Philippe Chevrel

Modeling the Visual and Motor Control of Steering With an Eye to Shared-Control Automation

This paper describes a newly developed driver model that focuses on the control of car steering. The model represents visual anticipation of road curvature and compensation of lateral positioning error. It also incorporates a neuromuscular system, inspired by Hoult and Cole (2008), including an internal model of the steering system compliance, muscle co-activation by α and γ signals and the stretch reflex. Preliminary driving simulator experiments with five participants showed that the identification of model parameters yielded consistent results. Moreover, the model was able to steer the driving simulator by itself and showed a behavior similar to that of the human driver who provided the data for parameter identification. This model may be used for the design of automation for shared control of steering.

Linear Parameter-Varying Controller Design for Active Power Filters

Abstract Most often, active filters are designed by assuming that the network frequency is time-invariant. There exist some cases however where this assumption failed: for example the frequency of the aboard ship the electrical network frequency may have significant deviation. This paper shows the efficiency of the H ∞ linear parameter-varying control design methodology applied to the active power-filtering problem in presence of a time-varying network frequency. Performances and robustness of the resulting controller are analyzed. Model reduction of linear parameter-varying controller is then considered. Finally, simulation results are exposed proving the validity of this approach.

Dilated LMI characterisations for linear time-invariant singular systems

This article explores, based on projection lemma, dilated linear matrix inequality (LMI) characterisations for linear time-invariant singular systems. The deduced formulations cover not only the existing results reported in the literature, but also complete some missing LMI conditions. This article also lightens the mutual relations of these characterisations and clarifies the relation between the dilated LMIs for the conventional state-space systems and those for singular systems. The well-known results for the state-space setting reported in the literature can be reviewed as special cases.

IMPLICIT STATE-SPACE REPRESENTATION : A UNIFYING FRAMEWORK FOR FWL IMPLEMENTATION OF LTI SYSTEMS

Abstract Practically, some intermediary realizations are used in order to simulate, numerically, dynamic systems. One of the most popular is the state-space realization. It reveals to be very useful to study the impact of Finite Word Length implementation, especially in the case of embedded controller. Numerous works concerned the design of the “best” realization concerning parameterisation, numerical noise minimisation or saving computation. This paper points out however that a standard state-space realization is too basic to take into account some interesting realizations. On the contrary, it highlights that implicit state-space realizations allows a more direct link with the macroscopic computations to be performed. It is necessary to describe some popular algorithms simulating LTI systems. Moreover, such a representation has the important property to unify different ways of research considering differently the possibilities offered by using the shift, δ or γ operators.

Parametrization of extended stabilizing controllers for continuous-time descriptor systems

This paper investigates the extended stabilization control problem for continuous-time descriptor systems (also refereed to as singular systems, implicit systems or generalized state-space systems) where unstable and nonproper weighting filters are used. In such nonstandard problem, the desired controller, called the extended stabilizing controller, has to satisfy two conditions simultaneously: (i) the closed-loop is admissible; (ii) only the internal stability of a part of the closed-loop is required. In terms of two generalized Sylvester-type equations, necessary and sufficient conditions for the existence of an observer-based extended stabilizing controller are given. Moreover, a parametrization of the class of extended stabilizing controllers is formulated.

Synthesis and Analysis of Robust Flux Observers for Induction Machines

Abstract This paper presents and compares two approaches for the design of robust flux observers for induction motors. Both take the measurement noises into account. The first one, based on Linear Matrix Inequalities (LMI) formulation, leads to a quadratically stable flux observer. The second one is a Kalman filter with a particular tuning method, which reduces the effects of some parameter uncertainties. The dynamical performances, robustness and algorithmic complexity of both observers are shown and compared.

Finite wordlength controller realisations using the specialised implicit form

A specialised implicit state-space representation is introduced to deal with finite wordlength effects in controller implementations. This specialised implicit form provides a macroscopic description of the algorithm to be implemented. So, it constitutes a unifying framework, allowing to encompass various implementation forms, such as the δ-operator, the ρDirect Form II transposed, observer-based and many other realisations usually considered separately in the literature. Different measures quantifying the finite wordlength effects on the overall closed-loop behaviour are defined in this new context. They concern both stability and performance. The gap with the infinite precision case is evaluated classically through the coefficient sensitivity and roundoff noise analysis. The problem of determining a realisation with minimum finite wordlength effects can subsequently be solved using appropriate numerical methods. The approach is illustrated with an example.

Multiobjective controller synthesis for parameter dependent descriptor systems via dilated LMI characterizations

This paper proposes dilated LMI characterizations of admissibility, D-admissibility, H¿ and H2 norms for continuous-time descriptor systems. These dilated LMIs achieve less conservative results when dealing with robust admissibility/performance analysis of affine parameter-dependent descriptor systems. Furthermore, based on these conditions, the paper presents an iterative design procedure for multiobjective state feedback control of parameter dependent descriptor systems. The main idea underlying the proposed method is to linearize the products of controller parameter K and the auxiliary variable G by assigning a part of G. When initializing the proposed algorithm, the assignment takes into account an explicit characterization of G. The effectiveness of the proposed conditions and design method is shown through some numerical examples.

Modelling human control of steering for the design of advanced driver assistance systems

Abstract This paper reviews a set of scientific studies on how driver modelling may serve as the basis for designing advanced driving assistance systems. The work was aimed at explicitly representing the human visual and motor processes involved in the control of steering, and took into account current knowledge in the behavioural sciences. The nature and structure of the model, and its calibration using experimental data (identification), were addressed. Two design applications were considered: 1) estimating the driver state in various conditions of distraction and 2) building an automatic controller for haptic shared control of the steering wheel.

Extended H 2 output feedback control for continuous descriptor systems

This paper investigates the design of an “extended” H2 output feedback controller for continuous descriptor systems. In such problem, the controller, which is described within descriptor framework, has to satisfy simultaneously two conditions: 1-The closed-loop is admissible and has minimum H2 norm. 2-Only the internal stability of a part of the closed-loop is sought. In such case, the standard H2 output feedback control problem for descriptor systems cannot be solved. An explicit characterization of the optimal solution, based on two generalized algebraic Riccati equations (GAREs) and two structured generalized Sylvester-type equations, is given. A numerical example is included to illustrate the applicability of the proposed results.