A method for analyzing critical value of control surface speed and hydraulic flow demand of flight control system

Abstract

The present invention discloses a method for analyzing the critical value of the rudder rate and the hydraulic flow demand of the flight control system. Step 1: Input the rudder deflection instruction into a steering gear model with a rate limiter to obtain a rudder deflection response with a rate limit; Step 2: Input the rudder deflection response into a natural aircraft model or an ideal aircraft model, and calculate the flight quality according to the aircraft output response; If the flight quality does not meet the requirements, increase the rate limit, repeat step 1 until the flight quality meets the requirements, and find the critical value of the rudder rate; Step 3: Bring the steering gear model with a rate limiter into the natural aircraft model, and calculate the hydraulic flow demand of the flight control system in all scenarios under each flight stage and each flight condition according to the process of the mission profile. The present invention can accurately and quickly provide design input for the flight control system, ensure the rationality of the design, shorten the iterative development time, and reduce the development risk.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft flight control system design, and in particular relates to a method for analyzing a critical value of a control surface speed and a hydraulic flow demand of a flight control system. Background Art

[0002] The flight control system is an important user of the hydraulic system. It is used throughout the entire flight process to control the safe flight of the aircraft. The rudder velocity and hydraulic flow demand are key inputs in the design of the flight control system. The traditional solution method for the hydraulic flow of the aircraft flight control system is that the control stability professional proposes the rudder hinge torque, and then refers to the same type of aircraft to give the rudder velocity based on experience. Finally, the peak flow superposition method is used to superimpose the peak flows of each rudder together to obtain the maximum required flow. This solution method is often conservative and will cause the hydraulic flow to be over-designed.

[0003] In order to meet the flight quality requirements in aircraft design, the rudder speed needs to reach a certain value. A rudder speed above this value can meet the flight quality requirements, but the greater the rudder speed, the greater the required flow rate, the higher the power of the hydraulic system, and the larger the volume and weight of the hydraulic system, which is not conducive to aircraft design.

[0004] Aircraft design is a long cycle that requires repeated iterations. The main flight control system, which involves the flight quality and flight safety of the aircraft, requires iterative analysis to ensure the rationality of the design. Based on this, it is urgent to design an analysis method that can accurately reflect the critical value of the control surface speed and the hydraulic flow demand of the flight control system. Summary of the invention

[0005] The purpose of the present invention is to provide a method for analyzing the critical value of the rudder speed and the hydraulic flow demand of the flight control system. The present invention can accurately and quickly provide design input for the flight control system, ensure the rationality of the design, shorten the iterative development time, and reduce the development risk.

[0006] The technical solution of the present invention is: a method for analyzing the critical value of the control surface speed and the hydraulic flow demand of the flight control system, comprising:

[0007] Step 1, inputting the rudder deflection command into the servo model with a rate limiter to obtain a rudder deflection response with a rate limiter;

[0008] Step 2: Input the rudder deflection response into the natural aircraft model or the ideal aircraft model, and calculate the flight quality according to the aircraft output response; if the flight quality does not meet the requirements, increase the speed limit, repeat step 1 until the flight quality meets the requirements, and calculate the critical value of the rudder speed;

[0009] Step 3: Bring the servo model with rate limiter into the natural aircraft model, and calculate the hydraulic flow demand of the flight control system in all scenarios under each flight phase and flight condition according to the process of the mission profile.

[0010] In the aforementioned control surface rate critical value and flight control system hydraulic flow demand analysis method, the flight quality in step 2 is: the flight quality of the aircraft dynamic response related to the control surface deflection rate.

[0011] In the aforementioned control surface velocity critical value and flight control system hydraulic flow demand analysis method, the flight quality includes longitudinal flight quality, lateral flight quality, heading flight quality and PIO flight quality.

[0012] In the aforementioned control surface rate critical value and flight control system hydraulic flow demand analysis method, the ideal aircraft model in step 2 is a low-order equivalent aircraft model that meets the flight quality requirements and is used in the early stage of aircraft design.

[0013] In the aforementioned method for analyzing the critical value of the control surface velocity and the hydraulic flow demand of the flight control system, the critical value of the control surface velocity in step 2 is a control surface velocity value that meets the flight quality requirements and can design the volume and weight of the hydraulic system to be as small as possible.

[0014] In the aforementioned method for analyzing the critical value of the control surface velocity and the hydraulic flow demand of the flight control system, the natural aircraft model in step 2 is a nonlinear dynamic model of the aircraft, which is used in the later stage of aircraft design.

[0015] In the aforementioned control surface rate critical value and flight control system hydraulic flow demand analysis method, the flight conditions in step 3 include: normal conditions, crosswind conditions and engine failure conditions.

[0016] In the aforementioned control surface rate critical value and flight control system hydraulic flow demand analysis method, the flight phases in step 3 include taxiing, take-off, climb, cruise and descent.

[0017] The advantages of the present invention are as follows: the conventional rudder speed is mainly based on the empirical method, an aircraft with the same configuration is selected, the maximum rudder speed value obtained during the test flight of the aircraft is taken as a standard, the rudder speed value of the new aircraft is designed, and the hydraulic flow is solved by the peak superposition method under the rudder speed value. The present invention obtains the critical value of the rudder speed that meets the flight quality requirements, and then obtains the hydraulic flow demand of the flight control system in the mission profile process, which can get rid of the over-design caused by the traditional empirical method, provide accurate input for the design of the flight control system, reduce the volume and weight of the flight control hydraulic system, thereby reducing the design cost of the flight control system, and the present invention can quickly realize the analysis of the hydraulic flow demand, so that the two-month iteration cycle of the traditional manual calculation is reduced to one week, reducing the development time and saving time cost.

[0018] In summary, the present invention can accurately and quickly provide design input for the flight control system, ensure the rationality of the design, shorten the iterative development time, and reduce the development risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Flowchart for solving critical value of aircraft control surface deflection rate and flow demand of flight control system;

[0020] Figure 2 This is a servo model with rate limitation;

[0021] Figure 3 Flow chart for solving critical value of rudder speed;

[0022] Figure 4 Solve the detailed flow chart for the flow demand of the aircraft flight control system. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is by no means limited to any specific settings and methods proposed below, but covers any improvements, replacements and modifications of structures, methods, devices without departing from the spirit of the present invention. In the accompanying drawings and the following description, known structures and technologies are not shown to avoid unnecessary ambiguity in the present invention.

[0025] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other, and the embodiments can refer to and quote each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] Example 1. A method for analyzing the critical value of the control surface speed and the hydraulic flow demand of the flight control system, see Figure 1-4 ,include:

[0027] Step 1: Input the rudder deflection command into the servo model with rate limiter to obtain the rudder deflection response with rate limiter. The rudder deflection command is obtained according to the corresponding flight quality specification requirements, such as step command, square wave command, etc. Figure 2 As shown in the figure, δ e is the servo input command, e is the difference between the input command and the feedback command, δ′ e is the servo speed, v is the servo saturation speed, and δ is the servo output.

[0028] Step 2. Input the rudder response into the natural aircraft model, and calculate the flight quality based on the aircraft output response. If the flight quality does not meet the requirements, increase the rate limit and repeat step 1 until the flight quality meets the requirements, and find the critical value of the rudder rate. The rudder rate affects the dynamic response of the aircraft. The flight qualities related to the dynamic response of the aircraft include the short-period frequency, damping ratio and CAP control expected parameters in the longitudinal quality, the pitch angle rate criterion, and the normal overload time response criterion; the roll modal time constant, roll delay criterion, and roll oscillation criterion in the lateral flight quality; the Dutch roll minimum damping and frequency in the heading flight quality, and the sideslip angle response criterion; the bandwidth criterion in the PIO evaluation criterion, and the time domain Neal-smith criterion. According to the different stages of the aircraft, the requirements for the first-level flight quality are given. The specific solution process of the critical value of the rudder rate is as follows: Figure 3 shown.

[0029] Step 3: Bring the servo model with rate limit into the natural aircraft model, and calculate the hydraulic flow requirements of the flight control system in different flight phases and different flight conditions according to the mission profile process. The specific calculation process is as follows: Figure 4 As shown, the specific steps are as follows:

[0030] (1) Provide the state parameters of the initial flight phase and input the control surface control instructions according to the state parameters to be achieved;

[0031] (2) Based on the current state parameters of the aircraft and the input control surface commands, the control commands are solved according to the control law and input into the steering gear;

[0032] (3) The steering gear moves according to the control command and deflects the rudder surface. The flow rate of the input steering gear that changes with the deflection process of the rudder surface and the flow rate of the hydraulic system leakage (mainly the leakage of the servo valve) during the deflection process of the rudder surface are calculated. The sum of the two flow rates is the flow rate required by the system;

[0033] (4) Input the rudder deflection into the aircraft's six-degree-of-freedom dynamics model and calculate the aircraft state. If the aircraft state does not reach the target value, continue to input the rudder command. If the aircraft state reaches the target value, proceed to the next step.

[0034] (5) Determine whether the mission is completed. If the mission is not completed, enter the next flight phase. If the mission is completed, the entire calculation process ends and the output is a curve of the flow rate required by the system changing with time.

Claims

1. A method for analyzing the critical value of control surface velocity and the hydraulic flow demand of a flight control system, characterized in that: include: Step 1, inputting the rudder deflection command into the servo model with a rate limiter to obtain a rudder deflection response with a rate limiter; Step 2: Input the rudder deflection response into the natural aircraft model or the ideal aircraft model, and calculate the flight quality according to the aircraft output response; if the flight quality does not meet the requirements, increase the speed limit, repeat step 1 until the flight quality meets the requirements, and calculate the critical value of the rudder speed; Step 3: Bring the servo model with rate limiter into the natural aircraft model, and calculate the hydraulic flow demand of the flight control system in all scenarios under each flight phase and each flight condition according to the process of the mission profile; The flying qualities in step 2 are: the flying qualities of the aircraft dynamic response related to the control surface deflection rate; The flying qualities include longitudinal flying qualities, lateral flying qualities, heading flying qualities and PIO flying qualities; The control surface rate affects the dynamic response of the aircraft. The flight qualities related to the dynamic response of the aircraft include the short-period frequency, damping ratio and CAP control expected parameters in the longitudinal quality, the pitch angle rate criterion, and the normal overload time response criterion; the roll modal time constant, roll delay criterion, and roll oscillation criterion in the lateral flight quality; Dutch roll minimum damping and frequency in heading flight quality, sideslip angle response criteria; bandwidth criteria in PIO evaluation criteria, time domain Neal-smith criteria; according to different stages of the aircraft, the requirements for first-level flight quality are given; The calculation process of the hydraulic flow demand of the flight control system in different flight phases and different flight conditions is as follows: (1) Provide the state parameters of the initial flight phase and input the control surface control instructions according to the state parameters to be achieved; (2) Based on the current state parameters of the aircraft and the input control surface commands, the control commands are solved according to the control law and input into the steering gear; (3) The steering gear moves according to the control command and deflects the rudder surface. The flow rate of the input steering gear that changes with the deflection process of the rudder surface and the flow rate of the hydraulic system leakage during the deflection process of the rudder surface are calculated. The sum of the two flow rates is the flow rate required by the system; (4) Input the rudder deflection into the aircraft's six-degree-of-freedom dynamics model and calculate the aircraft state. If the aircraft state does not reach the target value, continue to input the rudder command. If the aircraft state reaches the target value, proceed to the next step. (5) Determine whether the mission is completed. If the mission is not completed, enter the next flight phase. If the mission is completed, the entire calculation process ends and the output is a curve of the flow rate required by the system changing with time.

2. The method for analyzing the critical value of control surface velocity and the hydraulic flow demand of the flight control system according to claim 1, characterized in that: The ideal aircraft model in step 2 is a low-order equivalent aircraft model that meets the flight quality requirements and is used in the early stages of aircraft design.

3. The method for analyzing the critical value of control surface velocity and the hydraulic flow demand of the flight control system according to claim 1, characterized in that: The critical value of the control surface velocity in step 2 is: a control surface velocity value that can both meet the flight quality requirements and design the volume and weight of the hydraulic system to be small.

4. The method for analyzing the critical value of control surface velocity and the hydraulic flow demand of the flight control system according to claim 1, characterized in that: The natural aircraft model in step 2 is a nonlinear dynamic model of the aircraft, which is used in the later stage of aircraft design.

5. The method for analyzing the critical value of control surface velocity and the hydraulic flow demand of the flight control system according to claim 1, characterized in that: The flight conditions in step 3 include: normal conditions, crosswind conditions and engine failure conditions.

6. The method for analyzing the critical value of control surface velocity and the hydraulic flow demand of the flight control system according to claim 1, characterized in that: The flight phases in step 3 include taxi, takeoff, climb, cruise, and descent.

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