A method and control system for controlling the trajectory of a UAV during collision with a rope

Abstract

The present invention relates to a method and control system for controlling the recovery trajectory of a UAV after hitting a rope, and proposes an adaptive trajectory control method based on side-slip stabilization, which can predict before the side wind has a substantial impact on the movement of the UAV body, and take suppression measures to improve the trajectory control sensitivity and control accuracy under the interference of the side wind, realize high-precision trajectory control under the strict time window constraint conditions, improve the success rate of the UAV hitting the rope, and reduce the probability of recovery damage. The trajectory control method proposed by the present invention can greatly improve the success rate of a single hit, realize precise control of the wing hitting the rope point, and effectively avoid the damage to the rope caused by the reduction of control accuracy under wind field interference and the increase in time and fuel costs caused by frequent go-arounds.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle control, and relates to a method and a control system for controlling a trajectory of a UAV that is recovered by hitting a rope. More specifically, it is a method for realizing high-precision trajectory recovery of a skyhook recovery type UAV by using an adaptive anti-crosswind trajectory control law during the recovery phase. Background Art

[0002] Skyhook recovery drones have been increasingly used in small and medium-sized drones because of their good site adaptability and large mission load. However, compared with other take-off and landing drones, the requirements for track control during the rope-impact recovery process are much more stringent. Generally speaking, the track control accuracy is required to be within half of the length of a single wing. The current track control mostly uses PID control or L1 track control methods. These methods can basically meet the requirements in an environment with stable airflow, but when there is a large crosswind interference, the control effect is difficult to meet the recovery requirements, especially when there is a gust of wind interference very close to the rope-impact point. It is difficult for the existing control method to maintain the required track control accuracy under extremely short time constraints. Therefore, it is urgent to invent a track control method that can adaptively suppress large side winds, so as to achieve high-precision track control under the constraint of unstable airflow, improve the success rate of rope-impacting, and reduce the risk of recovery. Summary of the invention

[0003] Technical issues to be solved

[0004] In order to avoid the shortcomings of the prior art, the present invention proposes a UAV collision rope recovery track control method and control system to solve the problem that the track of the skyhook recovery UAV is easily affected by the side wind when the collision rope is recovered, resulting in a low success rate of the collision rope and a high risk of recovery damage.

[0005] Technical Solution

[0006] A method for controlling the trajectory of a UAV by hitting a rope for recovery, characterized by the following steps:

[0007] Step 1: When the hook recovery drone enters the recovery mode, the drone slides down from the current altitude to the rope impact altitude, and at this altitude, it aims at the expected rope impact point to maintain altitude and track flight. The lateral control law is track control under the side slip stabilization constraint;

[0008] When the UAV flies to the decision window at a certain distance from the capture rope, it automatically determines whether the altitude deviation, speed deviation and track deviation meet the window requirements. If any of the elements does not meet the requirements, it will exit the recovery mode and enter the recovery mode again after a go-around.

[0009] Step 2: If all elements meet the window requirements, the drone continues to maintain altitude-fixed, track-controlled flight until the wing hits the rope;

[0010] During this period, the lateral control law of the drone is the track control under the side slip stabilization constraint. After the drone hits the rope, the rope slides along the leading edge of the wing to the wing tip, and the metal hook at the wing tip locks the rope; at this time, the engine stops working, and the drone slows down and swings back under the action of the rope until it finally stops, thus realizing the skyhook return of the drone;

[0011] The track control law is:

[0012]

[0013] δ r =k rψ ×Δψ+k r ×r+k ry ×Δy+k β ×β

[0014] where δ a is the aileron control amount; is the UAV roll angle deviation; p is the roll angle rate; Δψ is the heading angle deviation; Δy is the lateral track deviation; is the roll angle magnification factor; k p is the roll angular rate magnification factor; k aψ k is the aileron's amplification factor for heading angle control; ay k is the aileron's amplification factor for lateral track deviation control; yi is the lateral track deviation integral control coefficient;

[0015] δ r is the rudder control quantity; r is the heading angular rate; β is the sideslip angle; k rψ k is the amplification factor of the rudder on the heading angle control; r is the heading angular rate magnification factor, k ry k is the amplification factor of the rudder on the lateral track deviation control; β is the sideslip angle feedback amplification factor.

[0016] A control system for realizing the unmanned aerial vehicle (UAV) collision rope recovery track control method, characterized by comprising an angular rate gyro, a sideslip angle sensor, a heading attitude system, a satellite signal receiver and a flight control computer; the flight control computer input end is connected to the heading angle and track quantity signal, and the output is connected to the aileron servo and the rudder servo; the unmanned aerial vehicle is provided with an angular rate gyro, a sideslip angle sensor, a heading attitude system and a satellite signal receiver, wherein the angular rate gyro measures the pitch, roll and heading angular rate of the unmanned aerial vehicle; the heading attitude system measures the heading angle, pitch angle and roll angle of the unmanned aerial vehicle; the sideslip angle sensor measures the sideslip angle of the unmanned aerial vehicle; the satellite signal receiver is used to measure the height, ground speed and position information of the unmanned aerial vehicle; the flight control computer solves the control law to obtain the control amount of the control surface deflection of the aileron servo and the rudder servo, and drives the corresponding servo to move.

[0017] Beneficial Effects

[0018] The present invention proposes a method and control system for controlling the trajectory of a UAV that hits a rope and recovers the UAV. The invention proposes an adaptive trajectory control method based on side slip stabilization. The method can be predicted before the side wind has a substantial impact on the movement of the UAV body, and suppression measures can be taken to improve the trajectory control sensitivity and control accuracy under the interference of the side wind, so as to achieve high-precision trajectory control under the strict time window constraint conditions, improve the success rate of the UAV hitting the rope, and reduce the probability of recovery damage. The trajectory control method proposed by the present invention can be used to well maintain the heading and trajectory of the UAV through the coordinated control of the aileron and the rudder, and the UAV can react in advance and quickly suppress the possible side wind within the strict time window of the rope recovery process through side slip angle stabilization, so as to ensure that the trajectory deviation of the UAV does not fluctuate due to wind field disturbances and cannot meet the accuracy requirements. This method can greatly improve the success rate of a rope hit, achieve precise control of the wing rope hit point, and effectively avoid rope hit damage caused by reduced control accuracy under wind field interference and the increase in time and fuel costs caused by frequent go-arounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Decision flow chart for the process control of UAV collision recovery

[0020] Figure 2 This is the trajectory control structure diagram of the UAV rope recovery process DETAILED DESCRIPTION

[0021] The present invention will now be further described with reference to the embodiments and the accompanying drawings:

[0022] like Figure 1As shown in the figure, the control decision process of the UAV hitting the rope recovery process is given. When the hook recovery drone enters the recovery mode, the drone slides down from the current altitude to the rope hitting altitude, and at this altitude, it aligns with the expected rope hitting point to maintain altitude and track flight. When the drone flies to the decision window at a certain distance from the capture rope, it automatically determines whether the altitude deviation, speed deviation and track deviation meet the window requirements. If any element does not meet the requirements, the recovery mode is exited and the recovery is entered again after a go-around. If all elements meet the window requirements, the drone continues to maintain altitude and track flight until the wing hits the rope. During this period, the lateral control law of the drone is track control under the side slip stabilization constraint.

[0023] like Figure 2 As shown in the figure, the track control structure of the UAV collision rope recovery process is given. The control system includes the following components: angular rate gyro, side slip angle sensor, heading system, satellite signal receiver, flight control computer, aileron servo and rudder servo. The angular rate gyro is used to measure the pitch, roll and heading angular rate of the UAV; the heading system is used to measure the heading angle, pitch angle and roll angle of the UAV; the side slip angle sensor measures the sideslip angle of the UAV; the satellite signal receiver is used to measure the altitude, ground speed and position information of the UAV; the aileron servo and rudder servo are used to execute the corresponding servo motion instructions respectively, and the flight control computer is used to collect the measurement information and instruction information of each sensor, solve the control law, and output the control output of each channel. In the rope-impact recovery trajectory control system, the control law program runs in real time in the flight control computer, and the roll rate, roll angle, heading rate, heading angle, position information, sideslip angle collected from various sensors, as well as the heading angle and trajectory instructions obtained from the expected instructions are input into the trajectory control law, and the aileron and rudder surface deflection control quantities are solved to drive the corresponding servos to move, thereby changing the heading and lateral trajectory of the UAV, and adjusting the deviations of these parameters from the expected values ​​to within the required range within a limited time, ultimately achieving successful rope-impact recovery.

[0024] Track control law:

[0025]

[0026] δ r =k rψ ×Δψ+k r ×r+k ry ×Δy+k β ×β

[0027] where δ a is the aileron control amount; is the UAV roll angle deviation; p is the roll angle rate; Δψ is the heading angle deviation; Δy is the lateral track deviation. is the roll angle magnification factor; k pis the roll angular rate magnification factor; k aψ k is the aileron's amplification factor for heading angle control; ay k is the aileron's amplification factor for lateral track deviation control; yi is the lateral track deviation integral control coefficient. r is the rudder control quantity; r is the heading angular rate; β is the sideslip angle; k rψ k is the amplification factor of the rudder on the heading angle control; r is the heading angular rate magnification factor, k ry k is the amplification factor of the rudder on the lateral track deviation control; β is the sideslip angle feedback amplification factor. All parameters can be measured by sensors, and the control coefficients can be determined by linearization and six-degree-of-freedom nonlinear simulation.

Claims

1. A method for controlling the trajectory of a UAV by hitting a rope, characterized in that Here are the steps: Step 1: When the hook recovery drone enters the recovery mode, the drone slides down from the current altitude to the rope impact altitude, and at this altitude, it aims at the expected rope impact point to maintain altitude and track flight. The lateral control law is track control under the side slip stabilization constraint; When the UAV flies to the decision window at a certain distance from the capture rope, it automatically determines whether the altitude deviation, speed deviation and track deviation meet the window requirements. If any of the elements does not meet the requirements, it will exit the recovery mode and enter the recovery mode again after a go-around. Step 2: If all elements meet the window requirements, the drone continues to maintain altitude-fixed, track-controlled flight until the wing hits the rope; During this period, the lateral control law of the UAV is the track control under the side slip stabilization constraint; after the UAV hits the rope, the rope slides along the leading edge of the wing to the wing tip, and the metal hook at the wing tip locks the rope; at this time, the engine stops working, and the UAV slows down and swings back under the action of the rope until it finally stops, thus realizing the recovery of the UAV by the skyhook; The track control law is: δ r =k rψ ×Δψ+k r ×r+k ry ×Δy+k β ×β where δ a is the aileron control amount; is the UAV roll angle deviation; p is the roll angle rate; Δψ is the heading angle deviation; Δy is the lateral track deviation; is the roll angle magnification factor; k p is the roll angular rate magnification factor; k aψ k is the aileron's amplification factor for heading angle control; ay k is the aileron's amplification factor for lateral track deviation control; yi is the lateral track deviation integral control coefficient; δ r is the rudder control quantity; r is the heading angular rate; β is the sideslip angle; k rψ k is the amplification factor of the rudder on the heading angle control; r is the heading angular rate magnification factor, k ry k is the amplification factor of the rudder on the lateral track deviation control; β is the sideslip angle feedback amplification factor.

2. A control system for implementing the UAV collision rope recovery track control method described in claim 1, characterized in that It includes an angular rate gyro, a sideslip angle sensor, a heading attitude system, a satellite signal receiver and a flight control computer; the flight control computer input is connected to the heading angle and track signal, and the output is connected to the aileron servo and the rudder servo; the UAV is equipped with an angular rate gyro, a sideslip angle sensor, a heading attitude system, and a satellite signal receiver, among which the angular rate gyro measures the pitch, roll, and heading angular rate of the UAV; the heading attitude system measures the heading angle, pitch angle, and roll angle of the UAV; The sideslip angle sensor measures the sideslip angle of the drone; the satellite signal receiver is used to measure the altitude, ground speed and position information of the drone; the flight control computer solves the control law to obtain the control amount of the aileron servo and the rudder deflection of the rudder, and drives the corresponding servo movement.

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