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This paper proposes two model-free sliding mode control system (MFSMCS) structures. The new structures are compared with a model-free intelligent proportional-integral (iPI) control system structure. Two simple design approaches for the MFSMCS structures are suggested. The control system structures and the design approaches are validated by a set of real-time experimental results on a nonlinear laboratory twin rotor aerodynamic system (TRAS). The MFSMCS structures are considered in the framework of a Multi Input-Multi Output TRAS control system, where the azimuth and pitch positions are controlled using separate Single Input-Single Output control system structures for each control channel (azimuth and pitch). The experimental validation is carried out by two scenarios that illustrate and allow the assessment of the MFSMCS structures performance and the comparison versus a model-free iPI control system structure as well. [ABSTRACT FROM AUTHOR]

This paper proposes a novel model-free trajectory tracking of multiple-input multiple-output (MIMO) systems by the combination of iterative learning control (ILC) and primitives. The optimal trajectory tracking solution is obtained in terms of previously learned solutions to simple tasks called primitives. The library of primitives that are stored in memory consists of pairs of reference input/controlled output signals. The reference input primitives are optimized in a model-free ILC framework without using knowledge of the controlled process. The guaranteed convergence of the learning scheme is built upon a model-free virtual reference feedback tuning design of the feedback decoupling controller. Each new complex trajectory to be tracked is decomposed into the output primitives regarded as basis functions. The optimal reference input for the control system to track the desired trajectory is next recomposed from the reference input primitives. This is advantageous because the optimal reference input is computed straightforward without the need to learn from repeated executions of the tracking task. In addition, the optimization problem specific to trajectory tracking of square MIMO systems is decomposed in a set of optimization problems assigned to each separate single-input single-output control channel that ensures a convenient model-free decoupling. The new model-free primitive-based ILC approach is capable of planning, reasoning, and learning. A case study dealing with the model-free control tuning for a nonlinear aerodynamic system is included to validate the new approach. The experimental results are given. [ABSTRACT FROM PUBLISHER]