Constrained Active Fault Tolerant Control Based on Active Fault Diagnosis and Interpolation Optimization

A new active fault tolerant control scheme based on active fault diagnosis is proposed to address the component/actuator faults for systems with state and input constraints. Firstly, the active fault diagnosis is composed of diagnostic observers, constant auxiliary signals, and separation hyperplanes, all of which are designed offline. In online applications, only a single diagnostic observer is activated to achieve fault detection and isolation. Compared with the traditional multi-observer parallel diagnosis methods, such a design is beneficial to improve the diagnostic efficiency. Secondly, the active fault tolerant control is composed of outer fault tolerant control, inner fault tolerant control and a linear-programming-based interpolation control algorithm. The inner fault tolerant control is determined offline and satisfies the prescribed optimal control performance requirement. The outer fault tolerant control is used to enlarge the feasible region, and it needs to be determined online together with the interpolation optimization. In online applications, the updated state estimates trigger the adjustment of the interpolation algorithm, which in turn enables control reconfiguration by implicitly optimizing the dynamic convex combination of outer fault tolerant control and inner fault tolerant control. This control scheme contributes to further reducing the computational effort of traditional constrained predictive fault tolerant control methods. In addition, each pair of inner fault tolerant control and diagnostic observer is designed integratedly to suppress the robust interaction influences between estimation error and control error. The soft constraint method is further integrated to handle some cases that lead to constraint violations. The effectiveness of these designs is finally validated by a case study of a wastewater treatment plant model.

Active fault-tolerant control system for a swash mass helicopter using back-stepping approach

In this article, an active fault-tolerant control system is designed and analyzed for a new model structure of unmanned aerial vehicles, which is referred to a swash mass helicopter. It consists of a double-blade coaxial shaft rotor for generating the necessary thrust and four masses that are located on the main body structure to maneuver the helicopter. The translational and rotational subsystems of the helicopter are highly coupled. Therefore, change of coordinate and feedback linearization methodologies are applied to address the problem and achieve the canonical form of the model. Next, actuator fault as a loss of effectiveness and bias faults are modeled for the dynamic. The main contribution of this article is to design an active fault-tolerant control system based on back-stepping and T-S fuzzy estimation methods for the swash mass helicopter which has never been designed in the last decades. T-S fuzzy methodology is responsible for obtaining the estimated value of the actuator faults during the flight. The Lyapunov theory illustrates that the proposed control strategy can stabilize the system despite the actuator’s fault. The simulation results show the effectiveness of the proposed scheme compared with another method.