Gain scheduled flight control law for a flexible aircraft : A practical approach

Abstract: This paper presents a gain-scheduling method applied to flight control law design. The method is a stabilitypreservinginterpolation technique ofexisting controllers under observer-state feedback form. Application is made on a flexible civil aircraft example considering multiple scheduling parameters. Although the interpolation technique gives powerful a priori stability guarantees, the sufficient condition to satisfy leads to conservative results in practice. We thus use a fixed observer model and check stability andperformance thanks to μ-analysis. Provided results are really satisfactory for a final controller of little complexity

Multi-level fine pointing test-bed for space applications

For space applications that need high accuracy pointing of the payload, fine pointing system is an indispensable tool. To reach high level of high accuracy pointing and tracking, proper synchronization between the attitude of the satellite and each stage of the pointing module should be considered. This study focuses on developing and demonstrating staging control for fine pointing system. Currently, an experimental model for multi-stage control has been built in the laboratory to be used as a testbed and a teaching tool to validate the control strategies. This paper gives a brief introduction of the study, experimental model design criteria and staging control strategy. An example of a controller synthesis for multi-stage actuators based on Hinfinity is also presented

Robust scheduled control of longitudinal flight with handling quality satisfaction

Classic flight control systems are still widely used in the industry because of acquired experience and good understanding of their structure. Nevertheless, with more stringent constraints, it becomes difficult to easily fulfil all the criteria with these classic control laws. On the other hand, modern methods can handle many constraints but fail to produce low order controllers. The following methodology proposed in this paper addresses both classic and modern flight control issues, to offer a solution that leverages the strengths of both approaches. First, an H∞ synthesis is performed in order to get controllers which satisfy handling qualities and are robust withrespect to mass and centre of gravity variations. These controllers are then reduced and structured by using robust modal control techniques. In conclusion, a self-scheduling technique is described that will schedule these controllers over the entire flight envelope

Robust control of longitudinal flight with handling qualities constraints

Classical flight control systems are still widely used in industry because of acquired experience and good understanding of their structure. Nevertheless, with more stringent constraints, it becomes difficult to easily fulfill all the criteria with this classical control laws. This article aims at showing that this problem can be solved by first designing a high order controller satisfying all the constraints, then by reducing and structuring it in order to make it look like a classical controller. Firstly, an H∞ synthesis is performed in order to get a robust controller versus mass and center of gravity variations, which will satisfy the handling qualities; then it will be reduced by using robust modal control techniques

Control of a launcher in atmospheric ascent with guardian maps

This paper describes the synthesis of a SISO scheduled controller for a launcher vehicle. The problem consists in designing a control law which will be valid on the atmospheric ascent trajectory from time 25 s to time 60 s, while ensuring robustness and performance requirements. Moreover a flexible model with two bending modes is considered, making the problem more challenging. An algorithm based upon guardian maps has been retained in order to find an a priori fixed architecture controller. The algorithm yields a sequence of controllers that ensures that pole confinement constraints are fulfilled for any time between 25 s and 60 s. The user can then interpolate those controllers to find a scheduled controller with respect to time

Controller parametric robustification using observer based formulation and multimodel design technique

This paper deals with equivalent observer based structure and controller robustification. The purpose of the method is to improve the parametric robustness of an initial controller, synthesized, for example, by using H∞ or μ technics. The method is based on equivalent Luenberger observer formulation and multimodel design procedure for the parametric robustification. Matrices of the equivalent ”feedforward+observer +feedback” controller are synthesized to guarantee the same closed loop eigenstructure and input/output transfert as the initial controller (without any restriction on the initial controller order). Afterwards, they are used to initialize an iterative design procedure aiming at improving the parametric robustness. This procedure is based on real-μ analysis and multimodel eigenstructure assignment (using the observer based formulation). Due to the observer structure, improvement of the parametric robustness of the initial controller without paying attention to the closed loop poles coming from the controller dynamic is obtained. Another advantage of the equivalent observer based formulation lies in the fact that it would directly be used to schedule the controller (dynamic and feedback parts). Finally the global method (equivalent observer plus robustification) is applied on the robust control of the space shuttle described in μ-analysis and synthesis toolbox

Optimisation des phases de vol pour un drone capable de vol stationnaire et de vol en translation rapide

Les travaux présentés dans ce papier reprennent l'ensemble des aspects abordés lors de l'automatisation d'un système qui se veut être autonome : la modélisation, la linéarisation, la synthèse de loi de commande, la simulation, le pilotage, le guidage et l'optimisation. Le support expérimental est un micro-drone dont le domaine de vol est élargi(de la capacité de vol stationnaire "comme un hélicoptère" au vol d’avancement rapide "comme un avion"). Les points abordés ici sont plus particulièrement, la modélisation, la linéarisation, le pilote pour le vol stationnaire et le pilote longitudinal pour les transitions de phases de vol autonomes effectuées par séquencement de gains. Nous indiquerons également la structure du simulateur complet non linéaire qui permet de tester les lois réalisées avant de les embarquer. A la fin de l'article, les perspectives et la suite des travaux seront présentées

Unsupervised Classification for Tiling Arrays: ChIP-chip and Transcriptome

Tiling arrays make possible a large scale exploration of the genome thanks to probes which cover the whole genome with very high density until 2 000 000 probes. Biological questions usually addressed are either the expression difference between two conditions or the detection of transcribed regions. In this work we propose to consider simultaneously both questions as an unsupervised classification problem by modeling the joint distribution of the two conditions. In contrast to previous methods, we account for all available information on the probes as well as biological knowledge like annotation and spatial dependence between probes. Since probes are not biologically relevant units we propose a classification rule for non-connected regions covered by several probes. Applications to transcriptomic and ChIP-chip data of Arabidopsis thaliana obtained with a NimbleGen tiling array highlight the importance of a precise modeling and the region classification

Modeling & control of a space robot for active debris removal

Space access and satellites lifespan are increasingly threatened by the great amount of debris in Low Earth Orbits (LEO). Among the many solutions proposed in the literature so far, the emphasis is put here on a robotic arm mounted on a satellite to capture massive debris, such as dead satellites or launch vehicle upper stages. The modeling and control of such systems are investigated throughout the paper. Dynamic models rely on an adapted Newton-Euler algorithm, and control algorithms are based on the recent structured H infinity method. The main goal is to efficiently track a target point on the debris while using simple PD-like controllers to reduce computational burden. The structured H infinity framework proves to be a suitable tool to design a reduced-order robust controller that catches up with external disturbances and is simultaneously compatible with current space processors capacities