Aircraft trajectory optimization method based on fixed thrust engine

Abstract

The invention discloses an aircraft trajectory optimization method based on a fixed thrust engine, and belongs to the field of guidance control, and the method comprises the steps: S1, building an aircraft dynamics model, and determining the working parameters of the engine; s2, determining a drop point range and drop point parameters; s3, determining a power-on point area and a power-off point area which can meet the drop point range and the drop point parameters through Monte Carlo simulation, and obtaining a flight control domain; and S4, making a guidance strategy of an engine working section based on the flight control domain. For the engine which can only be ignited for one time, the trajectory is only adjusted in the working period of the engine, the situation that attitude control consumption is too much due to frequent attitude adjustment is avoided, the attitude control total impulse and the attitude control service life requirement are optimized, and the drop point precision is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of guidance and control, and to ballistic optimization of spacecraft flying on extraterrestrial bodies based on fixed thrust and total impulse as orbital control power, and particularly to a ballistic optimization method for spacecraft based on a fixed thrust engine. Background Technology

[0002] Extraterrestrial objects are mainly divided into those with atmospheric environments and those without. With the continuous development of deep space exploration missions, higher demands are placed on the landing accuracy and takeoff control of spacecraft on extraterrestrial bodies (such as the Moon and Mars). For exploration of objects with atmospheric environments, spacecraft can use aerodynamics to adjust their flight attitude, requiring relatively low energy for attitude control. However, for exploration of objects without atmospheric environments, spacecraft cannot use aerodynamics for attitude adjustment and must rely entirely on their own propulsion systems for orbit and attitude control.

[0003] Currently, ballistic optimization methods for spacecraft operating in atmospheric-free environments often employ the establishment of dynamic models combined with intelligent optimization algorithms (such as genetic algorithms and particle swarm optimization) for target simulation to determine the optimal control strategy. However, these methods typically assume that the engine can ignite multiple times or that the thrust is adjustable. For spacecraft with only single-ignition capability, their control degrees of freedom are limited, and the landing accuracy heavily depends on the control strategy during the engine's operational phase.

[0004] In existing technologies, for spacecraft operating in atmospheric environments, frequent attitude adjustments are often necessary during flight to ensure landing accuracy. This leads to a significant increase in attitude control fuel consumption, consequently increasing the overall weight of the spacecraft and mission costs. This is especially true for spacecraft capable of secondary launches and single-fire capability (such as solid rocket motors), which require continuous attitude and orbit control propulsion. While strict attitude control throughout the flight can guarantee landing, it increases fuel consumption, raising the spacecraft's weight. Furthermore, since their engines are single-fire capable, fuel depletion in the attitude control system will severely impact mission success rates.

[0005] Therefore, there is an urgent need for a ballistic optimization scheme for fixed-thrust, single-ignition engines that can minimize attitude control fuel consumption and improve mission reliability and economy while ensuring landing accuracy. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for optimizing the trajectory of an aircraft based on a fixed thrust engine.

[0007] The objective of this invention is achieved through the following technical solution: A method for optimizing the trajectory of an aircraft based on a fixed-thrust engine is provided, including: S1. Establish the aircraft dynamics model and determine the engine operating parameters; S2. Determine the landing point range and landing point parameters; S3. The activation and deactivation regions that can satisfy the landing range and landing parameters are determined through Monte Carlo simulation, thus obtaining the flight control domain; S4. Develop a guidance strategy for the engine operating phase based on the flight control domain.

[0008] In some embodiments, the aircraft dynamics model is as follows: in, Indicates the mass of the aircraft. Indicates the speed of the aircraft; Indicates time; Indicates engine thrust; Indicates the angle of attack; Indicates the trajectory inclination angle; ( x, y () indicates location; This indicates the engine's power consumption per second.

[0009] In some embodiments, the landing parameters include landing speed and landing angle.

[0010] In some embodiments, step S3 specifically includes: The boundary trajectory is determined based on the impact point range and the gravitational flight constraints. The engine shutdown and startup areas are determined based on the boundary trajectory. The boundary area is determined based on the boundary trajectory.

[0011] In some embodiments, formulating a guidance strategy for the engine operating phase based on the flight control domain includes: During engine operation, when the aircraft touches the flight control domain, it adjusts its flight attitude to ensure that the aircraft shuts down within the shutdown point area constraint.

[0012] In some embodiments, the flight control domain has upper and lower margins, and the guidance strategy satisfies: in, This represents the upper boundary function of the flight control domain. This represents the lower boundary function of the flight control domain. For lower margin, For the sake of margin, Indicates the location of the aircraft.

[0013] It should be further noted that the technical features corresponding to the above embodiments can be combined or substituted with each other to form new technical solutions without conflict.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention adjusts the trajectory and determines the flight control domain during the engine operation phase, using it as a constraint for guidance. Traditional methods, to ensure landing accuracy, typically require high-frequency attitude maintenance and trajectory fine-tuning throughout the entire flight (including the long unpowered taxiing phase), necessitating continuous operation of the attitude control engine and consuming a large amount of precious fuel. This invention condenses and pre-positions the core "trajectory correction" action within the brief period of main engine operation. During this time, utilizing the main engine's high thrust, the thrust direction is changed by adjusting the attitude, efficiently completing trajectory correction. Once the main engine shuts down and the aircraft enters the taxiing phase, it only needs minimal attitude maintenance, significantly reducing the number and duration of attitude control engine operations, saving attitude control fuel. This fuel saving directly translates to a reduction in launch weight (allowing more weight to carry scientific payloads) and a significant decrease in mission costs.

[0015] 2. This invention concentrates correction actions on the active propulsion phase, allowing the attitude control system to remain in standby or low-frequency operation during the taxiing phase, significantly reducing the cumulative operating time and ignition cycle number of the attitude control engine. This directly extends the on-orbit service life of the attitude control system, reduces the probability of mission failure due to attitude control system malfunction, and greatly improves the reliability and robustness of the aircraft in performing long-term or complex missions.

[0016] 3. The introduction of control margin provides a buffer for real-time guidance and control, enhancing robustness in response to emergencies. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a method for optimizing the trajectory of an aircraft based on a fixed-thrust engine, as shown in an embodiment of the present invention. Figure 2 This is a schematic diagram of the flight trajectory shown in an embodiment of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that the defects in the solutions in the prior art are all the results of the inventors' practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed by the embodiments of this application in the following text should be the inventors' contributions to this application in the process of invention and creation, and should not be understood as technical content known to those skilled in the art.

[0020] In one exemplary embodiment, such as Figure 1 As shown, a method for optimizing the trajectory of an aircraft based on a fixed-thrust single-ignition engine as its orbital propulsion is provided, including: S1. Establish the aircraft dynamics model and determine the engine operating parameters; S2. Determine the landing point range and landing point parameters; S3. The activation and deactivation regions that can satisfy the landing range and landing parameters are determined through Monte Carlo simulation, thus obtaining the flight control domain; S4. Develop a guidance strategy for the engine operating phase based on the flight control domain.

[0021] For example, the aircraft dynamics model is as follows: in, Indicates the mass of the aircraft. Indicates the speed of the aircraft; Indicates time; Indicates engine thrust; Indicates the angle of attack; Indicates the trajectory inclination angle; ( x, y () indicates location; This represents the engine's per-second power consumption. The engine's operating parameters are obtained through ground-based vacuum testing, where the relationship between engine thrust P and time is used to solve the equations.

[0022] For example, the landing point range includes the landing point area, and the landing point parameters include landing point speed, landing point angle, and landing point attitude.

[0023] For example, step S3 specifically includes: The boundary trajectory is determined based on the impact point range and the gravitational flight constraints. The engine shutdown point region is determined based on the boundary trajectory (expressed as a function). ) and the boot point region (expressed as a function) ); The boundary area is determined based on the boundary trajectory.

[0024] For example, based on the Monte Carlo simulation envelope, the ballistic optimization strategy is determined as follows: During engine operation, when the aircraft touches the flight constraint domain (i.e., flight control domain) formed by the engine start-up point and shutdown point area, it adjusts the aircraft's flight attitude to ensure that the aircraft is within the shutdown point area constraint range at the moment of shutdown.

[0025] Specifically, the Monte Carlo simulation uses a scatter plot to draw the boundaries of all possible landing points, and then extrapolates these boundaries back to the shutdown and startup points. All simulated landing points are plotted on a map of the target celestial body's surface. These landing points form a scatter plot (a point cloud). This point cloud visually represents all possible landing points of the spacecraft under the influence of all possible errors. Based on the mission-required confidence level (e.g., a 99% landing probability), a region is drawn on this point cloud that encompasses a corresponding proportion of the landing points. This region is the actual, error-considered landing point constraint domain C. It must be less than or equal to the mission-required landing point range.

[0026] From the massive dataset of all simulations, successful samples that ultimately land within the landing point constraint region C are selected. All state data (primarily position and velocity) of these successful samples at the moment of engine shutdown are extracted. This shutdown state data also forms a point cloud (scattered) in the state space. This point cloud defines the set of all shutdown states that could lead to a successful landing. This successful shutdown state point cloud is then enclosed by a mathematically describable region (such as a six-dimensional ellipsoid, or a volume in the three-dimensional position space). This region is the engine shutdown point region.

[0027] Combination Figure 2 In the diagram, number 1 represents the launch coordinate system 0XYZ. The trajectory optimization process is as follows: 1. Establish flight dynamics model equations and determine engine operating parameters (including thrust, operating time, etc.); 2. Based on the requirements of the impact area 7 and the boundary trajectory 6, reverse-engineer the engine start-up area 2, the engine shutdown area 5, and the corresponding parameters; 3. Determine the boundary region based on boundary trajectory 6, with the upper boundary being... The lower boundary is ; 4. Based on the shutdown point region 5 and parameters as constraints, formulate guidance and control requirements for the engine operating phase, constraining flight trajectory 3 within the flight control domain, and forming a trajectory optimization strategy: in, This represents the upper boundary function of the flight control domain. This represents the lower boundary function of the flight control domain. For lower margin, For the sake of margin, Indicates the location of the aircraft.

[0028] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A method for trajectory optimization of a fixed-thrust engine based aircraft, characterized in that, The method comprises the following steps: S1. Establishing an aircraft dynamics model and determining the working parameters of the engine; S2. Determining the landing point range and landing point parameters; S3. Determining the starting point region and the shutdown point region that can satisfy the landing point range and the landing point parameters through Monte Carlo simulation, and obtaining a flight control domain; S4. Formulating a guidance strategy of the engine working section based on the flight control domain.

2. A method of trajectory optimization for a fixed thrust engine based aircraft as recited in claim 1, wherein, The aircraft dynamics model is as follows: wherein, represents the aircraft mass, represents the aircraft velocity; represents time; represents the engine thrust; represents the angle of attack; represents the ballistic angle; x, y represents the position; represents the engine specific consumption.

3. A method of trajectory optimization for a fixed thrust engine based aircraft as recited in claim 1, wherein, The landing point parameters comprise a landing point speed and a landing point angle.

4. A method of trajectory optimization for a fixed thrust engine based aircraft as recited in claim 1, wherein, Step S3 specifically comprises the following steps: Determining a boundary trajectory according to the landing point range and in combination with the gravitational flight constraint; Determining the shutdown point region and the starting point region according to the boundary trajectory; Determining a boundary region according to the boundary trajectory.

5. A method of trajectory optimization for a fixed thrust engine based vehicle according to claim 4, wherein, The guidance strategy of the engine working section formulated based on the flight control domain comprises the following steps: In the engine working stage, when the aircraft touches the flight control domain, the flight attitude of the aircraft is adjusted to ensure that the shutdown moment of the aircraft is within the shutdown point region constraint range.

6. A method of trajectory optimization for a fixed thrust engine based vehicle as claimed in claim 5, wherein, The flight control domain is provided with an upper and lower margin, and the guidance strategy satisfies the following conditions: wherein, represents an upper boundary function of the flight control domain, represents a lower boundary function of the flight control domain, is a lower margin, is an upper margin, represents an aircraft position.

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