Last weekend, teams from 30 universities around North America descended on New Hampshire Motor Speedway in Loudon for the third annual SAE Formula Hybrid challenge. Formula Hybrid is an offshoot of the long-running Formula SAE student design competition, except as the name implies, the cars have hybrid powertrains. The first two instances of the competition were both won by the team from McGill University in Montreal, Quebec, Canada. We spoke to McGill team member Jeff Turner after the initial competition, so we were naturally interested to hear how McGill's entry performed this year.
After using a modified Formula SAE chassis for the first two years, the McGill team built an all-new car this year specifically for Formula Hybrid. Instead of the parallel hybrid used in the original car, the McGill team went with a series hybrid configuration this time. Unfortunately, the car wasn't completely sorted out and had a number of problems. The Subaru Robin single cylinder engine the team has been using for two years was down on power from even its original 7 horsepower rating. As a result, the charge-depleting setup turned out to be even more depleting than intended.
A number of other teams also ran series hybrids, and the team from Brigham Young University even built a hydraulic series hybrid. Unfortunately, the hydraulic system was ruled ineligible under the current rules, so the team couldn't compete. You can read Jeff's description of this year's event after the jump.
[Source: Formula Hybrid, Jeff Turner]
Photos Copyright ©2009 Jeff Turner/ Adam Laidlaw / Ali Najmabadi
We've spoken before, Sam wrote a few pieces on some of the hybrid and EV projects coming out of McGill University up in Montreal. Anyway, we just returned from the 2009 Formula Hybrid competition in Loudon NH, and I thought that if you'll be doing a piece on it some time soon, you might appreciate some input from one of the competitors.
Well, we definitely did not get our third consecutive victory this year! We returned to the competition with a new car, built from the ground up as a series hybrid with independent rear wheel drive, as opposed to our first generation racer which was a modified FSAE car. Our overall configuration was largely the same, with many of the same components as before, but optimized to squeeze the most performance out of each, and rearranged in a way to make assembly and maintenance more bearable. Our battery was downsized slightly last year, lopping off two cells to form an 18 cell, 45 amp-hour, 64.8V nominal pack, or about 2.9kWh - cells and battery management system care of Lithium Technology Corporation.
Our "range extender" is still a 7hp Subaru-Robin single cylinder four-stroke, 211cc. This output about half of the average driving power required during last year's endurance event, so it's definitely a "charge depleting" hybrid, so we keep it running right from the start! though we can force it into EV mode whenever we want. This year we swapped out our German Perm PMG 132 generator for a made-in-America Mars Electric ME0709, a similar DC brushed, permanent magnet motor that puts out just as much power, weighs about 16lbs more, but costs about half the price of a Perm, and seems to be much more robust in the high temperature application of being connected to an IC engine.
Our drive motors are still PMG 132's though (6hp continuous, 15hp peak), coupled independently to the left and right wheels through pulley-type CVTs. What was exciting this year was that, thanks to a CompactRIO programmable controller donated by National Instruments, we were able to control the two motors independently based on steering angle, sending more power to the outside wheel in a turn. This gave us a really sharp turning circle, and also gave us a lot of configurability for the handling characteristics of the car. We even reversed the signals in the rain, giving more power to the inside wheel, and this really gave us a lot more control and prevented spin outs. The same micro controller was also in charge of controlling our generator, monitoring motor and generator temperatures and ramping down currents if ever there's risk of overheating, recording data and storing it all on a USB key, as well as displaying useful information to the driver via a student designed Palm pilot touch !
screen display program.
Anyway, as I said, we didn't perform quite to expectations this year. We ran into a number of problems, most of them small and easily overcome, but our trusty Subaru engine seems to have gotten a little tired. We believe our harsh stop-start cycling has caused the timing chain to skip, so we were getting pitiful output coupled with extreme temperatures. We didn't manage to fix this in time for the endurance event, so basically had to squeeze everything we could out of our batteries to complete the full 22kms. Eventually, the batteries were drained, and unlike the Volt, our engine was not providing adequate power for the vehicle to perform acceptably. We still managed to complete the event though, so we were pretty pleased with that.
So that's our story. We were much busier than other years when nothing ever seemed to break down on us! I think this was actually a good thing - we had a much bigger team than other years, having recruited a whole bunch of 1st and 2nd year students, and they all got to learn a lot from all the problems we had. And we generally had a really great time, so I think we've set ourselves up for a great year next year.
This competition is always great for seeing a wide variety of different concepts and technologies. There did seem to be a number of teams following our approach of series hybrid with independent rear-wheel drive, including the 3rd place Drexel University. Drexel, however, uses ultracapacitors for energy storage (much less energy) and therefore runs a more powerful engine that is able to provide the average power requirements for the vehicle - a charge sustaining hybrid as opposed to our charge depleting hybrid with high energy storage batteries and a weaker engine. Illinois Institute of Technology (IIT) showed up with two cars this year, one a parallel hybrid, but their series hybrid was VERY impressive. It wasn't running at the comp, but it was quite something to look at. We coined the term "All-dressed Hybrid"... It was four wheel drive, with a PMG 132 at each front wheel, coupled through a custom built planetary gear (i think I heard 4:1 step down in speed from motor to wheel). It then had a massive AC motor out back, plus a DC generator, similar to our own arrangement, though I don't know what kind of output it had. For accumulators, it ran both Li-ion batteries AND ultracaps. It looked great too, the front wheel motors giving it a wider track in front than in back, making for some great proportions. Unfortunately the car was not in running condition for most of the competition, although hopefully we'll see it again next year.
Brigham Young University surprised me by showing up with a series hydraulic hybrid. We had looked into adding hydraulic regen brakes to our front wheels last year, but gave up when we found out that batteries and ultra-caps were the only allowable energy storage media. These guys from BYU thought they would be allowed this year, but found out just recently they would not be allowed to compete. Nevertheless, they came to demonstrate their car, and I'm really glad they did. It used two carbon fiber accumulators to provide pressure to a hydraulic motor at each rear wheel. These motors can apparently deliver a real punch from a tiny package, I don't remember any specific numbers though unfortunately. They were not allowed to drive the car at the competition, but I've heard some pretty incredible claims. They were given awards for innovation.
In general, its felt that the competition does not put enough emphasis on fuel efficiency. The winning team, Texas A&M, was what I would call a fairly mild hybrid. In fact, it completed the entire endurance event without the electrical systems energized, essentially proving that a stock FSAE car is the best way to go as the rules are currently laid out. Even if everything had worked as planned for McGill, I don't think we would have performed better than this very ICE dependent entry. They simply did a very good job of analyzing the rules and deciding logically on the best approach There are only two events that imply a certain degree of fuel efficiency and drivetrain electrification:
-Drive 75 meters on electricity alone in under 12 seconds
-Complete the endurance event (22kms) on 4 litres of fuel or less.
You are not given any points for fuel left over at the end of the event. That works out to under 13mpg!! Having completed all events at every year of this competition, we can tell you that 4 litres is more than enough fuel, and every year we've emptied our gas tank into the rental car for the trip home. I was talking with Jay Friedland of Plug-In America, and we both agree that the organizers need to change the rules to encourage more innovative and fuel efficient designs.
Anyway, sorry for the rant. If you're interested, I have a few photos from the competition, and I could even scan my copy of the competition brochure which has a brief tech description for each of the 30 teams.
One of you guys should make the trip down to the competition next year! Make sure to come and say hi to McGill!