Speed Control Integrated into the Powertrain Computer

Available computation time on an engine control microprocessor system provides a number of possibilities for addition of other vehicle control features. In General Motors 2.5 liter engine applications, vehicle speed control has been integrated into the engine control module. This provides additional features at a lower cost compared to current systems.

This paper discusses the logic of such a speed control system and some of the development techniques employed in implementation. Logic issues discussed include: basic control approaches, timing of calculations, and system enhancements due to available engine and transmission status. The inner and outer control loop characteristics affecting control stability will be reviewed with special interest. Potential future system enhancements will be examined. Finally, the development procedure for logic changes and calibration values will be discussed.