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

Abstract

The present invention relates to a longitudinal trajectory control method and control system for unmanned aerial vehicle (UAV) rope collision recovery, which is suitable for high-precision rope collision recovery of skyhook recovery type UAV. By applying the longitudinal trajectory control method proposed in the present invention, the height and speed can be decoupled and controlled, and the speed, height and pitch angle of the UAV during rope collision recovery are all within the optimal range through attitude constraints. This method can greatly improve the success rate of a rope collision, realize high-precision rope collision point control and speed and attitude control, avoid the increase in time cost and risk caused by frequent go-arounds due to low control accuracy, and avoid wing damage or reduced service life due to inaccurate impact points or excessive speed when hitting the rope. The control method of the present invention greatly improves the height control accuracy and wind resistance under harsh time and speed constraints, improves the success rate of a rope collision, and makes the rope collision point optimal, reduces the probability of damage to the UAV rope collision, and improves the service life.

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 the longitudinal trajectory of a unmanned aerial vehicle (UAV) during a collision with a rope. More specifically, it is a method for realizing high-precision collision with a rope during the recovery phase of a skyhook recovery type UAV through a new height and speed decoupling control. Background Art

[0002] Skyhook recovery drones do not need to use airport runways or carry parachutes for parachute recovery, so they have received great attention in the take-off and landing of small and medium-sized drones. However, compared with taxiing and parachuting drones, the requirements for height and speed during the rope-hitting recovery process are much more stringent. The height control accuracy is generally required to be at least within 1 meter, and the speed must also be controlled within a small range above the safe speed. At present, the vertical direction of the Skyhook recovery drone is mainly controlled by height proportional control during rope-hitting recovery, while the speed generally uses a fixed throttle or a simple proportional control. For drones, the changes in height and speed are mutually coupled. This method of controlling the height channel and the speed channel separately is difficult to achieve the desired accuracy, resulting in a low success rate of a rope-hitting and a high risk of recovery damage. Therefore, it is urgent to invent a longitudinal trajectory control method with height and speed decoupled control to achieve high-precision height control under strong speed constraints, improve the success rate of rope-hitting, 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 longitudinal trajectory control method and control system for UAV collision recovery, which solves the problems of low success rate of one-time collision with the rope and high recovery risk of skyhook recovery of UAV.

[0005] Technical Solution

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

[0007] Step 1: When the skyhook recovery drone enters the recovery mode, the drone slides down from the current altitude to the rope collision altitude, and maintains a constant altitude flight at this altitude to align with the expected rope collision point, that is, the longitudinal control law is the height and speed decoupling control under the condition of pitch angle restriction;

[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 do not meet the requirements, it will exit the recovery mode, turn and climb away from the skyhook, and enter the recovery mode again after a go-around.

[0009] Step 2: If all factors meet the window requirements when the drone reaches the decision window, the drone continues to maintain a fixed altitude flight under the speed constraint until the wing hits the rope. During this period, the longitudinal control law of the drone is the height and speed decoupling control under the pitch angle constraint;

[0010] After the drone hits the rope, the rope slides along the leading edge of the wing to the wing tip and is locked by the metal hook at the wing tip. 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 recovery of the drone by the skyhook.

[0011] The height and speed decoupling control law is:

[0012]

[0013]

[0014] where δ e is the elevator control quantity; Δθ is the pitch angle deviation of the UAV; q is the pitch angle rate; Δh is the height deviation; Δv is the speed deviation. θ is the pitch angle magnification factor; k q is the pitch angle rate magnification factor; k he k is the amplification factor of the elevator for altitude control; ve k is the amplification factor of the elevator on speed control; hi is the height integral control coefficient;

[0015] δ t is the engine throttle control amount; m is the mass of the drone; g is the acceleration of gravity; is the rate of change of height; v is the speed; k is the rate of change of velocity. tp With k ti are the corresponding height and speed decoupling control coefficients respectively.

[0016] A control system for realizing the longitudinal trajectory control method of the unmanned aerial vehicle (UAV) collision rope recovery is characterized by comprising a flight control computer, an angular velocity gyroscope, a heading system and a satellite signal receiver; the input end of the flight control computer is respectively connected to the signals of the speed deviation Δv and the height deviation Δh, and the output end is respectively connected to the elevator servo and the throttle servo of the UAV; the UAV is provided with an angular velocity gyroscope, a heading system and a satellite signal receiver, the angular velocity gyroscope measures the pitch, roll and yaw angular rate signals, the heading system sends the pitch angle and roll angle signals of the UAV to the input end of the flight control computer, and the satellite signal receiver sends the altitude, ground speed and position information of the UAV to the input end of the flight control computer; the flight control computer calculates the elevator control surface deflection angle and the throttle adjustment angle control amount, and controls the elevator servo and the throttle servo connected to the output end.

[0017] The pitch angle, pitch rate, height, speed and other parameters used in the longitudinal trajectory control law can be measured by the corresponding sensors. Each control parameter can be obtained through control law design and simulation. Specifically, the parameter range that meets the control performance is obtained through linear simulation based on time domain and frequency domain analysis, and then the six-degree-of-freedom nonlinear model of the UAV is used to perform time domain analysis and parameter optimization to determine the final parameters.

[0018] Beneficial Effects

[0019] The present invention proposes a method and control system for controlling the longitudinal trajectory of a UAV during a rope collision recovery, which is suitable for high-precision rope collision recovery of a skyhook recovery type UAV. By applying the longitudinal trajectory control method proposed in the present invention, the height and speed can be decoupled and controlled, and the speed, height and pitch angle of the UAV during rope collision recovery can be kept within the optimal range through attitude constraints. This method can greatly improve the success rate of a rope collision, achieve high-precision rope collision point control as well as speed and attitude control, and avoid the time cost and risk increase caused by frequent go-arounds due to low control accuracy, as well as wing damage or reduced service life due to inaccurate impact points or excessive speed when hitting the rope.

[0020] The control method of the present invention greatly improves the altitude control accuracy and wind resistance under harsh time and speed constraints, increases the success rate of a single rope collision, optimizes the rope collision point, reduces the probability of damage to the UAV due to rope collision, and increases its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the recovery process of the drone hitting the rope

[0022] Figure 2 Vertical decision flow chart for the rope recovery process

[0023] Figure 3 Longitudinal control structure diagram for the rope recovery process DETAILED DESCRIPTION

[0024] The present invention will now be further described with reference to the embodiments and the accompanying drawings:

[0025] like Figure 1 and Figure 2As shown in the figure, there are a schematic diagram of the UAV rope-hitting recovery process and a longitudinal decision-making flow chart, respectively. When the skyhook recovers the UAV and enters the recovery mode, the UAV slides down from the current altitude to the rope-hitting altitude, and maintains a constant altitude flight at this altitude aligned with the expected rope-hitting point. When flying to a 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 window requirements, the rope-hitting recovery mode is exited, and the recovery is entered again after a go-around. If all elements meet the window requirements when the UAV reaches the decision window, it continues to maintain a constant altitude flight under speed constraints until the wing hits the rope. During this period, the longitudinal control law of the UAV is a height and speed decoupling control under the condition of pitch angle constraints.

[0026] like Figure 3 As shown in the figure, the longitudinal control structure of the rope recovery process is given. The control system includes the following components: angular rate gyro, heading and attitude system, satellite signal receiver, flight control computer, elevator servo and throttle servo. The angular rate gyro is used to measure the pitch, roll and yaw angular rates of the UAV; the heading and attitude system is used to measure the pitch and roll angles of the UAV; the satellite signal receiver is used to measure the altitude, ground speed and position information of the UAV; the elevator servo and throttle 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 quantity of each channel. In the longitudinal trajectory control system of the rope-impact recovery, the control law program runs in real time in the flight control computer. The pitch rate, pitch angle, altitude, ground speed collected from various sensors and the altitude and ground speed commands obtained from the expected commands are input into the longitudinal trajectory control law, and the elevator control surface deflection angle and throttle adjustment angle control amount are solved to drive the corresponding servo movement, thereby changing the altitude, speed and attitude of the UAV, and adjusting the deviations of these parameters from the expected values ​​to the required range within a limited time, and finally successfully realizing the rope-impact recovery.

[0027] Decoupling control law of height and speed:

[0028]

[0029]

[0030] where δ e is the elevator control quantity; Δθ is the pitch angle deviation of the UAV; q is the pitch angle rate; Δh is the height deviation; Δv is the speed deviation; δ t is the engine throttle control amount; m is the mass of the drone; g is the acceleration of gravity; is the rate of change of height; v is the speed; is the velocity change rate; k θ is the pitch angle magnification factor; k q is the pitch angle rate magnification factor; khe k is the amplification factor of the elevator for altitude control; ve k is the amplification factor of the elevator on speed control; hi is the height integral control coefficient; k tp With k ti are the corresponding decoupling control coefficients. All parameters can be measured by sensors, and all control coefficients can be determined by UAV linearization and six-degree-of-freedom nonlinear simulation.

Claims

1. A method for controlling the longitudinal trajectory of a UAV during rope collision recovery, characterized in that Here are the steps: Step 1: When the skyhook recovery drone enters the recovery mode, the drone slides down from the current altitude to the rope collision altitude, and maintains a constant altitude flight at this altitude to align with the expected rope collision point, that is, the longitudinal control law is the height and speed decoupling control under the condition of pitch angle restriction; 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 do not meet the requirements, it will exit the recovery mode, turn and climb away from the skyhook, and enter the recovery mode again after a go-around. Step 2: If all factors meet the window requirements when the drone reaches the decision window, the drone continues to maintain a fixed altitude flight under the speed constraint until the wing hits the rope. During this period, the longitudinal control law of the drone is the height and speed decoupling control under the pitch angle constraint; After the drone hits the rope, the rope slides along the leading edge of the wing to the wing tip and is locked by the metal hook at the wing tip. 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 recovery of the drone by the skyhook. The height and speed decoupling control law is: where δ e is the elevator control quantity; Δθ is the pitch angle deviation of the UAV; q is the pitch angle rate; Δh is the height deviation; Δv is the speed deviation; k θ is the pitch angle magnification factor; k q is the pitch angle rate magnification factor; k he k is the amplification factor of the elevator for altitude control; ve k is the amplification factor of the elevator on speed control; hi is the height integral control coefficient; δ t is the engine throttle control amount; m is the mass of the drone; g is the acceleration of gravity; is the rate of change of height; v is the speed; is the velocity change rate, k tp With k ti are the corresponding height and speed decoupling control coefficients respectively.

2. A control system for realizing the longitudinal trajectory control method of the UAV collision rope recovery as described in claim 1, characterized in that It includes a flight control computer, an angular velocity gyro, a heading and attitude system and a satellite signal receiver; the input end of the flight control computer is respectively connected to the signals of the speed deviation Δv and the height deviation Δh, and the output end is respectively connected to the elevator servo and throttle servo of the unmanned aerial vehicle; the unmanned aerial vehicle is provided with an angular velocity gyro, a heading and attitude system and a satellite signal receiver, the angular velocity gyro will measure the pitch, roll and yaw angular rate signals, the heading and attitude system sends the pitch angle and roll angle signals of the unmanned aerial vehicle to the input end of the flight control computer, and the satellite signal receiver sends the altitude, ground speed and position information of the unmanned aerial vehicle to the input end of the flight control computer; the flight control computer calculates the elevator control surface deflection angle and the throttle adjustment angle control amount, and controls the elevator servo and throttle servo connected to the output end.

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