It’s been said that experience is the best teacher, and that the lessons worth learning are always unplanned. It was in this spirit that Blue Sky Solar Racing’s May testing trip took place this year. Withthe goal of being able to give new team members an opportunity to experience race conditions, 20 team members, both veterans and newcomers, spent May 27th to 30th at the Grand Bend Motorplex and Brantford Airport putting Polaris, the car raced in the 2017 World Solar Challenge through its paces.
Despite being race proven, getting the car ready for some road time involved more than just loading it up and heading out. In the preceding months, it had served as a testing and development ground for new fabrication techniques, mechanical assemblies and electrical circuits. As a result, getting it back in tip top shape proved to be the perfect way to train new team members. Everything from bleeding the brakes and checking the steering calibration, to charging up the batteries needed to be done. Finally, months of learning the fundamentals of how the car is built was put into practice and the new recruits rose to the occasion.
A question that’s been asked is why plan our own testing trip rather than running another race such as the American Solar Challenge (ASC). It comes down to a matter of return on investment. This team deemed it more valuable to focus on designing the best possible car for the World Solar Challenge (WSC) rather than investing time into modifying Polaris to conform to ASC regulations. As a result, the team has been able to effectively add an additional 6 months of design time to the next generation car while still building experience in race conditions from testing trips like this one.
After 2 days of testing and driving at both Grand Bend Motorplex and Brantford Airport the team had a wealth of new data about the car’s driving characteristics. The new team members also experienced first hand the impact of not only design decisions but also logistical ones. With WSC lasting approximately 5 days and 3 weeks of testing in Australia preceding the race, being able to coordinate food, transport of supplies, support vehicles and safety procedures is critical. While things went quite well for the most part, a valuable lesson, provided by strong winds, taught the team how to rapidly relocate and appropriately secure tents and vehicles.
A sincere thank you to all our sponsors for making testing trips like this possible is in order. We would especially like to thank Brantford Airport and Grand Bend Motor Plex for providing the venues used for testing. As the next generation vehicle makes its way through the design pipeline we are more confident than ever that WSC 2019 will be our best race yet.
Electrical Test Bench
Being a team that designs, builds and races solar vehicles the ability to test and verify the performance and functionality of the electrical systems is key. The system has many components
including but not limited to firmware, software, hardware, printed circuit boards, sensors and wiring. To confirm that these systems behave identically to simulation requires continuous testing as both individual modules and a overall system. The need for modularization has motivated the creation of a new test bench.
The test bench is based on an off the shelf pegboard with the individual system components (printed circuit boards) arranged on plexiglass stands. This makes it easy to place and connect modules and also swap module versions. Furthermore, with the new power supplies and instrumentation generously provided by Rigol it is now possible to completely simulate the entire car’s electrical system on the test bench. As a result, continuous integration and testing of new submodules can now happen on an almost daily cycle. With a working system, a newer version module can be swapped in, tested, debugged and verified in in just a few hours. This in turn will result in a system that meets the team’s “triple R” race requirements: reliability, robustness and repairability.
The new electrical test bench wired up and running. Swapping in a new module is as easy as moving a few cables.
With the systems for the new car already starting to take shape, building the testbench has proved to be an excellent exercise for the new team members. It has given them a better understanding of how what they’re working on will contribute to the overall vehicle. This has also allowed the more experienced team members to focus on understanding and designing the new car to the 2019 World Solar Challenge requirements without needing to spend as much time bringing new recruits up to speed. After all, measuring voltages, soldering new components and trying new modules is learning that’s hard to glean in reports.
A sincere thank you is owed to our sponsor Rigol for the power supplies, electronic loads, and oscilloscopes that helped make the new test bench a reality.
Aerobody Design and Wind Tunnel Testing
With race regulations posing stricter constraints on both solar array and battery sizes every year,
making use of these limited power sources is what allows our team to be competitive. To that end, the aerodynamic characteristics of the car have the greatest impact on our efficiency. To design the best possible aero body, our team has been combining simulation with real world testing. While the actual design is still under wraps, we wanted to share the process that’s allowed us to iterate faster than ever before.
In previous design cycles, the team would typically simulate 2-3 different aero body designs per week, which meant that given the lead time needed for fabrication, only about 50 designs could be evaluated. This cycle has increased that pace by an order of magnitude, with around 20 simulations per week now being run. It’s been a better tool set both in terms of compute hardware and software that has made this possible.
Our compute rack
Polaris was designed on a pair of compute workstations from 2010 (8GB of RAM and 4 CPU cores each). This limited the size of the meshes (resolution of result) and meant that a full simulation would take upwards of 20 hours to run. With the support of the University of Toronto’s Engineering Society the team was able to purchase 4 new high-performance workstations. This upgrade at the start of this design cycle (64GB of RAM and 12 CPU cores each) provided a massive boost in performance. However, these did not come with Graphical Processing Units (GPUs) needed to render the 3D models. We were extremely fortunate and are grateful to Advanced Micro Devices (AMD) for sponsoring new Radeon Pro Workstation GPUs, these ensured that all our CAD and meshing software ran perfectly. AMD also provided additional workstations, including one of their new ThreadRipper platforms. We’ve been astounded by the performance these platforms have provided and their reliability (as of present they’ve been online without issue for over 6 months). The team also recently purchased a server which the IT division converted to a High-Performance Computing (HPC) Grid, that the aero team could submit larger simulation jobs to. With the ability to now queue up dozens of simulations, the new compute infrastructure is happily humming away, running different parametric studies to determine the sensitivity of vehicle performance to factors such as width, height and fillet gradient just to name a few.
Despite the enhanced iteration schedule, real world testing is still important. In July, the team conducted wind tunnel testing at the University of Toronto’s Institute for Aerospace Studies (UTIAS) in the lab of Prof. Philippe Lavoie. The team tested 3D printed models of Horizon and Polaris, our two most recent cars, to obtain a better understanding of their aerodynamic characteristics. With the help of MedPrint we were able to print quality models that met our specifications. While the 3D-printing was quick (a few days), the surface finish proved to be the most challenging aspect of fabricating the models. Many techniques were tried and after two weeks the team had finally found a way to achieve the desired finish. In the wind tunnel the team was able to verify their understanding of the vehicle’s dynamics and percolate new ideas for use in the design of the new car.
Once again, a sincere thank you to all our sponsors is in order as you have made it possible for us to iterate through various designs faster than ever before. A thank you to Delta Server Store, the University of Toronto’s Engineering Society, and Advanced Micro Devices for the new compute hardware. For the software tool chain, we would like to thank Dassault for providing CATIA, Aventec for providing training, ANSYS for providing our simulation tools and Applied CCM for providing our meshing tools and valuable support. We would also like to thank UTIAS for time in their wind tunnel. While the aero body for the new car is still under wraps we look forward to unveiling our best one yet in just a few months.
Please stay tuned!
All the best,