Faouzi Msahli

Adaptive high gain observer based output feedback predictive controller for induction motors

An accurate estimation of both rotor and stator resistances is usually required to achieve high performance control in induction machine drive systems. In our study, an output feedback predictive controller which is adaptive with respect to these parameters uncertainties is proposed. Such design attempts to a fully decoupling in speed and flux magnitude when conjoint estimation of the state and the critical parameters is performed. Precisely, two-stage of high gain observer are used to provide on-line update of rotor and stator resistances as well as following time evolution of the rotor flux and the load torque. Then, the instantaneous estimates are exploited in a constrained predictive controller for achieving the admissible tracking objective. The little number of the synthesis parameters and the ability of the control scheme to handle input constraints constitute the two main benefits of our design. Simulation results show that the proposed controller is suitable for high dynamics performance applications.

Active modes and switching instants identification for linear switched systems based on Discrete Particle Swarm Optimization

In this paper, a methodology for identifying switching sequences and switching instants of switched linear systems (SLS) is derived. The identification problem of a SLS is a challenging and non-trivial problem. In fact, it involves interaction between binary, discrete and real-valued variables. A SLS switches many times over a finite time horizon and thus estimating the sequence of activated modes and the switches locations is a crucial problem for both control and Fault Detection and Isolation (FDI). The proposed methodology is based on the Discrete Particle Swarm Optimization (DPSO) technique. The identification problem is formulated as an optimization problem involving noisy data (system inputs and outputs). Both a set of binary variables corresponding to each sub-model before and after each switch, and the corresponding switching instants are iteratively adjusted by the DPSO algorithm. Thus, the DPSO algorithm has to classify which sub-system has generated which data. The efficiency of the proposed approach is illustrated through a numerical example and a physical one. The numerical example is a Switched Auto-Regressive eXogenous (SARX) system and the physical one is a buck-boost DC/DC converter.

Predictive and Backstepping Control of Double Tank Process: A Comparative Study

ABSTRACT This paper addresses the nonlinear control design problem for a state-coupled two-tank liquid-level system. For this systems dynamics, motivated by a desire to provide precise liquid-level control, two radically different control approaches are presented and compared: the model predictive control and the backstepping control. In the first proposed approach, a model-based predictive controller is designed for the two-tank liquid-level system that ensures exponentially stabilization for a particular class of second-order nonlinear system. Moreover, a robust controller based on a backstepping strategy is designed in order to ensure globally asymptotically stabilization for another particular class of second-order nonlinear systems. To ensure a suitable basis for their comparison, two different control methods are designed and verified with the same test setup. To highlight the efficiency and applicability of the proposed control schemes, theoretical comparisons as well as experimental results are provided and discussed.

Stability analysis and stabilization of switched linear systems based on vector norms approach

The stability analysis and the stabilization problems for continuous-time switched linear systems are studied in this paper, by investigating a new stability conditions based on the comparison, the overvaluing principle, the application of Borne-Gentina criterion and the Kotelyanski conditions. These stability conditions issued from vector norms correspond to a vector Lyapunov function. Indeed, the switched system to be controlled will be represented in the Companion form. A comparison system relative to a regular vector norm is used in order to get the simple arrow form of the state matrix that yields to a suitable use of Borne-Gentina criterion for the establishment of sufficient conditions for global asymptotic stability.

Simultaneous state and unknown input reconstruction using cascaded high-gain observers

ABSTRACT This paper presents a systematic routine for jointly reconstruct the state variables and the unknown inputs (UIs) for a large class of nonlinear MIMO systems. After an appropriate change of state coordinates, a set of cascade high-gain observers (CHGO) are designed in such a way that each of them provides an estimation of only one component of the UI vector, except the last one which gives a final adjustment of the whole state variables. Such design achieves a boundary of the state estimation error which can be arbitrarily small by properly specifying the sole synthesis parameter. An illustrative example verifies the effectiveness of the proposed scheme.

Comparative study of higher order sliding mode controllers

The standard sliding mode control (SMC) lads, generally, to the appearing of an undesirable chattering phenomenon to solve this problem we develop a novel approach of higher order sliding mode control (HOSMC). The proposed procedure provides an exponential stability on the sliding surface and guarantees the robustness against uncertainties and external matched disturbances. In this paper, and to show the good performances of the new design scheme we present a comparative study between three well known techniques of HOSMC in literature with our approach. Numerical simulations are developed to show the effectiveness of the proposed approach.

Optimal control of switched linear systems by particle swarm optimization.

Abstract Abstract This paper deals with Optimal Control problems of Dynamical Switched Linear Systems (OCPDSLS). This special class of hybrid systems combines the standard control, where dynamic subsystems are described by differential linear equations with a switching law which activates, alternatively, these subsystems. For a pre-specified modal sequence, we demonstrate that switching time instants and continuous input can be solved simultaneously by using an evolutionary computation technique, namely Particle Swarm Optimization (PSO). Some structural and numerical difficulties encountered in solving such problems by conventional approaches are discussed. The mapping between PSO and OCPDSLS is established via a generic procedure to synthesize optimal control laws. An illustrative numerical non-convex example is solved showing the effectiveness of the proposed technique in overcoming difficulties of this problem known to be NP-hard, non-linear and constrained one.

The extended Kalman filter for nonlinear system: Application to system of waste water treatment

This paper addresses the estimation of non-measured states in waste water treatment process. Specifically, the extended Kalman filter has been investigated for this class of nonlinear systems. Of particular interest, it is shown that extended Kalman filter can be applied to estimate the states in our system and provide good estimations for the non-measurable states.

Optimization of switching instants for optimal control of switched discrete non linear systems based on Particle Swarm algorithm

In this paper, we studied the optimal control problems for switched non linear systems; in particular we focus on problems in which a prespecified sequence of active subsystems is given and propose a discrete Particle Swarm Optimization approach to find the optimal switching instants. The objective is to minimize the performance criterion wish depend on these instants.

Sliding mode observer sensorless vector controlled induction motor drive with anti-windup PI speed controller

This paper deals with sliding mode observer (SMO) for sensorless control of induction motor (IM) drive with anti-windup proportional integral (AWPI) speed controller. By using PI speed controller with its output variables saturated, a wind-up phenomenon and an unstable response often occur especially for sensorless electric motor drive. In order to improve a high performance SMO sensorless vector controlled induction motor drive, we use an anti-windup action included in the PI controller inner speed loop. The proposed scheme is implemented on a digital signal processor (DSP) using a dSpace DS1104 controller board. Experimental results are presented to show the effectiveness of the algorithm with smoothly and stably response.