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While drones have a number of constructive applications, such as planting fields, delivering packages and monitoring the safety of factory workers, their potential use in both the military and criminal realms have become a source of concern over the past few years. During the course of this blog, we’ll study a number of methods used to capture, disable and destroy hostile drones.
As drones wielding cameras are becoming progressively less expensive, developers of anti-drone technology have begun an industry of their own. Israeli engineers have recently developed a technique which not only detects a drone, but determines what it is viewing. They first create a recognizable pattern on the object to be viewed. Once the pattern is established, the drone’s radio signals are intercepted from a remote source to search for an identical pattern in the streaming video the drone sends back to its operator. If detected, they can determine they are being monitored by the drone. By use of this technique, the subject is able to see what the drone sees by pulling the pattern from the radio signal-even without cracking the drone’s encrypted video. This technique capitalizes on a video streaming feature known as delta frames. Instead of encoding the video as a series of raw images, it’s compressed into a series of changes from the previous image in the video, which means when a streaming video displays a still object, it transmits fewer bytes of data than when the subject is moving or changing colors. A number of tests at international sites have proven this compression feature can reveal key content of a video to the subject intercepting it. Though an effective technique, compression stream monitoring is too sophisticated for the average drone user.
Another method of drone detection is through the radio signal between the operator and the drone. The Aeroscope system, developed by the Chinese firm DJI, works by detecting the communication signal between the drone and its controller. It then decodes the signal and sends the drone’s telemetry data and registration to the Aeroscope box, much like that of a GPS display. If the owner of the offending drone is registered, an e-mail may be sent to the owner, advising them of local policies. While the Aeroscope system is currently only able to detect DJI drones, which represent about two-thirds of the drone market, enhancements are expected in the near future. Firmware updates will allow the Aeroscope to communicate with other drones based upon electronic signature. These communications will be in real time, as opposed to the current e-mails, which may not be read until days after the event. While the Aeroscope system has proven effective, it is too costly for the average drone enthusiast and primarily utilized by governmental agencies.
Another defense against drones is to capture them. This may be accomplished by using an interceptor drone or a land launched net. These drones use video cameras which are directed toward suspicious drones flying in unauthorized areas. Once the interceptor drone is within range of the suspect drone, it shoots a synthetic netting which wraps around the suspect’s propellers, forcing it down. The Tokyo Police have a fleet of interceptor drones, whose mission is to protect both public buildings and officials. The drones, which measure 3′ by 3′, deploy netting measuring 3′ by 6′ and have been largely successful, leading to the arrest of the drone operator in one case. Police in Britain use shoulder-mounted guns to intercept drones. The most sophisticated of these devices, developed by the British engineering firm Open Works, is a large bazooka, the SkyWall100, which fires a net and parachute at a target while using a high- power scope for aiming. The SkyWall system is a highly successful one, in global use by a number of security services and government agencies.
Several other methods of drone interception bear mention. During the last few years, both the United States and China have tested laser technology which can successfully shoot down a drone within seconds of interception. Boeing has recently developed a high energy beam that both locates and disables drones at a distance of several miles. This device utilizes infrared cameras, which are effective in conditions of low visibility. A novel approach was taken in the Netherlands, in which eagles were trained by Dutch police to bring down suspect drones by latching on to their propellers, rendering them ineffective. The eagles see the drones as prey and quickly lose interest in other pursuits. Drones may also be disabled by jamming their operating frequencies. Two such devices have come into use, the Anti-UAV Defense System (AUDS), scans the skies for hostile drones by use of a high-powered radio signal. A portable system, which utilizes targeted radio signals to disrupt drone controls is the DroneDefender. The Defender system is an electronic rifle which operates in the same manner as the AUDS device. These currently have a range of about 1,500 ft, with more capable units under development. The potential problem with using both the AUDS and Defender systems are their capability to jam local radar transmitters, a source of legal problems. Finally, several drone manufacturers have collaborated to establish no fly zones for their drones. If you add your address to their database, any drones made by these manufacturers will be unable to fly over your property due to built-in GPS restrictions. Though a viable concept, not all manufacturers are willing to allow access to their database, as well as no law to enforce its use.
Ever since the wingspan of rc models exceeded three feet in length, proper storage of flying models has been an issue. During this blog, we’ll look at several methods of storing radio control planes under different conditions.
For rc modelers who have a large number of aircraft, the best approach is to get them off the floor to prevent damage from a number of sources. The use of hangers, while not a new idea, will serve to mount the models from the ceiling where they may hang freely out of harm’s way. The most common hangers are designed smaller aircraft weighing under four pounds. Heavier models will require larger hangers. An appropriate hanger size would be a 4′ by 3/16″ steel rod, big enough to reach a ceiling beam as well as strong enough to support the plane. Bike hooks and smaller scale hooks may also be used to mount the hanger in the ceiling, depending upon the weight and size of the model. Suggested tools are a ruler, vise, sandblaster or sandpaper, a degreaser, drill, stud finder, and pencil. Optional tools include 24″ by 3/16″ inside diameter tubing for padding the rod where the wings are supported in addition to glass cleaner or hairspray.
The first step to preparing the hangers is to bend the steel rods. Find and mark the center point of the rod, securing it to a vise then bending a 90-degree angle into the rod. Remove from the vise and complete the bend so the rod is folded in half. Use the vise again, if necessary to reinforce the bend. Find the center of the bent piece, bending it again to about 45-degrees, spreading the legs out slightly wider than the plane’s fuselage. You can work different bends which correspond to the fuselage shape. Next, prepare the hangers for painting. This may be accomplished by using either a sandblaster or a bench grinder with a wire wheel. Sandpaper may also be used. The purpose is to remove any residual oils from the metal in order to give a good surface for the paint to adhere. A degreaser or TSP will clean up any remaining residue. Then, spray paint the hangers, making sure to let them dry completely. The next step is to add tubing to insulate the hanger where it contacts the wing. Be sure the inside diameter of the tube matches the outside diameter of the rod. This will act as a buffer between the hanger and the wing of the rc plane, advantageous for heavier planes as well as those having a delicate finish. Hairspray and glass cleaner are good treatments for the hanger surface with hairspray acting as an adhesive as it drys. Finally, mount the hooks in the ceiling, draping the hangers through the hooks.
Planes may also be mounted on the wall area of a garage or storage building. If space allows, the entire aircraft may be secured with hangers draped around wall mounted hooks, as with the ceiling example. However, if storage space is limited, the fuselage and wing components may need to be stored separately. By using metal shelf brackets placed about two feet above the floor level supporting a wooden shelf, wings may be placed in small storage bins on the shelf. In this mode, the wings are high enough not to be disturbed by traffic inside the area, yet low enough not to conflict with fuselage storage. Fuselages may be hung by either the tail or propeller, with the tail preferred due to the larger surface area. The disadvantage of tail hanging is gasoline accumulation near the engine. Rotating fuselage positions may help in overcoming this. Finally, if no other space is available, an appropriate rc plane makes a good decorator item for a den or rec room.
Another method of storage, which has gained favor in recent years, is the use of PVC tubing. Its advantages are simplicity, flexibility, and a relatively low cost. With the use of a scissors-like cutting tool, PVC tubing may be cut to any length or configuration. While three to four-tier racks are the most popular configuration, many variations are in use. Since PVC racks are light, they are easily transportable, allowing an rc pilot the opportunity to fly several planes at an event. Cement is usually not necessary to secure PVC tubing, since the tubing is usually snug at the 90-degree joints. PVC pipes may also be used with metal hangers and hooks with the PVC acting as an insulator, as well as a work stand frame for rc models.
RC model stores sell a variety of storage kits, with most priced about $50, depending upon the configuration and type of kit. Some avid enthusiasts have even purchased outdoor buildings in which to store their planes. With all of the possibilities, rc model storage is not a one size fits all endeavor.
To view a large-scale model in flight is an impressive experience. These rc planes have a number of features, such as flaps, sliding canopies and landing lights, which convey the impression of a real aircraft. However, the complexity of these models poses a problem for the rc pilot. During this blog, we’ll examine some of the problems associated with flying a large rc model.
The first issue of flying a large rc plane is a reliable power source. While lipo (lithium polymer) batteries now offer near gasoline power in some applications, gasoline engines remain the best choice to provide sustained power over a long flight. Speaking of fuel, carefully check all fuel lines and make sure they are properly connected. Make sure you have the correct diameter and type of line for the fuel you are using. All of the rc’s fuel should be filtered, with periodic filter changes advisable. A number of models now have a filter in the filing line, as well as one between the carburetor and the fuel tank. If the rc pilot is using glow fuel or gasoline, he may use either, but not both as they are not interchangeable. The rc pilot should also make sure the fuel tank clunk stays free from the front of the tank and does not bend, which could obstruct the flow of fuel, producing a rough take off.
Flight control surfaces are an important component, as well. The rc operator must make sure all control linkages are both properly secured and pivot according to transmitter commands. Ailerons, elevators, and rudders should have equal parameters of movement in each direction. This is especially true of flaps, which aid in landing and flight stability at low speeds. Flap hinges should work freely, without binding. Servo mounts also pose a problem, as they tend to work loose after repeated flights. Check them after each flight to ensure they are secure and functioning. Engine mounts and mufflers are also prone to vibration. Carefully balancing the props will help, but vibrations are an inherent problem with large rc models. Replace propeller blades when necessary to keep the aircraft running smoothly, since they cost a fraction of replacing an entire plane.
Range checks are essential to gauge whether a radio signal allows the plane to fly at a safe distance without it going out of radio range. To conduct a range check, first turn on the transmitter, then the receiver and fully retract the antenna. Activate the transmitter while walking back from the plane between seventy-five and one-hundred feet. As you walk away from the plane, keep moving the control surface sticks and closely watch the various control surfaces of the plane. If you experience a hesitation or a lack of movement of the control surfaces, do not attempt to fly the aircraft. Check the transmitter batteries, as they may need recharging or replacing, since low batteries may drastically reduce radio range. Loose connections to the receiver could also cause a lack of response from control surfaces. If control surfaces are still unresponsive, there may be signal interference from other rc hobbyists on your frequency. Interference is a leading cause of rc aircraft crashes, so you need to be sure your frequency is clear before taking off. Whatever the cause, if your rc plane appears difficult to control, correct the problem before flying.
Though not always practiced, test glides of the aircraft are advisable, particularly if the rc model is a powered glider or a large aircraft. The reason for doing this to determine the glide pattern of the plane, should it suddenly lose power. A test glide is best conducted over long grass if possible. This is necessary to ensure a soft landing for the plane should there be turbulence. Test glides may also be used to confirm the balance of the plane with regard to weight distribution and center of gravity. Always take off and land in a flat, level area if possible. Finally, have fun but use common sense; avoid flying too close to people or property yet keeping the plane at a sensible height and distance while maintaining control, as well as keeping an eye out for other rc pilots.
While the operation of radio control models as a hobby is a relatively recent event, the technology behind the hobby dates back to the nineteenth century. During the course of this blog, we’ll trace the evolution of rc model transmitters and their applications.
The first use of radio control technology dates back to 1898, when Nikola Tesla built a pair of radio controlled boats, demonstrating them to a shocked crowd at Madison Square Garden. Though only able to cruise a short distance, the boats showed the potential of radio control. During World War I, Archibald Low designs an aerial drone plane for the Royal Flying Corps for use as a radio-controlled guided bomb. By the 1930s practical rc planes were available to hobbyists, with Walter and William Good building and flying the first fully-functional rc aircraft in 1937. As a result of progress in radio control technology during World War II, the use of rc models increased dramatically during the 1950s, though the battery capacities were limited and needed frequent rechargings until transistors became available.
Transistors also reduced the voltage requirements of a battery, virtually eliminating the older high voltage batteries. One channel rc radio kits were introduced in the 1950s with preassembled units offered later. In both tube and transistor radios of the era, the rc planes control functions were operated by an electromagnetic escapement utilizing a rubber- band loop system from which the rc pilot could control rudder and speed functions. By the 1960s, crystal-controlled superheterodyne receivers became available. These offered a true three-dimensional control of rc aircraft (yaw, pitch and motor speed). Heterodyne receivers also provided a more sensitive signal selection coupled with a more stable rc model control. After World War II commercial rc planes control signals were limited to two or three channels using amplitude modulation. More channel choices were added in the 1960s using frequency modulation, which offered twenty or more operating channels.
The next generation of rc model transmitters was developed in the mid-1970s. A Pulse Width Modulation (PWM) Signal is a method by which an analog signal is produced using a digital source. PWM signals consist of two primary components that define its behavior: a duty cycle and a frequency. The duty cycle is the amount of time the signal is in a high (on) state as a percentage of the total time it takes to complete one cycle. The frequency determines how fast the PWM completes a cycle, and consequently how fast it switches between high and low states. By cycling a digital signal on and off at a fast enough rate, and with a certain duty cycle, the output will appear to behave like a constant voltage analog signal when providing power to devices. These signals transmitted in a rapid succession could control multiple functions on the rc model.
On the heels of PWM signal technology Pulse Code Modulation (PCM) was developed. While analog technology uses continuous signals, digital technology encodes the information into discrete signal states. With two states assigned per digital signal, they are called binary signals, while a single binary digit is termed a bit. While PCM is an efficient means of signal transmission, it is by no means foolproof due to the proliferation of radio control devices in both the hobby and industrial markets. To overcome this problem, some late model FM receivers which still use PWM coding can be modified by the use of advanced computer chips to detect the individual signal characteristics of a particular Pulse Width Modulation without needing a designated code, as required with PCM coding.
By the early 2000s, Spread Spectrum rc contol systems came into use. A Spread Spectrum rc control system uses a variable frequency of operation, usually in the 2.4 gigahertz band, in which the rc transmitter stays on a given frequency for a minimal amount of time. With the enhanced security offered by Spread Spectrum systems, an increasing number of radio manufacturers are offering the units to hobbyists at a price from $3,000 to as low as $30. A number of manufacturers are now selling conversion kits for older digital 72 MHz radios and receivers, providing even more options for the rc model operator.
Though flying an rc model can be a fun activity, certain safety considerations must be observed in order to make the flight both a safe and enjoyable experience. During this blog, we’ll take a look at buying an rc plane or helicopter from the safety standpoint, as well as techniques to promote safe flying.
Real aircraft must undergo a pre-flight checklist, which is also a good philosophy for radio control aircraft. The pilot must make sure the rudder, ailerons, and elevators are functioning properly, with both the receiver battery and radio fully charged. The problem with rc planes, as opposed to rc helicopters, is the center of gravity. The center of gravity is a point at which the plane needs to balance in order to fly well. The center of gravity for a plane with a tail can be as far back as 32% from the nose of the plane of the plane, though the operator may still have to make it balance. While placement of the battery and radio can compensate for any CG imbalance, it’s always desirable to have both a light nose and tail section of the aircraft, with adjustments made at the center of the fuselage. A properly balanced plane will be more responsive to commands and use less fuel/battery charge. Flying wing designs have a common center of gravity at 23% back from the nose.
Before launching the plane, be sure the correct propellers are installed. The thickest section of the prop should be facing toward the front, The rc pilot can determine the front of the blade by manufacturer lettering. The plane will still fly with the prop(s) mounted backward, though at about a third of the power of a front mounted blade since the thicker front section displaces more air. Better quality props are more rigid, and thus more stable in flight – especially at high rpms. They are also less likely to flatten out over extended use. Getting a good launch of the aircraft is more difficult than it appears. Inexperienced rc pilots have a tendency to spin the plane, often a cause of crashes. If one wingtip is moving faster than the other, it will have more air over the wing, so the plane will roll towards the slower wing. The correct procedure is to release the plane when both wings are level and moving in the same direction at the same speed. If the model is launched at too steep an angle, it will experience an immediate stall.
Transmitters are an important element of rc flight. Many rc pilots have a tendency to fly their planes by their thumbs. Clutch the transmitter sticks on the side with the elevons or elevator-ailerons control. This offers the rc pilot more than one orientation to the controls and prevents accidental maneuvers of the rc plane. Don’t jerk the control sticks, but rather use a gradual motion from which to control the model. Proper antenna angle is another factor, since there may be local interference, which affects signal quality. Fly the plane at a close distance, using different antenna angles to determine the optimum signal. While more recent rc planes are equipped with a homing device, which returns the plane to the transmitter if the model experiences signal or line of sight interference, it’s always best to fly your rc plane no farther than your field of view. A three channel transmitter with throttle, rudder and elevator controls is usually the best for a beginner. Speaking of planes, the most important decision facing beginning rc pilots is choice of aircraft. The hard fact is the plane will experience a number of crashes until the pilot becomes more proficient. Foam is a relatively inexpensive material and easy to repair if the rc plane is damaged. While a foam aircraft construction is not the most pleasing to the eye, it provides the rc model beginner with a practical means of getting into the air. RC models may be purchased in either ready to fly (RTF) or in kit form, which must be assembled. Building your own model has the advantages of learning the parts and operating systems of the plane, as well as a lower cost. RC model planes may be powered by either gasoline engines or lithium polymer (LIPO) batteries. The use of lipo batteries has increased drastically in radio control use over the last ten years. They offer near gasoline engine performance while being more compact, with little or no maintenance.
The use of radio control aircraft, quadcopters and drones have increased exponentially over the last fifteen years. Near collisions between drones and passenger aircraft now run into the hundreds each year, with the FAA receiving in excess of 100 reports per month. While most drones weigh less than ten pounds and have a limited altitude, heavier and more capable machines are the rise. For example, even a collision between a lightweight drone and a jetliner could result in millions of dollars if the jetliner sustained damage to either the engine or control surfaces. Though the FAA has a regulation in effect for four years making it illegal to fly a drone within five miles of an airport and limiting the altitude to 400 ft., many operators who use drones in their business pay scant attention. A year later the FAA enacted a five dollar registration fee for all drones weighing more than half a pound. While ineffective at tracking drones, it may get the attention of some operators. For all the electronics and regulations, perhaps the best source of rc model safety is common sense in their use.
During the last five years, the use of and uses for drones have increased exponentially. In this blog, we’ll trace the employment of drones in a number of industries.
While much of the current drone technology isn’t new, recent investments in both capital and technology have made drones a practical tool in a number of industries. The agricultural sector is one in which drone applications are on the rise. With the global population projected to reach about 9 billion by 2050 and agricultural consumption to increase by 70 per cent during the same period, the use of drones in agriculture has the potential of revolutionizing that sector of the economy. Such drones are high-tech systems which perform many tasks a farmer can’t, such as conducting soil scans, monitoring crop health, applying fertilizers and water, even tracking weather and estimating yields, as well as collecting and analyzing data. With the FAA currently streamlining regulations for agri-drone use, the market for such systems has the potential for approximately 80% of all drones produced, according to a recent study by Bank of America Merrill Lynch.
A number of construction companies are exploring the possibilities of utilizing drones or UAVs (Unmanned Aerial Vehicles) in that industry. Drones have a number of roles in the construction industry: among them are marketing, surveying, inspection, progress reporting, safety and monitoring workers at multiple sites. In the survey role, drones allow contractors to get detailed information about a job site, as well as conditions on surrounding properties. While site surveyors are necessary in some situations, drones can perform essentially the same function at a fraction of the cost. In the realm of construction inspection, drones offer a high degree of flexibility. For example, drones can effectively scan the roof of a skyscraper, revealing any possible construction faults. They are also useful at sites such as tunnels and bridges, which may be inaccessible from the surrounding land. The contractor can even use the drone to compare the construction to the actual plans of a project. Drone photography can be utilized to show aerial views of a site from different angles to determine feasibility of construction. These photos can be sent to a number of potential contractors during the bid process. The same capability is also useful to show job progress to developers, who may not be able to visit the site on a regular basis. Finally, drones provide a means of monitoring the safety of workers at multiple sites, keeping the contractor informed of any safety issues on a real time basis, requiring a fraction of the manpower and cost of on site supervisors.
Drones also have potential in the commercial sector. For example, Wal Mart is currently utilizing drones comparable to those used in agriculture to scan warehouse inventory, checking for missing or misplaced items. Drones flying through a warehouse are able to complete an inventory in a day – a task that would take an on site warehouse crew a month. Though in its early stages, a few major companies are using drones for delivery purposes. Dominos Pizza began a delivery service in Britain, in which a drone was able to deliver two pizzas per trip. This service has the obvious advantage of avoiding traffic jams. In Philadelphia, a dry cleaning service is using drones to make emergency deliveries of laundry to customers. Though weight restrictions are a problem, they are capable of flying a freshly cleaned suit to a customer’s front door. The latest evolution is party drones, which fly over an outdoor party, playing prerecorded music.
While drones haven’t been adopted on a mass scale, they have increased the functionality of a number of key industries, breaking through the traditional barriers. From quick deliveries, to monitoring construction progress to agriculture, drones increase work efficiency and productivity, improving customer service, safety and security – with little or no manpower. According to a recent Price Waterhouse Coopers study, drone related activity provides an economic boost of more than $127 billion globally. With the relaxed FAA flight rules approved in 2016, drone operators have more flexibility from which to operate. As it becomes cheaper to develop industry-specific drones, subsidiary niche markets will emerge. A recent study indicates the use of commercial drones could add $82 billion and 100,000 jobs to the national economy by 2025 – not bad for a young industry.
After my grandson flew his newly purchased quadcopter a few weeks ago, I was stunned by the quality of video produced by its camera. During the course of this blog, we will trace the development of compact cameras, as well as their effect upon the radio control models.
The evolution of drone cameras began in 1901, when renown photographer George Lawrence conceived the idea of attaching a camera to a balloon to take photos of banquet halls and outdoor ceremonies. Lawrence developed a panoramic camera with a relatively slow shutter speed, which proved idea for area photographs. While his first balloon pictures were a success, both he and the balloon crashed, with Lawrence surviving a 200 ft. fall without injury. He then developed a camera platform using a series of kites connected by bamboo shafts to support the weight of the camera and ran a steel piano wire from the ground up to carry the electrical current that would trip the camera shutter. The photos were retrieved by parachute. This system was so successful, Lawrence used it to photograph San Francisco after the 1906 earthquake – from which he earned $ 15,000.
However, it wasn’t until the advent of digital technology in the 1970′s, which allowed photography to become more adaptable, that compact cameras became feasible. A digital camera is a hardware device, which takes pictures like a conventional camera, but stores the image to data instead of printing it to film. Most digital cameras are now capable of recording video in addition to taking photos. Perhaps the earliest precursor to digital photography occurred in 1957 in which Russell Kirsch, a pioneer of computer technology, developed an image scanning program utilizing a rotating drum to create images, the first scanned image a picture of Kirsch’s son. By 1969 a charge-coupled semiconductor was created by ATT Bell Labs, in which a semiconductor was capable of gathering data from photoelectric sensors, then transferring that charge to a second storage capacitor. Analog data could be transferred from a light sensitive chip, which could be converted into a digital grid, producing an image. In 1974 Bell Laboratories developed a charge transfer system, which could store and transfer charge carriers containing pixel data in serial order. This system was further refined by Bell in 1978, in which a charge transfer imaging device was produced using solid state technologies. This system was both more cost-effective, as well as preventing smearing aberrations created by similar image capture devices.
In 1973 Eastman Kodak took a gamble and hired Steve Sasson, a young electrical engineer. Sasson was one of a small cadre of electrical engineers employed by Kodak, a company well known for its chemical and mechanical engineering projects. Sasson was directed to capitalize on the capabilities of a charge-coupled device created by Fairchild Semiconductor, which could transmit and store images of 100 by 100 pixels. In 1975 Sasson completed a prototype camera incorporating a charge-coupled device, adapting a lens from an eight millimeter film camera, an analog -to-digital converter from a Motorola digital voltmeter, and a digital-data cassette recorder for storing image data. With this combination, Sasson and other Kodak technicians could capture an image and record it to a cassette in a mere 23 seconds.
By 1990 several companies began to enter the digital photography market, creating a new segment for consumer cameras. The first digital camera ready for sale in the US market was the Dycam Model 1, which came out the same year. The Model 1 was capable of recording images at a maximum resolution of 376 pixels by 240 pixels. Two developments in the 1990′s further enhanced the marketability of digital cameras. The first was a codec, utilized for image compression, the precursor to the JPEG image file format of today. This system exponentially increased the storage capacity of digital cameras over prior magnetic tape and floppy disc storage systems. By the mid 1990′s Apple began to market the Quick Take 100, the most widely marketed digital camera in the United States. The Quick Take had a maximum resolution of 640 by 480 pixels and could store up to 24 images in 24 bit color. In 1995 Casio released the QV-10, the first consumer digital camera to include a to include a liquid crystal display (LCD) screen, which quickly allowed camera owners to review newly photographed images. Other developments in the 1990′s included a pocketable imaging device with an LCD screen capable of displaying images from a camera storage device, as well as a single- lens digital reflex camera, which could reproduce camera images in 35mm film quality. By the end of the decade, digital cameras had a resolution of 2,000 pixels by 2,000 pixels.
In the early 2000′s a merging of digital camera and lithium polymer battery technologies took place. In the latter case, the flexible polymer battery began to deliver near gas engine performance with the attributes of less weight and volume on the rc model frame. Digital cameras were now both lightweight and efficient, capable of both still photos and video covering a relatively wide area. By 2010 a number of drones and smaller quadcopters carried flash drive units, which could be inserted into the rc model camera to record flight video. Once on the ground, the rc pilot would then insert the drive unit into the USB connection of a personal computer, playing the video of the quadcopter flight on the computer monitor screen – a far cry from pulling piano wire to trip a camera shutter.
Within the past fifteen years there has been a revolution in both types and capabilities of rc model batteries. During this blog, we will attempt to analyze current types of batteries on the market and their best uses.
The NICAD or nickel cadium battery was the first battery in use for rc models and has served the radio control pilot for decades. NICAD batteries were first developed in Sweden, with the first practical batteries produced in 1906. Nickel cadium batteries were first produced in the United States in 1946 and radio control enthusiasts began to use them in the 1950s. They were popular because they had a higher power to weight ratio than gasoline engines in use on rc models of the time, although they had a limited endurance. Nickel cadium batteries offer the advantages of a low internal charge resistance, producing high currents. These batteries also have a relatively low self discharge (retaining its charge while stored) and their performance is not drastically affected by fluctuations in temperature. Some of the disadvantages of NICADS are they are both heavier and bulkier than newer technology batteries, are not environmentally friendly, as well as gradually losing their charge capacity if not periodically drained and recharged. Despite the availability of newer battery types, some rc hobbyists continue to use them when extremely fast performance Is required.
Nickel-metal hydride (NIMH) batteries are chemically similar to nickel cadium cells while utilizing a hydrogen-absorbing alloy instead of cadium. An NIMH battery has two to three times the capacity of an NICAD battery. Nickel-metal hydride batteries were first tested in 1967 using a lanthanum alloy, which was both expensive to produce in addition to having a limited charge life. After extensive testing in the 1970s and 1980s a practical battery using a mischmetal alloy was developed in 1987. NIMH batteries have the advantages of a higher capacity than NICAD batteries, in addition to retaining more of their charge capacity over time and being more environmentally friendly. Nickel-hydride batteries can lose their charge faster than other types, and require an outside charger for peak efficiency, unlike NICAD batteries. NIMH batteries are lighter than nickel-cadium units and more subject to breakage with imported batteries often running below stated capacity. NIMH batteries are most often used in transmitter and receiver packs of rc model units.
A lithium polymer or LIPO battery is a rechargeable battery of lithium-ion in a soft pouch type structure, unlike NICAD or NIMH batteries. The cells of the LIPO batteries contain liquid electrolytes with the polymer barriers used to separate the battery cells. The electrolytes may also be gelled by a polymer additive to conduct current. Lithium polymer batteries have been in use since the mid 1990s and have a very high power to weight ratio. They retain much of their charge in storage and are resistant to temperature changes. However, they are sensitive to overcharging and rapidly discharging, posing a fire hazard due to the polymer chemicals. RC models such as quadcopters now routinely use LIPO batteries attaining performance and endurance greater than many gas powered units. There are two recent variations of LIPO technology which overcome some of the basic LIPO battery limitations. The LifePO4 is more resistant to overcharging and discharging than the basic LIPO battery, as well as being less flammable . The LifePO4 has an ever higher power to weight ratio than a regular lithium polymer battery. The A123 battery, a modified LifePO4 utilizing nano technology, is able to deliver current at an even faster rate than the LifePO4 with greater safety. Such batteries give the rc pilot revolutionary advantages of weight, performance and safety.
My grandson and I were looking at pictures of rc helicopters online and we saw the picture of a strange looking craft. Unlike a conventional helicopter, which has a large main rotor centered above the cabin with a smaller rotor mounted at the tail, this unit had its rotors mounted at the end of four bars, extending from the center. The helicopter in question is called a quadcopter and is one of the fastest growing types of rc models. During the course of this blog, we will trace the development of quadcopters, as well as some of the reasons for their current popularity.
While manned quadcopters were first tested in the 1920s, rc model applications began in Japan in the early 1990s. Although the tests were successful, the quad units were never marketed internationally. During the early phases of the wars in Iraq and Afghanistan, the military was in need of a means of conducting reconnaissance in support of ground operations. These missions were first conducted by small rc planes mounted with cameras. While the rc aircraft were effective camera platforms, the need for a hover capability became apparent. Experiments were conducted with a number of designs, with a practical rc quadcopter developed by the late 2000s.
Radio control quadcopters have only recently come into use due to the processing power required to not only keep all four rotors turning, but at a synchronized speed. RC quadcopters represent the merging of several technologies. The first being a solid state gyro system from which to steer the craft, followed by high capacity batteries to provide increased flight endurance, along with digital camera technology for video and still photo observation. Many of them are constructed of a carbon-fiber material, similar to that on the Boeing 787 Dreamliner. These copters are quite durable, with some test units surviving crashes in excess of 100 ft.
The quadcopter is a popular rc vehicle for a number of reasons. To begin with, it has fewer moving parts than a conventional rc helicopter and is easier to fly. While a conventional rc copter may need pitch adjustments to its main rotor while in flight, the quadcopter runs via four flat-bladed rotors. To control the quad in flight is merely a matter of controlling the power to each of the rotors. Quadcopters are also relatively safe from wind conditions due to their balanced structure. Quad units are simplier to build and repair than conventional rc helos. A number of quads are equipped with multi-colored led lights, enabling night flights. With current battery and engine technology, many quadcopters can fly in excess of 30 min. Finally, the quads are built around the ever present camera, an afterthought on a conventional rc copter.
In 2010, a radio controlled aircraft collided with a small private plane during a charity airshow at a Colorado airport. While there was no visual damage to the private plane, the incident reflected a growing trend in rc aviation – the use of FPV planes. During the course of this blog, we will discuss the current problems surrounding their use.
We first need to define an FPV plane. An FPV (First Person View) plane is a radio controlled model aircraft, which utilizes a small onboard video camera and transmitter sending imagery to a ground receiving unit in the form of video goggles or a portable LCD screen. The view from such flights is the same as a pilot would have from the plane. Because of this, the rc pilot on the ground need not maintain line of sight (LOS) contact with the model, limited only by the reach of the radio signal and the power supply of the aircraft. While a number of rc aircraft are built with FPV capability, kits are available to install video cameras on virtually any rc plane. The rc pilot using goggles or head tracking gear usually has an exciting flight experience.
The capability of FPV aircraft to fly beyond visual contact range (some have a radius in excess of thirty miles), as well as an altitude ceiling above 3,000 ft., may sometimes cause problems when the pilot loses the video signal. For example, private planes often make their landing approaches at altitudes within the envelope of the FPV model. A loss of signal at the wrong time could result in a collision between the two craft and pilot error due to the distraction. Collisions with communications towers, power lines and other ground obstacles pose an equal threat. Though there are currently no laws or regulations governing control of FPV planes, the Academy of Model Aeronautics has proposed several guidelines to make FPV flight safer.
The first is the use of a buddy box system, in which two pilots, one in sight of the rc and the other monitoring the flight by video are able to direct the plane using independent flight controls. Another proposal requires an FPV pilot to fly their craft within line of sight at an altitude of no higher than 400 ft. Some models utilize autopilots, which automatically fly the plane back to its controller upon loss of video power. For all of the safety concerns, there has never been a recorded incident of an FPV plane causing major property damage or injuries, due to the majority of FPV models being constructed of styrofoam, which is lighter and less rigid.