SwRI-designed tool allows custom development and modification of engine control algorithms
Institute engineers have designed and built a unique engine control system that rapidly evaluates the complex control and diagnostic algorithms needed to test and modify engines under development. The flexible system is equally successful for gasoline, diesel, natural gas, and alcohol powered engines, as well as hybrid-powered engines and a variety of cylinder, ignition, and fuel-delivery configurations.
The Rapid Prototyping Engine Control System (RPECS) gives engineers a tool to effectively replace original equipment manufacturer (OEM) and off-the-shelf control systems. Calibrations can be adjusted in the latter two systems, but control algorithms are proprietary, making it impossible or expensive to test new engine control strategies.
Using a standard PC, custom hardware that includes an SwRI-designed engine controller card, and SwRI-copyrighted software, RPECS allows designers total control over all engine parameters, including fueling, ignition, exhaust gas recirculation, and idle air. In addition, RPECS allows engineers to quickly and efficiently modify algorithms when necessary.
"The system was originally funded under the Institute's internal research program to support a number of specific efforts," 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 anxious 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.
The RPECS team designed the system to be useful to clients with specific projects necessitating algorithm changes. 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.
The RPECS system is easy to use. The OEM control unit is replaced by an engine controller card (or multiple cards, depending on the number of cylinders) that 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.
Clients are supplied with a base code package in source format, so engine designers can modify the algorithms. They can change basic control configurations, such as number of cylinders, firing order, and other parameters, simply by entering numbers on an interface screen. Clients are also given a non-exclusive perpetual license for the system. At present, three manufacturers are applying RPECS to vehicle design efforts.
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 clients needs. Thus, additional capability is possible without extra design effort.
Published in the Fall 1995 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Joe Fohn.