Incipient Actuator Faults Research Articles

Active Diagnosis of Incipient Actuator Faults for Stochastic Systems

In this paper, the active diagnosis problem of incipient actuator faults is investigated for a class of discrete-time stochastic systems. The input is exclusively designed for diagnosis purposes to optimally discriminate among multiple mode hypotheses that correspond to the multiple incipient actuator fault scenarios. Due to infeasibility in evaluating the misdiagnosis probability in the closed form, its new upper bound is derived as an alternative. It is proven that this upper bound is a tighter bound on the misdiagnosis probability for incipient actuator faults, compared with the widely used Bhattacharyya upper bound. For computation complexity reduction and diagnosis performance improvement purposes, a novel input design criterion is constructed for active fault diagnosis (AFD) based on the derived upper bound, under which the input design problem can be solved to global optimality. By injecting the optimal input, to fully utilize the diagnostically relevant information in the output data so as to draw a reliable diagnosis conclusion, the resulting measurement output sequence is exploited to make the AFD decision on the basis of the minimum misdiagnosis probability rule. Finally, experimental results on a four-tank system illustrate the effectiveness and superiority of the proposed AFD approach.

A generalized proportional‐integral observer for fault detection: An approximate input disturbance decoupling approach

SummaryThis article proposes a generalized PI observer with approximate disturbance decoupling (ADD‐GPIO) for detecting incipient actuator faults of a system subject to periodic input disturbances. Robustness to disturbances and sensitivity to faults is achieved through dynamic configuration of the disturbance transmission zeros and pole‐optimization respectively. By incorporating the ‐gap metric with index, a novel interpretable fault sensitivity optimization objective function is proposed. It is the first time in the fault detection observer design that the difference between the transfer function matrices (TFMs) relating fault detection residual to the disturbances and faults is quantified by the proposed ‐gap metric, which allows a more differentiated treatment of the disturbance and fault signals for better fault detection. Then, the optimal design of the ADD‐GPIO is modeled as a mixed‐integer optimization problem and the Lagrangian relaxation is adopted to find the near‐optimal parameters of the ADD‐GPIO at less computation costs in real application. Finally, both simulation and lab experiments of a two‐wheeled self‐balancing robot are carried out to validate the improved performance of the proposed method.

Integrated fault-tolerant control of a quadcopter UAV with incipient actuator faults

Integrated fault-tolerant control of a quadcopter UAV with incipient actuator faults

Distributed Fault-Tolerant Consensus Tracking Control of Multi-Agent Systems Under Fixed and Switching Topologies

This paper proposes a novel distributed fault-tolerant consensus tracking control design for multi-agent systems with abrupt and incipient actuator faults under fixed and switching topologies. The fault and state information of each individual agent is estimated by merging unknown input observer in the decentralized fault estimation hierarchy. Then, two kinds of distributed fault-tolerant consensus tracking control schemes with average dwelling time technique are developed to guarantee the mean-square exponential consensus convergence of multi-agent systems, respectively, on the basis of the relative neighboring output information as well as the estimated information in fault estimation. Simulation results demonstrate the effectiveness of the proposed fault-tolerant consensus tracking control algorithm.

Incipient Actuator Fault Handling in Nonlinear Model Predictive Control

This paper presents a reconfigurable nonlinear model predictive control (NMPC) scheme for handling of incipient actuator faults in nonlinear plants. The scheme seeks to ensure recoverability from an incipient actuator fault in plants where the input redundancy is insufficient to stabilize the faulty system at the nominal operating point, thereby requiring transition to a safe control-invariant set. To this end, the proposed scheme takes into account an estimate of the decrease in remaining actuator capacity from the time of detection of an incipient actuator fault, and minimizes the required control input to steer the plant to the safe set. We provide conditions for stability and fault recoverability of the proposed scheme, and demonstrate its applicability on a numerical example with two CSTRs in series.

Incipient fault diagnosis for T–S fuzzy systems with application to high‐speed railway traction devices

This study addresses the problem of incipient fault detection and diagnosis for Takagi–Sugeno (T–S) fuzzy systems and explores further results of total measurable fault information residual (ToMFIR). First, T–S fuzzy model is used to describe the global dynamics of a non-linear system and the model of incipient actuator faults is formalised. Second, based on the ToMFIR, a novel incipient fault detection method is proposed, which removes the assumptions on system structure in some existing work. Further, sliding-mode observers combined with ToMFIR-based thresholds are designed for incipient fault isolation. Finally, application results conducted on a high-speed railway traction device are given to illustrate the effectiveness of the proposed approach.

Incipient Fault Detection Using an Associated Adaptive and Sliding-Mode Observer for Quadrotor Helicopter Attitude Control Systems

An associated adaptive and sliding-mode observer (AASMO) design is proposed to detect and estimate the incipient actuator faults of a quadrotor. The incipient faults considered are physical structure aging and quadrotor leakage. First, disturbances and nonlinear parameters are considered in system formulation for a realistic mathematical model of the quadrotor. Its fault model is also introduced. Second, the decomposed subsystems are obtained through coordinate transformations to separate the incipient faults from the disturbances. For the subsystem with no disturbance, the adaptive observer can estimate the incipient faults. For the subsystem with disturbances, the sliding-mode observer has strong robustness against the disturbances. Dynamic error convergence and system stability can also be guaranteed by Lyapunov stability theory. Finally, the simulation results of quadrotor helicopter attitude systems validate the efficiency of the proposed AASMO-based incipient fault detection algorithm.

Proactive Actuator Fault-Tolerance in Economic MPC for Nonlinear Process Plants

This paper presents a scheme for proactive accommodation of incipient actuator faults in nonlinear process plants operated with economic model predictive control (EMPC). The control scheme implements a switching from nominal economic operations to a safe-transition mode when receiving a warning about an incipient fault in one of the actuators, thereby ensuring that the plant is proactively steered to a steady-state point where the suspect control actuator is inactive. Upon reaching this safe steady-state point, the faulty actuator can be safely disconnected and repaired without shutting down the plant, before the controller subsequently resumes nominal economic operation. To steer the plant to the safe steady-state point, we impose an l1 penalty function in order to achieve dead-beat control and reach the steady state in finite time. We provide a lower bound on the penalty parameter to ensure exactness of the penalty function, and analyze stability and convergence properties of the proactive fault-tolerant EMPC scheme. We demonstrate application of the proposed scheme on a non-isothermal continuously stirred tank reactor.

ToMFIR-based Detection and Estimation for Incipient Actuator Faults in a class of Closed-Loop Nonlinear Systems

Since incipient faults often have small amplitudes and obscure symptoms, those observer-based or output residual-based fault indicators are ineffective for incipient faults, especially in the presence of system disturbances. The ToMFIR-based fault detection approaches use both controller and output residuals to construct a fault indicator, which make them sensitive to incipient faults. This paper extends the ToMFIR-based fault detection approaches to a class of closed-loop nonlinear systems under the consideration of system disturbances. The restriction on the fault type is removed compared with the existing approaches, and ToMFIR-based fault estimation algorithm has been derived. Verification results in a near space hypersonic vehicle (NSHV) simulation system can demonstrate the effectiveness of the proposed approach.

Adaptive Monitoring and Accommodation of Nonlinear Actuator Faults in Positive Real Infinite Dimensional Systems

We consider a class of positive real infinite dimensional systems which are subjected to incipient actuator faults. The actuator fault is modeled as a time varying transition from an initial (linear or even nonlinear) map into another unknown nonlinear map at the onset of the fault occurrence. An infinite dimensional adaptive detection observer is utilized to generate a residual signal in order to detect the fault occurrence and to assist in the fault accommodation. This is done via an automated control reconfiguration which utilizes information on the new actuator map and adjusts the controller via a right inverse of the new actuator map. A robust modification is utilized in order to avoid false alarms caused by unmodeled dynamics. An example is included to illustrate the applicability of the proposed detection scheme.

Using unknown input observers for robust adaptive fault detection in vector second-order systems

The purpose of this manuscript is to construct natural observers for vector second-order systems by utilising unknown input observer (UIO) methods. This observer is subsequently used for a robust fault detection scheme and also as an adaptive detection scheme for a certain class of actuator faults wherein the time instance and characteristics of an incipient actuator fault are detected. Stability of the adaptive scheme is provided by a parameter-dependent Lyapunov function for second-order systems. Numerical example on a mechanical system describing an automobile suspension system is used to illustrate the theoretical results.