A radio-controlled model or RC model is a model that is steerable with the use of radio control. All types of model vehicles have had RC systems installed in them, including cars , boats , planes , and even helicopters and scale railway locomotives. Radio control has been around since Nikola Tesla demonstrated a remote control boat in World War II saw increased development in radio control technology.
The Luftwaffe used controllable winged bombs for targeting Allied ships. Their "Guff" radio controlled plane is on display at the National Aerospace museum.
Ed Lorenze published a design in Model Airplane News that was built by many hobbyists. Originally simple 'on-off' systems, these evolved to use complex systems of relays to control a rubber powered escapement's speed and direction. Commercial versions of these systems quickly became available. The tuned reed system brought new sophistication, using metal reeds to resonate with the transmitted signal and operate one of a number of different relays.
In the s the availability of transistor -based equipment led to the rapid development of fully proportional servo -based "digital proportional" systems, achieved initially with discrete components, again driven largely by amateurs but resulting in commercial products. In the s, integrated circuits made the electronics small, light and cheap enough for the s-established multi-channel digital proportional systems to become much more widely available.
In the s miniaturised equipment became widely available, allowing radio control of the smallest models, and by the s radio control was commonplace even for the control of inexpensive toys. At the same time the ingenuity of modellers has been sustained and the achievements of amateur modelers using new technologies has extended to such applications Fort Lauderdale Boat Excursions Project as gas-turbine powered aircraft, aerobatic helicopters and submarines. Before radio control, many models would use simple burning fuses or clockwork mechanisms to control flight or sailing times.
Sometimes clockwork controllers would also control and vary direction or behaviour. Other methods included tethering to a central point popular for model cars and hydroplanes , round the pole control for electric model aircraft and control lines called u-control in the US for internal combustion powered aircraft.
The first general use of radio control systems in models started in the late s with single-channel self-built equipment; commercial equipment came soon thereafter. Initially remote control systems used escapement , often rubber driven mechanical actuation in the model.
Commercial sets Fort Lauderdale Boat Excursions Number often used ground standing transmitters, long whip antennas with separate ground poles and single vacuum tube receivers. The first kits had dual tubes for more selectivity.
Such early systems were invariably super regenerative circuits, which meant that two controllers used in close proximity would interfere with one another. The requirement for heavy batteries to drive tubes also meant that model boat systems were more successful than model aircraft. 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.
Low cost systems employed a superregenerative transistor receiver sensitive to a specific audio tone modulation, the latter greatly reducing interference from 27 MHz Citizens' band radio communications on nearby frequencies.
Use of an output transistor further increased reliability by eliminating the sensitive output relay , a device subject to both motor-induced vibration and stray dust contamination. 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, and kick-up elevator.
In the late s, RC hobbyists had mastered tricks to manage proportional control of the flight control surfaces, for example by rapidly switching on and off reed systems, a technique called "skillful blipping" or more humorously "nervous proportional".
By the early s transistors had replaced the tube and electric motors driving control surfaces were more common. The first low cost "proportional" systems did not use servos, but rather employed a bidirectional motor with a proportional pulse train that consisted of two tones, pulse width modulated TTPW.
A more sophisticated and unique proportional system was developed by Hershel Toomin of Electrosolids corporation called the Space Control. This benchmark system used two tones, pulse width and rate modulated to drive 4 fully proportional servos, and was manufactured and refined by Zel Ritchie, who ultimately gave the technology to the Dunhams of Orbit in The system was widely imitated, and others Sampey, ACL, DeeBee tried their hand at developing what was then known as analog proportional.
But these early analog proportional radios were very expensive, putting them out of the reach for most modelers. Eventually, single-channel gave way to multi channel devices at significantly higher cost with various audio tones driving electromagnets affecting tuned resonant reeds for channel selection. Crystal oscillator superheterodyne receivers with better selectivity and stability made control equipment more capable and at lower cost. The constantly diminishing equipment weight was crucial to ever increasing modelling applications.
Superheterodyne circuits became more common, enabling several transmitters to operate closely together and enabling further rejection of interference from adjacent Citizen's Band voice radio bands.
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 be controlled with two or one. Radio control 'channels' were originally outputs from a reed array, in other words, a simple on-off switch. To provide a usable control signal a control surface needs to be moved in two directions, so at least two 'channels' would be needed unless a complex mechanical link could be made to provide two-directional movement from a single switch.
Several of these complex links were marketed during the s, including the Graupner Kinematic Orbit, Bramco, and Kraft simultaneous reed sets. With the electronics revolution, single-signal channel circuit design became redundant and instead, radios provided coded signal streams which a servomechanism could interpret. Each of these streams replaced two of the original 'channels', and, confusingly, the signal streams began to be called 'channels'.
Controlling all the primary controls of a powered aircraft rudder, elevator, ailerons and throttle was known as 'full-house' control.
A glider could be 'full-house' with only three channels. Soon a competitive marketplace emerged, bringing rapid development. By the Fort Lauderdale Boat Excursions Value s the trend for 'full-house' proportional radio control was fully established. Typical radio control systems for radio-controlled models employ pulse width modulation PWM , pulse position modulation PPM and more recently spread spectrum technology, and actuate the various control surfaces using servomechanisms. These systems made 'proportional control' possible, where the position of the control surface in the model is proportional to the position of the control stick on the transmitter.
The pulse is repeated in a frame of between 10 and 30 milliseconds in length. Off-the-shelf servos respond directly to servo control pulse trains of this type using integrated decoder circuits, and in response they actuate a rotating arm or lever on the top of the servo.
An electric motor and reduction gearbox is used to drive the output arm and a variable component such as a resistor " potentiometer " or tuning capacitor. The variable capacitor or resistor produces an error signal voltage proportional to the output position which is then compared with the position commanded by the input pulse and the motor is driven until a match is obtained.
The pulse trains representing the whole set of channels is easily decoded into separate channels at the receiver using very simple circuits such as a Johnson counter. The relative simplicity of this system allows receivers to be small and light, and has been widely used since the early s. More recently, high-end hobby systems using Pulse-Code Modulation PCM features have come on the market that provide a digital bit -stream signal to the receiving device instead of analog type pulse modulation.
Advantages include bit error checking capabilities of the data stream good for signal integrity checking and fail-safe options including motor if the model has a motor throttle down and similar automatic actions based on signal loss.
However, those systems that use pulse code modulation generally induce more lag due to lesser frames sent per second as bandwidth is needed for error checking bits.
PCM devices can only detect errors and thus hold the last verified position or go into failsafe mode. They cannot correct transmission errors. In the early 21st century, 2. This range of frequencies has many advantages. Because the 2. Electromagnetic noise, for example from electric motors, is not 'seen' by 2. The transmitter antenna only needs to be 10 to 20 cm long, and receiver power usage is much lower; batteries can therefore last longer.
In addition, no crystals or frequency selection is required as the latter is performed automatically by the transmitter. Also, should the receiver lose power, even for a few milliseconds, or get 'swamped' by 2. RC electronics have three essential elements. The transmitter is the controller.
Transmitters have control sticks, triggers, switches, and dials at the user's finger tips. The receiver is mounted in the model. It receives and processes the signal from the transmitter, translating it into signals that are sent to the servos and speed controllers.
The number of servos in a model determines the number of channels the radio must provide. Typically the transmitter multiplexes and modulates the signal into pulse-position modulation. The receiver demodulates and demultiplexes the signal and translates it into the special kind of pulse-width modulation used by standard RC servos and controllers. In the s, a Japanese electronics company, Futaba , copied wheeled steering for RC cars.
It was originally developed by Orbit for a transmitter specially designed for Associated cars It has been widely accepted along with a trigger control for throttle. Often configured for right hand users, the transmitter looks like a pistol with a wheel attached on its right side.
Pulling the trigger would accelerate the car forward, while pushing it would either stop the car or cause it to go into reverse. Some models are available in left-handed versions. There are thousands of RC vehicles available. Most are toys suitable for children. RC toys generally have simplified circuits, often with the receiver and servos incorporated into one circuit.
It's almost impossible to take that particular toy circuit and transplant it into other RCs. Hobby grade RC systems have modular designs. Many cars, boats, and aircraft can accept equipment from different manufacturers, so it is possible to take RC equipment from a car and install it into a boat, for example.
However, moving the receiver component between aircraft and surface vehicles is illegal in most countries as radio frequency laws allocate separate bands for air and surface models. This is done for safety reasons. Most manufacturers now offer "frequency modules" known as crystals that simply plug into the back of their transmitters, allowing one to change frequencies, and even bands, at will.
Some of these modules are capable of "synthesizing" many different channels within their assigned band. Hobby grade models can be fine tuned, unlike most toy grade models.
For example, cars often allow toe-in , camber and caster angle adjustments, just like their real-life counterparts. All modern "computer" radios allow each function to be adjusted over several parameters for ease in setup and adjustment of the model. Many of these transmitters are capable of "mixing" several functions at once, which is required for some models.
Radio-controlled aircraft also called RC aircraft are small aircraft that can be controlled remotely. There are many different types, ranging from small park flyers to large jets and mid-sized aerobatic models.
The aircraft use many different methods of propulsion, ranging from brushed or brushless electric motors, to internal combustion engines, to the most expensive gas turbines. Radio-controlled tanks are replicas of armored fighting vehicles that can move, rotate the turret and some even shoot all by using the hand-held transmitter.
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