To fulfill ever increasingly stringent emission regulations, a great many studies on engine control and catalytic converter performance have been made. Topics of great interest in this area, to name a few, include: the relationship between catalyst light-off time and air-fuel (A/F) ratio; the relationship between forced A/F ratio modulation and catalyst efficiency; the effects of phase-shifted A/F ratio modulation between banks of a dual bank engine, or among cylinders of a single manifold engine on catalyst efficiency; and methods of modeling and measuring the oxygen storage capacity of a catalytic converter by rich-lean transition, A/F ratio sweeping, or other on-line estimation methods.
To undertake this type of research, an engine control system with necessary functions, especially with very flexible A/F ratio control capabilities, is needed. Mass production ECU does not provide the flexibility desired and it is also hard to develop and integrate the control algorithms needed for catalyst testing into the existing ECU software. An engine rapid control prototyping system is set up in an engine dynamometer test cell environment to overcome the limitations of mass production ECU and fulfill the requirements for catalyst research and testing. Model-based development methodology is adopted for the design and implementation of necessary software. Control algorithms, including individual bank control of a dual bank engine, A/F ratio modulation of different frequencies and amplitudes, with and without phase shift between banks, A/F ratio rich-lean transition and sweeping etc, are designed using graphical language, automatically converted into executables to run on the real-time target. UDP communication for real-time command and variable exchange between the engine controller and the test cell controller is developed to facilitate testing. The system provides the flexibility and good control performance desired for catalyst research and evaluation testing. Application and results of the system on a 4.6L V8 gasoline engine is given.