By Jeff Meisel
Graphical system design tools help deliver hybrid vehicles to the masses.
Hybrid vehicles have officially arrived. Motivated by inflated gas prices and our nation’s dependence on non-renewable energy, key research and development (R&D) institutions have created technology that has advanced the adoption of hybrids in recent years.
Design labs at the “Big Three” U.S. automotive manufacturers — Ford, General Motors, and DaimlerChrysler — as well as those of their European and Asian counterparts, are all engaged in the R&D of hybrid technology.
Less obviously, R&D at leading academic institutions in the U.S. and Canada is playing a pivotal role in bringing hybrid vehicles to the masses. One venue is the 2005-2007 Challenge X Hybrid Vehicle Competition.
In this three-year competition, with headline sponsors including the U.S. Department of Energy, General Motors, and Argonne National Labs, 17 teams have been challenged to re-engineer a GM Equinox. The aim is to cut the crossover sport utility vehicle’s (SUV) fuel consumption and emissions of greenhouse gases while maintaining or exceeding the vehicle’s original utility and performance. Extensive resources of hardware, software, and training have been provided to the teams from platinum sponsors including Natural Resources Canada, The MathWorks, National Instruments,Freescale Semiconductor, AVL North America, Inc., U.S. Environmental Protection Agency, and the U.S. Department of Transportation.
Photo courtesy of Roy Feldman/Challenge X
> > This Virginia Tech hybrid vehicle competes at the GM Proving Grounds in Mesa, Arizona. A CompactRIO vehicle controller is embedded into the rear wheel well of the vehicle.
Designed to follow the actual vehicle development cycle at General Motors, the first year of the Challenge X competition focused on modeling, simulation, and testing of the vehicle powertrain and vehicle subsystems selected by each school. That stage was completed in the spring of 2005. Years two and three require the teams to develop and integrate their advanced powertrain and subsystems into a donated GM Equinox. For this integration stage, graphical system design tools such as NI LabVIEW help the teams to quickly design, prototype, and deploy their hybrid control systems and meet the requirements of the competition.
To appreciate the complexity that participating universities face in developing a near production-ready vehicle in only three years, consider how long it’s taken hybrid technology to gain commercial adoption. The timeline available here as a PDF file illustrates the road traveled by hybrid vehicles from the first modern-era introduction in 1972 to the present day.
As the timeline indicates, various government initiatives in the U.S. have driven the development of new hybrid technology within the Big Three, but it took Japanese manufacturers Toyota and Honda to get the first mass-produced vehicles to market. One lesson learned from the early generation hybrids of the late 1990s, is that both value and consumer perception play equally important parts in the mainstream adoption of hybrids. That is why Challenge X places an emphasis on minimizing energy consumption (value) while at the same time maintaining or exceeding the hybrid vehicle’s utility and performance when compared to similar non-hybrid vehicles (consumer perception).
Consider the real-world example in a case-study on how graphical system design tools successfully implemented the control strategy in a hybrid vehicle for Virginia Tech during the second year of the Challenge X competition.
Virginia Tech incorporated a graphical system design methodology to implement the control strategy of its split-parallel architecture hybrid vehicle. The graphical system design process, which can be broken down into three key areas (design, prototype, and deploy), allows engineering teams to quickly iterate on algorithms by focusing on the intellectual property (IP) of the system while shortening typical custom-embedded design development time and costs.
< < This figure shows a portion of LabVIEW code that reports data acquisition values of the Virginia Tech Hybrid Vehicle such as electric cooling, engine speed, braking, and clutch parameters, etc.
Let’s examine the three key areas in the context of Virginia Tech’s control strategy implementation. The end result of the process is a hybrid vehicle control system written in LabVIEW and implemented on an off-the-shelf platform such as CompactRIO from National Instruments (see figure above).
In the design stage, algorithms or logic are developed to accomplish a variety of math, control, filtering, or signal processing tasks. Additionally, modeling and simulation can be performed to iterate and tune the algorithms. For example, the Virginia Tech hybrid vehicle used an advanced feature of LabVIEW to incorporate control models from other tools such as Simulink from The MathWorks. This allowed a model to be imported that performed the control of the hybrid vehicle modes such as engine start and stop, and regenerative breaking with tests using Argonne National Laboratory’s Powertrain System Analysis Toolkit (PSAT).
> > LabVIEW graphical code is used to implement the hybrid vehicle control strategy with CompactRIO, which consists of a real-time processor and FPGA along with module I/O for rapid prototyping.
During the prototype stage, the simulated algorithms are verified using an off-the-shelf CompactRIO system from National Instruments, with a real-time (RT) processor and field programmable gate array (FPGA). Additionally, because LabVIEW was used to design the control strategy, low-level programming languages such as C or VHDL were not required to implement the system.
For final deployment, an off-the-shelf solution such as CompactRIO can be deployed in the final system or a custom hardware design can be developed. If a custom hardware design is developed, LabVIEW offers auto-code generation to create C code from LabVIEW algorithms for deployment to microprocessors or DSPs. As demonstrated in the hybrid, Virginia Tech deployed its control system running on CompactRIO in the rear wheel well of its modified Chevy Equinox.
< < This view of the Virginia Tech hybrid vehicle model illustrates the drive systems directed by the CompactRIO vehicle controller and its location in the vehicle’s rear wheel well.
The Virginia Tech team took First Place during Year 2 (Spring 2006) of the event, and cut the vehicle’s well-to-wheels petroleum use by 74% compared to a stock Equinox. (“Well-to-wheels” accounts for the consumption “upstream” in producing fuel from petroleum and is the standard metric used to compare hybrid vehicles using competing technologies.) The graphical system design approach using a high-level language such as LabVIEW with off-the-shelf hardware such as CompactRIO allowed for a rapid prototyping platform with enough horsepower and flexibility to accommodate changes in the overall vehicle control strategy.
> >This figure shows LabVIEW Real-Time code from the Virginia Tech Hybrid Vehicle running on the real-time processor of CompactRIO. A start command is provided to start the engine, and then various parameters are sent to the FPGA of the CompactRIO for communication over the GMLAN in-vehicle network.
“National Instruments software and hardware platforms for graphical system design give the competing Challenge X teams high-level tools,” said James B. Kolhoff, GM powertrain software engineering director,” allowing them to quickly design, prototype, and deploy innovative control strategies for new hybrid and fuel cell vehicles. In this research phase of development, the NI platform is being used to improve fuel efficiency and performance at a lower cost for future GM vehicles.” This design approach offers a glimpse of how automotive design engineers will help bring hybrid vehicles of the future to market via innovate control strategies.
Jeff Meisel is the product manager for LabVIEW Real-Time at National Instruments and serves as a technical judge for the Vehicle Development Review (VDR) of the Challenge X Hybrid Vehicle Competition. He may be contacted via e-mail at firstname.lastname@example.org Send your comments about this article through e-mail by clicking here. Please reference ” Hybrid Vehicle” in your message.
Challenge X Competition
General Motors, U.S. DOE