Hierarchical terminal sliding mode control method of four-rotor unmanned aerial vehicle hanging system based on preset performance
By employing a layered terminal sliding mode control method, the load swaying problem in the quadcopter UAV sling system was solved, enabling rapid positioning and anti-swaying of the sway angle, thus improving the safety and reliability of transportation.
Patent Information
- Application Number
- CN202511541605.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-27
- Publication Date
- 2026-01-13
Smart Images
Figure CN121325918A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of quadcopter drone sling control technology, and in particular to a layered terminal sliding mode control method for a quadcopter drone sling system based on preset performance. Background Technology
[0002] In recent years, thanks to the rapid development of electronic control and embedded technologies, quadcopter drones have begun to be widely used. Among these, payload capacity is one of the core capabilities enabling their widespread application. The ability of drones to carry suspended loads can bring significant benefits to various applications in construction, law enforcement, and agriculture. In particular, drone delivery services have already begun pilot programs in some areas of China. Quadcopter drone sling systems can handle various load loading and unloading issues because the suspension point of the rope is generally located near the drone's center of gravity, minimizing the impact of the suspended load on the drone's center of gravity, moment of inertia, and other parameters. The system can carry loads of different volumes, shapes, and masses. Therefore, the versatility of using sling loads on quadcopter drones makes research on quadcopter drone sling systems highly significant.
[0003] Traditional quadcopter control algorithms primarily target rigid loads or self-attitude stability. However, a sling system is essentially a typical underactuated, strongly coupled, multi-rigid-body system. The core problems are: 1. The suspended load generates uncontrollable swaying during UAV maneuvers. This swaying not only reduces the positioning accuracy and stability of the transport mission but may also react against the UAV itself, causing system instability or even crashes; 2. The system's dynamic model contains numerous uncertainties, including unknown or changing load mass, external environmental interference (such as wind disturbance), and system parameter perturbations caused by changes in sling length; 3. The UAV provides only six degrees of freedom of control force / torque through its four rotors, while the load's swaying degree of freedom cannot be directly controlled and must be indirectly suppressed through the movement of the UAV itself, significantly increasing the complexity of controller design.
[0004] To address these issues, researchers both domestically and internationally have proposed various control strategies, but all have certain limitations: Linear control methods (such as PID and LQR) are simple in structure and easy to implement, but they are usually based on linearized models near the system's operating point. The strong nonlinearity and large-range swaying of the suspension system can cause the system to move far from the operating point, leading to a sharp decline in the performance of the linear controller, insufficient robustness, and difficulty in effectively suppressing swaying; Conventional sliding mode control (SMC) has attracted attention due to its inherent strong robustness to matching uncertainties and can effectively handle model errors and external disturbances. However, traditional linear sliding surfaces can only achieve asymptotic convergence (the convergence time is theoretically infinite), which cannot meet the urgent needs of suspension systems for fast convergence and high-precision control.
[0005] In summary, the main drawback of the existing technology is the lack of a control method that can strictly guarantee the tracking error and sway performance of the suspension system in both transient and steady-state phases, converge quickly within a finite time, and simultaneously possess strong robustness and low chattering characteristics. Summary of the Invention
[0006] This invention simulates and verifies the theoretical quadrotor UAV sling transport control method and analyzes its control performance. It then applies this method to quadrotor UAV sling systems, better replacing the experience-based operation of technicians, continuously reducing errors caused by human factors, addressing the limitations of manual control methods in handling harsh environments, and resolving load sway issues generated during UAV flight, thereby improving transport safety and reliability. This invention proposes a layered terminal sliding mode control method for quadrotor UAV sling systems based on preset performance, achieving precise positioning and sway angle elimination control during transport.
[0007] To solve the above problems, the present invention adopts the following technical solution: A hierarchical terminal sliding mode control method for a quadrotor UAV sling system based on preset performance includes the following steps: S1. Using Lagrange equations and dynamic analysis, a dynamic model of the quadrotor UAV sling system with external disturbances is established. The error is defined by comparing the desired trajectory with the established dynamic model. Using a pre-defined performance method, the boundary-constrained error *e* in the original system is mapped to a new unconstrained variable. This enables the transformation of errors in the quadcopter drone's mounting system. S2. Based on the model of the quadcopter UAV sling system after error transformation, the sliding mode control method of the terminal is adopted to design the sliding mode surface of the system. Due to the coupling relationship between the displacement in the x-direction and the swing angle, the idea of layered sliding mode is adopted to design the sub-sliding mode surface and the total sliding mode surface. S3. Combining the quadcopter UAV sling system after error transformation in step S1 and the sliding surface designed in step S2, the controllers in the z and x directions of the system are calculated. Based on this, an adaptive law is designed to improve the robustness of the system against unknown disturbances, and finally the accurate positioning and anti-sway control of the quadcopter UAV sling system are achieved.
[0008] As a further optimization of the aforementioned hierarchical terminal sliding mode control method for a quadrotor UAV sling system based on preset performance, in step S1, the dynamic model of the quadrotor UAV sling system containing external disturbances, established based on the Lagrange equation, is as follows: , in , Indicates the drone's altitude. This represents the displacement of the drone in the x-direction. Let M represent the swing angle of the suspended load, m represent the mass of the UAV, m represent the mass of the suspended load, l represent the length of the suspension rope, g represent the acceleration due to gravity, and d represent external disturbances. Based on this formula, the following is defined: , , , , , , Then, regarding the error Introduce a preset performance function Convert the error to: , in , , .
[0009] As a further optimization of the hierarchical terminal sliding mode control method for a quadrotor UAV sling system based on preset performance, in step S2, the sliding mode surface function of the terminal sliding mode controller is constructed as follows. , In step S2, due to the coupling relationship between the x-displacement and the swing angle, the recursive terminal sliding surface and the overall sliding surface are designed as follows: , in , , The coefficient to be designed.
[0010] As a further optimization of the aforementioned layered terminal sliding mode control method for a quadcopter UAV sling system based on preset performance, in step S3, the design... It can be obtained The equivalent control law, , To address disturbances in the control law, an adaptive law is designed to eliminate the disturbances, and a setting is made. To estimate the disturbance, an adaptive law is designed as follows: , in These are the parameters to be designed; Choose the sliding mode convergence law: By designing a controller and combining it with an equivalent control law, we can obtain: , in , , , , which are the parameters to be designed.
[0011] Beneficial effects Compared with the prior art, the present invention has significant advantages and beneficial effects, achieving considerable technological progress and practicality, and possessing broad application value. It has at least the following advantages: This invention addresses the load swaying problem generated during transport in a quadcopter drone sling system. Based on a pre-defined performance error transformation method, it maps the "boundary-constrained" error 'e' in the original system to a new "unconstrained" variable, constructing a new mathematical model. Then, a controller based on hierarchical terminal sliding mode is designed for this new mathematical model, enabling the quadcopter drone sling system to simultaneously possess precise positioning and anti-sway characteristics.
[0012] The method of this invention enables the UAV sling system to stabilize more quickly at a designated location, and it can track the desired trajectory throughout the entire process. Furthermore, it effectively suppresses load sway during UAV transport, achieving precise system positioning and eliminating residual load sway. This faster and more effective elimination of sway demonstrates good robustness.
[0013] The method of this invention solves the problem of load swaying during drone sling transport, improves transport efficiency and stability, and provides a theoretical basis for safe and reliable drone sling transport. Attached Figure Description
[0014] Figure 1 A schematic diagram of a two-dimensional model of a quadcopter drone suspended by slings; Figure 2The displacement tracking curve in the z-direction of a UAV flying to an altitude of 8m; Figure 3 The displacement tracking curve of the UAV in the x-direction when it flies horizontally to a distance of 8m in the x-direction; Figure 4 The curve showing the change in the drone's load swing angle under a preset trajectory; Figure 5 Comparison curves of trajectory tracking errors of UAVs in the z-direction using different methods under a preset trajectory; Figure 6 Comparison curves of trajectory tracking errors of UAVs in the x-direction using different methods under a preset trajectory; Figure 7 Error comparison curves for different methods of load swing angle under a preset trajectory; Figure 8 Error comparison curves of different methods for applying pulse interference in the z-direction during level flight; Figure 9 Error comparison curves of different methods for applying pulse interference in the x-direction during level flight; Figure 10 The error comparison curves show different methods of applying pulse interference to the load swing angle during level flight. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of protection. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art, without creative effort, including formal modifications to the technical solutions described in the following embodiments or equivalent substitutions of some technical features, based on the inspiration of the present invention, are within the scope of protection of the present invention.
[0016] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0017] like Figure 1 As shown, this embodiment provides a layered terminal sliding mode control method for a quadcopter UAV sling system based on preset performance, including: Construct the hardware structure of a drone hoisting system with load swing effect; Based on the dynamic model of the UAV hoisting system with load swing effect, the mathematical expressions for the positions of the UAV and the load are written. The system is analyzed, rewritten as a radial nonlinear system, and the errors in the system model are converted to errors with preset performance.
[0018] For the system after error transformation, a hierarchical terminal sliding mode controller is designed, and an adaptive law is added to resist external disturbances. The resulting controller enables the UAV sling transport system to simultaneously possess the advantages of stable tracking, precise positioning, and anti-sway angle. The input signal is obtained by combining the system position information, swing angle information, and the controller. Driven by this input signal, the system achieves the dual objectives of system positioning and load stabilization.
[0019] In this embodiment, the hardware structure of the flying hoisting system with load swing effect mainly consists of the UAV body, the hoisting rope between the UAV and the load, and the load itself. Specifically, the quadcopter UAV is an F450 quadcopter UAV with a wheelbase of 450mm, the hoisting rope is a rigid lightweight rope, and the load is a 3D printed ball.
[0020] Step 1 This system is a quadcopter drone sling system, combined with... Figure 1 Create a suspended model of a quadcopter drone connected by lanyards, based on the Lagrange dynamics equations: , in, , , , These are the system state vector, the system inertial force matrix, the system centripetal Coriolis force matrix, and the gravitational potential energy matrix, respectively. For system control input; These are system resistance disturbances, and their specific forms are as follows: , , , , , , The dynamic model of the quadcopter UAV sling system with external disturbances is derived as follows.
[0021] , Combination Figure 1 Select For an inertial coordinate system in the longitudinal plane, any point in the longitudinal plane is chosen as the origin of the inertial coordinate system. ; direction parallel to This refers to the direction of the drone's horizontal speed, and also the direction in which the load swings forward; Perpendicular to And it points in the opposite direction to the Earth's center. All subsequent systems in the modeling process are based on this coordinate system. For the center of mass of the drone, Let F be the swing angle of the load being lifted, and F be the total pulling force provided by the UAV. Let the length of the lifting rope be... The mass of the drone is The mass of the suspended load is The acceleration due to gravity is g.
[0022] Step Two The dynamic model of the quadrotor UAV sling system containing external disturbances is converted into a radial nonlinear form: , Based on this formula, define: , , , , , Based on error , and the preset performance function Error transformation is performed on the radiometric nonlinear system: , in , , .
[0023] Step 3 The sliding surface function of the terminal sliding mode controller is constructed using the unrestricted radial nonlinear system obtained through error transformation: , Due to the coupling relationship between the x-displacement and the swing angle, the recursive terminal sliding surface and the total sliding surface are designed as follows: , in , , The coefficient to be designed.
[0024] The system after error transformation is combined with hierarchical terminal sliding mode control to design... It can be obtained Equivalent control law , To address disturbances in the control law, an adaptive law is designed to eliminate the disturbances, and a setting is made. To estimate the disturbance, an adaptive law is designed as follows: , in These are the parameters to be designed.
[0025] Choose the sliding mode convergence law: By designing a controller and combining it with an equivalent control law, we can obtain... , in , , , , which are the parameters to be designed.
[0026] Step Four The desired trajectory is selected as follows: , In the formula To determine the displacements in the x and z directions of the positioning trajectory. The initial acceleration adjustment parameters, For gain.
[0027] To verify the effectiveness of the controller designed in this disclosure, testing can be conducted on a self-built platform following the steps described above. This paper utilizes the MATLAB / Simulink experimental simulation platform to build a quadcopter UAV hoisting simulation model, and analyzes the system's positioning and anti-sway performance through numerical simulation. The main parameters of the simulation model are: , The controller gain proposed in the invention: Preset performance parameters: , , , , , , Controller parameters: , , , , , , , , , , , .
[0028] The nonlinear coupling controllers for comparison are as follows: , in: , in, These are the parameters to be designed. This refers to the air drag coefficient. Specific parameters are as follows: .
[0029] In contrast to the layered terminal sliding mode controller, the system it controls is a system that has not undergone preset performance transformation, as shown in the formula. The controller is as follows: , in: , Wherein the gain: , , , , , , , , , , , The results are as follows Figures 2 to 7 As shown.
[0030] Figure 2 and Figure 3 As can be seen, during the process of the preset UAV flying from the origin (0,0) to the target point (8,8), the UAV's trajectory in the z and x directions almost perfectly coincides with the preset trajectory, and the trajectory tracking effect is very good.
[0031] Figure 4 It can be seen that the controller effectively controls the load swing angle under the preset trajectory, and the maximum swing angle is always below 5°. Moreover, when the drone arrives at the target point in about 12 seconds, the swing angle can quickly return to zero, which well completes the positioning and swing elimination function.
[0032] Figure 5 As can be seen from the comparison of error curves between different controllers in the z-direction, the hierarchical terminal sliding mode control based on preset performance proposed in this paper tracks the preset trajectory within 0.5s with a tracking error of 0, and there are no significant fluctuations within 20s of the flight process. Compared with nonlinear coupling control, it has excellent performance. Compared with hierarchical terminal sliding mode control without preset performance, it has a significant improvement in tracking speed, which is optimized from 1s to 0.5s.
[0033] Figure 6As can be seen from the comparison of error curves between different controllers in the x-direction, the hierarchical terminal sliding mode control based on preset performance proposed in this paper exhibits the smallest overall fluctuation, and the error quickly returns to zero when the UAV reaches the target point in about 12 seconds, achieving the positioning function. In contrast, the nonlinear coupled controller still has static errors after reaching the target point, and the hierarchical terminal sliding mode control only achieves stability in about 20 seconds, with excessive overshoot throughout the process.
[0034] Figure 7 As can be seen, the swing angle curves of the three control methods are similar, but the hierarchical terminal sliding mode control method based on preset performance proposed in this paper has a smaller overshoot and a faster stability after reaching the target point. The other two methods take about 14 seconds to achieve stability, while the method in this paper is stable in about 12 seconds.
[0035] Figure 8 As can be seen, when the UAV is hovering at a certain point, and a 0.1N pulse interference of 1.25s is applied at 5s, the hierarchical terminal sliding mode control method based on preset performance proposed in this paper has the smallest fluctuation in the z direction, and can better cope with external interference compared with the other two methods.
[0036] Figure 9 As can be seen, when the UAV is hovering at a certain point, if a 0.1N pulse interference of 1.25s is applied at 5s, the hierarchical terminal sliding mode control method based on preset performance proposed in this paper can achieve rapid stabilization five seconds after the interference occurs in the x-direction. However, the nonlinear coupling controller is offset due to the interference, causing the UAV's positioning to shift by 0.06m. The hierarchical terminal sliding mode control only achieves stabilization 11s after the interference occurs.
[0037] Figure 10 It can be seen that when the UAV is hovering at a certain point, and a 0.1N pulse interference of 1.25s is applied at 5s, the hierarchical terminal sliding mode control method based on preset performance proposed in this paper has a smaller overshoot in terms of swing angle compared with the other two methods, and can achieve stability about 5s after the interference occurs.
[0038] Example 2: This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the layered terminal sliding mode control method for a quadcopter UAV sling system based on preset performance as described in Embodiment 1.
[0039] Example 3: This embodiment provides a computer-readable storage medium storing a computer program. When executed by a processor, this program implements the layered terminal sliding mode control method for a quadcopter UAV sling system based on preset performance, as described in Embodiment 1. It enables the UAV sling system to track the trajectory and quickly eliminate sway under a preset trajectory. This preset trajectory is not limited to the S-shaped trajectory shown in the text; any normal UAV trajectory conforming to the laws of physics is acceptable.
[0040] The preferred embodiments and examples of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments and examples. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the concept of the present invention.
Claims
1. A hierarchical terminal sliding mode control method for a quadcopter UAV sling system based on preset performance, characterized in that: Includes the following steps, S1. Using Lagrange equations and dynamic analysis, a dynamic model of the quadrotor UAV sling system with external disturbances is established. The error is defined by comparing the desired trajectory with the established dynamic model. Using a pre-defined performance method, the boundary-constrained error *e* in the original system is mapped to a new unconstrained variable. This enables the transformation of errors in the quadcopter drone's mounting system. S2. Based on the model of the quadcopter UAV sling system after error transformation, the sliding mode control method of the terminal is adopted to design the sliding mode surface of the system. Due to the coupling relationship between the displacement in the x-direction and the swing angle, the idea of layered sliding mode is adopted to design the sub-sliding mode surface and the total sliding mode surface. S3. Combining the quadcopter UAV sling system after error transformation in step S1 and the sliding surface designed in step S2, the controllers in the z and x directions of the system are calculated. Based on this, an adaptive law is designed to improve the robustness of the system against unknown disturbances, and finally the accurate positioning and anti-sway control of the quadcopter UAV sling system are achieved.
2. The layered terminal sliding mode control method for a quadcopter UAV sling system based on preset performance as described in claim 1, characterized in that: In step S1, the dynamic model of the quadrotor UAV sling system containing external disturbances, established based on the Lagrange equations, is as follows: ， in , Indicates the drone's altitude. This represents the displacement of the drone in the x-direction. Let M represent the swing angle of the suspended load, m represent the mass of the UAV, m represent the mass of the suspended load, l represent the length of the suspension rope, g represent the acceleration due to gravity, and d represent external disturbances. Based on this formula, the following is defined: ， ， ， ， ， ， Then, regarding the error Introduce a preset performance function Convert the error to: ， in , ， 。 3. The layered terminal sliding mode control method for a quadcopter UAV sling system based on preset performance as described in claim 1, characterized in that: In step S2, the sliding surface function of the terminal sliding mode controller is constructed as follows: ， In step S2, due to the coupling relationship between the x-displacement and the swing angle, the recursive terminal sliding surface and the overall sliding surface are designed as follows: ， in , , The coefficient to be designed.
4. The layered terminal sliding mode control method for a quadcopter UAV sling system based on preset performance as described in claim 3, characterized in that: In step S3, design It can be obtained The equivalent control law, ， To address disturbances in the control law, an adaptive law is designed to eliminate the disturbances, and a setting is made. To estimate the disturbance, an adaptive law is designed as follows: ， in These are the parameters to be designed; Choose the sliding mode convergence law: By designing a controller and combining it with an equivalent control law, we can obtain: ， in , , , , which are the parameters to be designed.