Stabilization of Fractional‐Order Linear Systems with State and Input Delay

This paper describes a variable structure control for fractional‐order systems with delay in both the input and state variables. The proposed method includes a fractional‐order state predictor to eliminate the input delay. The resulting state‐delay system is controlled through a sliding mode approach where the controller uses a sliding surface defined by fractional order integral. Then, the proposed control law ensures that the state trajectories reach the sliding surface in finite time. Based on recent results of Lyapunov stability theory for fractional‐order systems, the stability of the closed loop is studied. Finally, an illustrative example is given to show the interest of the proposed approach.     

Solving the integrated lot-sizing and job-shop scheduling problem

Production planning and scheduling are usually performed in a sequential manner, thus generating unfeasibility conflicts. Moreover, solving these problems in complex manufacturing systems (with several products sharing different resources) is very challenging in production management. This paper addresses the solution of multi-item multi-period multi-resource single-level lot-sizing and scheduling problems in general manufacturing systems with job-shop configurations. The mathematical formulation is a generalisation of the one used for the Capacitated Lot-Sizing Problem, including detailed capacity constraints for a fixed sequence of operations. The solution method combines a Lagrangian heuristic, determining a feasible production plan for a fixed sequence of operations, with a sequence improvement method which iteratively feeds the heuristic. Numerical results demonstrate that this approach is efficient and more appropriate than a standard solver for solving complex problems, regarding solution quality and computational requirements.     

Asymptotic numerical methods for unilateral contact

New algorithms based upon the asymptotic numerical method (ANM) are proposed to solve unilateral contact problems. ANM leads to a representation of a solution path in terms of series or Padé approximants. To get a smooth solution path, a hyperbolic relation between contact forces and clearance is introduced. Three key points are discussed: the influence of the regularization of the contact law, the discretization of the contact force by Lagrange multipliers and prediction–correction algorithms. Simple benchmarks are considered to evaluate the relevance of the proposed algorithms. Copyright © 2006 John Wiley & Sons, Ltd.     

TOC-based planning and scheduling model

A case study investigating a reengineering project based on theory of constraints fundamental measurements is presented. Bad bottom line results triggered the project. The main constraint is the market itself. Moreover, a policy constraint encouraging local optima in the planning and scheduling process limits the company from reaching its goal and prevents it from exploiting the market constraint. The paper also discusses briefly a risk analysis of such projects.     

Neyman–Pearson Test for Fault Detection in the Process Dynamics

Fault detection in industrial plants plays an important role for ensuring the product quality, safety, and reliability of plant equipment. The purpose of this work is to propose a fault detection technique with a black-box modeling and a statistical module based on Neyman–Pearson test (NPT). In fact, Nonlinear Auto-Regressive Moving Average with eXogenous input (NARMAX) model is used to obtain a model for the normal condition operation. To detect a fault, The NPT has been applied to the residual of NARMAX model. The efficiency of the technique is illustrated through its application to monitor product quality in a distillation unit.     

Design of variable structure voltage regulator using poleassignment technique

In a power system, the role of a generator voltage regulator is to ensure that the output voltage is maintained within an acceptable threshold. In this paper a voltage regulator is proposed. The design of this regulator is based on both variable structure control theory and a pole assignment technique. The performance of the proposed regulator has been compared to that of the realistic regulator system proposed by the IEEE Committee on Excitation Systems. The results are discussed, and the pertaining recommendations are given