Publications de Roland Longchamp

RST Controller Design by Convex Optimization Using Frequency-Domain Data

Roland Longchamp, Alireza Karimi, Gorka Galdos Sanz de Galdeano

A new robust fixed-order RST controller design approach by convex optimization is proposed in this paper. Only frequency-domain data are considered in the approach for linear time-invariant single-input single-output systems. It is shown that performance s ...

2011

Interactive applications to explore the parametric space of multivariable controllers

Yves Henri Philippe Piguet, Roland Longchamp

This paper describes interactive applications used to illustrate an advanced course on multivariable control. The direct manipulation of features in graphics, such as eigenvectors in the phase plane or observer eigenvalues in the complex plane, gives the s ...

2011

Robust Controller Design by Convex Optimization based on Finite Frequency Samples of Spectral Models

Roland Longchamp, Alireza Karimi, Gorka Galdos Sanz de Galdeano

Some frequency-domain controller design problems are solved using a finite number of frequency samples. Consequently, the performance and stability conditions are not guaranteed for the frequencies between the frequency samples. In this paper, all possible ...

Ieee Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, Nj 08855-1331 Usa2010

H∞ Controller Design for Spectral MIMO Models by Convex Optimization

Roland Longchamp, Alireza Karimi, Gorka Galdos Sanz de Galdeano

A new method for robust ﬁxed-order H∞ controller design by convex optimization for multivariable systems is investigated. Linear Time-Invariant Multi-Input Multi- Output (LTI-MIMO) systems represented by a set of complex values in the frequency domain are ...

Elsevier2010

H-infinity Controller Design for Spectral MIMO Models by Convex Optimization

Roland Longchamp, Alireza Karimi, Gorka Galdos Sanz de Galdeano

A recent method for robust fixed-order H-infinty controller design by convex optimization proposed in [1] is investigated in this paper for the tuning of multivariable controllers. Linear Time-Invariant Multi-Input Multi-Output (LTI-MIMO) systems represent ...

2009

Modeling and Control of a Magnetically Levitated Planar Motor

Roland Longchamp, Marc Kunze, Alireza Karimi, Vincent Reymond

This paper deals with the modeling and control of a magnetically levitated planar motor. The actuator considered has moving coils and stationary magnets. The principal objective is to develop a model which can be implemented in simulation. Therefore, the d ...

2009

Iterative Learning Control based on Stochastic Approximation

Roland Longchamp, Alireza Karimi, Mark Edward John Butcher

In this paper stochastic approximation theory is used to produce Iterative Learning Control algorithms which are less sensitive to stochastic disturbances, a typical problem for the learning process of standard ILC algorithms. Two algorithms are developed, ...

2008

Frequency Domain Controller Design by Linear Programming Guaranteeing Quadratic Stability

Roland Longchamp, Marc Kunze, Alireza Karimi

In a recent work, a frequency method based on linear programming is proposed to design fixed-order linearly parameterized controllers for stable linear multi- model SISO systems. The method is based on the shaping of the open-loop transfer functions in the ...

IEEE2008

Fixed-Order Controller Design for Systems with Polytopic Uncertainty Using LMIs

Roland Longchamp, Alireza Karimi, Hamid Khatibi

Convex parameterization of fixed-order robust stabilizing controllers for systems with polytopic uncertainty is represented as an LMI using KYP Lemma. This parameterization is a convex inner-approximation of the whole non- convex set of stabilizing control ...

2008

Robust fixed-order H infinity Controller Design for Spectral Models by Convex Optimization

Roland Longchamp, Alireza Karimi, Gorka Galdos Sanz de Galdeano

A new approach for robust fixed-order

H_\infty

controller design by convex optimization is proposed. Linear time-invariant single-input single-output systems represented by a finite set of complex values in the frequency domain are considered. It is show ...

IEEE2008

Fixed-Order Controller Design for Polytopic Systems Using Rank Deficiency in a Sylvester Matrix

Roland Longchamp, Alireza Karimi, Hamid Khatibi

Fixed-order controller design for LTI-SISO polytopic systems is investigated using rank deficiency constraint on the controller Sylvester resultant matrix. It is shown that the non-convexity of fixed-order controller design problem can be gathered in a ran ...

2008

On the Consistency of Certain Identification Methods for Linear Parameter Varying Systems

Roland Longchamp, Alireza Karimi, Mark Edward John Butcher

The consistency of certain identification methods for Linear Parameter Varying systems is considered. More precisely, methods for the identification of SISO input-output models are analysed. In order to perform a consistency analysis the application of erg ...

2008

Data-driven Precompensator Tuning for Linear Parameter Varying Systems

Roland Longchamp, Alireza Karimi, Mark Edward John Butcher

Methods for direct data-driven tuning of the parameters of precompensators for LPV systems are developed. Since the commutativity property is not always satisfied for LPV systems, previously proposed methods for LTI systems that use this property cannot be ...

IEEE2008

Model-Free Precompensator Tuning Based on the Correlation Approach

Roland Longchamp, Alireza Karimi, Mark Edward John Butcher

High performance output tracking can be achieved by precompensator or feedforward controllers based on the inverse of either the closed-loop system or the plant model, respectively. However, it has been shown that these inverse controllers can adversely af ...

2008

A Statistical Analysis of Certain Iterative Learning Control Algorithms

Roland Longchamp, Alireza Karimi, Mark Edward John Butcher

Iterative Learning Control (ILC) is a technique used to improve the tracking performance of systems carrying out repetitive tasks, which are affected by deterministic disturbances. The achievable performance is greatly degraded, however, when non-repeating ...

2008

Robust PID controller tuning with specifications on the infinity-norm of sensitivity functions

Roland Longchamp, Daniel Garcia, Alireza Karimi

An overview of the recent works on proportional integral derivative (PID) controller tuning methods based on specifications on the infinity-norm of the sensitivity functions is presented. The presented approach is very flexible relative to the controller s ...

2007

Robust Control of Polytopic Systems by Convex Optimization

Roland Longchamp, Alireza Karimi, Hamid Khatibi

Robust control synthesis of linear time-invariant SISO polytopic systems is investigated using the polynomial approach. A convex set of all stabilizing controllers for a polytopic system is given over an infinite-dimensional space. A finite-dimensional app ...

2007

Robust Loop Shaping Controller Design for Spectral Models by Quadratic Programming

Roland Longchamp, Alireza Karimi, Gorka Galdos Sanz de Galdeano

A quadratic programming approach is proposed to tune fixed-order linearly parameterized controllers for stable LTI plants represented by spectral models. The method is based on the shaping of the open-loop or closed-loop frequency functions in the Nyquist ...

2007

Robust Controller Design by Linear Programming with Application to a Double-Axis Positioning System

Roland Longchamp, Marc Kunze, Alireza Karimi

A linear programming approach is proposed to tune fixed-order linearly parameterized controllers for stable LTI plants. The method is based on the shaping of the open-loop transfer function in the Nyquist diagram. A lower bound on the crossover frequency a ...

2007

Robust Pole Placement of Systems with Polytopic Uncertainty Via Convex Optimization

Roland Longchamp, Alireza Karimi, Hamid Khatibi

Convex parameterization of fixed-order robust stabilizing controllers for systems with polytopic uncertainty is represented as an LMI using KYP Lemma. This parameterization is a convex inner-approximation of the whole non-convex set of stabilizing controll ...

2007