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Ohio State University EcoCAR Improves Emissions Controls - The EcoCAR Spring Workshop

Wed, 03/30/2011 - 12:14pm
Eric Schacht
OSU vehicle arrivalThe Ohio State University EcoCAR team is one of 16 teams competing to build the best hybrid vehicle in the EcoCAR Challenge Competition. However, the EcoCAR Competition is not a simple “build the car and compete” type of competition. Each EcoCAR vehicle must undergo rigorous design analyses to prove its capabilities before building, and then the completed vehicles must pass rigorous technical inspections and on-road safety evaluations before the vehicles can even participate in events and testing. Because of these requirements, the vehicles were shipped to the EPA National Vehicle and Fuel Emissions Laboratory in Ann Arbor, Mich., for inspections and testing at a state-of-the-art facility. Here, the vehicles are fully inspected and given the opportunity to test emissions and fuel economy with the EPA’s equipment. With the test data and inspection results, the teams are given two months to make changes and repairs to arrive at competition in June ready to compete.

Team Preparation for Spring Workshop

The OSU team had quite a task to prepare the vehicle for the Spring Workshop and ultimately prepare for competition. The Spring Workshop is an opportunity for the organizers of the competition to inform the teams on competition events, preparation techniques, and various other tips and hits before the competition. This year, the workshop also included the vehicles for the pre-inspection and vehicle testing. The OSU team has been working to fine-tune the calibration of the E85 engine that provides range-extending hybrid operation for the vehicle. The team chose to use a 1.8L Honda CNG engine that offers a high 12.5:1 compression ratio and write the control software and calibrate it for E85. The task requires multiple graduate and undergraduate students doing thesis work, as well as typical volunteer team work, to achieve an engine capable of performing well in the OSU vehicle. The result is an engine that achieves a peak efficiency of 40.8 percent and averages 38-39 percent in the typical vehicle operation (as compared to traditional gasoline engines, which have peak efficiency of approximately 36 percent and average approximately 20-30 percent in typical operation). However, in order to achieve low emissions the team needed the valuable test data the EPA could offer to tweak the engine operation for both emissions and fuel consumption. The team added an electrically heated catalyst to reduce startup emissions and also designed the vehicle to have a single-speed gearbox for highway overdrive operation. These additional features further improve emissions and fuel consumption, but make the vehicle far more complex to control.

catalyst bench testThe team has been working on controls tuning on an engine dynamometer over the past two years, as well as conducting in-vehicle testing over the past few months. However, as the Spring Workshop approached, more work still needed to be done. The electrically heated catalyst needed to be integrated into the vehicle and tested, along with dynamic drive testing. Before testing on the vehicle, the team would check and tune software in the engine dynamometer; however, only two weeks before the vehicle ship date, the dynamometer engine failed. As a solution, the team developed an in-vehicle dynamometer mode using the dSPACE MicroAutoBox and its ControlDesk software, which allowed software and calibrations – originally designed and then automatically generated from MathWorks Simulink and Real-Time Workshop – to be tested before taking to the road.

During testing and tuning of the vehicle, the team also worked through a variety of technical inspection details, such as installing the interior of the vehicle around the 21 kWh of lithium iron phosphate batteries from A123 Systems. The team also worked to tie up wires to protect them from chaffing and moving components. Lastly, the team reviewed mechanical fasteners for lock washers and proper tightening to ensure everything on the vehicle was mounted securely.

Testing at Spring Workshop

The OSU vehicle arrived at the EPA safe and sound and passed through a preliminary technical inspection. OSU car on dynoThe team arrived and worked quickly to resolve issues seen by the technical inspectors, and it worked with inspectors to determine what issues might be resolved when the vehicle returned. With a quick completion of the inspection, the vehicle was moved into a four-wheel chassis dynamometer and the team began testing. The team developed test plans that would compare heating the catalyst to not heating it, as well as changes in drivability algorithms and idle speed, which would allow the team to make the best decisions possible on tradeoffs in energy, drivability, and emissions – or hopefully to tune and gain the best of all three. The initial results of testing revealed problems with idle emissions, startup emissions and the team’s engine throttle control. However, the results also showed the team was successfully controlling the engine under load and after warm-up achieving excellent emissions and fuel economy.

The Results

The team worked throughout the week at the EPA to improve the engine startup, electrically heated catalyst, and throttle control, of which showed issues early in the week. At the end of the week, a third and final set of tests showed a drastic improvement in throttle control and electrically heated catalyst. The team reduced the startup emissions by roughly 50 percent by improving the throttle control; and when compared to heating the catalyst, the team could reduce the startup emissions by another 80 percent. All of this shows the workshop provided a very valuable opportunity for testing and improvements. The OSU team will return to competition much more prepared after going through this process at the EPA.

ride and driveBefore returning home from the EPA earlier this month, the OSU vehicle participated in a media “ride and drive” event. The team demonstrated the vehicle for competition sponsors as well as various news outlets. The response was one of excitement for the technology and the vehicles on display. The OSU vehicle performed well, and the team plans to continue making the final touches on the vehicle and arrive at the competition in June prepared to find out who designed the best vehicle for the EcoCAR Challenge.

About the author
Eric Schacht is a graduate student at Ohio State University dedicated to the EcoCAR project. Mr. Schacht is the team leader managing or overseeing much of the vehicle design, construction and tuning to ensure the vehicle performs at its best for the final competition in June. He shares this leadership with John Kruckenberg, Beth Bezaire and a number of other team members that manage the subgroups such as emissions, controls, mechanical systems and engine control. He is currently pursuing a master’s degree in electrical engineering and writing a thesis on vehicle controls efficiency and drivability topics for the EcoCAR vehicle. 
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