Benoit Clement

Modeling of a Complex-Shaped Underwater Vehicle for Robust Control Scheme

The two critical issues of robust control are stable controller synthesis and control performance guarantee in the presence of model uncertainties. Inside all robust stable solutions, small modeling parametric uncertainties lead to better performance controllers. However, the cost to develop an accurate hydrodynamic model, which shrinks the uncertainty intervals, is usually high. Meanwhile, when the robot geometry is complex, it becomes very difficult to identify its dynamic and hydrodynamic parameters. In this paper, the main objective is to find an efficient modeling approach to tune acceptable control design models. A control-oriented modeling approach is proposed for a low-speed semi-AUV (Autonomous Underwater Vehicle) CISCREA, which has complex-shaped structures. The proposed solution uses cost efficient CFD (computational fluid dynamic) software to predict the two hydrodynamic key parameters: The added mass matrix and the damping matrix. Four DOF (degree of freedom) model is built for CISCREA from CFD and verified through experimental results. Numerical and experimental results are compared. In addition, rotational damping CFD solutions are studied using STAR-CCM+ TM. A nonlinear compensator is demonstrated to tune linear yaw model for robust control scheme.

An interpolation method for gain-scheduling

Presents an efficient method for discrete-time gain-scheduling. The proposed algorithm concerns the interpolation of discrete-time controllers in the particular case of an off-line known trajectory. In spite of this restriction, it allows us to give computable results for a large class of plants. Moreover the specific structure of an observer-based controller is used. In order to illustrate the methodology, an example is given.

Gain Scheduling for an Aerospace Launcher With Bending Modes

Abstract An interpolation method with guaranteed stability is first presented. It can be performed with an LTV (Linear Time Varying) system which parametric trajectory is off-line known. An important point of this method is that it can turn into linear interpolation with some special conditions. This is then performed considering an aerospace application. It concerns a non stationary launcher during the atmospheric phase; the control law has to reject any wind disturbance.

Modeling of a complex-shaped underwater vehicle

A control-oriented modeling approach is proposed for a low-speed semi-AUV (Autonomous Underwater Vehicle) CISCREA, which has complex-shaped structures. Due to the geometry of this AUV, it is very difficult to identify its dynamic and hydrodynamic parameters. Therefore, the main objective of this paper is to find an efficient modeling approach to tune acceptable control design models. The presented solution uses cost efficient CFD (computational fluid dynamic) softwares predicting the two hydrodynamic key parameters: The added mass matrix and the damping matrix. A complete model is built for CISCREA from CFD and verified through experimental results. The results indicate that the proposed computational approach seems to be desirable for the robust control scheme of many complex-shaped AUVs. Finally, Numerical and experimental results are compared.

Multi-objective H2/H∞/Impulse-to-Peak Control of a Space Launch Vehicle

A multi-objective synthesis problem involving H 2 , H ∞ and impulse-to-peak performances is investigated. In general, multi-objective control problems are hard problems to solve and do not have exact solutions. Here, an LMI formulation is proposed for the mixed H 2 /impulse-to-peak optimization under an H ∞ constraint for LTI discrete-time systems. This framework is then used to control the attitude of a space launcher. A particular control structure is defined and a multiobjective H 2 / H ∞ /impulse-to-peak synthesis problem is solved to tackle specific specifications. A systematic synthesis procedure including the tuning of design parameters is defined and results from simulations are presented.

AEROSPACE LAUNCH VEHICLE CONTROL: A GAIN SCHEDULING APPROACH

This paper presents a methodology for designing an aerospace launch vehicle autopilot. Linear controllers are first designed using a multi-objective method based on the Youla parameterization and the optimization under constraints described by linear matrix inequalities. These controllers are then interpolated in such a way that the stability of the closed-loop plant is guaranteed. Results obtained from a nonlinear simulator against wind disturbances and parameter uncertainties are then given.

Launcher Attitude Control: Some Answers to the Robustness Issue

Abstract This paper presents the main results obtained in the frame of PIROLA, a 3 years research working group on robust control of launchers, under financial support of CNES induding ONERA, EADS Space Transportation, the control departments of Supelcc and SUPAERO, and CNRS/LAAS. The first part of the paper addresses the general problem of the attitude control of launchers specially the robustness concern. In the second part the different synthesis methods which have been proposed and tested during the project are described. Some of them address the stationary control problem and have therefore to be associated to an interpolation algorithm to be implemented. Two other methods aim at designing nonstationary controllers. The advantages and limits of each method for this particular problem are emphasized.

Robust gain scheduled control of a space launcher by introducing LQG/LTR ideas in the NCF robust stabilisation problem

A space launcher is a time-varying plant which is known to be hard to control, due to time and frequency-domain constraints and parameters uncertainties. In this paper, this problem is solved by interpolating LTI controllers designed for different instants of the flight. Such controllers are obtained by combining the NCF robust control problem with the LQG/LTR approach, the later being useful to design the compensators included in the first one.

Flexible Arm Multiobjective Control Via Youla Parameterization and LMI Optimization

Abstract An algorithm for multiobjective control is first derived from recent results of Scherer. It allows to use different Lyapunov functions by combining the Youla parameterization, an observer structure and congruence transformations to obtain an LMI formulation. The efficiency of this approach is then tested by considering a benchmark problem: a flexible arm with three different loads.

Sea glider guidance around a circle using distance measurements to a drifting acoustic source

This paper describes a simple yet robust sea glider guidance method in a constellation of Lagrangian drifters under the polar ice cap. The glider has to perform oceanographic measurements, mainly conductivity, temperature and depth, in the area enclosed by the drifters and can not rely on GNSS (Global Navigation Satellite System) positioning data as the polar ice cap makes it impossible to surface. The originality of the presented method resides in 2 points. First, a very simple PID (Proportional, Integral and Derivative) controller based on a basic kinematic model is tuned. Second, the method does not use a localization algorithm to estimate state space model data but interval analysis methods are performed to bound the errors in range to the transponder and its derivative. Moreover, only one acoustic beacon is used. Validation is then performed through simulations.