Silver europium(III) polyphosphate

Europium(III) silver polyphosphate, AgEu(PO3)4, was prepared by the flux method. The atomic arrangement is built up by infinite (PO3)n chains (periodicity of 4) extending along the c axis. These chains are joined to each other by EuO8 dodeca­hedra. The Ag+ cations are located in the voids of this arrangement and are surrounded by five oxygen atoms in a distorted [4+1] coordination

Linear time-varying flatness-based control of Anti-lock Brake System (ABS)

In this paper, a flatness-based control strategy for linear time-varying systems is proposed in order to track a desired trajectory. The flatness-based control is designed by using two observers: a reduced order observer with a constant estimator error gain and an exact observer for designing a polynomial two-degrees-of-freedom controller without resolving Bezout equation in time varying framework. The proposed approach is illustrated with the control of an Anti-lock Brake System (ABS) and led to track a given trajectory for the wheel slip

Towards an ultra-local model control of two-tank-system

This paper deals with the design of an ultra­ local model control. The proposed approach is based on the estimation of the ultra-local model parameters using least squares resolution technique instead of numerical derivation technique. The closed-loop control is implemented through an adaptive PI in order to reject the influences of the dis­ turbance and noise output signais. Its main advantages are: its simplicity and its robustness with respect to the parame­ ter uncertainties of system. In this paper, it is processed to test the efficiency of the parameter estimation method com­ pared with the performance of numerical derivation tech­ nique. The method is applied to the water level control of a two-tank-system. Numerical simulations show that the gen­ erated desired trajectory is followed in an efficient way even with severe operating conditions

Design of adaptive PID controllers based on adaptive Smith predictor for ultra-local model control

In this paper, an ultra-local model control approach based on adaptive Smith predictor is proposed. The design of adaptive PID controller takes into account the estimation of variable time delay which is compensated by the addition of an adaptive Smith predictor. The purpose of this paper is to solve the online estimation problem of time delay thanks to the proposed identification method of ultra-local model parameters. A performance comparison between the proposed control approach and the Smith predictor control with classical PID is carried out. The numerical simulation results of the thermal process study with severe constraints and operating conditions show the superiority of the adaptive PID controller. The robustness with respect to noises, disturbances and system parameter uncertainties of control approaches are highlighted

Experimental comparison of new adaptive PI controllers based on the ultra-local model parameter identification

This paper is devoted to an experimental comparison between two different methods of ultra-local model control. The concept of the first proposed technique is based on the linear system resolution technique to estimate the ultra-local model parameters. The second proposed method is based on the linear adaptive observer which allows the joint estimation of state and unknown system parameters. The closed-loop control is implemented via an adaptive PID controller. In order to show the efficiency of these two control strategies, experimental validations are carried out on a two-tank system. The experimental results show the effectiveness and robustness of the proposed controllers

Sliding window identification with linear-equality constraints

In this paper, we present a new algorithm of sliding window identification with linear-equality constraints. This algorithm consists in firstly deleting the oldest set of data and in secondly adding the last set of data. The method developed in this paper allows to consider at every step a set of new data by an extension of their result. The proposed algorithm is based on the recursive calculus of the pseudo-inverse matrix from the forms of Albert and Sittler. A simple and easily implementable initialization of the constrained algorithm is proposed. An improvement is obtained by removing the influence of oldest set of data and by satisfying the linear-equality constraints. It is shown that the solutions of the sliding window identification algorithm converge to the true parameter that satisfies the equality constraints. Numerical example is provided to show the effectiveness of the proposed method

Ultra-local model control based on an adaptive observer

In this paper, a new ultra-local model control approach is proposed. The concept is based on the linear adaptive observer to estimate the ultra-local model parameters instead of algebraic derivation technique. The importance of adaptive observer is deduced in the join estimation of state and unknown parameters of parametric systems. The closedloop control is implemented via an adaptive PID controller to reject disturbances due to exogenous parameter uncertainties. In this paper, a performance comparison between the adaptive observer based method and the algebraic derivation technique is developed to show the efficiency of the proposed control strategy. The approaches are applied to a two-tank system for the water level control. Several successful simulation results are shown to demonstrate the effectiveness of the proposed controller

A new adaptive controller for a two-tank-system based on algebraic derivation techniques

In this paper, a new adaptive controller is proposed for ultra-local model based control. The concept is based on the algebraic derivation techniques to estimate the two ultra-local model parameters. A comparison study with the control method of Fliess-Join which is based on some elementary differential algebra is developed. The robustness of the ultra-local model controllers with respect to noises, external disturbances and parameter uncertainties is highlighted. The control strategies are successfully tested via the control of a two-tank nonlinear system. Different numerical simulations show the effectiveness of the proposed controller

An algebraic control approach based on the estimation of an ultra-local Broïda model

This paper deals with a new parameter estimation method for an ultra-local model of Broïda. The proposed approach is based on the algebraic derivation techniques and the linear system resolution method, in order to estimate the ultra-local model parameters, such that the variable time-delay. The closed-loop control is achieved via an adaptive PI controller to reject the influence of noises and disturbances. A simulation results of a thermal process application are given to validate the effectiveness of the proposed strategy. A performance comparison with a classical PID controller is achieved

Performances comparison between ultra-local model control, integral iliding mode control and PID control for a coupled tanks system

This paper deals with the comparison of robust control approaches for the level water control of coupled tanks system. A new ultra-local model control (ULMC) approach leading to adaptive controller is proposed. The parameter identification of the ultra-local model is based on the algebraic derivation techniques. The main advantages of this control strategy are its simplicity and robustness. A comparison study with the integral sliding mode control (ISMC) approach is carried out. The perfect knowledge of the output variable degree, which is a standard assumption for sliding modes, is assumed here. The comparison of the simulation results for the proposed adaptive controller with the ISMC controller and the classical PID controller has a better performances in the presence of external perturbations and parameter uncertainties