Drones have become extremely useful for disaster management. They reduce the time required to locate victims and the time required for subsequent intervention by searching a large area within a short period of time. While drones are being used to monitor traffic and weather, firefighting, surveillance, and delivery, a graduate student from TU Delft’s Faculty of Aerospace Engineering has built smart mini-drones that can be used to detect a gas leak.
This drone, designed by Bart Duisterhof, addresses one of the critical aspects of most industrial drones available in the market. These drones, also sometimes referred to as multi-rotor drones, can be large and hence are not ideal for situations such as detecting a gas leak. Duisterhof is addressing this issue with indigenously developed mini-drones that are smaller and lighter than normal drones but still capable of performing the same tasks.
Smart mini-drones to detect gas leak
For his master’s thesis, Duisterhof designed smart mini-drones that can independently detect gas leaks. The idea around these smart mini-drones stems from the fact that there is a need for small and low-cost drones for operations in complex and small spaces.
“Such spaces are often inaccessible or poorly accessible,” says Bart Duisterhof. “There’s also a risk of explosion. You rather don’t send people into such an area. Instead, you can use drones.”
While most people might suggest using a normal drone, their size becomes too big for small spaces. While normal drones might enter an area, they may fail to optimally navigate tight spaces and crash, thereby rendering them incapable of finding the leak. To mitigate this issue, Duisterhof decided to develop several small drones that spread around the room.
“As soon as one of the drones detects gas, it communicates with the other drones, and together they locate the leak. So with several drones, you trace a leak more quickly. Another advantage of working with small, low-cost drones is that it is less of a problem if one or two fail or crash,” he says.
Challenging the status quo
Duisterhof explains that there has been an earlier study about the use of small drones to detect gas leaks. This study concluded that it might not work and Duisterhof wanted to challenge this notion. He found out that not every gas spreads equally well and is therefore difficult to detect. In his own tests, Duisterhof found that the drone was easily able to detect the gas.
The graduate student from TU Delft, the oldest and largest technical university in the Netherlands, says that building small drones to detect gas leaks was a risk that turned out to be rewarding. “The great thing about a university is that you have the space to do that. I also chose something that’s not directly linked to my degree programme. I taught myself a lot of things, including how to make algorithms. It shows that it’s sometimes possible to think outside the box in your degree programme. That way, you can reach solutions you might not otherwise have thought of,” he explains in a blog.
Duisterhof not only challenged the status quo but also found a way to best optimise the chip powering the drone. Since the order of business of these smart mini-drones is to detect gas leaks, they need to be able to navigate well. While most industrial drones rely on cameras or large lasers to navigate a zone, the same cannot be used here because of their weight and complexity around processing the data.
“Processing that data takes up a lot of space on the chip. So does the mapping software that uses complex optimisation to determine the best route. If you want to limit the weight of the drone, you can’t take a powerful computer with you,” he explains.
With regular navigation methods not working for his drone concept, Duisterhof started looking for other solutions. He found one by replacing a camera with small lasers and observed a difference of several megabytes in terms of storage. This also resulted in drones being lightweight and able to fly for a longer duration. “By developing an algorithm that makes use of a set of simple behavioural rules, I was able to reduce the amount of data even further,” he notes.
Duisterhof’s small mini-drones are interesting not only because they address a real-world problem but also because of their inspiration: insects. The graduate student explains that he took inspiration from insects for the algorithm powering the drone. He calls his insect-inspired algorithm a bug algorithm and his Master’s research is succinctly titled “Sniffy Bug”.
Insects manage to navigate using simple behavioural rules and avoid collisions in the process. Duisterhof took inspiration from this behaviour and designed his own algorithm. The algorithm incorporates a total of 16 parameters, including one that prevents drones from flying into each other or hitting a wall. They do so without keeping so much distance that they miss the gas leak.
These small mini-drones designed by Duisterhof also incorporate the so-called particle swarm optimisation (PSO) to ensure that the drones work together. This is the cornerstone of the success of this project, where the drones manage to detect gas leaks in coordination and without flying into each other.
Successful test with free software
One of the challenges while designing a drone is finding readily available components. Duisterhof faced this challenge by building the hardware for the drones himself. “The gas sensors I used can be found in standard smoke detectors, but I had to develop the green printed circuit board with the chip myself,” he says.
He describes designing the PCB to be one of the challenging endeavours during his master’s project. Since the software program needed for the drone was expensive, Duisterhof settled for a free trial that ran out after 15 days. This only made the task more testing since he needed to get the design right from the get-go. “I managed it with the help of a PhD student. After that, I had to solder it under a microscope. That was another thing I’d never done before,” he explains.
After getting the design and software finalised, it was time for Bart Duisterhof’s smart mini-drones to fly. The drone with a diameter of 12 cm and weighing only 37.5 grams was tested using a computer simulation model written by Duisterhof himself and they were also successful in detecting a gas leak. When one of the drones detected a gas leak, the other two began flying towards it, which showed that the project was successful.
Autonomy of small robots
Duisterhof has managed to build a drone that is small, lightweight and capable of doing things that large drones are sold for. It is able to do so because of indigenous design, self-developed PCB and reprogrammed software that enables communication. All of this can also be described as materials needed for further advancement in the autonomy of small robots.
“When I embarked on my degree programme, I imagined I’d later go on to build aircraft at Airbus or do something in the space industry. But it ended up being almost the exact opposite: tiny flying machines close to the ground. I think artificial intelligence is absolutely fascinating. Even more than flight system dynamics,” he adds.
While these drones were designed to detect gas leaks, they can also be used for other purposes like greenhouses or a moon lander. His project and its impact resulted in Duisterhof being named Best Graduate of the Faculty of Aerospace Engineering.