An unmanned aerial vehicle guidance method and device based on recursive sliding mode, equipment and medium

Abstract

The application discloses a kind of unmanned aerial vehicle guidance methods, device, equipment and medium based on recursive sliding mode, it is related to unmanned aerial vehicle flight control technical field, including: the guidance channel of unmanned aerial vehicle is decomposed into horizontal channel and vertical channel;Target recursive sliding surface is respectively constructed in horizontal channel and vertical channel, and equivalent control item is constructed according to target recursive sliding surface, and switch compensation item of sliding mode controller is generated according to external disturbance;In vertical channel, the gravity compensation item of unmanned aerial vehicle is determined, and the angle of descent bias control amount is calculated according to the angle of descent constraint of unmanned aerial vehicle;Equivalent control item, switch compensation item, gravity compensation item and angle of descent bias control amount are superposed to obtain target guidance instruction, and target guidance instruction is used to guide unmanned aerial vehicle.By generating switch compensation item according to external disturbance, dynamic robust suppression to target maneuver and environmental disturbance is realized, and the precision of unmanned aerial vehicle guidance is improved.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) flight control technology, and in particular to a UAV guidance method, device, equipment, and medium based on recursive sliding mode. Background Technology

[0002] In the research on guidance and control of UAVs against dynamic targets, the construction of three-dimensional relative motion models, line-of-sight dynamics, and robust guidance laws has long been the core of the research.

[0003] Existing UAV guidance methods mainly rely on the geometric relationship of the line-of-sight angle or a single-layer sliding surface structure to track targets. This method is prone to problems such as response lag, increased jitter, or decreased guidance accuracy, and its robustness and controllability are difficult to meet the requirements of modern UAV missions. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a UAV guidance method, apparatus, device, and medium based on recursive sliding mode, which can achieve dynamic robust suppression of target maneuvers and environmental disturbances by generating switching compensation terms according to external disturbances, thereby improving the guidance accuracy of UAVs. The specific solution is as follows:

[0005] Firstly, this application provides a UAV guidance method based on recursive sliding mode, including:

[0006] Establish a relative motion model between the UAV and the dynamic target, and decompose the UAV's guidance channel into a horizontal channel and a vertical channel based on the relative motion model;

[0007] Target recursive sliding surfaces are constructed in the horizontal channel and the vertical channel respectively. In the horizontal channel and the vertical channel, equivalent control terms are constructed according to the corresponding target recursive sliding surfaces. Switching compensation terms of the sliding controller are generated according to external disturbances. The equivalent control terms are the control quantities obtained when the derivative of the target recursive sliding surface is zero.

[0008] In the vertical channel, the gravity compensation term of the UAV is determined based on the pitch attitude of the UAV, and the corresponding landing angle offset control amount is calculated according to the landing angle constraint of the UAV.

[0009] The equivalent control term, the switch compensation term, the gravity compensation term, and the landing angle offset control term are superimposed to obtain the target guidance command, and the target guidance command is used for UAV guidance.

[0010] Optionally, after establishing the relative motion model between the UAV and the dynamic target, the method further includes:

[0011] Construct a gust model to describe the time-varying characteristics of wind speed, a wind shear model to describe the variation of wind speed with spatial location, and a horizontal wind model to describe the stochastic characteristics of natural wind.

[0012] The wind disturbance data generated by the gust model, the wind shear model, and the horizontal wind model are obtained, and the external disturbance is determined based on the wind disturbance data.

[0013] Optionally, constructing the target recursive sliding surface in the horizontal channel and the vertical channel respectively includes:

[0014] In the horizontal channel and the vertical channel, a first sliding surface is constructed based on the corresponding guidance error; wherein, the first sliding surface is a fast non-singular terminal sliding surface;

[0015] Add a target integral term to the first sliding surface to obtain the second sliding surfaces corresponding to the horizontal channel and the vertical channel respectively. Set the value of the second sliding surface to zero at the initial guiding moment, and construct the target recursive sliding surface using the first sliding surface and the corresponding second sliding surface.

[0016] Optionally, the step of generating the switching compensation term for the sliding mode controller based on external disturbances includes:

[0017] The upper bound of the disturbance of the target acceleration is evaluated to obtain the corresponding target estimate, and the switching compensation term of the sliding mode controller is constructed based on the target estimate and the target recursive sliding surface; wherein, the target acceleration is the equivalent acceleration caused by external disturbance and the maneuvering behavior of guiding the target.

[0018] Optionally, the determination of the gravity compensation term for the UAV based on its pitch attitude includes:

[0019] The pitch attitude of the UAV is determined, the projection component of gravity in the normal direction of the vertical channel is determined based on the pitch attitude, and the gravity compensation term is determined based on the projection component.

[0020] Optionally, the step of calculating the corresponding landing angle offset control amount based on the landing angle constraint of the UAV includes:

[0021] The landing angle offset control value is calculated based on the difference between the landing angle constraint and the current line-of-sight angle, the remaining flight time of the UAV, and the relative motion relationship between the UAV and the guided target.

[0022] Optionally, the step of superimposing the equivalent control term, the switch compensation term, the gravity compensation term, and the landing angle offset control value to obtain the target guidance command includes:

[0023] In the horizontal channel, the equivalent control term and the switch compensation term are superimposed to generate a horizontal channel guidance command;

[0024] In the vertical channel, the equivalent control term, the switch compensation term, the gravity compensation term, and the drop angle offset control term are superimposed to generate a vertical channel guidance command;

[0025] The target guidance command is generated using the horizontal channel guidance command and the vertical channel guidance command.

[0026] Secondly, this application provides a UAV guidance device based on recursive sliding mode, comprising:

[0027] The channel decomposition module is used to establish a relative motion model between the UAV and the dynamic target, and decompose the UAV's guidance channel into a horizontal channel and a vertical channel based on the relative motion model.

[0028] A sliding surface construction module is used to construct target recursive sliding surfaces in the horizontal channel and the vertical channel respectively, construct equivalent control terms in the horizontal channel and the vertical channel according to the corresponding target recursive sliding surfaces, and generate switching compensation terms for the sliding controller according to external disturbances; the equivalent control terms are the control quantities obtained when the derivative of the target recursive sliding surface is zero;

[0029] The gravity compensation term determination module is used to determine the gravity compensation term of the UAV based on the pitch attitude of the UAV in the vertical channel, and to calculate the corresponding landing angle offset control amount according to the landing angle constraint of the UAV.

[0030] The UAV guidance module is used to superimpose the equivalent control item, the switch compensation item, the gravity compensation item, and the landing angle offset control quantity to obtain the target guidance command, and to use the target guidance command to guide the UAV.

[0031] Thirdly, this application provides an electronic device, comprising:

[0032] Memory, used to store computer programs;

[0033] A processor is used to execute the computer program to implement the aforementioned UAV guidance method based on recursive sliding mode.

[0034] Fourthly, this application provides a computer-readable storage medium for storing a computer program that, when executed by a processor, implements the aforementioned UAV guidance method based on recursive sliding mode.

[0035] This application first establishes a relative motion model between the UAV and the dynamic target, and decomposes the UAV's guidance channel into a horizontal channel and a vertical channel based on the relative motion model. Then, a target recursive sliding surface is constructed in the horizontal channel and the vertical channel respectively. In the horizontal channel and the vertical channel, equivalent control terms are constructed according to the corresponding target recursive sliding surface, and a switching compensation term for the sliding controller is generated according to external disturbances. The equivalent control term is the control quantity obtained when the derivative of the target recursive sliding surface is zero. Then, in the vertical channel, the gravity compensation term of the UAV is determined based on the pitch attitude of the UAV, and the corresponding landing angle offset control quantity is calculated according to the landing angle constraint of the UAV. Finally, the equivalent control term, the switching compensation term, the gravity compensation term, and the landing angle offset control quantity are superimposed to obtain the target guidance command, and the UAV is guided using the target guidance command. Therefore, this application achieves precise compensation for nonlinear coupling by constructing a target recursive sliding surface and building an equivalent control term, eliminating the arrival stage of traditional sliding mode and ensuring rapid error convergence; by generating a switching compensation term based on external disturbances, it achieves dynamic robust suppression of target maneuvers and environmental disturbances, reducing chattering; by introducing a gravity compensation term in the vertical channel, it overcomes the response hysteresis caused by gravity in the initial stage; by calculating the landing angle offset control quantity based on the landing angle constraint, it achieves precise control of the terminal landing angle; finally, it superimposes the various control quantities to obtain the target guidance command, enabling the UAV to achieve high-precision guidance in complex environments. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the unmanned aerial vehicle (UAV) guidance method based on recursive sliding mode disclosed in this application;

[0038] Figure 2 This is a schematic diagram of the line-angle relationship between an unmanned aerial vehicle and a guided target disclosed in this application;

[0039] Figure 3 This is a schematic diagram of a sliding mode structure disclosed in this application;

[0040] Figure 4 This is a schematic diagram of a three-dimensional trajectory corresponding to one of the different guidance methods disclosed in this application;

[0041] Figure 5 This is a schematic diagram of the XY plane projection corresponding to one of the different guiding methods disclosed in this application;

[0042] Figure 6 This is a schematic diagram of a UAV guidance device based on recursive sliding mode disclosed in this application;

[0043] Figure 7 This is a structural diagram of an electronic device disclosed in this application. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Current UAV guidance methods are prone to issues such as response lag, increased jitter, or decreased guidance accuracy, and their robustness and controllability are insufficient to meet the requirements of modern UAV missions. To address this, this application provides a UAV guidance method based on recursive sliding mode. By generating a switching compensation term based on external disturbances, it achieves dynamic robust suppression of target maneuvers and environmental disturbances, thereby improving UAV guidance accuracy.

[0046] See Figure 1 As shown, this embodiment of the invention discloses a UAV guidance method based on recursive sliding mode, including:

[0047] Step S11: Establish a relative motion model between the UAV and the dynamic target, and decompose the UAV's guidance channel into a horizontal channel and a vertical channel based on the relative motion model.

[0048] In this embodiment, it is first necessary to establish a relative motion model between the UAV and the dynamic target, and then decompose the UAV's guidance channel into a horizontal channel and a vertical channel based on the relative motion model. The specific process is as follows:

[0049] Step 1: Modeling the relative motion of UAV moving target guidance:

[0050] 1.1. Relative motion guidance equations between machine and eye:

[0051] In UAV guidance of dynamic targets, guidance laws are typically designed based on the relative motion between the UAV and the target. Therefore, it is necessary to first establish a relative motion model describing the changes in distance and line-of-sight (LAS) angle between the UAV and the target. The rotation rate of the LAS angle directly determines the generation of guidance commands; therefore, its dynamic relationship is the foundation for constructing any guidance method. To accurately describe the geometric and kinematic coupling relationships of the UAV-target system, the following set of relative motion equations can be established to characterize the changes in distance, horizontal LAS angle, and vertical LAS angle over time:

[0052] ;

[0053] In the formula, r is the distance between the target and the drone. and The speeds of the target and the missile, respectively. and Here, θ represents the lead angle of the target and missile velocity vectors, respectively, and k is the scaling factor. θ is the missile guidance angle, and q is the line-of-sight angle of the missile target.

[0054] To simplify the calculation, the three-dimensional ballistic trajectory can be decomposed into a horizontal plane and a vertical plane. Corresponding guidance equations can be established and modeled on these two planes respectively. Then, the component motions on these two planes can be synthesized to obtain the entire pursuit curve.

[0055] In a three-dimensional Cartesian coordinate system, let the coordinates of the UAV and the target at a certain moment be respectively... and Assuming both the target and the drone are moving at a constant speed, their speeds are respectively and .

[0056] The relative coordinates of the aircraft and the target are represented as follows:

[0057] ;

[0058] Based on the motion relationship between the aircraft and the target, the equations of the center of mass of the aircraft and the target are as follows:

[0059] ;

[0060] ;

[0061] In the formula, and Let be the angle between the velocity directions of the aircraft and the target and the z-axis. and Let be the angle between the projection of the aircraft's and the target's velocities onto the horizontal plane and the x-axis. The time elapsed before the target changes course is... Afterwards, the coordinates of the drone and the target are:

[0062] ;

[0063] ;

[0064] Assuming the target is The target begins its maneuver at a certain moment, undergoing sinusoidal motion in the vertical plane. Let its amplitude be , and the period of the sinusoidal maneuver be T. Then its angular velocity during the sinusoidal maneuver is: ;

[0065] Calculations show that:

[0066] ;

[0067] The time remains unchanged. Therefore, it can be deduced that the target changed orbit after a certain period of time. The target coordinate equation is as follows:

[0068] ;

[0069] Decomposition of the spatial motion of the aircraft and the target:

[0070] Decomposing the three-dimensional spatial motion into independent motions in two planes, horizontal and vertical, the target line angles in the horizontal and vertical planes are as follows:

[0071] ;

[0072] Target line angle in relative motion, such as Figure 2 As shown.

[0073] In the formula, and These are the target line angles in the horizontal and vertical planes, respectively. Based on the guidance relationship, we can obtain:

[0074] ;

[0075] and These are the guidance angles of the UAV in the horizontal and vertical planes, respectively. Similarly, after time... Based on the above formula, we can obtain the equivalent form:

[0076] ;

[0077] Therefore, it can be seen that, through a certain number of iterations, the three-dimensional motion trajectories of the aircraft and the target can be calculated.

[0078] By further differentiating it and substituting the relative acceleration, we can obtain the general form of the second-order dynamics at the line-of-sight angle:

[0079] ;

[0080] in , These are the equivalent accelerations of the target and the aircraft in the horizontal normal direction, respectively. The geometric coupling term consists of relative position and velocity. This is the horizontal projection of the distance between the drone and the target.

[0081] ;

[0082] Similarly, in the perpendicular plane, we can obtain:

[0083] ;

[0084] in , The equivalent acceleration is in the vertical normal direction. This is the geometric coupling term for the vertical line-of-sight angle.

[0085] ;

[0086] Adding a dot above the original sign indicates the first derivative of the original sign, while adding two dots indicates the second derivative. For example... , , , , , They are respectively , , , , , The first differential.

[0087] In summary, the relative motion between the three-dimensional machine and the eye can ultimately be unified into the following line-of-sight angle dynamic equation:

[0088] ;

[0089] The relative motion model in this embodiment includes the formulas described above for the motion relationship between the UAV and the guided target.

[0090] In addition, in this embodiment, after establishing the relative motion model between the UAV and the dynamic target, the method further includes: constructing a gust model to describe the time-varying characteristics of wind speed, constructing a wind shear model to describe the changes in wind speed with spatial location, and constructing a horizontal wind model to describe the random characteristics of natural wind; acquiring wind disturbance data generated by the gust model, wind shear model and horizontal wind model, and determining external disturbances based on the wind disturbance data.

[0091] Specifically, in the aforementioned three-dimensional aircraft-target relative motion model, we primarily started from an idealized environment, deriving the position evolution equations of the aircraft and target in inertial space, as well as the line-of-sight dynamics model centered on the target line angle. This provided a unified and controllable dynamic foundation for the subsequent construction of guidance laws. However, in actual flight environments, the atmospheric conditions in which UAVs operate often exhibit significant randomness and time-varying characteristics, especially near low altitudes or complex terrain. Wind disturbances can have a critical impact on relative motion relationships, line-of-sight angular rates, and guidance control accuracy. Therefore, it is necessary to further introduce a mechanically reasonable atmospheric wind disturbance model based on the relative motion model to describe external uncertainties in real-world environments.

[0092] Based on the above considerations, this section models typical atmospheric wind disturbance characteristics, thereby incorporating wind speed variations into the relative motion equations. This lays the foundation for the subsequent design of a robust and adaptive guidance law. The wind disturbance model can be used both as part of the unknown disturbance and compensated online by an adaptive sliding mode mechanism, and as an important parameter for constructing harsh environments in numerical simulations.

[0093] In the field of aircraft navigation and guidance, mathematical models of wind disturbance are used to describe the characteristics of different wind speed variations. The following are three common mathematical models of wind disturbance and their characteristics.

[0094] (1) Gust Model: Gusts refer to short-term sudden changes in wind speed, usually caused by atmospheric turbulence or topographic disturbance. Its mathematical model is divided into the step model and the cosine model. The former simply represents the instantaneous increase in wind speed, but does not conform to the actual gradual change characteristics, while the latter is closer to the gradual change process of actual gusts. The two mathematical models are shown below.

[0095] ;

[0096] ;

[0097] in This indicates the change in wind speed over time. Let T be the step value, and T be the period of the cosine variation.

[0098] (2) Wind shear model: The change of wind speed with altitude or horizontal distance is commonly seen during takeoff and landing or in wind farms. The two mathematical models of vertical wind shear (exponential law) and horizontal wind shear (linear model) are as follows.

[0099] ;

[0100] z represents the height. For reference wind speed, This is the surface roughness coefficient.

[0101] ;

[0102] Where k is the shear gradient and x is the horizontal distance.

[0103] (3) Horizontal wind model: Includes mean wind speed and random turbulence components to simulate the randomness of natural wind. Turbulence is described by power spectral density:

[0104] ;

[0105] L is the turbulence scale. For wind speed standard deviation, The frequency is used. In practical applications, random wind speed sequences are generated by passing white noise through a shaping filter (such as a second-order filter).

[0106] Wind disturbance and model uncertainty are equivalent to disturbance terms acting on the line-of-sight dynamics. Linear perturbation is imminent. Projecting onto the horizontal / vertical normal yields And the model uncertainty and the attitude-velocity coupling effect caused by angular acceleration are expressed as Therefore, the dynamic equation can be written as:

[0107] ;

[0108] in, and It is a lumped disturbance in the guidance process, and its amplitude is usually assumed to be bounded.

[0109] Step S12: Construct target recursive sliding surfaces in the horizontal channel and the vertical channel respectively. In the horizontal channel and the vertical channel, construct equivalent control terms according to the corresponding target recursive sliding surfaces respectively. Generate switching compensation terms for the sliding controller according to external disturbances. The equivalent control terms are the control quantities obtained when the derivative of the target recursive sliding surface is zero.

[0110] In this embodiment, a target recursive sliding surface is constructed in the horizontal channel and the vertical channel, respectively, including: constructing a first sliding surface in the horizontal channel and the vertical channel based on the corresponding guidance error; wherein, the first sliding surface is a fast non-singular terminal sliding surface; adding a target integral term to the first sliding surface to obtain the second sliding surface corresponding to the horizontal channel and the vertical channel respectively; setting the value of the second sliding surface at the initial guidance moment to zero; and constructing the target recursive sliding surface using the first sliding surface and the corresponding second sliding surface.

[0111] Specifically, step 2, the UAV dynamic target guidance algorithm based on recursive adaptive sliding mode:

[0112] 2.1 Design of Recursive Sliding Mode Guide Law:

[0113] Based on the horizontal and vertical decomposition of the 3D guidance model, with the target line angle , As a reference signal, the pilot angle is set. , The dynamic tracking problem is constructed as two independent control channels. First, the guidance error is defined:

[0114] ;

[0115] ;

[0116] Where k is the proportional guidance factor, which is used to track the proportionality of the guidance angle during the guidance process, amplify the body response, enhance the lateral response sensitivity under highly maneuverable target conditions, and ensure that the guidance error can converge in a finite time within a larger convergence domain, thereby improving the acquisition capability in the initial segment.

[0117] Centralized interference The boundedness of a property can be defined as:

[0118] ;

[0119] ;

[0120] in, , , , , , These are the gain coefficients used to estimate the disturbance, and all are taken as positive values; The error between the guide angle and the target line angle in the horizontal plane, The error between the guiding angular velocity and the target angular velocity in the horizontal plane, The error value between the guide angle and the target line angle in the vertical plane. This represents the error between the guiding angular velocity and the target angular velocity in the vertical plane.

[0121] For the horizontal channel, in order to obtain a robust guidance law with finite-time convergence, a fast non-singular terminal sliding surface is introduced. As the first layer of hierarchical sliding mode structure (i.e., the first sliding surface), its form is as follows:

[0122] ;

[0123] Where k>0, >0, >0 represents the convergence coefficients of each derivative, used to adjust the convergence rate and adaptability to nonlinear maneuvers. To further avoid the non-negligible arrival phase in traditional sliding mode control and improve the transient performance of guidance errors, a first-layer sliding surface... Based on this, an internal integral (i.e., the target integral) is introduced. A second-layer integral recursive sliding mode structure (i.e., the second sliding surface) is constructed. The internal integral quantity... The derivative satisfies the following condition:

[0124] ;

[0125] And define the second sliding surface. This forms a recursive integral sliding mode structure:

[0126] ;

[0127] in >0 represents the recursive coupling gain. This is achieved by setting the initial integral value to satisfy:

[0128] ;

[0129] Can make =0, thus effectively weakening the existence of the sliding mode arrival stage, allowing the guidance error to work under the sliding mode dynamics constraint from the initial moment, achieving fast and smooth guidance angle approximation characteristics.

[0130] In practical applications, the horizontal angle during guidance is observable, therefore:

[0131] ;

[0132] Sliding surface The derivative is:

[0133] ;

[0134] By setting =0, and combined with the relative motion equation of the guide, the following equivalent guide control law can be obtained.

[0135] ;

[0136] For the vertical channel, in order to obtain a robust guidance law with finite-time convergence, a fast non-singular terminal sliding surface is introduced. As the first layer of hierarchical sliding mode structure, its form is as follows:

[0137] ;

[0138] Where k>0, >0, >0 represents the convergence coefficients of all derivatives, used to adjust the convergence rate and adaptability to nonlinear maneuvers. To further avoid the non-negligible arrival phase in traditional sliding mode control and improve the transient performance of guidance errors, a second-layer integral recursive sliding mode structure is constructed based on the first-layer sliding surface, by introducing internal integral quantities. Its derivative satisfies:

[0139] ;

[0140] And define the second sliding surface:

[0141] ;

[0142] Where λ>0 is the recursive coupling gain. The initial value of the integral is set to satisfy:

[0143] ;

[0144] Can make =0, thus effectively weakening the existence of the sliding mode arrival stage, allowing the guidance error to work under the sliding mode dynamics constraint from the initial moment, achieving fast and smooth guidance angle approximation characteristics.

[0145] ;

[0146] Sliding surface The derivative is:

[0147] ;

[0148] By setting =0, and combined with the relative motion equation of the guide, the following equivalent guide control law for the vertical channel can be obtained.

[0149] ;

[0150] In addition, in this embodiment, generating the switching compensation term of the sliding mode controller based on external disturbances includes: evaluating the upper bound of the disturbance of the target acceleration to obtain the corresponding target estimate, and constructing the switching compensation term of the sliding mode controller based on the target estimate and the target recursive sliding surface; wherein, the target acceleration is the equivalent acceleration caused by external disturbances and the maneuvering behavior of guiding the target.

[0151] 2.2 Adaptive Gain and Parameter Estimation Mechanism:

[0152] During guidance, the system is inevitably affected by a combination of external disturbances, equivalent acceleration changes introduced by target maneuvers, sensor noise, and model uncertainties. Because the actual disturbances are unknown and time-varying, even if the initial values ​​of the sliding surfaces for both channels are guaranteed through the design of recursive integral sliding surfaces at the initial moment... =0 and =0, the system state will still deviate from the sliding surface under external disturbances, resulting in reduced tracking accuracy. To enhance the ability to maintain the sliding surface and improve overall robustness, an additional switching compensation control quantity (i.e., switching compensation term) needs to be constructed in addition to the equivalent control.

[0153] ;

[0154] ;

[0155] in It is a generalized form of the traditional sliding mode reaching law, capable of... Provides rapid recovery when deviating from the sliding surface; exponential term It can provide less chattering near the sliding mode and stronger convergence when the sliding mode is far away, achieving segmented enhanced convergence behavior with fast and slow convergence when the sliding mode is near.

[0156] An adaptive estimation compensation is used to address the upper bound of the disturbance. This is due to the equivalent disturbance term in the line-of-sight angle dynamics. Having the characteristics of being unknown, time-varying, and coupled with relative error, this invention is based on the structured boundedness of the perturbation bound.

[0157] ;

[0158] Constructed parameters The design enables online estimation of disturbance intensity based on real-time guidance error, allowing the compensation term to automatically increase when the disturbance is large and decrease when the disturbance decreases. This effectively avoids the overcompensation and strong chattering problems commonly found in fixed-gain sliding mode control.

[0159] They are respectively The estimated value. Parameters Update according to the corresponding adaptive law.

[0160] ;

[0161] in , and For positive integers, The initial value is designed to be 0. Finally, the dynamic target guidance law based on recursive adaptive sliding mode is constructed as follows:

[0162] ;

[0163] The control structure of the recursive adaptive sliding membrane proposed in this embodiment is as follows: Figure 3 As shown, it includes non-singular terminal sliding surfaces, integral recursive sliding surfaces, and adaptive rates.

[0164] Step S13: In the vertical channel, the gravity compensation term of the UAV is determined based on the pitch attitude of the UAV, and the corresponding landing angle offset control amount is calculated according to the landing angle constraint of the UAV.

[0165] In this embodiment, determining the gravity compensation term of the UAV based on its pitch attitude includes: determining the pitch attitude of the UAV, determining the projection component of gravity in the normal direction of the vertical channel based on the pitch attitude, and determining the gravity compensation term based on the projection component.

[0166] Specifically, step 3 involves considering guided modifications to safety constraints:

[0167] In actual flight, UAVs not only need to achieve rapid and robust tracking of maneuvering targets, but also must meet flight safety constraints, such as gravity impact compensation in the initial stage and the landing angle constraint required during the terminal approach. To this end, this step further introduces two types of constraint correction quantities based on the aforementioned sliding mode guidance law, so that the guidance commands have better physical feasibility and terminal control capability.

[0168] 3.1 Initial Gravity Compensation:

[0169] In the guidance of maneuvering targets by UAVs, the rate of change of the vertical line-of-sight angle is a key factor determining 3D tracking performance. However, fixed-wing UAVs are often affected by problems such as incomplete aerodynamic state establishment, insufficient angle of attack, or flattened attitude in the early stages of flight, resulting in significantly insufficient normal acceleration in the vertical direction. Especially under small bank flight conditions, the lift contribution cannot offset the projection of gravity, causing the line-of-sight angle in the vertical channel to exhibit "initial response hysteresis." If left untreated, although the sliding mode guidance law can converge theoretically, its arrival phase will be significantly prolonged, and it may even deviate from the sliding surface at the initial moment, increasing guidance error, causing the controller to enter a high-amplitude switching mode, and leading to unnecessary control chatter. Therefore, the influence of gravity on the vertical line-of-sight angle must be compensated for in an explicit and analytical manner in the guidance law.

[0170] Based on the line-of-sight (LOS) guidance dynamics derived in step 1, regardless of the target's state, the acceleration term of the second-order equation for the vertical LOS can be decomposed into a controllable term (normal acceleration generated by lift) and an uncontrollable term (gravity projection). The vertical equivalent normal acceleration of the UAV satisfies:

[0171] ;

[0172] in This is the component of gravity along the vertical normal direction (i.e., the projected component of gravity along the normal direction of the vertical channel). This term always acts in the line-of-sight dynamics, is independent of target acceleration and geometric terms, and is a definite disturbance component. Upon initial entry into the guidance area, if the UAV's angle of attack has not yet been established... The effective value is often small, and at this time, the actual controllable acceleration of the system is severely canceled out by the gravity term, resulting in a decrease in the vertical change rate of the line-of-sight angle. It is difficult to meet the requirements of the sliding mode reaching law. Based on this physical fact, the present invention treats the gravity term as a modelable perturbation and introduces it into the guiding law as a separate compensation term, so that it is equivalently canceled at the moment the system begins to guide, thereby enabling the sliding surface to immediately enter the effective convergence region.

[0173] In this embodiment, the acceleration command in the recursive sliding mode guidance law consists of two parts, namely the equivalent control term. With switch compensation item Treating the gravity term directly as an unknown disturbance and handling it through the switching term would not only introduce additional chattering but also waste adaptive compensation bandwidth. Therefore, a more reasonable approach is to isolate the gravity term as a "resolvable known disturbance" and include it in the command channel. Based on this, this embodiment constructs a gravity compensation term for the vertical channel:

[0174] ;

[0175] Its physical meaning is to use the gravity normal projection updated in real time with the UAV's pitch attitude to actively cancel out the uncontrollable parts of the line-of-sight dynamics. Based on this, the command acceleration of the vertical channel is corrected as follows:

[0176] ;

[0177] By Explicitly incorporating a command control law effectively reduces the equivalent disturbance term in line-of-sight dynamics, ensuring that the remaining disturbance only includes unmodelable components such as environmental wind disturbance, aerodynamic uncertainties, and sensor noise. Since gravity is a deterministic term, this compensation not only reduces the arrival time of the sliding mode approach phase but also lowers the requirement for adaptive gain, thus reducing chattering in actual control. Furthermore, because gravity compensation and the equivalent sliding mode control are parallel rather than interchangeable, it does not alter the definition of the sliding surface or disrupt the finite-time convergence characteristics of fast non-singular terminal sliding modes. The system's sliding mode structure, guidance error dynamics, and disturbance upper bound estimation mechanism remain unchanged; only the fixed disturbance component in line-of-sight dynamics is preemptively removed from the unknowns, allowing the robustness of the sliding mode algorithm to be used for genuine unpredictable disturbances rather than to compensate for constant gravity.

[0178] Furthermore, since the tracking law of this embodiment has a nonlinear amplification effect compared to proportional guidance, its proportional guidance factor k plays a role similar to the amplification coefficient in the traditional proportional guidance method. This ensures that the dynamic energy after vertical channel compensation converges within a finite time.

[0179] For pure proportional guidance, the UAV's normal overload It is proportional to the line-of-sight angular velocity. Based on the above two equations, the expression for normal overload is derived:

[0180] ;

[0181] Considering the influence of gravity on the aircraft during operation, a gravity compensation term is added to the control commands to achieve a compensation effect, resulting in the following form:

[0182] ;

[0183] The range of values ​​for the proportional guidance factor k is given below. First, the variation of the line-of-sight angle needs to be analyzed. According to step 1, we can obtain:

[0184] ;

[0185] Ignoring changes in the vector velocities of the UAV and the target, the second derivative of the line-of-sight angle change can be derived:

[0186] ;

[0187] To ensure that the designed guidance law can hit the target in a shorter time and with a smaller miss distance, its trajectory needs to be relatively flat. According to the definition of the derivative, the second derivative can be understood as the rate of change of the first derivative. The above formula will be discussed in detail below. Then q and With opposite signs, when the first derivative is positive, its rate of change continuously decreases, and the first derivative will tend to zero. When the first derivative is negative, the second derivative is positive, and the absolute value of the derivative also tends to zero with time. Therefore, in q and The rate of change of the line-of-sight angle converges when the signs are opposite; if If both remain in the same sign, then the rate of change of the line-of-sight angle diverges. To ensure the trajectory is as straight as possible, convergence conditions must be met; therefore, the range of the proportionality coefficient can be derived:

[0188] ;

[0189] This ensures that the line-of-sight angle does not diverge in the dynamics after gravity compensation, and further enhances the stability in the initial stage.

[0190] Furthermore, in this embodiment, the corresponding landing angle offset control amount is calculated based on the landing angle constraint of the UAV, including: calculating the landing angle offset control amount based on the difference between the landing angle constraint and the current line of sight angle, the remaining flight time of the UAV, and the relative motion relationship between the UAV and the guided target.

[0191] Specifically, 3.2, Corner Constraints:

[0192] In most UAV precision strike missions, simply tracking and intercepting maneuvering targets in space is insufficient; it is often necessary to further satisfy the terminal landing angle constraints required by the mission, such as vertical strikes, downward attacks, and specified penetration angles. These terminal angle requirements are essentially constraints on the UAV's velocity direction at the moment of strike. Since the velocity direction has a geometric relationship with the line-of-sight angle, discrete acceleration bias methods (such as adding a constant acceleration term in traditional proportional guidance) cannot adapt to complex maneuvering targets and nonlinear sliding mode guidance structures. This invention transforms the landing angle constraint into a gradual correction of the guidance angle reference trajectory, making the desired landing angle a part of the target state tracked by the sliding mode guidance law, rather than forcibly pulled by an external overload bias. This makes the implementation of the landing angle constraint not only theoretically controllable and dynamically smooth, but also easier to integrate with recursive sliding mode structures, without causing disturbance term bursts or convergence failures.

[0193] First, consider the vertical channel line-of-sight dynamics given in step 1:

[0194] ;

[0195] in Control torque Obtained through aerodynamic mapping. The aforementioned recursive sliding mode control law has been constructed with equivalent terms. To approximate the desired line-of-sight acceleration And through the switch item With gravity compensation term The error is guaranteed to converge within a finite time. However, to satisfy the terminal condition... An additional bias needs to be injected into the reference line-of-sight angle acceleration to ensure that the line-of-sight angle trajectory in the integral sense satisfies specific boundary conditions.

[0196] Therefore, the true line-of-sight acceleration of the vertical channel is expressed as the sum of the reference value and the offset value:

[0197] ;

[0198] in This is the bias term introduced to achieve the terminal landing angle. Integrating the above equation over the entire guidance time, combined with the terminal conditions, we get:

[0199] ;

[0200] By rearranging the first-order integral term, we can obtain the integral constraint for the bias term:

[0201] ;

[0202] The above equation can be approximated as the product of the bias term and the remaining flight time. According to equation (1), an approximate solution for the remaining flight time can be obtained:

[0203] ;

[0204] in For the remaining flight time, This represents the line-of-sight angle gap that needs to be filled to reach the terminal landing angle. Combining guidance geometry, the remaining flight time is given by the relative distance and relative radial velocity:

[0205] ;

[0206] In the formula, the subscripts 0 and f represent the initial and final times of the UAV's operation, respectively. Given the remaining flight time, based on the missile-target motion relationship, at the moment the UAV strikes the target, the missile-target tilt angle is consistent with the missile-target line-of-sight angle:

[0207] ;

[0208] Define a function:

[0209] ;

[0210] The second term is a reasonable first-order prediction of the integral term of the future reference line-of-sight angle acceleration, thus yielding the analytical form of the instantaneous bias:

[0211] ;

[0212] In practical control, the bias term needs to be transformed into the control torque of the vertical channel through body dynamics mapping. Ultimately, the guided correction of the landing angle constraint can be naturally incorporated into the recursive adaptive sliding mode control law of the vertical channel, forming the following complete form:

[0213] ;

[0214] This model employs a static wind field modeling method with independent and uniform distribution across three axes. Headwind, crosswind, and vertical wind components are randomly generated within preset extreme ranges, and uniform wind speed sampling is achieved through linear transformation. The model structure is simple and efficient; although it does not consider the spatiotemporal dynamics of the wind field, it can quickly cover extreme wind speed conditions. Its core feature is low computational complexity, making it suitable for boundary condition analysis in large-scale Monte Carlo simulations and providing basic wind disturbance input for miss rate assessment.

[0215] Step S14: Superimpose the equivalent control term, the switch compensation term, the gravity compensation term, and the landing angle offset control term to obtain the target guidance command, and use the target guidance command to guide the UAV.

[0216] In this embodiment, the equivalent control term, switch compensation term, gravity compensation term, and landing angle offset control term are superimposed to obtain the target guidance command. This includes: in the horizontal channel, superimposing the equivalent control term and switch compensation term to generate a horizontal channel guidance command; in the vertical channel, superimposing the equivalent control term, switch compensation term, gravity compensation term, and landing angle offset control term to generate a vertical channel guidance command; and using the horizontal channel guidance command and the vertical channel guidance command to generate the target guidance command.

[0217] The specific process can be seen in the following formula and corresponding discussion, and will not be repeated here:

[0218] ;

[0219] ;

[0220] In this embodiment, a dynamic target is used as an example to guide the target. The initial position, velocity, and acceleration of the dynamic target are as follows:

[0221] ;

[0222] Meanwhile, the interference model is set as follows:

[0223] (1) Simplified wind disturbance model:

[0224] Wind speeds in all directions follow a uniform distribution:

[0225] ;

[0226] in, Maximum values ​​for tailwind and headwind; Maximum crosswind value; : Maximum wind shear; : A random value between 0 and 1.

[0227] This model employs a static wind field modeling method with independent and uniform distribution across three axes. Headwind, crosswind, and vertical wind components are randomly generated within preset extreme ranges, and uniform wind speed sampling is achieved through linear transformation. The model structure is simple and efficient; although it does not consider the spatiotemporal dynamics of the wind field, it can quickly cover extreme wind speed conditions. Its core feature is low computational complexity, making it suitable for boundary condition analysis in large-scale Monte Carlo simulations and providing basic wind disturbance input for miss rate assessment.

[0228] (2) Gyroscope noise modeling:

[0229] Gyroscope noise follows a Gaussian distribution:

[0230] ;

[0231] Noise power:

[0232] ;

[0233] in, This is the gyroscope output value; This is the actual value of the gyroscope; This represents noise power.

[0234] This model decomposes noise into two channels: measurement noise and sensitive axis noise. A noise power base is generated using uniformly distributed random numbers, and Gaussian white noise is superimposed on the angular velocity measurement. A separate parameter design is employed, with two independent upper limit parameters controlling the noise intensity. The model's advantage lies in its ability to effectively simulate the core error sources of the IMU with a minimalist structure, balancing computational efficiency and physical plausibility, making it particularly suitable for robustness verification of control systems.

[0235] (3) Aerodynamic coefficient deviation modeling:

[0236] ;

[0237] in, Minimum scaling factor; : Maximum scaling factor.

[0238] This deviation is in the form of a scaling factor, and its application is as follows:

[0239] ;

[0240] in, The aerodynamic coefficient after aerodynamic pull, For the original aerodynamic coefficient, This is the aerodynamic coefficient pull factor.

[0241] Influence coefficients include lift coefficients drag coefficient Pitch moment coefficient wait.

[0242] The aerodynamic calculation equations are as follows:

[0243] ;

[0244] Where F represents aerodynamic force, Where is atmospheric density, S is the windward area, and C is the original aerodynamic coefficient.

[0245] This embodiment uses a uniform perturbation model based on a global scaling factor to generate a single random deviation coefficient within a fixed range, simultaneously scaling all aerodynamic parameters. By setting a broad perturbation boundary, it covers extreme operating conditions ranging from performance degradation to enhancement. Its core value lies in achieving envelope analysis of aerodynamic uncertainties with minimal computational cost, prominently manifested in its extremely simple model structure (single random sampling), making it an effective tool for system-level sensitivity studies.

[0246] Dynamic target guidance was performed using the direct tracking method, the proportional guidance method, and the method proposed in this patent, respectively. The guidance results of the three methods are as follows:

[0247] like Figure 4 As shown, all three methods can achieve stable tracking, and the overall trajectories are relatively smooth. The direct tracking method can quickly approach the target in 3D space with a simple trajectory, but due to the lack of vertical channel gravity compensation, its Z-axis response in the initial stage is relatively lagging; furthermore, the lack of a landing angle constraint at the end causes the final approach direction to deviate from the current heading, making it difficult to meet specific landing angle requirements. The proportional guidance method exhibits good 3D trajectory smoothness, but requires a longer convergence time and a relatively longer trajectory path when the initial deflection angle is large. The recursive adaptive sliding mode method in this embodiment, through the rapid convergence of recursive sliding mode, the strong robustness of adaptive compensation, and the terminal shaping of landing angle constraints, makes the entire 3D trajectory fast, stable, and controllable in terms of task constraints at the beginning, middle, and end, resulting in the best overall trajectory quality among the three methods.

[0248] In addition, such as Figure 5As shown, the direct tracking method has a short path, fast turning, and a relatively smooth overall trajectory, but it still has a certain amount of lateral adjustment when the initial deflection angle is large. The proportional guidance method has a smoother planar trajectory, but due to its limited response speed, the path is usually longer than that of the direct tracking method. Under the action of the recursive sliding mode structure, the method of this patent can quickly establish a reasonable planar turn, with a compact mid-section path, small lateral deviation, and adaptive compensation that maintains high stability when maneuvering towards the target. Therefore, the XY planar trajectory is relatively compact, and the heading can be adjusted in time during the final landing angle stage, so that the landing angle is basically parallel to the target.

[0249] Therefore, this application achieves precise compensation for nonlinear coupling by constructing a target recursive sliding surface and building an equivalent control term, eliminating the arrival stage of traditional sliding mode and ensuring rapid error convergence; by generating a switching compensation term based on external disturbances, it achieves dynamic robust suppression of target maneuvers and environmental disturbances, reducing chattering; by introducing a gravity compensation term in the vertical channel, it overcomes the response hysteresis caused by gravity in the initial stage; by calculating the landing angle offset control quantity based on the landing angle constraint, it achieves precise control of the terminal landing angle; finally, it superimposes the various control quantities to obtain the target guidance command, enabling the UAV to achieve high-precision guidance in complex environments.

[0250] See Figure 6 As shown, this embodiment of the invention discloses a UAV guidance device based on recursive sliding mode, comprising:

[0251] The channel decomposition module 11 is used to establish a relative motion model between the UAV and the dynamic target, and decompose the UAV's guidance channel into a horizontal channel and a vertical channel based on the relative motion model.

[0252] The sliding surface construction module 12 is used to construct target recursive sliding surfaces in the horizontal channel and the vertical channel respectively, construct equivalent control terms in the horizontal channel and the vertical channel according to the corresponding target recursive sliding surfaces respectively, and generate switching compensation terms of the sliding controller according to external disturbances; the equivalent control terms are the control quantities obtained when the derivative of the target recursive sliding surface is zero.

[0253] The gravity compensation term determination module 13 is used to determine the gravity compensation term of the UAV based on the pitch attitude of the UAV in the vertical channel, and to calculate the corresponding landing angle offset control amount according to the landing angle constraint of the UAV.

[0254] The UAV guidance module 14 is used to superimpose the equivalent control item, the switch compensation item, the gravity compensation item and the landing angle offset control quantity to obtain the target guidance command, and use the target guidance command to guide the UAV.

[0255] In some specific embodiments, the channel decomposition module 11 further includes:

[0256] The horizontal wind model building unit is used to build a gust model to describe the time-varying characteristics of wind speed, a wind shear model to describe the variation of wind speed with spatial location, and a horizontal wind model to describe the stochastic characteristics of natural wind.

[0257] An external disturbance determination unit is used to acquire wind disturbance data generated by the gust model, the wind shear model, and the horizontal wind model, and to determine the external disturbance based on the wind disturbance data.

[0258] In some specific embodiments, the sliding surface construction module 12 may specifically include:

[0259] A first sliding surface construction unit is used to construct a first sliding surface in the horizontal channel and the vertical channel respectively based on the corresponding guidance error; wherein, the first sliding surface is a fast non-singular terminal sliding surface;

[0260] The second sliding surface construction unit is used to add a target integral term to the first sliding surface to obtain the second sliding surfaces corresponding to the horizontal channel and the vertical channel respectively, set the value of the second sliding surface to zero at the initial guiding moment, and construct the target recursive sliding surface using the first sliding surface and the corresponding second sliding surface.

[0261] In some specific embodiments, the sliding surface construction module 12 may specifically include:

[0262] A switching compensation term construction unit is used to evaluate the upper bound of the disturbance of the target acceleration to obtain the corresponding target estimate, and to construct the switching compensation term of the sliding mode controller based on the target estimate and the target recursive sliding surface; wherein the target acceleration is the equivalent acceleration caused by external disturbance and the maneuvering behavior of guiding the target.

[0263] In some specific embodiments, the gravity compensation term determination module 13 may specifically include:

[0264] A gravity compensation term determination unit is used to determine the pitch attitude of the UAV, determine the projection component of gravity in the normal direction of the vertical channel based on the pitch attitude, and determine the gravity compensation term based on the projection component.

[0265] In some specific embodiments, the gravity compensation term determination module 13 may specifically include:

[0266] The landing angle offset control calculation unit is used to calculate the landing angle offset control quantity based on the difference between the landing angle constraint and the current line-of-sight angle, the remaining flight time of the UAV, and the relative motion relationship between the UAV and the guided target.

[0267] In some specific embodiments, the UAV guidance module 14 may specifically include:

[0268] The first instruction generation unit is used to superimpose the equivalent control item and the switch compensation item in the horizontal channel to generate a horizontal channel guidance instruction.

[0269] The second instruction generation unit is used to superimpose the equivalent control item, the switch compensation item, the gravity compensation item and the drop angle offset control quantity in the vertical channel to generate a vertical channel guidance instruction.

[0270] The target instruction generation unit is used to generate the target guidance instruction using the horizontal channel guidance instruction and the vertical channel guidance instruction.

[0271] Furthermore, embodiments of this application also disclose an electronic device, Figure 7 This is a structural diagram of an electronic device 20 according to an exemplary embodiment. The content of the diagram should not be construed as limiting the scope of this application.

[0272] Figure 7 This is a schematic diagram of the structure of an electronic device 20 provided in an embodiment of this application. Specifically, the electronic device 20 may include: at least one processor 21, at least one memory 22, a power supply 23, a communication interface 24, an input / output interface 25, and a communication bus 26. The memory 22 stores a computer program, which is loaded and executed by the processor 21 to implement the relevant steps in the UAV guidance method based on recursive sliding mode disclosed in any of the foregoing embodiments. Alternatively, the electronic device 20 in this embodiment may specifically be an electronic computer.

[0273] In this embodiment, the power supply 23 is used to provide operating voltage for each hardware device on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and external devices, and the communication protocol it follows can be any communication protocol applicable to the technical solution of this application, and is not specifically limited here; the input / output interface 25 is used to acquire external input data or output data to the outside world, and its specific interface type can be selected according to specific application needs, and is not specifically limited here.

[0274] In addition, the memory 22, as a carrier for resource storage, can be a read-only memory, random access memory, disk or optical disk, etc. The resources stored thereon can include operating system 221, computer program 222, etc., and the storage method can be temporary storage or permanent storage.

[0275] The operating system 221 is used to manage and control the various hardware devices on the electronic device 20 and the computer program 222, which may be Windows Server, Netware, Unix, Linux, etc. In addition to including a computer program capable of performing the recursive sliding mode-based UAV guidance method executed by the electronic device 20 as disclosed in any of the foregoing embodiments, the computer program 222 may further include computer programs capable of performing other specific tasks.

[0276] Furthermore, this application also discloses a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, it implements the aforementioned recursive sliding mode-based UAV guidance method. Specific steps of this method can be found in the corresponding content disclosed in the foregoing embodiments, and will not be repeated here.

[0277] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0278] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0279] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0280] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0281] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A UAV guidance method based on recursive sliding mode, characterized in that, include: Establish a relative motion model between the UAV and the dynamic target, and decompose the UAV's guidance channel into a horizontal channel and a vertical channel based on the relative motion model; Target recursive sliding surfaces are constructed in the horizontal channel and the vertical channel respectively. In the horizontal channel and the vertical channel, equivalent control terms are constructed according to the corresponding target recursive sliding surfaces. Switching compensation terms of the sliding controller are generated according to external disturbances. The equivalent control terms are the control quantities obtained when the derivative of the target recursive sliding surface is zero. In the vertical channel, the gravity compensation term of the UAV is determined based on the pitch attitude of the UAV, and the corresponding landing angle offset control amount is calculated according to the landing angle constraint of the UAV. The equivalent control term, the switch compensation term, the gravity compensation term, and the landing angle offset control term are superimposed to obtain the target guidance command, and the target guidance command is used for UAV guidance.

2. The UAV guidance method based on recursive sliding mode according to claim 1, characterized in that, After establishing the relative motion model between the UAV and the dynamic target, the following is also included: Construct a gust model to describe the time-varying characteristics of wind speed, a wind shear model to describe the variation of wind speed with spatial location, and a horizontal wind model to describe the stochastic characteristics of natural wind. The wind disturbance data generated by the gust model, the wind shear model, and the horizontal wind model are obtained, and the external disturbance is determined based on the wind disturbance data.

3. The UAV guidance method based on recursive sliding mode according to claim 1, characterized in that, The construction of target recursive sliding surfaces in the horizontal channel and the vertical channel respectively includes: In the horizontal channel and the vertical channel, a first sliding surface is constructed based on the corresponding guidance error; wherein, the first sliding surface is a fast non-singular terminal sliding surface; Add a target integral term to the first sliding surface to obtain the second sliding surfaces corresponding to the horizontal channel and the vertical channel respectively. Set the value of the second sliding surface to zero at the initial guiding moment, and construct the target recursive sliding surface using the first sliding surface and the corresponding second sliding surface.

4. The UAV guidance method based on recursive sliding mode according to claim 1, characterized in that, The method for generating the switching compensation term of the sliding mode controller based on external disturbances includes: The upper bound of the disturbance of the target acceleration is evaluated to obtain the corresponding target estimate, and the switching compensation term of the sliding mode controller is constructed based on the target estimate and the target recursive sliding surface; wherein, the target acceleration is the equivalent acceleration caused by external disturbance and the maneuvering behavior of guiding the target.

5. The UAV guidance method based on recursive sliding mode according to claim 1, characterized in that, The method for determining the gravity compensation term of the UAV based on its pitch attitude includes: The pitch attitude of the UAV is determined, the projection component of gravity in the normal direction of the vertical channel is determined based on the pitch attitude, and the gravity compensation term is determined based on the projection component.

6. The UAV guidance method based on recursive sliding mode according to claim 1, characterized in that, The calculation of the corresponding landing angle offset control value based on the landing angle constraint of the UAV includes: The landing angle offset control value is calculated based on the difference between the landing angle constraint and the current line-of-sight angle, the remaining flight time of the UAV, and the relative motion relationship between the UAV and the guided target.

7. The UAV guidance method based on recursive sliding mode according to claim 1, characterized in that, The step of superimposing the equivalent control term, the switch compensation term, the gravity compensation term, and the landing angle offset control value to obtain the target guidance command includes: In the horizontal channel, the equivalent control term and the switch compensation term are superimposed to generate a horizontal channel guidance command; In the vertical channel, the equivalent control term, the switch compensation term, the gravity compensation term, and the drop angle offset control term are superimposed to generate a vertical channel guidance command; The target guidance command is generated using the horizontal channel guidance command and the vertical channel guidance command.

8. A UAV guidance device based on recursive sliding mode, characterized in that, include: The channel decomposition module is used to establish a relative motion model between the UAV and the dynamic target, and decompose the UAV's guidance channel into a horizontal channel and a vertical channel based on the relative motion model. A sliding surface construction module is used to construct target recursive sliding surfaces in the horizontal channel and the vertical channel respectively, construct equivalent control terms in the horizontal channel and the vertical channel according to the corresponding target recursive sliding surfaces, and generate switching compensation terms for the sliding controller according to external disturbances; the equivalent control terms are the control quantities obtained when the derivative of the target recursive sliding surface is zero; The gravity compensation term determination module is used to determine the gravity compensation term of the UAV based on the pitch attitude of the UAV in the vertical channel, and to calculate the corresponding landing angle offset control amount according to the landing angle constraint of the UAV. The UAV guidance module is used to superimpose the equivalent control item, the switch compensation item, the gravity compensation item, and the landing angle offset control quantity to obtain the target guidance command, and to use the target guidance command to guide the UAV.

9. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the UAV guidance method based on recursive sliding mode as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, Used to store a computer program, which, when executed by a processor, implements the UAV guidance method based on recursive sliding mode as described in any one of claims 1 to 7.

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