newsletter October 2019
COMPLIANCE TEST WITH NOVA Text and photo: Sindre Sagstad
Our Suspension and Drivetrain group has been working on developing the new suspension for next year’s car. The group designs crucial parts of the car such as motors, gearboxes, wheels, steering system, brake system and suspension. Improvement is always on Revolve NTNU’s agenda and in order to improve we have a continuous dialogue with alumni to get the best transfer of knowledge. Another way to improve is to gain a deeper understanding of all the different parameters of each system. For the suspension group this means getting more information about how compliance affects the vehicle dynamics of our car. Compliance is a phenomenon that can be described as the inverse of stiffness. In other words: it is how our suspension behaves under load. The basic goal of a race car’s suspension is
maximizing the contact between the tires and the road so that the tires can generate the highest amount of force possible, thus making the car go faster. The Vehicle Dynamics group develops the suspension geometry and kinematics using our self-made optimization algorithm based on the assumption that the suspension has infinite stiffness. In reality this is not the case. During a track round the suspension takes up all the forces acting on the car. This will cause compliance (deformation) in every component in the suspension. This changes the wheel’s angles relative to the road which deviates from the theoretical angles the suspension is designed for. This affects grip and how the car behaves. How much the suspension deforms is very hard to measure. It is even more difficult to measure how much each
component contributes to the total deformation. There have been multiple attempts at getting better estimates earlier years, with varying results. This year we have chosen another approach, using digital image correlation to measure how the suspension behaves under load. The compliance test is done by placing reference points at areas of interest. A force, which simulates lateral forces the car experiences during cornering, is
then applied to the wheels. The force was applied using a turnbuckle and measured with a load cell. A force of 3 kN was used in the experiment. Two cameras were then placed so they could capture the points placed on the suspension and wheel. Additionally, a camera was placed to capture what load is applied in every instant. The cameras can then recreate these points in a three-dimensional space, where we then can measure how the points move when different
forces are applied. This enables us to confirm how the angle of the wheel reacts to a given lateral force. Points were also placed on different members in the suspension to try and estimate the displacement in each member. It should be mentioned that this was an early stage experiment, with some uncertainties. The results from the test are still being processed and we are very excited to see what the outcome of the test will be. An early guess is that we will be able to estimate the change in angle down to one
hundredth of a degree. If the test turns out successful, we will further investigate how to perform a more realistic test. We think the technology of digital image correlation has great potential for helping us designing an even faster race car. We would like to thank the Department of Structural Engineering at NTNU for making it possible to perform this test with lending us both equipment and helpful personnel. This is greatly appreciated by us in Revolve NTNU.
PCB DESIGN IN PROGRESS Text: Sindre Solberg Photo: Sindre Solberg og Marion Christine Løkkevig
Last month our Embedded Electronics group have worked on schematics and layout for the Printed Circuit Board (PCB) prototypes. First, new members had to learn their systems and get used to Altium. Altium is an industry-leading schematic capture, layout and prototyping tool. This year Embedded Electronics will make around 40 in-house developed PCBs. The different systems we will further develop are:
• Accumulator Management System: System responsible for voltage and temperature measurements in the accumulator. • Dashboard: The car’s dashboard consists of LCD-screen, indication lamps and buttons. • Inverter & Motor Controller: Last year this group made an in-house developed inverter for the first time and this year the group will try to make it more compact. • Safety Systems: Formula Student has high security requirements. These systems are made to make sure the car is safe to operate. • Sensors: There are multiple sensors on the car, and more sensors are added every year. There were over 300 sensors last year. • Vehicle Control Unit: Responsible for data processing, telemetry and safety features done in software.
After working on some designs of PCBs the group had a PCB design course with NORBIT. There they were showed some of NORBIT’s designs and got help to identify aspects where they can improve on their own designs. The course was helpful and what they taught will be used to develop the PCBs for our next racecar. Special thanks to Håkon Leithe and Øyvind Schei for holding the course. The next focus will be to finish the prototypes for the PCBs and get ready for testing!
ROAD TRIP WITH NOVA Text: Espen Bergset Jacobsen Photo: Marion Christine Løkkevig
During the first week of October it was time for our yearly tour visiting sponsors. Four members headed south with Nova safely strapped in our trailer. During the 8 hour ride to Oslo on Monday they took a short visit at Skriverform on the way. Here, they got a tour of Skriverform’s workshop where our uprights have been postmachined. Next day, the trip went to Hønefoss to visit Tronrud Engineering. Tronrud Engineering helped us 3D-printing our awesome uprights. Here the employees got to sit in Nova and many were eager to learn more and asked many interesting questions about the car. The members attended the Career Day at NMBU on wednesday. Here they exhibited Nova on stand along
with COWI. The building was packed with eager students and companies. Naturally, a lot of students were drawn to the racecar, and came to talk to both Revolve NTNU and COWI. On Thursday, it was finally Kongsberg Gruppen’s turn to see Nova. Our members held presentations about the project and our cars. Before calling it a day, the members paid a last visit at Semcon nearby. Semcon helped us machine the rotors, endbells, and housing for our engines. Many employees showed up to get a glimpse of Nova, but they were not the only ones interested. A group of kindergarteners came along and also wanted to see the car. Never too early to start recruiting, right?
The trip ended on Friday with a last sponsor visit, this time to Bertel. O Steen, who signed an agreement to continue as one of our main sponsors for the two coming years! A presentation of our cars was given, before we had an exciting discussion about the constantly changing car industry and its possibilities and challenges. Throughout the whole week our members were met with a lot of curiosity and interest, and they truly enjoyed visiting and talking about the project with our dedicated sponsors. Thanks to Kongsberg Gruppen, Bertel O. Steen, Tronrud Engineering, COWI, Skriverform and Semcon for having us, we’re looking forward to continue working with you this year!