Advanced Control of Dual Redundant Electro-Hydrostatic Actuator

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Condition monitoring and fault tolerance are increasingly important and are becoming essential elements of next generation computerized systems. Next generation of products, such as future electric cars and aircraft, will more heavily rely on these concepts for their safety and reliability. This proposal makes three new related contributions that are: a new robust optimal filter as an integral element of model-based condition monitoring; use of this filter in a new form of fault tolerant control; and the application of these methods to a novel Electro-Hydrostatic Actuation System.****The new filter will be based on the Smooth Variable Structure Filter (SVSF) theory developed by the applicant. The SVSF is a robust filter that can be used for state and parameter estimation. It has features that are uniquely suitable for condition monitoring compared to other strategies such as the Kalman Filter; it can better accommodate uncertainties in the system that is being monitored both in terms of its performance and its stability. The SVSF uses the 1st order sliding mode condition to achieve robust stability and in its original form is not optimal. Under this proposal, a 2nd order SVSF based on the 2nd order sliding mode condition will be formulated with the objective of obtaining a filter that is both robust and optimal. This will constitute a substantive theoretical contribution to the field of filtering. ****In general, real-world systems behave according to a number of different operating regimes (or modes). 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 a filtering strategy. In this research, the 2nd order SVSF will be combined with IMM to track changes and hence fault conditions as part of an enhanced condition monitoring strategy. A closed loop control strategy will then be developed with a feedforward compensation term that is updated according to the system's mode of operation as identified by the IMM, as a new form of fault tolerant control.***These condition monitoring and control strategies will be applied and validated by using a new actuation system referred to as the Dual Redundant Electro-Hydrostatic Actuator (EHA). This actuator has the ability to mechanically reconfigure itself for fault tolerance and failure prevention by using custom designed components. The prototype of this system is in itself a novel contribution to the fluid power industry.**