October 3, 2013
by Max Praglin
Photo credit: Anna Olson
Greetings from the Hidden Valley Raceway in Darwin, Australia! It’s been a while since we last posted from Port Augusta – and a lot has happened. Since departing from the Southern coast, we ran an approximately 1250km mock race, camped in the Outback while driving through the Northern Territory, settled down in Darwin at the Racetrack, drove a few laps, and (mostly) completed the scrutineering process for the 2013 Bridgestone World Solar Challenge.
In order to train our race crew and verify our race strategy, Luminos drove a mock race from Port Augusta, to Coober Pedy, to Port Augusta, to Glendambo (you could say we’re familiar with this stretch of road). The team practiced race day routines including morning array standing and control points, and also gained valuable experience in carefully metering our power consumption and production throughout the course of a multi-day race. As of the end of our mock race, Luminos has racked up around 4650 miles (7500 km). The car is ready for the 3022km between Darwin and Adelaide.
Mock race: Luminos drives along the Stuart Highway, A-B-C-B-A-B. Map from Google Maps.
The Stuart Highway is a perilous stretch of road having a rough chip-sealed surface (which notably changed our car’s power consumption), high winds, heat, desolation, and wildlife (emus as well as kangaroos after dusk). In spite of avoiding driving after the sun goes down to minimize the chance of wildlife encounters, we narrowly escaped crossing paths with a pair of emus that sprinted between Luminos and our chase car.
Following Luminos on the Stuart Highway. Photo credit: Anna Olson
In an endurance race like the 2013 Bridgestone World Solar Challenge, race strategy is of the utmost importance. Going the “right” speed over the course of 3000km sets apart cars with equal performance. The mock race was an important opportunity for our Strategy Team to complete the MATLAB software used in live monitoring of the car’s status, fetching aggregated weather data, predicting the car’s state of charge in real time to within a few percent, monitoring car health, and logging geo-stamped data that can be reviewed at a later date.
Monitoring and Strategy dashboard after a full day of driving. This software assists in making decisions about how we drive the car.
A key part of our testing included building a power-to-drive model for our car in race configuration on the Stuart Highway. Repeatedly driving on the same stretch of road (at different speeds) helps in characterizing how much power our drivetrain requires. Runs in opposite directions mean that a polynomial fit to measured values will give an approximation of the car’s power consumption on flat ground – a model which is quite useful in strategy calculations.
Upon analyzing the day’s data, a simple algorithm can roughly identify when the car has reached a constant cruise speed. Power values outside these times are deemed irrelevant due to acceleration of the car.
Output of the cruise identification algorithm. Credit: Max Praglin
Power-to-drive model plotted alongside collected data. While not a perfect fit, the red line is extremely informative for strategy decisions. Credit: Max Praglin
SSCP members arrived at the Hidden Valley Raceway and eagerly scoped out the other cars. We are incredibly impressed by our competitors and wish them the best of luck on the track as well as during the race!
Semi-professional tire seating crew (Darren Chen and Jamie Goldfield) use our secret weapon to assist another team. Photo credit: Anna Olson
SSCP had the pleasure of undergoing static scrutineering alongside top teams from the 2011 World Solar Challenge (Tokai, Nuon, and Michigan, to name a few). The car passed through every step of the process – except for the rear vision requirements. We have made adjustments to the white balance of our camera as well as a more rigid mounting system, both of which changes we expect to allow completion of static scrutineering. This video describes our experience at Scrutineering. Look out for more videos from Mark Shwartz at Stanford’s Precourt Institute for Energy, here.
SSCP decides who will drive the “hot lap” on Saturday. Photo credit: Alice Che
GPS logs from a track session at Hidden Valley. Click for animation.
Look for more updates as we move to Dynamic Scrutineering and final preparation for the race!