Drones: Weight is Everything
5/8/2019 | By Maker.io Staff
Drones are something of a phenomenon, hitting the commercial market in the past decade like wildfire. While drones are not new (dating back to WW2), they have definitely taken advantage of recent technological advancements. In this blog, we will learn about how weight is critical to a drone’s performance and how technology has helped!
Without a doubt, the most important capability of a drone is the ability to lift off from the ground and stay mobile in the air. For a very long time, the easiest method for achieving lift was with the use of wings. Wings can provide lift to a craft via two methods: the first involves the commonly known aerofoil (which generates lift due to high-/low-pressure air) and the second involves the angling of the wing itself so that the wing pushes against the air.
The areofoil – image courtesy Wikipedia
However, while wings (along with a propeller) can provide an efficient method for flight, they are not ideal for drones where hovering is required. Helicopters are similar to drones, in that they use a rotor shaft to generate thrust, but helicopters require a tail section with a sideward pointing rotor to prevent the vehicle from spinning. This also makes helicopters somewhat difficult to maneuver in tight spots, with the tail end needing to be carefully considered (some helicopters, such as the Chinook, don’t have a tail section but are quite long because they have two blades).
A typical helicopter configuration – image courtesy Wikipedia
This is where the drone design comes in! Drones are typically designed with four separately-controlled rotors that act like helicopter rotors (i.e., they point upwards to provide lift downwards). However, since there are four rotors spaced evenly at the edges of the drone, there are no rotational forces causing the drone to spin, and therefore there is no need for a tail section (like in a helicopter).
Typical drone configuration – image courtesy Wikipedia
While drones are commonly piloted by a user, they cannot be 100% controlled by a pilot. One of the reasons for this is that the use of four propellers (and their small size) makes them susceptible to sudden air currents, variations in motor power, and even pilot error. While a pilot can direct the drone as to where it is going and how fast it will get there, drones often require a controller that can measure its position, orientation, and acceleration to determine how best to perform that action.
For example, in the event that a small updraft causes the drone to rock unexpectedly, the drone must be able to correct for this faster than a human pilot could. Current drone technology is only possible with the advancements in technology that has reduced the weight and size of components. So, which technologies can you minimize while still maintaining performance?
Battery technology has come along way, with older technologies rapidly being replaced with Lithium-based batteries. As these batteries provide high energy densities, they can be shrunk down and reduced in weight while still providing ample power for any drone!
While working with a large 40-pin DIP microcontroller is easy, it is not something that you would want to lug around on a drone, because these microcontrollers are much heavier and larger than their SMD counterparts. This is why pre-made microcontroller modules, such as the Arduino Nano, are much more appropriate: they contain GPIO headers, use an SMD processor, and are very small and portable.
Believe it or not, but even motor technology has drastically improved with some incredibly small brushed DC motors available in the smallest sizes. Reducing the size of the motors does typically have a knock-on effect on the lifting power, but by reducing excess weight in the motor as well as other components, the overall effect of miniaturizing should allow for smaller drones with high mobility.
The chassis is one of the easiest points of attack for reducing the weight, as there are many materials and methods available for reducing weight. Frames made of metal, for example, can take advantage of aluminum with cut out holes, which can lead to significant weight reductions while retaining strength (ridged Zeppelin airships are an example of aluminum frames with large cut-outs).
Other materials that can be used include plastic (which can be easily 3D printed) and balsa wood (both easy-to-work-with materials). While materials such as polystyrene are incredibly lightweight, they are also prone to snapping, which may make them unsuitable for drones that can potentially crash.