CN204341410U - A kind of flight control system of Shipborne UAV autonomous landing on the ship - Google Patents

Abstract

The utility model discloses a flight control system for autonomous landing of a ship-borne unmanned aerial vehicle. The precise height of the unmanned aerial vehicle can be obtained through data fusion of a laser altitude sensor and a barometric altimeter, and the unmanned aerial vehicle and a ship-borne platform can be obtained through differential GPS. Based on the above information and the expected flight trajectory of the UAV, the airborne flight control system can calculate the size of the aileron, elevator, throttle and rudder, and control the UAV to land on the ship according to the predetermined trajectory. The control scheme uses laser altitude sensor and barometric altimeter data fusion to obtain the height of the UAV, which is faster and more accurate than the altitude measured by the traditional barometric altimeter; the flight control law uses a total energy control system with pitch angle negative feedback. The single-input single-output controller can control the altitude and speed more accurately. Compared with the total energy control system without pitch angle negative feedback, the advantage is that it can control the drone's glide and landing attitude, ensuring the flight safety of the drone.

Description

A flight control system for autonomous landing of ship-borne UAV

technical field

The utility model relates to the field of flight control, in particular to a flight control system for autonomous landing of a ship-borne unmanned aerial vehicle.

Background technique

The successful landing of a UAV on an aircraft carrier is a very complex control task. Among them, the control of altitude and speed is the key to successful landing. Since the aircraft carrier has been moving forward and the speed is not fixed, the trajectory of the UAV's descent has been changing. In addition, unlike road-based aircraft, carrier-based aircraft keep the throttle at the maximum during the descent phase and the moment they touch the ship, the flight speed is faster, and the altitude drop rate is also larger. Therefore, the altitude control of the drone must be fast and accurate. In addition, in order to ensure that the main landing gear touches the ship first, the shipborne UAV needs to maintain a pitch angle greater than zero during the descent phase.

Altitude control in the autonomous landing process of carrier-based UAV has become one of the core technologies of carrier-based aircraft autonomous flight control system. In the existing documents that can be consulted, some use altitude to control the elevator, airspeed to control the throttle, some use altitude to control the throttle, and airspeed to control the elevator, and some introduce visual control, but these materials do not comprehensively consider altitude, airspeed As well as the pitching attitude of the aircraft, it cannot control the autonomous landing of the ship-borne drone very well.

Utility model content

The technical problem to be solved by the utility model is to provide a flight control system for autonomous landing of a ship-borne UAV aiming at the defects involved in the background technology.

The utility model adopts the following technical solutions for solving the problems of the technologies described above:

A flight control system for autonomous landing of a ship-borne UAV, including an on-board control module and a guidance module, wherein:

The guidance module is set on the ship and includes a differential GPS base station and shipboard wireless data transmission;

The differential GPS base station is used to send carrier phase information and base station coordinate information to the differential GPS mobile station;

The airborne control module is arranged on the unmanned aerial vehicle and includes a laser height sensor, a differential GPS mobile station, an autopilot, and airborne wireless data transmission;

The differential GPS mobile station is used to receive the carrier phase of the GPS satellite and the information from the differential GPS base station, and form the phase difference observation value for real-time processing, and provide the GPS coordinates of the autopilot drone and the ship;

The laser height sensor is used to measure the height of the drone;

The autopilot is used to control the UAV to slide down and fly according to the preset landing track according to the differential GPS position information and the height of the UAV;

The shipboard wireless data transmission and airborne wireless data transmission are based on wireless communication.

As a further optimization scheme of the flight control system for autonomous landing of a shipborne UAV in the utility model, the autopilot includes a trajectory loop controller and an attitude loop controller, and the trajectory loop controller is used to calculate the UAV The expected throttle, expected pitch angle, and roll angle; the attitude loop controller is used to calculate the size of the aileron and elevator of the drone.

As a further optimization scheme of the flight control system for autonomous landing of a shipborne UAV in the utility model, the differential GPS base station and the differential GPS mobile station both adopt high-precision differential GPS supporting carrier phase differential technology.

As a further optimization scheme of the flight control system of a ship-borne unmanned aerial vehicle autonomous landing of the utility model, the ship-borne wireless data transmission and airborne wireless data transmission adopt one of 3G data transmission, 433MHz radio station, and 900MHz radio station .

As a further optimization scheme of the flight control system for autonomous landing of a ship-borne UAV in the utility model, the laser height sensor is installed on the self-stabilizing platform directly below the center of gravity of the UAV.

Compared with the prior art by adopting the above technical scheme, the utility model has the following technical effects:

1. Due to the use of laser altitude sensor and barometric altimeter data fusion in the control system, compared with using barometric altimeter alone, the accuracy is higher and the data output rate is faster;

2. Due to the adoption of the total energy control algorithm with pitch angle negative feedback, the height and speed of the carrier-based UAV can be decoupled during the descent phase, and the pitch angle is always kept fixed during the landing process, without the need for final leveling During the process, the accuracy of the touch point position is higher, and the touch attitude also ensures the safety of the UAV;

3. The calculation method of the height of the ship-borne UAV in this utility model can increase the height control accuracy, and ensure that the main landing gear touches the ship first when the ship-borne UAV touches the ship, which is beneficial to the safety of the ship-borne UAV and the ship.

The utility model method disclosed in this paper proves to be effective through flight tests. The test flight situation is as follows: the unmanned aerial vehicle platform uses a propeller front-pull conventional layout aircraft with a wingspan of 3m and a take-off weight of 10kg. Necessary sensors such as airborne barometric altimeter, laser range finder, airspeed meter and autopilot. There is a rope on the ground that moves at a fixed speed, simulating the horizontal movement of the deck. The longitudinal control of the autopilot adopts the total energy control system based on pitch angle negative feedback proposed in this paper. After several flight tests, the small UAV can land accurately, and the main landing gear touches the ground first at the moment of landing, the pitch angle is greater than zero, and the nose propeller does not wipe the ground.

Description of drawings

Figure 1 is a schematic structural diagram of the autonomous landing flight control system of a ship-borne UAV;

Figure 2 is a schematic diagram of the control system software structure;

Fig. 3 is a schematic structural diagram of the original total energy control system;

Fig. 4 is a schematic structural diagram of a total energy control system with pitch angle negative feedback.

Detailed ways

Below in conjunction with accompanying drawing, the technical scheme of the utility model is described in further detail:

As shown in Figure 1, the utility model discloses a flight control system for autonomous landing of a ship-borne UAV, including an on-board control module and a guidance module, wherein:

The guidance module is set on the ship and includes a differential GPS base station and shipboard wireless data transmission;

The differential GPS base station is used to send carrier phase information and base station coordinate information to the differential GPS mobile station;

The airborne control module is arranged on the unmanned aerial vehicle and includes a laser height sensor, a differential GPS mobile station, an autopilot, and airborne wireless data transmission;

The differential GPS mobile station is used to receive the carrier phase of the GPS satellite and the information from the differential GPS base station, and form the phase difference observation value for real-time processing, and provide the GPS coordinates of the autopilot drone and the ship;

The laser height sensor is used to measure the height of the drone;

The autopilot is used to control the UAV to slide down and fly according to the preset landing track according to the differential GPS position information and the height of the UAV;

The shipboard wireless data transmission and airborne wireless data transmission are based on wireless communication.

The autopilot includes a trajectory loop controller and an attitude loop controller, and the trajectory loop controller is used to calculate the desired throttle, desired pitch angle, and roll angle of the unmanned aerial vehicle; the attitude loop controller is used to calculate the unmanned aerial vehicle Aileron, elevator size.

Both the differential GPS base station and the differential GPS mobile station adopt high-precision differential GPS supporting carrier phase differential technology.

The shipboard wireless data transmission and airborne wireless data transmission adopt one of 3G data transmission, 433MHz radio station and 900MHz radio station.

The laser height sensor is installed on the self-stabilizing platform directly below the center of gravity of the drone.

The shipboard guidance module includes two parts: differential GPS base station and shipboard wireless data transmission. The precise GPS information of the differential GPS base station is sent to the airborne control module through the shipboard wireless data transmission.

Differential GPS is the first choice to use the differential GPS reference station with known accurate three-dimensional coordinates to obtain the pseudo-range correction or position correction, and then send this correction to the mobile station in real time or afterwards to correct the measurement data of the differential GPS mobile station , to improve the GPS positioning accuracy. Differential GPS is divided into three categories: position difference, pseudorange difference and carrier phase difference. Among them, the accuracy of carrier phase difference is centimeter level, and the real-time performance is the best, which is most suitable for the position measurement of moving objects. Therefore, as long as the high-precision differential GPS supporting the carrier phase differential technology can be used in the utility model.

The differential GPS base station sends the measured three-dimensional coordinates and the speed in three directions to the airborne control module through wireless data transmission to guide the shipboard UAV to automatically land on the ship.

Wireless data transmission is a device that transmits data wirelessly to another place. Including 3G data transmission, 433MHz radio, 900MHz radio, etc.

The hardware of the airborne control module includes an autopilot, a laser height sensor, a differential GPS mobile station, and an airborne wireless data transmission.

The autopilot is installed on the ship-borne UAV to collect various sensor data and differential GPS position information. Through calculation, the rudder and throttle of the UAV flight can be obtained, so as to control the UAV to slide down according to the preset landing track. flight.

The software structure of the autopilot is divided into two parts: the trajectory loop controller and the attitude loop controller. , and calculate the expected throttle, expected pitch angle, and roll angle of the UAV. The role of the attitude loop controller is to compare the expected pitch angle and roll angle calculated in the previous step with the current pitch angle and roll angle of the UAV, and calculate the size of the aileron and elevator of the UAV.

The principle of the laser height sensor is similar to that of the ultrasonic ranging sensor. The laser emits an optical signal to the target to be measured, and then receives the optical signal reflected by the target. By measuring the round-trip time of the optical signal, the distance of the target is calculated. Because the laser has a single wavelength, extremely fast propagation speed, high measurement accuracy, and the laser range finder has a compact structure and is easy to install and adjust, the laser height sensor is the most ideal instrument for high-precision distance measurement at present.

The differential GPS base station information sends the coordinate information to the airborne control module through wireless data transmission. The laser height sensor is installed on the self-stabilizing gimbal directly below the center of gravity of the drone. The self-stabilizing gimbal ensures that the laser height sensor is always facing the center of the earth without being affected by the attitude of the aircraft.

The principle of the laser height sensor is similar to that of the ultrasonic ranging sensor. The laser emits an optical signal to the target to be measured, and then receives the optical signal reflected by the target. By measuring the round-trip time of the optical signal, the distance of the target is calculated. Due to the single wavelength of the laser, the transmission speed is extremely fast and the measurement accuracy is high. However, the laser height sensor measures the distance between the light source and the reflective surface. When applied to a ship-borne UAV, the violent fluctuation of the sea surface will cause large fluctuations in the value measured by the laser height sensor. In addition, when the ship-borne UAV When flying above the ship, due to the large height difference between the ship-borne platform and the sea surface, the measured value will also fluctuate greatly. The barometric altimeter measures the external air pressure of the sensor. According to the relationship between atmospheric pressure and altitude, the altitude of the barometric altimeter can be obtained. The fluctuation of the sea surface will not cause the barometric altimeter to change, but the barometric altimeter is easily affected by temperature. When the external temperature of the sensor changes , the measured altitude will have a large deviation. Using data fusion technology, the advantages of laser altitude sensor and barometric altimeter can be combined to obtain high-precision altitude data.

The flight control method for autonomous landing of a shipborne UAV includes the following steps:

Step A), obtain the relative position of the UAV and the ship and the movement speed of the ship through differential GPS;

Step B), calculating the height of the drone;

Step C), according to the relative position of the UAV and the ship, the speed of the ship and the height of the UAV, calculate a glide trajectory with a track angle of -3.5 degrees;

Step D), and then control the UAV to slide and land on the ship according to the calculated trajectory.

The specific steps of the step B) are as follows:

Step B.1), using a laser height sensor to measure the laser height of the UAV;

Step B.2), using a barometric altimeter to measure the barometric altitude of the UAV;

Step B.3), when the laser height is greater than 50m, use the barometric height as the height of the UAV;

Step B.4), when the laser height is less than or equal to 50m:

Step B.4.1), filtering and processing the laser height data;

Step B.4.2), calculate the numerical change rate of the laser height; if the change rate is less than or equal to the maximum glide rate of the drone, use the laser height collected this time as the height of the drone; if the change rate is greater than that of the drone If the maximum glide rate of the UAV is higher, the laser altitude collected this time is discarded, and the collected air pressure altitude is compared with the air pressure altitude collected in the previous cycle to obtain the altitude difference, and then the altitude difference is compared with the altitude of the drone in the previous cycle. Add it as the height of the drone.

When the laser height is greater than or equal to 50m, the height data completely adopts the barometric altimeter data;

When the laser height is less than 50m, filter the laser height data, such as mean filtering, α-β filtering, etc., and calculate the change rate of the laser height value. If the change rate exceeds the maximum glide rate of the drone, the height data is considered equal to the previous value. The sum of the altitude of the drone in one cycle and the difference in pressure altitude between the two cycles before and after. Because although the barometric altimeter will produce drift in a long period, the rate of change of altitude measured in a short period is relatively accurate. Therefore, this fusion method combines the advantages of the laser altitude sensor that can measure the relative altitude and the advantages of the barometric altitude sensor's short-term data reliability, and provides reliable altitude data for the automatic landing of the UAV.

The software structure of the control system is shown in Figure 2, including a trajectory loop controller and an attitude loop controller. The input of the trajectory loop controller is the desired glide trajectory, and the output is the desired roll angle, pitch angle, throttle, and feedback information Including the current GPS coordinates of the UAV and the GPS coordinates of the shipboard platform, as well as the laser altitude and airspeed measured by the UAV; the input of the attitude loop controller is the expected roll angle, pitch angle and heading, and the output is the aileron, The size of the elevator and rudder, the feedback information includes the current roll angle, pitch angle and heading of the drone.

The longitudinal height and speed control method of the trajectory loop controller is a total energy control system with pitch angle negative feedback. The structural diagram is shown in Figure 4.

Total Energy Control System (TECS) is a control theory that controls aircraft altitude and speed by coordinating aircraft throttle and desired pitch angle. According to theoretical mechanics, the total mechanical energy expression of the aircraft is:

E _T = GV ² /2g + Gh

In the formula, _ET is the total mechanical quantity of the aircraft, which is composed of two parts: the kinetic energy and the potential energy of the aircraft. is the weight of the aircraft, g is the acceleration of gravity, V is the airspeed, h is the flight altitude, GV ² /2g and Gh represent the kinetic energy and gravitational potential energy of the aircraft respectively. The kinetic energy of the aircraft is directly related to the speed of the aircraft, and the gravitational potential energy is directly related to the altitude of the aircraft. Therefore, the velocity and altitude can be converted into kinetic energy and potential energy of the system unit in two different unit physical quantities. TECS takes the expected altitude and actual altitude, expected speed and actual speed of the aircraft as input, and calculates the expected kinetic energy, potential energy and total energy of the aircraft as well as the actual kinetic energy, potential energy and total energy of the aircraft based on these four quantities. Then calculate the size of the expected throttle according to the deviation between the expected total energy of the aircraft and the actual total energy, so as to complete the control of the total energy of the aircraft; according to the expected kinetic energy and actual kinetic energy of the aircraft, as well as the expected potential energy and actual potential energy of the aircraft, calculate the desired pitch angle. Size, so as to complete the distribution of aircraft kinetic energy and potential energy. The structure diagram of the total energy control system is shown in Fig. 3 .

The total energy control system with pitch angle negative feedback introduces the optimal pitch angle for landing into the standard total energy control system, in order to ensure that the aircraft lands at a specific pitch angle. This is very critical in the autonomous landing of ship-borne drones, because the speed of ship-borne drones touching the ship is relatively fast, and the landing gear bears huge force. Only when the main landing gear touches the ship first can the drone's safety Safety. In addition, if the nose landing gear touches the ship first, the attitude of the aircraft will be abnormal, which is very prone to accidents. Therefore, it is necessary to ensure that the UAV maintains a positive pitch angle during the entire descent process.

The structure diagram of the total energy control system with pitch angle negative feedback is shown in Fig. 4. The deviation between the current pitch angle of the aircraft and the optimal landing pitch angle is calculated by the PID controller to obtain the increment of the desired speed, which is added to the initial desired speed as the input of the total energy control system. Assuming that the current pitch angle of the UAV is less than the optimal landing pitch angle, the output of the PID controller is a negative value, so that the expected speed of the total energy control system decreases, the calculated expected throttle decreases, and the expected pitch angle increases. Finally, As a result, the cruising speed of the UAV decreases and the angle of attack increases. When the current pitch angle of the UAV is equal to the optimal landing pitch angle, the expected speed of the total energy control system remains unchanged. At this time, a steady state is reached, and the UAV will slide down at the current attitude and speed, and finally land safely on the ship.

Claims (5)

1. a flight control system for Shipborne UAV autonomous landing on the ship, is characterized in that, comprises onboard control module and bootstrap module, wherein:

Described bootstrap module is arranged on warship, comprises differential GPS base station and carrier-borne wireless data sending;

Described differential GPS base station is for sending carrier phase information and base station coordinate information sends to differential GPS movement station;

Described onboard control module is arranged on unmanned plane, comprises laser elevation sensor, differential GPS movement station, autopilot and airborne wireless number and passes;

Described differential GPS movement station for receiving the carrier phase of gps satellite and carrying out the information of self-differential GPS base station, and forms time-differenced phase observation value and processes in real time, is supplied to the gps coordinate on autopilot unmanned plane and naval vessel;

Described laser elevation sensor is for measuring the height of unmanned plane;

Described autopilot is used for gliding flight by presetting warship track according to the Altitude control unmanned plane of differential GPS location information and unmanned plane;

Described carrier-borne wireless data sending and airborne wireless number pass based on radio communication.

2. the flight control system of Shipborne UAV autonomous landing on the ship according to claim 1, it is characterized in that, described autopilot comprises track ring controller and attitude ring controller, and described track ring controller is for calculating expectation throttle, expectation pitch angle, the roll angle of unmanned plane; Described attitude ring controller is for calculating aileron, the elevating rudder size of unmanned plane.

3. the flight control system of Shipborne UAV autonomous landing on the ship according to claim 1, is characterized in that, described differential GPS base station and differential GPS movement station all adopt the high-precision difference GPS supporting technique of dispersion assign.

4. the flight control system of Shipborne UAV autonomous landing on the ship according to claim 1, is characterized in that, described carrier-borne wireless data sending and airborne wireless number pass the one adopted in 3G number biography, 433MHz radio station, 900MHz radio station.

5. the flight control system of Shipborne UAV autonomous landing on the ship according to claim 1, is characterized in that, described laser elevation sensor be arranged on immediately below unmanned plane center of gravity on steady The Cloud Terrace.