CN103149938A - Emergency landing method of unmanned aerial vehicle based on radio and laser guiding - Google Patents
Emergency landing method of unmanned aerial vehicle based on radio and laser guiding Download PDFInfo
- Publication number
- CN103149938A CN103149938A CN2013101195017A CN201310119501A CN103149938A CN 103149938 A CN103149938 A CN 103149938A CN 2013101195017 A CN2013101195017 A CN 2013101195017A CN 201310119501 A CN201310119501 A CN 201310119501A CN 103149938 A CN103149938 A CN 103149938A
- Authority
- CN
- China
- Prior art keywords
- unmanned plane
- laser
- runway
- radio
- control system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Abstract
The invention relates to an emergency landing method of an unmanned aerial vehicle based on radio and laser guiding. Equipment in the method comprises a laser scanner, laser receivers and a data processor; the laser scanner is arranged at the end of one end of a runway, a scanning center aligns to the center line of the runway, and a flake laser beam is emitted out in a scanning range of plus-minus five degrees to plus-minus ten degrees; two laser receivers are arranged at both ends of the wings of the unmanned aerial vehicle, and are connected with the data processor through cables; and the data processor is arranged inside an equipment compartment of the unmanned aerial vehicle. When a flight control system of the unmanned aerial vehicle judges that received GPS (Global Positioning System) data is in failure, the emergency landing of the unmanned aerial vehicle is realized through the combination of long-distance radio guiding and short-distance laser guiding.
Description
Technical field
The present invention relates to a kind of unmanned plane get off the plane in GPS device fails or the disturbed and loss situation of gps signal can safety, the method for precision landing, the security when increasing the unmanned plane landing improves the airport security guarantee condition.
Background technology
Must be with specific course heading with highly near accurately landing of runway during the unmanned plane landing, in this process, traditional landing mission is that unmanned plane carries out flight path control by the given positional information of GPS, elevation information, velocity reversal information.But in a single day Airborne GPS equipment break down or gps signal is disturbed and loss, can cause whole guidance system to quit work, and can have influence on the safe falling of unmanned plane, and in serious situation, unmanned plane even can be lost crash.At present, in the safe retrieving of sliding race landing unmanned plane, seldom there is unmanned plane to possess emergent Landing Guidance System, when GPS breaks down with problem, the unmanned plane operator can only be opened the remote manual control aircraft landing or guide to make unmanned plane landing by the relatively poor radio of precision, and this causes the probability that unmanned plane can safe falling greatly to reduce.Therefore, the effect along with UAV Landing guiding in modern unmanned plane is more and more important, be necessary to design a kind of unmanned plane without the GPS situation under the method for emergency landing guiding, thereby guarantee the precision landing of unmanned plane, the security when increasing the unmanned plane landing.
Summary of the invention
Technology of the present invention is dealt with problems and is: overcome the deficiencies in the prior art, a kind of unmanned plane emergency landing method based on radio and laser aiming is provided, can realize that the precise and safety of unmanned plane is landed in without the GPS situation.
Technical solution of the present invention is: a kind of unmanned plane emergency landing method based on radio and laser aiming, and the equipment that method is relied on comprises laser scanner, laser pickoff and data processor; Laser scanner is arranged on the end of runway one end, scanning center's line up with runway center line, send the sheet laser beam with positive and negative 5 degree to the sweep limit of positive and negative 10 degree, two laser pickoffs are arranged on two ends of unmanned plane wing, be connected with data processor by cable, data processor is arranged in the equipment compartment of unmanned plane; When the flight control system of unmanned plane judged that the gps data that receives breaks down, the emergency landing method step was as follows:
(1) mask gps data, change the radio bootmode over to, ground control station is sent to unmanned plane the flight control system of unmanned plane to the GPS latitude and longitude information of distance, position angle, the angle of pitch and the ground control station of ground control station by radio;
(2) flight control system of unmanned plane is according to the GPS latitude and longitude information of the unmanned plane that receives to distance, position angle, the angle of pitch and the ground control station of ground control station, extrapolate roughly the latitude and longitude information of unmanned plane, UAV Flight Control System is carried out independent navigation according to the latitude and longitude information of extrapolating, until fly into the window of marching into the arena;
(3) unmanned plane is according to the radio guiding of ground control station, and Ding Gaoping flies along the runway center line marking direction;
(4) enter the laser aiming window, be unmanned plane during flying to the position apart from 8 to 10 kilometers of runway proximal heads, judge whether laser pickoff receives the laser intelligence that laser scanner sends, if do not receive, turn step (5), otherwise turn step (6);
(5) unmanned plane is kept former state of flight, continue to judge whether laser pickoff receives the laser intelligence that laser scanner sends in this process, meanwhile flight control system judge unmanned plane apart from the distance of runway proximal head whether lower than 5 kilometers, if lower than 5 kilometers, control unmanned plane and go around and give an encore, restart from step (4);
(6) data processor is determined direction that unmanned plane is current and the distance between unmanned plane and laser scanner according to the laser intelligence that receives, UAV Flight Control System direction current according to unmanned plane adjusted unmanned plane with the direction flight over against the runway center, and controls unmanned plane safe landing on runway according to the distance between unmanned plane and laser scanner.
The present invention compared with prior art beneficial effect is:
(1) for overcome that in a single day Airborne GPS equipment break down or gps signal is disturbed and loss situation under cause whole unmanned plane guidance system to quit work and deficiency that can't safe landing, the present invention has designed a kind of emergency landing method that is applied to unmanned plane, by landing mission being divided into long-range vectoring and closely guiding two parts, carry out remote coarse adjustment by radio respectively, replace the resulting relevant information of GPS receiver by laser aiming and carry out accurate adjustment, guarantee the safe falling of unmanned plane.
(2) the present invention is in the safe landing process, adopt the tradition window of marching into the arena reliably, by the safe minimum that lands is set, when receiving laser intelligence before not entering safe minimum, can guarantee that unmanned plane has time enough and distance to carry out safe landing, otherwise, the security that further improves UAV Landing by the mode of again giving an encore.
Description of drawings
Fig. 1 is remote-wireless electricity bootup process schematic diagram of the present invention;
Fig. 2 is closely laser aiming process of the present invention schematic diagram;
Fig. 3 is that unmanned plane of the present invention is marched into the arena, the emergent schematic diagram that guides and go around;
Fig. 4 is laser scanning of the present invention, guiding schematic diagram;
Fig. 5 is the process flow diagram of emergency landing method of the present invention.
Embodiment
Below in conjunction with accompanying drawing, the present invention is elaborated, for a better understanding of the present invention, at first the below makes an explanation to the equipment that the present invention relies on.
The equipment that the present invention relies on comprises laser scanner, laser pickoff and data processor;
Laser scanner is arranged on the end of runway one end, and scanning center's line up with runway center line sends the sheet laser beam with positive and negative 5 degree to the sweep limit of positive and negative 10 degree, and sweep frequency is certain.
Two laser pickoffs are arranged on two ends of unmanned plane wing, are connected with data processor by cable, and data processor is arranged in the equipment compartment of unmanned plane, is connected with flight control computer by serial ports.
As shown in Figure 5, unmanned plane is when executing the task, the position data that the ground control station computing machine is sent ground control station GPS receiver here and the actual location data of tracking telemetry and command station constantly compare, and obtain the position correction amount, and launch by the wireless station of ground control station.The position correction amount that the aircraft position data that airborne computer is sent the GPS receiver here and radio receiver are sent here is carried out data and is processed, obtain position data more accurately, again these data and prebriefed pattern are compared the error signal that obtains actual flight path point standoff, and it is delivered to flight control system, aircraft is got back on the prearranged heading, the autonomous GPS navigation when completing aerial mission; When aircraft need to land, the position data of GPS more accurately that airborne computer obtains is determined current flight path, and compare with predetermined glide path, must deviate, and departure is delivered to flight control system, flight control system is controlled the flight position of unmanned plane, makes it follow the tracks of the landing glide path, according to the course line safe falling of planning in advance.
When the Airborne GPS device fails, perhaps gps signal is interfered and when losing, will cause the normal workflow of above-mentioned unmanned plane to carry out smoothly, the aerial mission of aircraft and landing process all can be affected, flight control system more can't be accurately with the unmanned plane talk down owing to can not get effective gps data and then can't control accurately aircraft track.
The technical scheme that the present invention designs in order to address the above problem just mainly comprises remote-wireless electricity guiding and laser aiming two parts closely.
One, remote-wireless electricity guiding
The long haul radio vectoring phase, march into the arena window till the laser aiming window by ground control station with radio vector aircraft arrival after breaking down from Airborne GPS.In Fig. 1, the main composition of long haul radio guiding is ground control station.It is the ground control station that unmanned plane carries, because needs provide relatively accurate radiogoniometry, so need to tracking telemetry and command station is parallel or be fixed perpendicular to runway accurately, and with carry out initial calibration through the runway course of demarcating, make the GPS information of ground control station satisfy accuracy requirement.
Concrete steps are as follows:
(1) mask gps data, change the radio bootmode over to, ground control station is sent to unmanned plane the flight control system of unmanned plane to the GPS latitude and longitude information of distance, position angle, the angle of pitch and the ground control station of ground control station by radio;
(2) flight control system of unmanned plane is according to the GPS latitude and longitude information of the unmanned plane that receives to distance, position angle, the angle of pitch and the ground control station of ground control station, as shown in Figure 1, extrapolate roughly the latitude and longitude information of unmanned plane, UAV Flight Control System is carried out independent navigation according to the latitude and longitude information of extrapolating, until fly into the window of marching into the arena;
As shown in Figure 3, the window definition of marching into the arena is apart from airfield runway proximal head 13-15 kilometer, the scope of height 500-800 rice.
Unmanned plane is completed data communication by radio and ground control station, and ground control station possesses radio signal search, tracking and positioning function, can make unmanned plane all the time along the flight of radio indication track; The tracking telemetry and command station antenna has the diaxon servo-drive system, measure the level of antenna and position angle and the angle of pitch that luffing angle changes and then obtain unmanned plane by the direction sensor of servo-drive system, provide the deviation of the current flight path of unmanned plane and preset flight path, just can provide the position of unmanned plane with respect to ground control station by the radio signal distance measuring equipment simultaneously, more just can complete coarse localization to unmanned plane according to the ground control station GPS positional information that gathers in advance of ground control station.At last, through wireless digital broadcasting station, these information are sent to flight control system, unmanned aerial vehicle flight path is revised, form closed-loop control system and control aircraft.Unmanned plane just can be completed without the independent navigation in the GPS situation by calculating positional information and the elevation information that provides of oneself height sensor out, flies to the appointed area.
Certainly, this process also can be carried out manual guidance by the unmanned plane latitude and longitude information that manually transfers to ground control station according to unmanned plane, formulates the zone until fly to.
(3) unmanned plane is according to the radio guiding of ground control station, and Ding Gaoping flies along runway heading;
In remote-wireless electricity bootup process, unmanned plane need to fly with level altitude, and voyage is 5～7km approximately, and in this process, before aircraft arrived the laser aiming window, aircraft will fly in the sector region of laser scanning light beam.Just need to open at remote-wireless electricity vectoring phase Laser Scanning Equipment the line scanning of going forward side by side.
Two, closely laser aiming
Closely laser aiming is from the laser aiming window to landing period.The equipment that closely needs in laser aiming to utilize comprises the magnetic heading that carries on unmanned plane.The runway course that basis has been demarcated on runway is in advance revised the deviation of magnetic heading, is used as unmanned plane during flying and emergency landing course control and sliding the race and controls.
Concrete steps are as follows:
(4) enter the laser aiming window, be unmanned plane during flying to the position apart from 8 to 10 kilometers of runway proximal heads, judge whether laser pickoff receives the laser intelligence that laser scanner sends, if do not receive, turn step (5), otherwise turn step (6);
(5) unmanned plane is kept former state of flight (direction and height), and judge unmanned plane apart from the distance of runway proximal head whether lower than 5 kilometers, if lower than 5 kilometers, control unmanned plane and go around and give an encore, restart from step (4);
(6) data processor is determined direction that unmanned plane is current and the distance between unmanned plane and laser scanner according to the laser intelligence that receives, UAV Flight Control System direction current according to unmanned plane adjusted unmanned plane with the direction flight over against the runway center, and controls unmanned plane safe landing on runway according to the distance between unmanned plane and laser scanner.
Here laser scanner is with the outside emission pulse laser bundle of a certain fixed frequency, and the paired pulses laser beam has been carried out coding work, the laser pulse information that is different scanning angles places is different, can determine thus the entrained azimuth information of laser beam that laser pickoff receives.β in Fig. 4
1And β
2Be exactly two laser pickoffs (A1, A2) and laser scanner line and runway center line marking angulation, suppose unmanned plane and and vertical runway center line vertical line L angulation this moment
Flight,
The angle can be provided by the magnetic heading on aircraft, so just can obtain the θ shown in figure according to geometric relationship
1And θ
2The angle, the mounting distance D of two laser pickoffs is known quantities, just can obtain the R shown in figure by triangle relation again, also just can calculate generating laser to unmanned plane apart from S, here the elevation information of unmanned plane is provided by radio altimeter, can calculate the elevation angle of unmanned plane according to Pythagorean theorem.The side drift angle of unmanned plane is by β
1And β
2Determine
Elevation angle is obtained by S and radio altimeter, can determine thus the directional information (elevation angle of unmanned plane, side drift angle) and positional information (apart from S, the longitude and latitude of unmanned plane etc.), wherein the side drift angle of gained is the required important references information of unmanned plane emergency landing.UAV Flight Control System side drift angle current according to unmanned plane adjusted unmanned plane with the direction flight over against the runway center, current elevation angle and predefined elevation angle (4 degree are general) are compared, adjust the flying height of unmanned plane, control difference in height, make it follow the tracks of predefined landing underscore, and control unmanned plane safe landing on runway according to the distance between unmanned plane and laser scanner.
The unspecified part of the present invention belongs to general knowledge as well known to those skilled in the art.
Claims (1)
1. unmanned plane emergency landing method based on radio and laser aiming is characterized in that: the equipment that method is relied on comprises laser scanner, laser pickoff and data processor; Laser scanner is arranged on the end of runway one end, scanning center's line up with runway center line, send the sheet laser beam with positive and negative 5 degree to the sweep limit of positive and negative 10 degree, two laser pickoffs are arranged on two ends of unmanned plane wing, be connected with data processor by cable, data processor is arranged in the equipment compartment of unmanned plane; When the flight control system of unmanned plane judged that the gps data that receives breaks down, the emergency landing method step was as follows:
(1) mask gps data, change the radio bootmode over to, ground control station is sent to unmanned plane the flight control system of unmanned plane to the GPS latitude and longitude information of distance, position angle, the angle of pitch and the ground control station of ground control station by radio;
(2) flight control system of unmanned plane is according to the GPS latitude and longitude information of the unmanned plane that receives to distance, position angle, the angle of pitch and the ground control station of ground control station, extrapolate roughly the latitude and longitude information of unmanned plane, UAV Flight Control System is carried out independent navigation according to the latitude and longitude information of extrapolating, until fly into the window of marching into the arena:
(3) unmanned plane is according to the radio guiding of ground control station, and Ding Gaoping flies along the runway center line marking direction;
(4) enter the laser aiming window, be unmanned plane during flying to the position apart from 8 to 10 kilometers of runway proximal heads, judge whether laser pickoff receives the laser intelligence that laser scanner sends, if do not receive, turn step (5), otherwise turn step (6);
(5) unmanned plane is kept former state of flight, continue to judge whether laser pickoff receives the laser intelligence that laser scanner sends in this process, meanwhile flight control system judge unmanned plane apart from the distance of runway proximal head whether lower than 5 kilometers, if lower than 5 kilometers, control unmanned plane and go around and give an encore, restart from step (4);
(6) data processor is determined direction that unmanned plane is current and the distance between unmanned plane and laser scanner according to the laser intelligence that receives, UAV Flight Control System direction current according to unmanned plane adjusted unmanned plane with the direction flight over against the runway center, and controls unmanned plane safe landing on runway according to the distance between unmanned plane and laser scanner.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2013101195017A CN103149938A (en) | 2013-04-08 | 2013-04-08 | Emergency landing method of unmanned aerial vehicle based on radio and laser guiding |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2013101195017A CN103149938A (en) | 2013-04-08 | 2013-04-08 | Emergency landing method of unmanned aerial vehicle based on radio and laser guiding |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN103149938A true CN103149938A (en) | 2013-06-12 |
Family
ID=48548079
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2013101195017A Pending CN103149938A (en) | 2013-04-08 | 2013-04-08 | Emergency landing method of unmanned aerial vehicle based on radio and laser guiding |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN103149938A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104807464A (en) * | 2015-04-22 | 2015-07-29 | 深圳市视晶无线技术有限公司 | Near field guiding method of aircraft |
| CN105445757A (en) * | 2015-12-02 | 2016-03-30 | 四川九洲电器集团有限责任公司 | Vehicle guiding system and guiding method |
| CN106873615A (en) * | 2015-12-11 | 2017-06-20 | 中国航空工业第六八研究所 | Emergent landing speed instruction set design method of giving an encore |
| CN107885223A (en) * | 2017-10-31 | 2018-04-06 | 武汉大学 | Unmanned plane recovery guiding system based on laser |
| CN107924196A (en) * | 2015-07-16 | 2018-04-17 | 赛峰电子与防务公司 | The method landed for automatic auxiliary aviation device |
| CN109032169A (en) * | 2018-06-15 | 2018-12-18 | 岭南师范学院 | A kind of unmanned plane landing-gear based on laser conduction |
| WO2019113877A1 (en) * | 2017-12-13 | 2019-06-20 | 江西洪都航空工业集团有限责任公司 | Unmanned vehicle control method and unmanned lawn mowing vehicle |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101811578A (en) * | 2010-04-23 | 2010-08-25 | 福建省电力有限公司福州电业局 | Special photoelectric nacelle of power patrol unmanned helicopter |
| CN102694351A (en) * | 2012-06-06 | 2012-09-26 | 长春理工大学 | High voltage overhead transmission line line-inspection unmanned aerial vehicle photoelectric detection device |
| WO2012140191A1 (en) * | 2011-04-14 | 2012-10-18 | Hexagon Technology Center Gmbh | System and method for controlling an unmanned air vehicle |
| CN102749927A (en) * | 2012-07-20 | 2012-10-24 | 常州大学 | System for pilotless plane to automatically avoid barrier and avoiding method of system |
| CN103092211A (en) * | 2013-01-05 | 2013-05-08 | 中国航天空气动力技术研究院 | Unmanned aerial vehicle emergent land method based on guidance of radio and laser |
-
2013
- 2013-04-08 CN CN2013101195017A patent/CN103149938A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101811578A (en) * | 2010-04-23 | 2010-08-25 | 福建省电力有限公司福州电业局 | Special photoelectric nacelle of power patrol unmanned helicopter |
| WO2012140191A1 (en) * | 2011-04-14 | 2012-10-18 | Hexagon Technology Center Gmbh | System and method for controlling an unmanned air vehicle |
| CN102694351A (en) * | 2012-06-06 | 2012-09-26 | 长春理工大学 | High voltage overhead transmission line line-inspection unmanned aerial vehicle photoelectric detection device |
| CN102749927A (en) * | 2012-07-20 | 2012-10-24 | 常州大学 | System for pilotless plane to automatically avoid barrier and avoiding method of system |
| CN103092211A (en) * | 2013-01-05 | 2013-05-08 | 中国航天空气动力技术研究院 | Unmanned aerial vehicle emergent land method based on guidance of radio and laser |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104807464A (en) * | 2015-04-22 | 2015-07-29 | 深圳市视晶无线技术有限公司 | Near field guiding method of aircraft |
| CN104807464B (en) * | 2015-04-22 | 2017-12-01 | 深圳市视晶无线技术有限公司 | Aircraft near field bootstrap technique |
| CN107924196A (en) * | 2015-07-16 | 2018-04-17 | 赛峰电子与防务公司 | The method landed for automatic auxiliary aviation device |
| CN107924196B (en) * | 2015-07-16 | 2021-03-09 | 赛峰电子与防务公司 | Method for automatically assisting an aircraft landing |
| CN105445757B (en) * | 2015-12-02 | 2018-07-06 | 四川九洲电器集团有限责任公司 | A kind of vehicles guiding system and bootstrap technique |
| CN105445757A (en) * | 2015-12-02 | 2016-03-30 | 四川九洲电器集团有限责任公司 | Vehicle guiding system and guiding method |
| CN106873615A (en) * | 2015-12-11 | 2017-06-20 | 中国航空工业第六八研究所 | Emergent landing speed instruction set design method of giving an encore |
| CN106873615B (en) * | 2015-12-11 | 2020-04-07 | 中国航空工业第六一八研究所 | Emergency return landing speed instruction set design method |
| CN107885223A (en) * | 2017-10-31 | 2018-04-06 | 武汉大学 | Unmanned plane recovery guiding system based on laser |
| CN107885223B (en) * | 2017-10-31 | 2020-02-14 | 武汉大学 | Unmanned aerial vehicle retrieves bootstrap system based on laser |
| WO2019113877A1 (en) * | 2017-12-13 | 2019-06-20 | 江西洪都航空工业集团有限责任公司 | Unmanned vehicle control method and unmanned lawn mowing vehicle |
| CN109032169A (en) * | 2018-06-15 | 2018-12-18 | 岭南师范学院 | A kind of unmanned plane landing-gear based on laser conduction |
| CN109032169B (en) * | 2018-06-15 | 2024-03-26 | 岭南师范学院 | Unmanned aerial vehicle landing device based on laser conduction |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103092211B (en) | Unmanned aerial vehicle emergent land method based on guidance of radio and laser | |
| CN103149938A (en) | Emergency landing method of unmanned aerial vehicle based on radio and laser guiding | |
| US7412324B1 (en) | Flight management system with precision merging | |
| KR101494654B1 (en) | Method and Apparatus for Guiding Unmanned Aerial Vehicle and Method and Apparatus for Controlling Unmanned Aerial Vehicle | |
| ES2817699T3 (en) | Automatic aircraft landing assistance procedure | |
| US9233761B2 (en) | Display apparatus, control support system, and display method | |
| US9830828B2 (en) | Systems and method for AIS transponder integration with ILS/VOR receivers | |
| US7917254B2 (en) | Aircraft guidance using localizer capture criteria for rectilinear displacement data | |
| CN108255190B (en) | Accurate landing method based on multiple sensors and tethered unmanned aerial vehicle using same | |
| RU2562890C2 (en) | Method of control over drone | |
| US10410529B2 (en) | Automatic assistance method for landing an aircraft | |
| CN105242285A (en) | Method based on satellite communication for identifying deception jamming acting on navigation data of unmanned plane | |
| CN106409016B (en) | Method and system for assisting guidance of an aircraft along a runway approach axis | |
| CA2795775C (en) | Method of guidance for aircraft trajectory correction | |
| EP3709116B1 (en) | Guidance deviation derivation from high assurance hybrid position solution system and method | |
| CN107168355A (en) | Unmanned vehicle course line determines method and apparatus | |
| CN113110529B (en) | Unmanned aerial vehicle long-distance composite autonomous navigation landing system and method in complex environment | |
| US20110022250A1 (en) | Helicopter autopilot | |
| RU2559196C1 (en) | Aircraft landing approach and system to this end | |
| US9612312B2 (en) | Flight guidance system | |
| CN205427178U (en) | A positioning system for accurate navigation of unmanned aerial vehicle | |
| US20080300740A1 (en) | GPS autopilot system | |
| KR20160089132A (en) | The moving vehicle docking system and method for drone pilotless aircraft | |
| US3456255A (en) | Aircraft inertial drift correction by a ground station | |
| US2323337A (en) | Radio navigation system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C02 | Deemed withdrawal of patent application after publication (patent law 2001) | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20130612 |