Radio control

Radio control (often abbreviated to R/C or simply RC) is the use of radio signals to remotely control a device. The term is used frequently to refer to the control of model vehicles from a hand-held radio transmitter. Industrial, military, and scientific research organizations make use of radio-controlled vehicles as well.

History

In 1898 at an exhibition at Madison Square Garden Nikola Tesla demonstrated a small boat which could apparently obey commands from the audience but was in fact controlled by Tesla interpreting the verbal requests and sending appropriate frequencies to tuned circuits in the boat. He was granted a US patent on this invention on November 8, 1898. [http://www.lindsaybks.com/arch/rdy/index.html] In 1904, "Bat", a Windermere steam launch, was controlled using experimental radio control by its inventor, Jack Kitchen.In 1909 the French inventor Gabet demonstrated what he called his "Torpille Radio-Automatique", a radio controlled torpedo [http://www.ctie.monash.edu.au/hargrave/rpav_home.html#Gabet] In 1917, Archibald Low as head of the RFC Experimental Works, was the first person to use radio control successfully on an aircraft.In the 1920s, various radio-controlled ships were used for naval artillery target practice.The Soviet Red Army used remotely controlled teletanks during 1930s in the Winter War against Finland and fielded at least two teletank battalions at the beginning of the Great Patriotic War. A teletank is controlled by radio from a control tank at a distance of 500–1,500 meters, the two constituting a "telemechanical group". There were also remotely controlled cutters Iand experimental remotely controlled planes in the Red Army. In the 1930s Britain developed the radio controlled "Queen Bee", a remotely controlled unmanned Tiger Moth aircraft for a fleet's gunnery firing practice. The "Queen Bee" was superseded by the similarly named "Queen Wasp", a later, purpose built, target aircraft of higher performance.

Military applications in the Second World War

Radio control was further developed during World War II, primarily by the Germans who used it in a number of missile projects. Their main effort was the development of radio-controlled missiles and glide bombs for use against shipping, a target that is otherwise both difficult and dangerous to attack. However by the end of the war the Luftwaffe was having similar problems attacking Allied bombers, and developed a number of radio-controlled anti-aircraft missiles, none of which saw service.

The effectiveness of the Luftwaffe systems was greatly reduced by British efforts to jam their radio signals. After initial successes, the British launched a number of commando 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 to wire guidance once they realized what was going on, but these systems were not ready for deployment until the war had already moved to France.

The German Kriegsmarine operated FL-Boote (ferngelenkte Sprengboote) which were radio controlled motor boats filled with explosives to attack enemy shipping from 1944.

Both the British and US also developed radio control systems for similar tasks, in order to avoid the huge anti-aircraft batteries set up around German targets. However, none of these systems proved usable in practice, and the one major US effort, "Project Aphrodite", proved to be far more dangerous to its users than to the target.

Radio control systems of this era were generally electromechanical in nature, using small metal "fingers" or "reeds" with different resonant frequencies each of which would operate one of a number of different relays when a particular frequency was received. The relays would in turn then activate various actuators 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.

These systems were widely used until the 1960s, when the increasing use of solid state systems greatly simplified radio control. The electromechanical systems using reed relays were replaced by similar electronic ones, and the continued miniaturization of electronics allowed more signals, referred to as "control channels", to be packed into the same package. While early control systems might have two or three channels using amplitude modulation, modern systems include 20 or more using frequency modulation.

Radio-controlled models

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 of transistors 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 rudder control (right, left, and neutral) and sometimes other functions such as motor speed. [ [http://www.fortsmithflightmasters.com/fp/fp040701.html Fort Smith Flightmasters: Radio Control Systems (Part 2)] with illustrations of an early installation and descriptions of various escapements.]

Crystal-controlled superheterodyne 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 can get away with two or one.

As the electronics revolution took off, single-signal channel circuit design became redundant, and instead radios provided coded signal streams which a servomechanism could interpret.

More recently, high-end hobby systems using Pulse-Code Modulation (PCM) features have come on the market that provide a computerized digital bit-stream signal to the receiving device, instead of analog type pulse modulation.

In the early 21st century, 2.4 gigahertz tramsissions have become increasingly utilised in high-end control of model vehicles and aircraft.

Modern military and aerospace applications

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 completely , computerized automatic 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 the Mars Exploration Rovers such as Sojourner.

Industrial control

Today radio control is used in industry for such devices as overhead cranes and switchyard locomotives. Radio-controlled teleoperators are used for such purposes as inspections, and special vehicles for disarming of bombs. Some remotely-controlled devices are loosely called robots, but are more properly categorized as teleoperators since they do not operate autonomously, but only under control of a human operator.

See also

* Air engine
* Radio-controlled model
* Radio-controlled car
* Radio-controlled boat
* Radio-controlled airplane
* Radio-controlled helicopter
* Teletank

Notes