A method and apparatus for automatic control of vertical speed mode in a fixed-wing aircraft

Abstract

The application provides a fixed-wing aircraft vertical speed mode automatic control method and device, and belongs to the technical field of automatic flight control. The method first determines a flight path angle sliding mode control loop target value based on a vertical speed control loop control law; and then designs a control law of the flight path angle sliding mode control loop based on the flight path angle sliding mode control loop target value. The application can make the aircraft accurately track the vertical speed target value when the aircraft is working in the automatic driving mode and the vertical speed mode is connected, improve the stability of the control process, reduce the overshoot, shorten the development cycle, and reduce the cost.

Description

Technical Field

[0001] This invention belongs to the field of automatic flight control technology, and particularly relates to an automatic control method and device for vertical speed mode of fixed-wing aircraft. Background Technology

[0002] Automatic flight control systems (AFS) are essential for modern transport aircraft, effectively reducing pilot workload and improving flight safety. Currently, due to their simple design and robustness, most transport aircraft AFS utilize traditional PID control architectures for their functional modes, including vertical speed mode. Vertical speed mode is a functional mode of fixed-wing aircraft AFS and is the most important and fundamental operating mode of modern transport aircraft AFS. Control signals for other longitudinal modes can be converted into vertical speed control loops, including altitude hold mode, approach glide mode, and vertical navigation mode.

[0003] The current vertical speed mode uses the traditional PID control method. The inner loop of the vertical speed mode control law uses attitude control, which uses the pitch angle and the pitch rate of the body axis as the feedback signals of the inner loop, while the outer loop uses PI or PID control of the vertical speed deviation and converts the vertical speed deviation into the target pitch angle.

[0004] The disadvantages of the above control methods are: in actual engineering, when designing the control law for the vertical speed mode, it is often necessary to find suitable control law parameters through multiple parameter trials based on certain engineering experience. This undoubtedly increases the development cycle and cost, while the control accuracy and stability are relatively low. Summary of the Invention

[0005] To address the problems of increased development cycle and cost, as well as low control accuracy and stability in existing technologies when designing control laws for vertical speed modes, this invention provides an automatic control method and device for vertical speed mode of fixed-wing aircraft. Using this invention will enable the aircraft to accurately track the target vertical speed value when the autopilot is engaged and vertical speed mode is activated, improving the smoothness of the control process, reducing overshoot, shortening the development cycle, and lowering costs. The technical solution is as follows:

[0006] In a first aspect, a method for automatic control of vertical speed mode of a fixed-wing aircraft is provided, the method comprising:

[0007] Step 1: Determine the target value γ of the sliding mode control loop for the flight path tilt angle based on the vertical velocity control loop control law. d ;

[0008] Step 2: Target value γ of the sliding mode control loop based on flight trajectory tilt angle dDesign the control law for the sliding mode control loop of the flight trajectory tilt angle;

[0009] Furthermore, the method also includes:

[0010] Step 3: The flight control computer performs automatic control of the aircraft's vertical speed mode based on the control law of the flight path tilt sliding mode control loop.

[0011] Optionally, the target value γ of the flight path tilt sliding mode control loop d The calculation formula is:

[0012] γ d =arcsin(u / V0)

[0013]

[0014]

[0015] In the formula, γ d V0 is the target value for the sliding mode control loop, where V is the flight path tilt angle. Choose a value for the vertical velocity. For the aircraft's real-time vertical speed, For vertical velocity deviation, K1, K2, K3, and K4 are the differential signals of the vertical velocity deviation, respectively. K1, K2, K3, and K4 are the proportional coefficient, differential coefficient, integral coefficient, and deviation coefficient.

[0016] Optionally, in step two, when designing the control law of the sliding mode control loop for the flight trajectory tilt angle, the Lyapunov function is designed based on the sliding surface function, and its derivative is calculated; then, based on the derivative of the Lyapunov function, the expression of the exponential reaching law of the vertical velocity mode is determined; and then the expression of the control law of the sliding mode control loop for the flight trajectory tilt angle is derived.

[0017] Alternatively, when designing the sliding mode surface function, the aircraft dynamics state-space equations of the following form can be selected:

[0018]

[0019] In the formula, α, q, γ, δ ec These are the aircraft's angle of attack, pitch rate, flight path angle, and elevator deflection. These are the derivatives of the aircraft's angle of attack, pitch rate, and flight path inclination, respectively. This is the elevator deflection matrix. The state space matrix of the aircraft dynamics;

[0020] Let n be 3 for the sliding surface function, and the sliding surface function be: s = c1x1 + c2x2 + x3, where x1, x2, and x3 represent the aircraft state variables α, q, and γ, respectively; s is the sliding surface function, and c1 and c2 satisfy: c1 = λ 2 ,c2=2λ, λ takes a negative value, x3=γ-γ d .

[0021] Optionally, a positive definite Lyapunov function can be defined as:

[0022]

[0023] Taking the derivative of the Lyapunov function, we get:

[0024] The expression for determining the exponential reaching law is: k takes a number greater than 0;

[0025] The expression for the control law of the sliding mode control loop for the flight trajectory inclination angle is derived as follows:

[0026]

[0027] In the formula,

[0028]

[0029] Optionally, step three includes:

[0030] Step 31: The flight control computer calculates the actuator displacement based on the control law of the sliding mode control loop of the flight trajectory tilt angle;

[0031] Step 32: The flight control system calculates and sends the actuator displacement to the actuator control system;

[0032] Step 33: The actuator control system determines the rudder surface deflection angle based on the actuator displacement;

[0033] Step 34: The automatic throttle control system acquires the target speed, as well as the aircraft's flight speed and acceleration, and calculates the throttle lever angle;

[0034] Step 35: The automatic throttle control system sends the throttle lever angle to the engine control system, so that the engine control system controls the engine thrust according to the throttle lever angle.

[0035] Optionally, the values ​​of k and λ can be determined based on the overshoot and oscillation of the aircraft's actual vertical speed.

[0036] Optionally, the values ​​of K1, K2, K3, and K4 are determined based on the aircraft's flight status.

[0037] In a second aspect, a fixed-wing aircraft vertical speed mode automatic control device is provided, for executing any of the fixed-wing aircraft vertical speed mode automatic control methods described in the first aspect, the device comprising:

[0038] The determination module is used to determine the target value γ of the sliding mode control loop for the flight trajectory tilt angle based on the control law of the vertical velocity control loop. d ;

[0039] The design module is used to design the target value γ of the sliding mode control loop based on the flight path tilt angle. d Design the control law for the sliding mode control loop of the flight trajectory tilt angle.

[0040] Thirdly, an automatic control device for vertical speed mode of a fixed-wing aircraft is provided, including a processor and a memory, wherein the processor is configured to execute instructions stored in the memory, and the processor implements the automatic control method for vertical speed mode of a fixed-wing aircraft as described in any of the first aspects by executing the instructions.

[0041] Fourthly, a computer-readable storage medium is provided, wherein instructions are stored therein, which, when executed on a processing component of a computer, cause the processing component to perform an automatic control method for vertical speed mode of a fixed-wing aircraft as described in any of the first aspects.

[0042] Fifthly, a computer program product containing instructions is provided, which, when run on a computer, causes the computer to execute the automatic control method for vertical speed mode of a fixed-wing aircraft as described in any of the first aspects.

[0043] The beneficial effects of this invention are at least as follows:

[0044] The method provided by this invention can more accurately control the aircraft to follow the vertical speed target value selected by the pilot when the aircraft is in vertical speed mode, reducing vertical speed overshoot, making the aircraft flight control smoother, improving passenger comfort, and is easy to implement. This invention can be used as an inner loop for autopilot altitude hold, altitude acquisition, vertical navigation, and approach glide mode. This invention can be used for the control law design of vertical speed mode for fixed-wing manned aircraft or fixed-wing unmanned aerial vehicles. Attached Figure Description

[0045] Figure 1 This is a block diagram of the vertical speed mode control method provided by the present invention;

[0046] Figure 2 This is the vertical speed control loop model provided by the present invention;

[0047] Figure 3 This invention provides a sliding mode control loop model for flight trajectory tilt angle.

[0048] Figure 4 This is the target vertical velocity value H_g curve given by the present invention;

[0049] Figure 5 This is the simulation curve of aircraft vertical speed control provided by the present invention. Detailed Implementation

[0050] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0051] This invention provides an automatic control method for the vertical velocity mode of a fixed-wing aircraft, mainly including determining the target value γ of the sliding mode control loop for the flight trajectory tilt angle. d And the design of the control law for the sliding mode control loop of the flight trajectory tilt angle. Please refer to... Figure 1 The method includes the following steps:

[0052] Step 1: Determine the target value γ of the sliding mode control loop for the flight path tilt angle based on the vertical velocity control loop control law. d .

[0053] Flight trajectory tilt angle sliding mode control loop target value γ d The calculation formula is:

[0054] γ d =arcsin(u / V0)

[0055]

[0056]

[0057] In the formula, γ d V0 is the target value for the sliding mode control loop, where V is the flight path tilt angle. Choose a value for the vertical velocity. For the aircraft's real-time vertical speed, For vertical velocity deviation, K1, K2, K3, and K4 represent the differential signal of the vertical velocity deviation, respectively. K1, K2, K3, and K4 are the proportional coefficient, differential coefficient, integral coefficient, and deviation coefficient. In practical applications, K1, K2, K3, and K4 should be determined based on the aircraft's flight conditions.

[0058] Furthermore, to improve control accuracy, the vertical velocity deviation... Filtering should be performed.

[0059] Step 2: Target value γ of the sliding mode control loop based on flight trajectory tilt angle d Design the control law for the sliding mode control loop of the flight trajectory tilt angle.

[0060] Specifically, the control law for the sliding mode control loop of the flight trajectory tilt angle is designed according to the following steps:

[0061] 1) Design sliding surface function

[0062] Choose the following form for the aircraft dynamics state-space equations:

[0063]

[0064] In the formula, α, q, γ, δ ec These are the aircraft's angle of attack, pitch rate, flight path angle, and elevator deflection. These are the derivatives of the aircraft's angle of attack, pitch rate, and flight path inclination, respectively. It is the elevator deflection matrix. It is the state space matrix of aircraft dynamics.

[0065] The order of the state-space equations for aircraft dynamics is 3. Therefore, we take n = 3 for the sliding surface function, and thus the sliding surface function is:

[0066] s = c1x1 + c2x2 + x3

[0067] In the formula, x1, x2, and x3 represent the aircraft state variables α, q, and γ, respectively. s is the sliding surface function, and c1 and c2 must satisfy: c1 = λ 2 c² = 2λ, where λ is negative. In specific design, the value of λ should be selected based on the overshoot and oscillation of the aircraft's actual vertical velocity.

[0068] To ensure that the aircraft's flight path angle always tracks the target command, let x3 = γ - γ d In the formula, γ d The target value for the sliding mode control loop is the tilt angle of the flight path.

[0069] 2) Design Lyapunov functions based on sliding surface functions and find their derivatives.

[0070] Define a positive definite Lyapunov function as:

[0071]

[0072] Taking the derivative of the Lyapunov function, we get:

[0073]

[0074] 3) Based on the derivative of the Lyapunov function, determine the expression for the exponential reaching law of the vertical velocity mode.

[0075] By forcing the time derivative of the Lyapunov function to be negative, i.e. The expression for determining the exponential reaching law is: In the formula, k takes a value greater than 0. In specific design, the value of k should be selected according to the overshoot and oscillation of the aircraft's actual vertical speed.

[0076] 4) The expression for the control law of the sliding mode control loop for the flight trajectory inclination angle is derived as follows:

[0077]

[0078] In the formula,

[0079] A1 = -c1a 11 --c2a 12 ,

[0080] A2=-c1a 12 --c2a 22 ,

[0081] B = c1b1 - c2b2

[0082]

[0083] Step 3: The flight control computer performs automatic control of the aircraft's vertical speed mode based on the control law of the flight path tilt sliding mode control loop.

[0084] Step three specifically includes:

[0085] Step 31: The flight control computer calculates the actuator displacement δ based on the control law of the sliding mode control loop of the flight trajectory tilt angle. ec ;

[0086] Step 32: Flight control calculates the actuator displacement δ ec Send to the actuator control system;

[0087] Step 33: The actuator control system is based on the actuator displacement δ ec Determine the control surface deflection angle δ e Determine the rudder surface deflection angle δ e The process can refer to relevant technologies;

[0088] Step 34: The automatic throttle control system acquires the target speed Vg, as well as the aircraft's flight speed and acceleration, and calculates the throttle lever angle.

[0089] Step 35: The automatic throttle control system sends the throttle lever angle to the engine control system, so that the engine control system controls the engine thrust according to the throttle lever angle.

[0090] For example, an embodiment of the present invention provides an automatic control method for the vertical speed mode of a fixed-wing aircraft, the steps of which are as follows:

[0091] 1) Determine the target value γ of the sliding mode control loop for the flight track inclination angle using the above step one. d .

[0092] 2) Using the control law design method of the flight track tilt sliding mode control loop in step two above, the control law of the flight track tilt sliding mode control loop is designed, and the expression of the control law of the flight track tilt sliding mode control loop is derived.

[0093] 3) According to Figure 1 The diagram within the dashed box illustrates the control law architecture for the vertical speed mode. The controller software for the vertical speed mode is developed by loading the calculation formulas and control law expressions from steps one and two into the flight control computer. Figure 1 The vertical speed control loop has three input signals, namely: An output signal γ d , Figure 1 The sliding mode control loop for the flight path tilt angle has four input signals: α, q, γ, γ d An output signal δ ec .

[0094] This embodiment uses the following steps to verify the vertical velocity control method:

[0095] Step 1) as Figure 1 As shown, a simulation model was built using Matlab / Simulink. The model consists of an aircraft longitudinal dynamics model, an actuator model, an autothrottle control system model, a flight path tilt angle sliding mode control loop model, and a vertical velocity control loop model. Figure 1 middle Indicates the given vertical velocity of the target. This represents the real-time aircraft vertical velocity feedback signal. The differential signal represents the vertical velocity, γ represents the flight path inclination angle, α represents the angle of attack, q represents the pitch rate, and V represents the vertical velocity. g V represents the given target airspeed. The differential signal representing airspeed, δ e Indicates the elevator deflection angle, δ t V represents the throttle lever angle, and V represents the airspeed. The flight path tilt angle signal, angle of attack signal, pitch rate signal, airspeed signal, and vertical velocity signal are extracted from the aircraft longitudinal dynamics model and sent to the control law model.

[0096] Step 2) Build using mathematical simulation software Matlab / Simulink Figure 1 The vertical velocity control loop model within the vertical velocity mode control law architecture shown is described in [reference needed]. Figure 2 The values ​​of the control law parameters selected in this embodiment are shown in Table 1.

[0097] Table 1. Control Law Parameters for Vertical Velocity Control Loop

[0098] K2 1 K3 0.1 K4 1

[0099] Step 3) Build using mathematical simulation software Matlab / Simulink Figure 1 The model of the flight trajectory tilt angle sliding mode control loop within the framework of the vertical velocity mode control law is shown below. Figure 3 In this embodiment, c1 = 4 and c2 = 2 are selected in the sliding mode function, and k = 3 is selected in the exponential reaching law.

[0100] Step 4) Set the entire model running cycle to 0.02 seconds and the simulation time to 80 seconds;

[0101] Step 5) The aircraft's initial flight altitude is 4000 meters and its airspeed is 130 meters per second;

[0102] Step 6) Given the target vertical velocity value H_g curve, as shown in the figure. Figure 4 As shown, the unit is meters per second;

[0103] Figure 4 In the test, the target vertical velocity value is +10 m / s for 0-20 seconds, 0 m / s for 20-40 seconds, -10 m / s for 40-60 seconds, and 0 m / s for 60-80 seconds.

[0104] from Figure 5 As can be seen, the aircraft can follow the given vertical speed target value very well, with small overshoot, no oscillation, and good control effect. This verifies the effectiveness of the method of the present invention.

[0105] The vertical speed mode automatic control method provided in this embodiment of the invention can be used as an inner loop for autonomous driving altitude holding, altitude interception, vertical navigation, and approach glide mode.

[0106] The vertical speed mode control method provided in this invention can be used for the design of control laws for the vertical speed mode of fixed-wing manned aircraft or fixed-wing unmanned aerial vehicles.

[0107] The method provided by this invention has the advantages of fast response, insensitivity to parameter changes and disturbances, and excellent robustness to systems with uncertain parameters.

[0108] An embodiment of the present invention also provides an automatic control device for the vertical speed mode of a fixed-wing aircraft, used to execute an automatic control method for the vertical speed mode of a fixed-wing aircraft provided in an embodiment of the present invention, the device comprising:

[0109] The determination module is used to determine the target value γ of the sliding mode control loop for the flight trajectory tilt angle based on the control law of the vertical velocity control loop. d ;

[0110] The design module is used to design the target value γ of the sliding mode control loop based on the flight path tilt angle. d Design the control law for the sliding mode control loop of the flight trajectory tilt angle.

[0111] The specific execution process of each module in this invention can be referred to the specific process of the relevant steps of the above method, and will not be repeated here.

[0112] An embodiment of the present invention also provides an automatic control device for the vertical speed mode of a fixed-wing aircraft, including a processor and a memory. The processor is configured to execute instructions stored in the memory, and the processor implements the automatic control method for the vertical speed mode of a fixed-wing aircraft according to the present invention by executing the instructions.

[0113] Another embodiment of the present invention provides a computer-readable storage medium storing instructions that, when executed on a computer processing component, cause the processing component to perform the automatic control method for vertical speed mode of a fixed-wing aircraft as described in the present invention.

[0114] In another embodiment of the present invention, a computer program product containing instructions is provided, which, when run on a computer, causes the computer to execute the automatic control method for vertical speed mode of a fixed-wing aircraft as described in the present invention.

[0115] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. An automatic control method for vertical speed mode of a fixed-wing aircraft, characterized in that, The method includes: Step 1: Determine the target value γ of the sliding mode control loop for the flight path tilt angle based on the vertical velocity control loop control law. d ; Target value γ of the sliding mode control loop for flight path tilt angle d The calculation formula is: γ d =arcsin(u / V0), ， In the formula, γd is the target value of the sliding mode control loop for the flight path inclination angle, and V0 is the aircraft speed. Choose a value for the vertical velocity. For the aircraft's real-time vertical speed, For vertical velocity deviation, K1, K2, K3, and K4 are the differential signals of the vertical velocity deviation, respectively. Step 2: Target value γ of the sliding mode control loop based on flight trajectory tilt angle d The control law for the flight path tilt sliding mode control loop is designed by first designing the Lyapunov function based on the sliding surface function and then differentiating it. Based on the derivative of the Lyapunov function, the expression for the exponential reaching law of the vertical velocity mode is determined. Finally, the expression for the control law of the flight path tilt sliding mode control loop is derived. In step two, when designing the sliding surface function, the aircraft dynamics state-space equations of the following form are selected: ， In the formula, α, q, γ, and δec represent the aircraft's angle of attack, pitch rate, flight path angle, and elevator deflection, respectively. These are the derivatives of the aircraft's angle of attack, pitch rate, and flight path inclination, respectively. This is the elevator deflection matrix. The state space matrix of the aircraft dynamics; Let n be 3 for the sliding surface function, and the sliding surface function be: s = c1x1 + c2x2 + x3, where x1, x2, and x3 represent the aircraft state variables α, q, and γ, respectively; s is the sliding surface function, and c1 and c2 satisfy: c1 = λ 2 ,c2=2λ, λ takes a negative value, x3=γ-γ d ; In step two, the positive definite Lyapunov function is defined as follows: ， Taking the derivative of the Lyapunov function, we get: , The expression for determining the exponential reaching law is: k takes a number greater than 0; The expression for the control law of the sliding mode control loop for the flight trajectory inclination angle is derived as follows: ， In the formula, 。 2. The method according to claim 1, characterized in that, The method further includes: Step 3: The flight control computer performs automatic control of the aircraft's vertical speed mode based on the control law of the flight path tilt sliding mode control loop.

3. The method according to claim 2, characterized in that, Step three includes: Step 31: The flight control computer calculates the actuator displacement based on the control law of the sliding mode control loop of the flight trajectory tilt angle; Step 32: The flight control system calculates and sends the actuator displacement to the actuator control system; Step 33: The actuator control system determines the rudder surface deflection angle based on the actuator displacement; Step 34: The automatic throttle control system acquires the target speed, as well as the aircraft's flight speed and acceleration, and calculates the throttle lever angle; Step 35: The automatic throttle control system sends the throttle lever angle to the engine control system, so that the engine control system controls the engine thrust according to the throttle lever angle.

4. The method according to claim 1, characterized in that, The values ​​of k and λ are determined based on the overshoot and oscillation of the aircraft's actual vertical speed.

5. The method according to claim 2, characterized in that, The values ​​of K1, K2, K3, and K4 are determined based on the aircraft's flight status.

6. An automatic control device for vertical speed mode of a fixed-wing aircraft, characterized in that, The apparatus for performing an automatic control method for vertical speed mode of a fixed-wing aircraft as described in any one of claims 1 to 5, the apparatus comprising: The determination module is used to determine the target value γ of the sliding mode control loop for the flight trajectory tilt angle based on the control law of the vertical velocity control loop. d ; The design module is used to design the target value γ of the sliding mode control loop based on the flight path tilt angle. d Design the control law for the sliding mode control loop of the flight trajectory tilt angle.

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