Mohamed Tadjine

Adaptive sensor-fault tolerant control for a class of multivariable uncertain nonlinear systems

This paper deals with the active fault tolerant control (AFTC) problem for a class of multiple-input multiple-output (MIMO) uncertain nonlinear systems subject to sensor faults and external disturbances. The proposed AFTC method can tolerate three additive (bias, drift and loss of accuracy) and one multiplicative (loss of effectiveness) sensor faults. By employing backstepping technique, a novel adaptive backstepping-based AFTC scheme is developed using the fact that sensor faults and system uncertainties (including external disturbances and unexpected nonlinear functions caused by sensor faults) can be on-line estimated and compensated via robust adaptive schemes. The stability analysis of the closed-loop system is rigorously proven using a Lyapunov approach. The effectiveness of the proposed controller is illustrated by two simulation examples.

Adaptive sensor-fault tolerant control for a class of MIMO uncertain nonlinear systems: Adaptive nonlinear filter-based dynamic surface control

Abstract This paper presents an adaptive fault tolerant control (FTC) scheme for a class of multiple-input multiple-output (MIMO) nonlinear systems against sensor faults, modeling errors and external disturbances. Four kinds of sensor faults including bias, drift, loss of accuracy and loss of effectiveness can be tolerated by the proposed FTC system. Within this scheme, dynamic surface control (DSC) technique, robust adaptation laws and adaptive nonlinear filters are combined for designing an adaptive dynamic surface control (ADSC)-based FTC system in order to compensate for the effects of sensor faults and system uncertainties (including external disturbances, modeling errors and unexpected nonlinear functions caused by sensor faults). Lyapunov approach is used to prove that all the signals in the closed-loop system are bounded and the tracking-errors can be forced to converge into a small neighborhood of zero. The feasibility and the effectiveness of the proposed FTC controller are demonstrated through two simulation examples.

Vector fault tolerant control of induction motor drives subject to stator interturn faults

The paper describes a vector fault tolerant control of squirrel cage induction machines (IM). The field oriented control (FOC) was combined to robust sliding mode control (SMC). This last is a technique to adjust feedback by previously defining a surface. The controlled state variables will be forced to move on this surface, then the behavior of the machine slides to the desired equilibrium point. We have taken the stator interturn fault, which is the most frequently encountered in practice. An analytical method for the modelling of this fault has been presented including space harmonics effect. This method is based on the calculation of the magnetic field distribution through the machine air-gap. The obtained model is less complicated to be implemented for condition monitoring or to validate fault tolerant control algorithms. Simulation results show, on the one hand that the proposed control scheme provides highperformance dynamic characteristics, and on the other hand the applicability and the tolerance of this control.

Sensorless vector controlled induction motors using adaptive observation

This paper presents the synthesis of an adaptive observer which is used for the improvement of the Direct Field Oriented Control (DFOC) of induction motor drives. The observer detects the rotor flux components in the stationary reference frame and the rotor speed using the measure of the stator terminal voltages and currents. The observer is adapted using a simple algorithm which does not imply a high computational load. Stability analysis based on Lyapunov theory is performed in order to guarantee the closed loop stability. Simulation tests under disturbances are provided to evaluate the consistency of the proposed control technique.

Diagnosis of cage induction motors subject to unbalanced supply voltage conditions including space and time harmonics

The paper describes an analytical method which is developed for the modeling of cage induction motors (IM) including space and time harmonics effects. This model is used to predict the influence of these harmonics on the electromagnetic performances of IM drives in healthy condition and to extract significant signatures under faulty conditions such as unbalanced supply voltage. The equations which describe the transient as well as steady state behavior including the computation of machine inductances are presented, basing on the calculation of the magnetic field distribution through the machine air-gap. The proposed model is less complicated to be implemented for condition monitoring or control of IM drives. The simulation results provide useful consequences about the characteristics of the IM under unbalanced voltage conditions including space and time harmonics effects. It will be shown that the space and time harmonics influence significantly the harmonic content of the electromagnetic torque and stator currents which are used for condition monitoring of IM drives.

Composite adaptive dynamic surface control of nonlinear systems in parametric strict-feedback form:

In this paper, a composite adaptive dynamic surface control scheme is developed for a class of parametric strict-feedback nonlinear systems. The proposed composite adaptation law uses both the surface error and the estimation error to update the parameters. In addition, by using the dynamic surface control technique, the problem of the explosion of complexity in the adaptive backstepping design is avoided. It is proved that the proposed scheme guarantees uniform ultimate boundedness of all signals in the closed-loop system with arbitrary small surface error by adjusting the design parameters. Simulation results demonstrate the effectiveness of the proposed approach for an electrohydraulic actuator system.

Global stability analysis and optimal control therapy of blood cell production process (hematopoiesis) in acute myeloid leukemia

In this paper we analyze the global stability of a coupled model for Acute Myeloid Leukemia and propose a therapy approach based on an optimal control strategy. Firstly, based on the positivity of the model, stability of trivial solutions for healthy and cancerous cell subsystems is assessed. To this end we use new Lyapunov functionals and take into account the interconnection between cell populations. Secondly, stability conditions for healthy situation in interconnected model are established by using Nyquist criterion. And thirdly, we design an optimal control based therapy that aims to eradicate cancerous cells and minimize the side effects of the treatment on healthy ones. After showing the existence of an optimal control, this one is determined by using Pontriagyns principal. We assess the effect of interconnection between healthy and cancerous cells on their dynamics and on the stability conditions for different cases. The behavior of the system in open loop and with application of the optimal control therapy is illustrated by simulation and results are biologically explained and motivated.

COMPARATIVE STUDY OF NON-LINEAR CONTROLLERS FOR THE REGULATION OF THE PARAPLEGIC KNEE MOVEMENT USING FUNCTIONAL ELECTRICAL STIMULATION

The non-idealities resulting from the excitation of the paraplegic quadriceps muscle by the functional electrical stimulation (FES) make the control problem challenging. Few works addressed the con...

Adaptive sensor fault-tolerant control for a class of multi-input multi-output nonlinear systems: Adaptive first-order filter-based dynamic surface control approach

This paper is concerned with the adaptive fault-tolerant control (FTC) problem for a class of multivariable nonlinear systems with external disturbances, modeling errors and time-varying sensor faults. The bias, drift, loss of accuracy and loss of effectiveness faults can be effectively accommodated by this scheme. The dynamic surface control (DSC) technique and adaptive first-order filters are brought together to design an adaptive FTC scheme which can reduce significantly the computational burden and improve further the control performance. The adaptation laws are constructed using novel low-pass filter based modification terms which enable under high learning or modification gains to achieve robust, fast and high-accuracy estimation without incurring undesired high-frequency oscillations. It is proved that all signals in the closed-loop system are uniformly ultimately bounded and the tracking-errors can be made arbitrary close to zero. Simulation results are provided to verify the effectiveness and superiority of the proposed FTC method.

A preliminary study on integrating operation flexibility within semi-heterarchical FMS control

This study aims to analyze the integration of operation flexibility (OF) within a semi-heterarchical flexible manufacturing system (SHFMS) control architecture. This architecture is composed of two types of decisional entities, global and local, and it exists three different modes in which those two types of entities can interact. In this paper, various ways in which OF can be integrated in the SHFMS architecture are presented and analyzed. Two of these options were implemented and tested using a theoretical flexible manufacturing system benchmark. The promising results confirms the significant contribution OF can provide, not only in terms of Just-in-Time (JIT) global performance but also in terms of the capacity to react to perturbations.