Aircraft attitude preset performance control method and device based on disturbance observer

Abstract

The invention discloses an aircraft attitude preset performance control method and device based on a disturbance observer, and the method comprises the steps: 1, building an attitude control model of an aircraft based on the kinematics and dynamics models of the aircraft; 2, designing a disturbance observer to estimate uncertain items and external disturbance in the aircraft attitude control model; and step 3, based on a preset performance control theory, designing a preset performance sliding mode attitude controller. According to the technical scheme provided by the embodiment of the invention, the anti-interference performance of the controller is improved, and the tracking of the expected control signal of the three-axis attitude angle of the aircraft within the preset performance boundary can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aircraft control, and particularly relates to a method and device for preset performance control of aircraft attitude based on a disturbance observer. BACKGROUND

[0002] As a complex nonlinear system with multiple inputs and multiple outputs, when the system model is not accurately modeled, the system is subjected to severe external disturbance or the internal modeling parameter is subjected to perturbation, the control law designed by common methods (such as backstepping method, dynamic inverse control, etc.) is difficult to meet the expected index due to lack of strong robustness and anti-interference ability.

[0003] In order to further improve the regulation of dynamic performance (such as overshoot, regulation time, etc.) in the control process, the birth of the preset performance control method provides an effective solution to this problem. SUMMARY

[0004] The application provides a method and device for preset performance control of aircraft attitude based on a disturbance observer, which is based on a disturbance observer and combined with preset performance control theory, and is mainly applied to attitude tracking control of a fixed-wing aircraft after the aircraft is subjected to simple disturbance, and is unique and different from the above-mentioned related patent inventions.

[0005] The application provides a method for preset performance control of aircraft attitude based on a disturbance observer, which comprises the following steps: Step 1: based on the kinematics and dynamics equations of an aircraft, a second-order model related to aircraft attitude control is established; Step 2: a nonlinear disturbance observer is established, which is used for estimating the uncertain terms in the aircraft attitude control model and external disturbance; Step 3: according to the second-order model of aircraft attitude control, the nonlinear disturbance observer and the error conversion function, a preset performance attitude controller is established, so that the system error is kept within the preset performance boundary.

[0006] Optionally, the expression of the second-order model of aircraft attitude control is as follows: ; In the formula, denotes the roll angle, pitch angle and yaw angle of the aircraft, denotes the corresponding three-axis angular velocity, denotes the three-axis control moment, denotes the external disturbance in three directions of the aircraft in the attitude control process. , , The expression of is as follows: ; ; ; In the formula , , This refers to the torques on the roll, pitch, and yaw axes other than the control torques generated by the three primary control surfaces. , and These represent the aircraft orbiting the fuselage. Moment of inertia of the three axes for The product of inertia between axes.

[0007] Optionally, the disturbance observer expression for the aircraft attitude control is:

[0008] In the formula, This is the exponential convergence law; This represents the observed value from the disturbance observer.

[0009] Optionally, the preset performance attitude controller is: ; In the formula , , It is a positive number. , It is a positive odd number and , This refers to the three-axis attitude angle tracking error. The conversion error is , It is a non-singular fast terminal sliding surface. For symbolic functions, x 1d The desired attitude angle signal; Auxiliary quantity , ,in, , , ( i =1, 2, 3); This represents the preset performance function in preset performance control; ; In the formula , ; To normalize the systematic error, ; wherein is a three-axis attitude angle tracking error; is a smooth, monotonically increasing and error conversion function, the function is specifically as follows ; wherein is a constant, satisfying , represents an initial value of the three-axis attitude angle tracking error .

[0010] The second aspect of the present application provides an aircraft attitude preset performance control device based on a disturbance observer, comprising: a first model establishing module, configured to establish a second-order model related to aircraft attitude control based on kinematics and dynamics equations of the aircraft; a second model establishing module, configured to establish a nonlinear disturbance observer, the nonlinear disturbance observer being configured to estimate uncertain terms in the aircraft attitude control model and external disturbances; a controller establishing module, configured to establish a preset performance attitude controller according to the second-order model of the aircraft attitude control, the nonlinear disturbance observer and the error conversion function, so that the system error is kept within a preset performance boundary.

[0011] Optionally, the second-order model of the aircraft attitude control is expressed as: ; wherein, represents a roll angle, a pitch angle and a yaw angle of the aircraft, represents corresponding three-axis angular velocities, represents three-axis control moments, represents external disturbances in three directions of the aircraft during the attitude control process. , , The expression of is as follows: ; ; ; wherein , , represents other moments in addition to control moments generated by three primary control surfaces in the roll, pitch and yaw axes, , and respectively represent moments of inertia of the aircraft around the body three axes, For The inertia product between the axes.

[0012] Optionally, the expression of the disturbance observer of the aircraft attitude control is:

[0013] In the formula, is an exponential approach law; represents the observation value of the disturbance observer.

[0014] Optionally, the preset performance attitude controller is: ; In the formula , , is a positive number, , is a positive odd number and , is a three-axis attitude angle tracking error, the conversion error of , is a non-singular fast terminal sliding surface, is a sign function, x 1d is a desired attitude angle signal; auxiliary quantity , wherein, , , i =1, 2, 3); represents a preset performance function in the preset performance control; ; In the formula , ; is normalized to the system error, ; In the formula is a three-axis attitude angle tracking error; is a smooth, monotonically increasing and related error conversion function, and the function is specifically as follows ; wherein is a constant, satisfying , represents a three-axis attitude angle tracking error The initial value.

[0015] This invention proposes a method and apparatus for pre-defined performance control of aircraft attitude based on a disturbance observer. The pre-defined performance aircraft attitude controller constructed by this invention can track the desired control signal of the three-axis attitude angle within the pre-defined performance boundary, can quickly estimate disturbances, and compensate the controller, thereby improving control efficiency. Attached Figure Description

[0016] Figure 1 A flowchart of an aircraft attitude preset performance control method based on a disturbance observer provided in an embodiment of the present invention; Figure 2 This is the tracking result of the desired attitude angle signal under sinusoidal perturbation conditions in an embodiment of the present invention; Figure 3 This refers to the tracking error of the desired attitude angle signal under sinusoidal perturbation conditions in this embodiment of the invention. Figure 4 This is the attitude angle observation output under sinusoidal disturbance conditions in this embodiment of the invention; Figure 5 This refers to the attitude angle observation error under sinusoidal disturbance conditions in the embodiments of the present invention. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] like Figure 1 As shown, this embodiment of the invention provides an aircraft attitude preset performance control method based on a disturbance observer, which combines preset performance theory with a disturbance observer. First, the aircraft attitude control method provided in this embodiment of the invention establishes an aircraft attitude control model based on the aircraft's motion model; Then, a disturbance observer is designed; Finally, based on the preset performance theory and the designed disturbance observer, a preset performance attitude controller was designed to achieve control of the aircraft's attitude.

[0019] Exemplarily, based on the preset performance control theory, firstly, the state (error) of the controlled system is artificially set with performance constraints; secondly, an isomorphism function is introduced to homomorphically map the constraint space to an unconstrained space; finally, in the new space generated by the mapping, a preset performance attitude controller capable of guaranteeing the stability of the new system is designed, so that the system error is kept within the preset performance boundary.

[0020] The aircraft attitude control method based on the preset performance controller provided by the embodiment of the application can include the following steps. Step 1, establishing an aircraft attitude control model based on the motion model of the aircraft; In order to facilitate the design of the control law, the aircraft attitude control model is constructed based on the kinematics and dynamics equations of the aircraft, as shown below:

[0021] In the formula, denotes the roll angle, the pitch angle and the yaw angle of the aircraft, denotes the corresponding three-axis angular velocity, denotes the three-axis control moment, denotes the external disturbance in three directions suffered by the aircraft during the attitude control process. , , The expression of is as follows: ; ; ; In the formula , , denotes the other moments on the roll, pitch and yaw axes in addition to the control moments generated by the three primary control surfaces, , and denote the moments of inertia of the aircraft around the body three axes, is the inertia product between the axes.

[0022] Step 2, designing a disturbance observer. Before designing the attitude controller, the external disturbance in the aircraft attitude control model is estimated using an observer to reduce or eliminate the influence of the unknown term on the effect of the controller. The disturbance observer can derive the state variable estimation value according to the input variable and output variable values of the system to achieve the estimation of the disturbance. The expression of the disturbance observer is as follows:

[0023] In the formula, is an exponential approach law, and its value is calculated by the following formula:

[0024] In the formula, .

[0025] Step 3, based on the preset performance theory, a preset performance sliding mode attitude controller is designed based on the disturbance observer designed in step 2, so as to realize the control of the attitude of the aircraft; Firstly, the three-axis attitude angle tracking error is defined as , and the expression is:

[0026] In the formula, represents the expected attitude angle, respectively, are the attitude angle tracking errors in the roll, pitch and yaw directions.

[0027] In an example embodiment of the application, the state (error) of the controlled system is artificially set to have performance constraints, and when the system tracking error is within the performance envelope boundary, the dynamic and steady-state characteristics of the system can meet the preset index, that is

[0028] In the formula, and are the preset lower envelope and upper envelope, respectively, wherein is a constant, satisfying By adjusting , the constraint on the system overshoot can be realized.

[0029] The selected performance envelope function satisfies: It is always greater than zero and monotonically decreasing within the defined time; as the time increases, tends to a constant , that is .

[0030] In order to realize the preset performance control of the aircraft attitude, the preset performance function is selected as:

[0031] In the formula, , .

[0032] In an example embodiment of the application, the introduction of the homeomorphism function maps the constraint space to the unconstrained space as: Firstly, the system error is normalized:

[0033] A smooth and monotonically increasing error conversion function is selected The normalized error is converted to the error in the real number field :

[0034] At this time, when the conversion error is bounded, the system performance constraint condition will be met, and the error conversion function is selected as: .

[0035] According to the preset performance control theory, the conversion error of is defined as . According to the conversion error, the attitude controller is designed, and when the system satisfies the asymptotic stability condition, the system error can be kept within the preset performance boundary.

[0036] When designing the preset performance attitude controller, the derivative of the conversion error is needed, and the expression is:

[0037] In order to facilitate derivation, the auxiliary quantity , is defined, where: , , i =1, 2, 3; Definition:

[0038] Taking the derivative of the above formula, we get:

[0039]

[0040]

[0041] The nonsingular fast terminal sliding mode surface is defined as follows:

[0042] In the formula , is a positive odd number and

[0043] The approach law is selected, and the expression is as follows:

[0044] The expression of the preset performance attitude controller is as follows:

[0045] In the formula, , , is a positive number, , is a positive odd number and , is a three-axis attitude angle tracking error, the conversion error of , the auxiliary quantity , ,, is a non-singular fast terminal sliding mode surface.

[0046] The embodiment of the application provides an aircraft attitude preset performance control method based on a disturbance observer, which combines the disturbance observer with the preset performance control. Firstly, the aircraft attitude control method provided by the embodiment of the application establishes an aircraft attitude control model based on the kinematics and dynamics model of the aircraft. Then, the disturbance observer is constructed. Finally, the embodiment of the application proposes an aircraft attitude preset performance control scheme based on a disturbance observer. The aircraft attitude control method provided by the embodiment of the application can realize the tracking of the three-axis attitude angle expected control signal within the preset performance boundary, can estimate the disturbance more quickly and compensate the controller, and improves the control efficiency. Compared with the traditional control method, the control scheme proposed by the embodiment of the application has smaller overshoot when tracking the signal changing quickly, and the system error will not exceed the performance boundary.

[0047] Further, in order to illustrate the effectiveness of the aircraft attitude control method proposed by the embodiment of the application, the simulation experiment of the attitude control method provided by the embodiment of the application is carried out. The tracking results of the expected tracking signal of the controller under simple disturbance are verified.

[0048] In the simulation, the initial conditions of 1000m in height and 100m / s in speed are selected, and the expected attitude angle command is given. Figures 2-5 The result curve and the tracking error curve of the preset performance controller provided by the embodiment of the application for tracking the expected attitude angle signal are given when the experiment is carried out in the sinusoidal external disturbance field, as shown in Figure 2 and Figure 3As can be seen from Figs. 6 and 7, under the influence of the sinusoidal form disturbance signal, the system can track the desired pitch angle signal within 2s whether the disturbance observer is added or not, but after 2s, the controller without the disturbance observer still has a small tracking error, and the tracking error will oscillate about 0.2° due to the existence of the disturbance, but can still be kept within the preset performance boundary. Figure 4 and Figure 5 As can be seen from Figs. 6 and 7, under the influence of the sinusoidal form disturbance signal, the system can track the desired pitch angle signal within 2s whether the disturbance observer is added or not, but after 2s, the controller without the disturbance observer still has a small tracking error, and the tracking error will oscillate about 0.2° due to the existence of the disturbance, but can still be kept within the preset performance boundary.

[0049] As can be seen from the simulation results, the control scheme proposed in the present application can realize tracking of the desired control signal of the three-axis attitude angle of the aircraft within the preset performance boundary, and improve the control efficiency.

[0050] Although the embodiments of the present application are as above, the content is only the embodiments adopted for the purpose of facilitating understanding of the present application, and is not intended to limit the present application. Any person skilled in the art of the present application can make any modification and change in the implementation form and details without departing from the spirit and scope of the present application, but the patent protection scope of the present application shall be subject to the scope defined by the appended claims.

Claims

1. A method for pre-setting aircraft attitude performance control based on a disturbance observer, characterized in that, Includes the following steps: Step 1: Based on the aircraft's kinematics and dynamics equations, establish a second-order model related to aircraft attitude control; Step 2: Establish a nonlinear disturbance observer. The nonlinear disturbance observer is used to estimate the uncertainties in the aircraft attitude control model and external disturbances. Step 3: Based on the second-order model of aircraft attitude control, the nonlinear disturbance observer, and the error transformation function, establish a preset performance attitude controller to keep the system error within the preset performance boundary.

2. The aircraft attitude preset performance control method based on a disturbance observer according to claim 1, characterized in that, The second-order model expression for the aircraft attitude control is: ; In the formula, Indicates the aircraft's roll angle, pitch angle, and yaw angle. This indicates the corresponding triaxial angular velocity. Indicates the three-axis control torque. This refers to the external disturbances experienced by the aircraft in three directions during attitude control. , , The expression is as follows: ; ; ; In the formula , , This refers to the torques on the roll, pitch, and yaw axes other than the control torques generated by the three primary control surfaces. , and These represent the aircraft orbiting the fuselage. Moment of inertia of the three axes for The product of inertia between axes.

3. The aircraft attitude preset performance control method based on a disturbance observer according to claim 2, characterized in that, The disturbance observer expression for the aircraft attitude control is: In the formula, s1 is the exponential reaching law; This represents the observation value of the disturbance observer.

4. The aircraft attitude preset performance control method based on a disturbance observer according to claim 3, characterized in that, The preset performance attitude controller is: In the formula, c1,λ,μ>0, α2,β2 are positive numbers, p2,q2 are positive odd numbers and 1 <p2 / q2<2,e s e represents the three-axis attitude angle tracking error. s The conversion error is ε s S is a non-singular fast terminal sliding surface, sign(S) is the sign function, and x 1d The desired attitude angle signal; Auxiliary quantities r = diag(r1, r2, r3), v = diag(v1, v2, v3), where, ρ i (t) represents the preset performance function in preset performance control; where ρ i0 > ρ i∞ > 0, β i > 0; To normalize the systematic error, In the formula e i (t) represents the three-axis attitude angle tracking error; T i (·) represents a smooth, monotonically increasing sum. The relevant error transformation function is as follows: Where δ i It is a constant that satisfies δ i ∈(0,1], e0 represents the three-axis attitude angle tracking error e i The initial value of (t).

5. An aircraft attitude preset performance control device based on a disturbance observer, characterized in that, include: The first model building module is used to build a second-order model related to aircraft attitude control based on the aircraft kinematics and dynamics equations. The second model building module is used to build a nonlinear disturbance observer, which is used to estimate the uncertainties and external disturbances in the aircraft attitude control model. The controller establishment module is used to establish a preset performance attitude controller based on the second-order model of aircraft attitude control, the nonlinear disturbance observer, and the error transformation function, so that the system error is kept within the preset performance boundary.

6. The aircraft attitude preset performance control device based on a disturbance observer according to claim 5, characterized in that, The second-order model expression for the aircraft attitude control is: ; In the formula, Indicates the aircraft's roll angle, pitch angle, and yaw angle. This indicates the corresponding triaxial angular velocity. Indicates the three-axis control torque. This refers to the external disturbances experienced by the aircraft in three directions during attitude control. , , The expression is as follows: ; ; ; In the formula , , This refers to the torques on the roll, pitch, and yaw axes other than the control torques generated by the three primary control surfaces. , and These represent the aircraft orbiting the fuselage. Moment of inertia of the three axes for The product of inertia between axes.

7. The aircraft attitude preset performance control device based on a disturbance observer according to claim 6, characterized in that, The disturbance observer expression for the aircraft attitude control is: In the formula, s1 is the exponential reaching law; This represents the observation value of the disturbance observer.

8. The aircraft attitude preset performance control device based on a disturbance observer according to claim 7, characterized in that, The preset performance attitude controller is: ； In the formula , , It is a positive number. , It is a positive odd number and , This refers to the three-axis attitude angle tracking error. The conversion error is , It is a non-singular fast terminal sliding surface. For symbolic functions, x 1d The desired attitude angle signal; Auxiliary quantity , ,in, ， ，（ i =1，2，3）； This represents the preset performance function in preset performance control; ； In the formula , ; To normalize the systematic error, ； In the formula This refers to the three-axis attitude angle tracking error. For a smooth, monotonically increasing sum The relevant error transformation function is as follows: ； in It is a constant, satisfying , Indicates the three-axis attitude angle tracking error The initial value.

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