Mohamed Smaoui

A Robust Differentiator-Controller Design for an Electropneumatic System

In this paper, a robust differentiator via sliding mode is studied. A comparative study between the robust differentiator and a classical one is presented. Experimental results of the proposed differentiator in the context of third order sliding mode controller for an electropneumatic system are given to illustrate the developments.

High gain and sliding mode observers for the control of an electropneumatic actuator

Electropneumatic actuators are more and more used in industrial applications. Due to nonlinear phenomena, for many applications, high accuracy can only be obtained when using nonlinear control laws. These strategies allow to get high performances but often need the knowledge of all state variables. Then, there is a real interest to design observers in order to estimate state from the measurements of only one of the chamber pressures in the actuator and carriage position. This paper focuses on a comparison between two nonlinear observers for a half-meter stroke electropneumatic unsymmetrical cylinder controlled by two three-way servodistributors: a high gain observer and a sliding mode one. Simulations are made with a fluid power systems dedicated software, AMESim.

Robust position control of an electropneumatic system using second order sliding mode

First order sliding mode control is an important robust control approach. For the class of systems to which it applies, first order sliding mode controller provides a systematic approach to the problem of maintaining stability and consistent performance in the face of modeling imprecision. On the other hand, the chattering phenomenon is one of the major problems in first order sliding mode control. This paper introduces a second order sliding mode control approach in the context of position control of an electropneumatic system. The main objective is to demonstrated through this approach the undesired chattering phenomenon can he avoided while retaining the same robustness of first order sliding mode control.

Robust control of electropneumatic actuator by 3/sup rd/-order sliding mode

This paper presents the synthesis and practical implementation of a robust 3/sup rd/ order sliding mode controller for an electropneumatic actuator. The controllers robustness is analyzed with respect to parameter uncertainties and load disturbances. Implementation results on an experimental set-up showing the controller performances are presented.

A Solution to the “Stick-Slip” Problem for an Electropneumatic Drive

Abstract This paper describes a solution to the problem of “stick-slip” for an electro-pneumatic system. The phenomenon of “stick-slip” may appear during the mechanical static state when the position is fixed but the pressures continue to evolve in each actuator chamber, until exceeding the dry friction zone. The system is then in partial equilibrium. The idea to avoid this phenomenon is a switching control law between the tracking position control and the pressure regulation.

HYBRID FORCE CONTROL WITH ON/OFF ELECTROPNEUMATIC STANDARD DISTRIBUTORS

Abstract This paper presents a new control method applied to the electro-pneumatic field. This strategy originates from the hybrid control theory recently developed for the control of asynchronous or synchronous electrical motors, e.g. Retif (2004). The interest of this strategy concerns the possibility of using standard on/off distributors instead of the usual servodistributors (components issued from proportional technology) for the force control of a pneumatic cylinder. Distributor components have less performance but are cheaper than a servodistributor. The aim is to obtain, with a distributor, the same performances as servodistributors on the global system. Based on both cylinder and distributor models, the hybrid control presented here chooses the best state for each on/off distributor to reach the desired force value. Experimental results are presented and discussed.

Lyapunov Stability Analysis of Switching Controllers in Presence of Sliding Modes and Parametric Uncertainties With Application to Pneumatic Systems

This paper concerns the control and the stability analysis of pneumatic actuators, which are nowadays of widespread use in the industry. A problem related to the use of such actuators is the so-called stick-slip, due to the presence of dry friction in the system. In this paper, we provide an empirical switching control law that avoids this phenomenon as well as a general approach to the stability analysis of nonlinear systems that will let us prove the stability of the closed-loop system. The approach is based on casting the closed-loop system into a piecewise-affine form and finding a Lyapunov function for it. Such an approach will be able to cope with the special features of the controlled pneumatic system model, namely, the presence of sliding modes, a whole equilibrium set, and uncertainties on the values of a few parameters. At the end of this paper, we will show how such a method can be successfully applied to our experimental setup under several hypotheses.

Modeling and sliding mode control of an electropneumatic system

This paper present a sliding mode controller of an electropneumatic system. In order to obtain a good position and pressure tracking and to reduce the chattering phenomenon, a proportional derivative PD sliding surface is used with an integral law. Finally, simulation results are presented to test the effectiveness of this proposed controller comparing with a classic sliding mode controller.

From theoretical differentiation methods to low-cost digital implementation

In this paper we review different differentiation methods and we investigate their digital implementation. The motivation is the design of a numerical differentiator based on a low-cost microcontroller device. Standard digital differentiation algorithms are presented and an alternative approach based on weighted H∞ filtering is introduced. In this approach, the differentiator design is based on signal and noise spectral density modelisation for the derivative estimation accuracy improvement. Experimental results are presented in order to prove the effectiveness of such approach.

Nonlinear Passivity Based Control Law with Application to Electropneumatic System

Abstract This paper presents a synthesis of a nonlinear controller to an electropneumatic system. Nonlinear passivity based control law is applied to the system under consideration. First, the nonlinear model of the electropneumatic system is presented. It is transformed to be a nonlinear affine model and a coordinate transformation is then making possible the implantation of the nonlinear controller. A nonlinear control law is developed to track desired position. Experimental results are also presented and discussed.