CN103241377B - There is the soft wing unmanned vehicle of automatic fog dispersal function - Google Patents

Abstract

The invention provides a soft-wing unmanned aerial vehicle with automatic defogging function, including a flexible stamping parafoil, a structural cabin, a power system, defogging equipment and a control system; the defogging equipment includes a built-in defogging device and an external defogging device The equipment is used to spread the anti-fog agent at the same time or separately. The built-in anti-fog equipment is installed inside the structure cabin, and the external anti-fog equipment is installed outside the structure cabin; The external anti-fog equipment consists of a fixed frame, a dispersing cylinder and an excitation electrode. The anti-fog equipment also includes detection and detection equipment. The present invention has the following beneficial effects: safe and reliable, easy to operate, and large load capacity; through remote control and autonomous navigation, the flight defogging distance range can be as long as 200 kilometers; It can be applied to local fog elimination, such as improving the road traffic environment, eliminating dense fog at airports, and improving the microclimate in disaster relief areas.

Description

Soft-wing unmanned aerial vehicle with automatic defogging function

technical field

The invention relates to the field of unmanned aerial vehicles, in particular to a soft-wing unmanned aerial vehicle with an automatic defogging function.

Background technique

Both drones and unmanned aerial vehicles are unmanned, but there are substantial differences. UAVs have fixed wings and are mostly used for military purposes such as high-altitude reconnaissance and attacking ground targets, and are rarely used for civilian purposes.

In order to meet various needs, people have researched and manufactured various unmanned aerial vehicles. The invention patent ZL 93202125.5 (authorized announcement number CN2204774Y) of the Airborne Forces Research Institute of the Chinese People's Liberation Army discloses a flexible stamped parafoil for powered flight, which is used for flight performances, advertising, frontier patrols and recreational flights. In addition, in the Chinese utility model patent ZL201220565967.0 (authorized announcement number CN 202879795 U), a remote-control powered flexible ram parafoil is used, which can be dragged from the ground by a vehicle or launched from the air, and can be used for surveying and Scouting the situation on the ground, sampling air pollution and monitoring volcanoes, etc. It has the advantages of light weight, low cost and convenient storage.

In the field of aircraft, people try to use unmanned aerial vehicles for artificial fog removal. The so-called artificial fog removal refers to the method of eliminating fog droplets in a local area by artificial influence to improve visibility. Specifically, certain equipment is used to spread catalysts such as silver iodide, dry ice, and liquefied propane into the fog to generate a large number of ice crystals. The water in the original fog droplets grows continuously, and the ice crystals grow and fall to the ground, so that the fog disappears.

At present, there are mainly the following ways to spread catalyst to eliminate fog:

The first is aircraft sowing: the use of transport aircraft or light aircraft to carry anti-fog agents for spraying on or in the fog is currently the main means of anti-fog. The advantage is that it can carry out rapid and large-area defogging operations. However, there are many deficiencies in aircraft fog removal. First of all, the risk of aircraft taking off and landing and operating in foggy weather is relatively high, which will endanger the safety of the aircraft and the pilot; when it comes to aircraft sowing, the route permit and ground command are very complicated; the flying and sowing altitude of the aircraft is high, and the sowing accuracy is poor , In addition, the cost of aircraft use is high.

The second is UAV sowing: At present, relevant research and development units have been sowing UAVs (including fixed-wing UAVs and rotary-wing UAVs). UAVs are operated by operators on the ground, so they are relatively safe. However, the payload of the UAV is relatively low (generally, the payload is 10-15kg), the carrying capacity of a flight operation is small, and the area for defogging is small. Moreover, the take-off and landing of the UAV are relatively complicated and costly.

The third is ground sowing: this method requires multiple catalyst spreading points on the ground, and the catalyst is released at a height of several meters above the ground, but this method will be affected by wind direction and wind speed. Moreover, the manpower and material resources consumed by arranging multiple catalyst spreading points in the fog area are huge. Especially on the expressway, an instrument for spreading the catalyst needs to be placed not far from the roadside along the way, and the cost is very high.

Contents of the invention

The technical problem to be solved by the present invention is to fill in the gaps in the prior art, and provide a safe, reliable, easy-to-manipulate, low-cost, heavy-duty robot that can fly as long as 200 kilometers through remote control and autonomous navigation. Wing unmanned aerial vehicle, as an automatic fog-elimination flight operation platform. Specifically, the present invention provides a soft-wing unmanned aerial vehicle with an automatic defogging function.

The present invention achieves the above-mentioned object of the invention through the following technical solutions.

A soft-wing unmanned aerial vehicle with automatic defogging function is characterized in that it includes: a flexible stamping parafoil, a structural cabin, a power system, defogging equipment and a control system; the flexible stamping parafoil provides lift for the system;

The lower part of the flexible stamping parafoil is connected to the structural cabin through a parachute; the structural cabin is equipped with a control system and built-in anti-fog equipment, and a power system is installed at the tail;

The structural cabin mainly includes the cabin frame, mounting seat and skid landing gear. The mounting seat is fixed on the bottom of the cabin frame and protrudes to both sides. The lower part of the body frame is used for the take-off and landing buffer of the system;

The power system is used to provide the power required for flight, mainly including engines and propellers;

The anti-fog equipment includes built-in anti-fog equipment and external anti-fog equipment, which are used to spread anti-fog agents at the same time or separately. The built-in anti-fog equipment is installed inside the structural cabin, and the external anti-fog equipment is installed outside the structural cabin;

The built-in anti-fog equipment is composed of a throwing cabin, an insert plate, a steering gear and a discharge port. The throwing cabin is installed in the structural cabin, and the bottom is opened on the structural cabin. Hold the input port, one end of the steering gear is connected to the plug-in board, and is controlled by the control system;

The external fog-eliminating equipment is composed of a fixing frame, a dispersing cylinder and an excitation electrode. The dispersing cylinder is fixed under the mounting seat through the fixing frame. The excitation electrode and the dispersing cylinder are installed together and controlled by the control system;

The anti-fog equipment also includes detection and detection equipment. The detection and detection equipment is equipped with: weather radar, satellite receiving equipment, PMS cloud particle measurement system, meteorological instrument, GPS positioning and data transmission system, and dual-channel microwave radiometer;

The control system has navigation control, communication and monitoring functions, including navigation unit, control unit, communication unit, video monitoring unit and ground control station;

The navigation unit is used to provide flight mission routes and send manipulation instructions to the control unit, mainly including onboard computer, navigation software, positioning module and various sensors; the control unit is used to execute the manipulation instructions sent by the navigation unit, drive the manipulation actuator, change The flight attitude and route mainly include the drive mechanism and power supply module; the communication unit is used for data interaction between the flying body and the ground control station, mainly including the transmitting station and receiving antenna; the video monitoring unit is used to connect the video monitoring unit installed on the flying body The video captured by the shooting equipment is downloaded to the ground station and displayed on the monitor; the ground control station is used to complete the setting of the flight route, the input of status data, the issuance of flight instructions, the monitoring of the flight trajectory and the feedback data of the flying object The receiving process mainly includes handheld remote control equipment and monitoring equipment.

In the soft-wing unmanned aircraft with automatic fog removal function of the present invention, the fog removal equipment can also have an airborne silver iodide generator, a liquid nitrogen generator, a flame bomb generator, a dry ice spreader, salt powder, urea spreading equipment and HB-1 type anti-fogging agent spreading equipment.

The soft-wing unmanned aerial vehicle with automatic defogging function of the present invention can adopt ground launch to take off, and the ground launching device includes tractor, launching fixed base, disengagement device and protective device, is used for the soft-wing unmanned aerial vehicle with automatic defogging function Take off from the ground.

The launch fixed base is set on the tractor; the soft-wing unmanned aerial vehicle to be launched with automatic defogging function is placed on the launch fixed base, and connected with the tightening winch through the tightening belt; the protective device is set at the front end of the launching base; The disengagement device is located in the middle of the launch fixed base, below the unmanned aerial vehicle to be launched.

The soft-wing unmanned aerial vehicle with automatic fog removal function of the present invention can also be launched by the airdrop device installed on the aircraft.

The soft-wing unmanned aerial vehicle with automatic defogging function of the present invention can also be equipped with a ground remote control system, which controls the flexible stamping parafoil unmanned aerial vehicle to fly to a predetermined height, and then flies to the target coordinate point according to the predetermined route. After completing the task of spreading the anti-fog agent to automatically eliminate the fog, return to the destination airspace according to the predetermined route, and judge the altitude information and the wind direction information of the landing site, and use the bird landing method to achieve fixed-point landing.

When defogging is required, the soft-wing unmanned aerial vehicle flies to the designated area, and the defogging medium is injected from the external defogging device or from the built-in defogging device, or the defogging medium is injected from both inside and outside.

Compared with the prior art, the present invention has the following beneficial effects:

1. Safe and reliable, easy to operate, large load capacity;

2. Through remote control and autonomous navigation, the flight defogging distance can be as long as 200 kilometers;

3. Low cost, simple and easy to implement;

4. It has a wide range of applications. It can be applied to any situation that needs to eliminate fog in a local area, such as improving the road traffic environment, eliminating dense fog at airports, and improving the microclimate in disaster relief areas.

Description of drawings

Fig. 1 is the overall appearance schematic diagram of the soft-wing unmanned aerial vehicle with automatic defogging function of the present invention

Fig. 2 is the structural representation of the soft-wing unmanned aerial vehicle with automatic defogging function of the present invention

Fig. 3 is the structural diagram of the defogging equipment of the soft-wing unmanned aerial vehicle with automatic defogging function of the present invention

Fig. 4 is the control system diagram of the soft-wing unmanned aerial vehicle with automatic defogging function of the present invention

Fig. 5 is a schematic diagram of the connection between the soft-wing unmanned aerial vehicle with automatic defogging function and the ground traction launching device of the present invention

Fig. 6 is the system block diagram of the soft-wing unmanned aerial vehicle with automatic fog removal function of the present invention

Fig. 7 is a schematic diagram of the ground take-off of the soft-wing unmanned aerial vehicle with automatic fog removal function of the present invention

Fig. 8 is a schematic diagram of the airdrop launch of the soft-wing unmanned aerial vehicle with automatic fog removal function of the present invention

In the figure: 1-flexible stamping parafoil, 2-structure cabin, 3-power system, 5-control system, 6-launching fixed seat, 7-tractor, 8-parachute rope, 9-mounting seat, 10-cabin body frame, 11-skid landing gear, 12-engine, 13-propeller, 14-built-in anti-fog equipment, 15-external anti-fog equipment, 16-throwing cabin, 17-board, 18-rudder, 19-Injection port, 20-Fixed frame, 21-Scattering cylinder, 22-Excitation electrode, 23-Navigation unit, 24-Control unit, 25-Communication unit, 26-Video monitoring unit, 27-Ground control station, 28- Break away from device, 29-guard, 30-tighten belt, 31-tighten winch.

Detailed ways

The present invention is further described by the following examples.

Fig. 1 is a schematic diagram of the appearance of the soft-wing unmanned aerial vehicle with automatic defogging function of the present embodiment, and Fig. 2 is a structural schematic diagram of the soft-wing unmanned aerial vehicle with automatic defogging function of the present embodiment. Referring to Fig. 1 and Fig. 2, the soft-wing unmanned aerial vehicle with automatic defogging function of the present embodiment comprises: flexible stamping parafoil 1, structure cabin body 2, power system 3, defogging equipment and control system 5; Flexible stamping parafoil 1 provides lift to the system.

The lower part of the flexible stamping parafoil 1 is connected to the structural cabin body 2 through the parachute 8; the structural cabin body 2 is equipped with a control system 5 and a built-in defogging device 14, and a power system 3 is installed at the rear.

The structural cabin body 2 mainly includes a cabin body frame 10 , an installation seat 9 and a skid type landing gear 11 . The mounting seat 9 is fixed on the bottom of the cabin frame 10 and protrudes to both sides, on which an external defogging device 15 is respectively installed, and the skid type landing gear 11 is installed on the bottom of the cabin frame 10 for take-off and landing buffering of the system.

The power system 3 is used to provide the power required for flight, and mainly includes an engine 12 and a propeller 13 .

Fig. 3 is the structural diagram of the anti-fog equipment of the soft-wing unmanned aerial vehicle with automatic anti-fog function of the present embodiment. As can be seen from Fig. 3, the anti-fog equipment is the key component of this embodiment, and the anti-fog equipment includes a built-in anti-fog equipment 14 And external mist elimination equipment 15. It can be seen from FIG. 3 that the built-in defogging device 14 is installed inside the structural cabin body 2 , and the external defogging device 15 is installed outside the structural cabin body 2 .

The built-in demisting device 14 is made up of a throwing cabin 16, an inserting plate 17, a steering gear 18 and a delivery port 19. The throwing cabin 16 is installed in the structural cabin body 2, and the bottom is provided with a delivery opening 19 on the structural cabin body 2. The plate 17 is installed in the lower part of the throwing cabin 16 and covers the delivery port 19, and one end of the steering gear 18 is connected with the inserting plate 17, and is controlled by the control system 5.

The working process of the built-in anti-fog device 14 is as follows: the control system 5 controls the steering gear 18, and the steering gear 18 pulls the insert plate 17 to open the injection port 19, and the anti-fog agent pre-placed in the throwing cabin 16 is successfully thrown out.

The external defogging device 15 is composed of a fixing frame 20, a dispersing cylinder 21 and an excitation electrode 22. The dispersing cylinder 21 is fixed under the mounting base 9 through the fixing frame 20, and the excitation electrode 22 and the dispersing cylinder 21 are installed together to be controlled. System 5 controls.

The working process of the external defogging device 15 is as follows: the control system 5 controls the excitation electrode 22, activates the dispersing cylinder 21, and sprinkles the defogging agent previously placed in the dispersing cylinder 21 to complete the defogging.

The built-in anti-fog equipment 14 and the external anti-fog equipment 15 can spread the anti-fog agent at the same time or separately. The anti-fog equipment also includes detection and detection equipment. instrument, GPS positioning and data transmission system, dual-channel microwave radiometer.

In the soft wing unmanned aerial vehicle with automatic defogging function of the present embodiment, defogging equipment can also have airborne silver iodide generator, liquid nitrogen generator, flame bomb generator, dry ice spreader, salt powder, urea spreading equipment And HB-1 type anti-fogging agent spreading equipment.

Fig. 4 is the control system diagram of the soft-wing unmanned aerial vehicle with automatic defogging function of the present embodiment, as can be seen from Fig. 4, control system 5 has navigation control and communication, monitoring function, comprises navigation unit 23, control unit 24 , communication unit 25, video surveillance unit 26 and ground control station 27.

The navigation unit 23 is used to provide flight mission routes and send manipulation instructions to the control unit, mainly including onboard computer, navigation software, positioning module and various sensors; the control unit 24 is used to execute the manipulation instructions sent by the navigation unit, and drive the manipulation actuators , to change the flight attitude and route, mainly including the driving mechanism and the power supply module; the communication unit 25 is used for data interaction between the flying body and the ground control station, mainly including the transmitting station and the receiving antenna; the video monitoring unit 26 is used to control the flying body The video taken by the installed video surveillance equipment is downlinked to the ground station and displayed on the display; the ground control station 27 is used to complete the setting of the flight path, the input of the state data, the sending of the flight order and the monitoring and control of the flight path The receiving and processing of flying object feedback data mainly includes handheld remote control equipment and monitoring equipment.

Fig. 5 is a schematic diagram of the connection between the soft-wing unmanned aerial vehicle with the automatic defogging function of the present embodiment and the ground traction launch device. Referring to Fig. 5, the ground launch device includes a tractor 7, a launch mount 6, a breakaway device 28 and a protective device 29. It is used for the soft-wing unmanned aerial vehicle with automatic fog removal function to tow and take off from the ground.

The launch fixed base 6 is arranged on the tractor 7; the soft-wing unmanned aerial vehicle with automatic fog removal function to be launched is placed on the launch fixed base 6, and is connected with the tightening winch 31 by the tightening belt 30; the protective device 29 is set At the front end of the launch base; the disengagement device 28 is located in the middle of the launch fixed base 6 and is located below the unmanned aerial vehicle to be launched. Concrete work process has been disclosed in utility model patent ZL201220565967.0 (authorization announcement number CN202879795 U), no longer detailed description here.

Fig. 6 is a system block diagram of the soft-wing unmanned aerial vehicle with automatic fog removal function of the present invention.

Figure 7 is a schematic diagram of the ground take-off of the soft-wing unmanned aerial vehicle with automatic fog removal function. The specific take-off process has been disclosed in the utility model patent ZL201220565967.0 (authorized announcement number CN 202879795 U), and will not be described in detail here. After controlling the soft-wing unmanned aerial vehicle with automatic defogging function to rise to the predetermined height, it will fly to the target coordinate point according to the predetermined route. Destination airspace, and judge the altitude information and the wind direction information of the landing field, and use the method of sparrow landing to achieve fixed-point landing.

Fig. 8 is a schematic diagram of the air-drop launch of the soft-wing unmanned aerial vehicle with automatic fog removal function of the present invention. It goes without saying that those skilled in the art can fully refer to FIG. 8 and the contents of the description of the present invention to implement airdrop launch of the soft-wing unmanned aerial vehicle with automatic fog removal function.

The use of soft-wing unmanned aerial vehicles for defogging operations is an unprecedented method of defogging operations, because the soft-wing unmanned aerial vehicles use large-area stamped parafoils as wings, and the aerodynamic resistance generated by the parafoils is sufficient to avoid The soft-wing unmanned aerial vehicle will not damage the equipment by landing on the ground at high speed, so in a sense, the safety of the soft-wing unmanned aerial vehicle is much higher than that of drones or even some manned aircraft.

The relevant parameters adopted in this embodiment are as follows:

Payload: ≥200kg;

Fuel weight: ≥60kg;

Take-off weight: ≤500kg;

Battery life: ≥6h;

Cruising speed: ≤50km/h;

Maximum flight altitude: 5000m;

Control mode: manual remote control and autonomous navigation, the autonomous navigation control mode has an external interface, and the coordinates of the target point can be temporarily input before use;

Manual remote control distance: 10km (plus extended range);

Take-off mode: launch vehicle tow and take off;

Take-off distance: ≤150m;

Landing gear: skid type landing gear;

Landing method: manual remote control and autonomous landing;

Equipped with the carrying interface and control start interface of the anti-fog equipment;

The antifogging agent used in this embodiment: the antifogging agent is divided into two types: spraying type antifogging agent and increasing type antifogging agent. Spray-type anti-fog agents include inorganic spray-type anti-fog agents, polymer spray-type anti-fog agents and composite spray-type anti-fog agents. Inorganic spray anti-fogging agent is a compound prepared in a certain proportion from silica gel emulsion of SiO2 hydrate, A1203 hydrate emulsion, non-ionic or anionic surfactant, cross-linking agent, catalyst and defoamer. Polymer spray anti-fogging agent is mainly composed of polyether sulfonate and polymethacrylic acid glycol glucose with a small amount of additives and solvents. Composite spray anti-fog agent is mainly composed of glycoside nonionic surfactant and general cationic surfactant. Increased anti-fog agents can be divided into fluorine-containing, silicon-containing, phosphorus-containing and boron-containing anti-fog agents. The fluorine-increased anti-fog agent refers to a surfactant in which the hydrogen atoms on the lipophilic group of the hydrocarbon chain are completely replaced by fluorine. Among the increasing anti-fogging agents, fluorine-containing anti-fogging agents have the best effect. Because the C—F bond in the fluorine-increased anti-fog agent has good heat resistance, chemical stability and duality of water and oil repellency, the C—F bond forms an oriented arrangement layer on its surface to reduce the surface tension of water , can make water droplets fall faster, and reduce the volatilization of the surface, so that the vapor pressure in the air drops below the saturated vapor pressure. Silicon-added anti-fogging agent is a kind of active agent composed of siloxane as lipophilic group and hydrophilic group. It has excellent thermal stability and chemical stability, and its ability to reduce surface tension is second only to fluorine-increased anti-fog agents and greater than hydrocarbon-based anti-fog agents.

This embodiment can eliminate or dilute the warm fog in the runway area within 30 minutes through multiple sorties of reciprocating operations, improve visibility and maintain it for a period of time.

Claims (5)

1. a soft-wing unmanned aerial vehicle with automatic fog removal function, is characterized in that, comprises: flexible stamping parafoil (1), structure cabin body (2), power system (3), fog removal equipment and control system ( 5); the flexible stamping parafoil (1) provides lift to the system; The lower part of the flexible stamping parafoil (1) is connected to the structural cabin (2) through a parachute (8); the structural cabin (2) is equipped with a control system (5) and a built-in anti-fog device (14), and a power system is installed at the rear (3); The structural cabin (2) mainly includes a cabin frame (10), a mounting seat (9) and a skid type landing gear (11), and the mounting seat (9) is fixed on the bottom of the cabin frame (10) and protrudes to both sides. External defogging equipment (15) is respectively installed on it, and the skid type landing gear (11) is installed on the lower part of the cabin frame (10), which is used for take-off and landing buffer of the system; The power system (3) is used to provide the power required for flight, mainly including an engine (12) and a propeller (13); The anti-fog equipment includes a built-in anti-fog equipment (14) and an external anti-fog equipment (15), which are used to spread anti-fog agents simultaneously or separately. The built-in anti-fog equipment (14) is installed inside the structural cabin (2), and the external The mist elimination equipment (15) is installed outside the structural cabin body (2); The built-in fog-eliminating equipment (14) is composed of a throwing cabin (16), an insert plate (17), a steering gear (18) and a discharge port (19), and the throwing cabin (16) is installed in the structural cabin (2), Bottom has drop-in opening (19) on structure cabin body (2), and flashboard (17) is installed in throwing away cabin (16) bottom and covers drop-in port (19), steering gear (18) one end and flashboard ( 17) are connected and controlled by the control system (5); The external defogging device (15) is composed of a fixing frame (20), a dispersing cylinder (21) and an excitation electrode (22), and the dispersing cylinder (21) is fixed under the mounting base (9) through the fixing frame (20). The excitation electrode (22) is installed together with the dispersing cylinder (21) and is controlled by the control system (5); The anti-fog equipment also includes detection and detection equipment. The detection and detection equipment is equipped with: weather radar, satellite receiving equipment, PMS cloud particle measurement system, meteorological instrument, GPS positioning and data transmission system, and dual-channel microwave radiometer; The control system (5) has navigation control and communication and monitoring functions, including a navigation unit (23), a control unit (24), a communication unit (25), a video monitoring unit (26) and a ground control station (27); The navigation unit (23) is used to provide flight mission routes and send manipulation instructions to the control unit, mainly including on-board computer, navigation software, positioning module and various sensors; the control unit (24) is used to execute the manipulation instructions sent by the navigation unit, Drive and manipulate the actuator to change the flight attitude and route, mainly including the driving mechanism and the power supply module; the communication unit (25) is used for data interaction between the flying body and the ground control station, mainly including the transmitting station and the receiving antenna; the video monitoring unit ( 26) It is used to download the video taken by the video monitoring equipment installed on the flying body to the ground station and display it on the display; the ground control station (27) is used to complete the setting of the flight route, the input of status data, The issuing of flight instructions, the monitoring of flight trajectory and the receiving and processing of flying object feedback data mainly include handheld remote control equipment and monitoring equipment. 2. the soft-wing unmanned aerial vehicle with automatic defog function according to claim 1, is characterized in that, defog equipment also has airborne silver iodide generator, liquid nitrogen generator, flame bomb generator, dry ice spreader, Salt powder, urea spreading equipment and HB-1 anti-fogging agent spreading equipment. 3. The soft-wing unmanned aerial vehicle with automatic fog removal function according to claim 1, characterized in that, the ground launching device comprises a tractor (7), launching a fixed base (6), a breakaway device (28) and a protective device (29), used for the soft-wing unmanned aerial vehicle with automatic fog removal function towing and taking off from the ground; The launch fixed base (6) is arranged on the tractor (7); the soft-wing unmanned aerial vehicle with automatic defogging function to be launched is placed on the launch fixed base (6), and tightened with the tightening belt (30) The winch (31) is connected; the protective device (29) is located at the front end of the launch base; the breakaway device (28) is located at the middle of the launch fixed base (6), and is positioned below the unmanned aerial vehicle to be launched. 4. The soft-wing unmanned aerial vehicle with automatic fog removal function according to claim 1, characterized in that, the unmanned aerial vehicle is launched by an airdrop device installed on the aircraft. 5. The soft-wing unmanned aerial vehicle with automatic defogging function according to any one of claims 1 to 4, characterized in that, a ground remote control system is provided to control the flexible ram parafoil unmanned aerial vehicle to fly to a predetermined height After that, fly to the target coordinate point according to the scheduled route, and after completing the task of spreading the anti-fog agent to automatically eliminate the fog at the task target point, return to the destination airspace according to the scheduled route, and judge the altitude information and the wind direction information of the landing field, and use the method of sparrow landing way to achieve fixed-point landing.