Fault Detection and Isolation of Nonlinear Systems: An Unknown Input Observer Approach With Sum-of-Squares Techniques

[[abstract]]This paper presents a novel nonlinear unknown input observer (UIO) design method for fault detection and isolation (FDI) of a class of nonlinear affine systems. By using sum-of-squares (SOS) theory and Lie geometry as the main tools, we demonstrate how to relax the rank constraint in the traditional UIO approach and simplify the design procedure, especially for the polynomial nonlinear systems. Meanwhile, we show that the detection and isolation thresholds based on the L-2 gains can be easily obtained via optimization formulated in terms of SOS. Simulation examples are given to illustrate the design procedure and the advantages. [DOI: 10.1115/1.4006074][[note]]SC

Consensus of multi-agent systems with general linear dynamics via dynamic output feedback control

[[abstract]]This study addresses consensus problems of multi-agent systems (MASs) using dynamic output feedback control under both fixed and switching topologies. We aim to exploit the information structure for the consensusability of MASs. Necessary and sufficient conditions are presented in terms of detectability and stabilisability of the agents, graph topology, and some matrix inequality constraints. These conditions explicitly reveal how consensusability is affected by the intrinsic dynamics of the agents, the communication topology and available information. In addition, this paper provides several constructive procedures for protocol design to achieve consensus, and establishes the so-called separation principle, which simplifies the design procedure greatly.[[note]]SC

Proportional Navigation With Delayed Line-of-Sight Rate

[[abstract]]This brief discusses the convergence analysis of proportional navigation (PN) guidance law in the presence of delayed line-of-sight (LOS) rate information. The delay in the LOS rate is introduced by the missile guidance system that uses a low cost sensor to obtain LOS rate information by image processing techniques. A Lyapunov-like function is used to analyze the convergence of the delay differential equation (DDE) governing the evolution of the LOS rate. The time-to-go until which decreasing behaviour of the Lyapunov-like function can be guaranteed is obtained. Conditions on the delay for finite time convergence of the LOS rate are presented for the linearized engagement equation. It is observed that in the presence of line-of-sight rate delay, increasing the effective navigation constant of the PN guidance law deteriorates its performance. Numerical simulations are presented to validate the results.[[note]]SC