Radio control (often abbreviated toRC) is the use ofcontrol signals transmitted byradio toremotely operate a device. Examples of simple radio control systems aregarage door openers andkeyless entry systems for vehicles, in which a small handheld radio transmitter unlocks or opens doors. Radio control is also used for control ofmodel vehicles from a hand-heldradio transmitter.Industrial,military, andscientific research organizations make use of radio-controlled vehicles as well. A rapidly growing application is control ofunmanned aerial vehicles (UAVs or drones) for both civilian and military uses, although these have more sophisticated control systems than traditional applications.
The idea of controlling unmanned vehicles (for the most part in an attempt to improve the accuracy oftorpedoes for military purposes) predates the invention of radio. The latter half of the 1800s saw development of many such devices, connected to an operator by wires, including the first practical application invented by German engineerWerner von Siemens in 1870.[1]
Getting rid of the wires via using a new wireless technology, radio, appeared in the late 1890s. In 1897 British engineer Ernest Wilson and C. J. Evans patented a radio-controlled torpedo or demonstrated radio-controlled boats on theThames river (accounts of what they did vary).[2][3] At an 1898 exhibition atMadison Square Garden,Nikola Tesla demonstrated a small boat that used acoherer-based radio control.[4] With an eye towards selling the idea to the US government as a torpedo, Tesla's 1898 patent included a clockwork frequency changer so an enemy could not take control of the device.[5]
In 1903, the Spanish engineerLeonardo Torres Quevedo introduced a radio based control system called the "Telekino"[6] at theParis Academy of Sciences. In the same year, he applied for several patents in other countries.[7][8] It was intended as a way of testingAstra-Torres airship, a dirigible of his own design, without risking human lives.[9] Unlike the previous mechanisms, which carried out actions of the 'on/off' type, Torres established a system for controlling any mechanical or electrical device with different states of operation. This method required a transmitter capable of sending a family of differentcode words by means of a binarytelegraph key signal, and a receiver, which was able to set up a different state of operation in the device being used, depending on the code word. It was able to select different positions for thesteering engine and different velocities for thepropelling engine independently, and also to act over other mechanisms such anelectric light, for switching it, and aflag, for raising or dropping it, at the same time,[10] and so up to 19 different actions.[11] In 1904, Torres chose to carry out the first test on a three-wheeled land vehicle with a range of 20 to 30 meters.[12] In 1906, in the presence of an audience which included KingAlfonso XIII of Spain, Torres demonstrated the invention in thePort of Bilbao, guiding the electrically powered launchVizcaya from the shore with people on board, which was controlled at a distance over 2 km.[13]
In 1904,Bat, aWindermere steam launch, was controlled using experimental radio control by its inventor, [Jack Kitchen]. In 1909 French inventor [Gabet] demonstrated what he called his "Torpille Radio-Automatique", a radio-controlled torpedo.[14]
In 1917,Archibald Low, as head of the secretRoyal Flying Corps (RFC) experimental works atFeltham, was the first person to use radio control successfully on an aircraft, a1917 Aerial Target. It was "piloted" from the ground by future world aerial speed record holderHenry Segrave.[15] Low's systems encoded the command transmissions as a countermeasure to prevent enemy intervention.[16] By 1918 the secretD.C.B. Section of the Royal Navy's Signals School, Portsmouth under the command ofEric Robinson V.C. used a variant of the Aerial Target’s radio control system to control from ‘mother’ aircraft different types of naval vessels including a submarine.[17]
During World War I American inventorJohn Hays Hammond, Jr. developed many techniques used in subsequent radio control including developing remote controlled torpedoes, ships, anti-jamming systems and even a system allowing his remote-controlled ship targeting an enemy ship's searchlights.[18] In 1922 he installed radio control gear on the obsolete US Navy battleshipUSSIowa so it could be used as atarget ship[19] (sunk in gunnery exercise in March 1923).
The SovietRed Army used remotely controlledteletanks during the 1930s in theWinter War againstFinland and fielded at least two teletank battalions at the beginning of theGreat Patriotic War. A teletank is controlled by radio from a control tank at a distance of 500–1500 m, the two constituting atelemechanical group. There were also remotely controlled cutters and experimental remotely controlled planes in the Red Army.
The United Kingdom's World War One development of their radio-controlled 1917 'Aerial Target' (AT) and 1918 'Distant Control Boat' (DCB) using Low's control systems led eventually to their 1930s fleet of "Queen Bee". This was a remotely controlled unmanned version of thede Havilland "Tiger Moth" aircraft forNavy fleet gunnery firing practice. The "Queen Bee" was superseded by the similarly namedAirspeed Queen Wasp, a purpose-built target aircraft of higher performance.
Radio control was further developed during World War II, primarily by the Germans who used it in a number ofmissile projects. Their main effort was the development ofradio-controlled missiles andglide bombs for use against shipping, a target otherwise both difficult and dangerous to attack. However, by the end of the war, theLuftwaffe was having similar problems attacking Alliedbombers and developed a number of radiocommand guidedsurface-to-air anti-aircraft missiles, none of which saw service.
The effectiveness of theLuftwaffe's systems, primarily comprising the series ofTelefunkenFunk-Gerät (or FuG) 203Kehl twin-axis, single joystick-equipped transmitters mounted in the deploying aircraft, and Telefunken's companion FuG 230Straßburg receiver placed in the ordnance to be controlled during deployment and used by both theFritz X unpowered, armored anti-ship bomb and the poweredHenschel Hs 293 guided bomb, was greatly reduced by British efforts to jam their radio signals, eventually with American assistance. After initial successes, the British launched a number ofcommando raids to collect the missile radio sets. Jammers were then installed on British ships, and the weapons basically "stopped working". The German development teams then turned towire-guided missiles once they realized what was going on, but the systems were not ready for deployment until the war had already moved to France.
The GermanKriegsmarine operatedFL-Boote (ferngelenkte Sprengboote) which were radio controlledmotor boats filled with explosives to attack enemy shipping from 1944.
Both the British and US also developed radio control systems for similar tasks, to avoid the huge anti-aircraft batteries set up around German targets. However, no system proved usable in practice, and the one major US effort,Operation Aphrodite, proved to be far more dangerous to its users than to the target. The AmericanAzon guided free-fall ordnance, however, proved useful in both theEuropean andCBI Theaters of World War II.
Radio control systems of this era were generally electromechanical in nature, using small metal "fingers" or "reeds" with differentresonant frequencies each of which would operate one of a number of differentrelays when a particular frequency was received. The relays would in turn then activate variousactuators acting on the control surfaces of the missile. The controller's radio transmitter would transmit the different frequencies in response to the movements of a control stick; these were typically on/off signals. The radio gear used to control the rudder function on the American-developedAzon guided ordnance, however, was a fully proportional control, with the "ailerons", solely under the control of an on-board gyroscope, serving merely to keep the ordnance from rolling.
These systems were widely used until the 1960s, when the increasing use ofsolid state systems greatly simplified radio control. The electromechanical systems usingreed relays were replaced by similar electronic ones, and the continued miniaturization of electronics allowed more signals, referred to ascontrol channels, to be packed into the same package. While early control systems might have two or three channels usingamplitude modulation, modern systems include twenty or more usingfrequency modulation.
The first general use of radio control systems in models started in the early 1950s with single-channel self-built equipment; commercial equipment came later. The advent oftransistors greatly reduced the battery requirements, since the current requirements at low voltage were greatly reduced and the high voltage battery was eliminated. In both tube and early transistor sets the model's control surfaces were usually operated by an electromagnetic 'escapement' controlling the stored energy in a rubber-band loop, allowing simple on/off rudder control (right, left, and neutral) and sometimes other functions such as motor speed.[20]
Crystal-controlledsuperheterodyne receivers with better selectivity and stability made control equipment more capable and at lower cost. Multi-channel developments were of particular use to aircraft, which really needed a minimum of three control dimensions (yaw, pitch and motor speed), as opposed to boats, which required only two or one.
As the electronics revolution took off, single-signal channel circuit design became redundant, and instead radios provided proportionally coded signal streams which aservomechanism could interpret, usingpulse-width modulation (PWM).
More recently, high-endhobby systems usingpulse-code modulation (PCM) features have come on the market that provide acomputerizeddigital databit-stream signal to the receiving device, instead of the earlier PWM encoding type. However, even with this coding, loss of transmission during flight has become more common[citation needed], in part because of the ever more wireless society. Some more modern FM-signal receivers that still use "PWM" encoding instead can, thanks to the use of more advanced computer chips in them, be made to lock onto and use the individual signal characteristics of a particular PWM-type RC transmitter's emissions alone,without needing a special "code" transmitted along with the control information as PCM encoding has always required.
In the early 21st century, 2.4 gigahertzspread spectrum RC control systems have become increasingly utilized in control of model vehicles and aircraft. Now, these 2.4 GHz systems are being made by most radio manufacturers. These radio systems range in price from a couple thousanddollars, all the way down to under US$30 for some. Some manufacturers even offer conversion kits for older digital 72 MHz or 35 MHz receivers and radios. As the emerging multitude of 2.4 GHz band spread spectrum RC systems usually use a "frequency-agile" mode of operations, likeFHSS that do not stay on one set frequency any longer while in use, the older "exclusive use" provisions at model flying sites needed for VHF-band RC control systems' frequency control, for VHF-band RC systems that only used one set frequency unless serviced to change it, are not as mandatory as before.
Remote control military applications are typically not radio control in the direct sense, directly operating flight control surfaces and propulsion power settings, but instead take the form of instructions sent to a completelyautonomous, computerizedautomatic pilot. Instead of a "turn left" signal that is applied until the aircraft is flying in the right direction, the system sends a single instruction that says "fly to this point".
Some of the most outstanding examples of remote radio control of a vehicle are theMars Exploration Rovers such asSojourner.
Today radio control is used in industry for such devices as overheadcranes and switchyardlocomotives. Radio-controlledteleoperators are used for such purposes as inspections, and special vehicles for disarming ofbombs. Some remotely controlled devices are loosely calledrobots, but are more properly categorized as teleoperators since they do not operate autonomously, but only under control of a human operator.
An industrial radio remote control can either be operated by a person, or by a computer control system in amachine to machine (M2M) mode. For example, an automated warehouse may use a radio-controlled crane that is operated by a computer to retrieve a particular item. Industrial radio controls for some applications, such as lifting machinery, are required to be of a fail-safe design in many jurisdictions.[21]
Industrial remote controls work differently from most consumer products. When the receiver receives the radio signal which the transmitter sent, it checks it so that it is the correct frequency and that any security codes match. Once the verification is complete, the receiver sends an instruction to arelay which is activated. The relay activates a function in the application corresponding to the transmitters button. This could be to engage an electrical directional motor in anoverhead crane.In a receiver there are usually several relays, and in something as complex as an overhead crane, perhaps up to twelve or more relays are required to control all directions. In a receiver which opens a gate, two relays are often sufficient.[22]
Industrial remote controls are getting more and higher safety requirements. For example: a remote control may not lose the safety functionality in case of malfunction.[23] This can be avoided by using redundant relays with forced contacts.
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