Laboratoire d’analyse et d’architecture des systèmes
T.GUEROUT, P.LOPEZ, T.MONTEIL, C.ARTIGUES, Y.GAOUA, G.DA COSTA
SARA, ROC, IRIT-UPS
Revue Scientifique : Future Generation Computer Systems, Vol.71, pp.1-17, Juin 2017 , N° 17006
The analysis of the Quality of Service (QoS) level in a Cloud Computing environment becomes an attractive research domain as the utilization rate is daily higher and higher. Its management has a huge impact on the performance of both services and global Cloud infrastructures. Thus, in order to nd a good trade-off, a Cloud provider has to take into account many QoS objectives, and also the manner to optimize them during the virtual machines allocation process. To tackle this complex challenge, this article proposed a multiobjective optimization of four relevant Cloud QoS objectives, using two different optimization methods: a Genetic Algorithm (GA) and a Mixed Integer Linear Programming (MILP) approach. The complexity of the virtual machine allocation problem is increased by the modeling of Dynamic Voltage and Frequency Scaling (DVFS) for energy saving on hosts. A global mixed-integer non linear programming formulation is presented and a MILP formulation is derived by linearization. A heuristic decomposition method, which uses the MILP to optimize intermediate objectives, is proposed. Numerous experimental results show the complementarity of the two heuristics to obtain various trade-offs between the different QoS objectives.
A.CHEREF, A.AGNETIS, C.ARTIGUES, J.C.BILLAUT
ROC, UNISI, LI
Rapport LAAS N°17126, Mai 2017
In this paper, we consider an integrated production and outbound delivery scheduling problem. In particular, we address the situation in which the scheduling sequence and the delivery sequence are the same and predefined. A set of jobs are processed on a single machine and finished jobs are delivered to the customers by a single capacitated vehicle. Each job has a processing time and transportation times between customers are taken into account. Since the sequence is given, the problem consists to form batches of jobs and our objective is to minimize the sum of the delivery times or general functions of the delivery times. The NP-hardness of the general problem is established and a pseudopolynomial time dynamic programming algorithm is given. Some particular cases are treated, for which NP-hardness proofs and polynomial time algorithms are given. Finally, a fixed-parameter tractability result is given.
D.SIMON, A.SEURET, O.SENAME
LIRMM, MAC, GIPSA-Lab
Rapport LAAS N°17125, DOI 10.1080/00207721.2017.1316879, Mai 2017, 11p.
The efficient control of real-time distributed systems, where continuous components are governed through digital devices and communication networks, needs a careful examination of the constraints arising from the different involved domains inside co-design approaches. Thanks to the robustness of feedback control, both new control methodologies and slackened real-time scheduling schemes are proposed beyond the frontiers between these traditionally separated fields. A methodology to design robust aperiodic controllers is provided, where the sampling interval is considered as a control variable of the system. Promising experimental results are provided to show the feasibility and robustness of the approach.
C.ZHANG, N.KHALFET, S.LASAULCE, V.VARMA, S.TARBOURIECH
L2S, CRAN, Vandoeuvre, MAC
Manifestation avec acte : International Workshop on Resource Allocation, Cooperation and Competition in Wireless Networks ( RAWNET ) 2017 du 15 mai au 15 mai 2017, Paris (France), Mai 2017, 6p. , N° 17114
E.PAUWELS, D.HENRION, J.B.LASSERRE
Ouvrage (contribution) : Geometric and Numerical Foundations of Movements, Springer, N°ISBN 978-3-319-51546-5, Mai 2017 , N° 16159
We propose a tutorial on relaxations and weak formulations of optimal control with their semidefinite approximations. We present this approach solely through the prism of positivity certificates which we consider to be the most accessible for a broad audience, in particular in the engineering and robotics communities. This simple concept allows to express very concisely powerful approximation certificates in control. The relevance of this technique is illustrated on three applications: region of attraction approximation, direct optimal control and inverse optimal control, for which it constitutes a common denominator. In a first step, we highlight the core mechanisms underpinning the application of positivity in control and how they appear in the different control applications. This relies on simple mathematical concepts and gives a unified treatment of the applications considered. This presentation is based on the combination and simplification of published materials. In a second step, we describe briefly relations with broader literature, in particular, occupation measures and Hamilton-Jacobi-Bellman equation which are important elements of the global picture. We describe the Sum-Of-Squares (SOS) semidefinite hierarchy in the semialgebraic case and briefly mention its convergence properties. Numerical experiments on a classical example in robotics, namely the nonholonomic vehicle, illustrate the concepts presented in the text for the three applications considered.
S.FERGANI, L.MENHOUR, O.SENAME, L.DUGARD, B.DANDREA NOVEL
DISCO, URCA, GIPSA-Lab, Mines ParisTech
Rapport LAAS N°17112, Mai 2017, 18p.
This paper deals with Global Chassis Control (GCC) of ground vehicles. It focuses on the coordination of suspensions and steering/braking vehicle controllers based on the interaction between the vertical and lateral behaviors of the vehicle. Indeed, the roll motion of the car can generate increasing load transfers that affect considerably the suspension system and vehicle stability. The load transfers can be described using the lateral acceleration. Then, the coordination is highlighted, in this work, through the relationship between the suspension behavior and the lateral acceleration in the framework of the Linear Paramter Varying (LPV) approach. The proposed control law is designed in hierarchical way to improve the overall dynamics of the vehicle. This global control strategy includes two types controllers. The first one is the longitudinal/lateral nonlinear Flatness controller. Based on the adequate choice of the flat outputs, the flatness proof of a 3DoF two wheels nonlinear vehicle model has been established. Then, the combined longitudinal and lateral vehicle control is designed. The algebraic estimation techniques have been used in order to have an accuracy estimation of the derivatives and filtering of the reference flat outputs. Such control strategy is developed in order to cope with coupled driving maneuvers like obstacle avoidance via steering control and stop-and-go control via braking or driving wheel torque. The second part of the proposed strategy consists of the LP V /H∞ suspension controller. This controller uses the lateral acceleration as a varying parameter to take into account the load transfers that affects directly the suspension system and therefore to achieve the desired performance. The coordination between the vehicle vertical and lateral dynamics is highlighted in this study, and the LP V /H∞ framework ensures a specific collaborative coordination between the suspension and the steering/braking controllers. Simulations on a complex full vehicle model have been validated using experimental data obtained on-board vehicle, with an identification procedure on a real Renault Mégane Coupé.
A.BENOIT, M.M.JOLDES, M.MEZZAROBBA
EXT, MAC, LIP6-CNRS
Revue Scientifique : Mathematics of Computation , Vol.86, N°305, pp.1303-1341, Mai 2017 , N° 14329
A wide range of numerical methods exists for computing polynomial approximations of solutions of ordinary differential equations based on Chebyshev series expansions or Chebyshev interpolation polynomials. We consider the application of such methods in the context of rigorous computing (where we need guarantees on the accuracy of the result), and from the complexity point of view. It is well-known that the order-n truncation of the Chebyshev expansion of a function over a given interval is a near-best uniform polynomial approximation of the function on that interval. In the case of solutions of linear differential equations with polynomial coefficients, the coefficients of the expansions obey linear recurrence relations with polynomial coefficients. Unfortunately, these recurrences do not lend themselves to a direct recursive computation of the coefficients, owing among other things to a lack of initial conditions. We show how they can nevertheless be used, as part of a validated process, to compute good uniform approximations of D-finite functions together with rigorous error bounds, and we study the complexity of the resulting algorithms. Our approach is based on a new view of a classical numerical method going back to Clenshaw, combined with a functional enclosure method.
C.GAZZINO, D.ARZELIER, L.CERRI, D.LOSA, C.LOUEMBET, C.PITTET-MECHIN
MAC, ROC, CNES, Thalès Alenia Space
Rapport LAAS N°17110, Avril 2017, 6p.
In this paper, a fuel optimal rendezvous problem is tackled in the Hill-Clohessy-Wiltshire framework with several operational constraints as bounds on the thrust, non linear non convex and disjunctive operational constraints (on-off profile of the thrusters, minimum elapsed time between two consecutive firings...). An indirect method and a decomposition technique have already been combined in order to solve this kind of optimal control problem with such constraints. Due to a great number of parameters to tune, satisfactory results are hard to obtain and are sensitive to the initial condition. Assuming that no singular arc exists, it can be shown that the optimal control exhibits a bang-bang structure whose optimal switching times are to be found. Noticing that a system with a bang-bang control profile can be considered as two subsystems switching from one with control on to with control off, and vice-versa, a technique coming from the switching systems theory is used in order to optimise the switching times.
G.MICHIELETTO, A.CENEDESE, L.ZACCARIAN, A.FRANCHI
RIS, University of Padova, MAC
Rapport LAAS N°17111, Avril 2017, 6p.
A quaternion-based nonlinear control strategy is here presented to steer and keep a generic multi-rotor platform in a given reference position. Exploiting a state feedback structure, the proposed solution ensures the stabilization of the aerial vehicle so that its linear and angular velocity are zero and its attitude is constant. The main feature of the designed controller is the identification of a zero-moment direction in the feasible force space, i.e., a direction along which the control force intensity can be assigned independently of the control moment. The asymptotic convergence of the error dynamics is confirmed by simulation results on a hexarotor with tilted propellers.
S.TARBOURIECH, A.SEURET, L.MOREIRA, J.M.GOMES DA SILVA Jr
Rapport LAAS N°17103, Avril 2017, 6p.
The paper presents an observer-based event-triggered control strategy for linear systems subject to input cone-bounded nonlinearities by using only available measurable variables. Sufficient conditions based on linear matrix inequalities are proposed to ensure the asymptotic stability of the closed loop and the avoidance of Zeno behavior in an emulation context. Based on these conditions, a convex optimization problem to compute the parameters of the event-trigger rule aiming at reducing the number of control updates is proposed. The approach is illustrated on a numerical example that considers the control of a linear system with a logarithmic input quantization constraint.