Partial and total actuator faults accommodation for input-affine nonlinear process plants

Industrial & Engineering Chemistry Research, 2007

Most of the control schemes for chemical plants are developed under the assumption that the sensors and the actuators are free from faults. However, the occurrence of faults will cause degradation in the closed-loop performance, having an impact on safety, productivity, and plant economy. In this work, the main novelty is given by the enhancement produced through the integration of the fault detection and identification (FDI) system over a robust adaptive predictive control (RAPC) strategy specially thought to turn it as a faulttolerant control (FTC) scheme. Additionally, the FDI itself is original because of the sensor and actuator faults treatment. The biases in sensors are detected and quantified by using wavelet decomposition and the extra delays in actuators by applying online identification techniques to appropriately modify the controller action. It is important to remark that the extra time delay, detected particularly at the actuators, is a problem that occurs frequently in practice; however, the academic community has mostly omitted it up to now. This methodology can improve the overall performance for nonlinear stable plants because the FDI is specifically designed as a complement of those aspects that RAPC cannot handle at all. The control technique involves a commutation of a linear time-varying robust filter in the feedback path of the control loop in synchronization with an adaptive predictive controller. Through simulation studies of a continuous stirred tank reactor (CSTR) with jacket, where the integration between FDI and FTC has been implemented, it can be shown that the proposed methodology leads to significant improvement in comparison with the same control scheme without FDI, particularly when the fault magnitude increases.

International Journal of Robust and Nonlinear Control, 2022

In this paper, the fault-tolerant control (FTC) problem is investigated for a class of non-affine output-constrained multi-input multiple output (MIMO) nonlinear systems with actuator faults. The controlled systems contain unknown nonlinear functions, unknown external disturbance and immeasurable states. The fuzzy logic systems and a robust compensation function are employed to deal with the unknown nonlinear functions and non-affine nonlinear actuator fault problems. Then, the state observer and the nonlinear disturbance observer are developed for estimating the immeasurable states and unknown compounded disturbance, respectively. By using the barrier Lyapunov function method and in the unified framework of adaptive backstepping output feedback control design, a novel adaptive fuzzy fault-tolerant controller design scheme is developed. It is shown that all the variables of the closed-loop system are semi-globally uniformly bounded (SGUUB). Moreover, the system outputs cannot violate their predefined bounds in the presence of the non-affine nonlinear faults. A simulation is given to validate the effectiveness of the proposed approach.

2023

The adaptive fault tolerant control (FTC) problem is investigated for a class of high-order strict-feedback nonlinear systems with the actuator faults, and an adaptive fault tolerant control strategy is proposed in this paper. Compared with the traditional first-order strict-feedback nonlinear systems, high-order strict-feedback nonlinear systems are more general, but more difficult to handle. In particular, this system occurs actuator failure, which generates the additional terms. To address the unknown nonlinearities in the system, radial basis function neural networks are introduced to approximate the unknown continuous nonlinear functions. Based on Lyapunov stability theory, it is proved that the tracking error converges to a small adjustable neighborhood of the origin with all signals in the closed-loop system being bounded. Finally, a numerical example is used to verify the effectiveness of the control scheme proposed in this paper. INDEX TERMS High-order strict-feedback nonlinear systems, fault-tolerant control, adaptive control.

International Journal of Control, Automation and Systems, 2013

The goal of this paper is to describe a novel fault tolerant tracking control (FTTC) strategy based on robust fault estimation and compensation of simultaneous actuator and sensor faults. Within the framework of fault tolerant control (FTC) the challenge is to develop an FTTC design strategy for nonlinear systems to tolerate simultaneous actuator and sensor faults that have bounded first time derivatives. The main contribution of this paper is the proposal of a new architecture based on a combination of actuator and sensor Takagi-Sugeno (T-S) proportional state estimators augmented with proportional and integral feedback (PPI) fault estimators together with a T-S dynamic output feedback control (TSDOFC) capable of time-varying reference tracking. Within this architecture the design freedom for each of the T-S estimators and the control system are available separately with an important consequence on robust L 2 norm fault estimation and robust L 2 norm closed-loop tracking performance. The FTTC strategy is illustrated using a nonlinear inverted pendulum example with time-varying tracking of a moving linear position reference.

AIAA Guidance, Navigation and Control Conference and Exhibit, 2008

In this paper, the problem of controlling systems with failures and faults is introduced, and an overview of recent work on direct adaptive control for compensation of uncertain actuator failures is presented. Actuator failures may be characterized by some unknown system inputs being stuck at some unknown (fixed or varying) values at unknown time instants, that cannot be influenced by the control signals. The key task of adaptive compensation is to design the control signals in such a manner that the remaining actuators can automatically and seamlessly take over for the failed ones, and achieve desired stability and asymptotic tracking. A certain degree of redundancy is necessary to accomplish failure compensation. The objective of adaptive control design is to effectively use the available actuation redundancy to handle failures without the knowledge of the failure patterns, parameters, and time of occurrence. This is a challenging problem because failures introduce large uncertainties in the dynamic structure of the system, in addition to parametric uncertainties and unknown disturbances. The paper addresses some theoretical issues in adaptive actuator failure compensation: actuator failure modeling, redundant actuation requirements, plant-model matching, error system dynamics, adaptation laws, and stability, tracking, and performance analysis. Adaptive control designs can be shown to effectively handle uncertain actuator failures without explicit failure detection. Some open technical challenges and research problems in this important research area are discussed.

Proceedings of International Conference on Artificial Life and Robotics, 2022

This article deals with observer-based integrated robust fault estimation and accommodation design problems for nonlinear system. The environmental disturbance torque, actuator faults, sensor faults and model uncertainties are considered. Firstly, we propose the augmented fault estimation observer (AFEO) to guarantee the convergence of H∞ performance index of fault estimation and to restrict the influence of uncertainties with respect to the fault estimation error as well. We then design the fault accommodation which is based on the dynamic output feedback to keep the stability of the closed-loop system while malfunctioning. AFEO and dynamic output feedback fault tolerant controller (DOFFTC) are separately designed. Their performances are separately considered. Finally, we propose a simulation result of the micro-satellite attitude control system to demonstrate the effectiveness of the presenting method.

Biointerface Research in Applied Chemistry, 2021

Continuous Stirred Tank Reactor (CSTR) is an important system in the chemical and biological industries. It's characterized by a complex nonlinear behavior and is usually affected by faults and disturbances. Therefore, the states and faults estimation of a CSTR is always a challenging task for automated process researchers and engineers. This paper proposes an adaptive observer. This paper proposes an adaptive observer in order to estimate states and actuator and sensor faults simultaneously under unknown disturbance. Firstly, the approach of the Takagi-Sugeno multi-model is proposed to transform the complex nonlinear model into several simple linear sub-models. However, the states of the considered isotherm CSTR are not completely measurable, so the multi-model is represented with non-measurable premise variables. Then, in order to transform the considered system into a system with an unknown input, a mathematical transformation is introduced to describe the sensor faults as ac...

2010 Conference on Control and Fault-Tolerant Systems (SysTol), 2010

Two different schemes for Fault Tolerant Control (FTC) based on Adaptive Control, Robust Control and Linear Parameter Varying (LPV) systems are proposed. These schemes include a Model Reference Adaptive Controller for an LPV system (MRAC-LPV) and a Model Reference Adaptive Controller with a H ∞ Gain Scheduling Controller for an LPV system (MRAC-H ∞ GS-LPV). In order to compare the performance of these schemes, a Coupled-Tank system was used as testbed in which two different types of faults (abrupt and gradual) with different magnitudes and different operating points were simulated. Results showed that the use of a Robust Controller in combination with an Adaptive Controller for an LPV system improves the FTC schemes because this controller was Fault Tolerant against sensor fault and had an accommodation threshold for actuator fault magnitudes from 0 to 6.

IEEE Transactions on Automatic Control, 2006

This note investigates process fault accommodation in a class of nonlinear continuous-time systems. A new fault estimation module, based on an adaptive estimator, is first proposed. The fault tolerant controller is constructed to compensate for the effect of the faults by stabilizing the closed-loop system. A flexible joint robotic example is given to illustrate the efficiency of the proposed approach. Index Terms-Active fault-tolerant control (FTC), adaptive estimator, fault estimation, nonlinear continuous-time systems.

IFAC Proceedings Volumes, 2012

In this paper, three different types of faults (abrupt-additive, gradual-additive and multiplicative) are introduced to two new reconfigurable structures for Fault Tolerant Control (FTC) of a Single Input-Single Output (SISO) non-linear process. The first FTC structure, named MRAC-LPV, is based on an MRAC design using an LPV system, while the second FTC structure is based on an MRAC with a H ∞ Gain Scheduling Controller (MRAC-H ∞ GS-LPV) also designed by using an LPV system. Both MRAC controllers were implemented using the Lyapunov theory methodology because it guarantees the stability of the closed-loop system. The proposed schemes were tested using the nonlinear model of the system. To compare the performance of these schemes, a Coupled-Tank system is used as testbed in which the different types of faults with different magnitudes and different operating points were tested. Results showed that the use of an H ∞ Gain Scheduling Controller in combination with an MRAC improves the FTC performance because the controller was able to deal in an efficient manner with the faults and the changes in the operating points of the nonlinear model of the system.

2010

Abstract—This paper addresses a new methodology to con-struct a fault tolerant control (FTC) in order to compensate actuator faults in nonlinear systems. This approach is based on the representation of the nonlinear model with a multiple model under Takagi-Sugeno's form. The proposed control requires a simultaneous estimation of the system states and of the occurring actuator faults.

International Journal of Advanced Computer Science and Applications, 2019

In this paper, the basic theory of the model reference adaptive control design and issues of particular relevance to control nonlinear dynamic plants with a relative degree greater than or equal to one with unknown parameters are detailed. The studied analysis was motivated through its application to a robot manipulator with six degrees of freedom. After linearization using the input-output feedback linearization and decoupling algorithm, the nonlinear Multi-input Multioutput system was transformed into six independent single-input single-output linear subsystems each one has a relative degree equal to two, the obtained results in different simulations shows that the augmented reference model adaptive controller has been successfully implemented.

Complexity, 2018

This article deals with the sliding mode fault-tolerant control (FTC) problem for a nonlinear system described under Takagi-Sugeno (T-S) fuzzy representation. In particular, the nonlinear system is corrupted with multiplicative actuator faults, process faults, and uncertainties. We start by constructing the separated FTC design to ensure robust stability of the closed-loop nonlinear system. First, we propose to conceive an adaptive observer in order to estimate nonlinear system states, as well as robust multiplicative fault estimation. The novelty of the proposed approach is that the observer gains are obtained by solving the multiobjective linear matrix inequality (LMI) optimization problem. Second, an adaptive sliding mode controller is suggested to offer a solution to stabilize the closed-loop system despite the occurrence of real fault effects. Compared with the separated FTC, this paper provides an integrated sliding mode FTC in order to achieve an optimal robustness interactio...

International Journal of Automation and Computing, 2016

This paper presents a robust adaptive state feedback control scheme for a class of parametric-strict-feedback nonlinear systems in the presence of time varying actuator failures. The designed adaptive controller compensates a general class of actuator failures without any need for explicit fault detection. The parameters, times, and patterns of the considered failures are completely unknown. The proposed controller is constructed based on a backstepping design method. The global boundedness of all the closed-loop signals is guaranteed and the tracking error is proved to converge to a small neighborhood of the origin. The proposed approach is employed for a two-axis positioning stage system as well as an aircraft wing system. The simulation results show the correctness and effectiveness of the proposed robust adaptive actuator failure compensation approach.

2009

In this Faults or process failures may drastically change system behaviour leading to performance degradation and instability. The reliability and fault-tolerance of a control system can be achieved through the design of either an active or passive Fault Tolerant Control (FTC) scheme. This paper proposes a new approach to fault compensation for FTC using fault estimation by which the faults acting in a dynamical system are estimated and compensated within an adaptive control scheme with required stability and performance robustness. The FTC scheme has an augmented state observer (ASO) in the control system, which has an intrinsic robustness in terms of the stability and performance of the estimation error. The design concepts are illustrated using the notion that the friction forces in a mechanical system can be estimated and compensated to give good control performance and stability. The example given is that of a non-linear inverted pendulum with Stribeck friction.