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Jorge Chávez,Omar Jiménez Alemán,Martín Flores Martínez,Héctor J. Vergara‑Hernández,Luis Olmos,Pedro Garnica‑González,Didier Bouvard 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.2
The design and fabrication of a bilayer Ti6Al4V–Ti6Al4V/30Ta component were performed by using the powder metallurgyprocess and solid-state sintering as the consolidation step. Phase change and sintering densifcation of the component werestudied by dilatometry. The addition of 30 vol% of Ta to the Ti6Al4V matrix had a noticeable efect over the microstructuraland mechanical properties of the alloy, which showed decrements of up to 12.2 and 21.5% in nano-hardness and elastic modulus, respectively. The decrement of these properties strongly afected the wear and corrosion performance of the component. Special attention was focused on the intermediate zone between layers denoted by a transition zone, which presented betterwear response because of the properties and microstructure caused by the gradient difusion of Ta. Ti6Al4V/30Ta alloyshowed an improved corrosion behaviour compared to Ti6Al4V alloy, decreasing 2.4 times their susceptibility to corrosionand about two orders of magnitude their corrosion rate. The bilayer component in this study is proposed as an alternative todecrease the consumption of expensive materials with improved properties.
A New Observer Design for Systems in Presence of Time-varying Delayed Output Measurements
Boubekeur Targui,Omar Hernández-González,Carlos-Manuel Astorga-Zaragoza,Gerardo-Vicente Guerrero-Ramírez,María-Eusebia Guerrero-Sánchez 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.1
This paper presents a state observer for linear systems and Lipschitz nonlinear systems with delayedoutput measurements, which are affected by a known and bounded time-varying delay. The structure of the proposedobserver is based on a proportional-integral term, which allows to compensate the time-varying delay. The observergain depends on the maximum bounded delay. This gain is computed by a Linear Matrix Inequality (LMI) approach. The observer exhibits good performance for state estimation of the system despite the presence of significantly longdelay. A Lyapunov-Krasovskii functional is used to prove the asymptotical convergence to zero of the observationerror. This observer is applied to the case of systems with time-varying delay whose dynamic is described by apiecewise differentiable function. Examples and numerical simulations are provided in order to support the validityof the main results.