A method and device for controlling longitudinal and velocity channels of a fixed-wing aircraft

Abstract

The present invention provides a method and device for controlling the longitudinal and velocity channels of a fixed-wing aircraft, comprising the following steps: designing a low-pass filter to filter the velocity of the aircraft, designing a fast differential observer, using the filtered velocity as input, and using the acceleration tracking result output by the fast differential observer as the derivative of the aircraft velocity; obtaining the control parameter velocity used by the aircraft in the control according to the indicated airspeed and flight altitude of the aircraft; obtaining the control method for the longitudinal and velocity channels according to the obtained aircraft velocity derivative and the control parameter velocity of the aircraft. The present invention can effectively solve the problem of serious coupling between the longitudinal and velocity channels of such aircraft, improve the control adaptability of the drone under narrow flight boundaries and strong external environmental interference, effectively improve the loop response characteristics, and effectively improve the safety of flight control.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft control, and in particular relates to a method and device for controlling the longitudinal and velocity channels of a fixed-wing aircraft. Background Art

[0002] For low-dynamic fixed-wing aircraft with large aspect ratio, the aircraft generally has large lift and drag, and the flight envelope is in the low-speed zone and is relatively narrow. When the UAV flies in a low dynamic pressure state, the coupling effect between the aircraft speed and the longitudinal track loop will be more significant than that of a high-speed aircraft. At this time, the fluctuation of the longitudinal loop will cause a drastic change in speed, which may cause the aircraft's flight speed to be lower than the lower limit of the safe flight speed, affecting flight safety; at the same time, the aircraft is very susceptible to the influence of the environmental wind field, causing airspeed fluctuations. At this time, the speed fluctuation will also cause the oscillation of the longitudinal attitude loop, which will not only cause a large deviation in the longitudinal track tracking, but also the instability of the aircraft attitude loop will affect the flight safety of the aircraft.

[0003] In the design process of conventional aircraft control strategies, the elevator is generally used for longitudinal track control, and the throttle is used for speed loop control. However, due to the lack of appropriate coordinated control between the control surface and the throttle, the decoupling control effect is not ideal. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method and device for controlling the longitudinal and velocity channels of a fixed-wing aircraft. The solution of the present invention can solve the problems existing in the prior art.

[0005] The technical solution of the present invention:

[0006] A method for controlling longitudinal and velocity channels of a fixed-wing aircraft comprises the following steps:

[0007] Design a low-pass filter to filter the speed of the aircraft.

[0008] Design a fast differential observer, take the filtered velocity as input, and use the acceleration tracking result output by the fast differential observer as the derivative of the aircraft velocity;

[0009] According to the indicated airspeed and flight altitude of the aircraft, obtain the control parameter speed V used by the aircraft in control;

[0010] According to the obtained aircraft velocity derivative and the aircraft control speed, the control method of the longitudinal and velocity channels is obtained: Among them, T c is the throttle control amount, δ e is the throttle control parameter, K np ,K pt ,K it ,Kpe ,K ie ,K q is the control parameter, q is the pitch angle rate, and They represent the total energy change rate increment and energy conversion change rate increment respectively. in, V c is the desired speed command, is the desired speed change rate command, is the expected height change law instruction, K vE ,K vL is the control parameter, Among them, K V ,K h is the controller parameter, h c The desired altitude command.

[0011] Furthermore, the structure of the fast differential observer is:

[0012] in

[0013] Where (k) represents the current beat signal, (k-1) represents the sampling value of the previous beat signal, T is the sampling period; v is the velocity signal, is the input signal of the differential observer, z 1 ,z 2 are the output signals of the differential observer, r and h are the filter parameters.

[0014] A device for controlling the longitudinal and speed channels of a fixed-wing aircraft comprises a filter, a fast differential observer, a parameter-controlled speed calculator and a controller. The filter obtains the speed of the aircraft, filters it and sends it to the fast differential observer. The fast differential observer tracks the speed and the differential of the speed according to the aircraft speed obtained by filtering, and inputs the result of tracking the speed differential into the controller as the speed derivative of the aircraft. The parameter-controlled speed calculator calculates the parameter-controlled speed of the aircraft according to the indicated airspeed and flight altitude of the aircraft, and transmits it to the controller. The controller calculates the throttle control amount and the throttle control parameter according to the obtained parameter-controlled speed and the speed derivative of the aircraft according to the control method.

[0015] Furthermore, the filter is a low-pass filter.

[0016] The beneficial effects of the present invention compared with the prior art are as follows:

[0017] The present invention decouples the longitudinal direction and velocity of the aircraft through the total energy method, which can effectively solve the problem of serious coupling between the longitudinal and velocity channels of such aircraft, enhance the control adaptability of the UAV under narrow flight boundaries and strong external environmental interference, effectively improve the loop response characteristics, and effectively improve the safety of flight control. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A schematic diagram of the steps of a method for controlling longitudinal and velocity channels of a fixed-wing aircraft provided in an embodiment of the present invention is shown;

[0020] Figure 2 A schematic diagram of a longitudinal and speed channel control device for a fixed-wing aircraft provided in an embodiment of the present invention is shown;

[0021] Figure 3 A schematic diagram of a longitudinal and speed channel control device for a fixed-wing aircraft according to an embodiment of the present invention is shown;

[0022] Figure 4 A schematic diagram of the control principle of a controller provided according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0025] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0026] like Figure 1 As shown, according to an embodiment of the present invention, a method for controlling the longitudinal and velocity channels of a fixed-wing aircraft is provided, comprising the following steps:

[0027] Step 1: Design a low-pass filter to filter the speed of the aircraft;

[0028] For large aspect ratio low dynamic fixed-wing aircraft, the speed measurement signal has large noise, which has a great impact on the signal quality, and the speed differential signal cannot be directly extracted from the speed signal. In the process of engineering use, the speed signal needs to be filtered.

[0029] In one embodiment, the speed is filtered using a low-pass filter, and the signal obtained by filtering is used as a parameter control signal to solve the control law. Generally, a first-order low-pass filter can be selected, and the filter structure is shown below.

[0030]

[0031] in, is the filter output, is the filter output value of the previous beat, r(k-1) is the sampling value of the previous beat; T is the sampling period, and A is the time constant, which can be selected according to the quality of the speed signal.

[0032] Step 2: Design a fast differential observer, take the filtered velocity as input, and use the output of the fast differential observer as z 2 As the derivative of the aircraft velocity;

[0033] In one embodiment, the fast differential observer structure is:

[0034] in

[0035] Where (k) represents the current beat signal, (k-1) represents the sampling value of the previous beat signal, T is the sampling period; v is the velocity signal, is the input signal of the differential observer, z 1 ,z 2 are the output signals of the differential observer, r and h are the filter parameters.

[0036] Step 3: According to the indicated airspeed and flight altitude of the aircraft, obtain the control speed used by the aircraft in control

[0037] In actual engineering applications, aircraft sensors often obtain indicated airspeed signals. Considering that the control law design is based on the evaluation of energy changes, when the aircraft's flight altitude envelope changes slightly, the indicated airspeed signal can be directly used instead of the true airspeed signal to solve the control law; if the aircraft's flight envelope is large, the correspondence between the indicated airspeed and the true airspeed at different altitudes in the envelope is quite different, and it cannot represent the real energy changes. Here, the indicated airspeed signal is processed to calculate the control parameter speed.

[0038] in, is the processed parameter control speed signal, V ias is the airspeed signal, ρ 0 is the sea level atmospheric density, ρ 0 =1.225kg / m 3 , ρ is the atmospheric density, and its value changes with altitude, satisfying the following equation:

[0039]

[0040] In the control law design process, the It participates in solving the control law as a speed signal.

[0041] Step 4: According to the obtained aircraft velocity derivative and the aircraft control parameter velocity, the control method of the longitudinal and velocity channels is obtained.

[0042] The total energy control method is used to complete the control law design. The throttle adjustment is mainly used to change the total energy of the drone. The deflection of the elevator causes the change of the longitudinal torque of the drone, which does not change the total energy. It only coordinates the mutual conversion between its potential energy and kinetic energy to achieve the purpose of distributing the total energy. In the control law design, the concepts of total energy and energy distribution of the drone are involved. The following defines the variable E T and L T Representing the total amount of energy and energy distribution, the above variables are defined as follows:

[0043] E T =0.5mV 2 +mgh

[0044] L T =0.5mV 2 -mgh

[0045] Among them, m is the mass of the aircraft, V is the true airspeed of the drone, h is the altitude of the drone, and g is the acceleration due to gravity.

[0046] Define variable energy change rate and energy conversion rate The above variables are defined as follows:

[0047]

[0048]

[0049] During the flight, the total energy change is mainly controlled by changing the thrust by adjusting the throttle amount, that is, by adjusting the throttle amount, the total energy reaches the desired state, and the energy change law Converge to 0; by adjusting the elevator to adjust the pitch angle of the drone to change the energy distribution between potential energy and kinetic energy, that is, by adjusting the elevator, the energy distribution ratio reaches the desired state, and the energy conversion change rate converges to 0. The longitudinal and speed control loops are designed as follows: Among them, T c is the throttle control amount, δ e is the throttle control parameter, K np ,K pt ,K it ,K pe ,K ie ,K q is the control parameter, q is the pitch angle rate, and this term is introduced to improve the damping characteristics of the longitudinal loop. and They represent the total energy change rate increment and energy conversion change rate increment respectively.

[0050] in,

[0051] in, V c is the desired speed command, is the desired speed change rate command, is the expected height change law instruction, K vE ,K vL is the control parameter,

[0052] in,

[0053] Among them, K V ,K h is the controller parameter, h c is the desired height command. By changing the control parameter K V ,K h , it can change the speed and altitude outer loop response characteristics, adjust the priority of the response of the UAV's longitudinal and speed channels, and implement priority altitude loop adjustment or priority speed loop adjustment according to flight mission requirements.

[0054] According to another embodiment, a longitudinal and speed channel control device for a fixed-wing aircraft is provided, including a filter, a fast differential observer, a parameter control speed calculator and a controller. The filter obtains the speed of the aircraft and filters it, and then sends it to the fast differential observer. The fast differential observer tracks the speed and the differential of the speed according to the aircraft speed obtained by filtering, and inputs the result of the speed differential tracking into the controller as the speed derivative of the aircraft. The parameter control speed calculator calculates the parameter control speed of the aircraft according to the indicated airspeed and flight altitude of the aircraft, and transmits it to the controller. The controller calculates the throttle control amount and throttle control parameters according to the obtained parameter control speed and the speed derivative of the aircraft according to the control method.

[0055] Further in one embodiment, the filter is a low-pass filter. In this embodiment, the filter structure is as follows.

[0056]

[0057] in, is the filter output, is the filter output value of the previous beat, r(k-1) is the sampling value of the previous beat; T is the sampling period, and A is the time constant, which can be selected according to the quality of the speed signal.

[0058] Further in one embodiment, the method for the parameter control speed calculator to calculate the parameter control speed V is:

[0059]

[0060] in, is the processed parameter control speed signal, Vias is the airspeed signal, ρ 0 is the sea level atmospheric density, ρ 0 =1.225kg / m 3 , ρ is the atmospheric density, and its value changes with altitude, satisfying the following equation:

[0061]

[0062] Further in one embodiment, the fast differential observer structure is:

[0063]

[0064] in

[0065] Where (k) represents the current beat signal, (k-1) represents the sampling value of the previous beat signal, T is the sampling period; v is the velocity signal, is the input signal of the differential observer, z 1 ,z 2 are the output signals of the differential observer, r and h are the filter parameters.

[0066] Further in one embodiment, the longitudinal and speed control loops in the controller are designed as follows:

[0067]

[0068] Among them, T c is the throttle control amount, δ e is the throttle control parameter, K np ,K pt ,K it ,K pe ,K ie ,K q is the control parameter, q is the pitch angle rate, and this term is introduced to improve the damping characteristics of the longitudinal loop. and They represent the total energy change rate increment and energy conversion change rate increment respectively.

[0069] in,

[0070] in, V c is the desired speed command, is the desired speed change rate command, is the expected height change law instruction, K vE ,K vL is the control parameter,

[0071] in,

[0072] Among them, K V ,K h is the controller parameter, h c is the desired height command. By changing the control parameter K V ,K h , it can change the speed and altitude outer loop response characteristics, adjust the priority of the response of the UAV's longitudinal and speed channels, and implement priority altitude loop adjustment or priority speed loop adjustment according to flight mission requirements.

[0073] In this embodiment, the principle of the fixed-wing aircraft longitudinal and speed channel control device is as follows: Figure 3 As shown, the control principle of the controller is as follows Figure 4 shown.

[0074] In one embodiment, a medium is provided for storing a method for controlling longitudinal and velocity channels of a fixed-wing aircraft according to the present invention.

[0075] In one embodiment, an aircraft is provided, which is controlled using a fixed-wing aircraft longitudinal and velocity channel control method according to the present invention.

[0076] In one embodiment, an aircraft is provided, wherein the fixed-wing aircraft longitudinal and speed channel control device of the present invention is installed on the aircraft.

[0077] In summary, the method and device for controlling the longitudinal and velocity channels of a fixed-wing aircraft provided by the present invention have at least the following advantages over the prior art:

[0078] The present invention decouples the longitudinal direction and velocity of the aircraft through the total energy method, which can effectively solve the problem of serious coupling between the longitudinal and velocity channels of such aircraft, enhance the control adaptability of the UAV under narrow flight boundaries and strong external environmental interference, effectively improve the loop response characteristics, and effectively improve the safety of flight control.

[0079] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for controlling longitudinal and velocity channels of a fixed-wing aircraft, characterized in that: The following steps are involved: Design a low-pass filter to filter the speed of the aircraft. Design a fast differential observer, take the filtered velocity as input, and use the acceleration tracking result output by the fast differential observer as the aircraft velocity derivative; According to the indicated airspeed and flight altitude of the aircraft, obtain the control speed used by the aircraft in control According to the obtained aircraft velocity derivative and the aircraft's control parameter velocity, the control method of the longitudinal and velocity channels is obtained: Among them, T c is the throttle control amount, δ e is the throttle control parameter, K np ,K pt ,K it ,K pe ,K ie ,K q is the control parameter, q is the pitch angle rate, and They represent the total energy change rate increment and energy conversion change rate increment respectively. That middle, V c is the desired speed command, is the desired speed change rate command, is the desired altitude change rate command, K vE ,K vL For the control parameters, Among them, K V ,K h is the controller parameter, h c is the desired altitude command; V is the true airspeed of the drone, g is the acceleration due to gravity, is the energy conversion rate of change; The structure of the fast differential observer is: in Among them, (k) represents the current beat signal, (k-1) represents the sampling value of the previous beat signal, T is the sampling period; v is the velocity signal, is the input signal of the differential observer, z1, z2 are the output signals of the differential observer, and r, h are the filter parameters.

2. A fixed-wing aircraft longitudinal and velocity channel control device for implementing the fixed-wing aircraft longitudinal and velocity channel control method of claim 1, characterized in that: The invention comprises a filter, a fast differential observer, a parameter-controlled speed calculator and a controller. The filter obtains the speed of the aircraft, filters it and sends it to the fast differential observer. The fast differential observer tracks the speed and the differential of the speed according to the aircraft speed obtained by filtering and inputs the result of the speed differential tracking into the controller as the speed derivative of the aircraft. The parameter-controlled speed calculator calculates the parameter-controlled speed of the aircraft according to the indicated airspeed and the flight altitude of the aircraft and transmits it to the controller. The controller calculates the throttle control amount and the throttle control parameter according to the obtained parameter-controlled speed and the speed derivative of the aircraft according to the control method.

3. A fixed-wing aircraft longitudinal and speed channel control device according to claim 2, characterized in that: The filter is a low-pass filter.

4. A medium, characterized in that A computer program is stored, wherein the computer program runs the method for controlling the longitudinal and velocity channels of a fixed-wing aircraft as described in claim 1.

5. An aircraft, characterized in that: The fixed-wing aircraft longitudinal and velocity channel control method according to claim 1 is used for control.

6. An aircraft, characterized in that: Install a fixed-wing aircraft longitudinal and speed channel control device as described in claim 2 or 3.

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