The Glider. Tarun Kadri Sathiyan, doctoral student, and Ola Benderius, associate professor, are building a glider. Among the components that make up the device is a long carbon fiber tube.
It may seem a bit inconspicuous to a passerby, just an anonymous metal door on a street in the former shipyard area at Lindholmen in Gothenburg. But inside – at the research laboratory Revere, a part of Chalmers University of Technology – cutting-edge activities regarding vehicle research are carried out, which, among other things, also have bearing on C2B2.
Inside the door opens an airy warehouse, with several meters in ceiling height, and which swallows several bulky objects. A truck, a passenger car, a chassis for a smaller home-built racing car. A large aluminum boat. The vehicles are included in various research projects, among other things with a focus on technology for autonomous vehicles and craft. On this particular day, the lab is responsible for a large stand at Svenska Mässan – a fairground in Gothenburg, so the room is quite empty of people. Ola Benderius, associate professor, and Tarun Kadri Sathiyan, doctoral student – both at the Department of Mechanics and Maritime Sciences at Chalmers – have the room to themselves.
They lift out an impact-resistant black plastic case, about one and a half meters long. From it they unpack a long carbon fiber tube with a diameter of around a couple of decimeters. With the help of a 3D printer, they have produced a pointed yellow top for the tube, plus a cap that plugs the back end.
The construction is called ”a glider”. A kind of measuring instrument that slowly moves through water.
The glider they are working with is part of C2B2’s work package 2: Open, data-driven innovation and new technologies. It has sensors connected to equipment on the inside. During movements in the water, the sensors record depth, water temperature and salinity. On the journey through different water layers, it measures the various parameters ten times per second.
As for how it can move forward in the water, the glider is equipped with an ingenious construction. With the help of a pressurized oil-filled bladder – a so-called buoyancy engine – the glider can change its own buoyancy and thus rise or fall.
It can also adjust its angle of attack by moving its own battery forward and backward.
The batteries are moved to tilt the glider pointing down or up by 20 degrees. And when falling or rising this angle – and with a little help from small wings attached to the tube – it will result in a force forward.
Thanks to this clever “hack” of the laws of physics, the craft moves forward, using almost no energy at all. The distance to the bottom becomes the decisive factor for how far the craft travels when it dives.
– Depending on how deep it is at the current location, the glider chooses a certain maximum depth, for example 70 meters, says Ola Benderius.
The dive takes place in a long slow motion, which for this particular glider will last about an hour.
Eventually, when it comes to the surface, the computers in the laboratory on land can locate it and automatically set a new course with a new maximum depth, and let the glider set off again.
– Once it is released into the sea, it is supposed to be able to stay out and dive for months, says Ola Benderius.
In addition to distinct research-related purposes, there are also other contexts where the elongated construction could be useful.
– For example, for companies that work with offshore wind power, they want to have various facts about the area before they start building, says Tarun Kadri Sathiyan.
To optimize the glider’s ability before it is released into the water, they have used a so–called hardware in the loop simulation.
– We have connected the glider’s sensors directly to a computer, says Ola Benderius.
They have then provided the sensors with synthetic data, giving the researchers the opportunity to evaluate and optimize the function while the device is still on a workbench.
As for the outer construction itself, it is almost fascinatingly simple, made with materials that are relatively easy to buy or make yourself. Despite the simplicity, it takes some working hours to get the slider ready.
In addition to Ola Benderius and Tarun Kadri Sathiyan, around twenty students at Chalmers University of Technology have invested time in the project.
A lot of value in the form of working time is thus invested in the process. Even the measuring equipment itself is expensive, and since the glider cannot steer away if it encounters an obstacle in the way, there is some danger of it colliding with something and potentially being lost. They must always keep that risk in mind.
– But of course we will avoid releasing it into waterways or the like, says Tarun Kadri Sathiyan.