The main contribution of this article is the proposal of a path-following method for fixed-wing unmanned aerial vehicles. This path-following method employs the multi-loop framework that consists of an outer guidance loop and an inner control loop. The guidance loop relies on the idea of tracking a virtual target. The virtual target is assumed to travel along the defined path and its speed is explicitly specified. This guidance law guarantees the asymptotic convergence to the desired path and can anticipate the transition of the flight path in advance, which reduces the command for the inner control loop. In the inner control loop, the flight control law based on dynamic surface control is derived to overcome the 'explosion of complexity' problem in the backstepping design. The numerical simulation result illustrates the effectiveness of the proposed method.

Aircraft fault detection and diagnosis (FDD) is a key technology to ensure flight safety. However, multiple simultaneous fault detection is still a difficult problem. To deal with it, a new FDD approach is proposed in this article, in which the expected-mode augmentation (EMA) approach is applied for the variable-structure interacting multiple model (VSIMM) estimation. The EMA approach is used for online model set adaption. In the EMA–VSIMM FDD approach, the failure model set is composed of a basic fixed model set and an adaptive EMA set. The EMA set is generated based on the basic fixed model set according to their predicted probabilities. Single or multiple simultaneous faults can be detected and diagnosed by applying the EMA set properly. The simulation results show that the EMA–VSIMM method is effective in detecting faults of various types and estimating unknown fault parameters.