Speed constraint separation method for solid rocket engine boosted vehicle

Abstract

The application discloses a speed-restricted separation method of a solid rocket engine-boosted vehicle, which comprises the following steps: S1, determining a first maximum speed threshold Vmax1, a second maximum speed threshold Vmax2 and a latest separation time Tmax; S2, comparing a full-missile flight speed Vt0 at the end of engine operation with the first maximum speed threshold Vmax1, and separating the vehicle in time at the end of engine operation when Vt0Vmax1, entering step S3; S3, delaying the separation of the vehicle after the end of engine operation; the specific method of delaying the separation is as follows: if the full-missile flight time is less than Tmax, comparing a full-missile flight speed Vt at the current time with Vmax2, separating the vehicle when VtVmax2, and continuing the full-missile flight when Vt≥Vmax2; if the full-missile flight time is greater than or equal to Tmax, separating the vehicle. The application can judge the separation time according to the real-time flight speed, provide a suitable speed after the separation of the main stage, and ensure the flight control requirements and speed requirements of the main stage after the separation.

Description

Technical Field

[0001] This invention belongs to the field of aircraft control technology, specifically relating to a velocity constraint separation method for a solid rocket engine-assisted glider. Background Technology

[0002] With the increasing demand for high-altitude testing in China and the growing need for aircraft-based drop tests, there is an urgent need for a safe and low-cost testing method to simulate aircraft drop tests and deliver the test subject to the designated airspace at the required flight speed. Therefore, adopting a method such as... Figure 1 Solid rocket engines, acting as booster stages, provide initial propulsion to the main stage of the vehicle. By designing relevant strategies, they can be widely adopted to ensure the main stage reaches a specified altitude at a designated speed. After the engine finishes firing, booster separation can occur, the main stage begins control, and the missile climbs to the designated altitude. Attitude adjustments are made to simulate aircraft launch, ensuring the subsequent flight trajectory meets performance requirements. This approach not only reduces testing costs and shortens the testing cycle but also improves safety. Since the solid rocket engine provides initial propulsion to the main stage, the separation speed directly determines the flight distance and characteristics of the main stage after separation. However, factors such as changes in atmospheric density, wind patterns at different altitudes, aerodynamic parameter deviations and mass characteristic deviations of the main stage, and the total impulse deviation of the solid rocket engine itself all contribute to a random dispersion of the main stage's flight speed after separation. Therefore, simply sending the separation command after the engine finishes firing is insufficient to meet the required flight speed.

[0003] Solid rocket engines differ from liquid rocket engines. Liquid rocket engines can measure flight speed in real time through an onboard inertial navigation system and adjust the supply of liquid fuel according to changes in flight speed to ensure that the flight speed of the main stage is within the required range after separation. However, once a solid rocket engine is completed, the thrust it provides cannot be changed according to changes in the external environment and aerodynamic parameter errors. Therefore, in actual flight, missiles using traditional solid rocket engines as booster systems cannot adjust their thrust. Furthermore, due to various deviations, the flight speed of the main stage will have a large deviation range after separation.

[0004] Therefore, how to design a separation strategy for missiles or launch vehicles that use solid rocket engines as boosters, and minimize the velocity dispersion of the main stage vehicle during the glide phase after separation, directly affects the success or failure of the project and its cost (the cost of solid rocket engines is much lower than that of liquid rocket engines). Summary of the Invention

[0005] The application aims at overcoming the above-mentioned defects, providing a speed-constrained separation method based on a solid rocket engine boosted aircraft, solving the technical problem that the existing separation method cannot effectively ensure that the velocity of the main stage aircraft in the glide section is within the required range, and providing a self-adaptive separation strategy which can determine the separation time according to the real-time flight speed and provide a suitable speed for the main stage after separation, thereby ensuring the flight control requirements and speed requirements of the main stage after separation.

[0006] To achieve the above-mentioned application purposes, the application provides the following technical solutions.

[0007] A speed-constrained separation method based on a solid rocket engine boosted aircraft, comprising:

[0008] S1 determining a first maximum speed threshold Vmax1, a second maximum speed threshold Vmax2 and a latest separation time Tmax by simulating the limit pull-off trajectory of the aircraft;

[0009] S2 comparing the full-missile flight speed Vt0 at the end of the engine operation with the first maximum speed threshold Vmax1, when Vt0Vmax1, making the aircraft timely separate at the end of the engine operation, and when Vt0≥Vmax1, entering step S3;

[0010] S3 making the aircraft delay separation after the end of the engine operation; the specific method of delay separation is: if the full-missile flight time is <Tmax, comparing the full-missile flight speed Vt at the current time with Vmax2, when VtVmax2, making the aircraft separate, and when Vt≥Vmax2, continuing the full-missile flight; if the full-missile flight time is ≥Tmax, making the aircraft separate;

[0011] The speed of the aircraft when separating from the engine is recorded as the initial speed; the first maximum speed threshold Vmax1 is the maximum initial speed of the aircraft which timely separates at the end of the engine operation and can meet the glide section speed constraint and reach the target point under the control of the control module; the second maximum speed threshold Vmax2 is the maximum initial speed of the aircraft which delays separation after the end of the engine operation and can meet the glide section speed constraint and reach the target point under the control of the control module; and the latest separation time Tmax is the latest separation time of the aircraft which delays separation after the end of the engine operation and can reach the target point under the control of the control module.

[0012] Further, in step S1, the determination method of the first maximum speed threshold Vmax1 comprises:

[0013] Vmax1=(V_m+V_m1) / 2;

[0014] wherein V_m is the maximum speed of the standard trajectory, and V_m1 is the maximum speed of the energy minimum trajectory in the limit pull-off trajectory.

[0015] Further, in step S1, the determination method of the second maximum speed threshold Vmax2 includes:

[0016] Selecting the energy maximum trajectory in the limit pull-off, determining the initial value of Vmax2 according to the energy maximum trajectory, and through the loop trial and error verification in 64 limit pull-off trajectories, the maximum initial speed that can make each limit pull-off trajectory meet the glide section speed constraint and can reach the target point is taken as Vmax2.

[0017] Further, in step S1, the determination method of the initial value of Vmax2 includes:

[0018] Determine the lift T of the aircraft in the maximum angle of attack and the maximum rudder angle state:

[0019] T = 5 × G;

[0020] Wherein, G is the gravity;

[0021] The speed of the energy maximum trajectory in the limit pull-off trajectory is taken as the initial value of Vmax2.

[0022] Further, in step S1, the determination method of Tmax includes:

[0023] Using enumeration method, the latest separation time that can make each limit pull-off trajectory can reach the target point is taken as Tmax.

[0024] Further, in step S1, the determination method of Tmax includes:

[0025] T max = T Vmin × (1+20%);

[0026] Wherein, T Vmin is the time when the speed of the energy maximum trajectory in the limit pull-off trajectory reaches Vmax2.

[0027] Further, the limit pull-off trajectory is the maximum pull-off combination considering the flight performance influencing factors, and the limit pull-off trajectory is 64.

[0028] Further, in step S2, when Vt0 < Vmax1, the method for separating the aircraft in time when the engine stops working includes: separating the aircraft within 0-1s after the engine stops working.

[0029] Further, when the full flight speed is compared with the first maximum speed threshold Vmax1 or the second maximum speed threshold Vmax2, the comparison result is determined according to the full flight speed measured by the inertial measurement unit for 10 frames in succession, and when the comparison results obtained by comparing the full flight speed measured by the inertial measurement unit for 10 frames in succession with the first maximum speed threshold Vmax1 or the second maximum speed threshold Vmax2 are all the same, the comparison result is taken as the final comparison result.

[0030] Compared with the prior art, the present application has at least one of the following beneficial effects:

[0031] (1) The present application creatively proposes a speed-restricted separation method for a solid rocket engine boosted vehicle, which is a self-adaptive separation strategy, and can determine the separation time according to the real-time measured flight speed, and provide a suitable speed after the primary stage separation, so as to ensure the flight control requirements and speed requirements of the primary stage after separation;

[0032] (2) The present application improves the inclusiveness of flight energy performance to aerodynamic deviation and environmental deviation, and has stronger applicability;

[0033] (3) Compared with a liquid engine with adjustable thrust, the cost of the vehicle with the solid engine boosted stage of the present application is greatly reduced;

[0034] (4) The present application comprehensively considers various factors in the flight process, and gives reasonable judgment thresholds and determination methods, so that accurate and reliable separation control can be made according to the real-time flight conditions and the judgment thresholds. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a full flight diagram;

[0036] Figure 2 is a primary flight speed curve obtained by using the separation method of the present application;

[0037] Figure 3 is a limit pull-off simulation height map in the case of using the method of the present application;

[0038] Figure 4 is a limit pull-off simulation speed scatter diagram in the case of using the present application;

[0039] Figure 5 is a limit pull-off simulation height map in the case of not using the method of the present application;

[0040] Figure 6 is a limit pull-off simulation speed scatter diagram in the case of not using the method of the present application;

[0041] Figure 7 is a flow chart of the speed-restricted separation method for a solid rocket engine boosted vehicle of the present application. DETAILED DESCRIPTION

[0042] The features and advantages of the present application will become more apparent from the detailed description in combination with the accompanying drawings upon reading of the following detailed description.

[0043] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Unless specifically stated otherwise, the present disclosure is not to be construed as using terms or phrases such as "example," "for example," "exemplary," or "illustrative" to identify ideas or options that are preferred or superior over others.

[0044] When a solid rocket engine is used as a boost engine, the main stage is a powered flight missile, and by measuring the real-time flight speed, the present application uses an adaptive separation strategy to ensure that, within a certain range of environmental deviation and aerodynamic deviation, the main stage is provided with an appropriate initial speed, and through adjustment of the ascending stage, the flight speed of the main stage vehicle trajectory glide stage after separation is within a reasonable dispersion range, and at the same time, the restriction on engine thrust is relaxed, and the pressure on engine design is reduced. The present application is applied to rockets or missiles using solid rocket engines as boost stages, and the use of the strategy can reduce the dispersion of the powered glide speed of the main stage vehicle after separation and ensure the flight speed constraint requirement.

[0045] The specific technical solutions of the present application are as follows:

[0046] By analyzing the force on the unpowered whole missile (the whole of the vehicle and the engine) in the flight state (the solid engine has ended work), assuming that the attack angle a = 0 in the uncontrolled state, the lift of the axisymmetric missile is 0, then the whole missile resultant force is the sum of the whole missile drag and gravity, according to Newton's second law, the acceleration is

[0047] a z =(F x_z +G z ) / m z =F x_z / m z +g (1)

[0048] a q =(F x_q +G q ) / m q =F x_q / m z +g (2)

[0049] Wherein, a z and a q are the main stage vehicle acceleration and the whole missile acceleration respectively, F x_z =Ca z *q*S z , is the main stage drag; Fx_q = Ca q *q*S q , Ca is the drag coefficient, q is the dynamic pressure, G z and G q are the main stage vehicle gravity and total mass gravity respectively, m z and m q are the main stage vehicle mass and total mass respectively, g is the gravity acceleration, and S is the characteristic area.

[0050] By comparing formula (1) and formula (2), if F x_z <F x_q , then a z <a q , which ensures that the total mass deceleration effect is better than the main stage deceleration effect after separation during the unpowered flight stage, which is also the prerequisite for the adaptive separation strategy of the application.

[0051] For flight safety considerations, the boost stage separation operation can only be performed after the engine operation is completed. It has been proved by calculation that the total mass acceleration value is greater than the main stage acceleration value, so when the flight speed is greater than the ideal speed due to various aerodynamic deviations and environmental deviations, the boost stage can be considered not to be separated at the end of the solid propellant engine operation, and the total mass state continues to fly for a period of time to achieve the purpose of decelerating as soon as possible.

[0052] Based on the above conditions, the technical solution of the application is: ①First, design a first maximum speed threshold Vmax1, a second maximum speed threshold Vmax2 and a latest separation time Tmax; ②Secondly, compare the speed at the end of the engine operation with the first maximum speed threshold Vmax1, if less than Vmax1, it is considered that the flight speed of the main stage after separation is within the required range, and the solid engine is separated immediately after the engine operation is completed; when the speed at the end of the engine operation is greater than the maximum threshold Vmax1, it is considered that the existing speed will cause the flight speed of the main stage after separation to be greater than the proposed speed range, and the separation needs to be delayed, because the total mass continues to climb unpowered, the speed decreases, and the air density and dynamic pressure decrease, and the controllability becomes worse, in order to ensure the controllability of subsequent flight, the latest separation time Tmax needs to be set.

[0053] The selection method of Vmax1, Vmax2 and Tmax is as follows:

[0054] The 64 limit deviations are the maximum deviation combinations of factors affecting flight performance such as mass characteristics and aerodynamic parameters, which simulate the real flight state and ensure that the designed control system has sufficient stability margin. The 64 limit deviations are a rigorous test of the real environment.

[0055] (1) Vmax1 selection

[0056] Take the standard trajectory as an example, when the standard trajectory separates in time after the engine stops working, the initial speed provided by the main flight vehicle makes the subsequent trajectory speed of the main flight vehicle still greater than the flight speed constraint, it is considered that the engine energy is too large, Vmax1 should be less than the maximum speed V_m of the standard trajectory, the maximum speed of the minimum energy trajectory is V_ml, generally Vmax1 is selected near (V_m+V_ml) / 2;

[0057] (2) Vmax2 selection

[0058] The selection principle of delayed separation Vmax2 is to access the control system as early as possible to ensure the accuracy of control, when the real-time flight speed of the missile is less than Vmax2, it separates immediately. Similarly, taking 64 limit deviation trajectories as a benchmark, through simulation curve analysis, the trial and error method is used to select the appropriate Vmax2 to ensure the safety flight margin. Here, the appropriate Vmax2 means that the selected Vmax2 should be the critical speed that makes the 64 limit deviation trajectories separate at this speed, and can meet the glide segment speed constraint and reach the maximum initial speed of the target point under the control of the control module.

[0059] (3) The latest separation time Tmax selection

[0060] The selection of the latest separation time is to ensure that the main flight vehicle can complete the flight task smoothly. Therefore, the controllability requirement of the largest energy trajectory flight is analyzed to ensure that the main flight vehicle is controllable and can complete the unpowered flight stably. Through simulation curve analysis, the enumeration method is used to select the latest separation time. Tmax is the critical time that makes the 64 limit deviation trajectories separate at this time, and can reach the target point under the control of the control module. Separating later than this time may cause the maximum energy trajectory to fail to reach the target point. The determination of Tmax takes reaching the target point as the goal, and meeting the glide segment speed constraint is no longer a necessary condition for the flight of the vehicle.

[0061] The same type of vehicle may have large or small effects on flight speed due to different environments and differences in production processes. Figure 2The first point of each curve is the maximum speed point, and the second point is the separation point. As can be seen from the curve 1, the maximum speed is less than the set Vmax1 (Vmax1 is set to 955 m / s in this case) at the highest speed point, so the normal separation is performed. As can be seen from the curve 2, the speed is greater than the set speed at the highest speed point, so the delayed separation is performed, and the separation command is sent when the speed is less than Vmax2 (Vmax2 is set to 720 m / s in this case). As can be seen from the curve 3, the speed at the highest speed point is greater than Vmax1, the delayed separation is performed, and the boost separation is performed at Tmax (Tmax is set to 15 s after the launch in this case), so the boost separation is performed at Tmax, and the converging and descending speed dispersion effect is achieved.

[0062] Embodiment:

[0063] The method flow of the embodiment is shown in Figure 7 , and includes:

[0064] (1) Vmax1, Vmax2 and Tmax selection. The adaptive separation strategy based on the solid rocket engine proposed in the application selects the ideal speed scheme and compares with the limit pull-off speed curve of the normal time separation (separation at the end of engine operation). Since the engine energy is designed on the basis of the standard energy with slight increase to ensure sufficient thrust, Vmax1 is selected near the average value of the maximum value in the ideal state (i.e. the maximum speed of the standard trajectory) and the maximum value of the deviation limit (i.e. the maximum speed of the minimum energy trajectory). Vmax2 is selected according to the flight height and the pull-off state. For the flying vehicle with a gable wing, the dynamic pressure is selected as the basis, where p is the air density, V is the vehicle speed, 64 limit pull-off energy maximum trajectories (the energy maximum trajectory is the trajectory with the maximum vehicle speed at the end of engine operation) in the normal separation condition are selected, the dynamic pressure q = 1 x 10 5 near the speed of the maximum point is selected as Vmax2, and the speed at the lift T = 5 x G after the delayed separation is determined for the flying vehicle of all configurations. In addition to the enumeration method, Tmax can also be selected as T max = T Vmin x (1 + 20%), T Vmin is the time when the energy maximum trajectory speed reaches Vmax2, and T max = T Vmin x (1 + 20%), which is verified by simulation of 64 limit pull-offs.

[0065] (2) Vmax1, Vmax2 and other determined states are loaded into the guidance combination by the missile launch control device.

[0066] (3) After the missile (or aircraft) is out of the barrel, the axial overload nx measured by the guidance assembly is used to determine whether the engine has finished working. In order to ensure reliability, when nx is <0 for the first time for 10 frames, it is considered that the engine has finished working, and the flight speed Vt measured by the inertial measurement unit at this moment is extracted;

[0067] (4) The missile speed Vt is compared with Vmax1, if the real-time speed Vt measured by the inertial navigation for 10 frames is <Vmax1, the separation is performed at 0.8s after the engine has finished working; if Vt>Vmax1, the separation is delayed until the real-time speed Vt measured by the inertial navigation for 10 frames is <Vmax2.

[0068] When the total flight time of the missile exceeds Tmax, the separation is performed immediately regardless of the value of the real-time flight speed Vt of the missile.

[0069] As Figure 3 , Figure 4 , Figure 5 and Figure 6 , through analysis of the extreme deviation simulation height and speed scatter diagram in the case of using the present application and not using the present application, it can be seen that, compared with the traditional separation mode, after the self-adaptive separation strategy designed by using the present application is adopted, the scatter of the trajectory maximum point is reduced from 1.2km to less than 1km, the speed scatter of the descending segment is reduced from 280m / s-460m / s to at least 280m / s-416m / s, and the speed scatter is reduced by about 45m / s, and the speed scatter of some extreme deviation trajectories is even smaller.

[0070] The present application is described in detail above in combination with specific embodiments and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that the technical solutions and embodiments of the present application can be replaced, modified or improved in many ways without deviating from the spirit and scope of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

[0071] The contents not described in detail in the specification of the present application are the known technology of those skilled in the art.

Claims

1. A speed constraint separation method for a solid rocket engine boosted vehicle, characterized in that, The method comprises the following steps: S1, determining a first maximum speed threshold Vmax1, a second maximum speed threshold Vmax2 and a latest separation time Tmax by simulating a limit pull-off trajectory of the aircraft; S2, comparing a full-missile flight speed Vt0 at the end of engine operation with the first maximum speed threshold Vmax1, when Vt0 < Vmax1, separating the aircraft in time at the end of engine operation, and when Vt0 ≥ Vmax1, entering step S3; S3, separating the aircraft after the end of engine operation; the specific method of delayed separation is: if the full-missile flight time < Tmax, comparing the full-missile flight speed Vt at the current time with Vmax2, when Vt < Vmax2, separating the aircraft, and when Vt ≥ Vmax2, continuing full-missile flight; if the full-missile flight time ≥ Tmax, separating the aircraft; The speed of the aircraft when separated from the engine is recorded as the initial speed; the first maximum speed threshold Vmax1 is the maximum initial speed of the aircraft separated in time at the end of engine operation, which can meet the glide segment speed constraint and reach the target point under the control of the control module; the second maximum speed threshold Vmax2 is the maximum initial speed of the aircraft separated after the end of engine operation, which can meet the glide segment speed constraint and reach the target point under the control of the control module; and the latest separation time Tmax is the latest separation time of the aircraft separated after the end of engine operation, which can reach the target point under the control of the control module.

2. The method of speed-restricted separation of a solid rocket engine boosted vehicle according to claim 1, wherein, In step S1, the determination method of the first maximum speed threshold Vmax1 comprises: Vmax1 = (V_m + V_m1) / 2; wherein V_m is the maximum speed of the standard trajectory, and V_m1 is the maximum speed of the energy minimum trajectory in the limit pull-off trajectory.

3. The method of speed-restricted separation of a solid rocket engine boosted vehicle according to claim 1, wherein In step S1, the determination method of the second maximum speed threshold Vmax2 comprises: selecting the trajectory with the maximum energy in the limit pull-off, determining the trial-and-error initial value of Vmax2 according to the trajectory with the maximum energy, and through the trial-and-error verification in the 64 limit pull-off trajectories, taking the maximum initial speed that can make each limit pull-off trajectory meet the glide segment speed constraint and reach the target point as Vmax2.

4. The method of speed-restricted separation of a solid rocket engine boosted vehicle according to claim 3, wherein In step S1, the determination method of the trial-and-error initial value of Vmax2 comprises: determining the lift T of the aircraft in the state of the maximum attack angle and the maximum rudder deflection angle: T = 5 × G; wherein G is the gravity; taking the speed of the trajectory with the maximum energy in the limit pull-off trajectory as the trial-and-error initial value of Vmax2.

5. The method of speed-restricted separation of a solid rocket engine boosted vehicle according to claim 1, wherein In step S1, the determination method of Tmax comprises: using the enumeration method, taking the latest separation time that can make each limit pull-off trajectory reach the target point as Tmax.

6. The method of speed-restricted separation of a solid rocket engine boosted vehicle according to claim 1, wherein In step S1, the determination method of Tmax comprises: T max = T Vmin x (1 + 20%); where T Vmin is the time at which the velocity of the maximum energy trajectory of the limiting pull-up trajectory reaches Vmax2.

7. The method of speed-restricted separation of a solid rocket engine boosted vehicle according to claim 1, wherein The limit pull-off trajectory is the maximum pull-off combination term considering the influence factors of flight performance, and the limit pull-off trajectory is 64.

8. The method of speed-restricted separation of a solid rocket engine boosted vehicle according to claim 1, wherein In step S2, when Vt0 < Vmax1, the method of separating the aircraft in time at the end of engine operation comprises: separating the aircraft within 0-1s after the end of engine operation.

9. The method of speed-restricted separation of a solid rocket engine boosted vehicle according to claim 1, wherein When the all-out flight speed is compared with the first maximum speed threshold Vmax1 or the second maximum speed threshold Vmax2, the comparison result is determined according to the all-out flight speed measured by the inertial measurement unit for 10 frames continuously, and when the comparison results obtained by comparing the all-out flight speed measured by the inertial measurement unit for 10 frames continuously with the first maximum speed threshold Vmax1 or the second maximum speed threshold Vmax2 are all the same, the comparison result is taken as the final comparison result.

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