Archives de
Auteur : touloje

Season 4 – Guerlédan Diaries

Season 4 – Guerlédan Diaries

Focus on a crossover project

Today we followed six robotics and hydrography students in Guerlédan. Their aim is to map the seabed of the lake using an autonomous surface drone: we call that a bathymetric survey. Bathymetry is the science of measuring the depths and relief of the ocean to determine the topography of the seafloor. ENSTA students have a companion named Ulysses: it is a semi-autonomous catamaran developed jointly by Texys Marine, a company which manufactures surface drones and sensors, and ENSTA Bretagne. Currently, no device can carry out a bathymetric survey in complete autonomy. Instead, survey boats are brought back to the lab to check the results. In case of an inconsistency, or in case of an error, scientists have to repeat the entire mission.

Our team’s main objective is to develop algorithms that will allow Ulysses to map the seabed in complete autonomy. For this purpose, Ulysses will be equipped with a multibeam sounder – a type of sonar that is used to map the seabed, – a GPS and an inertial unit – an electronic device that measures a body’s specific force and its orientation. In addition, it must be able to perform real-time data quality control, which will indicate where it will have to come back to for additional surveys. This project is at the crossroads between two different fields: Robotics and Hydrography. Robotics uses a lot of middleware – interfaces between software and hardware – are used, such as ROS (Robot Operating System). On the other hand, in hydrography, most software are under Windows. Managing communication between these two worlds is a real ordeal for our engineers!

Season 4 – Guerlédan Diaries

Season 4 – Guerlédan Diaries

Day 3

Today the weather was kind to us, windy but sunny. Some fearless students even went for a swim.

Focus 1 : Brave, the autonomous sailboat

The autonomous sailing boat named Brave was first designed by the IFREMER and built by ENSTA Bretagne to to compete in the World Robotics Sailing Championship (WRSC). This world champion autonomous sailboat is able to navigate thanks to a GPS and can change sail orientation by measuring and adapting to wind direction. Today third year students sailed it from one buoy to another using only camera detection. Tomorrow, they will test software to analyze images of buoys and will look for a way to detect them automatically while sailing.

Focus 2 : Can whales detect fishnets?

Some whales eat fish trapped in fishnets. To meet their quotas, fishermen end up casting more fishnets, which disturbs sea life.

Third years students are trying to understand how whales detect the presence of fishnets. To do so they immerse 4 hydrophones into the water to simulate the ears of whales.

With boats, they made noises at the surface by moving in the exact same way as fishing boats when they deploy fishnets. They managed to record the sounds of manoeuvres with different boats. Their next move is now to try and analyze and sort the recorded sounds using specific algorithms. This should help them determine whether whales can, just by hearing noises, detect the presence of fishing boats and fishnets.

Season 4: Guerlédan Diaries

Season 4: Guerlédan Diaries

This year is the first time second year robotics students have travelled to Guerlédan lake with the third year students. For us the aim of the stay is to work on GPS navigation with small boats called DDboats. These new boats were made by our robotics teachers Mr Benoit ZERR and his colleagues.

The stay is composed of a mixture of classes and practical work all aimed at reaching a point where the boats are able to perform a simple choreography on the lake without crashing into each other, a seemingly impossible feat in such short time.

Now the second day has come to an end and not a single DDboat has made it to the water. At that point most of the work has been done on computer simulations, which provide a simplified model of the boat and simulate the precision errors of the GPS. The hardest part is to estimate the position of the boats as precisely as possible.

Here is one example where the aim is to keep a given heading. The blue dots (which are mostly hidden by the other dots) correspond to the real trajectory of the boat. The red dots show the simulated GPS values, which have been randomly modified to fake the errors of real GPS measures. Finally, the green dots correspond to the estimated position. A system filters GPS values to get as close as possible to the real values.

The above picture shows the same kind of simulation but with a U-turn. Indeed, during the first attempts the simulated regulator was so unstable that a U-turn was impossible.

Finally, today was also the first time we had analyzed real world GPS data. Our teacher collected GPS data on the site, by walking the boat around. We than read this data and filtered it. The next picture is a plot of the real data (in blue) and the filtered data (in green). Finally the arrows correspond to the estimated speeds at each point.

And that ends the news for today, see you tomorrow for the latest updates !

Season 4 – Guerlédan Diaries

Season 4 – Guerlédan Diaries

Day 2

We’re back today with updates about our time at Guerlédan Lake. Here both the second- and third-year students are working on their respective projects while taking advantage of the lake for experiments.

Today we’ll focus on two groups of third year students and their respective projects.

The first group we shadowed are working on a sci-fi like project where the goal is to use a sensor called a LIDAR in cooperation with an inertial unit to locate yourself more accurately when a GPS is unable to access your position – because of obstacles or because you are underground.

Those students spent their day calibrating the LIDAR sensor (in the foreground of the picture) to make sure that the data it measures is correct. As it is humanely impossible to perfectly align the captor with the ground, this patch test ensures that the raw data won’t be affected by the offset. The LIDAR sensor is now able to compensate the flawed data.

In the meantime, the students working on the analysis of water columns in order to count fish populations were busy comparing and improving IFREMER’s and ENSTA Bretagne’s methods and equipment. The day was well spent diving into the arcane depths of the software as a first step towards their goal.

IFREMER’s software being incompatible with ENSTA Bretagne’s measuring protocol, they first needed to write a program that will enable them to draw charts of both data sets in order to compare them later this week.

Tune in for more news about exciting student projects tomorrow!

Season 4 : Guerlédan Diaries

Season 4 : Guerlédan Diaries

Day 1

Day 1

After a two-hour bus trip, ENSTA Bretagne 3rd year hydrography and oceanography students as well as 3rd and 2nd year robotics students discovered the inviting weather conditions at Guerlédan.

But why do ENSTA Bretagne students head to Guerlédan lake each year?

Two weeks a year, this place is turned into a real-size test laboratory. The lake bed was documented the last time the lake was emptied, so hydrography and oceanography students can explore it using the techniques they have learnt, and check their findings against the available data. The Guerlédan lake also provides students with rich opportunities to explore maritime application of robotics, conduct experiments and hone their problem-solving skills.

What did ENSTA Bretagne students do during this first day?

Once on site 3rd year students quickly started working on their respective projects, while the 2nd year robotics students attended a lesson on inertial navigation systems.

After lunch, students got back to work. 2nd year students kick-started their English podcast production workshops by making contact with the groups they will be reporting on all week.

A focus on “Isobath tracking with an Autonomous Underwater Vehicle” project.

Four robotics students are currently working on a torpedo-shaped underwater drone.

            Fig: Isobath tracking principle

This drone is meant to follow an isobath and must be autonomous as it is immerged.

Autonomous Underwater Vehicle

An isobath is an imaginary line or a line on a map or chart that connects all points having the same depth below a water surface – an ocean, a sea, or a lake.

A thruster located at the back of the Autonomous Underwater Vehicle allows it to move forward. Four other water pumps steer the drone. The motor of the drone has been fixed today, as it was defective.

Focus 2: The BOATBOT

The boatbot project consists in automating a motorized zodiac so it can draw a map of the seabed. The zodiac can already steer itself but has yet to be able to regulate its speed, which is what Erwann, David and Philipert hope to achieve by the end of this week. They are also exploring ways to adjust the length of the underwater probe in order to avoid collisions.

Boatbot has been designed to look for La Cordelière, a Breton battleship built in the fifteenth century, equipped with two hundred guns and manned by a thousand crewmen. It was part of Duchy of Brittany’ Navy and was destroyed during the battle of Saint-Mathieu: while the ship was in Brest hosting the celebrations of Saint-Laurent’s day, the English fleet was preparing a landing in Brittany, and the Cordelière was dispatched to intercept them. It was met by a larger English fleet, and fought valiantly against the British ship “Regent”, and both ships were destroyed after the Regent tried to board the Cordelière. It is estimated that two thousand men died in the battle, and among them were three hundred civilians still on board the Cordelière. All previous attempts to locate its wreck have been in vain and its location remain unknown in Brest bay.