A stability augmentation system for lateral layered control of an aircraft

Abstract

The application provides a stability enhancement system for aircraft lateral layered control, belongs to the technical field of automatic flight control, and relates to the technical field of automatic flight control.The system meets the design standard of a civil aviation IIIa control system.The system adopts a layered control architecture combining outer loop PID track tracking control and inner loop lateral heading model predictive control (MPC).The outer loop PID control is responsible for basic track tracking, and the inner loop MPC finely adjusts the heading angle and the track to ensure that the aircraft accurately aligns with the runway and stably flies.The method not only improves the control precision and response speed, but also significantly reduces the calculation burden, enhances the robustness and anti-interference ability of the system by combining the simplicity of the PID control and the multivariable optimization capability of the MPC.The system can effectively improve the stability of the aircraft lateral control under complex flight environment, and ensures the safety and reliability of the aircraft during the automatic landing task.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of automatic flight control, and relates to a stability enhancement system for aircraft lateral layered control. BACKGROUND

[0002] Fixed-wing aircraft, including civil passenger aircraft, military aircraft and unmanned aerial vehicles, need to perform take-off and landing procedures. In particular, the landing process is a complex and challenging task that often involves many accidents. Therefore, designing an automatic landing system with robustness and precise control ability to resist external disturbances has become an urgent task in the aviation field. With the continuous progress of aviation technology and the increasing demand for civil aviation, highly automated flight control systems, especially automatic landing systems, are gradually becoming the focus of research. These systems can significantly improve flight safety and operational efficiency under complex flight conditions such as low visibility and bad weather.

[0003] In the process of automatic landing, the importance of lateral control (such as track following and crosswind compensation) is particularly prominent. Lateral control not only directly relates to the precise heading tracking of the aircraft, but also is crucial to ensuring the smooth landing of the aircraft and avoiding deviation from the runway. It is an indispensable part of the automatic landing system, especially in complex environments, which can effectively ensure that the aircraft travels stably and safely along the predetermined route during flight.

[0004] Model predictive control (MPC) is becoming a mainstream method in the research of automatic landing systems due to its superior constraint handling ability and optimization performance, especially in the application of fixed-wing aircraft automatic landing control. Future research is expected to make greater breakthroughs in the integration and optimization of MPC and other advanced control strategies to cope with more complex and dynamic flight environments, further improve the accuracy and robustness of lateral control, and ensure flight safety. SUMMARY

[0005] The purpose of the present application is to solve the need for an automatic landing system with robustness to external disturbances and precise control ability in the prior art. The present application provides a stability enhancement system for aircraft lateral layered control, which uses a control mode combining outer loop PID control and inner loop MPC control to improve the effectiveness of safe automatic landing of the aircraft.

[0006] The present application specifically adopts the following technical solution to achieve the above purpose: a stability enhancement system for aircraft lateral layered control, comprising the following steps:

[0007] S1: establishing an automatic landing mathematical model of aircraft lateral motion;

[0008] S2: Obtain the lateral trajectory tracking instructions of each stage of the aircraft after the aircraft is prepared for landing, i.e. the heading deviation ξ, the heading ψ, the runway heading ψ rw , and the real-time height H. These signals are sent to the outer loop PID controller for accurate tracking and to generate the target roll angle φ g instruction;

[0009] S3: The target roll angle φ g output by the outer loop PID controller is sent to the inner loop MPC controller as the input of the inner loop control, and the control instructions δ a and δ r for the aileron rudder are obtained.

[0010] S4: According to the control instructions output by the controller and the described mathematical model of the automatic landing of the aircraft, the real-time dynamic signals of the aircraft are obtained to realize the control of the automatic landing of the aircraft.

[0011] Further, in S1, when designing the flight control system, whether using traditional classic control theory PID control or using many modern control theories to control the aircraft, the approximate dynamic linear equation of the aircraft equation needs to be obtained. The linear model of the aircraft body is determined by the nonlinear model, and the most commonly used method is to linearize the nonlinear state equation according to the small disturbance principle. According to the linear disturbance motion separation principle, linearization and decoupling processing are performed at the equilibrium point, and the continuous domain lateral motion state space equation is obtained as follows:

[0012]

[0013] Where Δβ, Δp, Δr, Δφ are the increments of the side slip angle, the roll angle velocity, the yaw angle velocity and the roll angle of the aircraft, respectively, and Δδ a is the input increment of the aileron deflection angle, and Δδ r is the input increment of the rudder deflection angle. Y β , Y p , Y r , Y φ , L β , L p , L r , N β are the coefficients of the lateral state matrix of the aircraft.

[0014] Further, the outer loop control rate of each stage designed in S2 is as follows:

[0015] 1) Heading selection control law algorithm

[0016] The function of the high hold control law is to control the aircraft to turn and fly to the centerline of the localizer at a certain intercept angle until the localizer beam is acquired.

[0017] φ g = K ψ (ψ g - ψ) (2)

[0018] where K ψ is the localizer deviation coefficient.

[0019] 2) Localizer mode control law algorithm

[0020] The localizer control law is used to control the aircraft to fly along the centerline of the horizontal beam of the runway, mainly introducing the LOC deviation and the aircraft heading signal. In order to better make the control accuracy of the approach lateral meet the index requirements, the localizer mode control law needs to be designed in segments according to the initial acquisition and tracking sub-mode and the terminal tracking sub-mode.

[0021] The initial acquisition and tracking stage,

[0022] φ g = K ξ ξ + K ψ (ψ RH - ψ) (3)

[0023] where K ξ is the proportional coefficient, and K ψ is the proportional coefficient.

[0024] The terminal tracking stage,

[0025]

[0026] where K is the differential coefficient.

[0027] 3) Aligning runway control law

[0028] The aligning runway control law aligns the nose of the aircraft with the centerline of the runway and keeps the wings level by controlling the rudder.

[0029] φ g = 0

[0030] δ r = K r (ψ RH - ψ) (5)

[0031] where δ r is the rudder command, and K r is the proportional coefficient of the heading angle and the runway heading deviation.

[0032] 4) Low nose control law

[0033] The low head control law will control the aircraft head to turn down, so that the nose landing gear gently touches the runway.

[0034] θ g = K θ (6)

[0035] In the formula, K θ is the target pitch angle.

[0036] Further, the inner loop attitude MPC control rate in S3 is designed as follows: the continuous domain lateral aircraft state space equation in S1 is discretized with a task cycle of 0.02 seconds. The fixed-wing aircraft automatic landing control belongs to the typical trajectory tracking control, and the lateral and lateral state variable parameters are defined as:

[0037] x r = [Δβ Δp Δr Δφ] T (7)

[0038] The lateral control output parameters are defined as:

[0039] u r = [Δδ a Δδ r ] (8)

[0040] The tracking error of the command is defined as

[0041] e r = x r -x d (9)

[0042] In the formula, x d represents the expected target value, and the aircraft can fly according to the target roll angle φ g In steady flight, the expected aircraft Δβ, Δp, Δr is generally set to 0, that is,

[0043] x d = [0 0 0 φ g ] (10)

[0044] Considering that the roll angle tracking error e r of the control system in the future period of time is minimum, and the aileron rudder and rudder output of the aircraft is minimum, the cost function of the lateral control optimal control is as follows:

[0045]

[0046] Here, considering the control performance and the calculation load, the model prediction interval cannot be too large, the model prediction interval N of the lateral model predictive controller is defined as 20, that is, the time of the prediction interval is T = 20 * 0.02s. The lateral control state quantity weight coefficient Q and the control quantity weight coefficient R are defined as follows: r r

[0047]

[0048] The lateral control constraint matrix is as follows:

[0049] x r (k+1) = G r x r (k) + H r u r (k) (13)

[0050] Wherein G r and H r are known matrices, and the model prediction interval N of the lateral model predictive controller is also defined as 20, that is, the time of the prediction interval is T = 20 * 0.02s. Considering the upper and lower bound constraints of the control variable, the constraint of the matrix U is:

[0051]

[0052] The beneficial effects of the present application are as follows:

[0053] The present application adopts a hierarchical control method of outer loop trajectory tracking PID control and inner loop attitude model predictive control (MPC), and the MPC has obvious advantages in processing multivariable systems, optimizing target control and real-time scheduling under constraint conditions as an advanced control strategy. The model predictive control (MPC) method is particularly suitable for complex dynamic environments due to its strong prediction ability and online optimization characteristics. The present application designs a new type of automatic landing control system, which can significantly improve the stability of automatic landing of the aircraft. The system is not only easy to implement in engineering, but also can be converted into software requirements, facilitating coding and debugging, and has strong engineering practical value. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is a flowchart of the method provided by the present application;

[0055] Figure 2 is an architecture diagram for implementing the method provided by the present application;

[0056] Figure 3 is a schematic diagram of division of each stage of automatic landing of the aircraft in the embodiment of the present application;

[0057] ​​Figure 4 This is a diagram illustrating the outer loop trajectory tracking control effect provided in an embodiment of the present invention.

[0058] Figure 5 This is a diagram illustrating the inner-loop attitude control effect provided in an embodiment of the present invention.

[0059] Figure 6 This is a schematic diagram of flight trajectory control provided in an embodiment of the present invention. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0061] This embodiment provides a stability enhancement system for lateral layered control of aircraft, mainly used to solve the problem of automatic flight and landing control, and provides the following technical solution, which will be combined with... Figures 1-6 Please provide a detailed explanation:

[0062] The present invention will now be described in further detail with reference to the accompanying drawings. The workflow of the present invention is as follows:

[0063] S1: Establish a mathematical model for automatic landing of aircraft lateral motion;

[0064] S2: After the aircraft prepares for landing, it acquires tracking commands for the aircraft's lateral motion trajectory at each stage, namely, heading deviation ξ, heading ψ, and runway heading ψ. rw Real-time altitude H. These signals are sent to the outer loop PID controller for accurate tracking and to generate the target roll angle φ. g instruction;

[0065] S3: The target roll angle φ output by the outer loop PID controller g And the target speed V of the aircraft g The command δ is sent to the inner loop MPC controller as input for inner loop control, resulting in the control of the aircraft's aileron rudder. a and the command to release the rudder δ r ;

[0066] S4: Based on the control commands output by the controller and the mathematical model of the aircraft's lateral motion for automatic landing, obtain the real-time dynamic signals of the aircraft to achieve automatic landing control of the aircraft.

[0067] In some embodiments, S1 includes:

[0068] In the design of flight control system, whether using traditional PID control or using many modern control theory to control the aircraft, the linearized equation of the approximate dynamics of the aircraft equation is needed. The most commonly used method is to linearize the nonlinear state equation according to the small disturbance principle. According to the linear disturbance motion separation principle, linearization and decoupling are carried out at the equilibrium point to obtain the continuous domain lateral motion state space equation:

[0069]

[0070] Where, Δβ, Δp, Δr, Δφ are the increments of the aircraft's sideslip angle, roll angular velocity, yaw angular velocity and roll angle, respectively, Δδ a is the input increment of the aircraft aileron deflection angle, Δδ r is the input increment of the aircraft rudder deflection angle. Y β , Y p , Y r , Y φ , L β , L p , L r , N β are the coefficients of the aircraft lateral state matrix.

[0071] In some embodiments, the outer loop control rates of each stage designed in the S2 are as follows:

[0072] 1) Heading selection control law algorithm

[0073] The function of the height holding control law is to control the aircraft to turn and fly to the center line of the heading path with a certain intercept angle until the heading beacon beam is intercepted.

[0074] φ g = K ψ (ψ g - ψ) (2)

[0075] Where, K ψ is the heading deviation coefficient.

[0076] 2) Heading path mode control law algorithm

[0077] The heading path control law is used to control the aircraft to fly along the center line of the horizontal beam of the runway, mainly introducing the LOC deviation and the aircraft heading signal. In order to better meet the control accuracy requirements of the approach lateral, the heading path mode control law needs to be designed in segments according to the initial capture and tracking sub-mode and the terminal tracking sub-mode.

[0078] Initial capture and tracking stage,

[0079] φg = K ξ ξ + K ψ (ψ RH - ψ) (3)

[0080] where K ξ is a proportional coefficient, K ψ is a proportional coefficient.

[0081] terminal tracking phase,

[0082]

[0083] where K is a differential coefficient.

[0084] 3) Align runway control law

[0085] The align runway control law aligns the nose of the aircraft with the centerline of the runway and keeps the wings level by controlling the rudder.

[0086] φ g = 0

[0087] δ r = K r (ψ RH - ψ) (5)

[0088] where δ r is the rudder command, K r is a proportional coefficient of the heading angle and the runway heading deviation.

[0089] 4) Low nose control law

[0090] The low nose control law controls the nose of the aircraft to turn down so that the nose gear contacts the runway gently.

[0091] θ g = K θ (6)

[0092] where K θ is the target pitch angle.

[0093] In some embodiments, the inner loop attitude MPC control law in S3 is designed as follows:

[0094] The continuous domain lateral aircraft state space equations in S1 are discretized with a task period of 0.02 seconds. The fixed-wing aircraft automatic landing control belongs to a typical trajectory tracking control, and the lateral and lateral state variable parameters are defined as:

[0095] x r = [ Δβ Δp Δr Δφ] T (7)

[0096] The lateral control output parameter is defined as

[0097] u r = [Δδ a Δδ r ] (8)

[0098] The tracking error of the command is defined as

[0099] e r = x r -x d (9)

[0100] In the formula, x d represents the desired target value, and the aircraft can fly according to the target roll angle φ g . In steady flight, the expected aircraft Δβ, Δp, and Δr are generally set to 0, that is,

[0101] x d = [0 0 0 φ g ] (10)

[0102] The roll angle tracking error e r of the control system in the future time period is considered to be minimized, and the aileron rudder and rudder output of the aircraft is minimized. The cost function of the lateral control optimal control is as follows:

[0103]

[0104] Here, considering the control performance and the calculation load, the model prediction interval cannot be too large. The model prediction interval N of the lateral model predictive controller is defined as 20, that is, the time of the prediction interval is T = 20 * 0.02 s. The lateral control state weight coefficient Q r and the control weight coefficient R r are defined as follows:

[0105]

[0106] The lateral control constraint matrix is as follows:

[0107] x r (k+1) = G r x r (k) + H r u r (k) (13)

[0108] wherein G r and H r are known matrices. The model prediction interval N of the lateral model predictive controller is also defined as 20, that is, the time of the prediction interval is T = 20 * 0.02 s. Considering the upper and lower bound constraints of the control variable, the constraint of the matrix U is:

[0109]

[0110] In some embodiments, real-time dynamic signals of the aircraft are acquired according to the control instruction output by the controller and the described mathematical model of automatic landing of lateral movement of the aircraft, so as to realize control of automatic landing of the aircraft.

[0111] The simulation experiment is carried out by using Matlab, and the corresponding landing simulation diagram is drawn, as shown in the figure. Figure 4 The initial simulation flight parameters are as follows: 1. The initial corrected airspeed of the aircraft is 75 m / s; 2. The initial height of the aircraft is 500 m; 3. The weight of the aircraft is 46000 kg; 4. The initial flight heading is 0 degree; 5. The target flight heading angle is-50 degrees; and 6. The flap is lowered by 35 degrees.

[0112] As shown in the figures. Figure 4 and Figure 5 The space position curve in the lateral plane and the curve of the lateral flight state changing with time in each stage of automatic landing of the aircraft are shown in the figures. In a stable atmospheric environment, the example aircraft initially flies in a level flight state at a height of 500 m at an approach speed of 65 m / s, and turns to the right to fly towards a target heading angle of-50 degrees, with an interception angle of 50 degrees with the center line of the runway. When the angle between the aircraft and the center line of the runway is less than 0.3 degrees to 2 degrees, the interception heading path is intercepted and the flight direction is adjusted for heading tracking, with a maximum heading overshoot of 1 degree. When the angle between the aircraft and the center line of the glide path is less than 0.05 degrees to 0.2 degrees, the glide path is successfully intercepted and tracking is started, and the flight speed remains unchanged. In the flattening stage, when the height approaches 9 m, the automatic throttle is collected to 0.3, and the lateral mode is switched from the heading path mode to the runway alignment mode. The aircraft finally lands at a distance of 180 m to 227 m from the intersection of the runway, and the lateral landing point is close to the center line of the runway. During the entire flight process, both MPC control and PID control show satisfactory control effect, especially in the output actions of elevator, aileron, rudder and throttle angle, MPC can realize more stable control, ensuring accurate tracking of the heading path and the glide path and safe landing.

[0113] In addition, it can be seen from the figure that Figure 6 that during the glide process, the overall control of the aircraft is stable, the entire motion trajectory of the aircraft accurately tracks the center line of the glide path, and does not exceed the 2-degree glide beam line boundary. After a period of glide, the aircraft begins to slowly approach the center line of the glide path and finally returns to the center line of the glide path. During this process, both MPC control and PID control achieve satisfactory control effect, all indicators meet the relevant requirements of the civil aircraft industry standard, and the effectiveness of the designed hierarchical control method is embodied.

[0114] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A stability augmentation system for lateral layered control of an aircraft, characterized by: The method comprises the following steps: S1: establishing a mathematical model of automatic landing of lateral movement of an airplane; S2: obtain the lateral trajectory tracking instructions of each stage of the aircraft after the aircraft is prepared for landing, i.e. the heading deviation ξ, the heading ψ, the runway heading ψ rw , the real-time height H, send these signals into the outer loop PID controller for accurate tracking and generate the target roll angle φ g instructions; S3: the target roll angle φ output by the outer loop PID controller g and the target speed V of the aircraft motion g is sent to the inner loop MPC controller as the input of the inner loop control, and the command δ a to the aileron rudder of the aircraft is obtained r ; S4: obtaining real-time dynamic signals of the airplane according to the control instruction output by the controller and the described mathematical model of automatic landing of lateral movement of the airplane, so as to realize control of automatic landing of the airplane; The outer loop control rates of each stage designed in the S2 are as follows: 1) a heading selection control law algorithm The height keeping control law is used to control the airplane to turn and fly towards the center line of the heading path with a certain intercept angle until the heading beacon beam is intercepted, φ g = K ψ (ψ g -ψ) In the formula, K ψ is a course deviation coefficient, 2) a heading path mode control law algorithm The heading path control law is used to control the airplane to fly along the center line of the horizontal beam of the runway, mainly introducing the LOC deviation and the airplane heading signal, in order to better make the control precision of the approach lateral meet the index requirements, the heading path mode control law needs to be designed in sections according to the initial capture and tracking sub-mode and the terminal tracking sub-mode, the initial capture and tracking stage, φ g = K ξ ξ + K ψ (ψ RH - ψ) wherein K ξ is a proportionality factor, K ψ is a proportionality factor, the terminal tracking stage, In the formula, is the differential coefficient, 3) an aligning runway control law The aligning runway control law controls the rudder to align the nose of the airplane with the center line of the runway and keep the wings horizontal, φ g = 0 delta r = K r (ψ RH -ψ) where δ r is the rudder command, K r is the proportional coefficient of the heading angle and the runway heading deviation, 4) a low nose control law The low nose control law controls the nose of the airplane to turn downward, so that the front landing gear gently contacts the runway, θ g = K θ In the formula, K θ is the target pitch angle; The inner loop attitude MPC control rate in the S3 is designed as follows: the continuous domain lateral airplane state space equation in the S1 is discretized with a task period of 0.02 seconds, the automatic landing control of the fixed-wing airplane belongs to a typical trajectory tracking control, and the lateral and lateral state variable parameters are defined: x r = [Δβ Δp Δr Δφ] T The lateral control output parameters are defined: u r = [Δδ a Δδ r ] The tracking error of the instruction is defined as e r = x r - x d where x d represents the desired target value, the aircraft can follow the target roll angle φ g flight, the desired aircraft Δβ, Δp, Δr is generally set to 0, i.e., x d = [0 0 0 φ g ] Consider the roll angle tracking error e of the control system in the future period of time r The minimum, and the aileron rudder surface and rudder output of the aircraft is minimum, the optimal control of the lateral control cost function is as follows: Here, considering the control performance and the calculation load, the model prediction interval cannot be too large, the model prediction interval N of the lateral model predictive controller is defined as 20, that is, the time of the prediction interval is T = 20 * 0.02 s, and the lateral control state quantity weight coefficient Q r and the control quantity weight coefficient R r are defined as follows: The lateral control constraint matrix is as follows: x r (k+1) = G r x r (k) + H r u r (k) wherein G r and H r are known matrices, the model prediction interval N = 20 of the lateral model predictive controller is defined, i.e. the time of the prediction interval is T = 20 * 0.02 s, considering the upper and lower bound constraints of the control variable, the constraint of the matrix U is:

2. A stability augmentation system for lateral layered control of an aircraft according to claim 1, wherein, In the S1, when the flight control system is designed, whether a traditional classic control theory PID control or many modern control theories are used to control the airplane, the approximate dynamic linear equation of the airplane equation needs to be obtained, the linear model of the airplane body is determined according to the nonlinear model, and the most commonly used method is to linearize the nonlinear state equation according to the small disturbance principle, the linearization processing and decoupling processing are performed at the equilibrium point according to the linear disturbance motion separation principle, and the continuous domain lateral movement state space equation is as follows: Where Δβ, Δp, Δr, and Δφ are the aircraft's sideslip angle increment, roll rate increment, yaw rate increment, and roll angle increment, respectively, and Δδ a Input the increment Δδ for the aircraft aileron deflection angle. r Input the increment for the aircraft rudder deflection angle, Y β Y p Y r Y φ L β L p L r N β , where is the coefficient of the aircraft's lateral state matrix.

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