Combined dynamic inspiration mode flight envelope design and trajectory optimization method

Abstract

The invention provides a combined dynamic inspiration mode flight envelope design and trajectory optimization method, and the optimization method comprises the following steps: obtaining a flight trajectory design input condition; analyzing the working envelope, flight overload and dynamic pressure flight path design constraints of the air suction power engine based on task requirements; resolving an upper attack angle section alpha up (t) meeting the constraint conditions to obtain an upper boundary of the flight envelope in the height-speed section; resolving a lower attack angle profile alpha down (t) meeting the constraint conditions to obtain a lower boundary of the flight envelope in the height-speed profile; and determining a flight trajectory in the upper and lower boundaries of the height-speed profile, namely, meeting the multi-constraint design condition of the trajectory of the air suction powered aircraft.

Description

Technical Field

[0001] The present invention belongs to the field of combined-power aircraft flight envelope and trajectory design, and in particular relates to a combined-power air-breathing mode flight envelope design and trajectory optimization method. Background Art

[0002] The performance of the combined power engine is severely coupled with the trajectory profile, and is very sensitive to flight altitude, Mach number, angle of attack, etc. The engine performance varies greatly under different conditions. When it exceeds the normal working range, the engine may experience abnormal phenomena such as overspeed and surge. When designing the trajectory of a combined power vehicle, in addition to considering the various constraints faced by traditional reentry vehicles, such as load, heat flow, dynamic pressure, hinge torque, etc., it is also necessary to consider the limitations and impact of engine performance on the flight trajectory. In order to give full play to the capabilities of the combined power engine under various constraints, it is necessary to optimize the flight envelope, mode switching point, and climb trajectory of the combined power vehicle. Summary of the invention

[0003] The purpose of the present invention is to propose a combined power air-breathing mode flight envelope design and trajectory optimization method, which is used to solve the trajectory design problems of the air-breathing combined power aircraft with many constraints in the ascent phase and high requirements on terminal window accuracy, and to realize the full trajectory design of the combined power engine.

[0004] The present invention provides a combined power air-breathing mode flight envelope design and trajectory optimization method, the optimization method comprising the following steps:

[0005] Obtain flight trajectory design input conditions;

[0006] Analyze the air-breathing engine operating envelope, flight overload, and dynamic pressure flight trajectory design constraints based on mission requirements;

[0007] Solve the attack angle profile α that satisfies the constraints up (t), obtain the upper boundary of the flight envelope in the altitude-speed profile;

[0008] Solve the downward attack angle profile α that satisfies the constraints down (t), obtain the lower boundary of the flight envelope in the altitude-speed profile;

[0009] The flight trajectory is determined within the upper and lower boundaries of the altitude-speed profile, that is, the multi-constraint design conditions of the trajectory of the air-breathing powered aircraft are met.

[0010] Furthermore, the upper boundary of the flight envelope in the altitude-speed profile is the maximum altitude that can be flown at each flight speed while satisfying the maximum angle of attack, maximum rate of change of angle of attack, minimum acceleration capability and engine operating envelope constraints.

[0011] Furthermore, the above solution satisfies the constraint condition of the angle of attack profile α up (t), obtain the upper boundary of the flight envelope in the altitude-speed profile, including the following steps:

[0012] (1) Obtaining the initial value of the flight state based on the initial conditions of the flight mission;

[0013] (2) Calculate the corresponding angle of attack α based on the maximum altitude constraint allowed by the engine a ;

[0014] (3) Determine whether the minimum acceleration capacity constraint is met and obtain the angle of attack α b ;

[0015] (4) Determine whether the angle of attack change rate constraint is met and obtain the angle of attack α up ;

[0016] (5) Based on the initial conditions of step (1), the altitude-velocity envelope upper boundary of the flight trajectory can be obtained according to the above steps (2), (3), and (4). The aircraft motion equation is solved until the terminal constraint is satisfied.

[0017] Furthermore, the lower boundary of the flight envelope in the speed-altitude profile is the minimum altitude that can be flown while satisfying the maximum angle of attack, maximum rate of change of angle of attack, maximum dynamic pressure, maximum overload, maximum acceleration capability and engine operating range constraints.

[0018] Furthermore, the solution satisfies the constraint condition of the downward attack angle profile α down (t), obtain the lower boundary of the flight envelope in the altitude-speed profile, including the following steps:

[0019] (1) Obtaining the initial value of the flight state based on the initial conditions of the flight mission;

[0020] (2) Calculate the corresponding angle of attack α by combining the lower limit of the engine's allowed altitude and the maximum dynamic pressure limit c ;

[0021] (3) Determine α c Whether the maximum overload constraint is met, the angle of attack α is obtained down ;

[0022] (4) Determine whether the angle of attack change rate constraint is met and obtain the angle of attack α down ;

[0023] (5) Based on the initial conditions of step (1), the α at each moment can be obtained according to the above steps (2), (3), and (4). down (t), and the lower boundary of the flight trajectory height-velocity envelope can be obtained by solving the aircraft motion equation until the terminal constraint is satisfied.

[0024] The beneficial effects of the present invention are as follows:

[0025] The combined-power aircraft intake mode flight envelope design method proposed in the present invention can solve the angle of attack value that satisfies the constraints and makes the height maximum or minimum according to the constraints of the upper and lower boundaries, and then obtain the flight envelope of the maximum height and the minimum height. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations of the present invention. In the accompanying drawings:

[0027] Figure 1 is a flow chart of the combined power aircraft air-breathing mode flight envelope design and flight trajectory design according to an embodiment of the present invention;

[0028] Figure 2 is a flowchart of flight envelope upper boundary planning according to an embodiment of the present invention;

[0029] Figure 3 4 is a flowchart of flight envelope upper boundary planning according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] Example 1

[0032] A combined power-breathing mode flight envelope design and trajectory optimization method, the design process is as follows Figure 1 , the specific steps are as follows:

[0033] S101: Obtain flight trajectory design input conditions;

[0034] S103: Analyze the air-breathing engine operating envelope, flight overload, and dynamic pressure flight trajectory design constraints based on mission requirements;

[0035] S105: Calculate the attack angle profile α that satisfies the constraints up (t), get the upper boundary of the height-velocity profile;

[0036] S107: Calculate the downward attack angle profile α that satisfies the constraints down(t), get the lower boundary of the height-velocity profile;

[0037] S109: Determine the flight trajectory within the upper and lower boundaries of the altitude-speed profile, that is, satisfy the multi-constraint design conditions of the air-breathing powered aircraft trajectory.

[0038] 2. Flight envelope upper boundary design method

[0039] The upper boundary of the flight envelope in the speed-altitude profile is the maximum altitude that can be flown at each flight speed while satisfying the constraints of maximum angle of attack, maximum rate of change of angle of attack, minimum acceleration capability, engine operating envelope, etc. The flight envelope upper boundary planning flow chart is as follows: Figure 2 shown.

[0040] (1) Obtaining the initial value of the flight state based on the initial conditions of the flight mission;

[0041] (2) Calculate the corresponding angle of attack α based on the maximum altitude constraint allowed by the engine a ;

[0042] Combined with the engine boundary as the upper boundary of the speed-altitude profile, it can be converted into the known current speed V k , height H k , trajectory angle γ k And the speed-altitude profile, solve the angle of attack that satisfies the profile. The corresponding formula is:

[0043]

[0044] Where, T k 、m k , D(α a ) are respectively the thrust, mass and resistance at the current moment, is the rate of change of velocity constrained by the profile. Where, the drag coefficient is a function of the angle of attack and the Mach number.

[0045] (3) Determine α a Whether the minimum acceleration capacity constraint is met, the angle of attack α is obtained b ;

[0046] The minimum acceleration capability corresponds to the maximum allowable angle of attack α of the aircraft max In order to make the aircraft meet both the engine operating range constraint and the minimum acceleration capability constraint, the angle of attack α calculated by equation (1) should be k and the maximum allowable angle of attack of the aircraft α max The minimum value of the two is used as the input value of the angle of attack at the current moment.

[0047] α b =min{α a ,α max}

[0048] (4) Determine α b Whether the angle of attack change rate constraint is met, the angle of attack α is obtained up ;

[0049] According to the maximum angle of attack change rate constraint, the maximum angle of attack allowed at the current moment can be obtained:

[0050]

[0051] In the formula, α k-1 is the angle of attack value at the previous moment. When the constraint exceeds the limit, the minimum value of the angle of attack values ​​obtained by the above constraints and the maximum angle of attack change rate is selected as the angle of attack input value at the current moment.

[0052]

[0053] It is the angle of attack value at the current moment solved according to the maximum angle of attack change rate;

[0054] α up is the angle of attack value that satisfies all upper boundary constraints at the current moment.

[0055] (5) Based on the initial conditions of step (1), the α at each moment can be obtained according to the above steps (2), (3), and (4). up (t), and the upper boundary of the flight trajectory height-velocity envelope can be obtained by solving the aircraft motion equation until the terminal constraint is satisfied.

[0056] 3. Flight envelope lower boundary design method

[0057] The lower boundary of the flight envelope in the speed-altitude profile is to ensure that the aircraft flies at the minimum altitude possible while meeting the maximum angle of attack, maximum rate of change of angle of attack, maximum dynamic pressure, maximum overload, maximum acceleration capability, and engine operating range constraints, so as to fully utilize the advantages of the combined engine. The flight envelope upper boundary planning flow chart is as follows: Figure 3 shown.

[0058] (1) Obtaining the initial value of the flight state based on the initial conditions of the flight mission;

[0059] (2) Calculate the corresponding angle of attack α by combining the lower limit of the engine's allowed altitude and the maximum dynamic pressure limit c ;

[0060] By using equation (1), we can solve the angle of attack value that satisfies the speed-altitude profile composed of the maximum dynamic pressure and the minimum altitude in the engine operating envelope. The lower boundary of the flight corridor is also limited by the acceleration capability. If the aircraft is to satisfy the constraints of dynamic pressure, the minimum operating altitude of the engine, and the acceleration capability, the corresponding angle of attack α calculated by equation (1) should be taken. k1 and minimum angle of attack αmi The maximum value among n is taken as the angle of attack input value α at the current moment c :

[0061] α c =max{α k ,α min}

[0062] (3) Determine α c Whether the maximum overload constraint is met, the angle of attack α is obtained d ;

[0063] The maximum overload allowed angle of attack α(n max ), if the overload exceeds the limit, the aircraft should fly along the maximum overload constraint; otherwise, according to α c Keep flying.

[0064]

[0065] (4) Determine α d Whether the angle of attack change rate constraint is met, the angle of attack α is obtained down ;

[0066] In the above calculation, the angle of attack α c Based on this, the angle of attack change rate constraint is considered. According to the minimum angle of attack change rate constraint, the minimum angle of attack allowed at the current moment can be calculated:

[0067]

[0068] In the formula, α k-1 is the angle of attack value at the previous moment.

[0069] When the constraint exceeds the limit, the minimum value of the angle of attack values ​​obtained according to the above constraints and the maximum angle of attack change rate constraint is selected as the angle of attack input value at the current moment.

[0070]

[0071] αd own is the angle of attack value that satisfies all lower boundary constraints at the current moment.

[0072] (5) Based on the initial conditions of step (1), the α at each moment can be obtained according to the above steps (2), (3), and (4). down (t), and the lower boundary of the flight trajectory height-velocity envelope can be obtained by solving the aircraft motion equation until the terminal constraint is satisfied.

[0073] Example 2

[0074] The flight envelope design of the combined-propulsion aircraft's air-breathing mode first requires obtaining the flight trajectory design input conditions, which generally include aircraft mass characteristics, combined-propulsion engine performance data and operating envelope, atmospheric parameters, mission dynamic pressure constraints, overload constraints, etc.

[0075] In the combined power flight air-breathing mode working stage, in addition to the altitude and speed constraints that must be met to ensure the normal operation of the combined power engine, multiple constraints such as dynamic pressure, overload, angle of attack, and rate of change of angle of attack must also be met to ensure the safety of the aircraft. Based on multiple constraints, the corresponding altitude, speed, and angle of attack constraints are analyzed in combination with the aircraft motion equations.

[0076] (1) Engine operating range and terminal window constraints:

[0077]

[0078] H Emin , H Emax They respectively represent the maximum and minimum operating altitudes in the engine operating envelope, and are both functions of the flight speed V.

[0079] (2) Dynamic pressure constraint:

[0080]

[0081] Here the dynamic pressure is the height H and velocity V, ρ0 represents the atmospheric density at sea level, constraining the lower boundary of the height;

[0082] (3) Normal overload constraint:

[0083]

[0084] here is the dynamic pressure, the normal force coefficient C y It is a function of the angle of attack α and the Mach number Ma, where m is the flight mass and g is the acceleration due to gravity.

[0085] Based on the flight trajectory design input and mission requirements, determine the initial flight state values, which generally include initial altitude, speed, position, mass, etc.

[0086] Based on the input conditions, follow the process Figure 2 The method completes the design of the upper boundary of the flight envelope in the speed-altitude profile. Combined with the maximum altitude constraint allowed by the engine, the corresponding angle of attack α is calculated. a , determine whether the angle of attack meets the minimum acceleration condition to obtain α b =min{α a ,α max}; judge α b Whether the angle of attack change rate constraint is met, get the angle of attack Based on the initial conditions, we get α at each moment. up (t), and the upper boundary of the flight trajectory height-velocity envelope can be obtained by solving the aircraft motion equation until the terminal constraint is satisfied.

[0087] Based on the input conditions, follow the process Figure 3 The method completes the design of the lower boundary of the flight envelope in the speed-altitude profile. The corresponding angle of attack α is calculated by combining the lower boundary of the engine's allowed altitude and the maximum dynamic pressure boundary. c , determine whether the angle of attack meets the minimum acceleration condition to obtain α b =min{α a ,α max}; judge α c Whether the maximum overload constraint is met, the angle of attack α is obtained d ; Judge α d Whether the angle of attack change rate constraint is met, get the angle of attack Based on the initial conditions, we can get α at each moment down (t), and the lower boundary of the flight trajectory height-velocity envelope can be obtained by solving the aircraft motion equation until the terminal constraint is satisfied.

[0088] Determine the flight trajectory within the upper and lower boundaries of the altitude-speed profile, that is, meet the multi-constraint design conditions of the air-breathing powered aircraft trajectory. So far, the combined power air-breathing mode flight trajectory design is completed.

[0089] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A combined power air-breathing mode flight envelope design and trajectory optimization method according to claim 1, characterized in that: The optimization method comprises the following steps: Obtain flight trajectory design input conditions; Analyze the air-breathing engine operating envelope, flight overload, and dynamic pressure flight trajectory design constraints based on mission requirements; Solve the attack angle profile α that satisfies the constraints up (t), obtain the upper boundary of the flight envelope in the altitude-speed profile; Solve the downward attack angle profile α that satisfies the constraints down (t), obtain the lower boundary of the flight envelope in the altitude-speed profile; The flight trajectory is determined within the upper and lower boundaries of the altitude-speed profile, that is, the multi-constraint design conditions of the trajectory of the air-breathing powered aircraft are met.

2. A combined power air-breathing mode flight envelope design and trajectory optimization method according to claim 1, characterized in that: The upper boundary of the flight envelope in the altitude-speed profile is the maximum altitude that can be flown at various flight speeds while satisfying the maximum angle of attack, maximum rate of change of angle of attack, minimum acceleration capability, and engine operating envelope constraints.

3. A combined power-breathing mode flight envelope design and trajectory optimization method according to claim 1 or 2, characterized in that: The solution satisfies the constraint condition of the upward attack angle profile α up (t), obtain the upper boundary of the flight envelope in the altitude-speed profile, including the following steps: (1) Obtaining the initial value of the flight state based on the initial conditions of the flight mission; (2) Calculate the corresponding angle of attack α based on the maximum altitude constraint allowed by the engine a ; (3) Determine whether the minimum acceleration capacity constraint is met and obtain the angle of attack α b ; (4) Determine whether the angle of attack change rate constraint is met and obtain the angle of attack α up ; (5) Based on the initial conditions of step (1), the altitude-velocity envelope upper boundary of the flight trajectory can be obtained according to the above steps (2), (3), and (4). The aircraft motion equation is solved until the terminal constraint is satisfied.

4. A combined power-breathing mode flight envelope design and trajectory optimization method according to claim 1, characterized in that: The lower boundary of the flight envelope in the speed-altitude profile is the minimum altitude that can be flown while satisfying the maximum angle of attack, maximum rate of change of angle of attack, maximum dynamic pressure, maximum overload, maximum acceleration capability and engine operating range constraints.

5. A combined power air-breathing mode flight envelope design and trajectory optimization method according to claim 1 or 4, characterized in that: The solution satisfies the constraint condition of the downward attack angle profile α down (t), obtain the lower boundary of the flight envelope in the altitude-speed profile, including the following steps: (1) Obtaining the initial value of the flight state based on the initial conditions of the flight mission; (2) Calculate the corresponding angle of attack α by combining the lower limit of the engine's allowed altitude and the maximum dynamic pressure limit c ; (3) Determine α c Whether the maximum overload constraint is met, the angle of attack α is obtained down ; (4) Determine whether the angle of attack change rate constraint is met and obtain the angle of attack α down ; (5) Based on the initial conditions of step (1), the α at each moment can be obtained according to the above steps (2), (3), and (4). down (t), and the lower boundary of the flight trajectory height-velocity envelope can be obtained by solving the aircraft motion equation until the terminal constraint is satisfied.

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