Mathematical modeling and nonlinear control of electrohydraulic and electrorheological systems

This thesis is concerned with the mathematical modeling, the analysis and the nonlinear controller design for electrohydraulic and electrorheological systems. In the first part of this work the mathematical models of the systems under consideration are derived whereby a special focus is laid on a consistent physical formulation. In the second part an energy-based position control strategy for electrohydraulic linear actuators is developed. Afterwards, the work deals with the impedance control task for electrohydraulic systems. Therein it is shown that the demands on the energetic efficiency of the impedance system can only be reached if, in addition to a suitable nonlinear controller design, the construction of the system is adapted. In contrast to electrohydraulic systems where an electromagnetic actuator is used for the control, the rheological behavior (e. g. the apparent viscosity) of the fluid can be directly controlled in electrorheological systems by applying a sufficient large electric field. In this work the position control task for an electrorheological actuator is considered. Here it is elaborated that due to the significant different construction of electrorheological actuators compared to electrohydraulic actuators, special controller strategies are demanded. Finally, in the last part it is shown that the nonlinear controller design methods proposed in this thesis based on a physical consistent mathematical modeling and a detailed analysis can also be applied to a more complex practical application, namely an electrohydraulic power steering system. In all parts of this work, the feasibility and the performance of the proposed control strategies are demonstrated by means of simulation and/or measurement results. Finally, the work is concluded by a summary and a short outlook to future research activities.