CN115859461A - Longitudinal controllable domain and stability analysis method for low-speed fixed wing unmanned aerial vehicle - Google Patents
Longitudinal controllable domain and stability analysis method for low-speed fixed wing unmanned aerial vehicle Download PDFInfo
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Abstract
The invention discloses a longitudinal controllable domain and stability analysis method of a low-speed fixed wing unmanned aerial vehicle, which comprises the following steps: determining an expected working range of an attack angle and a track inclination angle state; substituting the expected values of the attack angle and the track inclination angle into the trim calculation to obtain trim elevator deflection, trim airspeed and trim thrust; expressing the offset of the trim elevator, the trim airspeed and the trim thrust in a contour line distribution mode by taking an attack angle as a horizontal axis and a track inclination angle as a vertical axis to obtain an all-state trim contour line distribution diagram; introducing aircraft performance constraint and control constraint conditions into the full-state trim contour distribution map to obtain a controllable domain; and selecting an expected working point in the controllable domain, calculating the speed and attack angle change trend in the working point neighborhood to obtain a speed attack angle phase diagram, and judging the stability of the working point through the speed attack angle phase diagram. The method is applied to the technical field of unmanned aerial vehicles, and has the advantages of low complexity of balancing solution, strong intuition of result display, high application analysis efficiency and the like.
Description
Technical Field
The invention relates to the technical field of unmanned aerial vehicles, in particular to a longitudinal controllable domain and stability analysis method for a low-speed fixed wing unmanned aerial vehicle.
Background
In the field of aircraft design and application, flight envelope characterizes flight performance to a certain extent, and in the design process of an unmanned aerial vehicle control system, more attention is paid to stability of a balance state and controllability. The balance state calculation is generally called trim, and the current trim method generally determines the flight airspeed and the track inclination at a target working point and further calculates the corresponding trim incidence angle, elevator yaw and thrust through an iterative method. The method has the disadvantages of serious coupling, low solving efficiency and the like, the stability cannot be directly judged, and the calculation complexity is increased by further using a small disturbance linearization or pole distribution method.
In addition, the unmanned aerial vehicle is generally divided into stages such as unpowered gliding, dragging and running in the autonomous landing process. The control targets include altitude, speed, rate of convergence, and attitude of the aircraft. Wherein, the sinking rate is related to the speed, and further influences the height change condition, and a coupling and constraint relationship exists among the sinking rate, the speed and the height change condition. In the design of the conventional control method, the key points are whether the target state is reachable and stable, the state transition process and the balance constraint relation between the target states are often ignored, and an intuitive formula or a chart is lacked for carrying out explicit analysis on the state transition process, which affects the actual flight control effect.
In conclusion, the design process of the traditional unmanned aerial vehicle control characteristic, stability analysis and control method has certain defects in application, and actual requirements are difficult to meet.
Disclosure of Invention
Aiming at the technical defects existing in the design process of the existing unmanned aerial vehicle control method, the invention provides the longitudinal controllable domain and stability analysis method of the low-speed fixed wing unmanned aerial vehicle, and the method has the advantages of low coupling degree, high solving efficiency, strong graphic intuition and the like.
In order to achieve the purpose, the invention provides a longitudinal controllable domain and stability analysis method of a low-speed fixed wing unmanned aerial vehicle, which comprises the following steps:
step 1, determining an expected working range of an attack angle and a track inclination angle state of an unmanned aerial vehicle;
step 2, traversing the expected working ranges of the states of the attack angle and the track inclination angle, and substituting the expected values of the attack angle and the track inclination angle into balancing calculation to obtain the deviation of the balancing elevator, the balancing airspeed and the balancing thrust;
step 3, with the attack angle as a horizontal axis and the track inclination angle as a vertical axis, expressing the trim elevator deflection, the trim airspeed and the trim thrust in a contour line distribution mode to obtain an all-state trim contour line distribution diagram;
step 4, introducing aircraft performance constraint and control constraint conditions into the full-state trim contour distribution map to obtain a controllable domain of the unmanned aerial vehicle;
Compared with the prior art, the invention has the following beneficial technical effects:
1. in the process of rapidly calculating the trim state, the trim state calculation sequence is adjusted, so that the problem of coupling among a lift coefficient, a resistance coefficient and a pitching moment coefficient caused by the simultaneous change of an attack angle and an elevator deflection is solved, the solving complexity of a single trim state is greatly reduced, and the full-state trim calculation efficiency is improved;
2. in the invention, in the process of determining the controllable domain based on the full-state trim contour distribution diagram, the trim state and distribution in the flight envelope range are displayed in a visual mode, the controllable domain distribution condition under the constraint of the unmanned aerial vehicle control condition is visually represented, and the stable transition of the control process can be realized by selecting the required working point and the transfer process state in the controllable domain, so that the problems of poor tracking precision, difficult speed reduction and the like caused by the fact that the instruction does not meet the balance constraint in the actual control process are avoided;
3. in the process of analyzing the stability based on the incident angle velocity phase diagram, the change conditions of the incident angle and the velocity near a certain trim state are represented in the form of a trend line with an arrow, the stability of the trim state is reflected visually, the control law design of the working point can be adjusted correspondingly through the stability analysis, and the stability control near the balance working point is finally realized.
Drawings
In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the embodiments or technical solutions of the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a flowchart of a longitudinal controllable domain and stability analysis method of a low-speed fixed-wing drone in an embodiment of the present invention;
fig. 2 is a contour distribution diagram of a controllable domain obtained according to the characteristics of an unmanned aerial vehicle in the embodiment of the present invention;
fig. 3 is a phase diagram of the angular velocities of attack obtained for points S1 and S2 in fig. 2 in the embodiment of the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as upper, lower, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the motion situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.
The embodiment discloses a longitudinal controllable domain and stability analysis method for a low-speed fixed wing unmanned aerial vehicle, which specifically comprises the following steps 1 to 5 with reference to fig. 1.
Step 1, determining expected working ranges of an attack angle and a track inclination angle state of an unmanned aerial vehicle according to the designed flight performance of the unmanned aerial vehicle;
step 2, traversing the expected working range of the incidence angle and track inclination angle states, substituting the incidence angle and track inclination angle expected values into balancing calculation to obtain balancing elevator deflection, balancing airspeed and balancing thrust, wherein the specific implementation mode of the balancing calculation is as follows:
step 2.1, obtaining the change conditions of the lift coefficient, the resistance coefficient and the pitching moment coefficient of the unmanned aerial vehicle along with the change conditions of the attack angle and the elevator deviation;
step 2.2, establishing a balance equation set of force and moment of aerodynamic force, gravity and engine thrust, which comprises the following steps:
wherein Q is kineticPressure, airspeed is hidden in dynamic pressure Q, S is the wing infiltration area of the unmanned aerial vehicle, gamma is the track inclination angle, T is the thrust, C L (α，δ e )、C D (α，δ e )、C m (α，δ e ) Lift coefficient, drag coefficient, pitching moment coefficient of the drone, and C determined for step 2.1 L (α，δ e )、C D (α，δ e )、C m (α，δ e ) Are both offset by delta from the angle of attack alpha and the elevator of the unmanned aerial vehicle e Correlation;
step 2.3, limiting the attack angle and the track inclination angle of the trim state based on the expected working range of the attack angle and the track inclination angle of the unmanned aerial vehicle, solving the elevator deviation corresponding to the current trim attack angle by using a gradient descent method through a third formula of a balance equation set in the formula (1), wherein the iterative formula is as follows:
δ e (k+1)＝δ e (k)+μ(0-C m (α trim ,δ e (k))) (2)
in the formula, delta e (k + 1) is the elevator yaw, δ, of the (k + 1) th iteration e (k) The elevator deflection is the k iteration, mu is the iteration coefficient and is used for adjusting the iteration convergence characteristic, alpha trim Angle of attack for trim state;
and 2.4, substituting the incidence angle and the track inclination angle in the trim state and the elevator deflection obtained in the step 2.3 into a second formula of the balance equation set in the formula (1) to obtain a trim airspeed, wherein the trim airspeed is as follows:
in the formula, V a,trim To trim the space velocity, θ trim For trim state pitch angle, ρ is air density, m is unmanned aerial vehicle mass, g is gravitational acceleration, C D,trim To trim state drag coefficient, C L,trim The lift coefficient is in a trim state;
step 2.5, substituting the incidence angle and the track inclination angle of the trim state, the elevator deviation obtained in step 2.3 and the trim airspeed obtained in step 2.4 into a first equation of a balance equation set in the equation (1) to obtain trim thrust, wherein the trim thrust is as follows:
in the formula, T trim Is the trim thrust.
And 3, expressing the trim elevator deflection, the trim airspeed and the trim thrust in a contour line distribution mode by taking the attack angle as a horizontal axis and the track inclination angle as a vertical axis to obtain an all-state trim contour line distribution diagram, specifically:
on the basis of the balancing calculation in the step 2, the states of the balancing elevator deviation, the airspeed and the engine thrust corresponding to different balancing incidence angles and track inclination angles in an expected working range are calculated in a traversing mode, then the incidence angle is taken as a horizontal coordinate, the track inclination angle is taken as a vertical coordinate, contour line distribution of the balancing airspeed, the engine thrust, the elevator deviation and the corresponding pitch angle is drawn, and the full-state balancing contour line distribution diagram is obtained. In the all-state trim contour distribution diagram, the attack angle, track inclination angle, airspeed, elevator deflection, engine thrust and pitch angle corresponding to a certain point are in the same set of trim state.
Step 4, introducing aircraft performance constraint and control constraint conditions into the all-state trim contour distribution map to obtain a controllable domain of the unmanned aerial vehicle, specifically:
in the full-state trim contour distribution diagram, a zero thrust contour to maximum thrust contour region, an elevator deflection limiting region and an airspeed non-negative region are determined, the intersected part of the three regions is a controllable region which is the unmanned aerial vehicle, and further, stable conversion processes in different states can be designed in the diagram.
step 5.1, selecting an expected working point of the unmanned aerial vehicle in the full-state trim contour distribution diagram, and limiting the thrust and pitch angle of the working point;
step 5.2, establishing a dynamic differential equation of the attack angle and the speed, wherein the equation comprises the following steps:
in the formula, V a Is the speed of the unmanned aerial vehicle, alpha is the angle of attack of the unmanned aerial vehicle, D is the resistance, theta c Pitch angle, T, corresponding to desired operating point c The thrust corresponding to the expected working point, L is the lift force; substituting the thrust and pitch angle of the working point expected by the unmanned aerial vehicle in the step 5.1 into the kinetic differential equation, and traversing and calculating the airspeed and the change rate in the attack angle neighborhood of the working point expected by the unmanned aerial vehicle;
and 5.3, obtaining an attack angle velocity phase diagram according to the airspeed at the working point expected by the unmanned aerial vehicle and the change rate in the vicinity of the attack angle, and judging the stability of the working point expected by the unmanned aerial vehicle in the step 5.1 according to the attack angle velocity phase diagram.
Fig. 2 is an all-state trim contour distribution diagram calculated according to the characteristics of an unmanned aerial vehicle, wherein a thick solid line in fig. 2 represents trim thrust contour distribution, a longitudinal dotted line represents speed distribution, a longitudinal thin solid line represents trim rudder deflection angle, and an oblique dotted line represents pitch angle. The amplitude limit of the rudder deflection is controlled to be plus or minus 30 degrees, and the rudder deflection is distributed in the amplitude limit range in the figure 2, so that the area between the zero thrust line and the maximum thrust line is a controllable area. The velocity contour distribution becomes sparse with increasing angle of attack in fig. 2, wherein in a Y-shaped region surrounded by 11m/s and 10m/s velocity lines, the velocity change is small and the angle of attack change is large, so that the trim state is sensitive to the velocity change in the region.
And selecting points S1 and S2 in the figure 2 as expected working points, namely defining thrust and pitch angles, calculating the change trend of the speed and the attack angle in the nearby area, and obtaining an attack angle speed phase diagram for states S1 and S2 shown in the figure 3. In fig. 3, the trend change condition can intuitively determine that the S1 working point is an unstable saddle point and the S2 state is a stable focus.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (7)
1. A longitudinal controllable domain and stability analysis method for a low-speed fixed wing unmanned aerial vehicle is characterized by comprising the following steps:
step 1, determining expected working ranges of an attack angle and a track inclination angle state of an unmanned aerial vehicle;
step 2, traversing the expected working ranges of the states of the attack angle and the track inclination angle, and substituting the expected values of the attack angle and the track inclination angle into balancing calculation to obtain the deviation of the balancing elevator, the balancing airspeed and the balancing thrust;
step 3, with the attack angle as a horizontal axis and the track inclination angle as a vertical axis, expressing the trim elevator deflection, the trim airspeed and the trim thrust in a contour line distribution mode to obtain an all-state trim contour line distribution diagram;
step 4, introducing aircraft performance constraint and control constraint conditions into the full-state trim contour distribution map to obtain a controllable domain of the unmanned aerial vehicle;
and 5, selecting an expected working point of the unmanned aerial vehicle in the controllable domain, calculating the speed and attack angle change trend in the neighborhood of the expected working point to obtain a speed attack angle phase diagram, and judging the stability of the expected working point through the speed attack angle phase diagram.
2. The method for analyzing the longitudinal controllable domain and stability of the low-speed fixed-wing drone of claim 1, wherein in step 2, the trim calculation is specifically:
step 2.1, obtaining the change conditions of the lift coefficient, the resistance coefficient and the pitching moment coefficient of the unmanned aerial vehicle along with the change conditions of the attack angle and the elevator deviation;
step 2.2, establishing a balance equation set of force and moment of aerodynamic force, gravity and engine thrust, which comprises the following steps:
in the formula, Q is dynamic pressure, S is wing infiltration area of the unmanned aerial vehicle, gamma is track inclination angle, T is thrust, and C is L (α，δ e ) Lift coefficient for unmanned aerial vehicles, C D (α，δ e ) Coefficient of resistance for unmanned aerial vehicle, C m (α，δ e ) Is the pitching moment coefficient of the unmanned aerial vehicle, C L (α，δ e )、C D (α，δ e )、C m (α，δ e ) Are both offset by delta from the angle of attack alpha and the elevator of the unmanned aerial vehicle e Correlation;
step 2.3, limiting the attack angle and the track inclination angle of the trim state, and obtaining the elevator deviation corresponding to the current trim attack angle by applying a gradient descent method through a third formula of the balance equation set, wherein the third formula comprises the following steps:
δ e (k+1)＝δ e (k)+μ(0-C m (α trim ,δ e (k)))
in the formula, delta e (k + 1) is the elevator yaw, δ, of the (k + 1) th iteration e (k) The elevator deflection is the k iteration, mu is the iteration coefficient and is used for adjusting the iteration convergence characteristic, alpha trim Angle of attack for trim state;
step 2.4, substituting the incidence angle, the track inclination angle and the corresponding elevator deflection in the trim state into a second formula of the balance equation set to obtain the trim airspeed;
and 2.5, substituting the incidence angle and the track inclination angle of the trim state, the corresponding elevator deflection and the trim airspeed into the first equation of the balance equation set to obtain trim thrust.
3. The method for analyzing the longitudinal controllable domain and stability of the low-speed fixed-wing drone of claim 2, wherein in step 2.4, the trim airspeed is:
in the formula, V a,trim To trim airspeed, [ theta ] trim For trim state pitch angle, ρ is air density, m is unmanned aerial vehicle mass, g is gravitational acceleration, C D,trim To trim state drag coefficient, C L,trim The lift coefficient is the trim state.
4. The method for analyzing the longitudinal controllable domain and stability of the low-speed fixed-wing drone of claim 3, wherein in step 2.5, the trim thrust is:
in the formula, T trim To trim the thrust.
5. The method for analyzing the longitudinal controllable domain and stability of the low-speed fixed-wing unmanned aerial vehicle according to any one of claims 1 to 4, wherein the step 4 specifically comprises:
and determining the intersection part of the zero thrust contour line to the maximum thrust contour line region, the elevator deflection limiting region and the airspeed non-negative region in the all-state trim contour line distribution diagram, namely the controllable region of the unmanned aerial vehicle.
6. The method for analyzing the longitudinal controllable domain and stability of the low-speed fixed-wing unmanned aerial vehicle according to any one of claims 1 to 4, wherein the step 5 is specifically as follows:
step 5.1, selecting an expected working point of the unmanned aerial vehicle in the full-state trim contour distribution diagram, and limiting the thrust and pitch angle of the working point;
step 5.2, establishing a dynamics differential equation of an attack angle and a speed, substituting the thrust and the pitch angle of the working point expected by the unmanned aerial vehicle in the step 5.1 into the dynamics differential equation, and traversing and calculating the airspeed and the change rate in the neighborhood of the attack angle of the unmanned aerial vehicle at the expected working point;
and 5.3, obtaining an attack angle velocity phase diagram according to the airspeed at the working point expected by the unmanned aerial vehicle and the change rate in the attack angle neighborhood, and judging the stability of the working point expected by the unmanned aerial vehicle in the step 5.1 according to the attack angle velocity phase diagram.
7. The method for analyzing the longitudinal controllable domain and stability of the low-speed fixed-wing unmanned aerial vehicle according to claim 6, wherein in step 5.2, the dynamic differential equations of the attack angle and the speed are as follows:
in the formula, V a Is the speed of the unmanned aerial vehicle, alpha is the angle of attack of the unmanned aerial vehicle, D is the resistance, theta c Pitch angle, T, corresponding to desired operating point c For a thrust corresponding to the desired operating point, L is the lift.
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| CN116540763A (en) * | 2023-07-04 | 2023-08-04 | 天之翼(苏州)科技有限公司 | Intelligent monitoring management method and system for flight attitude of unmanned aerial vehicle |
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| CN116540763A (en) * | 2023-07-04 | 2023-08-04 | 天之翼(苏州)科技有限公司 | Intelligent monitoring management method and system for flight attitude of unmanned aerial vehicle |
| CN116540763B (en) * | 2023-07-04 | 2023-09-08 | 天之翼(苏州)科技有限公司 | Intelligent monitoring management method and system for flight attitude of unmanned aerial vehicle |
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