Hachemi Chekireb

Design of a fuzzy adaptive controller for MIMO nonlinear time-delay systems with unknown actuator nonlinearities and unknown control direction

This paper aims at investigating the fuzzy adaptive control design for uncertain multivariable systems with unknown actuator nonlinearities and unknown control direction that possibly exhibit time-delay. The actuator nonlinearities involve dead-zone or backlash-like hysteresis, while the control direction is closely related to the sign of the control gain matrix. Two fuzzy adaptive controllers are proposed to deal with such an issue. The design of the first controller is mainly carried out in the free time-delay case, while the second control design is performed assuming that the system exhibits time-varying delays. Of practical interest, the adaptive compensation of the effects of the actuator nonlinearities requires neither the knowledge of their parameters nor the construction of their inverse. Furthermore, the lack of knowledge of the control direction is handled by incorporating in the control law a Nussbaum-type function. The effectiveness of the proposed fuzzy adaptive controllers is illustrated through simulation results.

Trajectory tracking with obstacle avoidance of redundant manipulator based on fuzzy inference systems

In presence of the uncertainties in robot dynamics, model-based control law can easily fail. In our paper, this important question is tackled by using fuzzy adaptive control to drive with obstacle avoidance an industrial redundant manipulator under the hypothesis of uncertain dynamics. This hypothesis makes our controller an original one, since the problem of the tracking trajectory in the presence of obstacles and assuming that the robot dynamics are unknown has not been discussed before in the literature. Besides, the proposed obstacle avoidance is achieved by generating a self-motion. Furthermore, the usual procedure related to the obstacle avoidance based on Euclidean distance in 3D space is made easier since this one includes only the parameters of 2D space. This self-motion is directly incorporated into the adaptive fuzzy control scheme via the filtered tracking errors. The proposed method is tested by simulations in the case of redundant robot (PUMA 560) operating in 3D space in presence of obstacles. Despite that the robot dynamics are assumed to be uncertain, the proposed control performance is satisfactory. Indeed, the trajectory tracking control, incorporating self-motion obstacle avoidance, operates effectively with weak tracking control errors and bounded actuator torques evolving in admissible range.

On a sliding mode control and observer of induction motor

The aim of this paper is to develop a general class of manifolds on which sliding mode flux observation and control of induction motors. For flux-speed tracking, we consider the case where the sliding surface is formed by the derivative of the output tracking error and a function of this error. For flux observation, the surface is a function of the estimated error. Simulations results are given to highlight the performances of the proposed control method.

Redundant states in five-level inverter using selective harmonics elimination PWM

This study deals the problem of DC-link capacitor voltages balance in five-level inverter. The proposed solution is based on the redundant switching vectors using the selective harmonics elimination SHEPWM instead of space vector modulation [3]. The inverter supplies a high power induction motor of 20MW. The obtained results prove that the balancing of the dc capacitor is kept with canceling the most undesirable harmonics row 5th, 7th, and 11th.

Stability analysis of DFIG stator powers control based on sliding mode approach

The doubly fed induction generator (DFIG) received recently an important consideration in medium and high power wind energy conversion systems integration, due to its advantages compared to other generators types. The stator power sliding mode control (SPSMC) proves a great efficiency judge against other control laws and schemes. In the SPSMC laws elaborated by several authors, just the slide surface tracking conditions are elaborated using Lyapunov functions, and the boundedness of the DFIG states is never treated. Some works have validated theirs approaches by experiments results in case of specified machines and steady-states points, but these verifications stays insufficient to generalize to other machines and steady-states points range. Adding to this argument, the DFIG states boundedness demonstration is widely suggested in goal to ensure that in the application of the SPSMC, the states evaluates within theirs tolerable bounds. Our objective in the present paper consists to highlight the efficiency of the SPSMC by stability analysis. The boundedness of the DFIG states such as the stator powers and rotor flux is discussed. Moreover, the states trajectories are finding using analytical proves taking into consideration the SPSMC gains.

On-line identification of DFIG parameters with rotor current reconstitution

In this paper we develops an algorithm allowing to online identify the DFIG inductances, such the stator, rotor and mutual inductances. Only the stator currents and voltages sensors are required. The rotor currents reconstituted using the identified DFIG inductances. The inductances and the rotor currents are finding by solving the non-derivatives equations. The stator and rotor flux needed in the identification algorithm are estimated. The sliding mode observer of the rotor flux is used. The feasibility of our method tested, in the case of stator power control, by simulation in the case of DFIG rating at 1.5MW.

Lyapunov-based Cascaded Nonlinear Control of Induction Machine

This article develops Lyapunov-based nonlinear control to ensure the flux-speed tracking regime of a voltage-fed induction machine. The control law is determined in two steps. First, the virtual control, based on Lyapunov function, is obtained in order to impose the flux-speed tracking. After this step we deduce the real control, imposing the virtual control law. The simulation results of flux-speed tracking of induction machine show the validity of the proposed method in the presence of strong parametric perturbations. Finally, an extension of the proposed method to most voltage AC machines is discussed. This allows us to obtain a unified view for the control of electric AC machines.

New dc-link balancing algorithm for multilevel inverter in photovoltaic system

In this paper, a three-phase five level inverter with new balancing algorithm is proposed using Selective Harmonics Elimination PWM. The inverter is fed photovoltaic generator as dc source. 36 redundant vectors are making use for the 12 unbalance cases of four capacitor voltages instead of 24 cases presented in the previous works. The obtained results show that the frequency of the PWM is unchanged.

Adaptive sliding mode with time delay control based on convolutions for power flow reference tracking using a VSC-HVDC system

This paper deals with the design of an adaptive sliding mode with a time delay control based on convolutions (ASMTDCC) approach for a voltage source converter (VSC) high voltage direct current (HVDC) transmission system for power flow reference tracking over a wide range of operating conditions considering parameter variations and external disturbances. For this purpose, the model of a VSC-HVDC transmission system connecting two asynchronous electrical grids is developed. The problem of designing an ASMTDCC feedback scheme, via a control strategy, is addressed seeking a better performance. For ensuring robust behavior and reducing chattering, the ASMTDCC scheme is realized based on time delay approximation and sliding mode techniques. Theoretical developments and results are illustrated through simulation results.

Adaptive intelligent backstepping controller of induction machines

This paper presents an adaptive fuzzy backstepping controller (AFB) to handle the speed tracking problem of induction machines with unknown model, uncertain load-torque and nonlinear friction. The proposed AFB scheme uses adaptive fuzzy systems to reasonably approximate the uncertain dynamics appearing in the induction machine model. The backstepping concept is employed to systematically construct the control law deduced from the stability analysis in the sense of Lyapunov. It is shown that all the closed-loop signals are bounded and the tracking errors exponentially converge to a small neighborhood of the origin. Simulation results illustrate the effectiveness of the proposed control scheme.