Blowing up thousands of $5000 engines-virtually

EDN’s December 15 issue includes a “hot technology” feature that addresses model-based design and early prototyping. In researching this article, I visited the The Mathworks and talked with participants (including sponsors and competitors) in the Department of Energy’s EcoCAR competition, in which college teams redesign a production vehicle in an effort to optimize performance and-more importantly-learn to use the modeling and prototyping tools they’ll use upon graduation. The EcoCAR participants were meeting at The Mathworks headquarters in Natick, MA, to kick of year 2 of the EcoCAR competition. (Read about the year 1 in “Grooming the innovators of the future” and “EcoCAR uses student innovation to design more efficient cars.”)

Participating in the September 24 interview at The Mathworks were
–Chad Conway, a sophomore double major in ME and EE, who serves as the electrical team leader for the Rose-Hulman EcoCAR team;
–Zac Chambers, associate professor of mechanical engineering at Rose-Hulman Institute of Technology, who, along with Marc Herniter, full professor of electrical and computer engineering from the ECE department, serves as coadviser to for the institute’s EcoCAR program;
–Mike Wahlstrom, control and simulation engineer, Center for Transportation Research, Energy Systems Division, Argonne National Laboratory, who began his involvement with advanced vehicle competitions as a student and now serves as a competition organizer with Argonne, which manages the EcoCAR program under contract with the DOE; and
–Paul Smith, The Mathworks director of consulting services.

Could you describe EcoCAR?

Wahlstrom: EcoCAR is a three year program and latest in a 20-year history of advanced vehicle technology competitions that have been sponsored by the Department of Energy and cosponsored by companies including GM and The Mathworks. The first year of the program, the students were tasked with designing and simulating a powertrain using model-based design. In the second year they will be building a mule vehicle–they will take an ‘09 Saturn Vue and replace the powertrain with one of their own design.

A mule vehicle?

Wahlstrom: EcoCar and Challenge X [an advanced vehicle competition that concluded in 2008] both use a version of GM’s global development program. As part of that process, GM builds a mule vehicle, and we’ve borrowed the term. A mule vehicle is essentially 60 to 65% ready to go. The year 3 focus of EcoCar is on refinement of the vehicle so that will be more to near production state by end of the year.

And at this point, the beginning of year two, nobody has picked up a wrench.

Wahlstrom: They better not have.

Chambers: A virtual wrench only.

What’s happening now?

Chambers: At this point GM has begun delivering the vehicles.

So now students are ready to pick up the wrenches?

Chambers: A really big mistake that teams can make is that they immediately start tearing the vehicle apart. When they have an operational vehicle, it really behooves teams to use their CAN analysis tools to tap into the vehicle network to make sure they can communicate with all the different modules inside the vehicle and go out and collect some baseline data. They should get their testing procedures figured out while they have something that works before they try to figure out a testing procedure with something that may or may not work all that well. So really, teams should not start tearing their vehicles apart for at least another month and a half.

Chad, how long have you been on the team?

Conway: I joined in winter quarter last January. It was definitely an interesting thing to jump into. I knew coming to Rose that they had the EcoCAR project, and I knew I wanted to get into it. I spent a lot of time watching and learning because there was so much experience from the seniors who started on the team as freshmen with the Challenge X program. This year the seniors have graduated, and we are filling up spots and have started to use The Mathworks software as well as National Instruments software, and we are getting up to speed with the designs that have already been created for our vehicles. I had a lot of experience with electric cars in high school and figured good spot for me was to head up the electrical team. I wanted to be working with the electrical side of things, because as cars move to more microcontrollers and drive-by-wire, you need to know all the electrical systems. But there are always going to be wheels turning, so you need to know mechanical as well.

What approach is the Rose-Hulman team taking with its vehicle?

Chambers: Parallel pre-post transmission electric hybrid. What we have up front is a downsized 1.3l diesel engine. In between it and the stock four-speed automatic transmission we have inserted an electric machine to provide additional capability to the engine to offset its downsizing. On the back axle we’ve placed another electric machine to provide for regenerative breaking as well as additional acceleration, should we need it.

How does it compare with what’s on the road today?

Chambers: What you can buy today is going to be like Prius, which also utilizes two electric machines, but they are up front attached to the transmission. Ours are spread across the front axle and the rear axle. A difference between us and the Prius is the Prius does not change gears. We actually have a four-speed gear box that goes along with our vehicle. Our approach is by no means as sophisticated as GM’s 2-Mode transmission. That is a superior architecture to ours, but ours is an architecture you can understand and implement on the undergraduate level.

How does EcoCar compare with Challenge X?

Smith: The technology has really advanced. Zac made the comment that [the EcoCAR teams] are never going to beat GM’s engineers. GM’s engineers are professional engineers; they do this full time. The EcoCAR competition certainly has the same technology as a foundation, but it is really about producing people like Chad-talented engineers to join the workforce.

What architectures are other teams using in EcoCAR?

Smith: I think everything’s got a plug-in capability. This year we’ve got hydrogen-powered fuel cells, we’ve got a number of different architectures for hybrid technologies, including the one we just heard about, and it’s really a big step forward from what we saw both from a diversity perspective as well as the state of the art that we saw in the last competition.

Wahlstrom: A big thing for us on the organizing side for EcoCAR was trying to make sure we had a lot of diverse components available. That’s what drives diversity in the long run. So we went out and got several sponsors, GM being the biggest, obviously, but we also have battery supplier A123 and other companies as competition level sponsors. What we ended up with is seven teams that are utilizing biodiesel, seven that are using E85, two using hydrogen, and one fully functional electric vehicle. We also have a number of extended-range electric vehicle architectures. And we have many that would be classified as plug-in hybrid electric vehicles.

To get more specific, some are utilizing GM’s 2-Mode transmission as a package solution. Some like Rose have gone out and got their own motor sponsors. We cover a wide range, and there are no two approaches that are identical, which is great. We’ve got wide range of fuels and energy carriers and architectures, and we have a lot of electrification, and obviously that’s a big push. In Challenge X we had one plug in hybrid, and now any of the EcoCAR designs will be able to plug into the wall. And through the first year the teams have come up with some pretty intense near OEM-level designs and design reports.

This is 100% about the students. Like Zac said and Paul alluded, we are not out here to change the world with any one vehicle that we are going to build in the competition. The great thing is that we are building the engineers that will build those vehicles in the future.

Chambers: With the restructuring of the Big 3 automotive industry over the last couple of years, the changing landscape is the most transformative we’ve seen in transportation since the turn of the [20th] century, when people first started to figure out what makes a car go-is it going to be electric, is it going to be gas, is going to be a combination of the two? And engineers like Chad are the ones who are going to help us navigate that path.

Wahlstrom: [The EcoCAR teams] will come out of year 3 with a really good understanding of the whole vehicle-development process, and what that creates is an engineer who knows everything from the environmental impacts to the control impacts. I was impressed with [my fellow] challengex students, but already with EcoCAR these guys are just blowing us away. It’s really incredible to see some of the work that they are doing.

Chad, do you have much free time?

Conway: Not much at all. Between classes and dual major, it’s pretty intense. And EcoCAR is another dual major by itself.

Do students earn credit for participating in EcoCAR?

Chambers: One of the competition requirements is that students who participate should receive some form of academic credit because as Chad said this is a lot of time you spend on this project. At Rose, software is entrenched for all three years. Rose is a unique school. Mark [Herniter] and I worked very hard to embrace the model-based design philosophy and really work it into the undergraduate curriculum. To help make that work Rose-Hulman partnered with the Mathworks, Freescale, and MotoTron, and we have set up the first-in-the-nation model-based design laboratory at Rose-Hulman. We have two classes, an introductory course and an advanced course in the model-based design techniques, and not only are our students able to take these that are involved with the EcoCAR, but other students in the institute can as well. Sophomores through graduate students are learning these design tools that are necessary to be competitive.

What are the prerequisites for the classes?

Chambers: Consent of the instructor. The only prerequisite is some background in differential equations and LaPlace transforms. You’d think in a modeling course like this you would have to know something a out classical control theory. But our approach is to introduce controls from an experiential perspective with some simple systems, and then when students get to their controls class their senior year they say, oh, this is why I care about poles and zeros.

What happens in the advanced class?

Chambers: Once these students get a handle on software in the loop in the first course, we do some hardware in the loop for the second course. First we build our model in software and run it in non real time and see if we can find all of our logical and modeling errors on a very rapid timeline. Once we’re satisfied that’s working, we go to a real-time processor target where using an inexpensive target like XPCTarget. We can then go ahead and start running in real time and start debugging.

What’s XPCTarget?

Smith: XPCTarget is a piece of software from The Mathworks that converts PC hardware into a real-time prototyping or hardware-in-the-loop platform.

Chambers: Once satisfied with our real-time processing on the processor, we then take our controller and break it out onto one physical hardware board, and we take the model of the vehicle and break it out onto another hardware board, and then we have them communicate with each other. When satisfied that’s working, we then introduce a CAN communication network and put in the actual inputs [a controller is] going to receive from the vehicle pedals, shifter, PRNDL, and so forth. Then once we are satisfied that’s all working, we feel confident we can put that on to the actual vehicle and have nothing too catastrophic occur. So it’s really these levels of going through software to processor in the loop to the hardware in the loop that let us really accelerate the design process and catch a lot of potential dangers and errors and do a lot of algorithm and control strategy improvement, without even having the vehicle on hand but still having a good feel for how its going to perform.

So hardware-in-the-loop is a hot topic now?

Wahlstrom: Hardware in the loop involves the vehicle-control hardware: all the microprocessors. In a real hardware-in-the-loop system you basically have a big vehicle simulator, which is just big computer that runs in real time that you can plug all the vehicle computers into and run the simulations. You can perform tests as if you were actually running the vehicle. This is a process that is really cutting edge in the auto industry right now. GM utilizes it, and that’s why we thought it was really important to encourage it in EcoCAR. In Challenge X we always did model-based design using PSAT, which is the Powertrain System Analysis Toolkit, which is a product that Argonne National Laboratory actually built to sit on top of Simulink. But moving from that all the way to HIL which is great. [It represents] exactly what the students will do once they get into industry. It’s a lot safer for us to do thousands of hours of testing on the bench before we even get to turning on a vehicle.

Chambers: We’ve blown up thousands of $5000 engines…virtually.

Interview continued at “Do it right the first time–not necessarily good advice.”

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