The hypothesis of equal wave speeds for stabilization of Timoshenko beam is not necessary anymore: the time delay cases†

2019 ◽  
Vol 84 (4) ◽  
pp. 763-796 ◽  
Author(s):  
D S Almeida Júnior ◽  
I Elishakoff ◽  
A J A Ramos ◽  
L G Rosário Miranda
Keyword(s):  
Time Delay ◽  
Timoshenko Beam ◽  
Solid Mechanics ◽  
Type Systems ◽  
Recent Contribution ◽  
Wave Speeds ◽  
Delay Effects ◽  
Timoshenko Systems ◽  
Stability Results ◽  
Second Spectrum

AbstractIn the current study, we consider the Bresse–Timoshenko type systems and we prove some stability results for time delay cases into setting of so called simplified Bresse–Timoshenko equations (or truncated version of Bresse–Timoshenko equations) according to contributions of Elishakoff et al. (2010, Advances in Mathematical Modeling and Experimental Methods for Materials and Structures. Solid Mechanics and Its Applications. Springer: Berlin, 249–254.; 2015, Celebrating the Centenary of Timoshenko’s study of effects of shear deformation and rotary inertia. Appl. Mech. Rev.67, 1–11.; 2017, Critical contrasting of three versions of vibrating Bresse-Timoshenko beam with a crack. Int. J. Solids Struct. 109, 143–151.). These equations are free of the so-called ‘second spectrum’ phenomenon, and they have important consequences on stabilization setting. Specifically, following Almeida Júnior and Ramos (2017, On the nature of dissipative Timoshenko systems at light of the second spectrum. Z. Angew. Math. Phys.68, 31.) in a recent contribution that shows that damping effects eliminate the consequences of this spectrum for equal wave propagation velocities, we prove that time delay effects are able of stabilizing the truncated version regardless of any relationship between coefficients of system. It is concluded that dissipative truncated versions of Bresse–Timoshenko equations are advantageous over the classical Bresse–Timoshenko equations in stabilization context.

Time Delay Effects on Compactability of Soil-Cement Materials during Proctor Testing

2021 ◽  
pp. 036119812199870
Author(s):  
W. Griffin Sullivan ◽  
Isaac L. Howard
Keyword(s):  
Time Delay ◽  
Vital Role ◽  
Test Method ◽  
Dry Density ◽  
Soil Cement ◽  
Delay Effects ◽  
Proctor Test ◽  
Negative Effect ◽  
Departments Of Transportation ◽  
Cement Mixtures

The Proctor test method, as specified in AASHTO T134 and ASTM D558, continues to play a vital role in design and construction quality control for soil-cement materials. However, neither test method establishes a methodology or standardized protocols to characterize the effects of time delay between cement addition and compaction, also known as compaction delay. Compaction delay has been well documented to have a notably negative effect on compactability, compressive strength, and overall performance of soil-cement materials, but specification tools to address this behavior are not prevalent. This paper aims to demonstrate the extent of compaction delay effects on several soil-cement mixtures used in Mississippi and to present recommended new test method protocols for AASHTO T134 to characterize compaction delay effects. Data presented showed that not all soil-cement mixtures are sensitive to compaction delay, but some mixtures can be very sensitive and lead to a meaningful decrease in specimen dry density. Recommended test method protocols were presented for AASHTO T134 and commentary was presented to provide state Departments of Transportation and other specifying agencies a few examples of how the new compaction delay protocols could be implemented.

scholarly journals Overlapping Decentralized Controller Design for Descriptor-type Systems with Distributed Time-delay

2021 ◽  
Vol 20 ◽  
pp. 257-263
Author(s):  
Altug Iftar
Keyword(s):  
Time Delay ◽  
Large Scale ◽  
Controller Design ◽  
Original System ◽  
Type Systems ◽  
Large Scale System ◽  
Decentralized Controllers ◽  
Distributed Time Delay

Decentralized controller design using overlapping decompositions is considered for descriptor-type systems with distributed time-delay. The approach is based on the principle of extension. In this approach, a given large-scale system is decomposed overlappingly into a number of subsystems and expanded such that the overlapping parts appear as disjoint. A decentralized controller is then designed for the expanded system. This controller is then contracted for implementation on the original system. It is shown that if the decentralized controllers are designed to stabilize the expanded system and to achieve certain performance, then the contracted controller, which would have an overlapping decentralized structure, will stabilize the original system and will achieve corresponding performance

scholarly journals Controller Design for Descriptor-type Systems with Distributed Timedelay Using Extension

2021 ◽  
Vol 20 ◽  
pp. 27-32
Author(s):  
Altug Iftar
Keyword(s):  
Time Delay ◽  
Controller Design ◽  
Original System ◽  
Type Systems ◽  
Distributed Time Delay

Controller design using extension is considered for descriptor-type systems with distributed time-delay. The approach is useful in decentralized controller design using overlapping decompositions. In this approach, a given largescale system is decomposed overlappingly into a number of subsystems and expanded such that the overlapping parts appear as disjoint. Since the subsystems appear as disjoint for the expanded system, it is easier to design a descentralized controller for the expanded system. This controller is then contracted for implementation on the original system. In the present paper, it is shown how to contract such a controller to guarantee stability and desired performance for the original system

Time Delay Effects on Dynamic Patterns in a Coupled Neural Model

2000 ◽  
pp. 268-275
Author(s):  
Seon Hee Park ◽  
Seunghwan Kim ◽  
Hyeon-Bong Pyo ◽  
Sooyeul Lee ◽  
Sang-Kyung Lee
Keyword(s):  
Time Delay ◽  
Neural Model ◽  
Delay Effects ◽  
Dynamic Patterns

Optimally designed Lyapunov–Krasovskii terminal costs for robust stable–feasible model predictive control of uncertain time-delay nonlinear dynamical systems

2020 ◽  
pp. 095965182095219
Author(s):  
S Yaqubi ◽  
MR Homaeinezhad
Keyword(s):  
Time Delay ◽  
Dynamical Systems ◽  
Model Predictive Control ◽  
Predictive Control ◽  
Robust Stability ◽  
Control Algorithm ◽  
Nonlinear Dynamical Systems ◽  
Prediction Horizon ◽  
Delay Effects ◽  
Uncertain Time

This article details a new Model Predictive Control algorithm ensuring robust stability and control feasibility for uncertain nonlinear multi-input multi-output dynamical systems considering uncertain time-delay effects. The proposed control algorithm is based on construction of a Lyapunov–Krasovskii functional as terminal cost. Incorporation of this terminal cost into the Model Predictive Control optimization problem and calculation of the associated admissible set result in robust feasibility and robust stability of closed-loop system in presence of uncertain time-delay effects and bounded disturbance signals. The Lyapunov–Krasovskii functional term is constructed with respect to predicted sliding functions over the prediction horizon and considers the effects of dynamical variations over the prediction horizon in generation of control inputs. As dynamical variations are investigated in a sample-to-sample basis, feasible sliding regions are updated at each sample as well. Finally, based on expression of sliding functions as a combination of dynamical variations and input-based terms, required control inputs are calculated in the admissible bound by the optimization algorithm. Construction of control scheme on this basis permits straightforward calculation of robust stability and feasibility conditions for a general class of uncertain nonlinear system in finite prediction horizon whereas in the previous works, often-restrictive conditions were considered for the investigated dynamical systems. Numerical illustrations indicate precision and efficiency of control algorithm and improved stability and convergence rate for multivariable nonlinear dynamical systems considering uncertain time-delay effects. Finally, hardware-in-the-loop implementation indicates applicability of the proposed scheme in real-time control applications particularly in case appropriate compromises between optimality and calculation speed are considered.

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