Presence Of Actuator Faults Research Articles

Multimodel-based flight control system reconfiguration control in the presence of input constraints

In this paper, a new active fault tolerant control strategy is proposed for the plant in the presence of actuator fault and input constraints, which is a combination of a direct adaptive control algorithm with multiple model switching, and the µ-modification is introduced in the model reference control architecture. Based on Lyapunov-Krasovskii stability theory, the stability of overall system is guaranteed and the boundedness of all signals is ensured, while appropriate switching of the multiple models ensures asymptotic tracking for the system states. Simulation results are presented to illustrate the efficiency of the developed fault-tolerant control approach.

Team Consensus for a Network of Unmanned Vehicles in Presence of Actuator Faults

In this paper, performance analysis of a team of unmanned vehicles (agents) that are subject to actuator faults is investigated. The team goal is to accomplish a cohesive motion in a modified leader-follower architecture by using a semi-decentralized optimal control strategy. The controller, which is recently proposed by the authors, is designed based on minimization of individual cost functions by using the available information from the neighboring sets. It is shown that a loss of effectiveness (LOE) fault in an actuator does not deteriorate the stability nor the consensus seeking goal of the team. This fault would only result in a different transient behavior, e.g., a change in the agent's convergence rate, without a change in the consensus value. On the other hand, if the fault in one or more of the agents is of the float type, either in the leader or the followers, the team could not maintain its consensus any longer, however the stability of the team can still be guaranteed. Moreover, the leader and the healthy followers adapt themselves to the follower's change when a float fault occurs in one of the agents. Finally, the behavior of the team in presence of the lock-in-place (LIP) actuator fault is also investigated. Simulation results are provided to demonstrate the performance of the team subject to the above three actuator fault scenarios.

Fault-tolerant control scheme for satellite attitude control system

A sliding mode control scheme with finite reaching time is proposed for a fault-tolerant satellite attitude control system in the presence of actuator faults and external disturbances. The actuator fault is modelled to reflect the degradation of the actuation effectiveness, and the solar array induced disturbance is considered as external disturbance. The control scheme is designed to perform the rest-to-rest manoeuvre of a satellite system with the degradation of the actuation effectiveness, and the stability analysis is performed using the Lyapunov theorem. Numerical simulations are conducted and the results are compared to verify the performance of the proposed fault-tolerant control scheme.

FAULT-TOLERANT SYNCHRONIZED MOTION CONTROL FOR CRANE SYSTEM USING WIRELESS SENSOR NETWORKS

This paper presents a fault-tolerant control strategy to accommodate faulty actuators in a crane system using wireless communications. The proposed control system contains several intelligent nodes which are interconnected by a wireless sensor network. A time-triggered protocol implemented on top of IEEE802.15.4 is employed to avoid the problems with randomly varying message latency and the “hidden terminal.” The reconfiguration strategy to tolerate faulty actuators is based on an IMC-PID controller of which parameters are adjusted online through an iterative optimization process using the diagnostic information being generated by smart actuators. The effectiveness of the proposed approach in the presence of actuator fault is demonstrated using a DC-motor based experimental system.

Fault‐tolerant control synthesis for a class of nonlinear systems: Sum of squares optimization approach

AbstractThis paper studies the fault‐tolerant control (FTC) problem for nonlinear systems, with guaranteed cost or H∞ performance objective in the presence of actuator faults. The faulty mode is built as a multi‐model framework of the typical aberration in actuator effectiveness. The novelty of this paper is that the effect of the nonlinear terms is described as an index in order to transform the FTC design problem into a semi‐definite programming. The proposed optimization approach is to find zero optimum for this index. Combined with other performance indexes, the conceived multi‐objective optimization problem is solved by using sum of squares method in a reliable and efficient manner. Numerical examples are included to verify the applicability of this new approach for the nonlinear FTC synthesis. Copyright © 2008 John Wiley & Sons, Ltd.

FAULT TOLERANT HYBRID MPC APPLIED ON SEWER NETWORKS1

In this paper, fault tolerant hybrid model predictive control (HMPC) for sewer networks is introduced. A hybrid model of the sewer system is presented which allows capturing inherent phenomena such as tank and collector overflows that are not always present but depend on the system state. Constraints due to actuator faults can be expressed in the same modelling framework. The model is used for predictive control to reduce combined sewer overflows (CSO) and pollution even in the presence of actuator faults. A simulation study is presented where fault tolerant control strategies are compared and analyzed for real rain scenarios.

Fault Diagnosis and Reconfigurable Control of a Pressurizer in a Nuclear Power Plant

In this paper, an integrated approach to the design of fault diagnosis and reconfigurable fault-tolerant control system against actuator and sensor faults in a nuclear power plant pressurizer is proposed. The scheme uses a reconfigurable proportional-integral (PI) control structure and a setpoint adjustment technique to achieve required performance at both the dynamic and steady-state conditions. A singular value decomposition (SVD) based eigenstructure assignment (EA) technique is used to achieve on-line automatic redesign of the controller. Fault diagnosis and controller reconfiguration mechanisms are carried out using statistical hypothesis tests based on the information from a two stage adaptive Kalman filter. The proposed approach has been evaluated under different type of Unanticipated actuator faults: e.g. abrupt and incipient faults; total and partial faults; single, multiple and consecutive faults under both set-point regulation and set-point tracking. Through set-point tracking, specified performance degradation in the presence of actuator fault. can be eexplicitly considered. Detection and isolation of sensor faults are achieved by voting among outputs from several hardware redundant sensors. The effectiveness of the approach is demonstrated via simulation using a pressurizer model.

Actuator fault detection and isolation in linear systems

A scheme for the detection and isolation of actuator faults in linear systems is proposed. A bank of unknown input observers is constructed to generate residual signals which will deviate in characteristic ways in the presence of actuator faults. Residual signals are unaffected by the unknown inputs acting on the system and this decreases the false alarm and miss probabilities. The results are illustrated through a simulation study of actuator fault detection and isolation in a pilot plant doubleeffect evaporator.