Southwest Research Institute^® (SwRI^®)  News

SwRI engineers develop an innovative engine control system

Unique engine control system rapidly adjusts algorithms for engines under development

San Antonio -- January 15, 1996 -- Engineers at Southwest Research Institute^® (SwRI^®)  have designed and built a unique engine control system that rapidly evaluates and adjusts the complex control and diagnostic algorithms needed to test and modify engines under development. The Rapid Prototyping Engine Control System (RPECS), which uses off-the shelf hardware and custom-built software, has proven equally successful for gasoline, diesel, natural gas, alcohol, and hybrid engines, as well as a variety of cylinder, ignition, and fuel-delivery configurations. RPECS provides engineers with an effective tool to replace original equipment manufacturer (OEM) and off-the-shelf control systems that are currently available. While calibrations can be adjusted in these systems, the algorithms are proprietary, making it expensive and often impossible to test new engine control strategies.

The system uses a standard PC, custom hardware that includes an SwRI-designed engine controller card, and SwRI-copyrighted software, and gives designers total control over all engine parameters, including fueling, ignition, exhaust gas recirculation, and idle air.

"RPECS was originally funded under the Institute's internal research program to support a number of specific engine projects," says Dr. Ken Shouse, senior research engineer and project manager. "These included SwRI-managed cooperative industry research programs such as the Ultra-Low Emissions Engine and Clean Heavy-Duty Diesel Engine programs, in which clients were eager to evaluate new design strategies to meet changing emissions requirements.

"Electronic engine control unit development has been driven by increasingly demanding emissions regulations," he adds. "Electronic engine controls were introduced in the late 1970s to improve performance and reduce emissions, but it was only in the 1980s, when emissions regulations could no longer be met with a mechanically controlled engine, that most large manufacturers moved to fuel injection systems that require electronic controls.

"Even large manufacturers that make their own controllers may find a use for the system," says Shouse, "because typically their own controllers are designed for mass production and are therefore more difficult to program than RPECS. In addition, there are a number of companies that make engines, but are not in the business of building engine controllers -- they rely on outside vendors. This tool can help them develop their own algorithms and their own engine control expertise." RPECS is easy to use. The OEM control unit is replaced by an engine controller card (or multiple cards, depending on the number of cylinders), which is inserted into a PC. The card contains a Silicon Systems integrated circuit that acts as an engine control chip and a specialized timer. The engineer programs the computer using the standard programming language C, and the chip transfers the instructions to the engine.

The RPECS system consists of the hardware required to control a port-injected eight-cylinder engine with waste-spark distributorless ignition, and up to 37 analog sensor inputs. The software provides for closed-loop fuel, ignition, idle-air, and exhaust gas recirculation control. An application-specific source code is included and is easily modified by the end user. The basic system costs $80,000; the purchase price includes one week of on-site engineering support, and one week of follow-up support by phone. More elaborate hardware and software are available at additional cost.

"The real value of the system," explains Shouse, "is that it consists primarily of off-the-shelf hardware, with a minimum of customized hardware and software tailored to the client's needs. Thus, additional capability is possible without extra design effort."

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