Boost separation method considering speed constraint of unpowered flight segment

Abstract

The application discloses a boost separation method considering speed constraint of unpowered flight section, comprising the following steps: S1, recording the time when the engine stops working as the earliest separation time tp0; S2, determining the latest separation time tp_max, wherein the tp_max is the latest time when the control system can control the aircraft to reach the target position according to the required speed and height; S3, obtaining the altitude-speed curve of the ideal trajectory as the ideal speed curve, and recording the ideal speed curve as the H-V curve; S4, determining the separation time of the aircraft according to the H-V curve in the actual flight process. The separation method provided by the application limits the speed of the separation time of the aircraft and the boost stage, provides a suitable initial speed for the unpowered flight section of the aircraft, and is simple, efficient and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of aircraft control technology and relates to a boost separation method that takes into account the speed constraints of the unpowered flight phase. Background Technology

[0002] With the rapid development of air defense weapons, specific aircraft are needed to participate in the testing and verification of these weapons at required speeds and within designated airspace. These aircraft typically use solid-propellant rocket engines for boosting. After separation, the control system activates to control the aircraft's attitude, speed, and altitude to meet the testing requirements of air defense weapons. This method simulates airborne deployment, is simple and efficient, and offers high reliability and safety. Furthermore, the control system can meet different speed and altitude requirements, making it highly adaptable.

[0003] Since the spacecraft is unpowered after separation, the velocity at the separation point directly affects its subsequent velocity and altitude. This separation velocity is closely related to engine thrust and the spacecraft's aerodynamic characteristics. First, the characteristics of solid rocket motors indicate that the total thrust varies under different temperature conditions; the higher the temperature, the greater the total thrust. As the total thrust increases, the velocity at separation will also increase. Second, aerodynamic deviations, mass characteristic deviations, and atmospheric parameter deviations all affect the flight trajectory, and solid rocket motors cannot adaptively adjust their thrust to regulate the separation velocity. Both of these factors can result in significant dispersion in the altitude and velocity of the spacecraft after separation, exceeding the experimental requirements. Therefore, the aforementioned method of launching a spacecraft using a solid rocket motor requires constraints on the separation velocity to meet the experimental conditions. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned shortcomings and provide a booster separation method that considers velocity constraints during the unpowered flight phase. This solves the technical problem that existing separation methods result in large dispersions of vehicle altitude and velocity under complex operating conditions, exceeding the experimental requirements. The separation method proposed in this invention restricts the velocity of the vehicle at the moment of separation from the booster stage, providing a suitable initial velocity for the unpowered flight phase. This separation method is simple, efficient, and easy to implement.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A boost-separation method considering velocity constraints during the unpowered flight phase includes:

[0007] S1 records the moment when the engine finishes working as the earliest separation time tp0;

[0008] S2 determines the latest separation time tp_max, which is the latest time that the control system can control the aircraft to reach the target position at the required speed and altitude.

[0009] S3 obtains the altitude-velocity curve of the ideal trajectory as the ideal velocity curve, and denotes the ideal velocity curve as the HV curve;

[0010] During the actual flight of S4, the separation time of the aircraft is determined based on the HV curve. The specific method is as follows:

[0011] S4.1 Determine whether the current time t satisfies t≥tp0. If t≥tp0, proceed to step S4.2.

[0012] S4.2 Determine whether the current time t satisfies t≤tp_max. If t≤tp_max, proceed to step S4.3; otherwise, separate the spacecraft at the current time t.

[0013] S4.3 Based on the actual altitude H(t) and HV curve of the aircraft at the current time t, obtain the ideal speed separateV(t) at the current time t. Determine whether the flight speed V(t) of the aircraft at the current time t satisfies V(t) < separateV(t). If V(t) < separateV(t), separate the aircraft at the current time t; otherwise, return to step S4.2 at the next time.

[0014] Furthermore, in step S3, the ideal trajectory is the trajectory in which the altitude and speed of the unpowered flight segment are within the required speed and altitude range, and the energy is in the middle range among all the deflection trajectories.

[0015] Furthermore, in step S3, each deflection trajectory includes deflection trajectories under high temperature, normal temperature and low temperature conditions. High temperature and low temperature are the highest and lowest operating temperatures in the actual process, and normal temperature is 20℃~25℃.

[0016] An ideal trajectory is one where energy is moderate under all operating conditions, including high temperature, normal temperature, and low temperature.

[0017] Furthermore, in step S3, the method for determining the ideal trajectory includes:

[0018] The standard ballistic trajectory under normal temperature conditions is selected as the reference trajectory, denoted as trajectory 1;

[0019] The altitude-velocity curve of trajectory 1 was used as the criterion for delay separation in full-condition simulation.

[0020] If the velocity and altitude of all the deflection trajectories obtained from the full-condition simulation are within the required range, then trajectory 1 is the ideal trajectory.

[0021] Otherwise, in the biased trajectory of normal separation, select a trajectory with a speed higher or lower than Trajectory 1 as the reference, denoted as Trajectory 2, and perform a full-condition simulation again; the speed deviation between Trajectory 2 and Trajectory 1 ≤ 5%.

[0022] Repeat the above steps until the altitude-speed curve of a certain trajectory is used as the delay separation judgment criterion for a full-condition simulation, and the speeds and altitudes of all the biased trajectories obtained are within the required ranges. Then, this trajectory is taken as the ideal trajectory.

[0023] Furthermore, in step S2, according to the simulation results of the normal separation biased trajectory, determine the latest separation time tp_max by the trial-and-error method.

[0024] The normal biased trajectory is the trajectory where the aircraft separates immediately when the engine ends its operation.

[0025] Furthermore, according to the simulation results of the normal separation biased trajectory under normal temperature, high temperature, and low temperature conditions, determine the latest separation time tp_max by the trial-and-error method; high temperature and low temperature are the highest and lowest working temperatures in the actual process, and normal temperature is 20°C - 25°C; the method for determining the latest separation time tp_max specifically includes:

[0026] Determine the initial value of tp_max as 1 / 3 of the total rising time of the standard trajectory of normal separation at normal temperature.

[0027] Adjust the value of tp_max within the range of the initial value ±2s according to the trajectory simulation results, so that tp_max is the critical value at which the control system can control the speed and altitude of the aircraft within the required ranges during the unpowered flight segment after all the biased trajectories separate at this moment.

[0028] Furthermore, in step S4.3, use the actual altitude H(t) of the aircraft at the current moment t to interpolate the H-V curve to obtain the ideal speed separateV(t) at the current moment t.

[0029] Furthermore, in step S4.3, the situation where it is judged that V(t) < separateV(t) means that the measured values of the inertial navigation device for ten consecutive frames all satisfy V(t) < separateV(t).

[0030] Furthermore, in step S4, when t = tp0, if the flight speed V(t) measured by the inertial navigation device satisfies V(t) < separateV(t) for ten consecutive frames, then the separation time tp = tp0 + 9Ts, where Ts is the time of one frame, otherwise tp = 999.

[0031] Further, in step S4, when tp0 < t < tp_max, if the flight speed V(t) measured by the inertial navigation device satisfies V(t) < separateV(t) for ten consecutive frames, the time at this moment is recorded as the speed separation time tp_v, and the separation time tp = tp_v; otherwise, tp = 999.

[0032] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0033] (1) The present invention creatively proposes a boost separation method considering the speed constraint in the unpowered flight segment. By adaptively adjusting the separation time to constrain the speed, the speed and altitude dispersion of the aircraft during unpowered flight are reduced, and the comprehensive performance of the trajectory is improved.

[0034] (2) Under the same engine temperature conditions, the method of the present invention reduces the influence of external disturbances such as aerodynamic deviation and mass deviation on the trajectory, and reduces the pressure on the control system in the unpowered segment.

[0035] (3) The ideal speed curve of the present invention is obtained by simulating the pulled-off trajectory within the entire working temperature range, enabling the aircraft to adapt to the differences in engine performance under different temperature conditions, and having strong inclusiveness and applicability.

[0036] (4) In the process of judging the separation point, the present invention gives reasonable thresholds such as the latest separation time and the ideal speed, and gives the determination method of the above thresholds, and realizes precise and reliable control of the separation of the aircraft based on the thresholds. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 FIG. is the simulation result of delayed separation obtained by using the separation method of the present invention. Among them, (a) and (b) are the altitude simulation results and speed simulation results at low temperature of -40°C respectively, (c) and (d) are the altitude simulation results and speed simulation results at normal temperature of 20°C respectively, and (e) and (f) are the altitude simulation results and speed simulation results at high temperature of 55°C respectively. <000008​​​​​​​​​​The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0041] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0042] This involves a separation strategy for aircraft propelled by solid rocket motors, which constrains the velocity at the separation point to constrain the altitude and velocity dispersion of the trajectory under the influence of multiple disturbances.

[0043] This invention provides a separation strategy for spacecraft using solid rocket motors as boosters, taking into account velocity constraints at the separation point. Even with significant deviations in engine thrust, atmospheric conditions, and aerodynamic parameters, this strategy ensures the spacecraft has a suitable initial velocity at separation, thereby reducing the velocity and altitude dispersion during the subsequent unpowered flight phase and improving the overall performance of the spacecraft.

[0044] Because the deceleration effect of the spacecraft before separation from the booster stage (after the booster stage has finished operating) is better than the deceleration effect of the spacecraft itself after booster separation under unpowered flight conditions, this invention considers situations where the total engine impulse is large or various deviations cause excessive ballistic energy. The separation of the spacecraft from the solid rocket engine is delayed, allowing the spacecraft to carry the booster stage and continue unpowered flight for a period to achieve rapid deceleration. Booster separation occurs when the speed decreases to the ideal value. The specific solution of this invention is described below:

[0045] 1) Firstly, for safety reasons, the spacecraft does not separate while the solid rocket engine is working, and the moment when the engine finishes working is recorded as the earliest separation time tp0.

[0046] 2) After the spacecraft separates from the booster stage, the control system engages. A delay in the separation time corresponds to a delay in the control system's engagement. If the control system engages too late, it cannot function effectively and may fail to control the spacecraft to reach the required speed and altitude for the experiment. Therefore, a latest separation time, tp_max, is designed. tp_max can be initially determined as 1 / 3 of the ascent time of a standard ballistic trajectory under normal temperature conditions. This can be adjusted appropriately within ±2 seconds based on simulation results. The final adjusted tp_max must ensure that the separation at this moment constrains the velocity and that the control system has sufficient time to control the ascent phase after separation.

[0047] 3) Since the engine may operate at different temperatures, and engine characteristics vary with temperature, during the preliminary design simulation, simulations are carried out under different temperature conditions such as normal temperature, high temperature, and low temperature. According to the simulation results, a trajectory with the height and speed in the non-powered flight segment within the required range of the test is selected as the ideal trajectory. This trajectory should meet all index requirements and have medium energy among the full-condition offset trajectories to ensure that when the trajectory energy is on the high or low side, the control system has the ability to control it near the ideal trajectory, reducing the speed and altitude dispersion. Therefore, the standard trajectory at normal temperature can be selected as the benchmark, and it is modified and adjusted through subsequent simulation verification, and the ideal trajectory is obtained through continuous iteration. The altitude-speed curve of this trajectory is used as the ideal speed curve H-V.

[0048] 4) During the actual flight process, the ideal speed at the current moment can be obtained by interpolating the H-V curve with the height H(t) at any time point t, denoted as separateV(t). When t≥tp0, the boost separation judgment starts. If the flight speed V(t) is less than separateV(t) at a certain moment, it is considered that the trajectory energy is close to the ideal trajectory at this time, and this moment is recorded as the speed separation time tp_v (tp0≤tp_v≤tp_max), and the aircraft is separated from the booster stage. If the flight speed V(t) is always greater than separateV(t) during the period of tp0≤t≤tp_max, the booster stage is separated at the moment of tp_max to ensure the final control accuracy.

[0049] Embodiment:

[0050] This embodiment provides a separation strategy considering the separation point speed constraint for an aircraft using a solid rocket engine as the booster stage, reducing the speed and altitude dispersion of the aircraft after separation, and improving the trajectory performance under full-condition conditions.

[0051] As Figure 3 shown, the steps of this embodiment are as follows:

[0052] 1) Conduct mathematical simulations on the normal separation trajectories under high temperature, normal temperature, and low temperature conditions, determine the latest separation time tp_max and the ideal speed curve H-V, and write them into the on-board computer;

[0053] 2) Judge the axial overload nx measured by the inertial navigation device. If nx<0 is satisfied for ten consecutive frames, it is considered that the booster engine has been shut down at this time, and this moment is recorded as the minimum separation time tp0. When the time t<tp0, the separation time tp = 999, that is, it is ensured that there will be no separation during the engine operation;

[0054] 3) Interpolate the H-V curve according to the height H(t) measured by the inertial navigation device in real time to obtain the real-time ideal speed separateV(t);

[0055] 4) When t = tp0, if the speed V(t) measured by the inertial navigation device satisfies V(t) < separateV(t) for ten consecutive frames, then tp = tp0 + 9Ts (Ts is the time of one frame), otherwise tp = 999;

[0056] 5) When tp0 < t < tp_max, judge the speed V(t) measured by the inertial navigation device. If it satisfies V(t) < separateV(t) for ten consecutive frames, record the current time as the speed separation time tp_v, and the separation time tp = tp_v, otherwise tp = 999;

[0057] 6) When tp0 < t < tp_max, if V(t) > separateV(t) is always satisfied, then the separation time tp = tp_max, and the aircraft and the booster stage separate at the latest separation time.

[0058] The beneficial effects of the present invention can be proved through mathematical simulation. Figure 1 This is the simulation result of the delayed separation strategy proposed by the present invention (judging that the aircraft speed meets the conditions before separation after the engine shuts down), Figure 2 This is the simulation result of the traditional separation strategy (the traditional separation strategy only judges that the engine shuts down and then separates immediately). The statistical results of the speed and the highest point height dispersion are shown in Table 1. Each simulation condition includes multiple disturbance items such as initial disturbance, aerodynamics, and mass characteristics, totaling 64 offset trajectories. It can be seen that at the same temperature, the height and speed dispersion of the trajectory during delayed separation are smaller; under the full working conditions of low temperature, normal temperature, and high temperature, the ends of some trajectories of normal separation diverge, while the trajectory control performance of delayed separation is good and the dispersion is small, which proves the effectiveness of the delayed separation strategy.

[0059] Table 1 Statistical results of speed and height dispersion

[0060]

[0061] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limitations on the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent replacements, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

[0062] The content not detailedly described in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A boost-separation method considering velocity constraints during the unpowered flight phase, characterized in that, include: S1 records the moment when the engine finishes working as the earliest separation time tp0; S2 determines the latest separation time tp_max, which is the latest time that the control system can control the aircraft to reach the target position at the required speed and altitude. S3 obtains the altitude-velocity curve of the ideal trajectory as the ideal velocity curve, and denotes the ideal velocity curve as the HV curve; During the actual flight of S4, the separation time of the aircraft is determined based on the HV curve. The specific method is as follows: S4.1 Determine whether the current time t satisfies t≥tp0. If t≥tp0, proceed to step S4.

2. S4.2 Determine whether the current time t satisfies t≤tp_max. If t≤tp_max, proceed to step S4.3; otherwise, separate the spacecraft at the current time t. S4.3 Based on the actual altitude H(t) and HV curve of the aircraft at the current time t, obtain the ideal speed separateV(t) at the current time t. Determine whether the flight speed V(t) of the aircraft at the current time t satisfies V(t) < separateV(t). If V(t) < separateV(t), separate the aircraft at the current time t; otherwise, return to step S4.2 at the next time. In step S2, the latest separation time tp_max is determined by trial and error based on the simulation results of the normal separation and deflection trajectory. A normal deflection trajectory is the trajectory by which the aircraft separates immediately after the engine stops firing; Based on the simulation results of normal separation and deflection trajectory under normal temperature, high temperature and low temperature conditions, the latest separation time tp_max is determined by trial and error. High temperature and low temperature refer to the highest and lowest operating temperatures in the actual process, while ambient temperature is 20℃~25℃; the specific methods for determining the latest separation time tp_max include: The initial value of tp_max is set to 1 / 3 of the total ascent time of a standard ballistic trajectory under normal separation at room temperature; Based on the ballistic simulation results, the value of tp_max is adjusted within the range of ±2s from the initial value, so that tp_max is the critical value that allows the control system to keep the speed and altitude of the aircraft within the required range during the unpowered flight phase after all the deflected trajectories separate at that moment.

2. The boost-separation method considering velocity constraints during the unpowered flight phase according to claim 1, characterized in that, In step S3, the ideal trajectory is the trajectory in which the altitude and speed of the unpowered flight phase are within the required speed and altitude range, and the energy is in the middle range among all the deflection trajectories.

3. The boost-separation method considering velocity constraints during the unpowered flight phase according to claim 2, characterized in that, In step S3, each deflection trajectory includes deflection trajectories under high temperature, normal temperature and low temperature conditions. High temperature and low temperature are the highest and lowest operating temperatures in the actual process, and normal temperature is 20℃~25℃. An ideal trajectory is one where energy is moderate under all operating conditions, including high temperature, normal temperature, and low temperature.

4. The boost-separation method considering velocity constraints during the unpowered flight phase according to claim 1, characterized in that, In step S3, the method for determining the ideal trajectory includes: The standard ballistic trajectory under normal temperature conditions is selected as the reference trajectory, denoted as trajectory 1; The altitude-velocity curve of trajectory 1 was used as the criterion for delay separation in full-condition simulation. If the velocity and altitude of all the deflection trajectories obtained from the full-condition simulation are within the required range, then trajectory 1 is the ideal trajectory. Otherwise, select a trajectory with a speed higher or lower than Trajectory 1 as the benchmark in the normal separation offset trajectory, denoted as Trajectory 2, and perform a full-condition simulation again; the speed deviation between Trajectory 2 and Trajectory 1 ≤ 5%; Repeat the above steps until a full-condition simulation is performed using the altitude-speed curve of a certain trajectory as the delay separation judgment criterion, and the speeds and altitudes of all offset trajectories obtained are within the required range. This trajectory is regarded as the ideal trajectory.

5. The boost-separation method considering velocity constraints during the unpowered flight phase according to claim 1, characterized in that, In step S4.3, use the actual altitude H(t) of the aircraft at the current time t to interpolate the H-V curve to obtain the ideal speed separateV(t) at the current time t.

6. The boost-separation method considering velocity constraints during the unpowered flight phase according to claim 1, characterized in that, In step S4.3, when it is judged that V(t) < separateV(t), the measured values of the inertial navigation device for ten consecutive frames all satisfy V(t) < separateV(t).

7. The boost-separation method considering velocity constraints during the unpowered flight phase according to claim 1, characterized in that, In step S4, when t = tp0, if the flight speed V(t) measured by the inertial navigation device satisfies V(t) < separateV(t) for ten consecutive frames, then the separation time tp = tp0 + 9Ts, where Ts is the time of one frame, otherwise tp = 999.

8. A boost-separation method considering velocity constraints during the unpowered flight phase according to claim 7, characterized in that, In step S4, when tp0 < t < tp_max, if the flight speed V(t) measured by the inertial navigation device satisfies V(t) < separateV(t) for ten consecutive frames, record this time as the speed separation time tp_v, and the separation time tp = tp_v, otherwise tp = 999.

Images