Dynamic-error-interval-based event-triggered adaptive fault-tolerant tracking control of uncertain nonlinear systems with actuator faults

This paper investigates the adaptive fault-tolerant tracking control of uncertain nonlinear systems with actuator faults. The considered faults are categorized into two types: partial loss of effectiveness and stuck faults. First, we design a novel interval to constrain the tracking error. More significantly, the proposed interval is dynamic and proven to be a subinterval of the existing static interval, thereby reducing the conservatism. Since the tracking error is employed in the virtual controller formulation, an interval transformation method is provided to remove the error constrained condition. This enhances the design flexibility of the controller. To attenuate the chattering induced by directly differentiating the virtual control signals (VCSs), a set of enhanced command filters is constructed. These filters process the VCSs and substitute their successive derivatives. Another key feature is the employment of continuous hyperbolic tangent functions in the filter design, replacing the conventional discontinuous sign functions, which means the chattering is further suppressed. Subsequently, a novel adaptive law with the event-triggered mechanism (ETM) is proposed for system uncertain parameter estimation and output regulation in the fault-free and faulty cases, which consequently meets the desired objective. The ETM is also proven to achieve a smaller number of triggers compared with the existing results. An example is provided to verify the effectiveness of the method.