An aircraft ground coordinated turning system and its sliding mode control method and system

Abstract

In view of the problem that the current aircraft ground coordinated turning control method has the problem that a large runway space is occupied during the turning process, which easily causes airport traffic congestion, the present application provides an aircraft ground coordinated turning system and its sliding mode control method and system. Based on the real-time parameters of the aircraft, the state of the aircraft ground coordinated turning system is controlled on the front wheel-main wheel coordinated turning composite sliding mode surface through the front wheel-main wheel coordinated turning control law, and a targeted aircraft ground coordinated turning system model is constructed. In view of the control problem of the traditional aircraft ground turning stage, considering the problems of the traditional front wheel steering turning technology such as oversteering of the front landing gear and large turning radius, a sliding mode control method for the aircraft ground coordinated turning system is proposed. Through the coordinated turning of the front wheel-main wheel, the turning radius is effectively reduced, and the accurate trajectory tracking of the aircraft during the ground taxiing process is achieved, which ensures that the aircraft can achieve flexible turning operations with a small radius.

Description

Technical Field

[0001] The present application relates to a sliding mode control method, and specifically to an aircraft ground coordinated turning system and a sliding mode control method and system thereof. Background Art

[0002] The ground taxiing characteristics of an aircraft are an important guarantee for aircraft safety during take-off and landing. Relevant statistics show that 49% of all aircraft safety accidents occur during take-off and landing, which is a high-incidence stage for aircraft accidents.

[0003] At present, the research on the take-off and landing stage of the aircraft is mainly focused on the field of aircraft anti-skid brake control, and there is less research on the ground coordinated turning control of the aircraft. The relevant research mainly focuses on the front wheel steering, engine thrust differential steering, main wheel differential brake steering, etc. In practical applications, the front wheel steering is mainly used for ground turning of the aircraft. However, this method has the disadvantages of excessive steering of the front landing gear and a large turning radius, which will result in a large runway space being occupied during the turning process, further causing airport traffic congestion. Summary of the invention

[0004] In view of the technical problem that the current aircraft ground coordinated turning control method occupies a large runway space during the turning process and easily causes airport traffic congestion, the present application provides an aircraft ground coordinated turning system and its sliding mode control method and system.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect, the present application proposes a sliding mode control method for an aircraft ground coordinated turning system, comprising:

[0007] Get real-time aircraft parameters;

[0008] Based on the real-time parameters of the aircraft, the state of the aircraft ground coordinated turning system is controlled on the nose wheel-main wheel coordinated turning composite sliding surface through the nose wheel-main wheel coordinated turning control law;

[0009] The state of the aircraft ground coordinated turning system includes the steering angles of the left main wheel and the right main wheel, and the steering angle of the front wheel;

[0010] The control target of the nose wheel-main wheel coordinated turning composite sliding surface is that the yaw distance and the yaw angle of the aircraft approach zero within a preset time;

[0011] The front wheel-main wheel coordinated turning control law acquisition method comprises:

[0012] The front wheel-main wheel coordinated turning composite sliding surface is derived, and combined with the aircraft ground coordinated turning system model, the front wheel-main wheel coordinated turning control law is determined; the system state quantities of the aircraft ground coordinated turning system model include the aircraft's yaw distance, the aircraft's yaw angle, the aircraft's longitudinal speed and the yaw angular velocity.

[0013] Furthermore, the aircraft ground coordinated turning system model, the nose wheel-main wheel coordinated turning composite sliding surface and the nose wheel-main wheel coordinated turning control law are all determined based on the aircraft trajectory tracking coordinate system;

[0014] The aircraft trajectory tracking coordinate system includes an inertial reference coordinate system, an aircraft body fixed coordinate system, and a coordinate system defined by a desired trajectory.

[0015] Furthermore, the aircraft ground coordinated turning system model includes:

[0016]

[0017] in, express The first derivative with respect to time, Indicates the lateral speed of the aircraft. Indicates the yaw angle of the aircraft. The vertical speed of the aircraft. express The first derivative with respect to time, represents the yaw angular velocity, Describing the expected trajectory exist The curvature of represents the desired position of the aircraft's center of gravity, Indicates the aircraft's yaw distance, express The first derivative with respect to time, is the rudder force, represents the force of the rudder on the main wheel, represents the force of the rudder on the front wheel, represents the crosswind disturbance force, Indicates the mass of the aircraft, It represents the cornering stiffness of the left and right main wheels when the slip angle is zero. Indicates the steering angle of the left and right main wheels, It represents the cornering stiffness of the front wheel when the sideslip angle is zero. represents the steering angle of the front wheels, represents the first-order derivative with respect to time , It represents the projection distance from the rudder to the center of gravity of the aircraft. Indicates the projection distance from the left main wheel and the right main wheel to the center of gravity of the aircraft. Indicates the projection distance from the front wheel to the center of gravity of the aircraft, represents the projected distance between the left main wheel and the right main wheel, represents the aircraft's moment of inertia, Indicates the ground force of the left main wheel. Indicates the ground force of the right main wheel.

[0018] Furthermore, the front wheel-main wheel coordinated turning composite sliding surface comprises:

[0019]

[0020] in, represents the yaw distance sliding surface, represents the yaw angle sliding surface, represents the sliding surface parameters of the yaw distance to be designed, , , , , Represents the sliding surface parameters of the yaw angle to be designed.

[0021] Furthermore, the front wheel-main wheel coordinated turning control law includes:

[0022]

[0023] in, represents the first intermediate parameter, represents the second intermediate parameter, represents the yaw distance sliding surface, represents the yaw angle sliding surface;

[0024]

[0025]

[0026] in, , , , .

[0027] In a second aspect, the present application proposes a sliding mode control system for an aircraft ground coordinated turning system, comprising:

[0028] Acquisition module, used to obtain real-time parameters of the aircraft;

[0029] A control module, for controlling the state of the aircraft ground coordinated turning system on the front wheel-main wheel coordinated turning composite sliding surface through the front wheel-main wheel coordinated turning control law based on the real-time parameters of the aircraft;

[0030] The state of the aircraft ground coordinated turning system includes the steering angles of the left main wheel and the right main wheel, and the steering angle of the front wheel;

[0031] The control target of the nose wheel-main wheel coordinated turning composite sliding surface is that the yaw distance and the yaw angle of the aircraft approach zero within a preset time;

[0032] The front wheel-main wheel coordinated turning control law acquisition method comprises:

[0033] The front wheel-main wheel coordinated turning composite sliding surface is derived, and combined with the aircraft ground coordinated turning system model, the front wheel-main wheel coordinated turning control law is determined; the system state quantities of the aircraft ground coordinated turning system model include the aircraft's yaw distance, the aircraft's yaw angle, the aircraft's longitudinal speed and the yaw angular velocity.

[0034] Furthermore, the aircraft ground coordinated turning system model, the nose wheel-main wheel coordinated turning composite sliding surface and the nose wheel-main wheel coordinated turning control law are all determined based on the aircraft trajectory tracking coordinate system;

[0035] The aircraft trajectory tracking coordinate system includes an inertial reference coordinate system, an aircraft body fixed coordinate system, and a coordinate system defined by a desired trajectory.

[0036] Furthermore, the aircraft ground coordinated turning system model includes:

[0037]

[0038] in, express The first derivative with respect to time, Indicates the lateral speed of the aircraft. Indicates the yaw angle of the aircraft. The vertical speed of the aircraft. express The first derivative with respect to time, represents the yaw angular velocity, Describing the expected trajectory exist The curvature of represents the desired position of the aircraft's center of gravity, Indicates the aircraft's yaw distance, express The first derivative with respect to time, is the rudder force, represents the force of the rudder on the main wheel, represents the force of the rudder on the front wheel, represents the crosswind disturbance force, Indicates the mass of the aircraft, It represents the cornering stiffness of the left and right main wheels when the slip angle is zero. Indicates the steering angle of the left and right main wheels, It represents the cornering stiffness of the front wheel when the sideslip angle is zero. represents the steering angle of the front wheels, represents the first-order derivative with respect to time , It represents the projection distance from the rudder to the center of gravity of the aircraft. Indicates the projection distance from the left main wheel and the right main wheel to the center of gravity of the aircraft. Indicates the projection distance from the front wheel to the center of gravity of the aircraft, represents the projected distance between the left main wheel and the right main wheel, represents the aircraft's moment of inertia, Indicates the ground force of the left main wheel. Indicates the ground force of the right main wheel.

[0039] Furthermore, the front wheel-main wheel coordinated turning composite sliding surface comprises:

[0040]

[0041] in, represents the yaw distance sliding surface, represents the yaw angle sliding surface, represents the sliding surface parameters of the yaw distance to be designed, , , , , represents the sliding surface parameters of the yaw angle to be designed;

[0042] The front wheel-main wheel coordinated turning control law includes:

[0043]

[0044] in, represents the first intermediate parameter, represents the second intermediate parameter, represents the yaw distance sliding surface, represents the yaw angle sliding surface;

[0045]

[0046]

[0047] in, , , , .

[0048] On the third aspect, the present application proposes an aircraft ground coordinated turning system, comprising a controller and an aircraft ground coordinated turning system body; the controller controls the aircraft ground coordinated turning system body according to the above-mentioned aircraft ground coordinated turning system sliding mode control method.

[0049] Compared with the prior art, this application has the following beneficial effects:

[0050] The present application proposes a sliding mode control method for an aircraft ground coordinated turning system. Based on the real-time parameters of the aircraft, the state of the aircraft ground coordinated turning system is controlled on the front wheel-main wheel coordinated turning composite sliding mode surface through the front wheel-main wheel coordinated turning control law. A targeted aircraft ground coordinated turning system model is constructed. Aiming at the control problem of the traditional aircraft ground turning stage, considering the problems of the traditional front wheel steering turning technology such as oversteering of the front landing gear and large turning radius, a sliding mode control method for the aircraft ground coordinated turning system is proposed. Through the coordinated turning of the front wheel and the main wheel, the turning radius is effectively reduced, the accurate trajectory tracking of the aircraft during the ground taxiing process is realized, and it is ensured that the aircraft can achieve flexible steering operations with a small radius.

[0051] The present application also proposes an aircraft ground coordinated turning system sliding mode control system and an aircraft ground coordinated turning system, which have all the advantages of the above-mentioned aircraft ground coordinated turning system sliding mode control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0053] Figure 1 This is a first flow chart of the sliding mode control method of the aircraft ground coordinated turning system of this application;

[0054] Figure 2 A second flow chart of the sliding mode control method of the aircraft ground coordinated turning system of the present application;

[0055] Figure 3 This is a schematic diagram of aircraft trajectory tracking in an embodiment of the present application;

[0056] Figure 4 This is a lateral force diagram of the aircraft taxiing in the embodiment of the present application;

[0057] Figure 5 This is a top-down force diagram of an aircraft taxiing in an embodiment of the present application;

[0058] Figure 6 is the yaw displacement curve of the cooperative turning control under fixed initial conditions;

[0059] Figure 7 The yaw angle curve of the aircraft under coordinated turning control under fixed initial conditions;

[0060] Figure 8 It is the motion trajectory curve diagram of the cooperative turning control under fixed initial conditions;

[0061] Fig. 9 It is the trajectory tracking curve diagram of the coordinated turning control at different longitudinal speeds;

[0062] Fig.10 It is the trajectory tracking curve diagram of the cooperative turning control under different initial aircraft yaw angles;

[0063] Fig.11 A schematic diagram of a sliding mode control system of the aircraft ground coordinated turning system of the present application. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0065] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0066] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0067] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invented product is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0068] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0069] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0070] When the front wheel steering is used to make a ground turn, a large amount of runway space is occupied during the turn, which easily causes airport traffic congestion. The main reasons are:

[0071] (1) Limitations of front-wheel steering.

[0072] Although nosewheel steering can control the ground direction of the aircraft, the turning radius is limited by many factors such as aircraft size, weight, tire characteristics and runway conditions. Due to their large size and weight, large aircraft usually require a larger turning radius to complete a turn, thus occupying more runway space. In the low-speed taxiing stage, the effect of nosewheel steering is more significant. However, as the speed increases, the maximum steering angle of the front wheel will decrease and the turning radius will increase accordingly. Therefore, during high-speed taxiing or takeoff and landing, nosewheel steering has limited effect on reducing the turning radius.

[0073] (2) Airport traffic flow and runway utilization.

[0074] At the airport, aircraft take-offs and landings and ground taxiing are frequent, and the traffic density is high. If each aircraft occupies a large runway space when turning on the ground, it will aggravate traffic congestion and affect the overall operation efficiency of the airport. In addition, the runway layout and taxiway settings of different airports are different, which will also affect the runway occupancy when the aircraft turns on the ground.

[0075] Based on the above situation, the present application proposes an aircraft ground coordinated turning system and its sliding mode control method and system, and the present application is described in detail below in conjunction with embodiments and drawings.

[0076] Aircraft ground coordinated turning is an important technology for aircraft to perform turning operations during the ground taxiing phase, especially in wide-body aircraft and large transport aircraft. This technology is designed to improve the flexibility and safety of aircraft during ground taxiing, reduce the turning radius, shorten the taxiing time, and thus improve the operational efficiency of the airport. The following is a detailed analysis of aircraft ground coordinated turning:

[0077] Aircraft ground coordinated turning refers to the process of the aircraft taxiing on the ground, through the coordinated control of the tire steering angle of the front landing gear and the main landing gear, to achieve a smooth turn of the aircraft. It is necessary to accurately calculate and control the parameters such as the tire steering angle, taxiing speed and ground friction to ensure that the aircraft maintains stability and safety during the turning process. By coordinating the steering angle of the tires of the front landing gear and the main landing gear, the turning radius of the aircraft can be significantly reduced, and the flexibility of the aircraft when taxiing on the ground can be improved.

[0078] The sliding mode control of the aircraft ground coordinated turning system is an advanced control strategy that combines the robustness of sliding mode control and the complexity of the aircraft ground coordinated turning system to achieve precise control and stability of the aircraft during ground taxiing. Among them, sliding mode control, also known as variable structure control, is a special nonlinear control method. By designing a sliding surface, the system state continuously approaches the sliding surface in the dynamic process and performs sliding mode motion on the sliding surface.

[0079] like Figure 1 As shown, it is a first flow chart of the sliding mode control method of the aircraft ground coordinated turning system of the present application, which may include:

[0080] S101, obtaining real-time parameters of the aircraft.

[0081] In practical applications, when performing sliding mode control of the aircraft ground coordinated turning system, it is necessary to obtain real-time aircraft parameters, such as aircraft speed, attitude, position and other related information. These real-time aircraft parameters can be obtained in real time through various sensors and monitoring systems on the aircraft and transmitted to the aircraft controller. In practical applications, different real-time aircraft parameters can be based on different coordinate systems, and can also be unified through conversion between coordinate systems.

[0082] S102, based on the real-time parameters of the aircraft, the state of the aircraft ground coordinated turning system is controlled on the front wheel-main wheel coordinated turning compound sliding surface through the front wheel-main wheel coordinated turning control law.

[0083] In sliding mode control, the sliding surface is the key element in sliding mode control. The purpose of designing the sliding surface is to enable the system state to slide onto the sliding surface quickly and accurately and keep moving on the sliding surface. The design of the sliding surface depends on the nature of the system and the control objective, which can be determined through mathematical modeling and analysis. The control law is another important component of sliding mode control. By reasonably designing the control law, high-precision control of the system state can be achieved.

[0084] The status of the aircraft's ground coordinated turning system includes the steering angles of the left main wheel, the right main wheel, and the steering angle of the front wheels. Through the coordination of the steering angles of the left main wheel, the right main wheel, and the front wheels, precise control of the aircraft's ground coordinated turning can be achieved to ensure the turning effect.

[0085] The control objective of the nose wheel-main wheel coordinated turning composite sliding surface is to make the aircraft's yaw distance and yaw angle approach zero within a preset time.

[0086] The method for obtaining the front wheel-main wheel coordinated turning control law includes:

[0087] The derivative of the nose wheel-main wheel coordinated turning composite sliding surface is obtained, and the nose wheel-main wheel coordinated turning control law is determined in combination with the aircraft ground coordinated turning system model; the system state quantities of the aircraft ground coordinated turning system model include the aircraft's yaw distance, the aircraft's yaw angle, the aircraft's longitudinal speed and the yaw angular velocity.

[0088] like Figure 2 As shown, it is a second flow chart of the sliding mode control method of the aircraft ground coordinated turning system of the present application, which may include:

[0089] S201, Modeling of aircraft ground coordinated turning system.

[0090] The essence of aircraft ground coordinated turning control is to ensure that the aircraft moves along a predetermined trajectory by controlling the steering angles of the front wheels and the main wheels. In order to describe the trajectory tracking problem of aircraft ground coordinated turning, this application introduces a coordinate system.

[0091] like Figure 3 The figure shows a schematic diagram of the aircraft trajectory tracking coordinate system. The aircraft trajectory tracking coordinate system includes multiple coordinate systems, and none of the coordinate systems show the corresponding Z axis, which can be regarded as perpendicular to the paper. represents the globally fixed inertial reference frame (referred to as the inertial reference frame), represents the fixed coordinate system of the aircraft body, Desired trajectory Defined coordinate system. Point Indicates the actual position of the aircraft's center of gravity, point represents the desired position of the aircraft's center of gravity, Indicates the actual heading angle of the aircraft relative to the inertial reference coordinate system. represents the desired heading angle of the aircraft relative to the inertial reference coordinate system, Indicates the aircraft's deviation distance.

[0092] It should be noted that the inertial reference coordinate system is stationary or in uniform linear motion relative to stars or distant galaxies. The actual heading angle of the aircraft body relative to the inertial reference coordinate system is the direction of the body relative to the earth during actual flight. The aircraft body fixed coordinate system is a three-dimensional orthogonal rectangular coordinate system fixed to the aircraft that follows the right-hand rule, and the origin is usually located at the center of mass of the aircraft.

[0093] The transformation matrix between the inertial reference coordinate system and the aircraft body fixed coordinate system is defined as shown in formula (1):

[0094] (1)

[0095] in, , Indicates the yaw angle of the aircraft. and Respectively Axis and The unit vector in the direction of the axis, and Respectively Axis and Unit vector in the direction of the axis.

[0096] Depend on Figure 3 It can be seen that:

[0097]

[0098] (2)

[0099] in, Describing the expected trajectory The first derivative with respect to time, Indicates time.

[0100] From formula (2), we can get:

[0101] (3)

[0102] in, express The first derivative with respect to time, express The first derivative with respect to time, Describing the expected trajectory exist The curvature of the .

[0103] Formula (2) can also be expressed as:

[0104] (4)

[0105] in, Indicates the lateral speed of the aircraft. It should be noted that the arrows in equations (2), (3) and (4) all represent vectors.

[0106] From formula (3) and formula (4), we can get:

[0107] (5)

[0108] Assume the aircraft's yaw angle Smaller, that is , , then formula (5) can be simplified as:

[0109] (6)

[0110] In addition, the yaw angle of the aircraft Taking the derivative, equation (6) can be expressed as equation (7):

[0111] (7)

[0112] in, express The first derivative with respect to time, express The first derivative with respect to time, Represents the yaw angular velocity.

[0113] like Figure 4 As shown in the figure, it is the lateral force diagram of the aircraft during taxiing. Figure 5 The figure shows the force diagram of the aircraft when taxiing from a bird's-eye view. Figure 4 middle, represents lift, represents wind resistance, Indicates the distance from the center of the body to the ground. represents the vertical distance from the residual thrust to the center of gravity, Indicates the ground's support force on the left main wheel. It represents the ground support force on the right main wheel. Indicates the support force of the ground on the front wheel. represents the angular velocity of the left main wheel, represents the angular velocity of the right main wheel, Represents the gravity of the aircraft. Assuming that the left and right main wheels of the aircraft have the same lateral stiffness and always turn at the same angle, according to Newton's second law and the law of rigid body rotation, we can get:

[0114] (8)

[0115] in, is the rudder force, represents the lateral force on the front wheel, Indicates the lateral force of the left main wheel, represents the lateral force of the right main wheel, represents the crosswind disturbance force, Indicates the mass of the aircraft, express The first derivative with respect to time, Indicates the projection distance from the rudder to the center of gravity of the aircraft ( Figure 2 middle arrive ), Indicates the projection distance from the front wheel to the center of gravity of the aircraft, Indicates the projection distance from the left main wheel and the right main wheel to the center of gravity of the aircraft. Indicates the ground force of the left main wheel. Indicates the ground force of the right main wheel, represents the projected distance between the left main wheel and the right main wheel, represents the aircraft's moment of inertia, express The first derivative with respect to time.

[0116] Left main wheel ground force The right main wheel ground force It can be expressed as:

[0117] (9)

[0118] in, Indicates the left main wheel support force, Indicates the right main wheel support force, represents the combination coefficient of the left main wheel, Indicates the coupling coefficient of the right main gear.

[0119] Front wheel lateral force , lateral force of left main wheel and the right main wheel lateral force It can be approximately expressed as:

[0120] (10)

[0121] in, It represents the cornering stiffness of the front wheel when the sideslip angle is zero. It represents the cornering stiffness of the left and right main wheels when the slip angle is zero. represents the front wheel slip angle, Indicates the left main wheel slip angle, Indicates the right main wheel slip angle.

[0122] Indicates the front wheel slip angle , indicates the left main wheel slip angle and represents the right main wheel slip angle It can be specifically expressed as:

[0123] (11)

[0124] in, represents the steering angle of the front wheels, Indicates the steering angle of the left and right main wheels.

[0125] Crosswind disturbance force and rudder force It can be expressed as:

[0126] (12)

[0127] in, represents the air density, represents the aircraft yaw coefficient, represents the rudder angle, represents the crosswind speed, represents the crosswind coefficient, represents the wing area, Indicates the tail rudder area.

[0128] Combining equations (6), (7) and (8), the aircraft ground coordinated turning system model is established:

[0129] (13)

[0130] in, represents the force of the rudder on the main wheel, Indicates the force of the rudder on the front wheel.

[0131] Rudder force on main wheel and the rudder force on the front wheel It can be expressed as:

[0132] (14)

[0133] In order to facilitate the design of the subsequent aircraft ground coordinated turning controller, equation (13) can be rewritten into the following form:

[0134] (15)

[0135] Among them, the system state quantity , system control input , , , , , , , express The first derivative with respect to time.

[0136] As an example, the following parameter value combinations can be used: , , , , , , , , , , .

[0137] S202, design the front wheel-main wheel coordinated turning composite sliding surface.

[0138] During the ground turning process of the aircraft, the control goal of the aircraft ground coordinated turning system is to enable the aircraft to move along the predetermined trajectory by accurately controlling the steering angles of the front wheels and main wheels. In other words, the aircraft ground coordinated turning control can essentially be regarded as a trajectory tracking control problem.

[0139] To achieve accurate tracking and control of the aircraft trajectory, the aircraft's yaw distance is required , and the aircraft's yaw angle It approaches zero in a short time. Therefore, the front wheel-main wheel cooperative turning composite sliding surface can be defined as:

[0140] (16)

[0141] in, represents the yaw distance sliding surface, represents the yaw angle sliding surface, represents the sliding surface parameters of the yaw distance to be designed, = , = , = , = , Represents the sliding surface parameters of the yaw angle to be designed. and The value of can be 10, and the specific value is selected to satisfy the Hurwitz (Hurwitz refers to the Hurwitz stability criterion, which is a mathematical tool) of the aircraft ground coordinated turning system.

[0142] S203, design a front wheel-main wheel coordinated turning control law.

[0143] Derivative the front wheel-main wheel coordinated turning composite sliding surface expression (16), take the exponential approach rate, and substitute equation (15) into it to obtain:

[0144] (17)

[0145] (18)

[0146] in, express The first derivative with respect to time, express The first derivative with respect to time, express The first derivative with respect to time, express The first derivative with respect to time, express The first derivative with respect to time.

[0147] By combining equations (17) and (18), we can get the front wheel-main wheel coordinated turning control law as:

[0148] (19)

[0149] in, represents the first intermediate parameter, Represents the second intermediate parameter.

[0150]

[0151] .

[0152] The aircraft's ground coordinated turning is controlled according to the control law.

[0153] The simulation was performed based on MATLAB software, and the sampling time was set to 0.001s. The simulation results are as follows Figures 6 to 10 shown. Figure 6 is the yaw distance curve of the coordinated turning control under fixed initial conditions, Figure 7is the yaw angle curve of the aircraft under coordinated turning control under fixed initial conditions, Figure 8 is the motion trajectory curve of cooperative turning control under fixed initial conditions, Fig. 9 It is the trajectory tracking curve diagram of the coordinated turning control at different longitudinal speeds. Fig.10 The following is the trajectory tracking curve of the coordinated turning control under different initial aircraft yaw angles. The fixed initial conditions are: the aircraft yaw distance is 5m, the aircraft yaw angle is 20°, and the aircraft lateral speed is 5m / s. Figure 6 and Figure 7 It can be seen from the figure that the present application can effectively control the yaw distance and the yaw angle of the aircraft to near zero in a relatively short period of time, which also shows that the present application can control the aircraft to taxi along the expected trajectory in a short period of time. Figure 8 It can be seen that the error of aircraft trajectory tracking eventually approaches zero, showing a significant control effect in achieving the expected trajectory. Fig. 9 It can be seen that under low-speed conditions, the aircraft can quickly and accurately track the expected trajectory and show a small tracking error. This also shows that under low-speed conditions, the aircraft ground coordinated turning system has good trajectory tracking control performance. However, as the aircraft's longitudinal speed increases, the curve radius of the aircraft's ground turn increases significantly, causing the aircraft's ground coordinated turning system to require more response time to achieve tracking of the expected trajectory. At the same time, the corresponding trajectory tracking error also gradually increases. Therefore, in the actual aircraft ground taxiing and turning process, in order to improve the overall control performance of the aircraft ground coordinated turning system, it is necessary to ensure that the aircraft is taxiing and turning at a lower longitudinal speed. From Fig.10 It can be seen that under different initial aircraft yaw angles, the aircraft ground coordinated turning system can achieve efficient tracking of the expected trajectory, and the tracking error can also be controlled within a reasonable range.

[0154] Based on the above-mentioned sliding mode control method of aircraft ground coordinated turning system, Fig.11 As shown, the present application also proposes a sliding mode control system for an aircraft ground coordinated turning system, which may include:

[0155] Acquisition module, used to obtain real-time parameters of the aircraft;

[0156] A control module, for controlling the state of the aircraft ground coordinated turning system on the front wheel-main wheel coordinated turning composite sliding surface through the front wheel-main wheel coordinated turning control law based on the real-time parameters of the aircraft;

[0157] The state of the aircraft ground coordinated turning system includes the steering angles of the left main wheel and the right main wheel, and the steering angle of the front wheel;

[0158] The control target of the nose wheel-main wheel coordinated turning composite sliding surface is that the yaw distance and the yaw angle of the aircraft approach zero within a preset time;

[0159] The front wheel-main wheel coordinated turning control law acquisition method comprises:

[0160] The front wheel-main wheel coordinated turning composite sliding surface is derived, and combined with the aircraft ground coordinated turning system model, the front wheel-main wheel coordinated turning control law is determined; the system state quantities of the aircraft ground coordinated turning system model include the aircraft's yaw distance, the aircraft's yaw angle, the aircraft's longitudinal speed and the yaw angular velocity.

[0161] It should be noted that in the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of each module is only a logical function division. There may be other division methods in actual implementation. For example, multiple modules can be combined or integrated into another device, or some features can be ignored or not executed. The module described as a separate component may or may not be physically separated. The component displayed as a module may be a physical unit or multiple physical units, that is, it may be located in one place, or it may be distributed in multiple different places. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment.

[0162] In addition, each module in each embodiment of the present invention may be integrated into a processing unit, each module may exist physically separately, or two or more modules may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0163] In addition, the present application also proposes an aircraft ground coordinated turning system, including a controller and an aircraft ground coordinated turning system body; wherein the controller controls the aircraft ground coordinated turning system body according to the above-mentioned aircraft ground coordinated turning system sliding mode control method.

[0164] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A sliding mode control method for an aircraft ground coordinated turning system, characterized in that: include: Get real-time aircraft parameters; Based on the real-time parameters of the aircraft, the state of the aircraft ground coordinated turning system is controlled on the nose wheel-main wheel coordinated turning composite sliding surface through the nose wheel-main wheel coordinated turning control law; The front wheel-main wheel coordinated turning control law includes: in, represents the first intermediate parameter, represents the second intermediate parameter, represents the yaw distance sliding surface, represents the yaw angle sliding surface; in, , , , ; The front wheel-main wheel cooperative turning composite sliding surface comprises: in, represents the yaw distance sliding surface, represents the yaw angle sliding surface, represents the sliding surface parameters of the yaw distance to be designed, , , , , represents the sliding surface parameters of the yaw angle to be designed; The state of the aircraft ground coordinated turning system includes the steering angles of the left main wheel and the right main wheel, and the steering angle of the front wheel; The control target of the nose wheel-main wheel coordinated turning composite sliding surface is that the yaw distance and the yaw angle of the aircraft approach zero within a preset time; The front wheel-main wheel coordinated turning control law acquisition method comprises: The nose wheel-main wheel coordinated turning composite sliding mode surface is derived, and the nose wheel-main wheel coordinated turning control law is determined in combination with the aircraft ground coordinated turning system model; the system state quantity of the aircraft ground coordinated turning system model includes the aircraft's yaw distance, the aircraft's yaw angle, the aircraft's longitudinal speed and the yaw angular velocity; The aircraft ground coordinated turning system model includes: in, express The first derivative with respect to time, Indicates the lateral speed of the aircraft. Indicates the yaw angle of the aircraft. It represents the longitudinal speed of the aircraft. express The first derivative with respect to time, represents the yaw angular velocity, Describing the expected trajectory exist The curvature of represents the desired position of the aircraft's center of gravity, Indicates the aircraft's yaw distance, express The first derivative with respect to time, is the rudder force, represents the force of the rudder on the main wheel, is the force of the rudder on the front wheel, represents the crosswind disturbance force, Indicates the mass of the aircraft, It represents the cornering stiffness of the left and right main wheels when the slip angle is zero. Indicates the steering angle of the left and right main wheels, It represents the cornering stiffness of the front wheel when the sideslip angle is zero. represents the steering angle of the front wheels, represents the first-order derivative with respect to time , It represents the projection distance from the rudder to the center of gravity of the aircraft. Indicates the projection distance from the left main wheel and the right main wheel to the center of gravity of the aircraft. Indicates the projection distance from the front wheel to the center of gravity of the aircraft, represents the projected distance between the left main wheel and the right main wheel, represents the aircraft's moment of inertia, Indicates the ground force of the left main wheel. Indicates the ground force of the right main wheel.

2. The sliding mode control method of the aircraft ground coordinated turning system according to claim 1, characterized in that: The aircraft ground coordinated turning system model, the nose wheel-main wheel coordinated turning composite sliding surface and the nose wheel-main wheel coordinated turning control law are all determined based on the aircraft trajectory tracking coordinate system; The aircraft trajectory tracking coordinate system includes an inertial reference coordinate system, an aircraft body fixed coordinate system, and a coordinate system defined by a desired trajectory.

3. A sliding mode control system for an aircraft ground coordinated turning system, characterized in that: include: Acquisition module, used to obtain real-time parameters of the aircraft; A control module, for controlling the state of the aircraft ground coordinated turning system on the front wheel-main wheel coordinated turning composite sliding surface through the front wheel-main wheel coordinated turning control law based on the real-time parameters of the aircraft; The front wheel-main wheel coordinated turning control law includes: in, represents the first intermediate parameter, represents the second intermediate parameter, represents the yaw distance sliding surface, represents the yaw angle sliding surface; in, , , , ; The front wheel-main wheel cooperative turning composite sliding surface comprises: in, represents the yaw distance sliding surface, represents the yaw angle sliding surface, represents the sliding surface parameters of the yaw distance to be designed, , , , , represents the sliding surface parameters of the yaw angle to be designed; The state of the aircraft ground coordinated turning system includes the steering angles of the left main wheel and the right main wheel, and the steering angle of the front wheel; The control target of the nose wheel-main wheel coordinated turning composite sliding surface is that the yaw distance and the yaw angle of the aircraft approach zero within a preset time; The front wheel-main wheel coordinated turning control law acquisition method comprises: The nose wheel-main wheel coordinated turning composite sliding mode surface is derived, and the nose wheel-main wheel coordinated turning control law is determined in combination with the aircraft ground coordinated turning system model; the system state quantity of the aircraft ground coordinated turning system model includes the aircraft's yaw distance, the aircraft's yaw angle, the aircraft's longitudinal speed and the yaw angular velocity; The aircraft ground coordinated turning system model includes: in, express The first derivative with respect to time, Indicates the lateral speed of the aircraft. Indicates the yaw angle of the aircraft. It represents the longitudinal speed of the aircraft. express The first derivative with respect to time, represents the yaw angular velocity, Describing the expected trajectory exist The curvature of represents the desired position of the aircraft's center of gravity, Indicates the aircraft's yaw distance, express The first derivative with respect to time, is the rudder force, represents the force of the rudder on the main wheel, is the force of the rudder on the front wheel, represents the crosswind disturbance force, Indicates the mass of the aircraft, It represents the cornering stiffness of the left and right main wheels when the slip angle is zero. Indicates the steering angle of the left and right main wheels, It represents the cornering stiffness of the front wheel when the sideslip angle is zero. represents the steering angle of the front wheels, represents the first-order derivative with respect to time , It represents the projection distance from the rudder to the center of gravity of the aircraft. Indicates the projection distance from the left main wheel and the right main wheel to the center of gravity of the aircraft. Indicates the projection distance from the front wheel to the center of gravity of the aircraft, represents the projected distance between the left main wheel and the right main wheel, represents the aircraft's moment of inertia, Indicates the ground force of the left main wheel. Indicates the ground force of the right main wheel.

4. The sliding mode control system of the aircraft ground coordinated turning system according to claim 3, characterized in that: The aircraft ground coordinated turning system model, the nose wheel-main wheel coordinated turning composite sliding surface and the nose wheel-main wheel coordinated turning control law are all determined based on the aircraft trajectory tracking coordinate system; The aircraft trajectory tracking coordinate system includes an inertial reference coordinate system, an aircraft body fixed coordinate system, and a coordinate system defined by a desired trajectory.

5. An aircraft ground coordinated turning system, comprising a controller and an aircraft ground coordinated turning system body; characterized in that: The controller controls the aircraft ground coordinated turning system body according to the sliding mode control method of the aircraft ground coordinated turning system according to any one of claims 1 to 4.

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