Friday

Do You Speak Quadcopter?

When we hear folk talking about consumer drones, they are often referring to quadcopters of various designs. In this post, I give an overview and explain some of the terms you may see if you decide to delve into this hobby (or are purchasing one as a gift).

What IS a quadcopter ("quad" for short)? At it's heart, a quadcopter is a lightweight remote-controlled four-propeller flying machine, almost always using electric motors. Quadcopters are usually not aerodynamic in any meaningful sense; they can't glide and need sustained power to stay aloft, like a helicopter. 


Quads have two sets of contra-rotating propellers, usually mounted on arms extending from the body of the machine. Two props will rotate clockwise, and two counter-clockwise; this is to prevent the aircraft spinning under the torque produced while providing lift.

These aircraft have a full range of motion, they can fly up/down, forward/back, left/right and they can also spin ("yaw") clockwise and counter-clockwise. The radio control features vary in complexity and quality, but at a minimum would allow the pilot to take off, fly and land the quadcopter around an area within a hundred meters or so of the controller (around 300 feet).

The radio controller (more correctly, the "transmitter") in it's most basic form (below) will typically have two moveable "sticks" or "thumb pads", like a video game controller. The left traditionally controls the motor speed (up/down) and the yaw (left right), which the right controls forward/back/move left/move right.

the basic controller that comes with the Hubsan shown above
The requirements of flying "a box with propellers on each corner" demands some electronic intervention to keep things manageable. Even the most inexpensive toy quads have some kind of internal gyroscope system "talking to" an onboard computer to allow it to respond appropriately to controls issued by the "pilot".
 
Although the quad will be seen to tilt and bank as it flies, it's "natural" (programmed) orientation is to remain level with the horizon. In this post, I am discussing machines you would purchase already constructed, I am not getting into the true hobby side of things where all kinds of home-made exotica awaits - and where you need to delve into flight controllers, carbon fiber frames and the like.

Learner or toy quads are typically physically small (many will sit comfortably in the palm of one's hand like my little Hubsan X4-107L shown above) and usually cost less than $100 "ready-to-fly" - many less than $50.

Ready-to-fly or "RTF" means the quadcopter comes with a controller and, other than providing batteries for the controller/transmitter and charging up the quad battery, they are ready to use. When one moves up the price range, you may also see "RTB" (Ready-to-bind), meaning you provide your own controller.

Moving up, still in the "toy" grade, you will find cameras and slightly larger quads. When one gets into the hundreds of dollar range, we start to see "hobby" grade drones, with larger batteries, more powerful brushless motors, GPS, more sophisticated transmitters and other niceties. 

The batteries used in the quads themselves are usually replaceable Lithium Polymer (LiPo) rechargables (so you may keep an extra battery on hand if needed). Flight times tend to be brief, in the order of ten minutes or less.

Larger batteries can give more flight time, but add weight and may hamper flight characteristics.  Flight times longer than 20 minutes are usually the province of professional quads.

Brushless motors are found in the more expensive quads, and can give better performance and longer life than "brushed" motors. 

Cameras vary enormously in quality, not just as far as the camera itself, but in the way it is mounted and what it is being used for. A typical sub $100 quad with a camera will record to an SD card and give a few minutes of pretty grainy video (still fun, but not very high quality). 

The beautiful, sweeping videos one sees on TV or YouTube are typically taken by a GoPro or similar quality camera using a "gimbal" mount, a mechanical apparatus that stabilizes the camera (and the images) and all but eliminates any vibration from the drone itself. 

Without a gimbal or some other kind of specialized camera mount, you will almost aways see some kind of "jello" effect (wobbly or jerky video), even with a good quality camera.

If you look at the different models of quad for beginners and intermediate flyers, you will see a pretty wide range of features, so it helps if you have some idea of what you are looking for. 

Note that almost all quads can be used in two or more "modes"; a beginner mode, where the controls are somewhat less responsive and one or more other modes, which make the quad more responsive, faster and/or more aerobatic.

These are only my broad classifications, but should be helpful: 

A small beginner quad - you can learn on these indoors or out, and when (not if) you crash, it will either just bounce, or you can replace a broken prop, etc. Most quads will come with at least one set of spare props. The basic skills learned here can transfer to a larger, more sophisticated quads.

These may be referred to as nano or micro quads, with the nano ones being the smaller size - they can be really tiny. Quads in general may also be referred to as 100mm, 150mm size, and so on. The measurement refers to the distance between diagonally opposite motors.

A medium size beginner quad - which will probably handle better outside (at least with light breezes). Quads do not handle strong winds well; nor would most other RC flyers like airplanes, gliders and helicopters.

A beginner quad of either size, with a camera - which allows you to take "snapshots" and/or short movies onto a removeable SD card mounted in the quad. Don't expect breathtaking videos, though, even if the camera is described as "HD".

An intermediate quad - may also have brushless motors and will be faster and possible more agile (and potentially more demanding to fly in the non-beginner mode). 

Depending on price, an intermediate quad may also bring features like GPS and "altitude hold", and probably a more sophisticated controller. GPS allows the quad to "know" where it is, and you can usually invoke a "return to home" function if you get disorientated or visually lose site of the quad during flight. It's not infallible, but can be a nice feature.

Altitude hold is just what the term implies; you can leave the throttle alone and the quad will remain at the current (or at a preset) altitude. 

Speaking of altitude, FAA regulations currently require that you cannot fly above a height of 400 feet (about 120 meters), nor fly the quad out of your sight; so-called "line of sight" flying. If the flying weight of the quad exceeds 250 grams (a little more than half a pound), you also must register it with the FAA (registration is currently under review/appeal). 

Some intermediate quads may also provide FPV via an onboard camera. FPV, or "First Person View" puts you in the pilot's seat and allows you to see a real-time display as if you were a tiny pilot sitting in the quad, which can be pretty breathtaking to observe.

The actual FPV display can be viewed in different ways: 

1 - On a small screen that is part of the controller.

2 - On a smart phone or tablet using an App that connects to the quad via WiFi (there is usually a slight delay using this method, which may or may not be important, depending on what the quad is being used for).

3 - Via a headset/googles with small screens that give a more immersive view - this is the method used by "racers". The video signal is directly transmitted to the headset from the quad camera.

Camera platform quads - such as the DJI Phantom series are usually larger (requiring registration with the FAA) and can be quite expensive, typically $500 and upward - more of an investment than a plaything. They may or may not come with a camera, although they typically will have a gimbal mount for the camera as previously mentioned, or offer the ability to easily install a gimbal.

They will also feature GPS and altitude hold, as well as other features allowing them to follow a selected object or person, for example - all niceties to make to make the video or photography process easier.

While these can also be quite "easy" to fly (a quad is a quad is a quad), the additional features obviously add complexity and cost. These are definitely not toys.

Believe it or not, I probably left out quite a few things, but there are a LOT of resources on YouTube and other places, such as Flyin' Ryan, RC Saylors and FliteTest. You can seen many reviews and flight tests of all kinds of quads and other flyers, as well as tutorials and other material for those interested in "rolling their own".


No comments :