Triangular wing unmanned aerial vehicle landing method and system for coping with ground effect nonlinear interference

Abstract

This invention relates to the field of unmanned aerial vehicle (UAV) control technology, proposing a landing method and system for delta-wing UAVs to cope with ground effect nonlinear interference. The method includes: using acquired flight status and sensor data, and based on a spatial gradient dynamic residual verification mechanism, determining whether the UAV has entered a strong ground effect zone; if it has, cutting off the altitude closed-loop feedback loop and smoothly switching to the attitude impedance holding mode; in the attitude impedance holding mode, constructing a second-order impedance dynamic model of the UAV's pitch axis, generating compensating rudder deflection commands to absorb ground effect disturbance torque; during deceleration and landing, running a total energy control system algorithm, monitoring the specific total energy decay rate in real time and predicting the takeoff distance, and performing go-around redundancy protection determination; monitoring the main landing gear load sensor in real time, and triggering a feedforward control strategy to actively unload residual aerodynamic lift and complete landing at the moment of confirmed ground contact. This invention solves the problems of high-frequency oscillations in flight control and extended drift distance caused by ground effect.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) control technology, and in particular to a landing method and system for delta-wing UAVs to cope with ground effect nonlinear interference. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] With the development of UAV technology, high-sweep delta-wing turbofan UAVs are widely used due to their excellent high-speed flight performance and aerodynamic characteristics. However, they are susceptible to significant near-ground aerodynamic interference during low-speed approach and landing. When approaching the runway, the flow field between the lower surface of the wing and the ground is compressed, and the downward diffusion of the downwash airflow is hindered, forming a strong ground effect. This results in a significant reduction in induced drag, an increase in the effective angle of attack, and the generation of a strong air cushion lift force.

[0004] Current research largely focuses on the macroscopic performance parameters of traditional wing-mounted / back-mounted commercial aircraft or hovering aircraft, lacking insights into the evolution of unsteady flow fields and disturbance control schemes for high-speed delta wings under ground effect. In actual landings, strong ground effect nonlinear disturbances can easily lead to prolonged drift distances and high-frequency oscillations in the longitudinal trajectory.

[0005] Conventional aircraft landing control schemes have the following technical limitations when dealing with the autonomous landing of turbofan delta-wing UAVs: existing landing systems mostly adopt continuous altitude error closed-loop feedback control, which is prone to inducing near-ground trajectory oscillations; in traditional landing logic, thrust control and pitch trajectory control are mostly independently decoupled designs, which can easily lead to insufficient kinetic energy decay; most existing landing control laws only maintain a fixed pitch attitude during the level float touchdown phase, relying on the wheels to naturally touch down and decelerate, and the passive touchdown mode is prone to landing bounce and structural impact. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a landing method and system for delta-wing UAVs to cope with ground effect nonlinear interference, solving the problems of high-frequency oscillations in flight control and extended drift distance caused by ground effect.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: The first aspect of this invention provides a landing method for a delta-wing unmanned aerial vehicle (UAV) to cope with ground effect nonlinear interference, comprising: Using the acquired flight status and sensor data, and based on the spatial gradient dynamic residual verification mechanism, it is determined whether the UAV has entered the strong ground effect zone; If it is determined that the strong ground effect zone has been entered, the altitude closed-loop feedback loop is cut off and the attitude impedance holding mode is smoothly switched; Under the attitude impedance holding mode, a second-order impedance dynamic model of the UAV pitch axis is constructed to generate a compensating rudder deflection command to absorb ground effect disturbance torque. During the deceleration and settling process, the total energy control system algorithm is run to monitor the specific total energy attenuation rate in real time and predict the takeoff distance, and to make a judgment on the redundancy protection for the go-around. The system monitors the main landing gear load sensors in real time and triggers a feedforward control strategy to actively unload residual aerodynamic lift and complete the landing the moment the ground contact is confirmed.

[0008] As a further technical solution, the judgment verification inequality of the spatial gradient dynamic residual verification mechanism is as follows:

[0009] In the formula, The differential symbol; This is the measured value of the vertical acceleration of the entire machine; This represents the theoretically expected increment of vertical acceleration. This indicates the real-time altitude above the ground. This is the preset dynamic residual safety isolation threshold. The system determines that the UAV has entered the strong ground effect zone if and only if the above verification inequality holds true continuously within the preset confidence time window.

[0010] As a further technical solution, the composite transition control law for the smooth switching to the attitude impedance holding mode is as follows:

[0011] In the formula, To control the elevator deflection command ultimately output by the flight control system within the handover time window; The time-smoothing decay weighting factor is used in the interval Internal continuous monotonically decreasing; To truncate the actual elevator deflection constant latched at the trigger moment; The impedance control output command is used for the impedance maintenance mode calculation after the switch. This is the initial switching moment that is confirmed to be triggered in the subsurface area; The preset control handover time window length.

[0012] As a further technical solution, the pitch rotation impedance equation of the second-order impedance dynamic model of the UAV pitch axis is defined as:

[0013] In the formula, For pitch inertia; To lock onto the desired high angle of attack for landing; and These are the real-time pitch angle and pitch rate, respectively. For external ground effect aerodynamic disturbance torque; For dynamic virtual stiffness; For dynamic virtual damping; Dynamic virtual stiffness and dynamic virtual damping follow the following dynamic adaptive scheduling law:

[0014]

[0015] In the formula, For dynamic virtual stiffness, For dynamic virtual damping, The nominal reference stiffness is set; The initial reference velocity at the moment of entry into the subsurface zone; Instantaneous airspeed; Damping ratio constraints set for the system.

[0016] As a further technical solution, the total energy control system algorithm calculates the specific rate of change of total energy as follows:

[0017] In the formula, This represents the instantaneous rate of change of total energy. This refers to the instantaneous thrust of the engine. The instantaneous aerodynamic drag of the entire aircraft; Instantaneous airspeed; For drone quality; This is the acceleration due to gravity.

[0018] As a further technical solution, the triggering condition for the re-flight redundancy protection determination is: and

[0019] In the formula, It is the absolute value of the total energy decay rate; This is the preset minimum safety ratio total energy decay rate threshold value; This represents the remaining runway length. For integration variables; This is the current determination time; This is the basic stabilization point predicted in advance; This refers to the predicted skid braking distance.

[0020] As a further technical solution, the feedforward control strategy includes: Within the high-dynamic control cycle time window confirming ground contact, the system outputs a step-type full-deflection stick command, coordinating with the deflection of the wing's auxiliary aerodynamic deceleration surfaces; thus increasing the overall dynamic lift coefficient of the aircraft. A significant nonlinear decrease occurs, satisfying the following aerodynamic characteristic relationship:

[0021] In the formula, This refers to the overall dynamic lift coefficient of the aircraft. It is a time variable; This is a preset positive lower bound parameter for the lift coefficient attenuation rate.

[0022] A second aspect of the present invention provides a delta-wing unmanned aerial vehicle (UAV) landing system for coping with ground effect nonlinear interference, comprising: The ground effect perception and triggering module is configured to: use the acquired flight status and sensor data, based on the spatial gradient dynamic residual verification mechanism, to determine whether the UAV has entered a strong ground effect zone; The closed-loop cutoff and switching module is configured to: if it is determined that the strong ground effect zone has been entered, cut off the height closed-loop feedback loop and smoothly switch to the attitude impedance holding mode; The energy monitoring and go-around module is configured to: construct a second-order impedance dynamic model of the UAV pitch axis under the attitude impedance holding mode, and generate compensation rudder deflection commands to absorb ground effect disturbance torque; The impedance disturbance rejection control module is configured to: run the total energy control system algorithm during deceleration and settlement, monitor the specific total energy attenuation rate in real time and predict the takeoff distance, and make a judgment on the redundancy protection for go-around. The feedforward unloading and anti-bounce module is configured to: monitor the main landing gear load sensor in real time, and trigger the feedforward control strategy to actively unload the residual aerodynamic lift and complete the landing at the moment of confirmation of ground contact.

[0023] A third aspect of the present invention provides a computer-readable storage medium having a program stored thereon that, when executed by a processor, implements the steps in the landing method for a delta-wing unmanned aerial vehicle for responding to ground effect nonlinear interference as described in the first aspect of the present invention.

[0024] The fourth aspect of the present invention provides an electronic device including a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the landing method for a delta-wing unmanned aerial vehicle for dealing with ground effect nonlinear interference as described in the first aspect of the present invention.

[0025] The above one or more technical solutions have the following beneficial effects: This invention addresses the limitations of near-ground altitude sensors, which are susceptible to interference from low-altitude atmospheric turbulence and white noise. It proposes a strong ground effect zone-based confident triggering mechanism using dynamic residual verification of spatial gradients. This mechanism effectively filters out non-essential disturbance signals by constructing a kinematic correlation between vertical acceleration changes and spatial altitude, avoiding false triggering caused by single-critical-value judgments and providing a reliable criterion for safe switching of control modes.

[0026] This invention addresses the phase lag and integral saturation problems that traditional closed-loop feedback systems are prone to under ground effect nonlinear disturbances. It proposes an anti-disturbance control strategy based on altitude feedback truncation and second-order attitude impedance maintenance. This strategy actively truncates altitude feedback the instant the system enters the ground effect region, transforming strict altitude tracking into compliant attitude disturbance rejection. This smoothly absorbs ground effect aerodynamic disturbances and ensures the stability of the UAV's descent trajectory.

[0027] This invention addresses the safety hazard of deceleration difficulties during the ground effect runway phase of a large-sweep delta wing by proposing a dynamic monitoring and go-around decision-making mechanism based on a Total Energy Control System (TECS). This mechanism upgrades traditional thrust-trajectory decoupling control to integrated total energy control for the entire aircraft. Combined with a runway distance prediction algorithm, it can reliably trigger go-around protection when kinetic energy decay is insufficient or when subjected to sudden tailwind interference, reducing the risk of runway overrun.

[0028] This invention addresses the unique high angle-of-attack air cushion lift effect of delta wings by proposing a feedforward active unloading strategy based on ground contact signals from wheel-mounted sensors. This strategy confirms the overdrive attitude feedback loop at the moment of ground contact and outputs a step rudder deflection command to actively unload residual aerodynamic lift. From a dynamic perspective, this instantaneously disrupts the lift-weight balance at the moment of ground contact, effectively suppressing secondary bounce during landing and shortening the ground roll distance.

[0029] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 The flowchart of the autonomous landing control method for the turbofan delta-wing UAV in the first embodiment is shown. Figure 2 This is a timing diagram of the UAV landing altitude descent trajectory and the anti-accidental touch logic for ground effect zone perception in the first embodiment. Figure 3 This is a timing diagram of the UAV landing altitude descent trajectory and the anti-accidental touch logic for ground effect zone perception in the first embodiment. Figure 4 The diagram shows the effect of the dynamic residual verification mechanism based on the ground effect lift correction model in the first embodiment. Figure 5 A comparison diagram of the pitch attitude control effect of the UAV under strong ground effect disturbance in the first embodiment; Figure 6 This is a timing diagram for the instruction-free mode switching and active feedforward unloading in the first embodiment; Figure 7 This is a diagram illustrating the adaptive dynamic pressure and overdamped constraint scheduling law of the second-order impedance control in the first embodiment. Figure 8 The graph shows the total energy decay rate of the TECS in the first embodiment and the monitoring curve for re-flight. Detailed Implementation

[0032] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0034] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0035] Example 1 Existing technologies and conventional aircraft landing control schemes have the following technical limitations when dealing with the autonomous landing of turbofan delta-wing UAVs: First, conventional altitude closed-loop feedback is prone to inducing near-ground trajectory oscillations. Existing landing systems mostly employ continuous altitude error closed-loop feedback control. In the strong ground effect zone, the air cushion lift force exhibits altitude-unsteady characteristics. When dealing with such high-frequency nonlinear disturbances, conventional closed-loop control systems typically produce phase lag and control overshoot, leading to frequent reciprocating deflections of the elevator. This can easily cause high-frequency oscillations in the longitudinal trajectory of the UAV during the near-ground phase, and even trigger long-period trajectory divergence.

[0036] Secondly, the decoupled control of energy and trajectory can easily lead to insufficient kinetic energy decay. After entering the ground effect zone, the delta wing experiences a sharp decrease in induced drag, resulting in a significantly longer longitudinal deceleration distance. In traditional landing logic, thrust control and pitch trajectory control are often independently decoupled designs, lacking comprehensive closed-loop control of the total energy of the entire aircraft. When encountering sudden tailwinds or strong ground effect airflow, if the dynamic decay state of the specific energy cannot be assessed in time, the system may struggle to decelerate within a safe runway distance, significantly increasing the safety risks of overrunning the runway or missing the go-around window.

[0037] Third, passive touchdown mode is prone to landing bounce and structural impact. Most existing landing control laws maintain a fixed pitch attitude during the float-to-touch phase, relying on the wheels to decelerate naturally upon touchdown. For delta wings, if the residual aerodynamic lift is not actively disrupted at the moment of touchdown, the fuselage is prone to secondary bounce due to the coupling effect of ground reaction force and air cushion lift. This not only compromises landing dynamic stability but also increases abnormal fatigue loads on the landing gear structure.

[0038] Therefore, to address the challenges of high-frequency oscillations in flight control and extended drift distance caused by ground effect, the proposed spatial gradient dynamic residual verification mechanism, second-order impedance dynamic model of UAV pitch axis, total energy control system algorithm, and feedforward control strategy effectively suppress trajectory oscillations in the near-ground phase, improving the system's robustness against disturbances while ensuring landing dynamics safety.

[0039] like Figure 1 As shown, this embodiment discloses a landing method for a delta-wing unmanned aerial vehicle (UAV) to cope with ground effect nonlinear interference, including: Step S1: Using the acquired flight status and sensor data, determine whether the UAV has entered a strong ground effect zone based on the spatial gradient dynamic residual verification mechanism; Step S2: If it is determined that the strong ground effect zone has been entered, the altitude closed-loop feedback loop is cut off and the attitude impedance holding mode is smoothly switched. Step S3: Under the attitude impedance holding mode, construct a second-order impedance dynamic model of the UAV pitch axis and generate compensation rudder deflection commands to absorb ground effect disturbance torque. Step S4: During the deceleration and settling process, run the total energy control system algorithm, monitor the specific total energy attenuation rate in real time and predict the takeoff distance, and make a judgment on the redundancy protection for the go-around. Step S5: Monitor the main landing gear load sensor in real time, and trigger the feedforward control strategy to actively unload the residual aerodynamic lift and complete the landing at the moment of confirmation of ground contact.

[0040] Specifically, In step S1, to effectively isolate near-ground turbulence and random gust interference and achieve highly robust confidence triggering for strong ground effect areas, a confidence triggering mechanism for strong ground effect areas based on spatial gradient dynamic residual cross-validation is proposed, which specifically includes the following execution logic: During the approach and landing phase, the dimensionless altitude ratio of the UAV is calculated in real time by integrating data from the airborne radar altimeter and the inertial navigation system. (in This is the real-time altitude above the ground. (Measurements of the drone's wingspan) and overall vertical acceleration. When the radar altimeter measures In the near-ground environment, i.e., when the altitude is below one wingspan, the ground effect begins to take effect. The ground blocks the downward diffusion of the downwash airflow, causing the airflow to be blocked between the lower surface of the wing and the ground, forming a high-pressure stagnation zone. At the same time, it suppresses the wingtip vortex roll-up, and the system activates the dynamic residual evaluation mechanism based on continuous time windows.

[0041] Specifically, the flight control computer has a pre-installed theoretical model for ground effect lift correction:

[0042] in, The lift coefficient in the ground effect region. The free atmosphere lift coefficient, This is the ground effect amplification factor.

[0043] To ensure the engineering reliability and academic rigor of the simulation data, the ground effect amplification factor... The data was obtained through high-fidelity offline numerical simulation of computational fluid dynamics. During the solution process, the SST algorithm, suitable for strong adverse pressure gradients and flow separation phenomena near the ground, was employed. Shear Stress Transport (SST) turbulence model, controlling for dimensionless distances near the wall. Before extracting the discrete lift coefficients, a grid independence verification was performed, and finally, a continuous high-order polynomial benchmark curve was generated by fitting using the least squares method.

[0044] When a delta wing enters the ground effect zone, the ground obstructs the downward diffusion of the downwash, resulting in a significant decrease in induced drag nonlinearity and an increase in the effective angle of attack, thus generating additional air cushion lift. Its theoretically expected vertical acceleration increment... Compared with dimensionless height The following nonlinear mathematical mapping relationship exists:

[0045] in, This represents the theoretically expected increment of vertical acceleration. For drone quality; air density; Instantaneous flight speed; This is the reference area for the delta wing.

[0046] To effectively separate the random high-frequency gust step signal in the time domain from the deterministic ground effect signal in the spatial domain, the flight control computer does not perform single-critical-value matching on the acceleration amplitude at a single moment, but instead calculates the vertical acceleration measurement value in real time. and theoretical expected value Regarding ground clearance The slope of change is used to calculate the spatial gradient. Within continuous decision time windows, the system constructs the following dynamic residual verification inequality:

[0047] in, This is the measured value of the vertical acceleration of the entire machine; This represents the theoretically expected increment of vertical acceleration. This indicates the real-time altitude above the ground. The differential symbol (representing the computation of spatial gradient); This is a preset dynamic residual safety isolation threshold based on the background white noise characteristics of airborne sensors.

[0048] In this embodiment, to balance gust resistance robustness with ground effect triggering sensitivity, The value range is set to 0.05~0.20. In practical engineering applications, its specific value is set as the standard deviation of the background Gaussian white noise of the vertical acceleration of the airborne inertial sensor under static base calibration. Three times the normal value is used to ensure that sensor noise and spurious gradient signals caused by normal minor airflow disturbances are filtered out with a 99.73% confidence probability. In the discrete solution of airborne digital flight control, regarding altitude... The spatial gradient is equivalently transformed into the derivative of the variable with respect to time and the overall vertical sink rate. The ratio is obtained by calculation.

[0049] The measured acceleration growth trend and the theoretical ground effect spatial gradient satisfy a preset mapping relationship if and only if the above verification inequality is satisfied within a preset confidence time window. (i.e., continuous) Each flight control calculation cycle If the condition is continuously true for a given number of consecutive frames, the system outputs a confirmation trigger signal to determine that the aircraft has entered the strong ground effect zone.

[0050] In this embodiment, to balance real-time triggering and interference resistance reliability, the following is implemented: Set to 3-5 calculation cycles (e.g., at a flight control sampling rate of 50Hz, corresponding to a certainty time window). (0.06~0.10s). This mechanism requires, from a physical perspective, that significant changes in acceleration must have a clear spatial correlation, thereby effectively filtering out random gust interference that does not have a high degree of correlation, significantly improving the robustness of the ground effect zone cut-off determination, and ensuring the safety of subsequent high-level closed-loop cutoff actions.

[0051] In step S2, to effectively overcome the step abrupt changes and transient impacts caused by high closed-loop integral saturation after confirming entry into the strong ground effect region, the smooth handover logic is specifically as follows: At the moment of confirming entry into the strong ground effect zone (i.e., the output of the confirmation trigger signal in step S1), the flight control system actively cuts off the altitude PID closed-loop feedback loop and activates the disturbance-free switching mechanism of the underlying control commands to achieve a smooth transition to the open-loop "attitude impedance holding mode".

[0052] Specifically, at the height loop cutoff trigger moment The flight control system executes the following instructions in parallel to reconstruct the logic: First, the system immediately freezes the integral component of the height PID controller, synchronously stopping the continued accumulation of height error to avoid the delayed release effect caused by integral saturation; Secondly, the system reads and latches data in real time. The actual physical deflection angle of the elevator at any given moment This is used as the initial feedforward reference quantity of the control system after the switch. Finally, within the preset control handover time window Internally, the system introduces a weight allocation factor that decays smoothly over time. Construct the following composite transition control law:

[0053] in, To control the elevator deflection commands that the flight control system ultimately outputs to the actuators within the handover time window; The time-smoothing decay weighting factor is in the interval The value continuously and monotonically decreases from 1.0 to 0. To truncate the actual elevator deflection constant latched at the trigger moment; The impedance control output command is calculated in real time based on the current flight attitude for the target control mode after switching (i.e., the attitude impedance holding mode in step S3 below); This is the initial switching moment that is confirmed to be triggered in the subsurface area; The preset control handover time window length.

[0054] Furthermore, impedance control output command A linear mapping solution is performed based on attitude deviation and elevator aerodynamic control effectiveness. The specific mapping model is as follows:

[0055] In the formula, The elevator steady-state trim deflection angle for the UAV in the current approach state; The control surface mapping gain coefficient is preset based on the aerodynamic derivative of the aircraft; The current real-time pitch angle; The target is the angle of attack. This mapping mechanism converts the attitude evolution of the virtual impedance characteristics into compensation actions of the physical actuators in real time.

[0056] When flight time At that time, the smooth decay weighting factor At this point, the system is essentially controlled by the attitude impedance control law. This disturbance-free switching mechanism, through a composite algorithm architecture of "physical state latching and smooth weight transfer," effectively suppresses the abrupt change in control surface caused by integral saturation release, cuts off the high-frequency feedback path from ground effect nonlinear disturbances to the control surface at the execution level, and ensures a smooth transition of the UAV's control modes under complex aerodynamic interference.

[0057] In step S3, to maintain the stability of the aircraft's pitch attitude under the support of a strong air cushion, rigid feedback is transformed into flexible disturbance rejection absorption. The specific adaptive control logic is as follows: In attitude impedance holding mode, the system reduces the tracking feedback weight for altitude trajectory and instead treats the UAV's pitch axis as a virtual physical system with second-order impedance dynamic characteristics. This allows for flexible absorption of high-frequency ground-effect disturbance torques, locking the attitude at high angles of attack, and utilizing the high induced drag of the delta wing itself for passive aerodynamic deceleration. Its pitch rotation impedance equation is defined as:

[0058] in, For pitch inertia; To lock onto the desired high angle of attack for landing; and These are the real-time pitch angle and pitch rate, respectively. For external ground effect aerodynamic disturbance torque; For dynamic virtual stiffness; For dynamic virtual damping.

[0059] To overcome the problem of nonlinear decay of control surface effectiveness during landing deceleration and to effectively avoid periodic bouncing from a physical mechanism perspective, the flight control system adopts the following strict dynamic adaptive scheduling law for impedance parameters: (1) Adaptive damping adjustment of virtual stiffness. According to aerodynamic principles, the control torque of the control surface is proportional to the dynamic pressure. If the stiffness remains constant, it is easy to induce elevator command overload saturation at low speeds. Therefore, the system uses the initial reference speed at the moment of entering the ground effect zone. Based on real-time airspeed, a system is constructed. Dynamic pressure scheduling regulation law:

[0060] in, The nominal reference stiffness is set; The initial reference velocity at the moment of entry into the subsurface zone; This refers to the instantaneous airspeed. This mechanism ensures that the control stiffness decreases proportionally as the aerodynamic environment deteriorates.

[0061] (2) Overdamped rigid constraint mechanism of virtual damping. In order to effectively suppress the tendency of aircraft to bounce caused by ground effect disturbance, the system needs to adjust the damping ratio of the impedance equation. Constantly limited to the critical damping or overdamped range Based on the standard form equivalence principle of a second-order system, the virtual damping follower regulation law of the system is defined as follows:

[0062] in, The damping ratio constraint is set for the system (set as a constant greater than or equal to 1.0). This underlying servo constraint adjustment law ensures that regardless of the virtual stiffness... How does the system damping soften as flight speed decreases? It can always recalculate synchronously and maintain a very strong oscillation absorption capability, thus eliminating the physical conditions for the drone to bounce twice and induce high-frequency oscillations from the mathematical model.

[0063] The flight control system executes step S4 in parallel in the background to provide an objective benchmark for judging the critical runway overrun risk, in order to quantify the kinetic and potential energy decay state of the high angle of attack ground effect taxiing segment in real time. Its specific operating logic is as follows: During deceleration and settlement in impedance-maintaining mode, to prevent runway overrun accidents caused by excessively slow energy decay due to sudden tailwinds or overly strong ground effect, the total energy control system (TECS) algorithm runs in parallel in the flight control system's background. This system calculates the rate of change of specific total energy in real time, determined by the difference between instantaneous thrust and aerodynamic drag. Its calculation model is as follows:

[0064] in, This is the instantaneous rate of change of total specific energy, expressed in m / s. This refers to the instantaneous thrust of the engine. The instantaneous aerodynamic drag of the entire aircraft; Instantaneous airspeed; For drone quality; This is due to gravitational acceleration. During the landing and leveling phase, the drag is greater than the engine thrust (i.e.,...). Therefore It typically exhibits a negative value within the normal deceleration settlement range.

[0065] Simultaneously, the system utilizes an advanced integral algorithm to predict the taxiing and braking distance under the current motion state, and constructs the following landing safety assessment and go-around redundancy protection trigger inequality:

[0066] in, It is the absolute value of the total energy decay rate; This is the preset minimum safety ratio total energy decay rate threshold value; This represents the remaining distance from the current drone position to the end of the runway. For integration variables; This is the current determination time; This is the predicted moment when the drone will come to a near stop. That is, the braking distance of the runway is predicted in advance using an integral algorithm; The instantaneous airspeed is assumed to be equivalent to ground speed in windless conditions.

[0067] The system determines that the current landing trajectory poses a high risk of runway overrun only when the above inequality holds true: that is, the energy decay rate is insufficient (the absolute value of the decay rate is less than the safety threshold) and the predicted braking distance exceeds the remaining runway length. In this case, the flight control system will forcibly exit the current impedance control mode and directly output the maximum available thrust pull-up command. This redundancy protection mechanism provides significant safety redundancy for autonomous landing in complex aerodynamic environments.

[0068] In step S5, to break the critical balance of lift and weight at the moment of landing of the delta wing from the physical source and effectively suppress the secondary bounce and floating tendency after landing, the specific feedforward control logic is as follows: At the moment of main landing gear touchdown, to effectively overcome the lag in feedback control, this system implements an active unloading strategy based on hardware signal feedforward with no computational wait. Specifically, the flight control system monitors the load sensors of the main landing gear in real time with priority; once the sensor electrical signal state undergoes its first level flip to confirm valid ground contact, the system no longer waits for passive feedback evolution of flight attitude or trajectory, but directly uses the discrete electrical signal as a priority feedforward trigger switch.

[0069] Within the high-dynamic control cycle window confirming ground contact, the flight control system outputs a step-like full-bore stick command at the maximum servo bandwidth of the actuators, coordinating with the deflection of the wing's auxiliary aerodynamic deceleration surfaces. This feedforward action injects a peak dynamic nose-down moment into the pitch axis, rapidly reducing the wing's true aerodynamic angle of attack within the necessary control cycle. This makes the overall dynamic lift coefficient of the aircraft... A significant decrease in nonlinearity occurs, thereby achieving the following in terms of aerodynamic characteristics:

[0070] In the formula, This refers to the overall dynamic lift coefficient of the aircraft. It is a time variable; This is a preset positive lower bound parameter for the lift coefficient attenuation rate.

[0071] This mechanism utilizes an active feedforward control strategy to quickly break the critical balance state of lift at the moment of ground contact, effectively blocking the high angle-of-attack ground effect floating tendency unique to delta wings from the physical source; at the same time, the rapid reduction of pitch attitude allows the wheel braking system to quickly obtain the maximum positive pressure brought by the weight of the entire aircraft, thereby effectively suppressing the ground effect rebound phenomenon and significantly shortening the ground roll distance after landing.

[0072] like Figure 2 As shown, during the normal approach phase of the UAV, the flight control system maintains closed-loop altitude control and monitors the UAV's descent status in real time. When the ground effect begins to occur, the system activates the ground effect zone determination logic. This determination logic is based on cross-validation of multi-dimensional parameters, specifically including: fusing multi-source data from radar altitude and inertial navigation system, calculating the gradient change of vertical acceleration in the spatial dimension, performing dynamic residual verification to eliminate random gust interference, and using a confidence time window. Continuous validation is performed. This mechanism ensures that the system only triggers mode switching when it captures ground effect features with clear spatial relevance.

[0073] Once the system is certain that it has entered the strong ground effect region, it immediately triggers a control mode switching procedure from altitude feedback to attitude impedance maintenance. For example... Figure 2 As shown in the flowchart on the right, this process first actively truncates the altitude PID closed-loop feedback loop through a command override mechanism, physically and logically blocking the transmission of ground-effect nonlinear disturbances to the trajectory level. At the moment of truncation, the system latches the current elevator deflection angle in real time as an initial mean square measure. Through repeated latching and state verification, the continuity and stability of command output are ensured, and finally, the system smoothly transitions into the attitude impedance maintenance mode. This mode switching achieved through feedback truncation and state latching effectively solves the trajectory oscillation problem caused by integral saturation in the near-ground phase, realizing flexible disturbance rejection protection during landing.

[0074] In this embodiment, to verify the effectiveness and engineering feasibility of the proposed autonomous landing method for a turbofan delta-wing UAV based on ground effect altitude feedback cutoff and attitude impedance maintenance, a longitudinal nonlinear landing dynamics model of the turbofan delta-wing UAV was built in a simulation environment. The core control objective of this simulation is to verify whether the system can accurately perceive strong ground effects through dynamic residuals during the approach and landing phase (step S1), achieve disturbance-free switching of control modes (step S2), use second-order impedance control to flexibly absorb ground effect disturbances to maintain attitude stability (step S3), objectively monitor deceleration and settlement safety through the total energy control system (step S4), and effectively execute feedforward active unloading actions at the moment of ground contact (step S5).

[0075] The initial simulation conditions are as follows: the UAV is specified to be in the glide phase of approach and landing, and its initial altitude is... Initial approach vacuum velocity The landing aerodynamic environment was simulated by superimposing standard Gaussian white noise with a high-altitude gust model to mimic near-ground turbulence. The basic physical parameters of the delta-wing UAV were set as follows: total mass of the entire aircraft... delta wing reference area Wingspan pitch axis moment of inertia .

[0076] Based on the aerodynamic characteristics and sensor hardware specifications of the UAV, the core parameters of the control law of this invention are calibrated: Expected landing with a high angle of attack Set to 12°; Spatial gradient dynamic residual safety isolation critical value Set to 0.15s -2 ; Ground effect certainty time window critical value Set to 0.4s; Control handover time window length for bumpless handover Set to 0.4s; Nominal reference stiffness controlled by second-order impedance Damping ratio constraint value Set to 1.2 (satisfies) (overdamped physical constraints). TECS minimum safety ratio total energy decay rate critical value Set to 1.0 m / s; The extreme value of the feedforward full offset push rod command at the moment of ground contact is set to -20°.

[0077] Simulation results are as follows Figures 3 to 8 As shown.

[0078] like Figure 3 The diagram illustrates the timing of the UAV's landing altitude descent trajectory and the anti-accidental touch logic for the ground effect zone. At that time, height above the ground Upon descending to a physical ground effect zone of one wingspan (2.4m), the system triggers the residual assessment activation flag. After continuous evaluation within a set time window, the final ground effect confirmation trigger flag is at a high level, objectively verifying the timing accuracy of the judgment logic.

[0079] like Figure 4 As shown, a dynamic residual verification mechanism based on the ground effect lift correction model is demonstrated. Under complex operating conditions introducing airflow disturbances and sensor background noise, the measured spatial gradient dynamic residual is effectively limited to the tolerance safety judgment zone within the evaluation time window (i.e., This indicates that the mechanism can effectively isolate random gust interference and accurately extract spatially correlated true ground effect features.

[0080] like Figure 5 As shown, this illustrates a comparison of the pitch attitude control performance of a UAV under strong ground effect disturbances. When encountering a non-command pitching torque due to ground effect, traditional PID control (black dashed line) exhibits significant passive pitching and subsequent phase lag oscillations due to integral saturation and rigid countermeasures. In contrast, the attitude impedance holding method (red solid line) used in this embodiment actively transforms rigid, error-free tracking into flexible absorption, allowing the nose to produce a compliant deflection of a specific amplitude (stabilizing at around 11.8°), effectively suppressing the high-risk "dolphin jump" oscillations at the physical system level.

[0081] like Figure 6 The diagram illustrates the action states of uninterrupted command mode switching and active feedforward unloading upon ground contact. After confirming entry into the ground effect zone, the elevator physical commands smoothly transitioned from the nominal trim state to the impedance control state within a 0.4s handover time window, without any command jumps. At the moment of impact, the system outputs a step full deflection command (-20°) in a feedforward manner, actively breaking the lift-weight critical balance of the delta wing at high angles of attack.

[0082] like Figure 7 The diagram illustrates the scheduling law of second-order impedance-controlled dynamic pressure adaptation and overdamped constraint. As the flight speed decreases, the dynamic virtual stiffness... With dynamic virtual damping All exhibit a proportional, adaptive decreasing trend. The underlying constraint mechanism ensures that the system damping ratio always satisfies the overdamping condition, providing a rigid mathematical guarantee for the system to absorb oscillations.

[0083] like Figure 8 The diagram illustrates real-time safety monitoring of the TECS specific energy decay rate during the landing deceleration and settlement phase. The specific energy decay rate is calculated in real-time across the entire approach settlement profile. It remains within the normal deceleration dissipation range (i.e., its amplitude) The threshold for triggering a go-around alarm exceeds the set threshold. This objectively verifies that the current dynamic state can meet the requirements for safe taxiing and parking. Example 2 This embodiment discloses a delta-wing unmanned aerial vehicle (UAV) landing system for coping with ground effect nonlinear interference, including: The ground effect perception and triggering module is configured to: use the acquired flight status and sensor data, based on the spatial gradient dynamic residual verification mechanism, to determine whether the UAV has entered a strong ground effect zone; The closed-loop cutoff and switching module is configured to: if it is determined that the strong ground effect zone has been entered, cut off the height closed-loop feedback loop and smoothly switch to the attitude impedance holding mode; The energy monitoring and go-around module is configured to: construct a second-order impedance dynamic model of the UAV pitch axis under attitude impedance holding mode, and generate compensation rudder deflection commands to absorb ground effect disturbance torque; The impedance disturbance rejection control module is configured to: run the total energy control system algorithm during deceleration and settlement, monitor the specific total energy attenuation rate in real time and predict the takeoff distance, and make a judgment on the redundancy protection for go-around. The feedforward unloading and anti-bounce module is configured to: monitor the main landing gear load sensor in real time, and trigger the feedforward control strategy to actively unload the residual aerodynamic lift and complete the landing at the moment of confirmation of ground contact.

[0084] Example 3 The purpose of this embodiment is to provide a computer-readable storage medium.

[0085] A computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the steps in the landing method for a delta-wing unmanned aerial vehicle (UAV) for responding to ground effect nonlinear interference as described in Embodiment 1 of this disclosure.

[0086] Example 4 The purpose of this embodiment is to provide an electronic device.

[0087] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the landing method for a delta-wing unmanned aerial vehicle to cope with ground effect nonlinear interference as described in Embodiment 1 of this disclosure.

[0088] The steps and methods involved in the apparatuses of Embodiments 2, 3, and 4 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0089] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0090] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A landing method for a delta-wing unmanned aerial vehicle (UAV) to cope with ground effect nonlinear interference, characterized in that, include: Using the acquired flight status and sensor data, and based on the spatial gradient dynamic residual verification mechanism, it is determined whether the UAV has entered the strong ground effect zone; If it is determined that the strong ground effect zone has been entered, the altitude closed-loop feedback loop is cut off and the attitude impedance holding mode is smoothly switched; Under the attitude impedance holding mode, a second-order impedance dynamic model of the UAV pitch axis is constructed to generate a compensating rudder deflection command to absorb ground effect disturbance torque. During the deceleration and settling process, the total energy control system algorithm is run to monitor the specific total energy attenuation rate in real time and predict the takeoff distance, and to make a judgment on the redundancy protection for the go-around. The system monitors the main landing gear load sensors in real time and triggers a feedforward control strategy to actively unload residual aerodynamic lift and complete the landing the moment the ground contact is confirmed.

2. The landing method for a delta-wing unmanned aerial vehicle (UAV) to cope with ground effect nonlinear interference as described in claim 1, characterized in that, The judgment verification inequality of the spatial gradient dynamic residual verification mechanism is as follows: In the formula, The differential symbol; This is the measured value of the vertical acceleration of the entire machine; This represents the theoretically expected increment of vertical acceleration. This indicates the real-time altitude above the ground. This is the preset dynamic residual safety isolation threshold. The system determines that the UAV has entered the strong ground effect zone if and only if the above verification inequality holds true continuously within the preset confidence time window.

3. The landing method for a delta-wing UAV to cope with ground effect nonlinear interference as described in claim 1, characterized in that, The composite transition control law for the smooth switching to the attitude impedance holding mode is as follows: In the formula, To control the elevator deflection command ultimately output by the flight control system within the handover time window; The time-smoothing decay weighting factor is used in the interval Internal continuous monotonically decreasing; To truncate the actual elevator deflection constant latched at the trigger moment; The impedance control output command is used for the impedance maintenance mode calculation after the switch. This is the initial switching moment that is confirmed to be triggered in the subsurface area; The preset control handover time window length.

4. The landing method for a delta-wing UAV to cope with ground effect nonlinear interference as described in claim 1, characterized in that, The pitch rotation impedance equation of the second-order impedance dynamic model of the UAV pitch axis is defined as: In the formula, For pitch inertia; To lock onto the desired high angle of attack for landing; and These are the real-time pitch angle and pitch rate, respectively. For external ground effect aerodynamic disturbance torque; For dynamic virtual stiffness; For dynamic virtual damping; Dynamic virtual stiffness and dynamic virtual damping follow the following dynamic adaptive scheduling law: In the formula, For dynamic virtual stiffness, For dynamic virtual damping, The nominal reference stiffness is set; The initial reference velocity at the moment of entry into the subsurface zone; Instantaneous airspeed; Damping ratio constraints set for the system.

5. The landing method for a delta-wing unmanned aerial vehicle (UAV) to cope with ground effect nonlinear interference as described in claim 1, characterized in that, The total energy control system algorithm calculates the specific rate of change of total energy as follows: In the formula, This represents the instantaneous rate of change of total energy. This refers to the instantaneous thrust of the engine. The instantaneous aerodynamic drag of the entire aircraft; Instantaneous airspeed; For drone quality; This is the acceleration due to gravity.

6. The landing method for a delta-wing unmanned aerial vehicle (UAV) to cope with ground effect nonlinear interference as described in claim 1, characterized in that, The triggering condition for the re-flight redundancy protection determination is: and In the formula, It is the absolute value of the total energy decay rate; This is the preset minimum safety ratio total energy decay rate threshold value; This represents the remaining runway length. For integration variables; This is the current determination time; This is the basic stabilization point predicted in advance; This refers to the predicted skid braking distance.

7. The landing method for a delta-wing unmanned aerial vehicle (UAV) to cope with ground effect nonlinear interference as described in claim 1, characterized in that, The feedforward control strategy includes: Within the high-dynamic control cycle time window confirming ground contact, the system outputs a step-type full-deflection stick command, coordinating with the deflection of the wing's auxiliary aerodynamic deceleration surfaces; thus increasing the overall dynamic lift coefficient of the aircraft. A significant nonlinear decrease occurs, satisfying the following aerodynamic characteristic relationship: In the formula, This refers to the overall dynamic lift coefficient of the aircraft. It is a time variable; This is a preset positive lower bound parameter for the lift coefficient attenuation rate.

8. A delta-wing unmanned aerial vehicle (UAV) landing system for coping with ground effect nonlinear interference, characterized in that, include: The ground effect perception and triggering module is configured to: use the acquired flight status and sensor data, based on the spatial gradient dynamic residual verification mechanism, to determine whether the UAV has entered a strong ground effect zone; The closed-loop cutoff and switching module is configured to: if it is determined that the strong ground effect zone has been entered, cut off the height closed-loop feedback loop and smoothly switch to the attitude impedance holding mode; The energy monitoring and go-around module is configured to: construct a second-order impedance dynamic model of the UAV pitch axis under the attitude impedance holding mode, and generate compensation rudder deflection commands to absorb ground effect disturbance torque; The impedance disturbance rejection control module is configured to: run the total energy control system algorithm during deceleration and settlement, monitor the specific total energy attenuation rate in real time and predict the takeoff distance, and make a judgment on the redundancy protection for go-around. The feedforward unloading and anti-bounce module is configured to: monitor the main landing gear load sensor in real time, and trigger the feedforward control strategy to actively unload the residual aerodynamic lift and complete the landing at the moment of confirmation of ground contact.

9. A computer-readable storage medium having a program stored thereon, characterized in that, When executed by the processor, the program implements the steps in the landing method for a delta-wing unmanned aerial vehicle (UAV) for dealing with ground effect nonlinear interference as described in any one of claims 1-7.

10. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the landing method for a delta-wing unmanned aerial vehicle (UAV) for dealing with ground effect nonlinear interference as described in any one of claims 1-7.

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