0069] Figure 3 It is a schematic diagram of the evaluation parameters of the aircraft pitch angle rate response;

[0070] Figure 4 It is a schematic diagram of the evaluation parameters of the aircraft normal overload response;

[0071] Figure 5 It is a schematic diagram of the flight control system of the present invention with a control model for hydraulic flow calculation. DETAILED DESCRIPTION OF THE INVENTION

[0072] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.

[0073] An aircraft can complete flight only through the coordinated work of multiple systems. For example, the engine system provides power for the aircraft, the hydraulic system provides energy for the actuating components of the aircraft, and the flight control system controls the aircraft by manipulating the control surfaces, enabling the aircraft to move according to the pilot's manipulation intention, thereby completing various functions and performing various tasks.

[0074] The working principle of the flight control system is as follows Figure 2 As shown in the figure: The pilot issues a control command through the cockpit control device. After receiving the control command, the flight control computer calculates the control command for the control surface according to the control law and sends it to the actuator to complete the control of the aircraft control surface, change the aerodynamic force on the aircraft, so that the aircraft moves according to the pilot's control command. At the same time, the sensors on the aircraft feedback the motion parameters (angular rate, overload, etc.) of the aircraft to the flight control computer for closed-loop control of the flight control system.

[0075] The flight control system has always pursued complete control functions and optimal performance. As an actuator in the flight control system, from the perspective of the flight control system, it is hoped that the movement speed of the actuator is as large as possible, so that the control surface can be quickly deflected to the given command position, so that the motion parameters of the aircraft can quickly meet the requirements of the pilot. However, this poses higher requirements on the aircraft's energy and structural strength, because the movement of the control surface requires hydraulic energy to drive, and the movement of the control surface will also generate a hinge moment on the structure.

[0076] From the perspective of the hydraulic energy system, it is only necessary to provide the user with the required pressure and flow rate. The main users on the aircraft are the landing gear system and the flight control system. Among them, the landing gear system only works for a period of time during takeoff and landing, while the flight control system works throughout the entire process of aircraft takeoff, cruise, and landing, and the cruise flight time is much longer than the working time of takeoff and landing. Therefore, it can be said that the flight control system is the user with the most demand for it.

[0077] If the required flow rate for the flight control system is too large, it will lead to an increase in the weight, volume, etc. of the hydraulic system, and ultimately reduce the effective payload of the aircraft. If the required flow rate is too small, it cannot meet the movement requirements of the control surface, thus affecting the normal operation of the aircraft. For this reason, a calculation method for the hydraulic flow rate demand of the flight control system based on flight quality requirements is proposed. Please refer to Figure 1 which includes the following steps:

[0078] S1. (a) Select the flight quality related to the hydraulic flow rate;

[0079] When studying flight quality, the longitudinal and lateral / directional are usually separated. Here, taking the longitudinal direction as an example, the flight quality terms related to the hydraulic flow rate are introduced:

[0080] Using the equivalent fitting method, the longitudinal movement of the aircraft is divided into two modes: long period and short period. When studying flight quality, the short period mode is usually more concerned. The fitting forms of the short period pitch angular rate and normal overload are usually:

[0081]

[0082] In the formula, s is the Laplace operator, represents the transfer function of pitch rate with respect to stick force or stick displacement, is the proportional coefficient of the numerator of the pitch rate transfer function, τ ω is the equivalent delay time of pitch rate, ε n1 is the short-period equivalent damping ratio, ω n1 is the short-period equivalent frequency; represents the transfer function of normal overload with respect to stick force or stick displacement, is the proportional coefficient of the numerator of the normal overload transfer function, τ n is the overload equivalent delay time, T θ represents the molecular time constant of the short period, and e is the base of the natural logarithm.

[0083] As Figure 3 shown, it is a schematic diagram of the evaluation parameters of the aircraft pitch rate response. Taking the short-period pitch rate criterion in the longitudinal direction of the aircraft as an example, the following characteristics are required for its response in flight quality:

[0084] (1) The effective delay time t1 is within the following range:

[0085] Level 1: t1 ≤ 0.12 s;

[0086] Level 2: t1 ≤ 0.17 s;

[0087] Level 3: t1 ≤ 0.21 s;

[0088] (2) The transient peak ratio Δω2 / Δω1 meets the following requirements:

[0089] Level 1: less than or equal to 0.3;

[0090] Level 2: less than or equal to 0.6;

[0091] Level 3: less than or equal to 0.85;

[0092] (3) The effective rise time Δt is within the following range:

[0093] ① Non-terminal flight phase:

[0094] Level 1: 29.6 / V T ≤ t1 ≤ 1645 / V T ;

[0095] Level 2: 10.5 / V T ≤ t1 ≤ 5263 / V T ;

[0096] ② Terminal flight phase:

[0097] Level 1: 29.6 / VT ≤t1≤658 / V T ;

[0098] Level 2: 10.5 / V T ≤t1≤2122 / V T ;

[0099] In the formula, V T represents the true airspeed;

[0100] As Figure 4 shown, it is a schematic diagram of the aircraft normal overload response evaluation parameter. Taking the short-period normal overload criterion in the longitudinal direction of the aircraft as an example, the following characteristics are required for its response in flight quality:

[0101] For V 表 ≥1.5V 表机动 when, the rise time t yss to reach the overload value of 0.95*n r shall not exceed:

[0102] Level 1: 1.5 s;

[0103] Level 2: 2.0 s;

[0104] Level 3: 2.5 s;

[0105] For V 表机动 ≤V 表 ≤1.5V 表机动 when, the rise time t yss to reach the overload value of 0.95*n r shall not exceed:

[0106] Level 1: 2.0 s;

[0107] Level 2: 2.5 s;

[0108] Level 3: 3.0 s;

[0109] For V 表 ≥1.5V 表机动 when, the overload overshoot (n ymax -n yss ) / n yss shall not exceed:

[0110] Level 1: 10%;

[0111] Level 2: 20%;

[0112] Level 3: 30%;

[0113] The number of oscillations when the overload response decays to plus or minus 5%n yss shall not be greater than 3 times. In the formula, V 表 is the indicated airspeed; V 表机动Refers to the minimum indicated airspeed for the aircraft's maneuvering flight, n yss is the steady-state overload, n ymax is the maximum overload;

[0114] (b) Construct the target aircraft model according to the selected flight quality. According to the equivalent fitting formula of the short-period pitch rate and normal overload, give the transfer function of the target aircraft;

[0115] (c) According to the inverse function from the aircraft body to the aircraft response parameters, inversely solve the rudder surface command required to achieve the response parameters;

[0116] This step is mainly calculated according to the response characteristics of the aircraft body. Because the normal process is to give the rudder surface command, and through the movement of the aircraft body, the expected aircraft response is generated. Here, the required rudder surface command needs to be inversely calculated according to the aircraft body response;

[0117] (d) Calculate the required rate value of the rudder surface according to the rate limit of the rudder surface actuator model

[0118] and the power required for all rudder surface actuators of the flight control system to move simultaneously;

[0119] The calculation process of the required rate value of the rudder surface is as follows:

[0120] Taking the response parameters of the aircraft longitudinal short-period pitch rate criterion and normal overload criterion as inputs, according to the inverse function from the aircraft body to each response parameter, inversely solve the rudder surface command δ required to achieve the pitch rate and normal overload response parameters cmd ; Input the rudder surface command δ cmd into the actuator model with rate limit, and then simulate through the aircraft body model, output the pitch rate and normal overload response parameters, and compare them with the response parameters of the longitudinal short-period pitch rate criterion and normal overload criterion. If the flight quality meets the criterion requirements, further reduce the rate limit value until it does not meet the requirements. At this time, the rate limit value is the required motion rate value

[0121] The power calculation formula required for all rudder surface actuators of the flight control system to move simultaneously is as follows:

[0122]

[0123] By calculating the power required for all rudders to move simultaneously, it can be ensured that the components of the hydraulic system have sufficient capacity to meet the highest power demand, thus avoiding system overload and failure. In the formula, N represents the power required for all actuators of the flight control system, N max represents the maximum power required for a certain rudder surface movement of the flight control system, Denotes the power loss coefficient. This calculation helps engineers select appropriate hydraulic components during the design phase to ensure that the entire system can operate efficiently and reliably under different flight conditions, avoiding over-design or wasting resources.

[0124] S2. Based on the calculation method of the control surface combination that all the original control surfaces move simultaneously, conduct an analysis of the control surface combination movement based on actual flight tests, analyze the division of flight phases and control actions during actual flight tests, and select the cases with relatively strict control surface combinations in combination with the flight quality flight test items, including tight turns, decelerating turns, maximum roll and pitch combination maneuvers, coordinated sideslip, lateral-directional control under asymmetric thrust, and takeoff and landing in strong crosswinds.

[0125] An aircraft needs to operate different mechanisms in different flight phases to meet the task requirements of the current phase. Usually, a complete flight can be divided into the following flight phases: ground phase, before takeoff V1, after takeoff V1, acceleration climb phase, climb phase, cruise phase, mission phase, descent phase, approach phase, landing in the air phase, landing on the ground phase, etc.

[0126] (1) Ground phase: The ground stationary phase, during which engine warm-up, ground checks, etc. are carried out. During ground checks, the pilot will operate each control surface to check the integrity of the control surface operation. The aircraft taxis from the parking position to the runway end, and at this time, the landing gear will use the hydraulic system to complete ground braking and turning, etc.

[0127] (2) Before takeoff V1: From releasing the brakes, taking off and taxiing to the decision speed V1. At this time, the landing gear will use the hydraulic system to complete ground braking and turning, etc.

[0128] (3) After takeoff V1: From the taxiing decision speed V1 to the aircraft being pulled up to a safe altitude. At this time, control surfaces such as the elevator of the aircraft will move.

[0129] (4) Climb phase: Accelerate and climb from a safe altitude. During this period, the landing gear will be retracted, and the flap and slat lift augmentation devices will be retracted.

[0130] (5) Cruise phase: At this time, each control surface of the aircraft will move according to the control requirements to achieve the control of the aircraft's attitude, flight path, etc.

[0131] (6) Mission phase: In addition to using hydraulic energy to operate the control surfaces to complete attitude, flight path, etc. control, the mission system will also use hydraulic energy.

[0132] (7) Descent phase: From the end-of-cruise altitude to the approach altitude, each control surface cooperates to complete the establishment of the descent attitude and flight path control.

[0133] (8) Approach phase: From the approach altitude to the landing safe altitude. During this period, the landing gear will be lowered, and the flap and slat lift augmentation devices will be lowered.

[0134] (9) Landing in the air: From the landing safety altitude to the main landing gear wheels touching the ground;

[0135] (10) Landing on the ground: Decelerating from the main landing gear wheels touching the ground to a taxi stop. During this period, the spoilers are opened for deceleration, and the landing gear will use the hydraulic system to complete braking and turning on the ground, etc.;

[0136] By analyzing the use of control surfaces in different stages, it can be found that the combination stage with the most use of control surfaces is the cruise stage;

[0137] To check the characteristics of the aircraft such as initial response, time delay, short-period mode damping, frequency, etc., the pilot's control actions generally include: single-pulse control, double-pulse control, step control, sine sweep, decelerating turn, tight turn, loop, accelerating and decelerating flight, coordinated sideslip, landing in strong crosswind, etc. Taking some of the control actions as examples, their descriptions are given as follows:

[0138] (1) Single-pulse control, action essentials: Pulse control, the control amplitude gradually increases from 1 / 4, 1 / 2 to full stroke, and stabilizes for 3 - 7 s after the control is completed. The purpose is to check the aircraft's initial response and equivalent time delay, and also to check the short-period mode frequency and damping of the aircraft. This action is only carried out for single-axis control in the longitudinal, lateral, and heading directions each time;

[0139] (2) Sine sweep, action essentials: Perform equal-frequency or variable-frequency control on the control column. The pilot's control frequency is 0.5 - 1.5 Hz. The purpose is to measure the dynamic quality of the aircraft system, including the measurement of stability margin, and can also be used for parameter identification. This action is only carried out for single-axis control in the longitudinal, lateral, and heading directions each time;

[0140] (3) Tight turn, action essentials: Keep the Mach number unchanged, gradually push the control column to increase the roll angle, and pull the control column to the bottom to gradually increase the normal overload until the maximum overload and angle of attack. The purpose is to verify the maximum overload and angle of attack, check the control force gradient, and check the control coordination. This action involves combined control in the lateral and longitudinal directions;

[0141] (4) Coordinated sideslip, keep the altitude and speed unchanged, push the control column and step on the rudder to keep the aircraft heading unchanged. The purpose is to check the coordination of the aircraft in the longitudinal, lateral, and heading directions, check the steady-state sideslip quality and landing in crosswind. This action involves combined control of the three axes;

[0142] Finally, the pilot gives an evaluation of the satisfaction of the flight control system through flight quality flight tests, providing support for the aircraft type approval. Flight quality flight tests are also divided into three-axis flight tests in the longitudinal, lateral, and heading directions. Taking the longitudinal direction as an example, its flight test items include longitudinal static stability, the short-period response of the aircraft, and the control feel during maneuvering flight;

[0143] (1) Longitudinal static stability: Conduct flight tests through horizontal straight-line acceleration and deceleration actions;

[0144] (2) Short-period response of the aircraft: Conduct flight tests through single-pulse, double-pulse, or step control actions.

[0145] (3) Handling feel during maneuvering flight: There are various flight test methods for this item, and stable turns, decelerating turns, and convergent turns can be used.

[0146] After comprehensively considering the above flight phases, control actions, and flight quality flight test items, select the cases with relatively severe control surface combinations, including: tight turns, decelerating turns, maximum roll and pitch combined control, coordinated sideslip, lateral-directional control under asymmetric thrust, takeoff and landing in strong crosswinds, etc. After establishing the simulation model later, the combined motion of each control surface can be directly obtained by giving the input according to the selected control and outputting according to the control law.

[0147] S3. Calculate the hydraulic flow requirements based on the configuration of the control surface energy sources, including the hydraulic flow RT_Q i [j] required by the j-th control surface for the i-th hydraulic source and the final hydraulic flow requirements of the i-th hydraulic source.

[0148] The calculation formula for the hydraulic flow required by the j-th control surface for the i-th hydraulic source is as follows:

[0149]

[0150] By calculating the hydraulic flow required for specific control surfaces, it can ensure that the output of the hydraulic source matches the requirements of the control surfaces, so as to ensure that the control surfaces can respond quickly and accurately to control commands as expected. In the formula, RT_Q i [j] represents the hydraulic flow required by the j-th control surface for the i-th hydraulic source, represents the movement speed of the j-th control surface, SQ[j] represents the conversion coefficient from the control surface movement speed to the flow rate, which is calculated through the connecting rod length and piston area of the actuator, ST[j] represents the usage status of the j-th control surface for the i-th hydraulic source, 0 means not in use, 1 means in use. Calculating the hydraulic flow requirements enables the system to make dynamic adjustments under different flight states and environmental conditions to meet different control requirements and flight performances, and improve the adaptability of the system.

[0151] The calculation formula for the final hydraulic flow requirements is as follows:

[0152]

[0153] By calculating the final hydraulic flow requirements, it can ensure that the hydraulic system can meet the control requirements of the aircraft under various flight conditions, so as to maintain good flight performance. In the formula, H_Q i represents the final hydraulic flow requirements of the i-th hydraulic source, RT_Qi [j] represents the hydraulic flow rate required for the j-th rudder surface for the i-th set of hydraulic sources. n represents the number of hydraulic sources. Accurately calculating the hydraulic flow rate demand can avoid over-design, reduce unnecessary energy consumption, and improve the energy efficiency of the system, which is of great significance for improving the economy of the aircraft and long-duration flight.

[0154] S4. Through the control model with hydraulic flow rate calculation, conduct simulation analysis of the control system to obtain the flow rate demand at any time, verify the demands put forward in the project demonstration stage and the preliminary design stage, and provide a reference for the optimal design of the aircraft.

[0155] See Figure 5 As shown, it is the flight control system of the control model with hydraulic flow rate calculation of the present application. Through the control model, when conducting simulation analysis of the control system, the flow rate demand can be obtained at any time, which is convenient for verifying the demands put forward in the project demonstration stage and the preliminary design stage. When the flow rate is insufficient, an alarm is promptly issued, which is convenient for the optimal design of the aircraft, so that the flight control system can provide accurate hydraulic flow rate demand input for the hydraulic system design, without wasting the flow rate of the hydraulic system on the premise of meeting the requirements of the flight control system, and achieving the optimal overall design index of the aircraft.

[0156] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A hydraulic flow demand calculation method for a flight control system based on flight quality requirements, characterized in that It includes the following steps: S1. Select the flight qualities related to hydraulic flow rate; Construct a target aircraft model according to the selected flight qualities, and give the transfer function of the target aircraft according to the equivalent fitting formulas of the short-period pitch angle rate and normal overload in the longitudinal direction of the aircraft; According to the inverse function from the aircraft body to the aircraft response parameters, inversely solve the rudder surface commands required to achieve the response parameters; Calculate the required motion rate value of the control surface according to the rate limit of the control surface actuator model And the power required for all control surface actuators of the flight control system to move simultaneously; S2. Compare with the calculation method of the rudder surface combination where all the original rudder surfaces move simultaneously, conduct an analysis of the rudder surface combination movement based on actual flight tests, analyze the division of flight phases and control actions in actual flight tests, and select the cases with relatively strict rudder surface combinations in combination with the flight quality flight test items, including tight turns, decelerated turns, maximum roll and pitch combined controls, coordinated sideslips, lateral-directional controls under asymmetric thrust, and takeoff and landing under strong crosswinds; S3. Calculate the hydraulic flow demand based on the configuration of the control surface energy, including the hydraulic flow RT_Q i [j] required by the j-th control surface for the i-th hydraulic source and the final hydraulic flow demand of the i-th hydraulic source; S4. Through a control model with hydraulic flow rate calculation, conduct a simulation analysis of the control system, obtain the flow rate requirements at any time, verify the requirements proposed in the project demonstration phase and the preliminary design phase, and provide a reference for the optimal design of the aircraft.

2. The hydraulic flow demand calculation method of a flight control system based on flight quality requirements according to claim 1, characterized in that In the above-mentioned S1, before selecting the flight qualities related to hydraulic flow rate, calculate the maximum power required to operate the rudder surface to overcome the hinge moment at a specified deflection speed, and the formula is as follows: In the formula, N max represents the maximum power required for the movement of a certain control surface of the flight control system, K represents the coefficient of the working characteristics of different control surface actuators, and M max represents the maximum hinge moment of the control surface, represents the required movement rate of the control surface.

3. A hydraulic flow demand calculation method for a flight control system based on flight quality requirements according to claim 2, characterized in that, In the above-mentioned S1, for the short-period pitch angle rate criterion in the longitudinal direction of the aircraft, its flight quality response has the following characteristics: (1) The effective delay time t1 is in the following range: Level 1: t1 ≤ 0.12 s; Level 2: t1 ≤ 0.17 s; Level 3: t1 ≤ 0.21 s; (2) The transient peak ratio Δω2 / Δω1 meets the following requirements: Level 1: less than or equal to 0.3; Level 2: less than or equal to 0.6; Level 3: less than or equal to 0.85; (3) The effective rise time Δt is in the following range: ① Non-terminal flight phase: Level 1: 29.6 / V T ≤t1≤1645 / V T ; Level 2: 10.5 / V T ≤t1≤5263 / V T ; ② Terminal flight phase: Level 1: 29.6 / V T ≤t1≤658 / V T ; Level 2: 10.5 / V T ≤t1≤2122 / V T ; In the formula, V T represents the true airspeed.

4. A method for calculating the hydraulic flow demand of a flight control system based on flight quality requirements according to claim 3, characterized in that In the above-mentioned S1, for the short-period normal overload criterion in the longitudinal direction of the aircraft, its flight quality response has the following characteristics: For V 表 ≥1.5V 表机动 When it reaches the overload value of 0.95*n yss the rise time t r shall not exceed: Level 1: 1.5 s; Level 2: 2.0 s; Level 3: 2.5 s; For V 表机动 ≤V 表 ≤1.5V 表机动 When it reaches an overload value of 0.95*n yss The rise time t r shall not exceed: Level 1: 2.0 s; Level 2: 2.5 s; Level 3: 3.0 s; For V 表 ≥1.5 V 表机动 when the overload overshoot (n ymax -n yss ) / n yss shall not exceed: Level 1: 10%; Level 2: 20%; Level 3: 30%; The overloading response decays to plus or minus 5%n yss and the number of oscillations is not greater than 3 times. In the formula, V 表 is the indicated airspeed; V 表机动 refers to the minimum indicated airspeed for the aircraft's maneuvering flight, n yss is the steady-state overloading, n ymax is the maximum overloading.

5. A method for calculating the hydraulic flow demand of a flight control system based on flight quality requirements according to claim 4, characterized in that, In the above-mentioned S1, construct a target aircraft model according to the selected flight qualities, and give the transfer function of the target aircraft according to the equivalent fitting formulas of the short-period pitch angle rate and normal overload. Among them, the equivalent fitting formula is the Laplace transform formula, as follows: In the formula, s is the Laplace operator, represents the transfer function of the pitch rate with respect to the stick force or stick displacement, is the molecular proportionality coefficient of the pitch rate transfer function, τ ω is the equivalent delay time of the pitch rate, ε n1 is the short-period equivalent damping ratio, ω n1 is the short-period equivalent frequency; represents the transfer function of the normal overload with respect to the stick force or stick displacement, is the molecular proportionality coefficient of the normal overload transfer function, τ n is the overload equivalent delay time, represents the molecular time constant of the short period, and e is the base of the natural logarithm.

6. A hydraulic flow demand calculation method for a flight control system based on flight quality requirements according to claim 5, characterized in that In S1, according to the rate limit of the control surface actuator model, calculate the required movement rate of the control surface The calculation process is as follows: Taking the pitch rate response parameter and the normal overload response parameter as inputs, according to the inverse functions from the aircraft body to each response parameter, the rudder command δ required to achieve the pitch rate and the normal overload response parameter is obtained by inverse solution cmd ; The rudder command δ cmd is input into the actuator model with rate limiting, and then simulated through the aircraft body model. The responses of the pitch rate and the normal overload are output, and compared with the pitch rate response parameter and the normal overload response parameter. If the flight quality requirements of the pitch rate response parameter and the normal overload response parameter are met, the rate limit value is further reduced until the requirements are not met. At this time, the rate limit value is the required motion rate value 7. A method for calculating the hydraulic flow demand of a flight control system based on flight quality requirements according to claim 6, characterized in that, In the above-mentioned S1, calculate the power required for all the rudder surface actuators of the flight control system to move simultaneously according to the rate limit of the rudder surface actuator model, and the calculation formula is as follows: In the formula, N represents the power required by all actuators of the flight control system, N max represents the maximum power required for the movement of a certain control surface of the flight control system, and represents the power loss coefficient.

8. A hydraulic flow demand calculation method for a flight control system based on flight quality requirements according to claim 7, characterized in that In the above-mentioned S2, according to the different requirements of flight missions, clearly divide each stage of the flight test, including takeoff, climb, cruise, approach, landing, etc. Each stage will correspond to different control actions and rudder surface combination requirements, and each stage is quantitatively calibrated through speed, altitude, and attitude parameters.

9. A method for calculating the hydraulic flow demand of a flight control system based on flight quality requirements according to claim 8, wherein, In S3, calculate the hydraulic flow demand based on the configuration of the control surface energy, including the hydraulic flow RT_Q i [j] required by the j-th control surface for the i-th hydraulic source. The calculation formula is as follows: In the formula, RT_Q i [j] represents the hydraulic flow rate required by the j-th rudder surface for the i-th set of hydraulic sources, represents the movement speed of the j-th rudder surface, SQ[j] represents the conversion coefficient from the rudder surface movement speed to the flow rate, which is calculated through the connecting rod length and piston area of the actuator, and ST[j] represents the usage status of the j-th rudder surface for the i-th set of hydraulic sources.

10. A hydraulic flow demand calculation method for a flight control system based on flight quality requirements according to claim 9, characterized in that, In the above-mentioned S3, calculate the hydraulic flow rate requirements based on the configuration of the rudder surface energy source. The calculation formula for the final hydraulic flow rate requirement of the i-th set of hydraulic sources is as follows: In the formula, \(H_Q\) i represents the final hydraulic flow rate requirement of the \(i\)-th set of hydraulic sources, and \(RT_Q\) i [j] represents the hydraulic flow rate required by the \(j\)-th rudder surface for the \(i\)-th set of hydraulic sources, and \(n\) represents the number of hydraulic sources.

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