Stéphane Font

Some control strategies for a high-angle-of-attack missile autopilot

Abstract Recent interest in high maneuverability and stealth in missiles has triggered new investigations in estimating the potential and applicability of recent theoretical control methods as well as how they can meet industrial demands. Since the work presented here is closely related to an industrial application it is desirable to deal primarily with classical regulators. In this paper, two nonlinear methods are considered: `Approximate feedback linearization’ and the `asymptotic output tracking’ approach. Simulation results are given.

Enhanced genetic algorithm with guarantee of feasibility for the unit commitment problem

In this paper, an enhanced genetic algorithm for the Unit Commitmentproblem is presented. This problem is known to be a large scale, mixed integerprogramming problem for which exact solution is highly intractable.Thus, a metaheuristic based method has to be used to compute a very often suitablesolution. The main idea of the proposed enhanced genetic algorithm is touse a priori knowledge of the system to design new genetic operators so as toincrease the convergence rate. Further, a suitable penalty criterion is defined toexplicitly deal with numerous constraints of the problem and to guarantee thefeasibility of the solution. The method is also hybridized with an exact solutionalgorithm, which aims to compute real variables from integer variables. Finally,results show that the enhanced genetic algorithm leads to the tractable computationof a satisfying solution for large scale Unit Commitment problems.

District heating : a global approach to achieve high global efficiencies

Abstract District heating networks are of great interest because of the high efficiencies which can be potentially achieved by a suitable management. However, due to system complexity, control laws are often heuristic laws and take into account only local parameters of the network, leading to suboptimal solutions when applied to the whole network. In this paper, a global approach is used. Models well suited to optimisation issues are defined to get tractable solutions for the whole problem. Simulation results are given for a district heating network benchmark designed by Electricite de France, and comprising a cogeneration system.

Some Control Strategies of High Angle of Attack Missile Autopilot

Abstract Recent interest for missile high maneuverability and stealthness motivates new investigations in order to estimate potential and applicability of recent theoretical control methods and consequently to meet the industrial demands. Since our work is closely related to an industrial application it is desirable to primarily deal with classical regulators. In the sequel, two nonlinear methods are considered: “Approximate feedback” linearization and asymptotic output tracking approach. Simulation results are given.

OPTIMIZATION AND CONTROL OF A DISTRICT HEATING NETWORK

Abstract The short term optimization and control of a district heating network is a crucial point for Energy Industries. In this article, a model, well suited to industrial issues is presented and then used to determine the optimal schedule of the network. As consumers demands are imperfectly predicted, it is necessary to have a closed loop strategy to robustly control the network. The control law is based on the schedule planning (open loop control) and on predictive control. The control method has been validated on a benchmark network created by ‘EDF’ (Electricite de France).

CONVEX OPTIMAL CONTROL DESIGN VIA PIECEWISE LINEAR APPROXIMATION

Abstract In convex optimization techniques for optimal control design, the main challenge is to manage an infinite dimensional Youla parameter. To make the problem tractable, a finite basis has to be defined. While delay basis has been shown efficient for discrete LTI plants, common bases for continuous applications are generally inefficient and numerically bad conditioned. This paper presents a straightforward functional basis derived from piecewise linear approximation theory. Several associated results on LTI systems, related with convolution product and Laplace transformation, are developed.

Modeling and optimization of a dedicated FMCW radar frequency synthesizer

This paper presents the modeling and optimization of a frequency synthesizer dedicated to FMCW radar applications. This frequency synthesizer based on a type-I PLL presents the advantages of a simplified architecture with less potential electronic drawbacks. A methodology to optimize the filter loop is proposed in order to obtain the required smoothed frequency characteristic and correct the VCO distortion.

Linear controller retuning approach based on nonconvex nonsmooth optimization

The purpose of this paper is to describe how the fundamental problem of linear controller design can be solved, for general specifications, by combining a theoretical result with a recent numerical nonconvex nonsmooth optimization technique. Various temporal and/or frequency design criteria and constraints can be considered. The formulated optimization problem is complex; it involves implicit and explicit design parameters and nonsmooth criteria as well. A new algorithm based only on the gradient notion is fully described. This algorithm, mixing with an exact computation of gradients based on parametric sensitivity functions, appears to be well suited for controller design and retuning. As illustration, this method is used to design an optimal PI controller for a benchmark oscillatory model and to tune a PID controller for a motor position control. Computer simulations and experimental bench results are given to demonstrate the effectiveness of the proposed algorithm.

Nonsmooth optimization for nonlinear missile autopilot: Improvement under time domain constraints

In this paper, a new parametric optimization approach to retune nonlinear controllers is proposed. It discusses the design of these controllers under temporal constraints. The formulated optimization problem is often complex; it involves nonsmooth design parameters and criteria. An efficient optimization algorithm based on the approximation of the epsilon subdifferential notion is presented. It only requires gradients which are computed using parametric sensitivity functions. The proposed approach is applied to tune a nonlinear missile autopilot. The purpose especially concerns how to appropriately apply our procedure in order to improve performance of a controlled nonlinear dynamic system. We show that the choice of the controller structure and parameters has a great effect on the validation of the temporal specifications. Simulation results are given to demonstrate the effectiveness of the proposed approach.

Convex optimization for control analysis application to the steam generator water level

In this paper a convex synthesis methodology is applied to a benchmark problem. The objective is to control the water level in the steam generator of a Pressurized Water Reactor. Both robustness and performance constraints are specified for this benchmark. The proposed approach explicitly takes into account constraints in both time and frequency domains. In this method, specifications are expressed into a convex optimization problem using Youla parameterization. A finite dimensional basis of parameters is then used, making the optimization problem numerically tractable. Two linear controllers corresponding to high and low operating power ranges are designed. The resulting controller is finally validated on a non-linear simulator used for the benchmark, thus allowing for comparison.