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The limiting values for NOx and HC concentrations in the exhaust gas of SI engines will be further lowered by legislation in many countries during the next years. This necessitates an improvement of the pollution control systems, which is achieved by including the dynamics of the three way catalyst into the control system. Before a control system can be designed, the dynamic behaviour of the exhaust after treatment system including the sensors has to be properly analyzed. As a first step a dynamic model of a solid-electrolyte oxygen sensor has been derived. It was the goal to obtain a better understanding of the cross sensitivities towards both reducing and oxidizing exhaust gas components such as H2, CO, O2 and NO. The model consists of three parts. Firstly, the porous protection layer, where only diffusion is assumed to occur, secondly the porous catalytic electrodes where the redox reactions take place and thirdly the solid electrolyte, where the electric potential is generated.

Based on an oxygen storage model of the three-way catalyst (TWC) an indirect adaptive control system is proposed. Utilizing a recursive Markov estimate method, the parameters involved in the model are identified on-line by measuring the upstream and downstream air-to-fuel ratios. These parameters are then used to estimate the relative oxygen level in the TWC which in turn is used as the control variable for the primary controller.

For a new concept of a hybrid drive line developed at the Swiss Federal Institute of Technology (ETH), a torque pedal interpretation for the accelerator pedal is investigated. For this purpose, based on a simple nonlinear model of the drive line, a robust nonlinear controller is developed. The controller consists of a nonlinear feedforward controller supported by a nonlinear estimator and a simple linear feedback controller. The robust performance of the control system developed is confirmed by simulations.

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.