The main focus lies on developing an applicable controller design method for automotive control problems. Automotive applications are characterised by a combination of the limited computational power of the car's on-board control unit and the nonlinear character of the systems to be controlled. Moreover, a required step in the development of series production controllers is the manual adaptation (calibration) of the controller parameters after the actual design. For this reason, the controller should provide tunable parameters. The parameters of the internal model of an IMC controller are chosen to serve for this purpose. Thus, IMC is proposed as the control structure.
The contribution of this thesis is two-fold. First, this work presents an IMC design procedure for nonlinear single-input, single-output systems. The nonlinear IMC, as proposed here, is based on the IMC structure known from linear systems and is based on a nonlinear feedforward control design. It is inversion-based and uses a low-pass state-variable filter which connects to the right inverse of the plant model to obtain a realisable IMC controller. Basic system properties, such as relative degree and internal dynamics, are exploited to extend the system class to stable and invertible plants. Input constraints and model singularities are taken into account by using a nonlinear low-pass filter that is made aware of the possible input/output behaviour of the model. This awareness is introduced by a model-dependent constraint of the filter's highest output derivative. The nonlinear IMC provides robust stability and robust tracking of the closed-loop system.
Second, the feasibility of this control scheme is presented. A single-input, single-output boost-pressure IMC controller is designed for a one-stage turbocharged diesel engine. The controlled plant was tested at the test bed and showed good results, surpassing the performance of the production PID-type controller. Two-stage turbocharging recently produced interest among car manufacturers and poses a challenging control problem due to the nonlinearity of the MIMO plant and a singularity of its inverse. This thesis presents the first model-based solution to this control problem. A multi-input, multi-output nonlinear IMC controller is designed and tested in simulations, showing good performance and robustness.
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