A launch vehicle landing adaptive compound attitude control method and control system

Abstract

The application provides a launch vehicle landing adaptive compound attitude control method and a control system. The method estimates the engine thrust according to the throttle ratio instruction of a guidance system, estimates the aerodynamic control ability according to the flight state, adjusts the control gain and instruction adaptively, and determines the switching logic from the aerodynamic control to the RCS control according to the control ability. The application divides the attitude control of the rocket landing stage into two parts, a nominal controller and an adaptive regulator. The nominal controller can not consider the control efficiency change caused by the thrust adjustment in the flight process, and the design difficulty is reduced. Through the online estimation of the control efficiency of the engine, the aerodynamic control and the reaction force RCS, the control gain and the actuator switching are adaptively adjusted, the actual flight state is adapted, and the high-precision attitude control of the rocket landing is realized.

Description

Technical Field

[0001] This invention relates to the field of aerospace launch vehicle technology, and in particular to a launch vehicle landing adaptive composite attitude control method and control system. Background Technology

[0002] Reusable launch vehicles are core equipment for achieving low-cost, high-frequency space access, and their vertical takeoff and landing (VTVL) recovery technology has become a research hotspot in the international aerospace field. During rocket recovery and landing, various attitude control methods are needed, including thrust vector control (changing the thrust direction using a gimbaled engine), aerodynamic control (grid fins or aerodynamic control surfaces), and reaction force (RCS) control, to achieve stability and attitude control of the rocket body. Unlike traditional rockets where attitude control requirements are met by using fixed trajectory and thrust design parameters during the ascent phase, rocket recovery and landing requires continuous thrust adjustment to achieve a soft landing, and the control efficiency of the aerodynamic control surfaces also changes with the flight state.

[0003] Currently, the most widely used engineering approach is for designers to pre-calculate characteristic points at different flight altitudes, speeds, and dynamic pressures based on wind tunnel test data and engine theoretical models, and then design multiple sets of PID control parameters or classical correction network parameters. During flight, the flight control computer uses the flight status obtained from navigation to look up and interpolate the corresponding control parameters. However, this method heavily relies on the accuracy of the offline model and suffers from problems such as sensitivity to aerodynamic deviations and inability to adapt to deep engine throttling.

[0004] Rocket recovery involves multiple control methods, including aerodynamic fins (grid fins), engine sway nozzles (TVC), and reaction force control systems (RCS). Existing technologies typically employ hard-switching logic based on speed or altitude thresholds (e.g., forcibly disabling aerodynamic fin control and activating RCS when the speed falls below a certain value). This open-loop switching method lacks flexibility. On one hand, because it doesn't consider the actual control capabilities at present, premature intervention in RCS before the aerodynamic fin efficiency has fully decayed can lead to propellant waste. Conversely, if the aerodynamic fin has failed (e.g., in the thin atmosphere of high altitudes) and the system fails to switch to RCS or TVC in time, it can result in attitude loss. On the other hand, existing logic usually assumes a constant RCS thrust. However, for widely used cold gas or monocomponent RCS systems, as the gas cylinder pressure decreases or the catalyst bed temperature changes, the output thrust gradually decreases over time. Fixed logic cannot detect this change, leading to insufficient control torque in the roll channel.

[0005] Therefore, there is an urgent need to provide a control method and system that can estimate thrust and aerodynamic control efficiency online and adaptively adjust attitude gain and switch control strategies accordingly. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes an adaptive composite attitude control method and control system for launch vehicle landing. The method estimates engine thrust online based on the engine throttle ratio command from the guidance system and estimates aerodynamic control capability online based on the flight status, thereby adaptively adjusting the control gain and command, and determining the switching logic from aerodynamic control to RCS control based on the control capability.

[0007] This invention provides a method and control system for adaptive composite attitude control of a launch vehicle landing, comprising at least the following steps: S1. Obtain the attitude angle command from the guidance system and the real-time attitude angle from the navigation calculation module, and obtain the attitude deviation signal by comparing the attitude angle command with the real-time attitude angle. S2. Input the attitude deviation signal from step S1 into the nominal controller. The dynamic gain module in the nominal controller receives the angular velocity information of the rocket body output by the navigation calculation module and multiplies it by the dynamic gain as the angular velocity feedback. The attitude deviation signal and the amplified angular velocity feedback are superimposed and then input into the correction network module and the static gain module in sequence, and the nominal control command is output. S3. Input the nominal control command from step S2 into the adaptive regulator. After adaptive gain adjustment and adaptive switching logic processing, output the final control commands for pitch, yaw and roll channels. The final control commands include the equivalent rudder deflection command and switching command for each channel. S4. The final control command is assigned to the actuator, which drives at least one of the following: engine oscillation, grid fin rotation, and RCS switch, thereby changing the control torque and acting on the rocket body to adjust the rocket's motion state. S5, the navigation calculation module senses the changes in rocket dynamics in real time, calculates the new real-time attitude angles, and uses them for a new round of attitude control, forming a closed-loop, cyclic control, and realizing adaptive composite attitude control during rocket landing.

[0008] Furthermore, the adaptive gain adjustment method in step S3 specifically involves calculating the adaptive gain based on the online engine thrust estimation and aerodynamic control efficiency evaluation results. ( 1 indicates a scrolling channel. Indicates a yaw channel. (representing the pitch channel); by combining the nominal control command with adaptive gain Multiply the data in real time to match the open-loop gain fluctuations of the system caused by thrust throttling or dynamic pressure changes, and obtain the corrected final control command.

[0009] Furthermore, the method for online engine thrust estimation specifically involves: during each control cycle of the landing flight process... The flight control computer reads the engine throttle ratio command given by the guidance system. The current thrust is estimated using a second-order difference equation. : ; in, To estimate thrust, For nominal thrust, and For engine thrust response coefficient, This is the throttling ratio instruction.

[0010] Furthermore, the method for evaluating the engine sway control efficiency and aerodynamic control efficiency is as follows: Using estimated thrust Calculate the engine sway control efficiency coefficient based on the current center of mass position: ; ; in, The efficiency coefficient for engine sway control. Indicates a scrolling channel. Indicates a yaw channel. Indicates the pitch channel. The distance from the engine oscillation center to the theoretical apex. The distance from the arrow's center of mass to its theoretical tip. This refers to the number of engine worktables. For the moments of inertia of the roll, yaw, and pitch axes, The distance between the pendulum centers, which is symmetrical about the longitudinal axis of the arrow body and participates in the roll control; pneumatic control efficiency coefficient Calculate as follows: ; in, For dynamic pressure, For aerodynamic reference area, For aerodynamic reference length, The grid rudder aerodynamic moment coefficients for roll, yaw, and pitch.

[0011] Furthermore, the grid rudder aerodynamic torque coefficient The value is obtained by looking up a table or by calculation based on the current Mach number and angle of attack / sideslip angle.

[0012] Furthermore, the adaptive gain is calculated based on the online engine thrust estimation and aerodynamic control efficiency evaluation results. The method is as follows: in, This refers to the combined yaw control coefficient for aerodynamic rudder and engine. This is the nominal engine control efficiency coefficient. This is the nominal aerodynamic control efficiency coefficient. This is the aerodynamic control efficiency coefficient. This is the efficiency coefficient for engine sway control.

[0013] In any of the above embodiments, the adaptive switching logic method in step S3 is specifically as follows: when the aerodynamic control efficiency is detected to have decayed to below a threshold, the switching logic is automatically triggered to generate a switching command; the switching command is specifically as follows: the control authority is transferred from the aerodynamic rudder to the RCS or engine oscillation system to ensure control continuity.

[0014] Furthermore, the adaptive switching logic method in step S3 is specifically as follows: Assuming the rocket uses a single engine, the switching target is the roll channel, and the thrust device is the RCS, the following adaptive switching steps are performed: Estimate the RCS thrust. And based on RCS thrust Calculate the critical value for the pneumatic control capability of the rolling channel. Compare the pneumatic control efficiency of the rolling channel. Critical value of pneumatic control capability of rolling channel ,like Then a switching command is generated: the aerodynamic control rudder and engine are controlled together, and the RCS is turned off; if Then, a switching command is generated: the aerodynamic control surface command is set to zero, the attitude of the roll channel is controlled by the switch of the RCS thrust device, and the attitude of the pitch and yaw channels is controlled by the engine sway.

[0015] Furthermore, the estimated RCS thrust And based on RCS thrust Calculate the critical value for the pneumatic control capability of the rolling channel. The specific method is as follows: If using air conditioning RCS, then by formula: Estimate RCS thrust; Through the formula: Calculate the critical value of the pneumatic control capability of the rolling channel; in, This represents the maximum permissible yaw angle of the grid rudder. The cumulative operating time of the RCS thrust device. , , , All are fitting coefficients; The number of RCS thrust devices participating in unidirectional roll control. This is the rolling control arm of the RCS thrust device.

[0016] Another aspect of the present invention provides an adaptive composite attitude control system for launch vehicle landing, comprising at least: a guidance module, a navigation calculation module, an attitude deviation signal calculation module, a nominal controller, an adaptive regulator, and an actuator; The guidance module is used to provide attitude angle commands; The navigation calculation module is used to sense changes in rocket dynamics in real time and provide real-time attitude angles and real-time flight status information of the rocket. The attitude deviation signal calculation module is used to obtain the attitude angle command and the real-time attitude angle, and calculate the attitude deviation signal based on the attitude angle command and the real-time attitude angle. The nominal controller includes a dynamic gain module, a correction network module, and a static gain module. It is used to receive the angular velocity of the rocket body output by the navigation calculation module and multiply it by the dynamic gain as angular velocity feedback through the dynamic gain module. It also adds the attitude deviation signal and the amplified angular velocity feedback quantity to the correction network module and the static gain module in sequence, and outputs the nominal control command through the static gain module. The adaptive regulator includes adaptive gain adjustment and adaptive switching logic, which are used to receive nominal control commands, process them through the adaptive gain adjustment and adaptive switching logic, and output the final control commands for pitch, yaw and roll channels, and distribute the final control commands to the actuators. An actuator is used to drive at least one of the following: engine oscillation, grid fin rotation, and RCS switch, thereby changing the control torque and acting on the rocket body to regulate the rocket's motion state.

[0017] The adaptive composite attitude control method and control system for launch vehicle landing of the present invention effectively solves the control problems faced by launch vehicles in the vertical landing phase, such as strong nonlinearity, time-varying nature, and coupling of multiple actuators, through a composite control architecture that combines nominal control and adaptive adjustment. It has at least one of the following beneficial effects: I. This invention decouples the controller into a two-layer architecture: a nominal controller and an adaptive regulator. Designers only need to design the control law for the nominal trajectory point, eliminating the need for tedious parameter scheduling (gain scheduling) for thousands of complex thrust-dynamic pressure combinations during the offline phase. The adaptive regulator, as the core dynamic compensation unit, extracts navigation and guidance command information in real time and performs gain corrections to address the drastic changes in engine thrust depth throttling and aerodynamic characteristics during landing. This not only greatly simplifies the complexity of offline parameter design and shortens the development cycle but also avoids control risks caused by insufficient coverage of offline design points, significantly improving the ease of engineering implementation.

[0018] II. This invention estimates the actual thrust of the engine online. and aerodynamic efficiency Furthermore, the system uses an adaptive regulator to compensate in real time for control torque deviations caused by engine depth throttling and drastic changes in dynamic pressure. This ensures that the actual open-loop gain of the system remains near the nominal design point throughout the landing process, effectively suppressing low-frequency oscillations or dynamic response divergence caused by gain mismatch, and ensuring attitude stability throughout the landing process.

[0019] Third, this invention establishes switching criteria based on real-time control capability assessment (rather than simple velocity / altitude thresholds). As the aerodynamic control efficiency of the roll channel gradually decreases, a seamless transition from aerodynamic control to reaction force control is achieved through online estimation and adaptive intervention of RCS thrust. This "flexible switching" mechanism eliminates the angular velocity disturbances that may occur during the switching transient in traditional hard switching logic, improving the attitude pointing accuracy of the rocket in the critical period before touchdown.

[0020] Fourth, this invention can assess the "control torque capability" of each actuator in real time, and the system can prioritize the actuator with the highest efficiency to perform control tasks. This efficient resource allocation reduces unnecessary RCS propellant consumption and leaves more control capability for precise landing in the final stage, thereby significantly improving the accuracy of the rocket's vertical landing and the success rate of soft landing.

[0021] Upon reading the detailed embodiments and examining the accompanying drawings, those skilled in the art will recognize additional features and advantages. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating the adaptive composite attitude control method for launch vehicle landing according to an embodiment of the present invention.

[0024] Figure 2 This is a logic block diagram of the adaptive composite attitude control for launch vehicle landing according to an embodiment of the present invention. Detailed Implementation

[0025] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and to exemplify the principles of the present invention, and are not configured to limit the present invention. In addition, the structural components in the drawings are not necessarily drawn to scale. For example, the dimensions of some structural components or regions in the drawings may be enlarged for other structural components or regions to aid in the understanding of the embodiments of the present invention.

[0026] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of the embodiments of the present invention. In the description of the present invention, it should be noted that, unless otherwise stated, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0027] Furthermore, the terms "comprising," "including," "having," or any other variations thereof are intended to cover non-exclusive inclusion, such that a structure or component that includes a list of elements includes not only those elements but also other structural elements that are not expressly listed or inherent to the structure or component. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the article or apparatus that includes the element.

[0028] Spatial relation terms such as "below," "under," "under," "low," "above," "on," and "high" are used for descriptive convenience to explain the positioning of one element relative to a second element, indicating that these terms are intended to cover different orientations of the device, in addition to those different from those shown in the figure. Furthermore, phrases such as "one element on / below another element" can indicate that two elements are in direct contact, or that there are other elements between the two elements. In addition, terms such as "first" and "second" are also used to describe individual elements, areas, parts, etc., and should not be considered limiting. Similar terms are used throughout the description to refer to similar elements.

[0029] It will be apparent to those skilled in the art that the present invention can be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention.

[0030] This invention takes a certain type of vertical recovery launch vehicle as an example. The rocket is equipped with a variable thrust liquid engine (with swaying capability), aerodynamic grid fins, and an RCS attitude control system.

[0031] See Figure 1 This invention provides an adaptive composite attitude control method for launch vehicle landing, comprising at least the following steps: S1. Obtain the attitude angle command from the guidance system and the real-time attitude angle from the navigation calculation module, and obtain the attitude deviation signal by comparing the attitude angle command with the real-time attitude angle. S2. Input the attitude deviation signal from step S1 into the nominal controller. The dynamic gain module in the nominal controller receives the angular velocity information of the rocket body output by the navigation calculation module and multiplies it by the dynamic gain as the angular velocity feedback. The attitude deviation signal and the amplified angular velocity feedback are superimposed and then input into the correction network module and the static gain module in sequence, and the nominal control command is output. S3. Input the nominal control command from step S2 into the adaptive regulator. After adaptive gain adjustment and adaptive switching logic processing, output the final control commands for pitch, yaw and roll channels. The final control commands include the equivalent rudder deflection command and switching command for each channel. S4. Distribute the final control command to the actuator, and drive at least one of the following through the actuator: engine oscillation, grid fin rotation, and RCS switch, thereby changing the control torque and acting on the rocket body to adjust the rocket's motion state. S5, the navigation calculation module senses the changes in rocket dynamics in real time, calculates the new real-time attitude angles, and uses them for a new round of attitude control, forming a closed-loop, cyclic control, and realizing adaptive composite attitude control during rocket landing.

[0032] In this embodiment, the actuator is an engine servo mechanism, a pneumatic servo mechanism, or an RCS solenoid valve.

[0033] Combination Figure 2 The adaptive composite attitude control method for launch vehicle landing in this embodiment employs an attitude controller comprising a nominal controller and an adaptive regulator. The nominal controller is designed according to the nominal trajectory corresponding to the nominal thrust and aerodynamic control capabilities (refer to *Control Systems (Volume 1)*, China Aerospace Publishing House, edited by Xu Yanwan, 1989), therefore, the nominal controller portion will not be described in detail here. The adaptive regulator serves as the core dynamic compensation unit, extracting navigation and guidance command information in real time and performing gain corrections to address the drastic changes in engine thrust depth throttling and aerodynamic characteristics during landing.

[0034] In this embodiment, the navigation calculation module processes sensor data to provide closed-loop feedback (real-time attitude angle) to the input end, and provides the angular velocity of the rocket body to the dynamic gain module of the nominal controller; at the same time, it transmits the real-time flight status (such as Mach number, dynamic pressure, etc.) calculated by the module to the adaptive regulator as the basis for parameter adjustment.

[0035] The nominal controller is responsible for the basic control logic design and consists of three core parts: dynamic gain, correction network, and static gain. The dynamic gain module uses the angular velocity of the rocket body provided by the navigation calculation module, multiplied by the dynamic gain, as closed-loop feedback. The correction network module employs frequency domain or time domain design methods (such as lead-lag correction) to filter and compensate the attitude deviation and the amplified angular velocity feedback signal, ensuring the stability of the system's dynamic response characteristics. The static gain module corresponds to the basic amplification factor under the nominal trajectory, providing a stable command output reference and outputting the nominal control commands.

[0036] The adaptive regulator in step 3 is the core component of the adaptive composite attitude control method for launch vehicle landing of the present invention. It includes two parts: adaptive gain and adaptive switching, which are used to correct the nominal control command to adapt to the changes in actual thrust and rudder effect.

[0037] First, the adaptive gain is calculated based on the online engine thrust estimation and aerodynamic control efficiency evaluation results according to the technical solution of this invention. By combining the nominal control command with this adaptive gain Multiplication (where subscripts are used) Different values ​​represent different channels), real-time matching of system open-loop gain fluctuations caused by thrust throttling or dynamic pressure changes. 1 indicates a scrolling channel. Indicates a yaw channel. Indicates the pitch channel.

[0038] Specifically, in one embodiment, the adaptive gain adjustment method in step S3 is as follows: calculating the adaptive gain based on the online engine thrust estimation and aerodynamic control efficiency evaluation results. By combining the nominal control command with adaptive gain Multiply the data in real time to match the open-loop gain fluctuations of the system caused by thrust throttling or dynamic pressure changes, and obtain the corrected total control command.

[0039] Furthermore, to effectively reconstruct the engine's dynamic response and make subsequent torque calculations closer to the true value, the specific method for online engine thrust estimation is as follows: during each control cycle of the landing flight process... (For example, 20ms), the flight control computer reads the engine throttle ratio command given by the guidance system. The current thrust is estimated using the following second-order difference equation. : ; in, To estimate thrust, For nominal thrust, and This is the engine thrust response coefficient. This is a throttling ratio command. In this embodiment... and It was obtained by fitting engine test data.

[0040] This embodiment addresses the physical delay and response inertia inherent in liquid rocket engines during deep throttling. Instead of simply transmitting guidance commands, this innovative approach introduces an online thrust estimation method based on high-order difference equations. This is achieved by establishing, for example: The configuration incorporates the step response characteristics obtained from engine testing into real-time calculations. This improvement significantly enhances the control system's perception accuracy of "real physical thrust," effectively resolving the phase difference between control commands and actual torque caused by thrust adjustment lag, thereby eliminating the common low-frequency attitude oscillation hazards during landing.

[0041] Furthermore, the specific methods for evaluating engine sway control efficiency and aerodynamic control efficiency are as follows: Using estimated thrust Given the current center of mass position (which varies with fuel consumption), calculate the engine sway control efficiency coefficient using the following equation: in, Engine sway control efficiency coefficient (subscript) (different values ​​represent different channels), where, Indicates a scrolling channel. Indicates a yaw channel. Indicates the pitch channel. The distance from the engine oscillation center to the theoretical apex. The distance from the arrow's center of mass to its theoretical tip. This refers to the number of engine worktables. For the moments of inertia of the roll, yaw, and pitch axes (subscript) Different values ​​represent different channels. The distance between the pendulum centers is symmetrical about the longitudinal axis of the arrow body and is involved in the roll control.

[0042] The aerodynamic control efficiency coefficient is calculated using the following formula. : ; in, For dynamic pressure, For aerodynamic reference area, For aerodynamic reference length, This represents the grid rudder aerodynamic moment coefficient for the corresponding channel (pitch, yaw, roll).

[0043] In this embodiment, the grid rudder aerodynamic torque coefficient The value is obtained by looking up a table or by calculation based on the current Mach number and angle of attack / sideslip angle.

[0044] For example, In the formula, The fitting parameters for aerodynamic control efficiency are obtained by fitting the aerodynamic characteristics at different Mach numbers, and are loaded into the flight control computer as parameters for interpolation at different Mach numbers.

[0045] Considering the grid rudder aerodynamic moment coefficient To address the issues of drastic Mach number variations and potential local distortions in polynomial fitting, this invention employs a radial basis function (RBF) neural network for online compensation. Specifically, using the nominal polynomial model as the baseline output, the attitude tracking error is used as the driver for updating neuron weights, enabling online learning and compensation for torque deviations caused by transonic center-of-pressure drift or aerodynamic disturbances of the control surfaces. Because the RBF network possesses global approximation characteristics and low computational overhead, it can effectively compensate for the differences between wind tunnel test data and actual flight environments, allowing the adaptive controller to maintain its nominal design performance even under extremely complex aerodynamic conditions, thus enhancing the algorithm's intelligence.

[0046] Furthermore, to counteract the effects of thrust and aerodynamic variations, an adaptive gain is calculated, reflecting the ratio of "current capability" to "nominal capability." Specifically, the adaptive gain is calculated based on online engine thrust estimation and aerodynamic control efficiency evaluation results. ( 1 indicates a scrolling channel. Indicates a yaw channel. The method for representing the pitch channel is as follows: in, This refers to the combined yaw control coefficient for aerodynamic rudder and engine. For engine control efficiency coefficient, This is the aerodynamic control efficiency coefficient. The nominal engine sway control efficiency coefficient. This is the nominal aerodynamic control efficiency coefficient. In this embodiment... During offline design, the parameters are acquired and bound to the flight control computer. The flight control computer then multiplies the output of the nominal PID controller by this gain. The corrected master control command is then obtained.

[0047] The adaptive gain matching algorithm implemented in this paper dynamically scales the nominal control command by comparing the difference between the "current actual capability" and the "nominal design capability" in real time. Its physical essence is to achieve constant open-loop gain of the closed-loop system throughout the entire flight envelope. Whether under extreme conditions such as low engine thrust operation or reduced aerodynamic control effect, it can ensure that the phase margin and amplitude margin of the control loop meet the design requirements, which greatly improves the high-precision tracking performance of attitude control.

[0048] In this embodiment, Usually taken as: in, This represents the maximum permissible angle of aerodynamic control surface sway. This represents the maximum permissible angle of engine sway. This embodiment introduces a joint control coefficient. It achieves normalization of the performance of actuators in different physical dimensions.

[0049] Secondly, the adaptive switching module is responsible for the logical allocation between actuators. When the aerodynamic control efficiency is detected to have decayed below the threshold, the adaptive switching module automatically triggers the switching logic to transfer the control authority from the aerodynamic rudder to the RCS or engine sway system, ensuring control continuity.

[0050] In any of the above embodiments, the adaptive switching logic method in step S3 specifically involves: when the aerodynamic control efficiency is detected to have decayed below a threshold, automatically triggering the switching logic and generating a switching command. This switching command specifically transfers control authority from the aerodynamic rudder to the RCS or engine oscillation system to ensure control continuity.

[0051] It should be noted that, due to the low velocity at the end of rocket landing, the roll control capability of the aerodynamic rudder decays most rapidly. Therefore, this embodiment focuses on the switching of the roll channel. Secondly, there are significant differences in landing control between single-launch and multi-launch rockets, and between chemical reaction-type thrusters and drop-pressure cold gas-type thrusters.

[0052] Assuming the rocket uses a single engine, the switching target is the roll channel, and the control device is a cold gas RCS, a chemical reaction RCS, or an aerodynamic control fin, given that the engine does not have roll control capability when using a single engine for landing control, the following adaptive switching steps can be executed: Estimating RCS thrust And based on RCS thrust Calculate the critical value for the pneumatic control capability of the rolling channel. Compare the pneumatic control efficiency of the rolling channel. Critical value of pneumatic control capability of rolling channel ,like Then a switching command is generated: the aerodynamic control rudder and engine are controlled together, and the RCS is turned off; if Then, a switching command is generated: the aerodynamic control surface command is set to zero, the attitude of the roll channel is controlled by the switch of the RCS thrust device, and the attitude of the pitch and yaw channels is controlled by the engine sway.

[0053] In this embodiment, it is assumed that the rocket uses multiple engines, and that other assumptions remain unchanged, the engines have roll control capability. If Then a switching command is generated: the aerodynamic control surface command is set to zero, and the attitude control of pitch, yaw, and roll channels is performed by engine oscillation.

[0054] Furthermore, estimate the RCS thrust. And based on RCS thrust Calculate the critical value for the pneumatic control capability of the rolling channel. The specific method is as follows: For the RCS of air conditioning, the formula is: Alternatively, a simplified polynomial form can be used: Estimate the RCS thrust. In the formula... Determined based on offline fitting of thrust device characteristics.

[0055] For chemical reaction type RCS, Its rated thrust can be directly taken.

[0056] Through the formula: Calculate the critical value for the pneumatic control capability of the rolling channel. Among them, This represents the maximum permissible yaw angle of the grid rudder. The cumulative operating time of the RCS thrust device. , , , All are fitting coefficients. The number of RCS thrust devices participating in unidirectional roll control. This is the rolling control arm of the RCS thrust device.

[0057] when At this time (usually at high speeds), the aerodynamic rudder is efficient enough. At this time, combined control is used, that is, the aerodynamic rudder and the engine (if roll capability is available) work together, and the RCS is turned off to save fuel.

[0058] when At this time (usually at low speed or at the end of landing), the efficiency of aerodynamic rudder control is so low that it can be ignored. At this time, it is necessary to make appropriate adjustments according to the number of rocket engines, so as to achieve a smooth transition of the rocket from a high dynamic pressure and high thrust state to a low dynamic pressure and variable thrust state, ensuring that the landing accuracy meets expectations.

[0059] To address the technical challenge of rapidly decreasing aerodynamic control effectiveness at the rocket's landing terminal phase, this embodiment proposes a flexible switching mechanism based on real-time control performance evaluation (rather than simple hard thresholds for speed or altitude). The system calculates the critical criteria between the aerodynamic control capability of the roll channel and the RCS (or multi-engine differential sway) control capability in real time. The system autonomously determines the timing of the transfer of control. This switching logic fully considers the real-time health status of the actuators and environmental disturbances, effectively avoiding the angular velocity jumps and attitude instability that may be caused near the critical point by traditional hard switching logic, and achieving a highly reliable and smooth transfer of control of the rocket from the aerodynamic deceleration phase to the powered descent phase.

[0060] Furthermore, those skilled in the art should understand that before rocket launch, the following parameters related to the recovery and landing mission and navigation calculations need to be pre-programmed into the flight control computer as reference data for real-time attitude control during the recovery process. Specifically, before rocket launch, the following parameters (the definitions of each parameter are given above and will not be repeated here) are pre-programmed into the flight control computer: Engine thrust response model coefficients ; Nominal thrust and nominal control efficiency coefficient table ; Aerodynamic coefficient fitting parameters (For different Mach number ranges); Arrow body geometric and mass characteristics parameters: ; RCS thrust attenuation fitting coefficient ( or (Series parameters).

[0061] This invention breaks through the deadlock of traditional rocket attitude control's over-reliance on large-scale offline gain scheduling, and innovatively proposes a design method that decouples the controller into a two-layer architecture: a nominal controller and an adaptive regulator. The nominal controller only needs to perform basic robustness design for preset nominal operating conditions, ensuring the system's stability benchmark under standard conditions. The adaptive regulator, as the core dynamic compensation unit, extracts navigation and guidance command information in real time and performs gain correction for the drastic changes in engine thrust depth throttling and aerodynamic characteristics during landing. This architecture design not only greatly simplifies the complexity of offline parameter design and shortens the development cycle, but more importantly, through functional decoupling, enables the control algorithm to smoothly cope with the complex envelope of alternating variable thrust and variable pressure, providing robust architectural support for the rocket's attitude stability during vertical recovery.

[0062] This invention proposes a complete online evaluation system for control effectiveness, encompassing engine sway, aerodynamic grid rudder, and RCS nozzle. For the aerodynamic end, a polynomial fitting model dynamically corrected with Mach number, angle of attack, and sideslip angle is used to accurately capture the impact of transonic pressure center drift on rudder effectiveness. For the RCS end, a thrust prediction model considering pressure decay in a drop-pressure system is established, with thrust estimates updated in real time through accumulated operating time. This refined modeling method enables the control system to grasp the "true torque boundaries" of each actuator in real time, avoiding control failures caused by hardware physical performance degradation (such as RCS thrust decay) or drastic environmental changes (such as sudden decrease in dynamic pressure), laying a precise mathematical foundation for multi-mechanism collaborative control.

[0063] The above embodiments can be combined with each other and have corresponding technical effects.

[0064] Another aspect of the present invention provides a launch vehicle landing adaptive composite attitude control system for implementing the launch vehicle landing adaptive composite attitude control method in any of the above embodiments. The landing adaptive composite attitude control system of the present invention includes at least: a guidance module, a navigation calculation module, an attitude deviation signal calculation module, a nominal controller, an adaptive regulator, and an actuator. The guidance module provides attitude angle commands. The navigation calculation module senses changes in rocket dynamics in real time and provides real-time attitude angles and real-time flight status information of the rocket. The attitude deviation signal calculation module acquires the attitude angle commands and real-time attitude angles, and calculates the attitude deviation signal based on the attitude angle commands and real-time attitude angles. The nominal controller includes a dynamic gain module, a correction network module, and a static gain module. It receives the rocket angular velocity output by the navigation calculation module multiplied by the dynamic gain as an angular velocity feedback quantity through the dynamic gain module, and then superimposes the attitude deviation signal and the amplified angular velocity feedback quantity, sequentially inputting them into the correction network module and the static gain module. The static gain module outputs the nominal control command. The adaptive regulator includes adaptive gain adjustment and adaptive switching logic. It receives nominal control commands and, after processing by the adaptive gain adjustment and adaptive switching logic, outputs final control commands for pitch, yaw, and roll channels to the actuators. These final control commands are then distributed to the actuators, which are either servo mechanisms or RCS solenoid valves. The actuators drive at least one of three actions: engine oscillation, grid fin rotation, and RCS switching, thereby changing the control torque and acting on the rocket body to adjust the rocket's motion state.

[0065] The actuator in this embodiment integrates three types of physical actuation systems. The engine servo controls the thrust vector control (TVC) oscillation, providing pitch, yaw, and roll control torques. The grid rudder servo provides three-channel control torques through aerodynamic surface deflection in the high dynamic pressure phase. The RCS (Reaction Force Control System) provides auxiliary torques in the low dynamic pressure or terminal landing phase, particularly addressing roll control issues in single-engine mode.

[0066] Given that the adaptive composite attitude control method for launch vehicle landing provided by this invention can evaluate the "control torque capability" of each actuator in real time, the system can prioritize the actuator with the highest efficiency to perform control tasks. This efficient resource allocation reduces unnecessary RCS propellant consumption and leaves more control capability for precise landing in the final stage, thereby significantly improving the accuracy of vertical landing and the success rate of soft landing.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for adaptive composite attitude control of a launch vehicle landing, characterized in that, At least the following steps are included: S1. Obtain the attitude angle command from the guidance system and the real-time attitude angle from the navigation calculation module, and obtain the attitude deviation signal by comparing the attitude angle command with the real-time attitude angle. S2. Input the attitude deviation signal from step S1 into the nominal controller. The dynamic gain module in the nominal controller receives the angular velocity information of the rocket body output by the navigation calculation module and multiplies it by the dynamic gain as the angular velocity feedback. The attitude deviation signal and the amplified angular velocity feedback are superimposed and then input into the correction network module and the static gain module in sequence, and the nominal control command is output. S3. Input the nominal control command from step S2 into the adaptive regulator. After adaptive gain adjustment and adaptive switching logic processing, output the final control commands for pitch, yaw and roll channels. The final control commands include the equivalent rudder deflection command and switching command for each channel. S4. Distribute the final control command to the actuator, and drive at least one of the following through the actuator: engine oscillation, grid fin rotation, and RCS switch, thereby changing the control torque and acting on the rocket body to adjust the rocket's motion state. S5, the navigation calculation module senses the changes in rocket dynamics in real time, calculates the new real-time attitude angles, and uses them for a new round of attitude control, forming a closed-loop, cyclic control, and realizing adaptive composite attitude control during rocket landing.

2. The adaptive composite attitude control method for launch vehicle landing according to claim 1, characterized in that, The adaptive gain adjustment method in step S3 is as follows: Adaptive gain is calculated based on online engine thrust estimation, engine sway control efficiency, and aerodynamic control efficiency evaluation results. , Indicates a deviating channel. Indicates the pitch channel; By combining the nominal control command with adaptive gain Multiply the data in real time to match the open-loop gain fluctuations of the system caused by thrust throttling or dynamic pressure changes, and obtain the corrected total control command.

3. The adaptive composite attitude control method for launch vehicle landing according to claim 2, characterized in that, The method for online estimation of engine thrust is as follows: Each control cycle during landing flight The flight control computer reads the engine throttle ratio command given by the guidance system. The current thrust is estimated using a second-order difference equation. : ； in, To estimate thrust, For nominal thrust, and For engine thrust response coefficient, This is the throttling ratio instruction.

4. The adaptive composite attitude control method for launch vehicle landing according to claim 3, characterized in that, The specific methods for evaluating the engine sway control efficiency and the aerodynamic control efficiency are as follows: Using estimated thrust Calculate the engine sway control efficiency coefficient based on the current center of mass position: in, The efficiency coefficient for engine sway control. Indicates a scrolling channel. Indicates a deviating channel. Indicates the pitch channel. The distance from the engine oscillation center to the theoretical apex. The distance from the arrow's center of mass to its theoretical tip. This refers to the number of engine worktables. For the moments of inertia of the roll, yaw, and pitch axes, The distance between the pendulum centers, which is symmetrical about the longitudinal axis of the arrow body and participates in the roll control; The aerodynamic control efficiency coefficient is calculated using the following formula. : in, For dynamic pressure, For aerodynamic reference area, For aerodynamic reference length, The grid rudder aerodynamic moment coefficients for roll, yaw, and pitch.

5. The adaptive composite attitude control method for launch vehicle landing according to claim 4, characterized in that, Grid rudder aerodynamic moment coefficient The value is obtained by looking up a table or by calculation based on the current Mach number and angle of attack / sideslip angle.

6. The adaptive composite attitude control method for launch vehicle landing according to claim 4, characterized in that, The adaptive gain is calculated based on the online engine thrust estimation, engine sway control efficiency, and aerodynamic control efficiency evaluation results. The method is as follows: in, This refers to the combined yaw control coefficient for aerodynamic rudder and engine. The nominal engine sway control efficiency coefficient. This is the nominal aerodynamic control efficiency coefficient. This is the aerodynamic control efficiency coefficient. This is the efficiency coefficient for engine sway control.

7. The adaptive composite attitude control method for launch vehicle landing according to any one of claims 1 to 6, characterized in that, The adaptive switching logic method in step S3 is as follows: when the pneumatic control efficiency is detected to have decayed to below the threshold, the switching logic is automatically triggered and a switching command is generated. The switching command specifically involves transferring control authority from the aerodynamic rudder to the RCS or engine oscillation system to ensure control continuity.

8. The adaptive composite attitude control method for launch vehicle landing according to claim 6, characterized in that, The adaptive switching logic method in step S3 is specifically as follows: Assuming the rocket uses a single engine, the switching target is the roll channel, and the thrust device is the RCS, the following adaptive switching steps are performed: Estimating RCS thrust And based on RCS thrust Calculate the critical value for the pneumatic control capability of the rolling channel. ; Compare the pneumatic control efficiency of the rolling channel Critical value of pneumatic control capability of rolling channel ,like Then a switching command is generated: the aerodynamic control rudder and engine are controlled together, and the RCS is turned off; if Then, a switching command is generated: the aerodynamic control surface command is set to zero, the attitude of the roll channel is controlled by the switch of the RCS thrust device, and the attitude of the pitch and yaw channels is controlled by the engine sway.

9. The adaptive composite attitude control method for launch vehicle landing according to claim 8, characterized in that, The estimated RCS thrust And based on RCS thrust Calculate the critical value for the pneumatic control capability of the rolling channel. The specific method is as follows: If using air conditioning RCS, then by formula: Estimate RCS thrust; By formula: Calculate the critical value of the pneumatic control capability of the rolling channel; in, This represents the maximum permissible yaw angle of the grid rudder. The cumulative operating time of the RCS thrust device. , , , All are fitting coefficients; The number of RCS thrust devices participating in unidirectional roll control. This is the rolling control arm of the RCS thrust device.

10. A launch vehicle landing adaptive composite attitude control system, used to implement the launch vehicle landing adaptive composite attitude control method according to any one of claims 1 to 9, characterized in that, At least including: The guidance module is used to provide attitude angle commands; The navigation calculation module is used to sense changes in rocket dynamics in real time and provide real-time attitude angles and real-time flight status information of the rocket. The attitude deviation signal calculation module is used to acquire the attitude angle command and the real-time attitude angle, and calculate the attitude deviation signal based on the attitude angle command and the real-time attitude angle. The nominal controller includes a dynamic gain module, a correction network module, and a static gain module. It is used to receive the angular velocity of the rocket body output by the navigation calculation module and multiply it by the dynamic gain as angular velocity feedback through the dynamic gain module. It also adds the attitude deviation signal and the amplified angular velocity feedback quantity to the correction network module and the static gain module in sequence, and outputs the nominal control command through the static gain module. An adaptive regulator, including adaptive gain adjustment and adaptive switching logic, is used to receive nominal control commands, process them through the adaptive gain adjustment and adaptive switching logic, output final control commands for pitch, yaw and roll channels, and distribute the final control commands to the actuators. An actuator is used to drive at least one of the following: engine oscillation, grid fin rotation, and RCS switch, thereby changing the control torque and acting on the rocket body to regulate the rocket's motion state.

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