1993-03-01

Model-Based Multivariable Speed and Air-to-Fuel Ratio Control of an Sl Engine 930859

In conventional engine control typically several heuristic controllers influence each other. To avoid the inherent conflicts, the following concept is investigated:A single model-based multivariable controller is used to control speed and air-to-fuel ratio simultaneously. The dynamic compensator is always in the loop. Thus, the stability of the system is not compromised by a change of structure.The commanded throttle position is now an output of the compensator. Therefore, an interpretation of the position of the accelerator is used to obtain the speed setpoint of the multivariable controller (“fly-by-wire”). The position of the driver pedal is interpreted as a desired acceleration of the vehicle.To increase the bandwidth of the control system, a feed-forward is introduced. The feed-forward for the throttle setpoint is a function of the speed setpoint. Feed-forward does not change any stability characteristics.Implementing this concept on a dynamic test bench shows the possibility for following the highest acceleration which occurs in the FTP cycle within the given tolerances.

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