Advanced integrated Control and Monitoring of Actuation Systems

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Product quality and reliability continue to be amongst the top priorities of manufacturers, and these must be maintained in spite of the need for lower costs. The demands placed on equipment suppliers to assure quality and reliability of the products they produce is increasing. Advanced control combined with advanced condition monitoring are increasingly important and are becoming integral and essential elements of next generation products. Fault Detection and Diagnosis (FDD) and condition monitoring systems are instrumental to improving reliability in the context of manufacturing or operation of systems. The benefits of FDD systems for preventative unscheduled maintenance, for end-of-line production testing, and for potential advanced control to compensate for component degradations are huge. FDD strategies can be model-based or signal-based. Model-based strategies are very effective but are used for systems that can be mathematically modeled. For complex systems for which a meaningful mathematical model is either not available or cannot be derived, signal-based strategies have to be used. This proposal considers the combined application of signal-based and model-based strategies for the condition monitoring and FDD of actuation systems. Condition monitoring will feed into and provide information for the adaptive modification of an advanced feedforward robust control strategy for better performance and for degradation compensation. An Electro-Hydrostatic Actuation (EHA) system used in aerospace will be considered as the application domain in this research. Model-based condition monitoring use estimation strategies. The model-based strategy considered in this proposal will be based on the Smooth Variable Structure Filter (SVSF). The SVSF is a robust filter with features that are uniquely suitable for condition monitoring; it can better accommodate uncertainties due to fault conditions in the system that is being monitored both in terms of its performance and its stability. In general, real-world systems behave according to a number of different operating regimes (or modes). Operating modes can also imply fault conditions. A strategy that can track mode changes in dynamic systems is the Interacting Multiple Model (IMM) concept. As part of its implementation, the IMM requires an estimation strategy. In this research, a new derivation of the SVSF will be combined with IMM to track changes due to fault conditions as part of an enhanced condition monitoring and robust control strategy. For fault conditions that cannot be easily modeled and exhibit a periodic nature, a signal-based strategy will be used. The results from condition monitoring would feed into a robust sliding mode controller that would adapt its feedforward term according to the mode of the actuation system as determined by the above mentioned SVSF/IMM method. Robust refinement of the control input combined with condition monitoring are transformative to the actuation industry.