CN115525067A - Design and implementation method of oblique take-off mode of tilt rotor aircraft - Google Patents
Design and implementation method of oblique take-off mode of tilt rotor aircraft Download PDFInfo
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Abstract
The invention relates to the aircraft control technology, and discloses a design and implementation method of a tilt rotor aircraft oblique take-off mode, wherein an oblique take-off path formed by sequentially connecting a plurality of nodes is set in a plane vertical to a horizontal plane and between a self-take-off starting point and a take-off terminal point, a rotor aircraft is started to fly along the set oblique path, tracking, guidance and control are carried out in the take-off process, and a track error generated in the flight is corrected, so that the tilt rotor aircraft always takes off along the set oblique take-off path; the shape of the oblique takeoff path is further optimized according to the requirements of different takeoff tasks, the airplane reaches the terminal point along the optimized oblique path, the time consumption of the airplane is reduced, and the energy consumption is obviously reduced.
Description
Technical Field
The invention relates to the technical field of aircraft control, in particular to a design and implementation method of an oblique take-off mode of a tilt rotor aircraft.
Background
Tiltrotor aircraft is a type of aircraft that can change its layout by rotating its rotors/propellers to point in a direction. The aircraft has wings of the fixed-wing aircraft and the tilting rotors, so that the advantages of the fixed-wing aircraft and the multi-rotor aircraft can be combined, and the aircraft can fly in two modes of vertical ascent and horizontal forward flight and can be switched between the vertical ascent mode and the horizontal forward flight mode. The tilt rotor aircraft can take off and land vertically and hover in the air, and has the advantages of high flying speed and strong cruising ability, and the military and civil application prospect is wide.
In the case of a tiltrotor aircraft, the takeoff process is a typical operation that includes both vertical ascent and horizontal forward flight modes and their interconversion, as shown in fig. 1. This process can be divided into three parts: (1) The tilt rotor aircraft takes the point A as a starting point, the rotor wing is maintained at 90 degrees vertically upwards, and the tilt rotor aircraft ascends to the point B according with the preset takeoff height in a vertical ascending flight mode to hover; (2) The airplane carries out flight mode conversion between a point B and a point C, and during the flight, the rotor wing of the tilt rotor aircraft is converted from 90 degrees vertically upwards to 0 degree horizontally forwards; (3) And (4) rotating the rotor wing of the airplane to 0 degree forward horizontally, enabling the airplane to reach the terminal C, and finishing the takeoff process. A big problem with this conventional takeoff is that at the start of takeoff, the aircraft is in a vertically ascending and hovering state for a long time, i.e. a vertically ascending/descending flight mode, in which the flight performance and efficiency of the tiltrotor aircraft become very low. The following reasons are specific:
firstly, in the vertical ascending and hovering flight modes, the fuselage, the wings and the empennage of the tilt rotor aircraft generate great air resistance, so that the maneuvering action of the take-off is hindered; this results in large power consumption during takeoff, and consequently, important flight performance indexes such as short voyage and dead time are shortened.
Second, the "fixed wing" (i.e., fuselage, wings, and empennage) portion of a tiltrotor aircraft is designed to fly flat rather than hover. Therefore, when the airplane is in a vertical ascending and hovering state, the fixed wing part of the airplane is in a flow field under an off-design working condition. When the aircraft is subjected to side and tail wind, the fixed wing part generates large disturbance force and moment, and the position and the attitude of the aircraft fluctuate greatly and even the aircraft is unstable.
Thirdly, the flight distance of the aircraft in this takeoff mode (from the starting point a to B, and then from B to the end point C) is relatively much longer than the straight distance between the takeoff starting point a and the end point C. In terms of flight efficiency, a long flight distance means that take-off takes longer. Consequently, the flight performance and efficiency of tiltrotor aircraft in this mode becomes very low.
Therefore, the design and implementation method of the oblique takeoff mode of the tilt rotor aircraft, which can improve the flight performance and improve the flight efficiency, become the pursued targets of those skilled in the art.
Disclosure of Invention
The invention mainly aims to solve the problems that the existing tilt rotor aircraft adopts a take-off mode in a vertical rising and hovering state, has high power consumption, thereby shortening important flight performance indexes such as a flight distance, a dead time and the like, and the fixed wing of the tilt rotor aircraft has poor interference resistance because the fixed wing is in a flow field of a non-design working condition. The invention provides a design and implementation method of a tilt take-off mode of a rotorcraft, which can realize the tracking of a take-off path and ensure that the tilt rotorcraft is close to or matched with a set tilt take-off path in the take-off process.
It is another object of the present invention to design an oblique takeoff path that facilitates the resolution and calculation of errors in the path tracking and attitude control process.
It is a further object of the present invention to provide a preferred path tracking and flight control scheme.
The invention further aims to optimize the set oblique takeoff path of the tilt rotor aircraft, further improve the flight efficiency of the aircraft, and further achieve the purposes of shortening the time consumption for takeoff or saving energy consumption.
The tilt rotor aircraft is in the oblique take-off process, from the take-off starting point to the terminal point, because various interference factors deviate and set the route, need maintain oblique flight state this moment, need reduce and track the positional deviation in route simultaneously, carry out the tracking guide and control to the take-off in-process promptly, and revise the tracking error who produces in the flight, control real-time adjustment aircraft position, speed, gesture etc. state, make tilt rotor aircraft keep being close with the take-off route of setting for in the take-off process, realize taking-off route tracking.
Therefore, in order to achieve the above primary object, the invention achieves take-off according to a set oblique take-off path, and adopts the following technical scheme: a design and implementation method for a tilt take-off mode of a tilt rotor aircraft is characterized in that: setting an oblique takeoff path, starting the gyroplane to take off along the set oblique takeoff path, tracking the path in the takeoff process, and determining the position deviation of the tilt gyroplane between the current position and the set oblique takeoff path; calculating the adjustment quantity required by the tilt rotor aircraft to reduce the current position deviation; and carrying out attitude control in real time according to the adjustment quantity, so that the tilt rotor aircraft correctly takes off along the set oblique take-off path.
According to the technical scheme, in the path tracking, firstly, the position deviation between the current position of the airplane and the oblique takeoff path is detected, and then the flight state adjustment quantity required by the airplane, including the position, the speed, the attitude and the like of the airplane, is calculated according to the position deviation. And finally outputting a flight attitude adjusting instruction for restraining the flight process of the airplane, realizing the effect of path tracking and achieving the aim of taking off along the set oblique taking-off path.
In the above technical solution, the oblique takeoff path may be a straight path from a starting point to an end point, and in addition, there are various possible curved or broken path paths. In order to facilitate the position deviation data analysis and calculation in the path tracking process, the method is taken as an optimal technical scheme: the oblique take-off path is arranged in a plane vertical to the ground and is a self-take-off starting point [0,0 ]] T To take-off terminal point [ x ] C ,0,z C ] T A broken line path formed by connecting a plurality of nodes in sequence is arranged between the nodes; the node coordinates of the broken line path are as follows: [0,0,0] T ,[x 1 ,0,z 1 ] T ,…,[x n ,0,z n ] T ,[x C ,0,z C ] T (ii) a Wherein, the horizontal coordinate x of the node in the broken line path i (i =1,2, \8230;, n) satisfies: 0 < x 1 ﹤x 2 ﹤x 3 …﹤x n ﹤x c (ii) a Vertical coordinate z of node in broken line path i (i =1,2, \8230;, n) satisfying: z is a radical of formula i Height above ground > 0.
The invention designs the oblique flight path as a broken line path, which can approach to a curve on one hand, and simultaneously, facilitates the processing and calculation of error information and is beneficial to path tracking. And the path nodes are digitalized, which is beneficial to the optimization of the path shape.
The set oblique takeoff path is a broken line path which is in a vertical plane vertical to the ground or a horizontal plane and is formed by a series of path nodes. That is, during takeoff, the aircraft does not make any side-to-side turning maneuvers. The path tracking firstly needs to determine the deviation between the airplane and the oblique takeoff path, in order to facilitate analysis, the position deviation is decomposed into a transverse deviation and a longitudinal deviation, the elimination of the longitudinal deviation needs to be realized by adjusting the height of the airplane, and the transverse deviation needs to be eliminated by adjusting the yaw motion (namely, left-right rotation) of the airplane, namely, changing the yaw angle. Therefore, the design and implementation method of the oblique takeoff mode of the tilt rotor aircraft further provides an optimal technical scheme in the path tracking process:
the position deviation between the airplane and the set oblique takeoff path is decomposed into: the method comprises the following steps of obtaining a transverse deviation and a longitudinal deviation, wherein the transverse deviation is the distance from the mass center of an airplane to a vertical plane where an oblique take-off path is located, and the longitudinal deviation is the deviation from the projection of the mass center of the airplane on the vertical plane to the oblique take-off path; in the path tracking, the longitudinal deviation of the airplane is eliminated by adjusting the pitch angle of the airplane, and the transverse deviation of the airplane is eliminated by adjusting the yaw movement of the airplane; specifically, the aircraft is first adjusted to an initial yaw angle ψ init Then, based on the adjustment amount Δ θ of the pitch angle for eliminating the longitudinal deviation and the adjustment amount ψ of the yaw angle for eliminating the lateral deviation lat,sp Adjusting the pitch angle and the yaw angle of the airplane in real time, and controlling the attitude, wherein the control method is a three-step rotation method:
firstly, rotating the aircraft to a heading angle psi which is the same as the heading angle of the set oblique takeoff path around the Z axis of the aircraft body init Making the heading angle psi of the X-axis of the airframe and the set oblique takeoff path init The directions are consistent;
second step, windingDesired value theta of machine body Y axis rotating by one pitch angle sp So as to eliminate the error generated by the airplane in the longitudinal direction;
third, a yaw angle psi for reducing lateral position deviations is rotated about the Z axis of the body lat,sp ；
Wherein the desired pitch angle is calculated by:
θ sp ＝θ base +Δθ (1)
the expected track dip angle is the pitch angle command theta sp ，θ base Is to maintain the pitch angle basic value set for oblique flight. In general terms of theta base Is arranged close to the inclination of the path itself.
In the preferred embodiment, the aircraft is first returned to the initial yaw angle by rotating the body about the Z axis, and on this basis, the longitudinal and lateral deviations are adjusted, i.e. the desired pitch angle θ is rotated about the Y axis of the body sp Rotated about the Z-axis of the body to achieve the desired yaw angle psi lat,sp Therefore, the elimination of longitudinal and transverse deviation is realized, and the tracking of the oblique takeoff path is achieved.
The design and implementation method of the oblique takeoff mode of the tilt rotor aircraft is taken as a preferable scheme, wherein the adjustment quantity delta theta of the pitch angle for eliminating the longitudinal deviation is calculated by the following method:
Δθ＝k P,lon (γ sp -γ) (2)
wherein k is P，lon The value is 1-2, gamma for adjustable coefficient sp The expected track inclination angle is obtained, and gamma is the actual track inclination angle;
wherein the desired track inclination angle γ sp Calculated by the following method:
use the barycenter of tilt rotor aircraft as the centre of a circle, it is L to draw the radius 1 Circle of radius L 1 The value of (A) can be determined by the speed of the tiltrotor aircraft, L 1 The relationship to the speed of the tiltrotor aircraft is:
the included angle between the horizontal plane and the connecting line from the circle center to the intersection point of the circle and the set oblique takeoff path is the expected track inclination angle gamma sp By geometric relationship (radius L) 1 The center of a circle and the intersection point of the path, and the included angle with the horizontal) can be calculated to obtain gamma sp (ii) a Wherein the content of the first and second substances,
the value is 10-30 for adjustable control parameters; v. of x And v Z The components of the aircraft velocity in the lateral (X) and longitudinal (Z) directions.
The design and implementation method of the oblique take-off mode of the tilt rotor aircraft is an optimal scheme, wherein the adjustment amount psi of the yaw angle for eliminating the transverse deviation lat,sp Calculated by the following method:
wherein psi lat,sp Yaw angle command, k, for reducing lateral position deviation Pψ，lat For adjustable control parameters, v y，sp At a desired lateral velocity; v. of y Is the actual lateral velocity; k is a radical of formula Pv，lat For adjustable control parameters, y is the aircraft position coordinate of the lateral deviation value, e lat Is the lateral path position deviation.
In the above technical solution, the present invention adopts the most intuitive method: the aircraft is raised/lowered, namely the pitch angle of the aircraft is changed, so that the height of the motion direction of the aircraft is changed, and the longitudinal deviation of the aircraft is eliminated. Giving an algorithm for adjusting the pitch angle, namely calculating the head raising/lowering amplitude, controlling the head raising of the aircraft when the position of the aircraft is lower than a takeoff path, increasing the pitch angle and recovering the height; and vice versa. Wherein, the pitching angle of the airplane is adjusted by drawing the radius L 1 The pitch angle adjustment amount is calculated by the circle, and compared with other methods (such as sideslip distance), the longitudinal movement of the airplane can be smoother. In the preferred embodiment, the lateral path position of the aircraft isThe yaw offset is numerically equal to the negative value of the y-component of the aircraft position, and the lateral offset can be eliminated by adjusting the yaw motion (i.e., left-right rotation) of the aircraft, i.e., changing the yaw angle.
Further, according to the design and implementation method of the oblique takeoff mode of the tilt rotor aircraft, as a preferred scheme, the mathematical expression of the three-step rotation method for controlling the attitude in real time is as follows:
wherein: l is a radical of an alcohol BE,sp For rotate matrix instructions: lz (psi) lat,sp )、Ly(θ sp ) Lc (ψ init) is a rotation matrix around the Z axis, Y axis, Z axis;
by obtaining L BE,sp， The attitude control is carried out, and the specific method comprises the following steps:
mixing L with BE,sp Converted into an angular velocity command omega sp ＝[p sp q sp r sp ] T Converting the angular velocity command into an angular acceleration command:
wherein: k is a radical of formula P，p 、k P，q 、k P，r 、k D，p 、k D，q 、k D，r 、k F，p 、k F，q 、k F，r Is an adjustable control parameter;
converting the angular acceleration command to a desired triaxial moment:
finally, the expected triaxial moment can be generated by adjusting the controllable quantities of the power, the control surface and the like of the tilt rotor aircraft, and the path tracking and control process of the oblique takeoff mode is realized.
The design and implementation method of the oblique take-off mode of the tilt rotor aircraft realizes the path tracking and attitude control of the oblique take-off through the technical scheme, so that the aircraft can take off along a set polygonal line-shaped oblique take-off path formed by sequentially connecting a plurality of nodes, the tilt rotor aircraft moves along the polygonal line path to complete the take-off process, and due to the physical motion continuity, the actual motion track along the polygonal line can be changed into a curve which tends to the polygonal line. Because the shape of the zigzag oblique takeoff path set between the takeoff starting point and the terminal point has countless variation possibilities, the aircraft tracking can reach the terminal point for different takeoff paths, but the takeoff process corresponding to the paths has different flight indexes (such as time consumption and energy consumption). For example: the corresponding take-off process has different time consumption, different energy consumption and different idle time; the formation of the oblique flight curve is also influenced by many factors such as flight speed, acceleration, change of oblique attitude, and transition of flight mode of the aircraft. Therefore, the invention further takes the flight indexes (such as shortest takeoff time, least power consumption, longest idle time and the like) set by the flight mission as targets to optimize the oblique takeoff path, namely, the heights of a plurality of nodes are modified and optimized by adopting a preset method, so that the oblique takeoff path set between the takeoff starting point and the takeoff terminal point is the optimized oblique takeoff path with the shortest takeoff time or the optimized oblique takeoff path with the least power consumption and the longest idle time.
Taking the set flight index as the shortest takeoff time (time consumed for takeoff) as an example, in order to enable the aircraft to take off quickly, the aircraft needs to accelerate quickly along the flight direction. The acceleration capability of tiltrotor aircraft varies with the attitude of the aircraft, the flight speed V, and the track pitch angle γ. In addition, during the acceleration of the aircraft, the attitude of the aircraft is constantly changing, and the flying speed V is also becoming larger and larger. At this time, to maintain the maximum acceleration of the aircraft, the track inclination angle γ must be adjusted. Whereas the adjustment of the track inclination angle γ means the curvilinearization of the flight path (trajectory).
The invention is therefore based on the object of optimizing the set zigzag-shaped oblique takeoff path with different flight criteriaThe specific method comprises the following steps: at the take-off starting point [0,0 ]] T And take-off terminal [ x ] C ，0，z C ] T The oblique take-off path is a broken line formed by sequentially connecting a plurality of nodes, and the shape of the oblique take-off path is optimized by a particle swarm iteration method, so that the tilt rotor aircraft takes off on the optimized oblique take-off path with the minimum time consumption, the minimum power consumption or the longest idle time;
the particle swarm iteration method specifically comprises the following steps:
initializing a particle swarm and presetting a value X of X-axis coordinates of a plurality of nodes 1 ，x 2 ，…，x n The Y-axis coordinate of the node is 0, and the Z-axis coordinate of a group of a plurality of the nodes is taken as a particle Z 1 ，z 2 ，…，z n Let the number of particles in the particle group be n P Each particle corresponding to a vector z j (j＝1，2，…，n p ) Setting the maximum number of iterations n max (ii) a "n" of the jth particle j The dimensional space coordinates "are:
an optimization iteration loop is started, and the ith (i =1,2, \8230;, n) is performed max ) Iteration, jth (j =1,2, \8230;, n) p ) The coordinate vector of the particle is
The node coordinates of the polygonal line path corresponding to take-off are [0,0 ]] T ，
[x C ，0，z C ] T ；
Adopting the nodes of the broken line path obtained by the ith iteration to carry out simulated takeoff, and calculating the corresponding takeoff time consumption, energy consumption or empty time;
judging whether the time spent on taking off or the energy consumption or the air remaining time is the jth (j =1,2, L, n) p ) The particle itself is best in all iterations (1-i) ifIf so, then z is j，i Set as the optimal path shape z of a single particle j，best I.e. z j，best ＝z j，i (ii) a Judging whether the time spent for taking off, or the energy consumption, or the empty time is optimal for all the particles (1 st to jth) in all the iteration attempts, if so, judging that the z is j，i Optimal path shape z set as a particle swarm best I.e. z best ＝z j，i ，
Judging whether i reaches the maximum iteration number n max If not, the position change of the jth particle is as follows:
z j，i+1 ＝z j，i +v j，i (8)
wherein v is j，i The velocity vector for the jth particle is calculated by:
w is an inertia coefficient which is obtained through the maximum inertia coefficient, the minimum inertia coefficient and the maximum iteration number; w is a min 、w max Determined empirically, c 1 、c 2 As perceptual and social coefficients, r 1 、 r 2 Is a random number between 0 and 1;
when i = n max Then the iteration is over and the overall optimum z of the particle swarm best Is
The optimal oblique take-off path is the optimal oblique take-off path with the shortest time consumption or the shortest energy consumption and the longest empty time.
According to the design and implementation method of the oblique take-off mode of the tilt rotor aircraft, the oblique take-off path can be optimized to be the optimal path with the needed target (such as shortest time consumption, or least energy consumption and longest empty time) through the particle iteration method.
According to the design and implementation method of the oblique take-off mode of the tilt rotor aircraft, the set oblique take-off path is arranged in the vertical plane, the flight path is tracked, so that the attitude control quantity is generated, the moving flight attitude of the aircraft is adjusted, the actual attitude of the aircraft is close to the attitude adjustment instruction, and the take-off track is close to the set take-off path. During takeoff, the tilt rotor aircraft ascends from the ground and takes off, then is immediately switched to an oblique takeoff mode, then flies along an oblique path from a starting point to a takeoff terminal point in the oblique takeoff mode, when the tilt rotor aircraft approaches the takeoff terminal point, the flight mode of the aircraft is switched to horizontal forward flight again until the aircraft rotor rotates to the horizontal forward 0 degree, the tilt takeoff mode is used for achieving takeoff along the oblique path between a takeoff starting point A and a takeoff terminal point C, the aircraft body is adjusted to be parallel to the flight direction from a common horizontal state, and at the moment, the inclination angle between the aircraft body and the horizontal plane is gamma. In this state, the cross section of the aircraft fuselage perpendicular to the direction of flight becomes minimal, and the flight resistance is greatly reduced. Meanwhile, because the movement directions of the fixed wing and the tail wing of the airplane are consistent with the flight direction, the lift force generated by the fixed wing and the tail wing can be fully utilized, and the flight efficiency of the airplane is effectively improved; the interference resistance and the moment of the fixed wing part can be obviously increased, so that the attitude fluctuation is reduced, and the takeoff process of the airplane is more stable. And when the takeoff terminal point C is approached, the flight mode of the airplane is converted into horizontal forward flight until the rotor wing of the airplane rotates to the horizontal forward 0 degree, and the takeoff process is finished. The take-off mode has the advantages that the vertical rising mode in the take-off mode of the original tilt rotor aircraft is avoided, the air resistance of the aircraft body, the wings and the empennage is greatly reduced, the power consumption in the take-off process is reduced, and the flight efficiency is greatly improved. Meanwhile, in the take-off process, the actual flying distance of the airplane is shorter than that of the existing take-off mode of vertically rising and then turning to the horizontal direction, so that the flying efficiency of the airplane is further improved.
The design and implementation method of the oblique take-off mode of the tilt rotor aircraft comprises the following steps of: a broken line path which is arranged in a plane vertical to the ground and formed by sequentially connecting a plurality of nodes from a take-off starting point to a terminal point; the advantages are that: the method is convenient for analyzing and calculating the error in the path tracking process, and meanwhile, the broken line path can be approximated to a curve when the nodes are enough, and the broken line path can be regarded as a simplified curve.
The design and implementation method of the oblique takeoff mode of the tilt rotor aircraft adopts a Z-Y-Z three-step rotation method to eliminate the path deviation in the takeoff process, particularly eliminates the longitudinal deviation by adjusting the pitch angle of the aircraft and draws the radius L 1 Compared with other methods such as lateral offset, the method can enable the longitudinal movement of the airplane to be smoother. Therefore, the tiltrotor aircraft can fly along the set oblique takeoff path correctly and smoothly.
Further, the oblique takeoff path is optimized through a particle iteration method, so that the oblique takeoff can be optimized from an oblique straight line and a plurality of curve or broken line paths, the oblique takeoff path with the shortest time consumption, or the oblique takeoff path with the least energy consumption, and the oblique takeoff path with the longest air-remaining time can be optimized, and the oblique takeoff process of the tilt rotor aircraft can achieve the effect of consuming time or consuming energy least.
Drawings
FIG. 1 is a diagram of a prior art takeoff process for a tiltrotor aircraft;
fig. 2 is a diagram of a tilt takeoff process of a tiltrotor aircraft according to the present invention;
fig. 3 is a diagram of different takeoff paths of the tiltrotor aircraft during an oblique takeoff process according to the present invention;
fig. 4 is a schematic view of a broken path line of an oblique takeoff path set in a design and implementation method of an oblique takeoff mode of a tilt rotor aircraft according to the present invention;
FIG. 5 is a control block diagram of a design and implementation method of a tilt take-off mode of a tiltrotor aircraft according to the present invention;
FIG. 6 is a schematic diagram of longitudinal and lateral trajectory deviations generated during oblique take-off of a tiltrotor aircraft;
fig. 7 is a schematic view of a flight state of an aircraft at a certain path node in the oblique take-off process of the tiltrotor aircraft according to the present invention;
fig. 8 is a position diagram of the end points of different takeoff paths during the oblique takeoff of a tiltrotor aircraft according to the present invention;
fig. 9, 10, and 11 are a trajectory diagram of a conventional takeoff of a tilt rotor aircraft, a trajectory diagram of a diagonal linear takeoff of the tilt rotor aircraft according to the present invention, and a trajectory diagram of a diagonal optimized curved takeoff of the tilt rotor aircraft according to the present invention, respectively;
FIG. 12 is a comparison graph of the take-off time of a tiltrotor aircraft in a conventional take-off mode and in an oblique linear take-off mode according to the present invention;
FIG. 13 is a graph comparing the oblique straight takeoff mode with the oblique optimized curve takeoff time of the present invention;
figure 14 is a schematic diagram of a hypothetical physical object in a tiltrotor aircraft tilt flight design process.
Detailed Description
The following detailed description of the preferred embodiments of the present invention will be made with reference to the accompanying drawings, but the scope of the present invention should not be limited by the preferred embodiments.
Referring to fig. 2, the present invention provides a design and an implementation method of a tilt rotor aircraft oblique takeoff mode, which can achieve takeoff from a starting point a to an end point C in a set oblique takeoff path, and when the tilt rotor aircraft takes off along the set oblique takeoff path, the aircraft is disturbed by various interference factors, and thus a tracking error is inevitably generated, as shown in fig. 6, the aircraft can only take off along the set oblique takeoff path while maintaining the oblique takeoff state and reducing and tracking a position deviation of the path.
In the oblique take-off process, the airplane is set not to make any left-right turning operation, namely the oblique take-off path of the airplane is a broken line path formed by a series of path nodes in a vertical plane, the broken line path is adopted to facilitate calculation and data processing, and in the path tracking process, the deviation between the current position of the airplane and the take-off path needs to be detected. For the convenience of information processing, the aircraft position deviation is decomposed into a transverse deviation and a longitudinal deviation, as shown in fig. 6, wherein the longitudinal deviation is the distance between the projection of the center of mass of the aircraft on the vertical plane and the oblique takeoff path, and the transverse deviation is the distance from the center of mass of the aircraft to the vertical plane. After the position error of the aircraft is determined, the flight state of the aircraft needs to be adjusted to reduce the deviation.
Referring to fig. 5 and 6, therefore, the present invention provides a design and implementation method of a tilt rotor aircraft oblique takeoff mode, including: path tracking and attitude control, namely setting an oblique take-off path in a vertical plane (ZOX) vertical to a horizontal plane, starting the tilt rotor aircraft to take off along the oblique take-off path, firstly, performing path tracking during the take-off process, determining the position deviation of the tilt rotor aircraft between the current position and the set oblique take-off path, and calculating the adjustment quantity required by the tilt rotor aircraft to reduce the current position deviation; and performing attitude control in real time according to the adjustment quantity, for example, controlling the speed, the pitch angle, the yaw angle and the like of the aircraft so as to eliminate the position deviation of the aircraft, so that the tilt rotor aircraft can correctly follow the set oblique takeoff path to fly.
Referring to fig. 4, due to the continuity of the physical movement of the aircraft takeoff, it is obviously not advisable to take a straight path from the starting point to the end point; however, in order to facilitate path tracking and simplify the analysis and calculation of the position deviation, the oblique takeoff path is preferably designed as a polygonal line: in particular to a self-takeoff starting point [0,0 ] arranged in a plane vertical to the ground] T To take-off terminal point [ x ] C ,0,z C ] T A broken line path formed by connecting a plurality of nodes in sequence is arranged between the nodes; that is, the horizontal (Y-direction) coordinates of all nodes of the polyline path are zero, i.e., the node coordinates of the polyline path are: [0,0,0] T ,[x 1 ,0,z 1 ] T ,…,[x n ,0,z n ] T ,[x C ,0,z C ] T (ii) a The coordinates of the starting point A are [0,0 ]] T The terminal point C coordinate is [ x ] C ,0,z C ] T Wherein the horizontal coordinate x of the node in the middle of the polyline path i (i =1,2, \8230;, n) satisfies: 0 < x 1 ﹤x 2 ﹤x 3 …﹤x n ﹤x c (ii) a I.e. satisfying an increasing relationship, the vertical coordinate z of the node in the polyline path i (i =1,2, \8230;, n) satisfying: z is a radical of i > 0, vertical coordinate z i In generalThe increasing relationship is satisfied, but not necessarily, the relationship is sequentially increasing.
For the zigzag oblique takeoff path, in the path tracking process, firstly, the position deviation between the airplane and the set oblique takeoff path is decomposed into: as shown in fig. 6, the transverse deviation is a distance from the center of mass of the airplane to a vertical plane where the oblique takeoff path is located, and the longitudinal deviation is a deviation from a projection of the center of mass of the airplane on the vertical plane to the oblique takeoff path; the invention relates to a method for adjusting the height of an airplane, wherein the elimination of longitudinal deviation needs to adjust the height of the airplane, and the method is used for raising/lowering the head of the airplane, namely, changing the pitch angle of the airplane so as to change the height of the movement direction of the airplane. Therefore, the adjustment amount of the pitch angle needs to be determined from the longitudinal deviation. Referring to fig. 7, a schematic view of a flight state of the aircraft at a certain path node is shown, as described above, the oblique takeoff path and the node thereof are located in a vertical plane, and the preset pitch angle θ of the aircraft is shown base And a tilt angle command δ t,sp Calculated from its airspeed and current track inclination (V, γ). Drawing a radius L by taking the mass center of the airplane as the center of a circle 1 Wherein L is 1 The expression of (a) is:
wherein v is x And v z Is the x-and z-component of the aircraft ground speed, k P,L 1 is an adjustable parameter, typically having a value of 10-30. The radius is L 1 The intersection point of the circle (c) and the takeoff path (d) is set as the direction of the expected speed (ground speed) of the aircraft, and the corresponding track inclination angle is gamma sp Thus, when L is determined 1 The track inclination angle is calculated as gamma through the geometric relation sp 。
In practical application, the aircraft needs to be raised/lowered, namely, the pitch angle is adjusted, so that the actual track inclination angle approaches gamma sp . Thus, at the existing pitch angle θ of the aircraft base Adding an adjustment value delta theta of a pitch angle, wherein the delta theta is related to the track inclination deviation of the airplane, and the calculation formula is as follows:
Δθ＝k P,lon (γ sp -γ) (2)
where k is P,lon Is an adjustable parameter and can take a value of 1-2. Final pitch angle command θ sp Is composed of
θ sp ＝θ base +Δθ (1)
Wherein the expected track inclination angle is the pitch angle command theta sp ，θ base Is a reference pitch angle provided for tracking an oblique path, the reference pitch angle θ base The method of obtaining (a) is described in detail later. The purposes which can be achieved by this method are: when the position of the airplane is lower than the takeoff path, controlling the airplane to raise the head, and increasing an adjustment quantity delta theta of a pitch angle to adjust the airplane to the height of an ideal oblique takeoff path; and vice versa.
Wherein the lateral path position deviation e of the aircraft lat This is simply understood as the distance of the aircraft from the vertical plane on which the takeoff path lies. In the numerical value, e lat Equal to the negative value of the y component of the aircraft position. By adjusting the yaw motion (i.e., left-right turning) of the aircraft, e can be eliminated lat . The adjustment amount psi of the yaw angle lat，sp Calculated by the following method:
in the above formula, /) lat，sp Yaw angle command (i.e. desired yaw angle) k to reduce lateral position deviation Pψ，lat Typical values for the adjustable parameters are 0.1-2,v y，sp A command for the y component of the aircraft ground speed (desired lateral velocity); v. of y The actual value of the y component of the ground speed of the aircraft (the actual lateral velocity); k is a radical of formula Pv，lat The typical value is 0.5-2 for adjustable parameters; y is the aircraft position coordinate, e lat Is a lateral path position deviation value;
the action mechanism is as follows: firstly, the expected transverse speed v is calculated through the magnitude of the transverse deviation y，sp . Then in order to make the actual lateral velocity v of the aircraft y Approaching the desired lateral velocity v y，sp Adjusting output magnitude psi lat，sp The psi lat，sp The airplane needs to rotate through the yaw movement angle, and the purpose of eliminating the transverse deviation is achieved.
The control method specifically comprises the following steps:
determining a transverse deviation and a longitudinal deviation in the path tracking process, and eliminating the transverse deviation and the longitudinal deviation through a Z-Y-Z three-step rotation method to ensure that the airplane correctly flies along a preset oblique takeoff path; the Z-Y-Z three-step rotation method comprises the following steps:
firstly, rotating the aircraft to a heading angle psi of a preset oblique takeoff path around the Z axis of the aircraft body init Making the course angle psi of X-axis of the body and the predetermined oblique takeoff path init The directions are consistent; this step is intended to bring the aircraft back to a position parallel to the original yaw angle;
secondly, rotating an adjusting quantity delta theta of a pitch angle around the Y axis of the airplane body to eliminate errors generated by the airplane in the longitudinal direction; wherein, the adjustment quantity delta theta of the pitch angle is obtained by the formulas (2) and (3), and the expected pitch angle theta can be obtained by the formula (1) sp The expected track dip angle is the pitch angle command theta sp ；
Third, the machine body is rotated by an angle psi for reducing the transverse position deviation lat，sp (ii) a Thereby eliminating lateral position errors. Psi lat，sp Can be obtained by the above equation (5).
Thus, the initial heading angle ψ init Desired pitch angle θ sp Angle psi for reducing lateral position deviation lat，sp The attitude control method is characterized in that the attitude control quantity generated in the path heel is used for generating the actual control variable of the controller through attitude control, so that the attitude and the inclination angle of the airplane reach the expected values, the transverse deviation and the longitudinal deviation of the airplane are eliminated, and the position deviation of the airplane relative to the set oblique takeoff path is ensured to be minimum.
The mathematical equation of the Z-Y-Z three-step rotation is as follows:
where L is a rotation matrix, L BE，sp For rotation matrix instructions, lz (ψ) lat，sp )、Ly(θ sp )、 Lz(ψ init ) Is a rotation matrix rotating about the Y and Z axes. To obtain L BE，sp Then, the data is sent to a "posture control" part in fig. 5 to complete posture stabilization and instruction tracking, which is detailed as follows:
first, using a proportional controller, L is adjusted BE，sp Into an angular speed command omega sp ＝[p sp q sp r sp ] T The calculation is prior art. Then, the angular velocity command is converted into an angular acceleration command:
wherein: k is a radical of P，p 、k P，q 、k P，r 、k D，p 、k D，q 、k D，r 、k F，p 、k F，q 、k F，r Is an adjustable control parameter, k P，p 、k P，q 、k P，r The value is 4 to 12,k D，p 、k D，q 、k D，r The value is 0 to-1, k F，p 、k F，q 、k F，r The value is a number greater than 0, which is different depending on the configuration of the aircraft.
Converting the angular acceleration command to a desired triaxial moment:
finally, the expected triaxial moment can be generated by adjusting the controllable quantities such as power, a control surface and the like of the tilt rotor aircraft, and the path tracking and control process of the oblique takeoff mode is realized. The specific triaxial moment generation method is different according to different models and can be obtained by related model parameters, and the path tracking and control process of the oblique takeoff mode is realized.
According to the technical scheme, the tilting rotor aircraft can take off in the set oblique take-off path, namely, the control quantity for controlling the attitude of the aircraft is generated in the path tracking process, so that the deviation between the aircraft and the set take-off path in the take-off process is reduced, and the purpose of taking off according to the set oblique take-off path is achieved. Can follow promptly and take off starting point A directly obliquely and fly to taking off terminal point C, oblique take off has shortened the distance in route of taking off, simultaneously, under the oblique take off mode, the air resistance greatly reduced of fuselage, wing and the fin of tiltrotor aircraft for take off process power consumption reduces, increases journey and dead time and can promote greatly. The oblique takeoff is closer to the flow field of the design working condition of the fixed wing part, so that the aircraft has better interference resistance, stable position and attitude and more stable aircraft.
Referring to fig. 2 and 3, the oblique takeoff path has a variety of possible curved or broken path in addition to the straight path that is apparent. The airplane can reach the terminal point by tracking different takeoff paths, but finally, flight indexes (such as time consumption and energy consumption) related to the takeoff process are different. In addition, the formation of the oblique takeoff curve in fig. 2 is also influenced by many factors such as flight conditions of the aircraft, such as flight speed, acceleration, change of oblique attitude, and transition of flight mode. Therefore, a further object of the present invention is to find an optimized oblique takeoff path under different optimal flight criteria, such as: the optimized oblique takeoff path has the advantages of shortest takeoff time, least power consumption and longest idle time.
Taking the set flight index as the shortest takeoff time (time consumed for takeoff) as an example, in order to enable the aircraft to take off quickly, the aircraft needs to accelerate quickly along the flight direction. The acceleration capability of tiltrotor aircraft varies with the attitude of the aircraft, the flight speed V, and the track pitch angle γ. In addition, during the acceleration of the aircraft, the attitude of the aircraft is constantly changing, and the flying speed V is also becoming larger and larger. At this time, to maintain the maximum acceleration of the aircraft, the track inclination angle γ must be adjusted. Whereas the adjustment of the track inclination angle γ means the curvilinearization of the flight path (trajectory). Fig. 3 shows two possible diagonal curved flight paths in this case: oblique curve 1, oblique curve 2.
As shown in fig. 4: the set oblique take-off is as follows: setting a broken line path formed by sequentially connecting a plurality of nodes between a takeoff starting point and a takeoff terminal point; the step of optimizing the path is that the heights of the nodes are modified by a preset method, and the shape of the broken line path is optimized; according to the requirements on flight performance of different takeoff tasks: for example, the takeoff time consumption is shortest, and the oblique trajectory design and optimization process is converted into a proper solvable mathematical mode.
The invention optimizes the oblique takeoff path by the following design method, and the finally formed optimized takeoff curve has the form of an oblique curve 1 in fig. 3.
The oblique takeoff path is obtained by taking the set flight index as the shortest takeoff time (shortest takeoff time) as an example and optimizing the set flight index by the following method:
referring to FIG. 4, first, at the takeoff start [0,0 ]] T And takeoff terminal [ x ] C ，0，z C ] T A broken line path formed by connecting a plurality of nodes in sequence is set between the first and the second rotary wing aircraft, and the tilt rotary wing aircraft moves along the broken line path to complete the takeoff process (due to the physical movement continuity, the actual movement track along the broken line can be changed into a curve tending to the broken line). And optimizing the shape of the broken line path by a particle swarm iteration method, so that the tilting rotorcraft has the maximum acceleration in the preset oblique takeoff path, namely the shortest time consumption.
The particle swarm iteration method specifically comprises the following steps:
initializing a particle swarm, and presetting X-axis coordinates of a plurality of nodes as X 1 ，x 2 ，…，x n The Y-axis coordinate of the node is 0, and the Z-axis coordinate of a group of a plurality of the nodes is Z 1 ，z 2 ，…，z n As one "particle", let the number of particles in the particle group be n p Each particle corresponding to a vector z j (j＝1，2，…，n p ) Setting the maximum number of iterations n max (ii) a "n" of the jth particle j The dimensional space coordinates "are:
by means of this presetting, the takeoff path shape optimization problem is converted into a mathematical problem: finding the best z 1 ，z 2 ，…，z n . The optimum z 1 ，z 2 ，…，z n And x 1 ，x 2 ，…，x n The broken line formed by the formed coordinate nodes just can minimize the time consumption of taking off along the path.
An optimization iteration loop is started, the ith time (i =1,2, \ 8230;, n) max ) Iteration, jth (j =1,2, \8230;, n) p ) The coordinate vector of the particle is
The node coordinates of the broken line path corresponding to take-off are [0,0 ]] T ，
[x C ，0，z C ] T ；
Adopting the nodes of the broken line path obtained by the ith iteration to carry out simulated takeoff, and calculating the corresponding takeoff time consumption;
judging whether the takeoff time is the jth (j =1,2, L, n) time p ) The particle itself is shortest in all iterations, i.e. 1 st to i-th iteration attempts, and if so, this z j，i Set as the optimal path shape z of a single particle j，best I.e. z j，best ＝z j，i (ii) a Judging whether the time spent on takeoff is the shortest of all the particles, namely the 1 st to the jth particles in all the iterations (namely the 1 st to the ith iterations), if so, judging that the z is j，i Optimal path shape z set as a particle swarm best I.e. z best ＝z j，i ，
Judging whether i reaches the maximum iteration number n max If not, the position change of the jth particle is as follows:
z j，i+1 ＝z j，i +v j，i (8)
wherein v is j，i The velocity vector for the jth particle is calculated by:
(9) In the formula, w is an inertia coefficient, and is obtained through a maximum inertia coefficient, a minimum inertia coefficient and a maximum iteration number; w is a min 、w max Determined empirically, c 1 、c 2 As perceptual and social coefficients, r 1 、r 2 Is a random number between 0 and 1;
when i = n max Then the iteration is over and the overall optimum z of the particle swarm best Is/are as follows
Is the optimal oblique takeoff path.
Referring to fig. 8, fig. 8 is a graph of takeoff start and end points showing 25 different takeoff end point C locations. Taking-off comparison experiments are carried out on the 25 terminal points, as shown in fig. 9, 10 and 11, fig. 9 shows a traditional taking-off track graph, fig. 10 shows a flight track graph of an oblique taking-off path set by the invention, and fig. 11 shows an optimized oblique taking-off path which is optimized in the shortest time consumption manner. Comparing fig. 9, 10, and 11, it can be seen that the conventional takeoff path is long, the flight distance between the oblique takeoff path set by the present invention and the optimized oblique takeoff path that consumes the shortest time is short, and particularly, it can be seen that the flight trajectory is smoother through the optimized oblique takeoff path that takes the shortest time as a target.
Referring to fig. 12, the time consumption of the conventional takeoff mode compared to the oblique takeoff mode for the 25 different endpoints shown in fig. 8 is shown, and it can be seen that the time consumption of the conventional takeoff mode is between 9 and 33 seconds. The oblique takeoff method is adopted for takeoff, the time consumption of the oblique takeoff mode is between 5 and 11 seconds and is obviously less than that of the traditional takeoff mode, and the time consumption of the oblique takeoff is only 55 to 33 percent of that of the conventional takeoff. Therefore, the oblique take-off mode of the tilt rotor aircraft effectively reduces the time consumption and the energy consumption of the aircraft and improves the flight efficiency.
Referring to fig. 13, it is shown that the time consumption of taking off is carried out by adopting a zigzag oblique takeoff path (i.e. the set oblique takeoff path) which is set in a vertical plane and is composed of a series of path nodes, and the optimized oblique takeoff path z which is optimized by the shortest time consumption is adopted best And carrying out a time-consuming comparison experiment of takeoff, wherein the experiment shows that the time consumption of the optimized oblique takeoff path with the shortest time consumption is obviously lower than that of the set oblique broken line path. Therefore, the design and implementation method of the oblique take-off mode of the tilt rotor aircraft can realize oblique take-off, can optimize the target of the oblique take-off path, reduces the time consumption and energy consumption of take-off and improves the flight efficiency compared with the traditional take-off mode, so that the aircraft can correctly take off along the optimal oblique take-off path and can optimize the path.
Obviously, the embodiment performs the path optimization by using the shortest consumed time as the target through the particle iteration method, so the method can also perform the optimization by using the shortest consumed energy as the optimization target, thereby obtaining the optimized path with the least consumed energy in the takeoff process, and the method can achieve the target of the longest vacant time because the least consumed energy is used in the takeoff process.
It should be added that, during the track tracking process, the elimination of the longitudinal error is realized by the reference pitch angle theta base On the basis of the reference pitch angle theta, an adjustment quantity delta theta of the pitch angle is added base The oblique flight mode of the tilt rotor aircraft is obtained by a design method of the oblique flight mode, and the implementation method of the oblique flight mode comprises the following steps: under the condition that each group of airspeed V and track inclination angle gamma are different, obtaining a plurality of groups of pitch angles theta and rotor wing tilt angles delta t So that the stress condition of the airplane meets the following conditions: the moment is balanced, and the resultant force along the normal direction of the flight path is zero. Thus, a combination of control quantities (theta, delta) is established for controlling the aircraft in each set of airspeed and track inclination (V, gamma) for the oblique flight regime t ) The table look-up function of (2): (Pitch angle θ, tilt angle δ t ) = f (airspeed V, track inclination γ).
The table look-up function is built based on hypothetical physical objects, as shown in fig. 14, which are: a tiltrotor aircraft is positioned in an inclined wind tunnel at an angle gamma (i.e. track inclination angle), the wind speed is V, the aircraft is fixed on a horizontal rod, the aircraft only allows to change the pitch angle, and in this model, the aircraft tilt angle delta t Different given values can also be set; will delta t Fixed at a certain value, slowly set theta sp Increasing from small (e.g., -30 °) to large (e.g., 90 °), the pitch angle of the aircraft itself will also increase slowly. At different pitch angles, the forces acting on the aircraft can be monitored, and if the forces acting on the aircraft in the normal direction along a given track pitch angle γ (wind tunnel inclination angle) are zero, the current (pitch angle θ, roll angle δ) is indicated t ) Under the combination, the airplane can realize oblique flight at airspeed V and track inclination angle gamma.
Based on the principle, the table look-up function is established by the following steps: setting a group of flight state parameters in a preset range: airspeed V i And track inclination angle gamma i I is a natural number, wherein V i >0 to a maximum value V max (ii) a The preset range of the track inclination angle gamma is as follows: gamma is more than 0 degree and less than 90 degrees; delta is not more than 0 degree within a preset range t A tilting angle delta is set within 90 DEG or less ti I is a natural number; theta is more than or equal to 90 degrees within the preset range of the pitch angle sp Selecting theta from small to large within 90 DEG sp I =1, θ i = -90 °; according to a predetermined tilting angle delta ti And a pitch angle theta sp Calculate the resultant normal force in the oblique flying direction, and determine whether the resultant normal force is zero? (ii) a If yes, recording the combination of the current flight state parameters and the control quantity: v i 、γ i 、δ ti 、θi＝θ sp If not, increasing a delta theta to obtain a new theta sp Calculating the normal resultant force again, judging whether the normal resultant force is zero or not, if the normal resultant force is zero, recording the group of data, if not, repeatedly changing the pitch angle until the pitch angle covers all range values, namely if theta sp Reaching a maximum value, and the recirculation varying the tilt angle delta t Repeating the pitch angle from the minimum value every time the tilting angle is changedGradually changing to the maximum value, and calculating until the tilting angle delta t Covering a preset range, then, changing the airspeed V and the track inclination angle gamma in a recycling mode, giving a new set of airspeed V and track inclination angle gamma, and repeating the process until the airspeed V and the track inclination angle gamma cover the preset range, so that a table look-up function can be obtained: (Pitch angle θ, tilt angle δ t ) = f (airspeed V, track inclination γ). The look-up table function indicates: when the tilt rotor aircraft obliquely flies at airspeed V and track inclination angle gamma, the control quantity combination (pitch angle theta and tilt angle delta) can be given by looking up the table function t ) So as to ensure that the airplane can realize oblique flight.
The reference pitch angle theta of the invention base Namely, the pitch angle for maintaining the oblique flight is determined by a look-up function corresponding to the current airspeed V and the track inclination angle gamma.
The above description is only illustrative, but not restrictive, and the present invention aims to provide a method for designing and implementing a tilt take-off mode of a tilt rotorcraft, which can correctly track and set a tilt take-off path, and design the tilt take-off path, so that path tracking and error analysis are facilitated; the method corrects the error of deviating from the set takeoff route in the takeoff process by a Z-Y-Z three-step rotation method, and can optimize the takeoff route according to different optimization targets, so that the takeoff process has the shortest time consumption or the least energy consumption or the longest empty time and the like. Many modifications, variations or equivalents may be made without departing from the spirit and scope as defined in the claims, such as optimizing take-off paths with a minimum of energy consumption as a goal, or optimizing routes using other existing optimization methods, but would fall within the scope of the invention.
Claims (7)
1. A design and implementation method for oblique take-off mode of tilt rotor aircraft is characterized in that: setting an oblique take-off path, starting the rotorcraft to take off along the oblique take-off path, tracking the path in the take-off process, and determining the position deviation between the current position of the tilt rotorcraft and the set oblique take-off path; calculating the adjustment quantity required by correcting the position deviation of the tilt rotor aircraft; and carrying out attitude control in real time according to the adjustment quantity, so that the tilt rotor aircraft correctly takes off along the set oblique take-off path.
2. The method for designing and implementing a tilt take-off mode of a tiltrotor aircraft according to claim 1, wherein: the oblique takeoff path is arranged in a plane vertical to the ground from a takeoff starting point [0, 0'] T To take-off terminal point [ x ] C ,0,z C ] T A broken line path formed by connecting a plurality of nodes in sequence is arranged between the nodes; the node coordinates of the broken line path are: [0,0,0] T ,[x 1 ,0,z 1 ] T ,…,[x n ,0,z n ] T ,[x C ,0,z C ] T (ii) a Wherein, the horizontal coordinate x of the node in the broken line path i (i =1,2, \8230;, n) satisfies: 0 < x 1 ﹤x 2 ﹤x 3 …﹤x n ﹤x c (ii) a Vertical coordinate z of node in broken line path i (i =1,2, \8230;, n) satisfying: z is a radical of i > 0, and the vertical coordinate presents a trend overall.
3. The method for designing and implementing a tilt take-off mode of a tiltrotor aircraft according to claim 2, wherein: the position deviation between the airplane and the set oblique takeoff path is decomposed into: the method comprises the following steps of (1) transverse deviation and longitudinal deviation, wherein the transverse deviation is the distance from the mass center of an airplane to a vertical plane where an oblique takeoff path is located, and the longitudinal deviation is the deviation from the projection of the mass center of the airplane on the vertical plane to the oblique takeoff path; in the path tracking, the longitudinal deviation of the airplane is eliminated by adjusting the pitch angle of the airplane, and the transverse deviation of the airplane is eliminated by adjusting the yaw motion of the airplane; specifically, the aircraft is first adjusted to an initial yaw angle ψ init Then, based on the adjustment amount Δ θ of the pitch angle for eliminating the longitudinal deviation and the adjustment amount ψ of the yaw angle for eliminating the lateral deviation lat,sp Adjusting the pitch angle and the yaw angle of the airplane in real time, and controlling the attitude, wherein the control method is a three-step rotation method:
firstly, the Z axis of the airplane body is wound to rotate and arrange the airplaneThe fixed oblique takeoff path has the same heading angle psi init Making the heading angle psi of the X-axis of the airframe and the set oblique takeoff path init The directions are consistent;
second, rotating the machine body Y axis by a desired value theta of a pitch angle sp So as to eliminate the error generated by the airplane in the longitudinal direction;
thirdly, rotating a yaw angle psi around the Z axis of the body for reducing the lateral position deviation lat,sp ；
Wherein the pitch angle desired value is calculated by:
θ sp ＝θ base +Δθ (1)
the expected track dip angle is the pitch angle command theta sp ，θ base Is a reference pitch angle set for tracking an oblique path.
4. The method for designing and implementing a tilt take-off mode of a tiltrotor aircraft according to claim 3, wherein:
the adjustment amount Δ θ of the pitch angle is calculated by the following method:
Δθ＝k P,lon (γ sp -γ) (2)
wherein k is P，lon To be adjustable factor, gamma sp The expected track inclination angle is obtained, and gamma is the actual track inclination angle;
wherein the desired track inclination γ sp Calculated by the following method:
the centroid of the tilt rotor aircraft is used as the circle center, and the drawing radius is L 1 Circle of (D), L 1 The relationship between the value of (a) and the speed of the tiltrotor aircraft is:
the included angle between the horizontal plane and the connecting line from the circle center to the intersection point of the circle and the set takeoff path is the expected track inclination angle gamma sp Passing through the radius L 1 I.e. gamma can be calculated sp (ii) a Wherein the content of the first and second substances,
for adjustable control parameters, v x And v Z The components of the aircraft velocity in the lateral (X) and longitudinal (Z) directions.
5. The method for designing and implementing the oblique takeoff mode of the tiltrotor aircraft according to claim 3 or 4, wherein:
the adjustment amount psi of the yaw angle lat,sp Calculated by the following method:
wherein psi lat,sp Yaw angle command, k, for reducing lateral position deviation Pψ，lat For adjustable control parameters, v y，sp At a desired lateral velocity; v. of y Is the actual lateral velocity; k is a radical of Pv，lat For adjustable control parameters, y is the aircraft position coordinate, e lat Is a lateral path position offset value.
6. The method for designing and implementing a tilt take-off mode of a tiltrotor aircraft according to claim 3, 4 or 5, wherein:
the mathematical equation of the three-step rotation method is as follows:
wherein: l is BE，sp Is a rotation matrix instruction; lz (psi) lat，sp )、Ly(θ sp ) Lc (ψ init) is a rotation matrix around the Z axis, Y axis, Z axis;
by obtaining L BE，sp The attitude control is carried out, and the specific method comprises the following steps:
will L BE，sp Converted into an angular velocity command omega sp ＝[p sp q sp r sp ] T Converting the angular velocity command toConverting into an angular acceleration command:
wherein: k is a radical of formula P，p 、k P，q 、k P，r 、k D，p 、k D，g 、k D，r 、k F，p 、k F，q 、k F，r Is an adjustable control parameter;
converting the angular acceleration command to a desired triaxial moment:
therefore, attitude control is realized, and path tracking is achieved.
7. The method for designing and implementing a tilt takeoff mode of a tiltrotor aircraft according to claim 6, wherein:
at the take-off starting point [0,0 ]] T And take-off terminal [ x ] C ，0，z C ] T The oblique take-off path is a broken line formed by sequentially connecting a plurality of nodes, and the shape of the oblique take-off path is optimized by a particle swarm iteration method, so that the tilt rotor aircraft takes off on the optimized oblique take-off path with the minimum time consumption, the minimum power consumption or the longest idle time;
the particle swarm iteration method specifically comprises the following steps:
initializing a particle swarm and presetting a value X of X-axis coordinates of a plurality of nodes 1 ，x 2 ，…，x n The Y-axis coordinate of the node is 0, and the Z-axis coordinate of a group of a plurality of the nodes is Z 1 ，Z 2 ，…，Z n As a "particle", let the number of particles in the particle group be n p Each particle corresponding to a vector z j (j＝1，2，…，n p ) Setting the maximum number of iterations n max (ii) a "n" of the jth particle j The dimensional space coordinates "are:
an optimization iteration loop is started, and the ith (i =1,2, \8230;, n) is performed max ) Iteration, jth (j =1,2, \8230;, n) p ) The coordinate vector of the particle is
The node coordinates of the polygonal line path corresponding to take-off are [0,0 ]] T ，
Adopting the nodes of the broken line path obtained by the ith iteration to carry out simulated takeoff, and calculating the corresponding takeoff time consumption, energy consumption or vacancy time;
judging whether the time spent on taking off or the energy consumption or the air remaining time is the jth (j =1,2, L, n) p ) The particle itself is best in all iterations, i.e. 1 st to ith iteration attempts, and if so, this z j，i Set as the optimal path shape z of a single particle j，best I.e. z j，best ＝z j，i (ii) a Judging whether the time spent on taking off, or the energy consumption, or the empty time is all the particles, namely the 1 st to the jth particles are optimal in all the iteration attempts, if so, the z is j，i Optimal path shape z set as a particle swarm best I.e. z best ＝z j，i ，
Judging whether i reaches the maximum iteration number n max If not, the position change of the jth particle is as follows:
z j，i+l ＝z j，i +v j，i (8)
wherein v is j，i The velocity vector for the jth particle is calculated by:
w is an inertia coefficient, and is obtained through the maximum inertia coefficient, the minimum inertia coefficient and the maximum iteration times; w is a min 、w max Determined empirically, c 1 、c 2 As perceptual and social coefficients, r 1 、r 2 Is a random number between 0 and 1;
when i = n max Then the iteration is over and the overall optimum z of the particle swarm best Is/are as followsThe optimal oblique take-off path is the optimal oblique take-off path which consumes the least time or energy or has the longest empty time.
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