What is a Drone?
Quadcopters. Batteries, Autopilots and Cameras
Most people have a pretty good idea of what a drone looks like, but have you ever wondered why it looks that way? The small vehicles most people think of when they hear the word drone is technically called a quadcopter, because it is a helicopter design that uses four propellers for locomotion. There are other copter designs that use different numbers of propellers and control methods, but small drones are usually quadcopters because they are simple and inherently balanced. A spinning propeller will exert an equal and opposite reaction against the airframe, at least according to Sir Isac Newton. To counteract that force another propeller is added spinning in the opposite direction. This is how the Chinook helicopter flys, although the propellers on the Chinook have a complicated mechanical system for controlling the pitch angle (twist) of the propellers. Because the goal of a quadcopter is to keep the mechanism simple, adding two more propellers and varying the rotational speed on each propeller through software can achieve the same result.
Quadcopters were first demonstrated in the 1930s, using very large aircraft that could hold a human pilot. However the design was put on the shelf due to the complicated controls and need for constant corrections. But in the early 2000s the development of cell phones and cameras led to introduction of small microchips that could recognize their spacial orentation and adjust screens and pictures to the way the user was holding it, either portrait or landscape. The rise of GPS navigators that included digital compasses to align maps and the incorporation of those chips into mobile phones were another component that could be borrowed, along with more powerful microprocessors that were designed for real-time control.
And then there’s the cordless power tool. The drone borrows three key items from power tools: motors, speed controler microchips and batteries. Adapting these components to work with inputs from a microprocessor was key to providing stable flight. Soon after hobbyists began modifying power tool parts and eventually they were able to construct their own specialized components that were more compact, lighter, and reacted more quickly, but the basic tech is the same.
When all these parts come together, along with a lot of software, you get a quadcopter. Pretty quickly after people started building and flying them someone came up with an idea: Why not mount one of those new GoPro cameras (another benefactor of mobile phone technology) on the front? Once this began people who were’t model aviationists realized that they could be used for budget aerial photography. Before quadcopters aerial photography and cinematography was an extremely expensive proposition, only for Hollywood or top 50 television markets. Much of the costs were due to having to carry the “200 lb guerrilla” and the heavy cameras. But with a GoPro sized camera, even with the inefficiency of quadcopters, the skys were opened up. As manufacturers began to integrate camers into the aircraft they also added remote control of the camera and video feeds using WiFi connections.
Inefficent design (but good enough)
Take a look at the picture at the top of this page. I’ve annotated it to show the major components of a drone. Each motor is pushed out to a corner to maximize propeller area and to add stability (imagine a chair, each leg pushed out as far as practical and as wide as necessary). The props are designed to generate the most lift from the motors while not overloading them. The internals of the body contain the battery pack and autopilot. In fact, the largest and heaviest component of any quadcopter is the battery! Finally, on the front of the body there’s the camera on its gimbal. This is known as the payload. The camera itself only weighs a few grams. Imagine, all that hardware just to carry a payload the weight of this morning’s coffee pod.
The sky has opened
But then again, without the camera what’s the point? Sure flying a quadcopter is fun but probably not all that useful. Aerial photography has always been a great way to gain perspective and insight, but has been out of reach for most. With remotely controlled quadcopters the cost of flight has dropped to a fraction of traditional flight. And thanks to the increases in processing power, pilot assisted flight requires much less training, with more a focus on airspace rules, payload control and flight management, and less emphasis on the mechanics of flight.
And now that more people have discovered aerial photography, the uses for quadcopters are expanding. Some of the new uses are quite old, but were difficult in practice. Some take advantage of the revolution in inexpensive storage and add robotics to quickly create extremely detailed maps and “digital twins” of the real world. Still others are using quadcopters for documenting changes in the enviroment, from construction sites to crop and vegetation growth, to tracking use of stored materials.
These new uses just weren’t practical before quadcopters. Every day people are finding more uses for these incredible tools.
Very informative!!