Unmanned Aerial Vehicle Wikipedia



Unmanned aerial vehicle


An unmanned aerial vehicle (UAV), commonly known as a drone, as an unmanned aircraft system (UAS), or by several other names, is an aircraft without a human pilot aboard. The flight of UAVs may operate with various degrees of autonomy: either under remote control by a human operator, or fully or intermittently autonomously, by onboard computers.
 
UAVs are often preferred for missions that are too "dull, dirty or dangerous" for humans. They originated mostly in military applications, although their use is expanding in commercial, scientific, recreational and other applications,[3] such as policing and surveillance, aerial photography, agriculture and drone racing.

 

Terminology


Multiple terms are used for unmanned aerial vehicles, which generally refer to the same concept.
 
The term drone, more widely used by the public, was coined in reference to the resemblance of dumb-looking navigation and loud-and-regular motor sounds of old military unmanned aircraft to the male bee. The term has encountered strong opposition from aviation professionals and government regulators.
 
The term unmanned aircraft system (UAS) was adopted by the United States Department of Defense (DoD) and the United States Federal Aviation Administration in 2005 according to their Unmanned Aircraft System Roadmap 2005–2030. The International Civil Aviation Organization (ICAO) and the British Civil Aviation Authority adopted this term, while the European Union's Single-European-Sky (SES) Air-Traffic-Management (ATM) Research (SESAR Joint Undertaking) roadmap for 2020 also uses it. This term emphasizes the importance of elements other than the aircraft. It includes elements such as ground control stations, data links and other support equipment. A similar term is an unmanned-aircraft vehicle system (UAVS) remotely piloted aerial vehicle (RPAV), remotely piloted aircraft system (RPAS). Many similar terms are in use.
 
A UAV is defined as a "powered, aerial vehicle that does not carry a human operator, uses aerodynamic forces to provide vehicle lift, can fly autonomously or be piloted remotely, can be expendable or recoverable, and can carry a lethal or nonlethal payload". Therefore, missiles are not considered UAVs because the vehicle itself is a weapon that is not reused, though it is also unmanned and in some cases remotely guided.
 
The relation of UAVs to remote controlled model aircraft is unclear.[citation needed] UAVs may or may not include model aircraft.[citation needed] Some jurisdictions base their definition on size or weight, however, the US Federal Aviation Administration defines any unmanned flying craft as a UAV regardless of size. A radio-controlled aircraft becomes a drone with the addition of an autopilot AI, and ceases to be a drone when the AI is removed.

UAV components

 
Manned and unmanned aircraft of the same type generally have recognizably similar physical components. The main exceptions are the cockpit and environmental control system or life support systems. Some UAVs carry payloads (such as a camera) that weigh considerably less than an adult human, and as a result can be considerably smaller. Though they carry heavy payloads, weaponized military drones are lighter than their manned counterparts with comparable armaments.
 
Small civilian UAVs have no life-critical systems, and can thus be built out of lighter but less sturdy materials and shapes, and can use less robustly tested electronic control systems. For small UAVs, the quadcopter design has become popular, though this layout is rarely used for manned aircraft. Miniaturization means that less-powerful propulsion technologies can be used that are not feasible for manned aircraft, such as small electric motors and batteries.
 
Control systems for UAVs are often different than manned craft. For remote human control, a camera and video link almost always replace the cockpit windows; radio-transmitted digital commands replace physical cockpit controls. Autopilot software is used on both manned and unmanned aircrft, with varying feature sets.
 
Body
The primary difference for planes is the absence of the cockpit area and its windows. Tailless Quadcopters are a common form factor for rotary wing UAVs while tailed mono- and bi-copters are common for manned platforms.
 
Power supply and platform
Small UAVs rely mostly use lithium-polymer batteries (Li-Po), while larger vehicles rely on conventional airplane engines.
 
Battery elimination circuitry (BEC) is used to centralize power distribution and often harbors a microcontroller unit (MCU). Costlier switching BECs diminish heating on the platform.
 
Computing
UAV computing capability followed the advances of computing technology, beginning with analog controls and evolving into microcontrollers, then system-on-a-chip (SOC) and single-board computers (SBC).
 
System hardware for small UAVs is often called the Flight Controller (FC), Flight Controller Board (FCB) or Autopilot.
 
Sensors
Proprioceptive sensors give information about the aircraft state. Exteroceptive sensors deal with external information like distance measurements, while exproprioceptive ones correlate internal and external states.
 
Non-cooperative sensors are able to detect targets autonomously so they are used for separation assurance and collision avoidance.
 
Degrees of freedom (DOF) refer to both the amount and quality of sensors on-board: 6 DOF implies 3-axis gyroscopes and accelerometers (a typical inertial measurement unit – IMU), 9 DOF refers to an IMU plus a compass, 10 DOF adds a barometer and 11 DOF usually adds a GPS receiver.
 
Actuators
UAV actuators include digital electronic speed controllers (which control the RPM of the motors) linked to motors/engines and propellers, servomotors (for planes and helicopters mostly), weapons, payload actuators, LEDs and speakers.
 
Software
UAV software called the flight stack or autopilot. UAVs are real-time systems that require rapid rsponse to changing sensor data. Examples include RaspberryPis, Beagleboards, etc. shielded with NavIO, PXFMini, etc. or designed from scratch such as Nuttx, preemptive-RT Linux, Xenomai, Orocos-Robot Operating System or DDS-ROS 2.0.
 
Loop principles
 
Typical flight-control loops for a multirotor
UAVs employ open-loop, closed-loop or hybrid control architectures. Open loop—This type provides a positive control signal (faster, slower, left, right, up, down) without incorporating feedback from sensor data.
 
Closed loops – This type incorporates sensor feedback to adjust behavior (reduce speed to reflect tailwind, move to altitude 300 feet). The PID controller is common. Sometimes, feedforward is employed, transferring the need to close the loop further.

Flight controls
Flight control is one of the lower-layer system and is similar to manned aviation: plane flight dynamics, control and automation, helicopter flight dynamics and controls and multirotor flight dynamics were researched long before the rise of UAVs.
 
Automatic flight involves multiple levels of priority.
 
UAVs can be programmed to perform aggressive man?uvres or landing/perching on inclined surfaces, and then to climb toward better communication spots. Some UAVs can control flight with varying flight modelisation, such as VTOL designs.
 
Communications
Most UAVs use a radio frequency front-end that connects the antenna to the analog-to-digital converter and a flight computer that controls avionics (and that may be capable of autonomous or semi-autonomous operation).
 
Radio allows remote control and exchange of video and other data. Early UAVs[when?] had only uplink. Downlinks (e.g., realtime video) came later.[citation needed]
 
In military systems and high-end domestic applications, downlink may convey payload management status. In civilian applications, most transmissions are commands from operator to vehicle. Downstream is mainly video. Telemetry is another kind of downstream link, transmitting status about the aircraft systems to the remote operator. UAVs use also satellite "uplink" to access satellite navigation systems.
 
The radio signal from the operator side can be issued from either:
 
Ground control – a human operating a radio transmitter/receiver, a smartphone, a tablet, a computer, or the original meaning of a military ground control station (GCS). Recently control from wearable devices, human movement recognition, human brain waves was also demonstrated.
Remote network system, such as satellite duplex data links for some military powers. Downstream digital video over mobile networks has also entered consumer markets, while direct UAV control uplink over the celullar mesh is under researched.
Another aircraft, serving as a relay or mobile control station - military manned-unmanned teaming (MUM-T).

Functions


Full autonomy is available for particular tasks, such as airborne refueling or ground-based battery switching.
 
Higher-level tasks call for greater computing, sensing and actuating capabilities.

Autonomous Control Levels chart
Level Level descriptor Observe Orient Decide Act
  Perception/Situational awareness Analysis/Coordination Decision making Capability
10 Fully Autonomous Cognizant of all within battlespace Coordinates as necessary Capable of total independence Requires little guidance to do job
9 Battlespace Swarm Cognizance Battlespace ingerence - Intent of self and others (allied and foes).

Complex/Intense environment - on-board tracking

Strategic group goals assigned

Enemy strategy inferred

Distributed tactical group planning

Individual determination of tactical goal

Individual task planning/execution

Choose tactical targets

Group accomplishment of strategic goal with no supervisory assistance
8 Battlespace Cognizance Proximity inference - Intent of self and others (allied and foes)

Reduces dependence upon off-board data

Strategic group goals assigned

Enemy tactics inferred

ATR

Coordinated tactical group planning

Individual task planning/execution

Choose target of opportunity

Group accomplishment of strategic goal with minimal supervisory assistance

(example: go SCUD hunting)

7 Battlespace Knowledge Short track awareness - History and predictive battlespace

Data in limited range, timeframe and numbers

Limited inference supplemented by off-board data

Tactical group goals assigned

Enemy trajectory estimated

Individual task planning/execution to meet goals Group accomplishment of tactical goals with minimal supervisory assistance
6 Real Time

Multi-Vehicle Cooperation

Ranged awareness - on-board sensing for long range,

supplemented by off-board data

Tactical group goals assigned

Enemy trajectory sensed/estimated

Coordinated trajectory planning and execution to meet goals - group optimization Group accomplishment of tactical goals with minimal supervisory assistance

Possible: close air space separation (+/-100yds) for AAR, formation in non-threat conditions

5 Real Time

Multi-Vehicle Coordination

Sensed awareness - Local sensors to detect others,

Fused with off-board data

Tactical group plan assigned

RT Health Diagnosis Ability to compensate

for most failures and flight conditions;

Ability to predict onset of failures

(e.g. Prognostic Health Mgmt)

Group diagnosis and resource management

On-board trajectory replanning - optimizes for current and predictive conditions

Collision avoidance

Self accomplishment of tactical plan as externally assigned

Medium vehicle airspace separation (100's of yds)

4 Fault/Event Adaptative

Vehicle

Deliberate awareness - allies communicate data Tactical group plan assigned

Assigned Rules of Engagement

RT Health Diagnosis; Ability to compensate

for most failures and flight conditions - inner loop changes reflected in outer loop performance

On-board trajectory replanning - event driven

Self resource management

Deconfliction

Self accomplishment of tactical plan as externally assigned

Medium vehicle airspace separation (100's of yds)

3 Robust Response to Real Time Faults/Events Health/status history & models Tactical group plan assigned

RT Health Diagnosis (What is the extent of the problems?)

Ability to compensate for most failures and flight conditions (i.e. adaptative inner loop control)

Evaluate status vs required mission capabilities

Abort/RTB is insufficient

Self accomplishment of tactical plan as externally assigned
2 Changeable mission Health/status sensors RT Health diagnosis (Do I have problems?)

Off-board replan (as required)

Execute preprogrammed or uploaded plans

in response to mission and health conditions

Self accomplishment of tactical plan as externally assigned
1 Execute Preplanned

Mission

Preloaded mission data

Flight Control and Navigation Sensing

Pre/Post flight BIT

Report status

Preprogrammed mission and abort plans Wide airspace separation requirements (miles)
0 Remotely

Piloted

Vehicle

Flight Control (attitude, rates) sensing

Nose camera

Telemetered data

Remote pilot commands

N/A Control by remote pilot

 

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