Design and Analysis of Event-Triggered Neuro-Adaptive Controller (ETNAC) for Uncertain Systems

In this paper, six new event-triggered neuro-adaptive control (ETNAC) schemes are presented for uncertain linear systems. Novelty of this paper lies in (i) the construction of the proposed ETNAC schemes, (ii) the design of event-triggering conditions, and (iii) the design of an observer called the modified state observer (MSO). In the proposed schemes, the MSO, the controller, and the event-triggering mechanisms are constructed and organized in a way such that they provide the control system designer with flexibility to choose between the one-way or two-way data exchange and also between the dynamic or static triggering conditions. The event-triggering conditions are designed on the basis of real performance parameters, such as the estimation/tracking errors that render control updates more on actual system events instead of the often-used extended time sampling. Another unique feature of ETNAC is its online uncertainty approximation capability even during inter-event times, which makes the controller robust and efficient. This part is developed with the help of an artificial neural network (ANN) and a polynomial regression-based MSO. The MSO formulations have two tunable gains, which allow fast uncertainty estimation without inducing high frequency oscillations, even while the system is in a transient state. Lyapunov analysis is used to show the stability of the system as well as to develop the event-triggering conditions. Effectiveness of the proposed controllers is demonstrated using benchmark numerical examples

Observer-based event-triggered and set-theoretic neuro-adaptive controls for constrained uncertain systems

In this study, several new observer-based event-triggered and set-theoretic control schemes are presented to advance the state of the art in neuro-adaptive controls. In the first part, six new event-triggered neuro-adaptive control (ETNAC) schemes are presented for uncertain linear systems. These comprehensive designs offer flexibility to choose a design depending upon system performance requirements. Stability proofs for each scheme are presented and their performance is analyzed using benchmark examples. In the second part, the scope of the ETNAC is extended to uncertain nonlinear systems. It is applied to a case of precision formation flight of the microsatellites at the Sun-Earth/Moon L1 libration point. This dynamic system is selected to evaluate the performance of the ETNAC techniques in a setting that is highly nonlinear and chaotic in nature. Moreover, factors like restricted controls, response to uncertainties and jittering makes the controller design even trickier for maintaining a tight formation precision. Lyapunov function-based stability analysis and numerical results are presented. Note that most real-world systems involve constraints due to hardware limitations, disturbances, uncertainties, nonlinearities, and cannot always be efficiently controlled by using linearized models. To address all these issues simultaneously, a barrier Lyapunov function-based control architecture called the segregated prescribed performance guaranteeing neuro-adaptive control is developed and tested for the constrained uncertain nonlinear systems, in the third part. It guarantees strict performance that can be independently prescribed for each individual state and/or error signal of the given system. Furthermore, the proposed technique can identify unknown dynamics/uncertainties online and provides a way to regulate the control input --Abstract, page iv