Robust Fault Reconstruction Research Articles

Sampled-data sliding mode observer for robust fault reconstruction: A time-delay approach

A sliding mode observer in the presence of sampled output information and its application to robust fault reconstruction is studied. The observer is designed by using the delayed continuous-time representation of the sampled-data system, for which sufficient conditions are given in the form of linear matrix inequalities (LMIs) to guarantee the ultimate boundedness of the error dynamics. Though an ideal sliding motion cannot be achieved in the observer when the outputs are sampled, ultimately bounded solutions can be obtained provided the sampling frequency is fast enough. The bound on the solution is proportional to the sampling interval and the magnitude of the switching gain. The proposed observer design is applied to the problem of fault reconstruction under sampled outputs and system uncertainties. It is shown that actuator or sensor faults can be reconstructed reliably from the output error dynamics. An example of observer design for an inverted pendulum system is used to demonstrate the merit of the proposed methodology compared to existing sliding mode observer design approaches.

Robust Fault Reconstruction in Uncertain Linear Systems Using Multiple Sliding Mode Observers in Cascade

In observer-based fault reconstruction, one of the necessary conditions is that the first Markov parameter from the fault to the output must be full rank. This paper seeks to relax that requirement by using multiple sliding mode observers in cascade. Signals from an observer are used as the output of a fictitious system whose input is the fault. Another observer is then designed and implemented for the fictitious system. This process is repeated until the first Markov parameter of the fictitious system with respect to the fault is full rank. The result is that robust fault reconstruction can be carried out for a wider class of systems compared to other works that also seek to relax the requirement of a full rank first Markov parameter. In addition, this paper has also investigated and presented the necessary and sufficient conditions as easily testable conditions, and also the precise number of observers required. A simulation example verifies the effectiveness of the scheme.

Disturbance Decoupled Fault Reconstruction using Sliding Mode Observers

Abstract The objective of a robust fault reconstruction scheme is to generate an accurate reconstruction of the fault that is unaffected by disturbances. A typical method for robust fault reconstruction is to reconstruct the faults and disturbances, which is conservative and requires stringent conditions. This paper investigates and presents conditions that guarantee a fault reconstruction that rejects the effects of disturbances, which are less stringent than those of previous work. A VTOL aircraft model is used to validate the work of this paper.

Robust sensor fault reconstruction applied in real-time to an inverted pendulum

This paper presents robust sensor fault reconstruction applied in real-time to an inverted pendulum. A linear observer is used to generate an estimate of the system states. Then the state estimates, inputs and outputs are used to generate a reconstruction of the fault. The observer was designed in order to make the reconstructions robust to system disturbances arising from mismatches between the linear model and actual system. Two design methods were tested; Bounded Real Lemma and Right Eigenstructure Assignment. Both methods produced excellent real-time results where the reconstruction is visually identical to the fault.

FREQUENCY-WEIGHTED ROBUST FAULT RECONSTRUCTION USING A SLIDING MODE OBSERVER

This paper introduces a new method for the design of robust fault reconstruction filters. The method is based on shaping the map from disturbance inputs to the fault estimation error through frequency weighting functions and formulating the problem as a robust observer design where the input-output error map is minimized by solving a set of matrix inequalities. The authors consider a numerical example consisting of ten states, two known inputs, four measured outputs, one disturbance, and three faults. Through this example, they show that the frequency shaping renders far superior performance than existing conventional methods when properly incorporated in the observer design problem.