Taking control of hybrids

  • 16-Aug-2013 02:23 EDT

Controls on Dana’s prototype hybrid loader determine whether the hybrid hydraulic system or the engine should power operations.

Ever-tightening fuel economy and emissions regulations are prompting many design teams to explore the benefits of hybrid technologies. Engineers are looking at controls and power electronics as they strive to trim costs and improve efficiency of these powertrain alternatives.

Improving controls can help developers reduce the size of batteries or hydraulic storage tanks, which translates to significant size and pricing gains. Turning to higher density electronics can also trim the cost of electronic control units. Many engineers agree that these controls are critical for the success or failure of hybrid vehicles.

“Controls are at the heart of the technology,” said George Constand, Chief Technical Officer at Dana. “We have a proprietary controller that has the ability to communicate with all the other ECUs on the vehicle. We work closely with our OEM partners to ensure that all the operations work together.”

When all operations work harmoniously, fuel savings can be significant. Control software and algorithms determine whether to use the conventional engine or hybrid alternatives to get the utmost efficiency.

“We use a high-level system manager that tells all the systems what to do,” said Gerard DeVito, Engineering Director for Eaton’s Hybrid Power Systems Division. “There are a lot of benefits. You can get more power density from motors and when the vehicle stops, you can turn the engine off and use the electric motors to start the motion.”

As hybrids become more sophisticated, they generally communicate more with multiple controls such as engine and hydraulic systems. That requires a good communications network as well as software that ensures close interactions so systems work together efficiently.

“Systems need to communicate so they accomplish all their goals,” said Mike Traver, Diesel Systems Business Unit Director for IAV Automotive Engineering. “You can’t have different systems fighting each other.”

The microcontrollers that handle communications and make decisions need to run at high speeds and have sufficient memory. Engineers are leveraging the advances made in the automotive industry, which has similar ruggedization requirements. That helps developers meet the performance requirements of off-highway operators.

“The controls provide very immediate feedback,” Constand said. “When power is needed, the controls immediately interact with the engine and interact with the hydraulic pumps and valves.”

In electric hybrids, controllers and networks aren’t the only critical devices. A range of power handling chips are also needed.

However, many of these parts haven’t been designed for rugged applications until recently, forcing engineers to develop alternative circuitry or add protective packaging. Over the past couple years, high voltage dc-dc and dc-ac converters have been undergoing a major transition. The power components used to convert high voltages such as the 340 V of some hybrids down to 12 V ac or dc for handhelds and other electronic tools are now available in ruggedized packages that can be used in off-highway vehicles.

“We’ve worked with suppliers to get them hardened, so now parts that weren’t available for harsh environments are shipping, which is really helpful in vehicles that need an auxiliary power generator,” DeVito said.

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