An aircraft cross-direction fault-tolerant control and reconstruction method and system under failure of a rudder surface

Abstract

The application provides a horizontal flight direction fault-tolerant control and reconstruction method for an aircraft under rudder surface failure, designs a horizontal flight direction fault-tolerant controller, calculates an optimal control law through a nominal model of the aircraft and a rudder surface failure model, and stabilizes the aircraft under external disturbance. Then, a quadruple neural network is used to estimate the optimal control law for all possible failure degrees. When the rudder surface failure occurs, the aircraft can be stably operated. The application provides a horizontal flight direction fault-tolerant control and reconstruction system for an aircraft under rudder surface failure, which is not limited in generality, based on a fault detection and isolation module, a switching mechanism and a flight control system, introduces a horizontal flight direction fault-tolerant controller, and stabilizes the aircraft under external disturbance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of flight control, and particularly relates to a method and system for lateral-directional fault-tolerant control and reconstruction of an airplane under failure of a rudder surface. BACKGROUND

[0002] The probability of failure of a rudder surface is relatively high for an airplane controlled by a rudder with a multi-control surface arrangement and a large deflection resistance in the lateral-directional plane. The flight control system needs to be reconfigured after failure of the rudder. In view of the failure of the rudder surface, a failure model of the rudder surface of the airplane needs to be analyzed. Since the airplane has a multi-control surface and adopts a dynamic inversion flight control law, the airplane has a control distribution module. By modifying the module, lateral-directional fault-tolerant control and system reconstruction of the airplane are realized in the above-mentioned failure of the rudder. In the case of limited failure of the rudder surface and a decrease in the flight quality level, the airplane adopts the flight control method based on the proposed fault-tolerant control and reconstruction system, so as to ensure flight safety and complete certain flight tasks.

[0003] From the perspective of control theory, detection and control of unwanted changes, referred to as faults, play a crucial role in the safety of an airplane system. Faults can occur in all parts of the control system, such as actuators, sensors and equipment structures. There are two main fault-tolerant control and reconstruction methods, namely passive fault-tolerant control and reconstruction and active fault-tolerant control and reconstruction. In the passive fault-tolerant control and reconstruction method, there is no fault detection, and a fault isolation module and a controller are redesigned to make the closed-loop system robust to faults. In contrast, in the active fault-tolerant control and reconstruction method, faults are first detected and isolated with the help of a fault detection and isolation module, and then control compensation is performed by a fault-tolerant control and reconstruction system. Unlike the active fault-tolerant control and reconstruction method, this method can compensate for a wide range of faults. SUMMARY

[0004] The application aims to overcome the shortcomings of the prior art and provide a method and system for lateral-directional fault-tolerant control and reconstruction of an airplane under failure of a rudder surface.

[0005] To achieve the above object, the application adopts the following technical solutions:

[0006] A method for lateral-directional fault-tolerant control and reconstruction of an airplane under failure of a rudder surface, comprising the following steps:

[0007] (1) establishing a nominal linearized model of the airplane without failure of the rudder surface and a lateral motion model of the airplane under failure of the rudder surface;

[0008] (2) Design an active fault-tolerant control law of the disturbance observer based on the nominal linear model of the aircraft without rudder surface failure and the lateral motion model of the aircraft in the state of rudder surface failure, measure the real disturbance by using the disturbance observer, calculate the estimated disturbance by using the Riccati equation and the regular matrix equation, so that the error between the estimated disturbance and the real disturbance measured by the disturbance observer is within the preset range, and obtain the active fault-tolerant control law of the aircraft in the normal state;

[0009] Then, a quadruple neural network is used to solve the parameters of the active fault-tolerant control law under each rudder surface failure degree, and finally the complete active fault-tolerant control law is obtained.

[0010] (3) When the rudder surface failure occurs, the hydraulic actuator of the aircraft loses pressure, the fault detection and isolation module sends a signal to the actuator switching module and the active fault-tolerant control law, the active fault-tolerant control law calculates the required control input, the actuator switching module switches to the electro-hydraulic actuator after receiving the signal and transmits the required control input to the electro-hydraulic actuator, and the electro-hydraulic actuator provides the required control input.

[0011] Further, in step (1), the nominal linear model of the aircraft without rudder surface failure is established, which is specifically:

[0012]

[0013] In the formula, x = [β, ρ, r, φ], where φ and ρ are the roll angle and roll angle rate respectively, r is the yaw angle rate, and β is the side slip angle; u H = [δ aH , δ rH ] T is a matrix composed of control input vectors respectively given by hydraulic actuators in ailerons and rudders, δ aH is a control input vector given by a hydraulic actuator in an aileron; δ rH is a control input vector given by a hydraulic actuator in a rudder; f(t) represents external disturbance; the system matrix in formula (1) is defined as:

[0014]

[0015]

[0016] C = [0 0 0 1]

[0017] D = [0 0 0 1]

[0018] In the formula, where I x , I z and I zxare the moment about x and z axes and the moment product about (x,z) axes respectively; u0is the initial control input of the aircraft; m is the mass of the aircraft; g0is the gravity constant; θ0is the reference climb angle; N r , N β and N p are the yawing moments about three stable axes respectively; L r , L β and L p are the rolling moments about three stable axes respectively; Y r , Y β and Y p are the lateral aerodynamic forces about three stable axes respectively; and are the yawing moments provided by rudder and aileron; and are the lateral aerodynamic forces provided by rudder and aileron.

[0019] Further, in step (1), the aircraft rudder surface failure model is established as:

[0020]

[0021] wherein μ ∈ [0, 1] represents the vertical tail damage degree, u E = [δ aE , δ rE ] T is the control input vector provided by the electro-hydraulic actuator driving the rudder surface rotation, and u E is the control input provided by the electro-hydraulic actuator when the rudder surface failure occurs;

[0022] The change of the system matrix in formula (3) is:

[0023]

[0024]

[0025] Further, in step (2), the acquisition process of the active fault-tolerant control law of the aircraft in normal condition is:

[0026]

[0027] In formula (5), and are positive definite matrices;

[0028] The optimal control law minimizing the control cost index is:

[0029]

[0030] K(t) in formula (6) is:

[0031]

[0032] wherein, is the disturbance vector measured by the disturbance observer; P1 and P2 are the unique solutions of the following Riccati equation and regular matrix equation respectively:

[0033]

[0034] wherein, and

[0035] The disturbance vector is measured by the disturbance observer:

[0036]

[0037] wherein, is a positive definite matrix, is the internal state vector of the disturbance observer;

[0038] The P1 and P2, and the state quantity of the rudder surface failure model of the aircraft are substituted into equation (6) to obtain the active fault-tolerant control law of the aircraft in normal condition.

[0039] Further, the four-layer neural network is used to solve the parameters of the active fault-tolerant control law in step (2), and finally the complete active fault-tolerant control law is obtained, which is specifically:

[0040] For different rudder surface failure degrees μ, the four-layer neural network is used to learn and estimate and

[0041]

[0042] The active fault-tolerant control law under different rudder surface failures is obtained by combining equations (6) and (10):

[0043]

[0044] Further, the four-layer neural network is composed of two neural network hidden layers and one neural network output layer, the activation function of the hidden layer is a Sigmoid function, and the activation function of the output layer is a linear function.

[0045] An aircraft lateral fault-tolerant control and reconstruction system under rudder surface failure, comprising a fault detection and isolation module, an aircraft lateral fault-tolerant controller, an actuator switching module, a hydraulic actuator and an electro-hydraulic actuator;

[0046] When the rudder surface failure occurs, the hydraulic actuator of the aircraft loses pressure, the fault detection and isolation module sends a fault signal to the actuator switching module and the aircraft lateral fault-tolerant controller, the aircraft lateral fault-tolerant controller outputs the required control input, and the actuator switching module switches to the electro-hydraulic actuator after receiving the fault signal and transmits the required control input to the actuator switching module, and the actuator switching module provides the required control input.

[0047] Further, the aircraft lateral fault-tolerant controller is designed by the following design method:

[0048] (1) Establish a nominal linear model of the aircraft without rudder surface failure and a lateral motion model of the aircraft in the state of rudder surface failure;

[0049] (2) Design an active fault-tolerant control law of a disturbance observer based on the nominal linear model of the aircraft without rudder surface failure and the lateral motion model of the aircraft in the state of rudder surface failure, the disturbance observer is used to measure the real disturbance, and the Riccati equation and the regular matrix equation are used to calculate the estimated disturbance, so that the error between the estimated disturbance and the real disturbance measured by the disturbance observer is within a preset range, and an active fault-tolerant control law of the aircraft in a normal state is obtained;

[0050] Then, a quadruple neural network is used to solve the parameters of the active fault-tolerant control law under each rudder surface failure degree, and finally a complete active fault-tolerant control law is obtained.

[0051] Compared with the prior art, the present application has the following beneficial effects:

[0052] The present application provides a kind of aircraft lateral fault-tolerant control and reconstruction method under rudder surface failure, design aircraft lateral fault-tolerant controller, through the nominal model of aircraft and rudder surface failure model, calculate optimal control law, to stabilize aircraft in the presence of external disturbance. Then, using quadruple neural network to estimate the optimal control law for all possible failure degrees. When the rudder surface failure occurs, the smooth operation of the aircraft can be realized.

[0053] The present application provides a kind of aircraft lateral fault-tolerant control and reconstruction system under rudder surface failure, without loss of generality, based on the presence of fault detection and isolation module, switching mechanism and flight control system, aircraft lateral fault-tolerant controller is introduced, to stabilize aircraft in the presence of external disturbance. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is a schematic diagram of the aircraft with rudder surface failure condition;

[0055] Figure 2 is a schematic diagram of quadruple neural network;

[0056] Figure 3 The specific architecture diagram of the aircraft lateral direction fault-tolerant control and reconstruction system under the rudder surface failure.

[0057] Figure 4 The lateral flight model output of the aircraft model under the normal condition;

[0058] Figure 5 The roll angle output by the application, the roll angle output by the model reference control, and the roll angle output by the passive fault-tolerant control under μ=0.9;

[0059] Figure 6 The sideslip angle output by the application, the sideslip angle output by the model reference control, and the sideslip angle output by the passive fault-tolerant control under μ=0.9;

[0060] Figure 7 The roll angle output by the application and the roll angle output by the model reference control under μ=1;

[0061] Figure 8 The sideslip angle output by the application and the sideslip angle output by the model reference control under μ=1;

[0062] Figure 9 The aileron angle output by the application and the aileron angle output by the model reference control under μ=1.

[0063] Wherein, 1 is the rudder surface failure part, 2 is the normal rudder surface part, 3 is the neural network hidden layer, and 4 is the neural network output layer. DETAILED DESCRIPTION

[0064] In order for those skilled in the art to better understand the application scheme, the technical solutions in the embodiments of the application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the application.

[0065] It is to be understood that the terms "first", "second", and the like, used in the description and the claims of the present application as well as the above-mentioned drawings, are used to distinguish between similar objects, not necessarily described in a particular sequential or chronological order. It is to be understood that the use of data, which is made herein, can be interchanged, where appropriate, to enable the embodiments of the application described herein to be carried out in other than the order shown or described herein. Furthermore, the terms "comprise" and "comprising" and any variation thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or apparatus that comprises a list of steps or units can not necessarily be limited to those steps or units which are expressly listed, but can include additional steps or units that are not expressly listed or inherent to such process, method, product or apparatus.

[0066] The application will be further described in details below with reference to the accompanying drawings:

[0067] The application proposes a rudder surface failure under the aircraft lateral direction fault-tolerant control and reconstruction method, which is applied in the scene of existing fault detection and isolation module, switching mechanism and feedforward performance degradation compensator without losing generality. The specific architecture of the aircraft lateral direction fault-tolerant control and reconstruction system under the rudder surface failure is as shown in the figure. Figure 3 When the rudder surface failure occurs, the hydraulic actuator of the aircraft loses pressure, the fault detection and isolation module sends a signal to the actuator switching module and the aircraft lateral direction fault-tolerant controller, the aircraft lateral direction fault-tolerant controller calculates the required control input, the actuator switching module switches to the electro-hydraulic actuator after receiving the signal and transmits the required control input to the electro-hydraulic actuator, and the electro-hydraulic actuator provides the required control input to the aircraft.

[0068] The main focus of the application is the design of the aircraft lateral direction fault-tolerant controller. The implementation means of the application is to obtain the nominal model and the rudder surface failure model of the aircraft. First, the optimal control law is calculated to stabilize the aircraft in the presence of external disturbances. Then, the optimal control law is estimated by using a neural network for all possible failure degrees.

[0069] The implementation of the aircraft lateral direction fault-tolerant control and reconstruction method under the rudder surface failure of the application is as follows:

[0070] A linearized model of the aircraft without rudder surface failure is extracted around a certain stable flight operating point, which is described as follows:

[0071]

[0072] In the formula, x = [β, ρ, r, φ], wherein φ and ρ are respectively the roll angle and roll angle rate, r is the yaw angle rate, and β is the side slip angle; u H = [δ aH , δrH ] T are the control input vectors given by the hydraulic actuators in the ailerons and rudder respectively, f(t) represents external disturbances. The system matrix in equation (1) is defined as:

[0073]

[0074]

[0075] C = [0 0 0 1]

[0076] D = [0 0 0 1]

[0077] where, where I x , I z and I zx are the moments about the x, z axes and the product of moments about the (x, z) axes respectively. u0is the initial control input of the aircraft. m is the mass of the aircraft; g0is the gravitational constant; θ0is the reference climb angle; N r , N β and N p are the yawing moments about the three stable axes; L r , L β and L p are the rolling moments about the three stable axes; Y r , Y β and Y p are the lateral aerodynamic forces about the three stable axes; and are the yawing moments provided by the rudder and ailerons; and are the lateral aerodynamic forces provided by the rudder and ailerons.

[0078] Further considering the failure of the rudder surface of the aircraft, a failure model of the rudder surface of the aircraft is established:

[0079]

[0080] where μ ∈ [0, 1] represents the damage degree of the vertical tail, u E = [δ aE , δ rE ] T is the control input vector provided by the electro-hydraulic actuator driving the rudder surface to rotate; when the failure of the rudder surface occurs, the hydraulic actuator loses pressure and cannot provide the required control input, i.e. u H in equation (1). Therefore, the fault detection and isolation module will send a signal to the actuator switching module to switch to the electro-hydraulic actuator to provide the required control input, i.e. u EThe change of the system matrix in equation (3) can be calculated by the following equation:

[0081]

[0082]

[0083] The effect of rudder surface failure in equation (3) can be explained as a process fault. Further, an active fault-tolerant control strategy will be developed to mitigate the effect of the process fault on the lateral flight of the aircraft.

[0084] To design the control law for the failure-free aircraft model in equation (1), the following control cost index is designed:

[0085]

[0086] In equation (5), and are positive definite matrices. Set the error e = r - y, where r is the reference signal, so Then the optimal control law that minimizes the control cost index in equation (5) can be further obtained as:

[0087]

[0088] K(t) in equation (6) is:

[0089]

[0090] where, is the disturbance vector measured by the disturbance observer; P1 and P2 are the unique solutions of the following Riccati equation and regular matrix equation, respectively:

[0091]

[0092] where and

[0093] Further, the disturbance vector is measured by the disturbance observer:

[0094]

[0095] where is a positive definite matrix, is the internal state vector of the disturbance observer.

[0096] In the case of rudder surface failure, it is obvious from equation (3) that for a specific rudder surface failure degree μ, there will be a new system matrix. Therefore, for a specific rudder surface failure degree, equation (6) considers the state quantity x under the specific rudder surface failure degree in equation (3). Therefore, the fault-tolerant control law can be calculated using the optimal control method described above for each rudder surface failure degree. To accomplish this task, for each μ, equation (6) is solved to obtain the control input u. and The estimation of the quadruple neural network is learned by:

[0097]

[0098] The above equations are the quadruple neural networks, i.e., N1(μ), N2(μ), N3(μ), and N4(μ). The type and structure are referred to Figure 2 The activation functions of the hidden layer and the output layer are sigmoid function and linear function, respectively. The flight data acquisition module provides the learning data required by the quadruple neural network, which collects the flight state and input data of the aircraft under normal conditions and rudder surface failure conditions. Figure 2 W and b in equation (10) represent the weight and bias matrices of each layer. After learning the estimation parameters of the quadruple neural network, the aircraft lateral fault-tolerant control and reconstruction system under rudder surface failure is obtained by combining equations (6) and (10):

[0099]

[0100] When the rudder surface fails, the aircraft's hydraulic actuators lose pressure, and the fault detection and isolation module sends a signal to the actuator switching module and the aircraft lateral fault-tolerant controller, which calculates the required control input. The actuator switching module receives the signal and switches to the electric hydraulic actuator and transmits the required control input to the actuator switching module, which provides the required control input to the aircraft.

[0101] Example 1: Nominal condition for μ = 0. In this case, the rudder surface is not damaged, so the rudder surface is driven by the hydraulic actuator. The lateral flight model output of the nominal aircraft model is shown in Figure 4 It can be seen that the roll angle and sideslip angle of the aircraft can stably follow the roll command and sideslip command given by the designed controller.

[0102] Example 2: Severe rudder surface damage. μ = 0.9 In this case, all hydraulic actuators will lose pressure, and through the switching mechanism, these actuators will be replaced by electric hydraulic actuators. Figure 5It is shown that the roll angle in the passive fault-tolerant control method not only cannot track the roll command, but also becomes infinite in the steady state. Similar poor tracking performance exists in the model reference adaptive control method, while the proposed method has good tracking performance in the presence of large external disturbances. Based on Figure 6 Compared with the other two methods, the proposed method can more effectively limit the sideslip angle to the vicinity of the zero signal.

[0103] Example 3: Rudder surface loss. μ = 1 In this case, the rudder can no longer drive the aircraft, and the control input is only provided by the ailerons. In this case, the proposed method and the MRAC method are considered. Figure 7 and Figure 8 It is shown that the proposed method is superior to the model reference adaptive control method in terms of roll angle tracking performance and sideslip angle zero signal tracking performance, respectively. Figure 9 It is shown that the proposed method has a huge advantage over the model reference adaptive control method, i.e. the required control input provided by the ailerons is much smaller than that of the model reference adaptive control method. This advantage is obvious in dangerous flight conditions.

[0104] The above merely illustrates the technical idea of the present application and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical solution falls within the protection scope of the claims of the present application.

Claims

1. A method for fault-tolerant control and reconfiguration of an aircraft in lateral direction under rudder surface failure, characterized in that, Includes the following steps: (1) Establish a nominal linearized model of the aircraft without rudder control surface failure and a model of the aircraft's lateral motion under rudder control surface failure conditions. (2) Based on the nominal linearized model of the aircraft without rudder control surface failure and the aircraft lateral motion model under rudder control surface failure state, design the active fault-tolerant control law of the disturbance observer. Using the real disturbance measured by the disturbance observer, calculate the estimated disturbance using the Riccati equation and the regular matrix equation, so that the error between the estimated disturbance and the real disturbance measured by the disturbance observer is within the preset range, and obtain the active fault-tolerant control law of the aircraft under normal conditions. Then, a quadruple neural network was used to solve the parameters of the active fault-tolerant control law under the failure degree of the rudder surface in each direction, and finally the complete active fault-tolerant control law was obtained. (3) When the rudder surface fails, the aircraft's hydraulic actuator loses pressure. The fault detection and isolation module sends a signal to the actuator switching module and the active fault-tolerant control law. The active fault-tolerant control law calculates the required control input. After receiving the signal, the actuator switching module switches to the electro-hydraulic actuator and transmits the required control input to the electro-hydraulic actuator. The electro-hydraulic actuator provides the required control input. In step (1), the nominal linearized model for the failure of the rudderless control surface of the aircraft is established as follows: （1） In the formula, ,in and These are the roll rate and the pitch rate, respectively. The yaw rate, Sideslip angle; It is a matrix composed of control input vectors given by the hydraulic actuators in the ailerons and rudder, respectively. The control input vector given to the aileron hydraulic actuator; The control input vector given to the hydraulic actuator in the rudder; Represents external disturbance; the system matrix in equation (1) is defined as: In the formula, , , ,in , and They are axis, Torque on the shaft and The product of torques on the shaft; This serves as the initial control input for the aircraft. It refers to the mass of the aircraft; It is the gravitational constant; For reference climb angle; , and These are the yaw moments on the three stability axes; , and These are the rolling torques on the three stabilizing axes; , and These are the lateral aerodynamic forces on the three stability axes; and The yaw moment is provided by the rudder and ailerons; and The lateral aerodynamic forces are provided by the rudder and ailerons; In step (1), the failure model of the aircraft rudder surface is established as follows: （3） in, Indicates the extent of damage to the vertical tail fin. It is the control input vector provided by the electro-hydraulic actuator that drives the rotation of the rudder surface; when rudder surface failure occurs... Control inputs provided for electro-hydraulic actuators; The change of the system matrix in equation (3) is as follows: （4） The process of obtaining the active fault-tolerant control law for the normal aircraft condition in step (2) is as follows: （5） In equation (5), and It is a positive definite matrix; set the error. ,in It is the reference signal, in equation (5) ; The optimal control law that minimizes the control cost index is: （6） In equation (6) for: （7） in, It is the disturbance vector measured by the disturbance observer; and These are the unique solutions to the following Riccati equation and regular matrix equation: （8） in, and ; Measure the disturbance vector using a disturbance observer: （9） in, It is a positive definite matrix. It is the internal state vector of the perturbation observer; The and , Substituting the state variables of the aircraft rudder surface failure model into equation (6), we obtain the active fault-tolerant control law for normal aircraft conditions.

2. The method for fault-tolerant control and reconfiguration of aircraft lateral heading under rudder surface failure as described in claim 1, characterized in that, In step (2), a quadruple neural network is used to solve for the parameters of the active fault-tolerant control law, ultimately obtaining the complete active fault-tolerant control law, specifically: The degree of failure of rudder surfaces in different directions The estimation formula (6) is learned by the four-fold neural network. and ; （10） Combining equations (6) and (10), we obtain the active fault-tolerant control law under different rudder surface failure conditions: （11）。 3. The aircraft lateral fault-tolerant control and reconfiguration method under rudder surface failure as described in claim 2, characterized in that, The quadruple neural network consists of two hidden layers and one output layer. The activation function of the hidden layer is a sigmoid function, and the activation function of the output layer is a linear function.

4. A fault-tolerant control and reconfiguration system for lateral heading of an aircraft under rudder surface failure, characterized in that, The system, which operates the method of claim 1, comprises a fault detection and isolation module, an aircraft lateral fault-tolerant controller, an actuator switching module, a hydraulic actuator, and an electro-hydraulic actuator. When a rudder surface failure occurs, the aircraft's hydraulic actuators lose pressure. The fault detection and isolation module sends a fault signal to the actuator switching module and the aircraft lateral fault-tolerant controller. The aircraft lateral fault-tolerant controller outputs the required control input. After receiving the fault signal, the actuator switching module switches to the electro-hydraulic actuator and transmits the required control input to the actuator switching module. The actuator switching module provides the required control input.

5. The aircraft lateral fault-tolerant control and reconfiguration system under rudder surface failure as described in claim 4, characterized in that, The aircraft lateral fault-tolerant controller was designed using the following method: (1) Establish a nominal linearized model of the aircraft without rudder control surface failure and a model of the aircraft's lateral motion under rudder control surface failure conditions. (2) Based on the nominal linearized model of the aircraft without rudder control surface failure and the aircraft lateral motion model under rudder control surface failure state, the active fault-tolerant control law of the disturbance observer is designed. The disturbance observer is used to measure the real disturbance, and the estimated disturbance is calculated using the Riccati equation and the regular matrix equation, so that the error between the estimated disturbance and the real disturbance measured by the disturbance observer is within the preset range, and the active fault-tolerant control law of the aircraft under normal conditions is obtained. Then, a quadruple neural network was used to solve for the parameters of the active fault-tolerant control law under the failure degree of the rudder surface in each direction, and finally the complete active fault-tolerant control law was obtained.

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