Actuator Fault Estimation (FE) and Fault Tolerant Control (FTC) strategies designed with model-based observers for Vertical TakeOff and Landing (VTOL) aerial vehicles are proposed and validated experimentally in this paper. Three observers are considered for FE: a nonlinear adaptive observer and a linear Proportional-Integral Observer (PIO) applied to a Planar VTOL and a quasi-Linear Parameter Varying (qLPV) PIO applied to a quadcopter vehicle. The fault detection is done by comparing the fault estimation signal with a predefined threshold. Fault isolation is achieved by analyzing the sign of the fault estimation signal. The Available Control Authority Index (ACAI) method is used to analyze the controllability properties of the vehicles under actuator faults. The main contribution of this work is the design and the experimental validation of complete active FTC schemes by using the proposed FE systems in order to accommodate a soft actuator fault and reconfigure an aggressive fault, even when the vehicle is flying in a non-hover position. Finally, the proposed FTC schemes are validated in different cases of flight tests for illustrating the effectiveness of the strategies.
In this article, various investigations on soft exoskeletons are presented and their functional and structural characteristics are analyzed. The present work is oriented to the studies of the last decade and covers the upper and lower joints, specifically the shoulder, elbow, wrist, hand, hip, knee, and ankle. Its functionality, applicability, and main characteristics are exposed, such as degrees of freedom, force, actuators, power transmission methods, control systems, and sensors. The purpose of this work is to show the current trend in the development of soft exoskeletons, in addition to specifying the essential characteristics that must be considered in its design and the challenges that its construction implies.
In this paper an active fault tolerant control (AFTC) has been designed and applied to a 3‐DOF helicopter mathematical model. The main contribution corresponds to an AFTC design based on eigenstructure assignment aiming at reconfiguring the controller gain after actuator fault occurrences, modelled as additive faults. The reconfigured controller gain is computed ensuring the best approximation acquired for the nominal fault‐free closed‐loop system on its eigenstructure, giving rise to a faulty closed‐loop system with the same closed‐loop eigenvalues. Simulation results on the on‐line controller gain reconfiguration are shown considering simultaneous time‐varying faults and those with negative and positive slopes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.