Flight control method for tilting transition stage of tilting wing aircraft

Abstract

The invention discloses a flight control method for a tilt transition stage of a tilt-rotor aircraft. The flight control method comprises the following steps: constructing a tilt corridor of the tilt-rotor aircraft; acquiring the vertical control quantity of the aircraft in the tilting transition stage in real time; the tilt angle corresponding to the upper boundary of the tilt corridor serves as a tilt angle feed-forward instruction of the aircraft in the tilt transition stage; a tilt angle beta is obtained; taking the flight speed of the upper boundary of the tilting corridor corresponding to the tilting angle beta as a flight speed instruction of the aircraft in the tilting transition stage; correspondingly obtaining a final accelerator instruction of the tilting rotor; and performing flight control on the aircraft in the tilting transition stage. The tilt angle can be determined based on the tilt corridor so as to correspondingly obtain the final accelerator instruction of the tilt rotor, meanwhile, the flight height is kept unchanged at the moment of the tilt transition stage, and the flight speed is controlled within the preset range, so that the height and speed control precision of the aircraft is improved, and the control precision of the aircraft is improved. And therefore, the controllability and the safety in the tilting flight process are improved.

Description

Technical Field

[0001] The invention relates to the technical field of tilt-rotor aircraft, and in particular to a flight control method for a tilt-rotor aircraft in a tilt transition phase. Background Art

[0002] During the flight control process of a tiltrotor aircraft, how to achieve stable control of the flight speed and altitude during the transition stage from the multi-rotor mode to the fixed-wing mode ("multi-rotor mode" means the tiltrotor is tilted to a state where the rotor blades are facing upward, "fixed-wing mode" means the tiltrotor is tilted to a state where the rotor blades are facing forward, and "transition stage" means the process in which the tiltrotor, driven by the tilt mechanism, causes the rotor blades to rotate from an upward state to a forward state, or from a forward state to an upward state) is a technical problem that needs to be urgently solved in this field.

[0003] In the prior art, during the above-mentioned transition phase, a control scheme of "fixed altitude but not speed control" is usually adopted (i.e., the flight altitude is kept unchanged, but the speed is open-loop controlled). When the transition time is too long, the transition is stopped. This scheme will cause the aircraft's route tracking capability to deteriorate. Alternatively, during the transition phase, the flight altitude and flight speed are controlled separately through different control weights, but this control method cannot take into account the control accuracy of both. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a flight control method for a tilt-rotor aircraft in a tilt transition phase, which can determine the tilt angle based on the tilt corridor to obtain the final throttle command of the tilt rotor, and at the same time keep the flight altitude unchanged at all times in the tilt transition phase, and control the flight speed within a predetermined range, so as to improve the altitude and speed control accuracy of the aircraft, thereby improving the controllability and safety of the tilt flight process.

[0005] The present invention provides the following technical solutions:

[0006] A flight control method for a tilt-wing aircraft during a tilt transition phase is provided, which comprises the following steps:

[0007] Constructing a tilt corridor for tilt-wing aircraft;

[0008] According to the vertical acceleration A of the aircraft as a whole z Obtain the vertical control value T of the aircraft in the tilt transition phase in real time;

[0009] The tilt angle corresponding to the upper boundary of the tilt corridor is used as a tilt angle feedforward instruction of the aircraft in the tilt transition phase;

[0010] Obtain the tilt angle β of rotors No. 5 and No. 6 according to the tilt angle feedforward command and the tilt angle feedback command;

[0011] Using the upper boundary flight speed of the tilt corridor corresponding to the tilt angle β as the flight speed instruction of the aircraft in the tilt transition phase;

[0012] The feedforward throttle command and the feedback throttle command are added together to obtain the final throttle commands for rotors No. 5 and No. 6;

[0013] During the tilt transition phase, the flight of the aircraft is controlled according to one or more of the final throttle command adjustment of rotors No. 5 and No. 6, the vertical control amount T, and the flight speed command.

[0014] Preferably, according to T = A z / A z_TOTAL Calculate the vertical control amount T, where A z_TOTAL is the maximum vertical acceleration of the entire aircraft.

[0015] Preferably, the tilt angle β=β Forward +β Feedback , where β Forward , β Feedback are respectively the tilt angle feedforward command and the tilt angle feedback command, and β Feedback =arctan(A z / A x ), A x is the overall forward acceleration of the aircraft.

[0016] Preferably, the feedforward throttle commands for the six rotors are obtained based on formulas (1)-(3):

[0017]

[0018] Among them, T, L, M, and N are the virtual control quantities of the thrust channel, the virtual control quantity of the roll channel, the virtual control quantity of the pitch channel, and the virtual control quantity of the yaw channel of the same rotor, respectively, and they are all known values; thrust_cmd1~thrust_cmd6 correspond to the feedforward throttle commands of rotors No. 1 to No. 6, respectively; a1~a4 correspond to the roll arm lengths of rotors No. 1 to No. 4, respectively; a5~a8 correspond to the pitch arm lengths of rotors No. 1 to No. 4, respectively; a9 and a10 correspond to the lengths from the thrust center of rotor No. 5 and the thrust center of rotor No. 6 to the center of mass of the fuselage, respectively; β is the tilt angle of rotors No. 5 and No. 6; T_curise is the normalized trim throttle of rotors No. 5 and No. 6; B 1 is the control effectiveness matrix; B is the control effectiveness matrix B 1 The normalized modulus of ; the superscript T indicates the matrix transpose.

[0019] Preferably, feedback throttle command = A x / A x_total , and Ax-total is the maximum forward acceleration of the aircraft as a whole, A x It is the overall forward acceleration of the aircraft obtained in real time.

[0020] Preferably, during the tilt transition stage, the flight of the aircraft is controlled according to one or more of the final throttle command adjustment of rotors No. 5 and No. 6, the vertical control amount T, and the flight speed command, including: during the tilt transition stage, the rotation speed of all rotors is controlled according to the vertical control amount T so that the flight altitude of the aircraft remains unchanged during the tilt transition stage.

[0021] Preferably, during the tilt transition stage, the flight of the aircraft is controlled according to one or more of the final throttle command adjustment of rotors No. 5 and No. 6, the vertical control amount T, and the flight speed command, including: during the tilt transition stage, the flight speed of the aircraft is adjusted according to the flight speed command, specifically, when the flight speed command is less than or equal to the flight speed threshold, the aircraft is controlled to fly at a preset ground speed, and when the flight speed command is greater than the flight speed threshold, the aircraft is controlled to fly at a preset airspeed.

[0022] Preferably, the flight speed threshold is the effective minimum value of the airspeed meter.

[0023] Preferably, during the tilt transition phase, the flight of the aircraft is controlled according to one or more of the final throttle command adjustment of rotors No. 5 and No. 6, the vertical control amount T, and the flight speed command, including: during the tilt transition phase, the throttle output of rotors No. 5 and No. 6 is adjusted according to the final throttle command of rotors No. 5 and No. 6.

[0024] Compared with the prior art, the present invention determines a tilt angle feedforward instruction based on a tilt corridor, obtains a tilt angle based on the tilt angle feedforward instruction and the tilt angle feedback instruction, and then adds the feedforward throttle instruction and the feedback throttle instruction to obtain the final throttle instruction for rotors No. 5 and No. 6. Meanwhile, the flight altitude is kept unchanged at all times during the tilt transition stage, and the flight speed is controlled within a predetermined range to ensure smooth flight of the aircraft. Thus, through the control method of "offline decoupling and real-time feedback", "fixed-altitude level flight" and tilt angle control are achieved during the tilt transition stage, thereby improving the altitude and speed control accuracy of the aircraft, thereby improving the controllability and safety during the tilt flight process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the tilt-rotor aircraft in the present invention;

[0026] Figure 2 A flowchart of the steps of the flight control method of the tilt-wing aircraft in the tilt transition phase of the present invention;

[0027] Figure 3It is the tilt corridor curve of the tilt-rotor aircraft in the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1:

[0030] like Figure 1 As shown, the tilt-rotor aircraft in this embodiment includes a fuselage 100, two main wings 101, 102 connected to the fuselage 100, and six rotors No. 1 to No. 6, among which rotors No. 5 and No. 6 are variable pitch rotors, which are respectively installed on one main wing, and can be tilted around the axis of the main wing under the drive of the tilt mechanism, so that rotors No. 5 and No. 6 can switch between multi-rotor mode and fixed-wing mode, and can provide a main thrust that exceeds the weight of the aircraft; rotors No. 1, No. 2, No. 3, and No. 4 are all non-tiltable fixed-pitch rotors, whose blades are always facing upward, and the four rotors all provide partial thrust as an auxiliary lift power system for providing torque for aircraft attitude control and auxiliary lift for vertical movement, and rotors No. 1 and No. 2 are arranged at the front of the fuselage, and rotors No. 3 and No. 4 are arranged at the tail of the fuselage.

[0031] On this basis, this embodiment provides a flight control method for a tilt-wing aircraft during a tilt transition phase, such as Figure 2 As shown, it includes the following steps:

[0032] S1. construct a tilt corridor for the tilt-rotating wing aircraft;

[0033] For example, in this embodiment, one or more of the following data can be obtained, such as the pull coefficient of different incoming flows, the pull change of the variable-pitch rotor under different incoming flow speeds, the pull change of the fixed-pitch rotor under different incoming flow speeds, the torque coefficient of the force on each part under different tilt angles, and the interference effect of the variable-pitch rotor on the fuselage and rudder effect at different tilt angles, the interference effect of rotors No. 1, No. 2, No. 5, and No. 6 on rotors No. 3 and No. 4 during the tilting process and the pull loss of rotors No. 3 and No. 4, the force and torque coefficients under different tilt angles-angles of attack-sideslips, and the rudder effect coefficient, and then flight modeling can be performed based on the above data to obtain the following data: Figure 3 The tilt corridor curve shown has a horizontal coordinate of flight speed and a vertical coordinate of tilt angle;

[0034] S2, according to the vertical acceleration A of the aircraft as a wholez Obtain the vertical control value T of the aircraft in the tilt transition phase in real time;

[0035] Specifically, in this embodiment, the vertical acceleration A of the entire aircraft is z It can be directly obtained in real time based on the altitude controller carried by the aircraft, and the altitude controller realizes the flight altitude control of the aircraft based on proportional-integral-differential control, active disturbance rejection control or nonlinear incremental control; further, in this embodiment, according to T=A z / A z_TOTAL Calculate the vertical control amount T, where A z_TOTAL is the maximum vertical acceleration of the entire aircraft, which can be calculated in ground testing using the pull of each rotor and the overall mass of the aircraft;

[0036] S3, the tilt angle corresponding to the upper boundary of the tilt corridor (such as Figure 3 The tilt angle corresponding to point A in the middle is used as the tilt angle feedforward instruction β of the aircraft in the tilt transition stage. Forward ;

[0037] S4, according to the tilt angle feedforward instruction β Forward And the tilt angle feedback command β Feedback Obtain the tilt angle β of rotors 5 and 6, where β = β Forward +β Feedback , and β Feedback =arctan(A z / A x ), where A x The forward acceleration of the entire aircraft is obtained in real time, which can be obtained through the output of the speed controller. At the same time, in this embodiment, the tilt angles β of the No. 5 and No. 6 rotors can be regarded as the same at any time;

[0038] S5. Obtain the feedforward throttle commands for the six rotors based on the least squares method and formulas (1)-(3):

[0039]

[0040] Among them, T, L, M, and N are the virtual control quantities of the thrust channel, roll channel, pitch channel, and yaw channel of the same rotor, respectively, and they are all known values; thrust_cmd1~thrust_cmd6 correspond to the feedforward throttle commands of rotors 1 to 6, respectively, and their value ranges are all [0,1]; a1~a4 correspond to the roll arm lengths of rotors 1 to 4, respectively; a5~a8 correspond to the pitch arm lengths of rotors 1 to 4, respectively; a9 and a10 correspond to the thrust center of rotor 5, rotor 6, respectively. The length from the thrust center of rotor No. 5 to the center of mass of the fuselage; β is the tilt angle of rotor No. 5 and No. 6. When rotor No. 5 and No. 6 are both in "multi-rotor mode" (i.e., the blades of rotor No. 5 and No. 6 are both facing upward), β = 90°; when rotor No. 5 and No. 6 are both in "fixed-wing mode" (i.e., the blades of rotor No. 5 and No. 6 are both facing the front of the fuselage), β = 0°; T_curise is the normalized trim throttle of rotor No. 5 and No. 6, and the normalized trim throttle of rotor No. 5 and No. 6 is the same, which can be calculated in advance; B 1 is the control effectiveness matrix; B is the control effectiveness matrix B 1 The unit modulus value of ; the superscript T indicates the matrix transpose;

[0041] S6, the upper boundary flight speed of the tilt corridor corresponding to the tilt angle β (such as Figure 3 The flight speed corresponding to point B in the figure is used as the flight speed instruction of the aircraft in the tilt transition phase; Figure 3 As shown in the middle tilt corridor, when the tilt angle β changes, the corresponding upper boundary flight speed will change accordingly, so that each tilt angle β has a corresponding flight speed instruction;

[0042] and, adding the feedforward throttle command and the feedback throttle command to obtain the final throttle command for rotors No. 5 and No. 6;

[0043] Among them, the final throttle command of rotor 5 is thrust_cmd final5 , and thrust_cmd final5 =thrust_cmd5+(A x / A x_total ); The final throttle command for rotor 6 is thrust_cmd final6 , and thrust_cmd final6 =thrust_cmd6+(A x / A x_total ); The feedback throttle commands of rotors 5 and 6 are the same, and the feedback throttle command = A x / A x_total , A x-totalis the maximum forward acceleration of the aircraft as a whole, which can be predetermined by ground testing;

[0044] S7. During the tilt transition phase, the rotation speeds of all rotors are controlled according to the vertical control amount T, so that the flight altitude of the aircraft during the tilt transition phase remains unchanged;

[0045] And / or, in the tilt transition stage, the flight speed of the aircraft is adjusted according to the flight speed instruction. Specifically, when the flight speed instruction is less than or equal to the flight speed threshold, the aircraft is controlled to fly at a preset ground speed, and when the flight speed instruction is greater than the flight speed threshold, the aircraft is controlled to fly at a preset airspeed, wherein the flight speed threshold may be an effective minimum value of an airspeed meter; thereby, the flight speed of the aircraft in the tilt transition stage can be controlled within a predetermined range so that it does not fluctuate too much;

[0046] And / or, during the tilt transition phase, the throttle outputs of rotors No. 5 and No. 6 are adjusted according to the final throttle commands of rotors No. 5 and No. 6.

[0047] Therefore, this embodiment first determines the tilt corridor in an offline state, further determines the tilt angle feedforward instruction based on the tilt corridor, and obtains the tilt angle based on the tilt angle feedforward instruction and the tilt angle feedback instruction, and then adds the feedforward throttle instruction and the feedback throttle instruction to obtain the final throttle instruction of rotors No. 5 and No. 6 accordingly. At the same time, the flight altitude is kept unchanged at all times during the tilt transition stage, and the flight speed is controlled within a predetermined range to make the aircraft fly smoothly. Therefore, through the control method of "offline decoupling and real-time feedback", "fixed altitude level flight" and tilt angle control are realized in the tilt transition stage, the altitude and speed control accuracy of the aircraft are improved, and then the controllability and safety of the tilt flight process are improved.

[0048] It should be noted that the technical features in the above two embodiments can be combined arbitrarily, and the combined technical solutions all belong to the protection scope of the present application. And in this article, terms such as "including", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0049] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A flight control method for a tilt-rotor aircraft in a tilt transition phase, wherein the tilt-rotor aircraft comprises a fuselage, two main wings connected to the fuselage, and six rotors No. 1 to No. 6, wherein: Rotors No. 5 and No. 6 are installed on a main wing respectively, and can be tilted around the main wing axis under the drive of the tilt mechanism; rotors No. 1, No. 2, No. 3, and No. 4 are non-tiltable rotors, and their blades are always facing upward. It is characterized in that the flight control method includes the following steps: Constructing a tilt corridor for tilt-wing aircraft; According to the vertical acceleration A of the aircraft as a whole z Obtain the vertical control value T of the aircraft in the tilt transition phase in real time; The tilt angle corresponding to the upper boundary of the tilt corridor is used as a tilt angle feedforward instruction of the aircraft in the tilt transition phase; Obtain the tilt angle β of rotors No. 5 and No. 6 according to the tilt angle feedforward command and the tilt angle feedback command; Using the upper boundary flight speed of the tilt corridor corresponding to the tilt angle β as the flight speed instruction of the aircraft in the tilt transition phase; The feedforward throttle command and the feedback throttle command are added together to obtain the final throttle commands for rotors No. 5 and No. 6; During the tilt transition phase, the flight of the aircraft is controlled according to one or more of the final throttle command adjustment of rotors No. 5 and No. 6, the vertical control amount T, and the flight speed command.

2. The flight control method according to claim 1, characterized in that: According to T=A z / A z_TOTAL Calculate the vertical control amount T, where A z_TOTAL is the maximum vertical acceleration of the entire aircraft.

3. The flight control method according to claim 1, characterized in that: Tilt angle β = β Forward +β Feedback , where β Forward , β Feedback are respectively the tilt angle feedforward command and the tilt angle feedback command, and β Feedback =arctan(A z / A x ), A x is the overall forward acceleration of the aircraft.

4. The flight control method according to claim 1, characterized in that: Based on formulas (1)-(3), the feedforward throttle commands for the six rotors are obtained: Among them, T, L, M, and N are the virtual control quantities of the thrust channel, the virtual control quantity of the roll channel, the virtual control quantity of the pitch channel, and the virtual control quantity of the yaw channel of the same rotor, respectively, and they are all known values; thrust_cmd1~thrust_cmd6 correspond to the feedforward throttle commands of rotors No. 1 to No. 6, respectively; a1~a4 correspond to the roll arm lengths of rotors No. 1 to No. 4, respectively; a5~a8 correspond to the pitch arm lengths of rotors No. 1 to No. 4, respectively; a9 and a10 correspond to the lengths from the thrust center of rotor No. 5 and the thrust center of rotor No. 6 to the center of mass of the fuselage, respectively; β is the tilt angle of rotors No. 5 and No. 6; T_curise is the normalized trim throttle of rotors No. 5 and No. 6; B 1 is the control effectiveness matrix; B is the control effectiveness matrix B 1 The normalized modulus of ; the superscript T indicates the matrix transpose.

5. The flight control method according to claim 1, characterized in that: Feedback throttle command = A x / A x_totla , and A x-total is the maximum forward acceleration of the aircraft as a whole, A x It is the overall forward acceleration of the aircraft obtained in real time.

6. The flight control method according to claim 1, characterized in that: During the tilt transition phase, the flight of the aircraft is controlled according to one or more of the final throttle command adjustment of rotors No. 5 and No. 6, the vertical control amount T, and the flight speed command, including: during the tilt transition phase, the rotation speed of all rotors is controlled according to the vertical control amount T so that the flight altitude of the aircraft remains unchanged during the tilt transition phase.

7. The flight control method according to claim 1, characterized in that: During the tilt transition phase, the flight of the aircraft is controlled according to one or more of the final throttle command adjustment of rotors No. 5 and No. 6, the vertical control amount T, and the flight speed command, including: during the tilt transition phase, the flight speed of the aircraft is adjusted according to the flight speed command. Specifically, when the flight speed command is less than or equal to the flight speed threshold, the aircraft is controlled to fly at a preset ground speed; when the flight speed command is greater than the flight speed threshold, the aircraft is controlled to fly at a preset airspeed.

8. The flight control method according to claim 1, characterized in that: The flight speed threshold is the effective minimum value of the airspeed meter.

9. The flight control method according to claim 1, characterized in that: During the tilt transition phase, the flight of the aircraft is controlled according to one or more of the final throttle command adjustment of rotors No. 5 and No. 6, the vertical control amount T, and the flight speed command, including: during the tilt transition phase, the throttle output of rotors No. 5 and No. 6 is adjusted according to the final throttle command of rotors No. 5 and No. 6.

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