newsletter April 2019
Easter Workshop Text: Erik Brettingen Johansen Photos: Ă˜yvind Ingebrigtsen
Workshops, completion of the car, football breaks, Easter lunch and an Easter egg hunt were some of the activities happening during the easter workshop. 17 days were left until the car was to be unveiled. 17 days until everything had to be completed and in working condition. For the aerodynamics group, their main task was to complete and paint every aerodynamic element within the end of the week. Each part has to be sufficiently sanded and prepared for painting, which takes a lot of time considering all the aerodynamic elements we have. The suspension group had received the 3D printed uprights and were mostly concerned about mounting everything together. As there were so many parts flowing around, the general rule was: If you don’t know what something is or it is not yours, then don’t touch it.
As for the Driverless vehicle, the main challenge was to understand Atmos, and to manage the wiring and hardware on the car. Even though Atmos was a reliable car, it still takes some time to transform it into a driverless car. Keeping true to traditions, there were both an Easter lunch and an Easter egg hunt. The prize had to be found by solving several riddles giving away a code to the lock hiding a huge easter egg filled with candy. The workshop also included several football matches, and a hike in the woods to have a barbeque. As sending the four electrical motors from Germany to Norway through the customs during the holidays would take a lot of time, the team decided to drive all the way to the manufacturer to pick them up. The trip was only supposed to last for 48 hours, but of course, that is not what happened. After we had picked up the motors and driven back to Norway, it became apparent that some legal documents were missing. The group had to drive all the way back to Germany, search for the documents in a time when everything was closed because of Easter, and then return to Norway. In total, the four members spent 99 hours in the car, which we think is a perfect example of how dedicated we are as a team.
The Unveiling Text: Rafi Khajeh Photos: Miriam Eilén Nerheim & Hugo Schleicher
At Studentersamfundet on 2nd May 2019, we revealed our new electric car and our second driverless car. The Unveiling was a proper celebration of our work and of the support we have received both from sponsors, friends and family. With two impressive cars, the whole audience couldn’t do anything else than gasp a silent “Wow” while clapping.
Both cars and the event itself was appreciated and we received feedback that people had a wonderful time. We want to thank every sponsor, every family member and all the students for attending and for making our unveiling such a sensational evening for us. What better way is there to motivate us when we are moving into the testing period?
After months of hard work, the race cars named Nova and Atmos driverless were revealed and presented to our sponsors, families, and students. The evening kicked off with some sushi and drinks and it ended with lots of cake and more drinks all while hanging around the new cars.
Did you miss the unveiling or want to see your favourite part again? You can see the entire unveiling on our Youtube channel right now.
Next Generation Racecars Text: Erik Brettingen Johansen Photo: Øyvind Ingebrigtsen
Nova
Nova is our sixth electrical race car, and the fourth that is four wheel driven with an electrical motor in each wheel. The car has a top speed of 115 km/h, and it weighs only 165 kg which is a reduction of 17 kg from last year.
Mechanical
When driving at 60 km/h, this year’s aerodynamic package produce a downforce equivalent to 95 kg. This is an increase of 14% compared to last year’s design, without increasing the air resistance. The calculations used to go through these design iterations has required over 1 million CPU hours, which would take a normal PC over 114 years to process. We have by ourselves and in cooperation with sponsors produced 113 moulds in aluminium and wood. We have coated all of these with 5 layers of chemicals and sanded each part for hours. An effort resulting in nothing less than 56 in-house produced carbon fibre parts. This year, we will for the first time ever drive with self developed, electrical motors! This has led to more flexibility in how we make the parts in the wheel interact, and of course learning a lot along the way. This has enabled us to make an even more compact gearbox, and we were able to reduce the weight by 15% which is 3 kg. We have also increased power with 22% and increased the top speed from 110 km/h to 115 km/h
We have worked with motor development over several years. This year we have cooperated with the German motor producer Fischer Elektromotoren to make the four motors. It has been very exciting, we have learned a lot along the way, and we want to thank all the sponsors and people that helped us make this a reality. -Eirik Bodsberg, Chief Mechanical Engineer
Electrical
Inside the car there is an advanced network of electronics and cables that each send each other tens of thousands of messages each second, with data such as the voltage over each battery cell with one part per thousand precision, the velocity and position of the car with millimeters in resolution, and the amount of current going through the cables measured 2000 times a second. This year, by changing from CAN 2.0 to the CAN-FD protocol, we are allowed to transfer seven times more data each second compared to last year. One challenge that appeared during last year’s competitions, were the threat of overheating of the battery when temperatures outside exceeded 32 degrees Celsius. That is why we have focused on improving the cooling system, which we have done by rearranging the battery cells. The new arrangement allows for 300% more exposed cooling surface, but required 10 comprehensive design iterations to complete.
Revolve NTNU has a long history of developing our own inverters. The alternative is to buy commercially available inverters, but these are bigger, heavier and harder to troubleshoot. At full speed, the inverters and the motors are able to produce a force equivalent of lifting 500 kg straight up in the air, and the driver experiences to be pushed back in the seat with double his own weight. To make this happen, the inverter has to convert the direct current from the battery to alternating current. We use 24 SiCMOS transistors to make this work, and they each open and close 12 000 times per second. If only one of them miss with less than 700 billion parts of a second, then the consequences are catastrophical. This tells about the precision required to control the inverters without even mentioning the heavy theory behind. The inverter project has lasted for over four years, eight students have dedicated a year of their life in which three of them have written a master thesis on the matter. This is without even mentioning all the competance and funds we have gotten from external partners. We are proud to say that this year we have a working self-built inverter.
Atmos driverless
The driverless project in Revolve NTNU needs primarily three things. Firstly, it needs a car that is reliable and works both mechanically and electrically. This includes the competence to be able to fix the car if something happens to it. Second, you need code to make the car, based on the surroundings, make choices about where to drive. So far we have more than 65 000 lines of code, which approximates to the number of words there are in the whole trilogy of Lord of the Rings. Lastly, and maybe most importantly, you need dedicated people who are willing to put down the efforts necessary. With the help of two LiDAR’s and a camera, the car is able to navigate itself. In total, we process more than 39 million pixles from the camera every second. That is about the same as 20 TV-screens. The two LiDAR’s on our car compliments each other, and accumulates in 1.6 million points each second. To find the right path, the car makes calculations about around 50 000 possible paths each second, and chooses the right one based on probability. This pipeline going from raw data to action runs at 15 Hz and that with a processing unit which is 70% smaller than last year. The overall goal is to be able to drive 10m/s with the driverless car for team 2019.
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