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This paper discusses the problem of marking constraints in a class of partially controllable timed Petri nets. Specifically, these are Timed Event Graphs (TEGs) which include disturbed input transitions and which are subject to token capacity constraints in some paths. Using the Min-Plus algebra formalism, formal approaches are proposed to design causal control laws to guarantee compliance with marking constraints in TEGs. Sufficient conditions are defined to show the existence and synthesis of these controllers. The developed methodologies are illustrated in a case study of a disassembly system with a limited stock of components. [ABSTRACT FROM AUTHOR]

Particle impact dampers are dissipative devices that can easily be coupled to structures in order to reduce vibrations over a wide frequency range and in adverse environmental conditions. In this work, a multiple-sphere chain impact damper is coupled to a cantilever beam in order to attenuate its flexural motions. This simple configuration was chosen to better understand the energy dissipation phenomena by the device when the beam is subjected to random excitations. In addition, a parametric study of the coupled system is conducted in order to assert optimal working conditions of the damper. This study is mostly based on a numerical model of the vibro-impacting system, which was calibrated based on an experimental rig. Firstly, the computational modal basis of the bare beam was experimentally identified, and then theoretically modified taking into account the mass of the container. Secondly, calibration of the impact model was achieved by fitting the parameters of the contact formulation with respect to sphere-dropping experiments. Finally, extensive parametric computations are presented and discussed. The vibratory responses are computed using a frequency banded Gaussian random excitation, for several values of the excitation amplitude, for an increasing number of spheres and for several values of the damper clearance. The numerical results concern the r.m.s. motion of the spheres and the beam, the r.m.s. spheres/beam contact forces, the average mechanical and dissipated energies by the beam modes and the damper, as well as the effective beam modal parameters when fitted with the damper, which are essential results for understanding these damping devices. Finally, the numerical results are reduced into relevant dimensionless parameters, which prove reasonably effective in collapsing the dynamical data from such a highly nonlinear system. The present study thus highlights interesting essential features on the dynamics of structures coupled to multiple particle vibro-impact dampers under random excitation. [ABSTRACT FROM AUTHOR]

This paper discusses the problem of control laws for Discrete Event Dynamic Systems (DEDSs) represented by Timed Event Graphs (TEGs) under Generalized Marking Constraints (GMCs). The behaviour of TEGs is described using linear equations while GMCs are expressed by weighted inequalities in Min-Plus algebra. We formulate the problem in terms of control linear Min-Plus models. Hence, an algebraic method to calculate control laws ensuring the respect of GMCs is suggested. And once sufficient conditions are satisfied, we propose casual feedbacks to guarantee these marking specifications. Besides, the proposed control strategy is applied to a dual-armed cluster tool, a well-known industrial application. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of the uncertainties interaction in the design parameters of a two-stage gearbox of a wind turbine. The purpose of the dynamic study is to minimize the linear displacements in order to have more stability. The uncertainty consideration using a unique parameter, allowed the identification of the influence of this latter on the dynamic response, in addition to its extreme values. The examination of multivariate parameters investigates the interaction of these parameters. Thus, the gear system dynamic behavior was studied by taking into account the uncertainty with a suggested diagram: uncoupled form to evaluate the impact of each parameter and coupled form based on the progressive interaction of uncertain dynamic parameters using the multivariate uncertainty method. For this purpose, the generalized polynomial chaos approach (GPC) was applied to simulate the dynamic behavior of the wind turbine gearbox. The obtained results were then verified using Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

This research examines a Progressive Damage Model for laminated composites using a wave-based technique. Using conventional numerical methodologies, such studies may require a significant amount of CPU time. Compared to standard techniques, the approach proposed can provide a quick and cost-effective evaluation. This work presents a numerical approach for dealing with periodic media subjected to an impact load that can provide damage initiate and evolution. The proposed model is based on a hybrid formulation for the wave-damage interaction that describes wave scatterings, as well as a stress analysis of a composite structure subjected to an impact force. The failure analysis is carried out by identifying the damage location and then describing the modification of the material properties of the damaged elements using Hashin's failure criteria and material property degradation rules. A comparison of stress distribution with results from the conventional finite element approach was performed in order to confirm the hybrid WFE/FE method, and good agreement was noted. Finally, an impact on a composite beam was studied. The evolution of the structural failure is presented. This article takes into consideration material degradation over time. [ABSTRACT FROM AUTHOR]