Multi-rotor unmanned aerial vehicle image guidance interception method based on single-axis holder

Abstract

The invention discloses a multi-rotor unmanned aerial vehicle image guidance interception method based on a single-axis holder, and aims to design a multi-rotor guidance law in combination with image information and realize guidance law tracking by adopting a double-loop PID (Proportion Integration Differentiation) controller. The system cost can be greatly reduced, and the system weight is effectively reduced; in the tracking process, the expected course is kept unchanged all the time, tracking errors are controlled by adjusting the transverse position speed, the system response speed is increased, and the phenomenon that the target loses lock and the like due to the fact that large course angle expected change is generated due to rapid change of the target in an image during tail end guidance is avoided; in addition, when the target is tracked, the position change of the target in the image is considered all the time, it is guaranteed that no large transverse position deviation is generated in the whole tracking process, and the terminal guidance interception precision can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of multi-rotor UAV guidance technology, and in particular, it is a multi-rotor UAV image guidance and interception method based on a single-axis gimbal. Background Technology

[0002] With the rapid development of technologies such as chips, navigation, guidance, and control, multi-rotor drones have been widely used in various fields. Combined with advanced technologies such as image recognition, they can achieve rapid interception of ground targets. Patent application number CN202311829858.4 discloses an image-based terminal guidance method for multi-rotor drones. This method calculates the target's elevation and azimuth angles by combining the aircraft's attitude angles, decomposes the velocity into speed commands in the northeast direction, and completes the control of the aircraft. This method achieves target interception through speed control. However, this method uses a three-axis pod for guidance and tracking, increasing weight and significantly raising system costs. Such systems are often consumables, and a low-cost solution would greatly improve cost-effectiveness. Furthermore, the method's implementation involves keeping the drone's nose always aligned with the target. During approach, as the target's proportion in the image increases, image lock-up and excessive terminal deviation occur. Additionally, this method does not consider the issue of the gimbal failing to keep the target locked in the image center due to the drone platform's rapid maneuvers during tracking, leading to significant tracking errors in actual flight and reducing the accuracy of target interception. Summary of the Invention

[0003] The purpose of this invention is to address the problems existing in the prior art by providing an image guidance method for rotary-wing unmanned aerial vehicles based on a single-axis gimbal.

[0004] The technical solution to achieve the purpose of this invention is: an image-guided interception method for rotary-wing UAVs based on a single-axis gimbal. This method combines image information to design a multi-rotor guidance law and employs a dual-loop PID controller to track the guidance law. Specifically, it includes:

[0005] Step 1: Establish the necessary coordinate systems for the guidance law design, including the northeast inertial coordinate system, the body coordinate system, the gimbal coordinate system, and the line-of-sight coordinate system;

[0006] Step 2: Define the transformation relationships between the coordinate systems;

[0007] Step 3: Extract the line-of-sight angle used to generate guidance commands based on the coordinate system transformation relationship;

[0008] Step 4: Design the multi-rotor guidance law to obtain the northward speed command, the eastward speed command, and the ground speed command, denoted as the NE-G ground speed command;

[0009] Step 5: Convert the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle.

[0010] Step 6: The flight control integrated navigation system obtains the current northward, eastward, and groundward speed feedback of the UAV, and calculates the actual forward, rightward, and groundward speed feedback based on the yaw angle computer body coordinate system.

[0011] Step 7: Based on the results of Steps 5 and 6, obtain the acceleration command of the body coordinate system through the PID controller;

[0012] Step 8: Based on the acceleration command of the body coordinate system, calculate the body attitude angle command, including pitch angle command, roll angle command and yaw rate command;

[0013] Step 9: Based on the aircraft attitude angle command, control the UAV to achieve guided interception.

[0014] Furthermore, step 1, establishing the necessary coordinate system for the guidance law design, specifically includes:

[0015] Define a northeast-central inertial coordinate system, with the UAV's takeoff point as the origin A, Ax N The axis coincides with the minor semi-axis of the Earth's ellipsoid, that is, along the northward direction, Ay E Coinciding with the semi-major axis of the ellipsoid, i.e., along the eastward direction, Az D The axis coincides with the normal to the ellipsoid, with downwards being positive, i.e., along the Earth's direction;

[0016] Define the body coordinate system, with the UAV's center of mass as the origin O, Ox B The axis is located within the UAV's reference plane, parallel to the fuselage axis, and points forward of the aircraft. B The axis is located within the longitudinal symmetry plane of the UAV and is perpendicular to Ox. B The axis pointing downwards is positive, Oy B The axis conforms to the right-hand rule;

[0017] Define the gimbal coordinate system, with the origin O. F At the center of the camera's image, O F x F The axis is the optical axis, pointing forward of the camera is positive, O F z F The axis is perpendicular to O in the longitudinal plane of the camera. F x F And downward is positive, O F y F The axes conform to the right-hand rule; define the camera coordinate system with origin O. L At the center of the camera's image, O L x L Axis at O L On the line connecting to the target point, and pointing positively towards the target, OL z L The axis is perpendicular to O in the longitudinal plane of the camera. L x L The axis is downward, and positive is downward. L y L The axis conforms to the right-hand rule;

[0018] Define a line-of-sight coordinate system with the origin O. S At the center of the camera's image, O S x S Axis at O S On the line connecting to the target point, and pointing positively towards the target, O S z S The axis is perpendicular to O in the vertical plane at the current position of the drone. S x S The axis is downward, and positive is downward. S y S The axis conforms to the right-hand rule.

[0019] Furthermore, step 2, defining the transformation relationships between the coordinate systems, specifically includes:

[0020] Rotate the northeast inertial coordinate system to the body coordinate system, and then rotate around z in sequence. D y' x B The rotation matrix for the axis of rotation—yaw angle ψ, pitch angle θ, and roll angle γ—is shown in ① below, where y' is the rotation around z. D Updated y after axis rotation yaw angle ψ E The axis; the body coordinate system rotates to the gimbal coordinate system, sequentially around the z-axis. B y F Axis rotation horizontal frame angle λ T and pitch frame angle λ D The rotation matrix shown in ② below; rotating from the gimbal coordinate system to the camera coordinate system, respectively around z. F y S Axis rotation lateral image deviation angle ε T and longitudinal image deviation angle ε D The rotation matrix is ​​shown in ③ below; from the northeast inertial coordinate system to the line-of-sight coordinate system, the rotations are respectively around z. D y S Axis rotation line of sight azimuth angle q T and the height angle of the line of sight q D The rotation matrix is ​​shown in ④ below;

[0021] ① Rotation matrix of northeast inertial coordinate system to body coordinate system

[0022]

[0023] In the formula, θ is the pitch angle of the aircraft, γ is the roll angle of the aircraft, and ψ is the yaw angle of the aircraft;

[0024] ② Rotation matrix from body coordinate system to gimbal coordinate system

[0025]

[0026] In the formula, λ D λ is the angle of the gimbal's pitch frame. T This is the yaw angle of the gimbal frame; for a single-axis gimbal, this angle is always 0.

[0027] ③ Rotation matrix from gimbal coordinate system to camera coordinate system

[0028]

[0029] In the formula, ε T ε is the lateral image deviation angle. D The vertical image deviation angle;

[0030] ④ Rotation matrix of the northeast inertial coordinate system to the line-of-sight coordinate system

[0031]

[0032] In the formula, q D q represents the elevation angle of the line of sight. T This is the azimuth angle of the line of sight.

[0033] Furthermore, the image deviation angle is defined as the angle between the camera's optical axis and the line-of-sight axis connecting the camera and the target, and is calculated as follows:

[0034]

[0035] In the formula, f is the camera focal length, and (x,y) are the horizontal and vertical pixel coordinates, respectively.

[0036] Furthermore, step 3 specifically includes: combining the gimbal output frame angle λ D ,λ T and the target image deviation angle ε D ,ε T Obtain the line-of-sight angle q used to generate guidance commands. D ,q T The calculation formula is:

[0037]

[0038] q D =arcsin(-c3)

[0039] In the formula, q D q represents the elevation angle of the line of sight. T This is the azimuth angle of the line of sight.

[0040] Furthermore, step 4, which describes the design of the multi-rotor guidance law, specifically includes:

[0041] Combining the characteristics of multi-rotor flight, a two-stage guidance process is designed in stationary flight mode;

[0042] The first stage is hovering and heading alignment. After selecting and locking onto the target in the image video, the camera coordinate system outputs the lateral and longitudinal image deviation angles. The gimbal rotates to track the target. At this time, the yaw rate command is designed based on the lateral image deviation angle to align the nose with the target.

[0043]

[0044] After aligning with the target, record the current heading value ψ. c Used for second-stage guidance commands;

[0045] in, For yaw rate command, K ψ This is the yaw rate adjustment coefficient, whose value can be set by the user.

[0046] The second stage is the dynamic interception process, given the combined velocity command V. c Based on the line-of-sight angle calculated above, a three-axis velocity command is generated in the northeast inertial coordinate system:

[0047]

[0048] In the formula, [V Nc V Ec V Dc These are the northbound speed command, the eastbound speed command, and the groundbound speed command, respectively.

[0049] Furthermore, step 5 involves converting the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle. The specific calculation formula is as follows:

[0050]

[0051] In the formula, V fc Forward velocity command, V rc For rightward speed command, V dc This is a ground-direction speed command.

[0052] Furthermore, the flight control integrated navigation system described in step 6 acquires the current northward, eastward, and groundward speed feedback of the UAV, and calculates it based on the actual forward, rightward, and groundward speed feedback in the yaw angle computer body coordinate system using the following specific formula:

[0053]

[0054] In the formula, [V N V E V D [V] is the current northward, eastward, and groundward velocity feedback of the UAV obtained by the flight control integrated navigation system. f V is the actual forward velocity. r V represents the actual velocity to the right. d This represents the actual velocity towards the ground.

[0055] Furthermore, in step 7, the acceleration command for the body coordinate system is obtained through the PID controller, and the specific calculation formula is as follows:

[0056]

[0057] in,

[0058]

[0059] In the formula, e vf Forward velocity error, For the forward acceleration error, e vr For rightward velocity error, For the rightward acceleration error, a fc Forward acceleration command, a rc For rightward acceleration, K pvf K ivf K dvf These are the proportional coefficient, integral coefficient, and derivative coefficient of the forward speed control loop, respectively; K pvr K ivr K dvr These are the proportional coefficient, integral coefficient, and derivative coefficient of the right-hand speed control loop, respectively.

[0060] Further, in step 8, based on the acceleration command of the body coordinate system, the computer calculates the body attitude angle commands, including pitch angle command, roll angle command, and yaw rate command. The specific calculation formula is as follows:

[0061]

[0062] In the formula, θ c For pitch angle command, γ c This is the roll angle command, where g is the acceleration due to gravity.

[0063] Heading tracking heading command ψ c The yaw rate command is:

[0064]

[0065] e ψ =ψ c -ψ

[0066] In the formula, For yaw rate command, K ψ This is the yaw rate adjustment coefficient, whose value can be set by the user, and ψ is the current heading.

[0067] Compared with the prior art, the significant advantages of this invention are:

[0068] (1) The present invention can significantly reduce system costs and effectively reduce system weight.

[0069] (2) The present invention maintains the desired heading unchanged during the tracking process and controls the tracking error by adjusting the lateral position and velocity, thereby improving the system response speed and avoiding large changes in the desired heading angle caused by the rapid changes of the target in the image during terminal guidance, which could lead to loss of target lock.

[0070] (3) The present invention always considers the positional changes of the target in the image when tracking the target, ensuring that no large lateral positional deviation will occur during the entire tracking process, which can effectively improve the accuracy of terminal guidance interception.

[0071] (4) The method proposed in this invention only requires a single-axis gimbal, which is low in cost and light in weight.

[0072] (5) The method proposed in this invention takes into account the error of gimbal locking the target during the guidance process, and has high tracking and interception accuracy.

[0073] (6) The method proposed in this invention keeps the heading unchanged during the tracking process, controls the position error by adjusting the lateral speed, has a low probability of losing the terminal target, and has strong robustness in the tracking process.

[0074] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0075] Figure 1 This is a flowchart of an image-guided interception method for rotary-wing UAVs based on a single-axis gimbal.

[0076] Figure 2 This is a diagram showing the coordinate system transformation relationship in one embodiment.

[0077] Figure 3 This is a diagram showing the transformation from the northeast inertial coordinate system to the body coordinate system in one embodiment.

[0078] Figure 4 This is a diagram showing the transformation from the body coordinate system to the gimbal coordinate system in one embodiment.

[0079] Figure 5 This is a transformation diagram from the gimbal coordinate system to the camera coordinate system in one embodiment.

[0080] Figure 6 This is a diagram showing the transformation from the northeast-northeast coordinate system to the line-of-sight coordinate system in one embodiment.

[0081] Figure 7 Here is a graph showing the speed command and response in one embodiment, where Figure 7 Figures (a) to (c) show the command and response curves for the forward, right, and ground directions, respectively.

[0082] Figure 8 Here is a graph showing the attitude command and response in one embodiment, where Figure 8 Figures (a) to (c) show the roll angle, pitch angle, and yaw angle command and response curves, respectively.

[0083] Figure 9 Here is an image deviation angle curve in one embodiment, wherein Figure 9 (a) in the figure is the target image deviation angle curve at the lateral angle. Figure 9 (b) in the figure is the target image deviation angle curve at the longitudinal angle.

[0084] Figure 10 This is a path diagram for guiding and intercepting a multi-rotor UAV in one embodiment. Detailed Implementation

[0085] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0086] It should be noted that if the embodiments of the present invention involve descriptions such as "first" and "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0087] In one embodiment, combined Figure 1 This paper provides an image-guided interception method for rotary-wing UAVs based on a single-axis gimbal. The method combines image information to design a multi-rotor guidance law and employs a dual-loop PID controller to achieve guidance law tracking. Specifically, it includes:

[0088] Step 1: Establish the necessary coordinate systems for the guidance law design, including the northeast inertial coordinate system, the body coordinate system, the gimbal coordinate system, and the line-of-sight coordinate system;

[0089] Step 2: Define the transformation relationships between the coordinate systems;

[0090] Step 3: Extract the line-of-sight angle used to generate guidance commands based on the coordinate system transformation relationship;

[0091] Step 4: Design the multi-rotor guidance law to obtain the northward speed command, the eastward speed command, and the ground speed command, denoted as the NE-G ground speed command;

[0092] Step 5: Convert the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle.

[0093] Step 6: The flight control integrated navigation system obtains the current northward, eastward, and groundward speed feedback of the UAV, and calculates the actual forward, rightward, and groundward speed feedback based on the yaw angle computer body coordinate system.

[0094] Step 7: Based on the results of Steps 5 and 6, obtain the acceleration command of the body coordinate system through the PID controller;

[0095] Step 8: Based on the acceleration command of the body coordinate system, calculate the body attitude angle command, including pitch angle command, roll angle command and yaw rate command;

[0096] Step 9: Based on the aircraft attitude angle command, control the UAV to achieve guided interception.

[0097] Furthermore, in one embodiment, step 1, establishing the coordinate system necessary for the guidance law design, specifically includes:

[0098] Define a northeast-central inertial coordinate system, with the UAV's takeoff point as the origin A, Ax N The axis coincides with the minor semi-axis of the Earth's ellipsoid, that is, along the northward direction, Ay E Coinciding with the semi-major axis of the ellipsoid, i.e., along the eastward direction, Az D The axis coincides with the normal to the ellipsoid, with downwards being positive, i.e., along the Earth's direction;

[0099] Define the body coordinate system, with the UAV's center of mass as the origin O, Ox B The axis is located within the UAV's reference plane, parallel to the fuselage axis, and points forward of the aircraft. B The axis is located within the longitudinal symmetry plane of the UAV and is perpendicular to Ox. B The axis pointing downwards is positive, Oy B The axis conforms to the right-hand rule;

[0100] Define the gimbal coordinate system, with the origin O. F At the center of the camera's image, O F x F The axis is the optical axis, pointing forward of the camera is positive, O Fz F The axis is perpendicular to O in the longitudinal plane of the camera. F x F And downward is positive, O F y F The axes conform to the right-hand rule; define the camera coordinate system with origin O. L At the center of the camera's image, O L x L Axis at O L On the line connecting to the target point, and pointing positively towards the target, O L z L The axis is perpendicular to O in the longitudinal plane of the camera. L x L The axis is downward, and positive is downward. L y L The axis conforms to the right-hand rule;

[0101] Define a line-of-sight coordinate system with the origin O. S At the center of the camera's image, O S x S Axis at O S On the line connecting to the target point, and pointing positively towards the target, O S z S The axis is perpendicular to O in the vertical plane at the current position of the drone. S x S The axis is downward, and positive is downward. S y S The axis conforms to the right-hand rule.

[0102] Furthermore, in one embodiment, step 2, which defines the transformation relationships between the coordinate systems, is combined with... Figures 2 to 6 Specifically, it includes:

[0103] Rotate the northeast inertial coordinate system to the body coordinate system, and then rotate around z in sequence. D y' x B The rotation matrix for the axis of rotation—yaw angle ψ, pitch angle θ, and roll angle γ—is shown in ① below, where y' is the rotation around z. D Updated y after axis rotation yaw angle ψ E The axis; the body coordinate system rotates to the gimbal coordinate system, sequentially around the z-axis. B y F Axis rotation horizontal frame angle λ T and pitch frame angle λ D The rotation matrix shown in ② below; rotating from the gimbal coordinate system to the camera coordinate system, respectively around z. F y S Axis rotation lateral image deviation angle ε T and longitudinal image deviation angle ε DThe rotation matrix is ​​shown in ③ below; from the northeast inertial coordinate system to the line-of-sight coordinate system, the rotations are respectively around z. D y S Axis rotation line of sight azimuth angle q T and the height angle of the line of sight q D The rotation matrix is ​​shown in ④ below;

[0104] ① Rotation matrix of northeast inertial coordinate system to body coordinate system

[0105]

[0106] In the formula, θ is the pitch angle of the aircraft, γ is the roll angle of the aircraft, and ψ is the yaw angle of the aircraft;

[0107] ② Rotation matrix from body coordinate system to gimbal coordinate system

[0108]

[0109] In the formula, λ D λ is the angle of the gimbal's pitch frame. T This is the yaw angle of the gimbal frame; for a single-axis gimbal, this angle is always 0.

[0110] ③ Rotation matrix from gimbal coordinate system to camera coordinate system

[0111]

[0112] In the formula, ε T ε is the lateral image deviation angle. D The vertical image deviation angle;

[0113] ④ Rotation matrix of the northeast inertial coordinate system to the line-of-sight coordinate system

[0114]

[0115] In the formula, q D q represents the elevation angle of the line of sight. T This is the azimuth angle of the line of sight.

[0116] Here, the image deviation angle is defined as the angle between the camera's optical axis and the line-of-sight axis connecting the camera and the target, and is calculated as follows:

[0117]

[0118] In the formula, f is the camera focal length, and (x,y) are the horizontal and vertical pixel coordinates, respectively.

[0119] Furthermore, in one embodiment, the line-of-sight angle is extracted based on coordinate system transformation relationships. As defined by coordinate system definitions, the line-of-sight coordinate system and the camera coordinate system are not the same concept; they only coincide along the line connecting the machine and the target, i.e., the x-axis coincides, while the y-axis and z-axis do not. In step 3, the angle λ of the gimbal output frame is combined... D ,λ T and the target image deviation angle ε D ,ε T Obtain the line-of-sight angle q used to generate guidance commands. D ,q T The calculation formula is:

[0120]

[0121] q D =arcsin(-c3)

[0122] In the formula, q D q represents the elevation angle of the line of sight. T This is the azimuth angle of the line of sight.

[0123] Furthermore, in one embodiment, step 4, designing the multi-rotor guidance law, specifically includes:

[0124] Combining the characteristics of multi-rotor flight, a two-stage guidance process is designed in stationary flight mode;

[0125] The first stage is hovering and heading alignment. After selecting and locking onto the target in the image video, the camera coordinate system outputs the lateral and longitudinal image deviation angles. The gimbal rotates to track the target. At this time, the yaw rate command is designed based on the lateral image deviation angle to align the nose with the target.

[0126]

[0127] After aligning with the target, record the current heading value ψ. c Used for second-stage guidance commands;

[0128] in, For yaw rate command, K ψ This is the yaw rate adjustment coefficient, whose value can be set by the user.

[0129] The second stage is the dynamic interception process, given the combined velocity command V. c Based on the line-of-sight angle calculated above, a three-axis velocity command is generated in the northeast inertial coordinate system:

[0130]

[0131] In the formula, [V Nc V Ec VDc These are the northbound speed command, the eastbound speed command, and the groundbound speed command, respectively.

[0132] Furthermore, in one embodiment, step 5 involves converting the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle. The specific calculation formula is as follows:

[0133]

[0134] In the formula, V fc Forward velocity command, V rc For rightward speed command, V dc This is a ground-direction speed command.

[0135] Furthermore, in one embodiment, the flight control integrated navigation system described in step 6 obtains the current northward, eastward, and groundward speed feedback of the UAV, and calculates it based on the actual forward, rightward, and groundward speed feedback in the yaw angle computer body coordinate system using the following specific formula:

[0136]

[0137] In the formula, [V N V E V D [V] is the current northward, eastward, and groundward velocity feedback of the UAV obtained by the flight control integrated navigation system. f V is the actual forward velocity. r V represents the actual velocity to the right. d This represents the actual velocity towards the ground.

[0138] Furthermore, in one embodiment, step 7 involves obtaining the body coordinate system acceleration command through a PID controller, and the specific calculation formula is as follows:

[0139]

[0140] in,

[0141]

[0142] In the formula, e vf Forward velocity error, For the forward acceleration error, e vr For rightward velocity error, For the rightward acceleration error, a fc Forward acceleration command, a rc For rightward acceleration, K pvf K ivf K dvf These are the proportional coefficient, integral coefficient, and derivative coefficient of the forward speed control loop, respectively; K pvrK ivr K dvr These are the proportional coefficient, integral coefficient, and derivative coefficient of the right-hand speed control loop, respectively.

[0143] Furthermore, in one embodiment, step 8 calculates the body attitude angle commands, including pitch angle commands, roll angle commands, and yaw rate commands, based on the acceleration commands of the body coordinate system. The specific calculation formula is as follows:

[0144]

[0145] In the formula, θ c For pitch angle command, γ c This is the roll angle command, where g is the acceleration due to gravity.

[0146] Heading tracking heading command ψ c The yaw rate command is:

[0147]

[0148] e ψ =ψ c -ψ

[0149] In the formula, For yaw rate command, K ψ This is the yaw rate adjustment coefficient, whose value can be set by the user, and ψ is the current heading.

[0150] In one embodiment, a rotary-wing unmanned aerial vehicle (UAV) image-guided interception system based on a single-axis gimbal is provided, the system comprising sequentially executing:

[0151] The first module is used to establish the coordinate systems necessary for the design of the guidance law, including the northeast inertial coordinate system, the body coordinate system, the gimbal coordinate system, and the line-of-sight coordinate system.

[0152] The second module is used to define the transformation relationships between different coordinate systems;

[0153] The third module is used to extract the line-of-sight angle for generating guidance commands based on the coordinate system transformation relationship;

[0154] The fourth module is used to design the multi-rotor guidance law and obtain the northward speed command, the eastward speed command, and the ground speed command, denoted as the NE-G ground speed command.

[0155] The fifth module is used to convert the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle.

[0156] The sixth module is used to obtain the current northward, eastward, and groundward speed feedback of the UAV through the flight control integrated navigation system, and to obtain the actual forward, rightward, and groundward speed feedback based on the yaw angle computer body coordinate system.

[0157] The seventh module is used to obtain the body coordinate system acceleration command through the PID controller based on the results of the fifth and sixth modules;

[0158] The eighth module is used to calculate the body attitude angle commands, including pitch angle commands, roll angle commands, and yaw rate commands, based on the acceleration commands of the body coordinate system.

[0159] The ninth module is used to control the UAV based on the body attitude angle command to achieve guided interception.

[0160] Specific limitations regarding the image-guided interception system for rotary-wing UAVs based on a single-axis gimbal can be found in the limitations of the image-guided interception method for rotary-wing UAVs based on a single-axis gimbal mentioned above, and will not be repeated here. Each module in the aforementioned image-guided interception system for rotary-wing UAVs based on a single-axis gimbal can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0161] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements:

[0162] Step 1: Establish the necessary coordinate systems for the guidance law design, including the northeast inertial coordinate system, the body coordinate system, the gimbal coordinate system, and the line-of-sight coordinate system;

[0163] Step 2: Define the transformation relationships between the coordinate systems;

[0164] Step 3: Extract the line-of-sight angle used to generate guidance commands based on the coordinate system transformation relationship;

[0165] Step 4: Design the multi-rotor guidance law to obtain the northward speed command, the eastward speed command, and the ground speed command, denoted as the NE-G ground speed command;

[0166] Step 5: Convert the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle.

[0167] Step 6: The flight control integrated navigation system obtains the current northward, eastward, and groundward speed feedback of the UAV, and calculates the actual forward, rightward, and groundward speed feedback based on the yaw angle computer body coordinate system.

[0168] Step 7: Based on the results of Steps 5 and 6, obtain the acceleration command of the body coordinate system through the PID controller;

[0169] Step 8: Based on the acceleration command of the body coordinate system, calculate the body attitude angle command, including pitch angle command, roll angle command and yaw rate command;

[0170] Step 9: Based on the aircraft attitude angle command, control the UAV to achieve guided interception.

[0171] For specific limitations on each step, please refer to the limitations on the image-guided interception method for rotary-wing UAVs based on a single-axis gimbal mentioned above, which will not be repeated here.

[0172] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, the computer program being implemented when executed by a processor:

[0173] Step 1: Establish the necessary coordinate systems for the guidance law design, including the northeast inertial coordinate system, the body coordinate system, the gimbal coordinate system, and the line-of-sight coordinate system;

[0174] Step 2: Define the transformation relationships between the coordinate systems;

[0175] Step 3: Extract the line-of-sight angle used to generate guidance commands based on the coordinate system transformation relationship;

[0176] Step 4: Design the multi-rotor guidance law to obtain the northward speed command, the eastward speed command, and the ground speed command, denoted as the NE-G ground speed command;

[0177] Step 5: Convert the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle.

[0178] Step 6: The flight control integrated navigation system obtains the current northward, eastward, and groundward speed feedback of the UAV, and calculates the actual forward, rightward, and groundward speed feedback based on the yaw angle computer body coordinate system.

[0179] Step 7: Based on the results of Steps 5 and 6, obtain the acceleration command of the body coordinate system through the PID controller;

[0180] Step 8: Based on the acceleration command of the body coordinate system, calculate the body attitude angle command, including pitch angle command, roll angle command and yaw rate command;

[0181] Step 9: Based on the aircraft attitude angle command, control the UAV to achieve guided interception.

[0182] For specific limitations on each step, please refer to the limitations on the image-guided interception method for rotary-wing UAVs based on a single-axis gimbal mentioned above, which will not be repeated here.

[0183] As a specific example, the invention will be further verified and illustrated in one embodiment.

[0184] This embodiment employs a quadcopter UAV equipped with a single-axis pitch gimbal. During flight, the ground control terminal monitors the video stream transmitted back by the gimbal in real time. After selecting a target, it locks onto it and enters the guidance and interception mode, obtaining the real-time image deviation angle. The gimbal adjusts its pitch direction in real time to track the target, controlling the longitudinal image deviation angle to 0. The UAV then performs autonomous image-guided interception. During flight, the image deviation angle is acquired and fed back in real time. The gimbal adjusts its pitch angle to lock the target on the midline and feeds back the real-time frame angle. Using the image guidance algorithm proposed in this paper, the line-of-sight azimuth and elevation angles are calculated by combining the UAV's attitude angle, gimbal angle, frame angle, and target image deviation angle. Based on the rotation matrix composed of the azimuth and elevation angles, the given desired velocity vector is decomposed into three velocity command components in the NE-G coordinate system. These components are then fed into the velocity controller to obtain the NE-G acceleration expectation, which is then used to calculate the attitude angle command and input into the attitude controller to form the angular velocity command. Finally, the angular velocity control loop completes the closed-loop control. Through the cascade controller, the UAV can quickly and accurately track the guidance command during flight, ultimately guiding the UAV to hit the target.

[0185] The actual flight data curve of this method is as follows: Figure 7-10 As shown, Figure 7 The curves showing the relationship between the guidance commands generated by this method and the actual flight speed demonstrate that the speed controller can stably and accurately track the speed commands. Figure 8 As the attitude controller input and attitude response results, flight data shows that the attitude control can track the control command well, thereby achieving accurate tracking of the speed command. At the same time, the yaw angle control remains constant using this method, and the flight results show that the heading tracking effect is good. Figure 9 As shown in the image deviation angle curve, it can be seen that when the target is not locked in the center of the image, this method takes into account the image deviation, which can further reduce the overall system error and improve guidance accuracy. Figure 10 The image shows the flight trajectory of the UAV during a real-world interception test. The red dot represents the target position, and the blue line represents the three-dimensional flight trajectory of the UAV. The flight test results show that the flight trajectory is continuous and smooth under the conditions of this method, and it can accurately hit the target.

[0186] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. A method for image-guided interception of multi-rotor UAVs based on a single-axis gimbal, characterized in that, The method combines image information to design a multi-rotor guidance law and uses a dual-loop PID controller to achieve guidance law tracking, specifically including: Step 1: Establish the necessary coordinate systems for the guidance law design, including the northeast inertial coordinate system, the body coordinate system, the gimbal coordinate system, and the line-of-sight coordinate system; Step 2: Define the transformation relationships between the coordinate systems; Step 3: Extract the line-of-sight angle used to generate guidance commands based on the coordinate system transformation relationship; Step 4: Design the multi-rotor guidance law to obtain the northward speed command, the eastward speed command, and the ground speed command, denoted as the NE-G ground speed command; Step 5: Convert the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle. Step 6: The flight control integrated navigation system obtains the current northward, eastward, and groundward speed feedback of the UAV, and calculates the actual forward, rightward, and groundward speed feedback based on the yaw angle computer body coordinate system. Step 7: Based on the results of Steps 5 and 6, obtain the acceleration command of the body coordinate system through the PID controller; Step 8: Based on the acceleration command of the body coordinate system, calculate the body attitude angle command, including pitch angle command, roll angle command and yaw rate command; Step 9: Based on the aircraft attitude angle command, control the UAV to achieve guided interception.

2. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 1, characterized in that, Step 1, establishing the necessary coordinate system for the guidance law design, specifically includes: Define a northeast-central inertial coordinate system, with the UAV's takeoff point as the origin A, Ax N The axis coincides with the minor semi-axis of the Earth's ellipsoid, that is, along the northward direction, Ay E Coinciding with the semi-major axis of the ellipsoid, i.e., along the eastward direction, Az D The axis coincides with the normal to the ellipsoid, with downwards being positive, i.e., along the Earth's direction; Define the body coordinate system, with the UAV's center of mass as the origin O, Ox B The axis is located within the UAV's reference plane, parallel to the fuselage axis, and points forward of the aircraft. B The axis is located within the longitudinal symmetry plane of the UAV and is perpendicular to Ox. B The axis pointing downwards is positive, Oy B The axis conforms to the right-hand rule; Define the gimbal coordinate system, with the origin O. F At the center of the camera's image, O F x F The axis is the optical axis, pointing forward of the camera is positive, O F z F The axis is perpendicular to O in the longitudinal plane of the camera. F x F And downward is positive, O F y F The axes conform to the right-hand rule; define the camera coordinate system with origin O. L At the center of the camera's image, O L x L Axis at O L On the line connecting to the target point, and pointing positively towards the target, O L z L The axis is perpendicular to O in the longitudinal plane of the camera. L x L The axis is downward, and positive is downward. L y L The axis conforms to the right-hand rule; Define a line-of-sight coordinate system with the origin O. S At the center of the camera's image, O S x S Axis at O S On the line connecting to the target point, and pointing positively towards the target, O S z S The axis is perpendicular to O in the vertical plane at the current position of the drone. S x S The axis is downward, and positive is downward. S y S The axis conforms to the right-hand rule.

3. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 1, characterized in that, Step 2, which defines the transformation relationships between the coordinate systems, specifically includes: Rotate the northeast inertial coordinate system to the body coordinate system, and then rotate around z in sequence. D y' x B The rotation matrix for the axis of rotation—yaw angle ψ, pitch angle θ, and roll angle γ—is shown in ① below, where y' is the rotation around z. D Updated y after axis rotation yaw angle ψ E The axis; the body coordinate system rotates to the gimbal coordinate system, sequentially around the z-axis. B y F Axis rotation horizontal frame angle λ T and pitch frame angle λ D The rotation matrix shown in ② below; rotating from the gimbal coordinate system to the camera coordinate system, respectively around z. F y S Axis rotation lateral image deviation angle ε T and longitudinal image deviation angle ε D The rotation matrix is ​​shown in ③ below; from the northeast inertial coordinate system to the line-of-sight coordinate system, the rotations are respectively around z. D y S Axis rotation line of sight azimuth angle q T and the height angle of the line of sight q D The rotation matrix is ​​shown in ④ below; ① Rotation matrix of northeast inertial coordinate system to body coordinate system In the formula, θ is the pitch angle of the aircraft, γ is the roll angle of the aircraft, and ψ is the yaw angle of the aircraft; ② Rotation matrix from body coordinate system to gimbal coordinate system In the formula, λ D λ is the angle of the gimbal's pitch frame. T This is the yaw angle of the gimbal frame; for a single-axis gimbal, this angle is always 0. ③ Rotation matrix from gimbal coordinate system to camera coordinate system In the formula, ε T ε is the lateral image deviation angle. D The vertical image deviation angle; ④ Rotation matrix of the northeast inertial coordinate system to the line-of-sight coordinate system In the formula, q D q represents the elevation angle of the line of sight. T This is the azimuth angle of the line of sight.

4. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 3, characterized in that, Image deviation angle is defined as the angle between the camera's optical axis and the line-of-sight axis connecting the camera and the target. It is calculated as follows: In the formula, f is the camera focal length, and (x,y) are the horizontal and vertical pixel coordinates, respectively.

5. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 3, characterized in that, Step 3 specifically includes: combining the gimbal output frame angle λ D ,λ T and the target image deviation angle ε D ,ε T Obtain the line-of-sight angle q used to generate guidance commands. D ,q T The calculation formula is: q D arcsin(-c3) In the formula, q D q represents the elevation angle of the line of sight. T This is the azimuth angle of the line of sight.

6. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 5, characterized in that, Step 4, which describes the design of the multi-rotor guidance law, specifically includes: Combining the characteristics of multi-rotor flight, a two-stage guidance process is designed in stationary flight mode; The first stage is hovering and heading alignment. After selecting and locking onto the target in the image video, the camera coordinate system outputs the lateral and longitudinal image deviation angles. The gimbal rotates to track the target. At this time, the yaw rate command is designed based on the lateral image deviation angle to align the nose with the target. After aligning with the target, record the current heading value ψ. c Used for second-stage guidance commands; in, For yaw rate command, K ψ This is the yaw rate adjustment coefficient, whose value can be set by the user. The second stage is the dynamic interception process, given the combined velocity command V. c Based on the line-of-sight angle calculated above, a three-axis velocity command is generated in the northeast inertial coordinate system: In the formula, [V Nc V Ec V Dc These are the northbound speed command, the eastbound speed command, and the groundbound speed command, respectively.

7. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 6, characterized in that, Step 5 describes converting the northeast ground speed command into forward, right, and ground speed commands in the body coordinate system using the yaw angle. The specific calculation formula is as follows: In the formula, V fc Forward velocity command, V rc For rightward speed command, V dc This is a ground-direction speed command.

8. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 7, characterized in that, Step 6 describes the flight control integrated navigation system acquiring the UAV's current north, east, and ground speed feedback. Based on the yaw angle and the actual forward, right, and ground speed feedback in the body coordinate system, the specific calculation formula is as follows: In the formula, [V N V E V D [V] is the current northward, eastward, and groundward velocity feedback of the UAV obtained by the flight control integrated navigation system. f V is the actual forward velocity. r V represents the actual velocity to the right. d This represents the actual velocity towards the ground.

9. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 8, characterized in that, Step 7 describes obtaining the body coordinate system acceleration command through a PID controller. The specific calculation formula is as follows: in, In the formula, e vf Forward velocity error, For the forward acceleration error, e vr For rightward velocity error, For the rightward acceleration error, a fc Forward acceleration command, a rc For rightward acceleration, K pvf K ivf K dvf These are the proportional coefficient, integral coefficient, and derivative coefficient of the forward speed control loop, respectively; K pvr K ivr K dvr These are the proportional coefficient, integral coefficient, and derivative coefficient of the right-hand speed control loop, respectively.

10. The image-guided interception method for multi-rotor UAVs based on a single-axis gimbal according to claim 9, characterized in that, Step 8: Based on the acceleration command in the body coordinate system, calculate the body attitude angle commands, including pitch angle command, roll angle command, and yaw rate command. The specific calculation formula is as follows: In the formula, θ c For pitch angle command, γ c This is the roll angle command, where g is the acceleration due to gravity. Heading tracking heading command ψ c The yaw rate command is: e ψ =ψ c -ψ In the formula, For yaw rate command, K ψ This is the yaw rate adjustment coefficient, whose value can be set by the user, and ψ is the current heading.

Images