A quadcopter, quadricopter, quadrotor or quad is a type of radio controlled and/or GPS controlled electric helicopter.
Quadcopters generally consist of a central hub from which four radial arms extend at ninety-degree intervals. The ends of each arm are equipped with an upward- or downward-facing outrunner motor driving standard and reverse rotation model airplane propellers or quadcopter-specific propellers.
The result is an extremely stable yet nimble model aircraft with high payload capability. This makes the quadcopter an excellent base for aerial photography, FPV flight or as an autonomous flying robot/unmanned aerial vehicle via GPS control.
Similar to the quadcopter is the Y-copter or tricopter. In this configuration, there are three arms radiating at 120-degree intervals with one or possibly two motors per arm. A hexcopter or hexacopter has six radials at 60-degree intervals. The terms multicopter and multirotor can apply to any helicopter of this basic type.
Each rotor produces both thrust and torque, with rotors one and three rotating clockwise and rotors two and four counterclockwise. This makes the net aerodynamic torque and angular acceleration about the yaw axis exactly zero in much the same manner as a coaxial helicopter. Directional flight is induced by mismatching the balance in aerodynamic torques, i.e., by offsetting the equal thrust of the motors at hover. This eliminates the need for linkages of any kind in a model quadcopter.
While the lack of linkages makes a model quadcopter among the simplest of flying models from a mechanical standpoint, the electronics necessary to fly a quadcopter are often extremely sophisticated. Many rely on an inertial measurement unit combining a gyroscope with an accelerometer, barometer and magnetometer. This may be tied into a standard R/C system, a programmable GPS system, a first-person-view system or a combination of any or all of the above.
MultiWii stabilization systems based on the software used to control the gyroscopes and accelerometers found in the control wands of the Nintendo Wii video game system are both effective and popular.
Popular too are discrete frames and components for those wishing to build their own custom quadcopter. Frames such as the DJI Flamewheel are available for use with the builder's choice of components; plans are available online to build one's own frame from scratch with materials ranging from those found in hardware stores to parts made on 3D printers. Hong Kong-based online hobby retailer HobbyKing has taken a lead in affordably priced discrete components. Software designers known under the screen names of "SimonK" and "Timecop" have developed their own quadcopter-specific programming codes for HobbyKing on their ESCs and control boards respectively. ESCs reflashed with open source SimonK software have become extremely popular, leading HobbyKing to develop their own quadcopter-specific ESC with SimonK software, the Afro.
Among the best-known RTF and ARF quadcopters are manufactured by Taiwanese model manufacturer Gaui. Another quadcopter, the DJI Phantom, incorporates highly sophisticated GPS and R/C systems into a single, ready-to-fly unit.
- Several nano-sized quadcopters were successfully programmed and flown in a series of computer controlled formations by Alex Kushleyev and Daniel Mellinger, graduates of the University of Pennsylvania School of Engineering and Applied Science and the founders of KMel Robotics, builders of the nanocopters. On February 29, 2012, Kushleyev, Mellinger and Deputy Dean for Education Vijay Kumar from the University of Pennsylvania's General Robotics, Automation, Sensing and Perception (GRASP) Laboratory introduced a video showcasing a set of KMel nano quadcopters programmed to play both standard and specially built musical instruments at the TED2012 conference in Long Beach, California. The quadcopters, each autonomously programmed, played the "James Bond Theme" on a modified electronic keyboard, a ride cymbal, maracas, a tom-tom and a "guitar" made from a modified couch frame and "strummed" by the quadcopters by stiff wires mounted beneath them. A pre-tuned electric guitar provided the closing chord with a pair of quadcopters strumming the guitar via those same wires. By March 3, the YouTube video produced at the university and uploaded on February 28 had surpassed 1.1 million hits; the original video showing the quadcopters in formation had surpassed more than 5.5 million hits by that same date.
- The MIT Aerospace Control Lab is doing similar work with variable pitch autonomous quadcopters. Such quadrotors have quicker, more accurate transition to hover from fast maneuvers.
- The 2010 introduction of the Parrot AR.Drone by French company Parrot SA combines FPV, video, combat and standard flight functions controllable via an Android smartphone or tablet. It is marketed as the "world's first flying video game."
- The Blade mQX, the world's first hobby grade RTF R/C micro quadcopter introduced in January 2012, relies on AS3X technology introduced by Horizon Hobby in October 2011. AS3X is a three-axis gyroscopic stabilization system which automatically stabilizes micro models which in turn causes them to perform like far larger models, even in wind. The motherboard of the mQX allows it to be flown in "X" configuration (two motors fore, two aft) or "plus sign" configuration (one motor both fore and aft; one motor per side).
- On October 21, 2011, the first manned R/C multicopter flight was achieved by German aviation company e-volo with their experimental VC-1. The pilot was e-volo's Thomas Senkel who is shown flying the VC-1 in the photo. The aircraft was the result of more than a year of development of both the airframe and flight systems.
- In March 2012, Dutch artist Bart Jansen combined the taxidermied remains of his tabby cat Orville - named for aviation pioneer Orville Wright - with a LotusRC T580 quadcopter frame. The result was the Orvillecopter, which Jansen said was a tribute to his longtime pet accidently killed by a car. Orville was particularly fond of birds and Jansen thought it would be appropriate to send him among them. The Orvillecopter was scheduled to be exhibited at the 2012 KunstRAI Art Festival in Amsterdam where it proved to be somewhat underpowered. Jansen and R/C helicopter pilot Arjen Beltman updated the internal electronics with HobbyKing units; plans were in place to fit it with larger motors and propellers in time to fly the artwork on what would have been Orville's birthday.
- A February 22, 2013 story on robotics research site Robohub.com told of a master's thesis project involving autonomous quadcopters by ETH Zurich university student Dario Brescianini. Brescianini developed an algorithm which allows two quadcopters to literally play catch with one another using an inverted pendulum. In this case, the inverted pendulum is a balanced stick with a simple shock absorber consisting of a flour-filled latex balloon at either end.
- In April, 2013, 40-year-old web developer Jason Muscat proposed to girlfriend Christina Dam in San Francisco, California's Alamo Square with the aid of an autonomous hexcopter. Muscat preprogrammed the hexcopter to deliver the engagement ring to his location as he "popped the question."
- On July 27, 2013, Bart Jansen and Arjen Beltman performed the first test flights of a follow-up to the Orvillecopter. Dubbed the "OstrichCopter," the creation is based on a farm-raised ostrich which died a natural death and was donated to Jansen. The idea was to give an otherwise flightless bird the power of flight despite the post-mortem nature of the subject. The work is considerably larger than the Orvillecopter and may well be one of the largest quadcopters in the world with a flying weight of 46 pounds (21kg).
- November 2013 saw the introduction of the world's smallest production quadcopter to date. Released as both the Estes Proto X and Hubsan X4, the four-channel model measures only 1.8" (45mm) across, roughly the size of an ordinary saltine cracker.
- Also in November 2013, internet mail order retailer Amazon.com announced a plan to deliver packages directly to consumers via autonomously controlled multirotors. Dubbed "Prime Air," the system is still in the experimental stages and will not be ready for several years pending further development of the technology and regulatory legislation by the US Federal Aviation Administration.
- British aerial platform company Flyonix did a fun but ultimately unsuccessful experiment. In December 2013, they constructed a full-sized model from foam sheeting of the TARDIS time travel vessel from the BBC-TV series Doctor Who and attempted to fly it via one of their hexacopter aerial platforms. The creation flew, but not well, ultimately flipping upside down and crashing in a field.
- During the 12th Annual Auto Expo held February 2014 in Delhi, India, French automobile manufacturer Renault displayed a concept car with a roof-launched, color coordinated quadcopter drone. The Kwid, if produced, would be aimed at younger, tech-savvy buyers who could use the drone as a means of reporting traffic problems to the driver or even more fun uses such as "selfie" photos of the driver and passengers while the vehicle is in motion.
- Video of the "James Bond Theme" quadcopters at the University of Pennsylvania's official YouTube site
- Video of the autonomous MIT variable pitch quadcopters at MIT Aerospace Control Lab's official YouTube site
- New multirotor discussion forums at RCGroups.com
- Gaui 330-X quadcopter build thread at RCGroups.com
- Detailed article on the development and production of the quadcopter at Wikipedia.org
- Official product page of the Blade mQX
- Discussion and YouTube link about the "nanocopter swarm" at Crackroll.com
- KMel Robotics home page
- Information page for the Parrot AR.Drone
- Story about the "Orvillecopter" at Dailymail.co.uk
- e-volo VC1 home page
- MultiWii home page
- Link to the throwing and catching quadcopters at Robohub.org
- NBC News story about the hexcopter-aided marriage proposal
- Review and discussion of the HobbyKing Afro ESC with SimonK software at RCGroups.com
- Video of the original test flight of the OstrichCopter at Youtube.com
- Second OstrichCopter test flight on Youtube.com
- Official home page of the experimental Amazon.com Prime Air service
- Flyonix home page with links to the build and videos of the full-scale TARDIS
- Report on the Renault Kwid concept car at msn.com
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