Author: Tronserve admin
Wednesday 4th August 2021 02:15 PM
Quadcopter Capabilities Take Flight
To anyone who's ever flown a quadcopter, dictionary definitions of a "drone" just don't do them justice, especially when the standard definition of the word is "a male bee…which does no work but can fertilize a queen." The recent addition of "unmanned aircraft or ship guided by remote control or onboard computers" is too sparse, so below we offer some positive linguistic ballast to the current dreary characterizations:
A drone is an unmanned vehicle that performs tasks while either traveling from its launch point to a specified destination and back or loitering in a designated area, with or without human intervention while avoiding collisions with other objects. When operating autonomously such a vehicle is called an Unmanned Autonomous Vehicle (UAV) or Unmanned Autonomous System (UAS). These unusual combinations of aeronautic and electronic technology are made possible by advances and cost reductions in sensors, processors, communications, and other technologies, are taking the world. Together, all this low-cost technical wizardry makes it possible for virtually anyone to own one, even if it is just a toy commonly offered at mall kiosks in the holiday season.
There are several quadcopter solutions on the Mouser Electronics website. Infineon has a portfolio of products meant for multicopters as shown on the Infineon multicopter solutions page, Cypress Semiconductor has a complete quadcopter solution that was created at Maker Faire, and the Intel Aero platform for UAVs includes a Aero Ready-to-Fly Drone, Aero Compute Board, Vision Accessory Kit and Enclosure Kit. Quadcopter kits can help students to better understand physics, control systems, programming, mathematics, and engineering. Quadcopters, or drones, are not your father's radio controlled (RC) Cessna.
Figure 1: Multicopter system block diagram by Infineon. (Source: Infineon)
The drone business is poised to quickly reach new heights according to Grand View Research (Figure 2) and in 2015 manufacturers of commercial drones racked up global sales of $356 million (including multi-rotor, nano, hybrid, fixed-wing, and other types) with projections of a tenfold increase to $1 billion by 2022.
Figure 2: The drone market through 2022. (Source: Grand View Research.)
Some might consider quadcopters to be a mere addendum to the "RC" market that today includes replicas of the Hindenburg. In fact, radio-control was first demonstrated in the late 1800s by Nicola Tesla, who demonstrated an RC boat in 1898. Tesla was followed by his associate and 1963 IEEE Medal of Honor winner John Hays Hammond Jr., the "father of remote-control," who among more than 400 other things, invented pitch propellers and single-dial radio tuning.
Figure 3: Tesla demonstrated this radio-controlled boat in 1898 for which he was awarded a patent. (Source: Nikola Tesla, 1898 - Nikola Tesla Museum, Belgrad.)
RC vehicles have over the years been powered by rubber bands, gasoline, electric motors, "nitro" glow fuel consisting of methanol, castor oil, and nitromethane (the latter also powers dragsters), and rocket engines. They range in price from a few hundred dollars to tens of thousands of dollars for huge homebrew RC aircraft.
The supremely nimble capabilities of quadcopters along with their relatively low cost are making quadcopters the go-to aircraft for dozens of applications ranging from simply taking high-resolution photos and video from above for personal use, to photojournalism and filmmaking, search and rescue, monitoring utilities, border patrol, surveying, law enforcement and crowd monitoring, wildlife and land management (including counting wildlife and detecting forest fires, illegal hunting, and many more applications. Drones have been used to film the 2014 Winter Olympics, and the United Parcel Service (UPS) recently completed tests using a 42-inch, eight-rotor quadcopter to simulate delivery of medical supplies.1 DHL Express earlier conducted similar tests for the same purpose.
Last but far from least is Amazon Prime Air, the company's proposed package delivery system whose goal is to deliver packages up to 55 pounds within 30 minutes. Amazon may or may not be able to make this a reality, but one cannot underestimate this company, which confidently states that "it looks like science fiction, but it's real. One day, seeing Prime Air vehicles will be as normal as seeing mail trucks on the road." 2
The Quadcopter Defined
A quadcopter is considerably more complex than four sets of electric-motor-powered rotors operated by remote control. A typical First Person View (FPV)-type quadcopter allows the "pilot" to view real-time images from the drone's camera on a video display, smartphone, or with goggles. A hand-held remote unit controls all flight functions as well as others, depending on what sensors it carries. The control unit contains a transceiver operating on up to nine channels within the unlicensed Industrial Scientific and Medical (ISM) bands at 2450MHz and 5.8GHz and in some cases Wi-Fi. One frequency, usually 2450MHz, is used for control and the higher frequency for video transmission. Operating the controls sends a signal to drone's receiver and then to the drone's control board, which commands the motors to spin either clockwise or counterclockwise and at speeds that alter the flight direction of the drone.
Flying any aircraft requires the ability to balance its weight by generating lift and balance moments around its center of gravity, which is accomplished by creating opposite moments. To understand how quadcopters work, see Figure 5. In a quadcopter, both lift and balance are accomplished by the four rotors, the most difficult challenge being generating the moments required to stabilize it while simultaneously producing control forces that allow it to move.
Figure 5: How rotors allow drones to fly. (Source: Barry Manz.)
Each quadcopter rotor produces both thrust and torque as well as a drag force opposite to the vehicle's direction of flight. When all rotors spin at the same velocity with two rotors spinning clockwise and two rotors spinning counterclockwise (left in Figure 5), the aircraft remains in place while providing lift for maintaining altitude. When two rotors deliver more thrust and two less, the aircraft turns (center diagram.) Finally, to induce pitch and roll, one rotor gets more thrust, two get much less, and the remaining rotor gets the least (far right, Figure 5.) In this way, quadcopters, unlike helicopters, require no tail rotor, a significant benefit.
Quadcopters can achieve greater stability by using two sets of rotors in what's called a coaxial configuration, with one set of rotors mounted above the other on a concentric shaft with the same axis of rotation but spinning in the opposite direction. This approach, which is used on some commercial and military helicopters, is also available on some of the most expensive commercial and consumer quadcopters. However, like helicopters (but not fixed-wing aircraft), quadcopters have no inherent aerodynamic stability, so they need an onboard computer to fly, without which they fall like a rock. They also need a battery-operated power supply, rotor speed controllers, and software, and to be fully autonomous they have to combine information from their onboard three-axis gyroscope, magnetometer, and accelerometer with data from GPS and a barometer; all to determine orientation and location.
All of the resulting data, as well as inputs from sensors (including cameras) must also be processed, transmitted, and received using an onboard radio transceiver and antennas. This requires prodigious amounts of processing power, high-speed memory, and multiple forms of connectivity in a very small package. Fortunately, all this is currently achievable.
Not surprisingly, the quadcopter DIY community is growing rapidly, and numerous websites can help in building a quadcopter either from scratch or a semi-assembled kit. The community builds on open-source hardware and software such as the Beagleboard, Orocos-Robot Operating System, and DDS-ROS 2.0. A typical "flight stack" consists of firmware such as ArduCopter-v1.px4, middleware such as Cleanflight, ArduPilot, and an operating system such as Linux or several others.
Like all hobbyist communities, drones have a large number of suppliers that give drone builders the ability to highly customize their aircraft, and hundreds of different rotors, modules, controllers, and other components are available. For the most technically astute and handy, it is possible to create a drone that can fly beyond the line of sight, miles from the pilot, using lower-frequency transceivers that have greater range. If the drone has the payload capacity and the developer is well versed in electronics, applications are limited only by the imagination. Unfortunately, one use that got U.S. national media attention was a video that shows a drone carrying a semi-automatic handgun firing live rounds when commanded by its creator, an 18-year-old engineering student named Austin Haughwout. He later posted another video of a drone with a remote-controlled flamethrower. Not surprisingly, his activities also got attention from local and federal law enforcement, who (incredibly enough) had a hard time determining if Haughwout actually violated any laws.
Situations like this conjure up nightmarish visions at the FAA and Department of Homeland Security, but regulations for commercial drone use and registration of all drones weighing over half a pound have been put into place fairly recently, and more regulation will come.
What's to Come
Even though quadcopters can already achieve astonishing feats, there's little doubt that they will achieve much more in the years ahead. For example, artificial intelligence and machine learning could allow a quadcopter to make intelligent decisions based on various types of sensor input. Although both AI and machine learning require formidable processing power, this could be provided by data centers (that is, the cloud), eliminating the need for extensive processing to be performed in the drone itself. Package delivery services are obviously immensely attractive to Amazon, UPS, FedEx, and national postal services, but the day when drones will be buzzing around neighborhoods is probably years away. One thing is sure: quadcopters are here to stay, and the potential for novel and useful applications is magnificent.