Engine Torque Control Variation Analysis 2008-01-1016

The growing complexity of engine control systems and integration with transmission and vehicle dynamics controls systems have lead to the use of torque-based engine control. Torque-based control enables flexibility and expandability of the powertrain control system structure. It allows various engine actuation technologies (active fuel management (AFM), cam phasing, supercharger, etc.) to be easily incorporated, and to enable a simpler control structure than current production controls. Torque-based control structure is developed to coordinate and achieve better engine, transmission, hybrid, and vehicle dynamics controls.

This paper describes the role of Engine Torque Control in a torque-based control system. It gives an overview of Engine Torque Control architecture with main elements, and discusses control system requirements. Engine Torque Control performance, defined by the engine torque transient response, has direct impact on qualities of torque based control, such as vehicle response, drivability and fuel economy. The engine torque transient response must be independent of control system, plant, and environmental variations. An accurate plant model of a powertrain system has been developed, presented, and tuned with a development vehicle data. This model is used to study the influence of parameter variation on the control system. The Engine Torque Control algorithm model used for Rapid-Prototyping Controls is connected with the powertrain plant model through a control interface model.

This paper characterizes an Engine Torque Control transient response in terms of classical control theory metrics such as overshoot, steady state error, and response time. The influence of both environmental and system parameters on the control system transient response characteristics is considered. The parameter variation and simulation Design of Experiment (DOE) runs were chosen by control design team and torque control experts. The torque response data collected on development vehicle is used to verify integrity of the simulation results. This paper provides simulation results illustrating how transient torque response performance is a function of system variations.