A method for the horizontal plane fixed-trajectory turning of an aircraft

Abstract

The present invention discloses a method for an aircraft to turn along a fixed trajectory in the horizontal plane, which comprises the following steps: S1: obtaining the control instruction equation of the aircraft; S2: calculating the control gain; S3: inputting the lateral overload instruction into the lateral overload control system of the aircraft, and the aircraft executes a turn according to the lateral overload instruction and the control gain; S4: establishing a judgment model for the speed of the aircraft during a turn, and using the judgment model to judge whether the turn of the aircraft is completed; S5: extracting the lateral position instruction of the aircraft after the turn is completed according to the designed flight trajectory, inputting the lateral position instruction into the lateral position control system, and correcting the position of the aircraft. The present invention first proposes that, on the premise of a given desired turning radius of the aircraft, the overload required for turning is calculated in real time based on the current speed of the aircraft, the judgment condition for ending the turn in advance is set, and the predetermined turn is completed, so that the aircraft can directly fly back to the main airway after the turn is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of aircraft control, and particularly to a method for an aircraft to turn along a fixed trajectory in the horizontal plane. Background Art

[0002] In a real flight scenario, controlling an aircraft to perform a predefined turning maneuver is a necessary part of flight and also reflects the combat capabilities of the aircraft. As a military aircraft used as a shooting training target, a target drone uses a pre-set flight path and mode to simulate an incoming missile of the enemy during a weapon test firing, providing a simulated target and shooting opportunity for various types of artillery or missile systems. The flight path of the target drone is largely restricted by the target supply area. Since the target supply area is fixed, some target drones with a long flight time usually need to turn repeatedly within this area to complete the predefined combat mission. If the ballistic dispersion is large during turning, there is a possibility that the target drone will fly out of the target supply area. Therefore, it is very important to study a method for an aircraft to turn along a fixed trajectory in the horizontal plane.

[0003] Taking a certain target drone as an example, in flight planning, a reference flight trajectory will be designed for the target drone, including a trajectory for completing a 180° turn and U-turn in the horizontal plane. Under ideal conditions, the designed trajectory after the target drone completes a 180° U-turn in the horizontal plane can be accurately connected to the main flight path. However, in actual flight, affected by many factors, using the overload value under the reference conditions during actual turning will cause a deviation between the actual trajectory and the ideal trajectory. When the actual turning speed is greater than the ideal turning speed, the turning radius will be larger; when the actual speed is less than the ideal turning speed, the turning radius will be smaller. In both cases, the position of the target drone after completing the turn will deviate significantly from the main flight path, and it is necessary to correct the lateral position again to return to the main flight path, generating a decaying serpentine flight trajectory around the main flight path.

[0004] In existing flight tests, the lateral overload value of the reference ballistic during a horizontal turn will cause a large deviation between the turning ballistic and the expected trajectory in the Monte Carlo simulation based on the overall parameter deviation, the end point of the turn is uncontrollable, and the flight trajectory is curved when correcting to the main flight path later. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the present invention provides a method for an aircraft to turn along a fixed trajectory in the horizontal plane, enabling the aircraft to fly directly back to the main flight path after completing the turn.

[0006] To achieve the above-mentioned invention objective, the technical solution adopted by the present invention is as follows:

[0007] Provide a method for an aircraft to turn along a fixed trajectory in the horizontal plane, which includes the following steps:

[0008] S1: According to the BTT control model of the aircraft in the three-channel case, convert the control command in the launch coordinate system to the ballistic coordinate system to obtain the control command equation of the aircraft;

[0009] S2: Design the lateral position control system of the aircraft, establish the closed-loop transfer functions of the five loops of the lateral position control system, and calculate the control gains;

[0010] S3: According to the control command of the aircraft, describe the dynamic equation of the centroid motion of the aircraft in the ballistic coordinate system Ox2y2z2, use the dynamic equation to calculate the lateral overload command when the aircraft turns, input the lateral overload command into the lateral overload control system of the aircraft, and the aircraft executes the turn according to the lateral overload command and the control gain;

[0011] S4: Establish a judgment model for the speed of the aircraft when turning, and use the judgment model to judge whether the turn of the aircraft is completed:

[0012] If the speed of the aircraft turning satisfies the judgment model, it is determined that the turn is completed, and step S5 is executed;

[0013] If the speed of the aircraft turning does not satisfy the judgment model, it is determined that the turn is not completed, return to step S3, and continue to execute the turn.

[0014] S5: Extract the lateral position command after the turn of the aircraft according to the designed flight trajectory, input the lateral position command into the lateral position control system, and correct the position of the aircraft.

[0015] Further, the control command of the aircraft in step S1 is:

[0016]

[0017] where, nyc is the longitudinal overload required for the aircraft to track the altitude, nzc is the heading overload required for lateral position correction or lateral maneuver, ny c is the longitudinal overload command value input to the pitch control loop, nz c is the lateral overload command value input to the yaw control loop, γ c is the roll angle command value input to the roll channel.

[0018] Further, step S2 includes:

[0019] S21: Use the pole placement method to design the control gains K z 、K v 、K n 、K β 、K ω ;

[0020] S22: Establish the closed-loop transfer function models ω y _close(s) and β_close(s) of the sideslip angle loop for the lateral position control system:

[0021]

[0022]

[0023] Among them, b1 is the dynamic coefficient of the course damping moment, b2 is the dynamic coefficient of the course static stability moment, b3 is the dynamic coefficient of the course control moment, b4 is the dynamic coefficient of the lateral force, and b5 is the dynamic coefficient of the rudder side force;

[0024] S23: Establish the characteristic equation of the pole placement method:

[0025]

[0026] Among them, ξ and ω n are the damping ratio and frequency corresponding to the ideal poles respectively;

[0027] S24: Make the characteristic equation equal to the corresponding system of the closed-loop transfer function model β_close(s) of the sideslip angle loop, and ignore the small quantities b1 and b4 in the dynamic coefficients to obtain the feedback control gains K ω and K β ;

[0028]

[0029] S25: Calculate the gain K n :

[0030]

[0031] Among them, t is the rise time of the response of the lateral overload control system; the gains K v , K z are directly assigned according to the control effect of the lateral position control system.

[0032] Furthermore, step S3 includes:

[0033] S31: Describe the dynamic equation of the centroid motion of the aircraft in the ballistic coordinate system Ox2y2z2:

[0034]

[0035] Among them, V is the speed of the aircraft, m is the mass of the aircraft, θ is the ballistic inclination angle, ψ V is the ballistic deflection angle, G x2 , G y2 , G z2The projections of gravity on the x, y, and z axes in the ballistic coordinate system are N x2 , N y2 , N z2 ; the projections of the resultant force of all external forces other than gravity on the x, y, and z axes in the ballistic coordinate system are;

[0036] S32: The projection equation of gravity in the ballistic coordinate system is:

[0037]

[0038] S33: Divide both ends of the formula of the projection equation by mg, and substitute the projection equation into the dynamic equation to obtain the overload equation expressed in terms of motion parameters:

[0039]

[0040] where n x2 , n y2 , n z2 are the projections of the overload on the x, y, and z axes in the ballistic coordinate system;

[0041] S34: Use the overload equation to establish a relationship model between the projection of the overload in the ballistic coordinate system and the tangential acceleration of the aircraft:

[0042]

[0043] S35: When the aircraft moves in the horizontal plane x2Oz2, the radius of curvature ρ of a point on the flight trajectory is the reciprocal of the derivative of the flight trajectory deflection angle ψ V with respect to the arc length s, and the radius of curvature of the semicircle flight trajectory is obtained as the radius equation r of the entire circle flight trajectory:

[0044]

[0045] S36: Substitute the radius equation r into the third equation in the relationship model to obtain the lateral overload command during the aircraft's turn. The lateral overload command includes the turn radius r' of the aircraft and the overload n z2 ' in the z-axis direction in the ballistic coordinate system:

[0046]

[0047]

[0048] S37: During the turn, the aircraft is in the cruise phase, the ballistic inclination angle is 0, so cosθ = 1, and the turn radius in the actual flight situation is relatively small, so a positive gain K r for compensating the turn radius is given, and K r is less than 1, then the lateral overload control amount is obtained:

[0049]

[0050] S38: Input the turning radius r' and overload n of the lateral overload command into the lateral overload control system, and the aircraft executes a turn according to the lateral overload command. z2 ' Input the turning radius r' and overload n of the lateral overload command into the lateral overload control system, and the aircraft executes a turn according to the lateral overload command.

[0051] Further, step S4 includes:

[0052] S41: Establish a judgment model for the speed of the aircraft during a turn:

[0053]

[0054] Wherein, V X and V Z are the x and z direction speeds in the launch coordinate system respectively, V Z0 is the threshold value of the z direction speed value in the launch coordinate system, and V X0 is the threshold value of the x direction speed in the launch coordinate system;

[0055] S42: When the aircraft is at a set distance from the main flight path during the turn, collect the V X and V Z at this time of the aircraft's turn, substitute them into the judgment model. If the current V X and V Z both satisfy the judgment model, it is determined that the turn is completed, and step S5 is executed to perform lateral position correction; if the speed of the aircraft's turn does not satisfy the judgment model, it is determined that the turn is not completed, and return to step S3 to continue executing the turn.

[0056] The beneficial effects of the present invention are as follows: The present invention first proposes that on the premise of a given desired turning radius of the aircraft, the overload required for turning is calculated in real time through the current speed of the aircraft, and the judgment conditions for early termination of the turn are set to complete the predetermined turn, so that the aircraft can directly fly back to the main flight path after completing the turn. The present invention calculates the required lateral overload during the turn in real time through the current speed of the aircraft based on the turning radius of the reference flight trajectory, and reasonably sets the turn end judgment point, so that the flight trajectories under different conditions are almost the same and can be smoothly connected to the main flight path. Brief Description of the Drawings

[0057] Figure 1 is a flowchart of the method for the aircraft to turn on a fixed trajectory in the horizontal plane.

[0058] Figure 2 is an ideal trajectory diagram of the aircraft.

[0059] Figure 3 is the command distribution diagram of BTT control.

[0060] Figure 4It is a schematic diagram of the lateral overload control system for an aircraft.

[0061] Figure 5 It is the horizontal plane projection curve of the aircraft flight in the prior art.

[0062] Figure 6 It is the Z-direction displacement curve of the aircraft flight in the prior art.

[0063] Figure 7 It is the lateral overload curve of the aircraft flight in the prior art.

[0064] Figure 8 It is the normal overload curve of the aircraft flight in the prior art.

[0065] Figure 9 It is the horizontal plane projection curve of the aircraft flight after using the method of the present invention.

[0066] Figure 10 It is the Z-direction displacement curve of the aircraft flight after using the method of the present invention.

[0067] Figure 11 It is the lateral overload curve of the aircraft flight after using the method of the present invention.

[0068] Figure 12 It is the normal overload curve of the aircraft flight after using the method of the present invention. Detailed implementation manners

[0069] The following describes the detailed implementation manners of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the detailed implementation manners. For those ordinary skilled in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions created using the concept of the present invention are within the scope of protection.

[0070] As Figure 1 shown, the method for the aircraft to turn along a fixed trajectory in the horizontal plane of this solution includes the following steps:

[0071] S1: As Figure 3 shown, according to the BTT control model of the aircraft under three channels, convert the control command in the launch coordinate system to the aircraft coordinate system to obtain the control command equation of the aircraft:

[0072]

[0073] where, nyc is the longitudinal overload required for the aircraft to track the altitude, nzc is the heading overload required for lateral position correction or lateral maneuver, ny c is the longitudinal overload command value input to the pitch control loop, nzc is the lateral overload command value for the input yaw control loop, γ c is the roll angle command value for the input roll channel.

[0074] S2: Design the aircraft lateral position control system, establish the closed-loop transfer functions of the five loops of the lateral position control system, and calculate the control gains.

[0075] Further, step S2 includes:

[0076] S21: Use the pole placement method to design the control gains K z , K v , K n , K β , K ω ;

[0077] S22: Establish the closed-loop transfer function model ω y _close(s) and the closed-loop transfer function model β_close(s) of the sideslip angle loop:

[0078]

[0079]

[0080] where, b1 is the dynamic coefficient of the heading damping moment, b2 is the dynamic coefficient of the heading static stability moment, b3 is the dynamic coefficient of the heading control moment, b4 is the dynamic coefficient of the lateral force, and b5 is the dynamic coefficient of the rudder side force;

[0081] S23: Establish the characteristic equation of the pole placement method:

[0082]

[0083] where, ξ and ω n are the damping ratio and frequency corresponding to the ideal poles respectively;

[0084] S24: Make the characteristic equation equal to the corresponding system of the closed-loop transfer function model β_close(s) of the sideslip angle loop, and neglect the small quantities b1 and b4 in the dynamic coefficients to obtain the feedback control gains K ω and K β ;

[0085]

[0086] S25: Calculate the gain K n :

[0087]

[0088] where t is the rise time of the response of the lateral overload control system; the gains K v and K z are directly assigned according to the control effect of the lateral position control system.

[0089] S3: According to the control command of the aircraft, describe the dynamic equation of the aircraft's center-of-mass motion in the aircraft coordinate system Ox2y2z2, calculate the lateral overload command during the aircraft's turning using the dynamic equation, input the lateral overload command into the aircraft's lateral overload control system, and the aircraft executes the turn according to the lateral overload command and the control gain;

[0090] Step S3 includes:

[0091] S31: Describe the dynamic equation of the aircraft's center-of-mass motion in the aircraft coordinate system Ox2y2z2:

[0092]

[0093] where V is the speed of the aircraft, m is the mass of the aircraft, θ is the ballistic inclination angle, ψ V is the ballistic deflection angle, G x2 and G y2 and G z2 are the projections of gravity on the x, y, and z axes in the ballistic coordinate system, and N x2 and N y2 and N z2 are the projections of the resultant force of all external forces except gravity on the x, y, and z axes in the ballistic coordinate system;

[0094] S32: The projection equation of gravity in the aircraft trajectory coordinate system is:

[0095]

[0096] S33: Divide both sides of the formula of the projection equation by mg and substitute the projection equation into the dynamic equation to obtain the overload equation expressed in terms of motion parameters:

[0097]

[0098] where n x2 and n y2 and n z2 are the projections of the overload on the x, y, and z axes in the ballistic coordinate system;

[0099] It can be seen from this that the projection of the overload vector on the flight trajectory coordinate system characterizes the ability of the aircraft to change the magnitude and direction of its flight speed, and can also qualitatively represent the tangential acceleration at each point on the flight trajectory and the shape of the flight trajectory.

[0100] S34: Establish a relationship model between the projection of overload in the flight trajectory coordinate system of the aircraft and the tangential acceleration of the aircraft using the overload equation:

[0101]

[0102] S35: When the aircraft moves in the horizontal plane x2Oz2, the radius of curvature ρ of a certain point on the flight trajectory is the reciprocal of the derivative of the deflection angle ψ of the flight trajectory at that point with respect to the arc length s. The radius of curvature of the semicircle flight trajectory is obtained as the radius equation r of the entire circular flight trajectory: V Taking the reciprocal of the derivative with respect to the arc length s, the radius of curvature of the semicircle flight trajectory is obtained as the radius equation r of the entire circular flight trajectory:

[0103]

[0104] S36: Substitute the radius equation r into the third equation in the relationship model to obtain the lateral overload command during the aircraft's turn. The lateral overload command includes the turning radius r' of the aircraft and the overload n in the z-axis direction in the aircraft's trajectory coordinate system: z2 ':

[0105]

[0106]

[0107] According to the BTT control principle, since the altitude of the aircraft is no longer controlled during a fixed-trajectory turn, but the altitude is maintained by the component of the lift generated by its tilted maximum lift surface in the direction of gravity. When the aircraft makes a turning maneuver, there is a deviation between this component and the ideal value, resulting in a phenomenon of altitude drop. Therefore, during actual flight, the aircraft does not turn in the horizontal plane. When using the lateral overload equation to calculate the lateral overload for turning, the projected radius of its actual flight trajectory on the horizontal plane is smaller than the expected value.

[0108] S37: During the turn, the aircraft is in the cruise phase, the ballistic inclination angle is 0, so cosθ = 1, and the turning radius in the actual flight situation is relatively small. Then, a positive gain K for compensating the turning radius is given r , and K r is less than 1. Then, the lateral overload control quantity is obtained:

[0109]

[0110] S38: Input the turning radius r' and the overload quantity n z2 ' of the lateral overload command into the lateral overload control system, and the aircraft executes the turn according to the lateral overload command.

[0111] S4: Establish a judgment model for the speed of the aircraft during a turn, and use the judgment model to determine whether the turn of the aircraft is completed;

[0112] S41: Establish a judgment model for the speed when the aircraft turns:

[0113]

[0114] Among them, V X and V Z are the x and z direction velocities in the launch coordinate system respectively, V Z0 is the threshold value of the z direction velocity in the launch coordinate system, and V X0 is the threshold value of the x direction velocity in the launch coordinate system;

[0115] S42: When the aircraft is at a set distance from the main flight path during the turning process, collect the V X and V Z at this time of the aircraft turning, substitute them into the judgment model. If the V X and V Z at this time both satisfy the judgment model, it is determined that the turning is completed, and step S5 is executed to perform lateral position correction; if the speed of the aircraft turning does not satisfy the judgment model, it is determined that the turning is not completed, and return to step S3 to continue the turning.

[0116] S5: Extract the lateral position command after the aircraft turning is completed according to the designed flight trajectory, input the lateral position command into the lateral position control system, and correct the position of the aircraft.

[0117] To ensure that the turning end position of the aircraft is basically unified, avoid the situation that the turning end positions are widely scattered under different interference conditions, and be conducive to subsequent lateral position correction, set the conditions for judging the end of turning in advance, so that the aircraft judges the end of turning and starts to correct when it is still a certain distance from the main flight path. Considering generality and simplicity, use the x direction velocity V X and the z direction velocity V Z in the launch coordinate system to judge whether to end the turning, that is, when both satisfy the judgment model, it is judged that the turning is ended.

[0118] The magnitude and direction of the velocity V X and V Z reflect the position of the aircraft from the side. Taking Figure 2 as an example, during the turning, if the velocity V X is positive, it means that the aircraft has not turned a quarter of a circle yet, and if it is negative, it means that the aircraft has already turned a quarter of a circle. |V Z |≤V Z0 indicates the proximity of the aircraft to the main flight path.

[0119] The effectiveness of the technology of the present invention is verified by comparing the simulation examples of three trajectories below. The first is the reference missile, that is, the trajectory under ideal conditions, the second is the trajectory with the largest turning radius in the Monte Carlo deflection, and the third is the trajectory with the smallest turning radius in the Monte Carlo deflection.

[0120] In the simulation, it is set that the lateral position deviation correction starts 2 seconds after the turn is completed, r = 5000m, K r = 0.985, V Z0 = 20m / s, V X0 = 0m / s. The simulation effect before using the method of the present invention is as Figures 5 - 12 shown, Figures 5 - 8 which is the simulation effect of the prior art aircraft in flight, Figures 9 - 12 and which is the simulation effect after using the method of the present invention.

Claims

1. A method for the horizontal plane fixed-trajectory turning of an aircraft, characterized in that, It includes the following steps: S1: According to the BTT control model of the aircraft in the three-channel, convert the control command in the launch coordinate system to the ballistic coordinate system to obtain the control command equation of the aircraft; S2: Design the lateral position control system of the aircraft, establish the closed-loop transfer function of the five loops of the lateral position control system, and calculate the control gain; S3: According to the control command of the aircraft, in the ballistic coordinate system describe the dynamic equation of the aircraft's center-of-mass motion, calculate the lateral overload command during the aircraft's turning using the dynamic equation, input the lateral overload command into the aircraft's lateral overload control system, and the aircraft executes the turn according to the lateral overload command and the control gain; S4: Establish a judgment model for the speed of the aircraft during turning, and use the judgment model to judge whether the turning of the aircraft is completed: If the speed of the aircraft turning satisfies the judgment model, it is determined that the turning is completed, and step S5 is executed; If the speed of the aircraft turning does not satisfy the judgment model, it is determined that the turning is not completed, return to step S3, and continue to execute the turning; S5: Extract the lateral position command after the aircraft turning is completed according to the designed flight trajectory, input the lateral position command into the lateral position control system, and correct the position of the aircraft; The step S2 includes: S21: Design the control gain of the lateral position control system using the pole placement method K z 、K v 、K n 、K β 、K ω ; S22: Establish the closed-loop transfer function model of the damping loop of the lateral position control system ω y _ close ( s ) and the closed-loop transfer function model of the sideslip angle loop β _ close ( s ): Among them, is the dynamic coefficient of the course damping moment, is the dynamic coefficient of the course static stability moment, is the dynamic coefficient of the course control moment, is the dynamic coefficient of the lateral force, is the dynamic coefficient of the rudder side force; S23: Establish the characteristic equation of the pole placement method: Among them, and are the damping ratio and frequency corresponding to the ideal poles, respectively; S24: Make the characteristic equation and the closed-loop transfer function model of the sideslip angle loop β _ close () s correspond to the system to be equal, and ignore the small quantities in the dynamic coefficients 、 , and obtain the feedback control gains and ; S25: Calculate the gain K n : Among them, is the rise time of the lateral overload control system response; the gain , is directly assigned according to the control effect of the lateral position control system.

2. The method for the aircraft to turn along a fixed trajectory in the horizontal plane according to claim 1, characterized in that, The control command of the aircraft in step S1 is: wherein, is the longitudinal overload required for the aircraft to track altitude, is the heading overload required for lateral position correction or lateral maneuver, is the longitudinal overload command value input to the pitch control loop, is the lateral overload command value input to the yaw control loop, is the roll angle command value input to the roll channel.

3. The method for the aircraft to turn along a fixed trajectory in the horizontal plane according to claim 1, characterized in that The step S3 includes: S31: Describe the dynamic equation of the centroid motion of the aircraft in the ballistic coordinate system as follows: Wherein, is the speed of the aircraft, is the mass of the aircraft, is the ballistic inclination angle, is the ballistic deflection angle, is the projection of gravity on the three axes in the ballistic coordinate system ; and is the projection of the resultant force of all external forces other than gravity on the three axes in the ballistic coordinate system . S32: The projection equation of gravity in the ballistic coordinate system is: S33: Divide both ends of the formula of the projection equation by , and substitute the projection equation into the dynamic equation to obtain the overload equation expressed by motion parameters: Among them, are the projections of the overload on the three axes in the ballistic coordinate system; ​ S34: Use the overload equation to establish the relationship model between the projection of the overload in the ballistic coordinate system and the tangential acceleration of the aircraft: S35: When the aircraft moves in the horizontal plane , the radius of curvature of a point on the flight trajectory is the reciprocal of the derivative of the flight trajectory deflection angle with respect to the arc length . The radius of curvature of the semi-circular flight trajectory is obtained as the radius equation of the flight trajectory : S36: Substitute the radius equation into the third equation in the relational model to obtain the lateral overload command during the aircraft's turn. The lateral overload command includes the turning radius of the aircraft r' and the overload z in the n z2 ' direction of the ballistic coordinate system S37: During the turn, the aircraft is in the cruise phase and the ballistic inclination angle is 0. Then , and the turning radius in the actual flight condition is small, so a positive gain for compensating the turning radius is given , and is less than 1, and the lateral overload control amount is obtained: S38: Turn radius of the lateral overload command r' and overload amount n z2 are input into the lateral overload control system, and the aircraft executes a turn according to the lateral overload command.

4. The method for the aircraft to turn along a fixed trajectory in the horizontal plane according to claim 1, characterized in that The step S4 includes: S41: Establish a judgment model for the speed of the aircraft during turning: Among them, and are respectively the and longitudinal velocities in the launch coordinate system, is the threshold of the longitudinal velocity value in the launch coordinate system, is the threshold of the lateral velocity in the launch coordinate system; S42: When the aircraft is still at a set distance from the main airway during the turning process, collect the and at this time and substitute them into the judgment model. If the and at this time both meet the judgment model, it is determined that the turning is completed, and step S5 is executed to perform lateral position correction; if the turning speed of the aircraft does not meet the judgment model, it is determined that the turning is not completed, and the process returns to step S3 to continue executing the turning.

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