Spacesamplingbased fault detection for nonlinear spatiotemporal dynamic systems with Markovian switching channel Abstract   This technical note is devoted to investigating the fault detection problem for a class of nonlinear spatiotemporal dynamic systems. Initially, by using sector nonlinearity approach, the considered nonlinear systems are represented by an Takagixe2x80x93Sugeno fuzzy model. Second, a new measure method, piecewise measure, is introduced to save the cost of system design. Furthermore, taking into account the switching network transmission channel, a modedependent asynchronous fuzzy diagnostic observer is constructed. Then, the sufficient conditions that guarantee the disturbancecontrolinputs robustness and fault sensitivity are established to optimize the fault detection systemxe2x80x99s performance. Finally, a practical application (cooling fin of a highspeed aerospace vehicle) is given to illustrate the effectiveness of the developed diagnostic observer design strategy.

On the need for switchedgain observers for nonmonotonic nonlinear systems Abstract   This paper focuses on the challenges in observer design for nonlinear systems which are nonmonotonic. A class of nonlinear systems is considered in which the process dynamics and output equations are both composed of nonlinear vector functions of scalar combinations of the states. The nonlinear functions are assumed to be differentiable with bounded derivatives. An observer design algorithm that requires solving just a single linear matrix inequality for exponentially convergent state estimation is developed. The developed algorithm works effectively when the involved nonlinear functions are monotonic. However, it fails when all or even some of the system functions are nonmonotonic. Both numerical computation and analytical results show that the observer design LMI has no feasible solutions when either all output functions or all process dynamics functions are nonmonotonic. Further, other constant gain LMIbased observer design methods from literature also fail when the involved nonlinear functions are all nonmonotonic, no matter how small the Lipschitz constant or the Jacobian bounds of the nonlinearities. This limitation has not previously been recognized in observer design literature. To overcome this limitation, a hybrid observer that switches between multiple constant observer gains is developed that can provide global asymptotic stability for systems with nonmonotonic nonlinear functions. Hybrid observers with switched gains enable existing observer design methods to be utilized for nonmonotonic nonlinear functions with finite local extrema. The application of the developed hybrid observer to two motion estimation applications, one a vehicle position tracking problem on roads and another a piston position estimation problem for an industrial actuator, are demonstrated.