Jean Christophe Ponsart

Brief paper: Output feedback control of a class of stochastic hybrid systems

This paper deals with static output feedback control of a class of reconfigurable systems with Markovian Parameters and state-dependent noise. The main contribution is to formulate conditions for multi-performance design related to this class of stochastic hybrid systems. The specifications and objectives under consideration include stochastic stability, H2 and H~ performances. Another problem related to a more general class of stochastic hybrid systems, known as Markovian Jump Linear Systems (MJLS), is also addressed. This problem concerns the mode-independent output feedback control of MJLS. The obtained results are illustrated on a numerical example.

Robust Sensor Fault Estimation for Descriptor-LPV Systems with Unmeasurable Gain Scheduling Functions

Abstract This paper addresses the design of a state estimation and sensor fault detection, isolation and fault estimation observer for descriptor-linear parameter varying (D-LPV) systems. In contrast to where the scheduling functions depend on some measurable time varying state, the proposed method considers the scheduling function depending on an unmeasurable state vector. In order to isolate, detect and estimate sensor faults, an augmented system is constructed by considering faults to be auxiliary state vectors. An unknown input LPV observer is designed to estimate simultaneously system states and faults. Sufficient conditions to guarantee stability and robustness against the uncertainty provided by the unmeasurable scheduling functions and the influence of disturbances are synthesized via a linear matrix inequality (LMI) formulation by considering H∞ and Lyapunov approaches. The performances of the proposed method are illustrated through the application to an anaerobic bioreactor model.

H ∞ Stochastic Stabilization of Active Fault Tolerant Control Systems: Convex Approach

This paper deals with the problem of H<inf>∞</inf>and robust H<inf>∞</inf>control, via dynamic output feedback, of continuous time Active Fault Tolerant Control Systems with Markovian Parameters (AFTCSMP) subject to structured parameter uncertainties. The above problematic are addressed under a convex programming approach. Indeed, the fundamental tool in the analysis is an LMI (Linear Matrix Inequalities) characterization of dynamical compensators that stochastically (robustly) stabilize the closed loop system and ensure H<inf>∞</inf>and robust H<inf>∞</inf>constraints.

Output feedback robust control of uncertain active fault tolerant control systems via convex analysis

This paper deals with the problem of and robust control, via dynamic output feedback, of continuous time active fault tolerant control systems with Markovian parameters (AFTCSMP) subject to both structured and unstructured parameter uncertainties. The above problematic is addressed under a convex programming approach. Indeed, the fundamental tool in the analysis is a linear matrix inequalities (LMI) characterization of dynamical compensators that stochastically (robustly) stabilize the closed loop system and ensure and robust performances. Numerical examples are presented to illustrate the theoretical results.

Fault-tolerant control design with respect to actuator health degradation: An LMI approach

The active fault-tolerant control approach relies heavily on the occurred faults. In order to improve the safety of the reconfigurable system, a methodology to incorporate actuator health in the fault-tolerant control design is proposed for a tracking problem. Indeed, information about actuator health degradation due to the applied control is considered in addition to fault estimation. The main objective is to design a fault-tolerant control system which guarantees a high overall system reliability and dependability both in nominal operation and in the presence of faults. Such an objective is achieved by a control performance index, which is proposed based on system reliability analysis. The fault-tolerant controller is synthesized by using a linear matrix inequality approach.

Fault tolerance in networked control systems under intermittent observations

Fault tolerance in networked control systems under intermittent observations This paper presents an approach to fault tolerant control based on the sensor masking principle in the case of wireless networked control systems. With wireless transmission, packet losses act as sensor faults. In the presence of such faults, the faulty measurements corrupt directly the behaviour of closed-loop systems. Since the controller aims at cancelling the error between the measurement and its reference input, the real outputs will, in such a networked control system, deviate from the desired value and may drive the system to its physical limitations or even to instability. The proposed method facilitates fault compensation based on an interacting multiple model approach developed in the framework of channel errors or network congestion equivalent to multiple sensors failures. The interacting multiple model method involved in a networked control system provides simultaneously detection and isolation of on-line packet losses, and also performs a suitable state estimation. Based on particular knowledge of packet losses, sensor fault-tolerant controls are obtained by computing a new control law using fault-free estimation of the faulty element to avoid intermittent observations that might develop into failures and to minimize the effects on system performance and safety.

A virtual actuator approach for the fault tolerant control of unstable linear systems subject to actuator saturation and fault isolation delay

This paper presents a fault tolerant control (FTC) strategy for unstable linear systems subject to actuator saturation and fault isolation delay. The solution relies on virtual actuators, an active fault-hiding method that reconfigures the faulty plant instead of the controller. The main contribution of the paper consists in the design of the virtual actuators with guarantees that, if at the fault isolation time the closed-loop system state is inside a region defined by a value of the Lyapunov function, the state trajectory will converge to zero despite the appearance of faults within a predefined set. In addition, the design of the nominal controller is performed so as to maximize the tolerated delay between the fault occurence and its isolation. Finally, the theoretical results are demonstrated and illustrated using an example.

Output-feedback H ∞ control of a class of networked fault tolerant control systems

This paper deals with static output feedback Hinfin control of a class of discrete-time networked control systems (NCSs) subject to random failures and random delays. The different random processes are modeled as Markovian chains, and the resulting closed-loop system belongs to the class of discrete-time Markovian jump linear systems (MJLS). For synthesis purposes, we adopt a new framework, based on the synthesis of ellipsoidal sets of controllers. Results are formulated as matrix inequalities. A numerical algorithm based on nonconvex optimization is provided and its running is illustrated on a classical example from literature.

Sensor Fault Diagnosis and Accommodation Based on Analytical Redundancy: Application to a Three-Tank System

Abstract In this paper, a sensor fault accommodation method is developed. This method makes possible the compensation of additive or multiplicative sensor faults and failures. Its principle is based on the on-line detection, localization and estimation of the faulty element when a fault occurs on the system. Then, a new control law is computed in order to compensate the fault effect on the system. The performances of the method are tested in simulation on a pilot plant.

Static Output-Feedback H α Control of a Class of Stochastic Hybrid Systems with Wiener Process

This paper deals with static output feedback Hα control of continuous time active fault tolerant control systems with Markovian parameters (AFTCSMP) and state-dependent noise. It adopts a new framework, based on the synthesis of ellipsoidal sets of controllers. It is also shown that the obtained results can easily be applied to the problematic of mode-independent static output feedback Halpha control of another class of stochastic hybrid systems known as Markovian jump linear systems. Results are formulated as matrix inequalities one of which is nonlinear. A numerical algorithm based on nonconvex optimization is provided and its running is illustrated on classical examples from literature.