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In this paper, a decentralised tracking control based on extended linearisation techniques is presented for a two rotor laboratory helicopter with two degrees of freedom. Employing Lagrange's equations, a nonlinear control-oriented state-space model can be derived. It is rewritten in a quasi-linear form – without any simplifications – with state-dependent matrices as a basis for the decentralised feedforward and feedback control design. The control task consists in tracking accurately desired trajectories for both the azimuth angle and the pitch angle. Due to unmeasurable states as well as uncertainties stemming from both model simplifications at modelling and unknown disturbance torques, an unscented Kalman filter is employed and combined with a discrete-time implementation of the nonlinear control law. The eficiency of the proposed controller is demonstrated by results from an experimental set-up.

High-temperature fuel cells are promising devices to generate both electric energy and process heat in a decentralized energy supply grid. On the one hand, fuel cells have a relatively high eficiency concerning conversion of chemical energy. On the other hand, as far as solid oxide fuel cells (SOFCs) are concerned, they can also operate with a large variety of gas mixtures, involving hydrogen, methane, carbon monoxide, and carbon dioxide. This results from the fact that SOFCs are capable to perform an internal gas reformation. However, the variability of the required electric power — to be provided by the SOFC — leads to the necessity to develop reliable, real-time capable control strategies. In contrast to linear stateof-the-art approaches, these procedures should be applicable within wide ranges of operating temperatures. Moreover, the controllers have to be designed in such a way that they are robust against uncertain parameters and external disturbances. Finally, they have to guarantee that upper bounds for the admissible cell temperature are guaranteed not to be violated. For these reasons, this paper presents extensions of interval-based sliding mode controllers employing a novel barrier Lyapunov function technique. These controllers provide a way to consider one-sided state constraints as well as input and input rate constraints.

The basis for the design of real-time capable control and state estimation strategies for mechanical systems with distributed parameters is the derivation of suitable system models. These models lead to state-space representations that are, on the one hand, sufficiently accurate to capture the dominant features of the system dynamics. On the other hand, the dimensionality of these models has to be limited to a reasonable size to make sure that the resulting control and state estimation approaches can be implemented in real time. Therefore, a huge amount of work has been performed in recent years which is related to early lumping techniques. By using these techniques, the governing partial differential equations are replaced by sets of ordinary differential equations before the control and estimator design is performed. In this paper, both local and global approximations of the system dynamics are compared in simulations. These approximations are determined either by using a finite element representation that is based on the Method of Integrodifferential Relations (MIDR) or, alternatively, by a global Ritz ansatz. Especially the MIDR approach allows for the derivation of system models which exactly fulfill energy conservation laws as well as boundary and inter-element conditions.

A cascaded control strategy for an innovative Duocopter test rig - a helicopter with two rotors combined with a guiding mechanism - is presented in this paper. The guiding mechanism consists of a rocker arm with a sliding carriage that enforces a planar workspace of the Duocopter. The Duocopter is attached to the carriage by a rotary joint and offers 3 degrees of freedom. The derived system model has similarities with a PVTOL and a planar model of a quadrocopter but involves additional terms due to the guiding mechanism. In the paper, a model-based cascaded control strategy is proposed: in the outer MIMO control loop, sliding mode techniques are employed to control both the horizontal and the vertical Duocopter position. The rotation angle of the Duocopter is controlled in a linear inner control loop using flatness-based techniques. An additional feedforward control takes into account known parts of the coupling forces between the carriage and the rocker. The control structure is extended by an Unscented Kalman Filter (UKF) that provides estimates for the state vector and, moreover, estimates for remaining errors concerning the feedforward coupling forces. The sum of the feedforward part and the estimated part can be used to accurately compensate for the impact of the guiding mechanism on the motion of the Duocopter frame. Thereby, an excellent tracking performance in vertical and horizontal direction can be achieved. The efficiency of the proposed control strategy is demonstrated by experiments.