A two-axis anti-sway device for a drone

Abstract

This application discloses a two-axis anti-sway device for suspending a drone, comprising: a base, a two-axis servo turntable, a rigid rod, a connecting seat, and a control system. The base is mounted on the drone body; the two-axis servo turntable is mounted on the base; the upper end of the rigid rod is rigidly connected to the power output end of the two-axis servo turntable, and the lower end is rigidly connected to the connecting seat used to fix the suspended load; the control system includes an attitude acquisition module, a main control module, and a drive module; the attitude acquisition module is used to acquire load attitude data and receive inertial navigation data from the drone; the main control module is used to generate compensation torque commands based on the load attitude data and the drone's inertial navigation data; the drive module is used to drive the two-axis servo turntable to output compensation torque according to the compensation torque commands, thereby counteracting the sway of the suspended object. This application can quickly suppress large swaying of the suspended load, improves the anti-sway response speed, and has low hysteresis.

Description

Technical Field

[0001] This application relates to the field of unmanned aerial vehicle technology, and in particular to a two-axis anti-sway device for unmanned aerial vehicles. Background Technology

[0002] With the rapid development of drone technology, drone slinging operations have been widely used in logistics transportation, emergency rescue delivery, aerial surveying, power line inspection, film and television aerial photography and other fields, becoming one of the core application directions of drones in civilian scenarios.

[0003] During drone slinging operations, the load is prone to irregular swaying due to factors such as drone acceleration and deceleration, turning, attitude adjustment, and external wind disturbance. This swaying not only reduces the positioning accuracy and efficiency of the slinging operation, but also, in severe cases, interferes with the flight attitude stability of the drone, and may even cause safety accidents such as crashes or load falls. Therefore, the anti-sway control of the slinging load has become a core technical problem that urgently needs to be solved in the field of drone slinging operations.

[0004] Currently, existing drone-borne anti-sway technologies can be mainly categorized as follows:

[0005] One type is the passive sway suppression solution, which mainly suppresses load sway through passive structures such as cable dampers, flexible buffer structures, and self-stabilizing gimbals. This type of solution has a simple structure, but the sway suppression effect is limited. It can only suppress small sway to a certain extent and cannot cope with large sway caused by the dynamic flight of drones or strong winds. Moreover, the sway suppression response is lagging, and it cannot achieve active stabilization. It has poor adaptability and cannot meet the operational needs of different weight loads.

[0006] Another type is the active anti-sway solution based on UAV flight control adjustment. This solution counteracts load sway by adjusting the UAV flight attitude, acceleration, deceleration, and flight trajectory through the UAV flight control system. This type of solution does not require additional anti-sway devices, but the anti-sway control is deeply coupled with the UAV flight control. To achieve anti-sway, the normal flight state of the UAV needs to be adjusted frequently, which greatly reduces the efficiency of operation and is very easy to cause UAV attitude instability, especially in the case of heavy load suspension, which poses a very high safety risk.

[0007] In summary, existing UAV slinging and sway reduction technologies all have varying degrees of defects. Passive solutions have insufficient slinging and sluggish response, while active flight control adjustment solutions pose flight safety hazards and have low operational efficiency. None of them can simultaneously meet the core requirements of slinging operations that do not affect the normal flight of the UAV, while achieving fast slinging response, high control precision, strong adaptability, and safety and reliability. Summary of the Invention

[0008] This application aims to at least partially solve one of the technical problems in the aforementioned technologies.

[0009] To achieve the above objectives, the first aspect of this application proposes a two-axis anti-sway device for suspending a drone, comprising: a base, a two-axis servo turntable, a rigid rod, a connecting seat, and a control system. The base is mounted on the drone body; the two-axis servo turntable is mounted on the base and achieves rotation with mutually orthogonal roll and pitch degrees of freedom through built-in roll servo motors and pitch servo motors; the upper end of the rigid rod is rigidly connected to the power output end of the two-axis servo turntable, and the lower end is rigidly connected to the connecting seat used to fix the suspended load; the control system includes an attitude acquisition module, a main control module, and a drive module; wherein the attitude acquisition module... The system comprises a block for acquiring load attitude data of the suspended load and receiving inertial navigation data from the UAV's inertial navigation system; a main control module for calculating the attitude deviation of the suspended load from the load attitude data and the inertial navigation data, and generating a compensation torque command that includes feedback control and gravity feedforward compensation by combining the absolute angle values ​​of the roll servo motor and the pitch servo motor; and a drive module for driving the roll servo motor and the pitch servo motor to output compensation torque according to the compensation torque command, so as to suppress the attitude deviation of the suspended load relative to the preset horizontal reference attitude in the roll and pitch directions.

[0010] In addition, the UAV-mounted two-axis anti-sway device proposed in this application may also have the following additional technical features:

[0011] As a further description of the above technical solution: the upper surface of the base is provided with mounting holes that match the body of the UAV, and the lower end of the base extends downward with two sets of symmetrically arranged vertical support cantilever arms, and the two-axis servo turntable is installed between the two sets of vertical support cantilever arms.

[0012] As a further description of the above technical solution: the two-axis servo turntable also includes a roll frame and a pitch frame; wherein, the roll frame is rotatably disposed between the two vertical support cantilever arms about the roll axis, and is connected to the roll servo motor mounted on the vertical support cantilever arms; the pitch frame is rotatably disposed within the roll frame about the pitch axis, and is connected to the pitch servo motor mounted on the roll frame; wherein, the roll axis and the pitch axis are orthogonal and perpendicular to each other; the bottom of the pitch frame is the power output end of the two-axis servo turntable, and is connected to the rigid rod.

[0013] As a further description of the above technical solution: both the roll servo motor and the pitch servo motor have built-in servo motor encoders coaxial with their rotors at their tail ends. The servo motor encoders are used to collect the absolute angle values ​​of the corresponding servo motors and feed them back to the main control module.

[0014] As a further description of the above technical solution: the drive module includes servo drivers that correspond one-to-one with the roll servo motor and the pitch servo motor; the servo drivers are used to receive the compensation torque command output by the main control module, convert it into a matching drive current, and control the corresponding servo motor to output a compensation torque opposite to the swing direction of the suspended load.

[0015] As a further description of the above technical solution: the attitude acquisition module includes a three-axis gyroscope, a three-axis accelerometer, and a data interaction unit; wherein, the three-axis gyroscope is used to acquire load angular velocity data in the load attitude data; the three-axis accelerometer is used to acquire load acceleration data in the load attitude data; and the data interaction unit is used to receive aircraft angle data and aircraft acceleration data in the aircraft inertial navigation data.

[0016] As a further description of the above technical solution: the main control module includes an attitude calculation unit, wherein the attitude calculation unit calculates the attitude deviation of the suspended load by solving the load angular velocity data, the load acceleration data, the carrier angle data, and the carrier acceleration data, and generates a feedback control quantity; wherein the specific steps of calculating the attitude deviation of the suspended load and generating the feedback control quantity are as follows: S100, constructing a first coordinate rotation matrix from the navigation coordinate system to the carrier body coordinate system based on the carrier angle data, and constructing a second coordinate rotation matrix from the carrier body coordinate system to the suspended load body coordinate system based on the absolute angle values ​​of the roll servo motor and the pitch servo motor; determining the carrier angular velocity and carrier angular acceleration based on the carrier angle data of the continuous sampling period, and determining the additional acceleration of the suspended mounting point by combining the position vector from the carrier inertial navigation reference point to the suspended mounting point. S200: Using the first coordinate rotation matrix, the additional acceleration, and the second coordinate rotation matrix, the acceleration data of the carrier aircraft is converted into traction acceleration in the coordinate system of the suspended load; S300: The traction acceleration is removed from the load acceleration data to obtain corrected acceleration data containing only gravity direction information and load sway information; S400: A quaternion-based attitude prediction model is constructed, and the predicted attitude quaternion for the current period is updated; S500: The predicted attitude quaternion and the corrected acceleration data are fused using a filtering fusion algorithm to obtain the optimal attitude quaternion for the current period; S600: The optimal attitude quaternion is converted into real-time roll angle and pitch angle, compared with a preset horizontal reference attitude, and the attitude deviation of the suspended load is calculated; S700: Based on the attitude deviation, the feedback control quantity used to counteract the dynamic sway of the load is calculated using an incremental PID control law.

[0017] As a further description of the above technical solution: the main control module also includes a feedforward compensation unit, which is used to calculate the gravity feedforward compensation amount to offset the influence of static gravitational torque based on the pre-calibrated hanging load parameters and the absolute angle value.

[0018] As a further description of the above technical solution: the three-axis gyroscope and the three-axis accelerometer are integrated into the attitude sensor, and the attitude sensor is fixedly installed at the connecting base and is set to follow the suspended load.

[0019] As a further description of the above technical solution: the main control module also has a built-in parameter calibration unit, which is used to adapt to different models of drones and different weights of suspended loads, and to complete the calibration and adjustment of control parameters, suspended load mass, and rigid rod length.

[0020] The two-axis anti-sway device for UAVs according to this application significantly improves the anti-sway response speed and control accuracy, and can reduce deformation and response delay in the force transmission process. This application adopts a direct-drive structure with a two-axis servo turntable and a rigid rod, which can realize two completely orthogonal and uncoupled independent rotational degrees of freedom: roll and pitch. The force transmission path formed by the rigid connection outputs a force that is beneficial to improving the efficiency of compensation torque transmission and control response speed to the suspended load. Compared with passive anti-sway schemes, it can quickly suppress large swings of the suspended load, significantly improve the anti-sway response speed, and eliminate control lag.

[0021] This application integrates the load attitude data and load acceleration data collected from the suspended load end with the carrier aircraft attitude data and carrier aircraft acceleration data output by the UAV carrier aircraft inertial navigation system, and calculates the attitude deviation of the suspended load, thereby fundamentally solving the problems of inaccurate attitude calculation and failure to eliminate sway during dynamic flight in the prior art.

[0022] This application adopts a composite control method of feedback control and gravity feedforward compensation. Based on the attitude deviation of the suspended load and the real-time absolute angle feedback of the servo motor, a precise closed-loop feedback control quantity is generated. At the same time, the influence of the static gravity torque of the suspended load is calculated and offset in advance by the gravity feedforward compensation unit. This not only eliminates the static attitude deviation, but also improves the dynamic response speed. It can realize the rapid and stable control of the suspended load, reduce steady-state error and control overshoot, and the anti-sway effect is far superior to the existing single feedback control scheme.

[0023] This application achieves anti-sway control through the design of a two-axis servo turntable, which eliminates the need to adjust the normal flight control logic of the UAV and avoids the coupling risk between anti-sway control and flight control. It also eliminates the need to install an additional power propulsion device on the load-bearing end, does not additionally occupy the effective payload capacity of the UAV, and does not negatively affect the aerodynamic layout and endurance of the UAV, thus greatly improving operational safety and endurance.

[0024] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0025] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0026] Figure 1 This is a schematic diagram of the structure of a two-axis anti-sway device for a drone according to an embodiment of this application;

[0027] Figure 2 This is a system block diagram of a control system according to an embodiment of this application;

[0028] Figure 3 This is a schematic diagram of the control flow of a control system according to an embodiment of this application;

[0029] Figure 4 This is a schematic diagram of the process for generating feedback control quantities according to an embodiment of this application;

[0030] As shown in the figure:

[0031] 100, Base; 200, Two-axis servo turntable; 210, Roll servo motor; 220, Pitch servo motor; 230, Roll frame; 240, Pitch frame; 300, Rigid rod; 400, Connecting seat; 500, Suspended load. Detailed Implementation

[0032] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0033] The following description, in conjunction with the accompanying drawings, describes the UAV-mounted two-axis anti-sway device according to an embodiment of this application.

[0034] like Figure 1 As shown, the UAV-mounted two-axis anti-sway device of this application embodiment includes a base 100, a two-axis servo turntable 200, a rigid rod 300, a connecting seat 400, and a control system.

[0035] The base 100 has mounting holes on its upper surface that match the UAV body. The base 100 is connected to the UAV body through the mounting holes. The lower end of the base 100 has two sets of symmetrically arranged vertical support cantilever arms. The two-axis servo turntable 200 is installed between the two sets of vertical support cantilever arms.

[0036] The two-axis servo turntable 200 is mounted on the base 100. The two-axis servo turntable 200 includes a roll servo motor 210, a pitch servo motor 220, a roll frame 230 and a pitch frame 240.

[0037] The rotation of two degrees of freedom, roll and pitch, is achieved through the roll servo motor 210 and the pitch servo motor 220.

[0038] The roll frame 230 is rotatably mounted between two vertical support cantilever arms around the roll axis and is connected to the roll servo motor 210 mounted on the vertical support cantilever arms. The pitch frame 240 is rotatably mounted inside the roll frame 230 around the pitch axis and is connected to the pitch servo motor 220 mounted on the roll frame 230. The roll axis and the pitch axis are orthogonal and perpendicular to each other.

[0039] The bottom of the pitch frame 240 is the power output end of the two-axis servo turntable 200, which is connected to the upper end of the rigid rod 300. The lower end of the rigid rod 300 is rigidly connected to the connecting seat 400 used to fix the suspended load 500.

[0040] The compensation torque and rotational motion output by the two-axis servo turntable 200 are transmitted to the suspended load 500 through the pitch frame 240, rigid rod 300, and connecting seat 400. It should be noted that the rigid rod 300 mentioned in this application refers to a rigid force-transmitting component whose bending and torsional deformations are negligible relative to the roll and pitch angles of the two-axis servo turntable 200 within the normal operating load and control frequency range of the device. It does not imply the absence of relative rotational degrees of freedom between the UAV body and the suspended load 500. The roll and pitch relative rotational degrees of freedom between the UAV body and the suspended load 500 are provided by the corresponding axes of the roll frame 230 and pitch frame 240. The oscillation of the suspended load 500 specifically manifests as periodic or non-periodic attitude deviations of the suspended load 500 relative to a preset horizontal reference attitude in the roll and pitch directions, rather than a flexible oscillation of the rigid rod 300 itself. In the dynamic calculation, the rigid rod 300 is treated as a rigid body link. The moment of inertia of the two-axis servo turntable 200 and the equivalent damping of the servo motor and the rotating shaft system are used to characterize the dynamic response of the two rotational degrees of freedom of roll and pitch.

[0041] The control system includes an attitude acquisition module, a main control module, and a drive module.

[0042] The attitude acquisition module is used to acquire the load attitude data of the 500-ton suspended load and to receive the inertial navigation data of the UAV carrier inertial navigation system.

[0043] The main control module is used to calculate the attitude deviation of the suspended load 500 by solving the load attitude data and the carrier inertial navigation data, and to generate a compensation torque command that includes feedback control quantity and gravity feedforward compensation quantity by combining the absolute angle values ​​of the roll servo motor 210 and the pitch servo motor 220.

[0044] The drive module is used to drive the roll servo motor 210 and the pitch servo motor 220 to output compensation torque according to the compensation torque command, so as to counteract the sway of the suspended object.

[0045] Specifically, during the drone slinging operation, the attitude acquisition module synchronously collects multi-source motion data of the sling load 500 and the drone carrier, and then the main control module calculates the attitude deviation of the sling load 500. Based on the attitude deviation and the real-time angle of the servo motor, a compensation torque command is generated. Subsequently, the drive module drives the corresponding servo motors of the two-axis servo turntable 200 to output the reverse compensation torque. Finally, the compensation action is transmitted to the sling load 500 through the rigid rod 300 to counteract its sway. The device executes the above process in a fixed cycle to achieve continuous active sway elimination throughout the entire slinging operation, ensuring that the sling load 500 is always in a stable horizontal state.

[0046] In one embodiment of this application, the attitude acquisition module includes a three-axis gyroscope, a three-axis accelerometer, and a data interaction unit.

[0047] Among them, the three-axis gyroscope is used to collect load angular velocity data (including roll axis angular velocity) from the load attitude data. pitch axis angular velocity yaw rate A triaxial accelerometer is used to acquire load acceleration data (including load attitude data) from the load acceleration data. The data interaction unit is used to receive aircraft angle data (including roll angle) from the aircraft's inertial navigation data via a communication interface. Pitch angle Yaw angle ) and aircraft acceleration data (including ).

[0048] The main control module includes an attitude calculation unit, which calculates the attitude deviation of the suspended load 500 by calculating the load angular velocity data, the load acceleration data, the carrier angle data, and the carrier acceleration data, and generates a feedback control quantity.

[0049] The specific steps for calculating the attitude deviation of the suspended load 500 and generating the feedback control quantity are as follows:

[0050] S100. Based on the aircraft angle data, construct a coordinate rotation matrix and combine it with the roll and pitch absolute angle values ​​of the two-axis servo turntable 200 to convert the aircraft acceleration data to the same coordinate system as the load body coordinate system to obtain the traction acceleration of the load 500.

[0051] It should be noted that this step involves the navigation coordinate system, the carrier aircraft coordinate system, and the load-bearing aircraft coordinate system. The navigation coordinate system is a reference coordinate system fixed to the ground; the carrier aircraft coordinate system changes with the UAV's attitude; and the load-bearing aircraft coordinate system changes along with the roll frame 230, the pitch frame 240, and the load 500. Since the pitch frame 240 is located within the roll frame 230, the relative attitude between the load-bearing aircraft coordinate system and the carrier aircraft coordinate system is determined by the absolute roll angle of the roll servo motor 210. And the absolute pitch angle of the pitch servo motor 220 To be determined jointly.

[0052] First, based on the roll angle in the aircraft angle data Pitch angle and yaw angle Construct the first coordinate rotation matrix from the navigation coordinate system to the aircraft body coordinate system. The aircraft acceleration vector in the navigation coordinate system Transform to the aircraft body coordinate system.

[0053] Furthermore, when using a right-handed coordinate system and setting the two-axis servo turntable 200 according to the rotation relationship of outer roll and inner pitch, based on the absolute roll angle... and absolute pitch angle Construct the second coordinate rotation matrix from the carrier aircraft body coordinate system to the suspended load body coordinate system. ,in .

[0054] Considering the additional acceleration generated by the rotation of the carrier aircraft on the mounting point during the UAV's maneuvering flight, let... The position vector pointing from the aircraft's inertial navigation reference point to the 200 mounting point of the two-axis servo turntable. Let be the angular velocity of the carrier aircraft in the carrier aircraft's body coordinate system. Given the corresponding angular acceleration, the translational acceleration of the carrier aircraft's inertial navigation reference point, after being converted to the hoisting point, is... .in, It can be determined based on the aircraft attitude data from continuous sampling periods. It can be determined based on the change in angular velocity between adjacent sampling periods.

[0055] Then, using the second coordinate rotation matrix, the acceleration of the suspension mounting point is transformed into the coordinate system of the suspended load body, resulting in... and will The traction acceleration is the acceleration that needs to be removed from the load acceleration data in step S200. Thus, the carrier acceleration data sequentially completes the transformation from the navigation coordinate system to the carrier body coordinate system and from the carrier body coordinate system to the load body coordinate system, while the tangential additional acceleration and centripetal additional acceleration generated by the carrier rotation at the mounting point are included in the traction acceleration.

[0056] S200. Remove traction acceleration from the load acceleration data to obtain corrected acceleration data containing only gravity direction information and load sway information.

[0057] Understandably, the raw load acceleration data contains three core components: first, the traction acceleration caused by the UAV's flight motion, which is an interference component; second, the Earth's gravitational acceleration, which serves as the baseline for attitude calculation; and third, the dynamic acceleration generated by the attitude changes of the suspended load 500 relative to the preset horizontal baseline attitude in the roll and pitch rotational degrees of freedom, which is the motion component that the anti-sway control needs to identify and suppress, and its formula is:

[0058]

[0059] in, The specific force measured by the triaxial accelerometer, i.e., the load acceleration data; The actual total acceleration of the suspended load of 500 in space. For traction acceleration, This is the oscillation acceleration.

[0060] Therefore, by subtracting the acceleration of the carrier aircraft, a corrected force ratio containing information about the direction of gravity and the 500° swing of the suspended load can be obtained. That is, to correct the acceleration data, the formula is: .

[0061] When static or oscillating slowly ,but It can be directly used to estimate attitude, especially in dynamic situations. It can be estimated through filtering or modeling.

[0062] This step completely eliminates traction acceleration interference from the original load acceleration data through corresponding subtraction operations of the three-axis components. The final corrected acceleration data retains only the gravity direction information used as the attitude calculation reference and the swing acceleration information used to determine the swing state of the suspended load 500. This completely eliminates the interference of all flight actions such as UAV acceleration, deceleration, turning, and attitude adjustment on attitude calculation. Whether it is a static scene of UAV hovering or a dynamic flight scene of acceleration, deceleration, and turning, a stable and effective attitude calculation data source can be output.

[0063] S300. Construct a quaternion-based attitude prediction model and update the predicted attitude quaternion for the current cycle.

[0064] It should be noted that the above-mentioned corrected acceleration data and gyroscope integration results are fused together, and an extended Kalman filter (EKF) is used to estimate the attitude quaternions of the suspended load 500. The state vector is taken as a quaternion. ,in, It is the real part of the quaternion. , , These are the imaginary parts corresponding to the three spatial axes of roll, pitch, and yaw, respectively, with T being the transpose symbol.

[0065] The angular velocity data from the three-axis gyroscope is used as the control input, and an antisymmetric matrix is ​​constructed using the angular velocity from the previous sampling period. Calculations yielded Instantaneous rate of change of attitude within the sampling period Its attitude prediction model is:

[0066]

[0067] Then, using the commonly used first-order Euler discrete integral, the instantaneous rate of attitude change is multiplied by the sampling period and superimposed onto the optimal attitude quaternion of the previous period. The above updates the predicted attitude quaternion for the current period. Its formula is:

[0068]

[0069] The superscript − indicates that the value is a predicted value.

[0070] It should be noted that the core inputs for this step include: the optimal attitude quaternion obtained from the previous cycle. Effective angular velocity data in the roll and pitch directions acquired by the three-axis gyroscope in the previous cycle. Preset fixed control sampling period (e.g., 1ms, commonly used in engineering) =0.001s), the entire solution process is a closed-loop iterative process with a fixed period: after the UAV is powered on and initially aligned, it will obtain the initial attitude quaternion under the 500 horizontal state of the suspended load, which will be used as the input for the first solution cycle. Subsequent cycles will automatically use the optimal attitude quaternion of the previous cycle as the input to form a continuous closed loop.

[0071] S400. The predicted attitude quaternion and the corrected acceleration data are fused by a filtering fusion algorithm to obtain the optimal attitude quaternion for the current cycle.

[0072] It should be noted that the gravity reference standard value is a fixed standard value of the Earth's gravitational acceleration in the ground navigation coordinate system, its direction is always vertically downward, and its value is a fixed value. It is the absolute horizontal reference for attitude calculation, and it will not change with the flight of the drone or the swing of the 500 load. It is the only absolute reference for correcting the cumulative drift of the three-axis gyroscope.

[0073] The attitude prediction quaternion obtained in step S300 Construct a rotation matrix from the 500 airframe coordinate system to the ground navigation coordinate system. Then, through matrix transpose, the vertically downward gravity reference standard value in the navigation coordinate system is obtained. Transforming to the body coordinate system with a suspended load of 500, we obtain the theoretical gravity value corresponding to the current predicted attitude, which is... ,in, To measure the noise, the observation residual is obtained by calculating the difference between the corrected acceleration data and the theoretical gravity value.

[0074] Based on the observation residuals calculated in the previous step, the Kalman gain is calculated using the extended Kalman filter algorithm. The cumulative drift error of the attitude prediction quaternion obtained in step S500 is then corrected using the observation residuals. Finally, the optimal attitude quaternion that retains the high response characteristics of the gyroscope and avoids long-term drift is obtained for the current period. The optimal attitude quaternion will be automatically used as the input for the next cycle step S500.

[0075] S500: Convert the optimal attitude quaternion into real-time roll angle and pitch angle, compare them with the preset horizontal reference attitude, and calculate the attitude deviation of the suspended load 500.

[0076] It should be noted that the optimal attitude quaternion output in step S400 is... By converting quaternions to Euler angles, i.e. using a general conversion formula, the real-time roll angle of the suspended load 500 relative to the horizontal reference plane can be calculated. Pitch angle Yaw angle .

[0077] For example, the real-time roll angle can be calculated using the following formulas. Pitch angle Yaw angle :

[0078]

[0079]

[0080]

[0081] Additionally, if the aircraft's inertial navigation system also provides accurate attitude, it can be used as an auxiliary observation in filtering to improve the accuracy of yaw angle estimation. For example, the aircraft's yaw angle can be... As a pseudo-observation, the observation equation is: ,in To observe the noise, its value can be calibrated and adjusted according to the actual output accuracy of the carrier aircraft's inertial navigation system. This addresses the technical problem that the yaw angle is prone to cumulative drift and insufficient long-term estimation accuracy due to the lack of an absolute geographical reference benchmark and reliance solely on the integration of a three-axis gyroscope during the attitude calculation process at the suspended load end.

[0082] In this application, the core objective of anti-sway control is to keep the suspended load 500 in an absolutely horizontal state at all times. Therefore, the preset horizontal reference attitude is the horizontal zero-position reference, i.e., the reference roll angle. Reference pitch angle .

[0083] Then the roll angle deviation The calculation formula is:

[0084]

[0085] Pitch angle deviation The calculation formula is:

[0086]

[0087] The rate of change of roll angular velocity deviation is:

[0088]

[0089] The rate of change of pitch angular velocity deviation is:

[0090]

[0091] Understandably, existing drone-borne sway reduction technologies suffer from several drawbacks: reliance on single-source sensor data from the load side, inability to separate drone flight motion interference, large attitude calculation errors in dynamic flight scenarios, and severe cumulative drift. To address these issues, a multi-step, precise calculation architecture—combining load-side motion sensing, carrier aircraft inertial navigation data fusion, and precise multi-step calculation—is employed. This architecture achieves high-precision, stable calculation of a 500° attitude deviation for the slung load. First, interference from drone flight motion is eliminated using carrier aircraft data, yielding pure data containing only gravity reference and load sway information. Then, the attitude is rapidly predicted using a gyroscope, and the cumulative drift of the gyroscope is corrected using the gravity reference, ultimately resulting in a precise attitude deviation.

[0092] S600. Based on the attitude deviation, the feedback control quantity used to counteract the dynamic swing of the load is calculated by an incremental PID control law.

[0093] It should be noted that the main control module can calculate the control torque of the roll axis and pitch axis using an incremental PID control law. Specifically, the roll axis control torque... The calculation formula is:

[0094]

[0095] Pitch axis control torque The calculation formula is:

[0096]

[0097] in, This is the proportionality coefficient. The differential coefficients are... is the integral coefficient.

[0098] In one embodiment of this application, the tail ends of both the roll servo motor 210 and the pitch servo motor 220 are equipped with servo motor encoders coaxial with their rotors. The encoders of the servo motors are used to collect the absolute angle values ​​of the corresponding servo motors and feed them back to the main control module.

[0099] In addition, the main control module has a built-in feedforward compensation unit, which is used to calculate the pre-calibrated parameters of the suspended load 500 (mass m, distance from the center of mass to the suspension point). ), combined with real-time absolute angle values ​​( absolute pitch angle The gravity feedforward compensation amount used to counteract the effects of static gravitational torque is calculated.

[0100] It should be noted that the suspended load 500 is connected to the two-axis servo turntable 200 through the rigid rod 300. When the servo motor has a rotation angle (i.e. the suspended load 500 deviates from the horizontal), gravity will generate a continuous disturbance torque on the motor shaft. This torque will force the suspended object to swing continuously in the tilting direction. If only PID control is used, the correction torque will only be output after the deviation occurs, which will result in response lag and static error.

[0101] Gravitational torque is a fixed disturbance that can be accurately calculated using physical formulas. Without waiting for the deviation to appear, the reverse torque can be calculated and output in advance to cancel the disturbance, allowing the PID controller to only handle the dynamic swaying of the suspended object, thus greatly improving the control response speed and steady-state accuracy.

[0102] Roll axis feedforward compensation torque The calculation formula is:

[0103]

[0104] Pitch axis feedforward compensation torque The calculation formula is:

[0105]

[0106] Since the pitch frame 240 is located within the roll frame 230, the pitch axis rotates synchronously with the roll frame 230. Therefore, the torque generated by the weight of the suspended load 500 in the pitch axis direction is also affected by the absolute roll angle. The projection effect, therefore through Correct the gravitational torque component in the pitch axis direction.

[0107] Therefore, the final output torque of the roll shaft for: Pitch axis output torque for: .

[0108] In one embodiment of this application, the drive module includes servo drivers that correspond one-to-one with the roll servo motor 210 and the pitch servo motor 220; the servo drivers are used to receive the compensation torque command output by the main control module, convert it into a matching drive current, and control the corresponding servo motor to output a compensation torque opposite to the swing direction of the suspended load 500.

[0109] It should be noted that the compensation torque command includes the roll axis output torque and pitch axis output torque obtained in the previous embodiment. The servo driver then controls the roll servo motor 210 and the pitch servo motor 220 to work according to the roll axis output torque and the pitch axis output torque, respectively, in order to perform compensation.

[0110] In one embodiment of this application, a three-axis gyroscope and a three-axis accelerometer are integrated into an integrated attitude sensor, which is fixedly installed at the connector 400 and is dynamically set to follow the suspended load 500.

[0111] It should be noted that the integrated design reduces the installation volume and avoids the installation errors of discrete components, ensuring the synchronization and accuracy of the acquired signals. By being fixed at the connector 400 and rigidly bound to the suspended load 500 for synchronous movement, the actual swing and tilt state of the suspended load 500 can be directly and without interference, providing accurate raw data for subsequent attitude calculation and anti-sway control.

[0112] In one embodiment of this application, the main control module also has a built-in parameter calibration unit, which is used to adapt to different models of drones and different weights of suspended loads 500, and to complete the calibration and adjustment of control parameters, mass of suspended load 500, and length of rigid rod 300.

[0113] It should be noted that the parameter calibration unit can be flexibly adapted to different models of drones and different weights of suspended loads 500, and complete the calibration and adjustment of anti-sway control parameters, suspended load 500 mass, and rigid rod 300 length. This design allows the device to be quickly adapted without being fixed to a single drone or fixed load. After changing the working carrier or suspended object, only simple calibration is required, which greatly improves the versatility of the device and the flexibility of on-site operation, while ensuring the anti-sway control accuracy in different scenarios.

[0114] In summary, the two-axis anti-sway device for UAVs according to the embodiments of this application significantly improves the anti-sway response speed and control accuracy, and can reduce deformation and response delay during the force transmission process. This application adopts a direct-drive structure with a two-axis servo turntable 200 and a rigid rod 300, which can realize two completely orthogonal and uncoupled independent rotational degrees of freedom of roll and pitch. The force transmission path formed by the rigid connection outputs a force that is beneficial to improving the efficiency of compensation torque transmission and control response speed to the suspended load 500. Compared with the passive anti-sway scheme, it can quickly suppress the large swing of the suspended load 500, significantly improve the anti-sway response speed, and eliminate control lag.

[0115] This application integrates the load attitude data and load acceleration data collected by the suspended load 500 end with the carrier aircraft attitude data and carrier aircraft acceleration data output by the UAV carrier aircraft inertial navigation system, and calculates the attitude deviation of the suspended load 500, thereby fundamentally solving the problems of inaccurate attitude calculation and failure to eliminate sway during dynamic flight in the prior art.

[0116] This application adopts a composite control method of feedback control and gravity feedforward compensation. Based on the attitude deviation of the suspended load 500 and the real-time absolute angle feedback of the servo motor, a precise closed-loop feedback control quantity is generated. At the same time, the static gravity torque of the suspended load 500 is calculated and offset in advance by the gravity feedforward compensation unit. This not only eliminates the static attitude deviation, but also improves the dynamic response speed, which can realize the rapid and stable control of the suspended load 500, reduce steady-state error and control overshoot, and the anti-sway effect is far superior to the existing single feedback control scheme.

[0117] This application achieves anti-sway control through the design of a two-axis servo turntable 200, without the need to adjust the normal flight control logic of the UAV, thus avoiding the coupling risk between anti-sway control and flight control; it also eliminates the need to install an additional power propulsion device at the load end 500, without additionally occupying the effective payload capacity of the UAV, and without negatively affecting the aerodynamic layout and endurance of the UAV, thus greatly improving operational safety and endurance.

[0118] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0119] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0120] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A device for suspending two axes of unmanned aerial vehicles (UAVs) to eliminate sway, characterized in that, It includes a base (100), a two-axis servo turntable (200), a rigid rod (300), a connecting seat (400), and a control system, wherein, The base (100) is mounted on the body of the UAV; The two-axis servo turntable (200) is mounted on the base and achieves rotation with two mutually orthogonal degrees of freedom, roll and pitch, through the built-in roll servo motor (210) and pitch servo motor (220); The upper end of the rigid rod (300) is rigidly connected to the power output end of the two-axis servo turntable (200), and the lower end is rigidly connected to the connecting seat (400) used to fix the suspended load (500). The control system includes an attitude acquisition module, a main control module, and a drive module; The attitude acquisition module is used to acquire the load attitude data of the suspended load and receive the carrier inertial navigation data of the UAV. The main control module is used to calculate the attitude deviation of the suspended load by solving the load attitude data and the carrier aircraft inertial navigation data, and generate a compensation torque command containing feedback control quantity and gravity feedforward compensation quantity by combining the absolute angle values ​​of the roll servo motor and the pitch servo motor. The drive module is used to drive the roll servo motor and the pitch servo motor to output compensation torque according to the compensation torque command, so as to suppress the attitude deviation of the suspended load relative to the preset horizontal reference attitude in the roll and pitch directions.

2. The UAV-mounted two-axis anti-sway device according to claim 1, characterized in that, The upper surface of the base (100) is provided with mounting holes that match the body of the UAV. The lower end of the base (100) extends downward with two sets of symmetrically arranged vertical support cantilever arms. The two-axis servo turntable (200) is installed between the two sets of vertical support cantilever arms.

3. The UAV-mounted two-axis anti-sway device according to claim 2, characterized in that, The two-axis servo turntable (200) also includes a roll frame (230) and a pitch frame (240). The rolling frame (230) is rotatably disposed between the two vertical support cantilever arms around the rolling axis and is connected to the rolling servo motor (210) mounted on the vertical support cantilever arms. The pitch frame (240) is rotatably disposed within the roll frame (230) about the pitch axis and is connected to the pitch servo motor (220) mounted on the roll frame (230); Wherein, the roll axis and the pitch axis are orthogonal and perpendicular to each other; The bottom of the pitch frame (240) is the power output end of the two-axis servo turntable (200) and is connected to the rigid rod (300).

4. The UAV-mounted two-axis anti-sway device according to claim 1, characterized in that, The tail ends of both the roll servo motor (210) and the pitch servo motor (220) are equipped with servo motor encoders coaxial with their rotors. The servo motor encoders are used to collect the absolute angle values ​​of the corresponding servo motors and feed them back to the main control module.

5. The UAV-mounted two-axis anti-sway device according to claim 1, characterized in that, The drive module includes servo drivers that correspond one-to-one with the roll servo motor (210) and the pitch servo motor (220); the servo drivers are used to receive the compensation torque command output by the main control module, convert it into a matching drive current, and control the corresponding servo motor to output a compensation torque opposite to the swing direction of the suspended load.

6. The UAV-mounted two-axis anti-sway device according to claim 1, characterized in that, The attitude acquisition module includes a three-axis gyroscope, a three-axis accelerometer, and a data interaction unit; wherein... The three-axis gyroscope is used to collect load angular velocity data from the load attitude data; The triaxial accelerometer is used to collect load acceleration data from the load attitude data; The data interaction unit is used to receive the aircraft angle data and aircraft acceleration data from the aircraft inertial navigation data.

7. The UAV-mounted two-axis anti-sway device according to claim 6, characterized in that, The main control module includes an attitude calculation unit, wherein the attitude calculation unit calculates the attitude deviation of the suspended load by calculating the load angular velocity data, the load acceleration data, the carrier angle data and the carrier acceleration data, and generates feedback control quantity; The specific steps for calculating the attitude deviation of the suspended load and generating the feedback control quantity are as follows: S100: Construct a first coordinate rotation matrix from the navigation coordinate system to the carrier body coordinate system based on the carrier angle data, and construct a second coordinate rotation matrix from the carrier body coordinate system to the suspended load body coordinate system based on the absolute angle values ​​of the roll servo motor and the pitch servo motor; determine the carrier angular velocity and carrier angular acceleration based on the carrier angle data of the continuous sampling period, and determine the additional acceleration of the suspended load mounting point by combining the position vector from the carrier inertial navigation reference point to the suspended load mounting point; use the first coordinate rotation matrix, the additional acceleration, and the second coordinate rotation matrix to convert the carrier acceleration data into traction acceleration in the suspended load body coordinate system; S200: Remove traction acceleration from the load acceleration data to obtain corrected acceleration data containing only gravity direction information and load sway information; S300. Construct a quaternion-based attitude prediction model and update the predicted attitude quaternion for the current cycle. S400. The predicted attitude quaternion and the corrected acceleration data are fused by a filtering fusion algorithm to obtain the optimal attitude quaternion for the current cycle. S500: Convert the optimal attitude quaternion into real-time roll angle and pitch angle, compare them with the preset horizontal reference attitude, and calculate the attitude deviation of the suspended load. S600. Based on the attitude deviation, the feedback control quantity used to counteract the dynamic swing of the load is calculated by an incremental PID control law.

8. The UAV-mounted two-axis anti-sway device according to claim 1, characterized in that, The main control module also includes a feedforward compensation unit, which is used to calculate the gravity feedforward compensation amount to offset the influence of static gravitational moment based on the pre-calibrated hanging load parameters and the absolute angle value.

9. The UAV-mounted two-axis anti-sway device according to claim 6, characterized in that, The three-axis gyroscope and the three-axis accelerometer are integrated in the attitude sensor, which is fixedly installed at the connecting seat (400) and is set to follow the suspended load.

10. The UAV-mounted two-axis anti-sway device according to claim 8, characterized in that, The main control module also has a built-in parameter calibration unit, which is used to adapt to different models of drones and different weights of the suspended load (500) to complete the calibration and adjustment of the load parameters.

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