bluuebunny/crossref_metadata_2025_split huggingface dataset:
Robust Fault Detection and Isolation for Linear Input Time-Delay Systems
Authors: Yao Y. X. , Kovacevic R. , Zhang Y. M. 
Published: July 2023

Abstract
In this paper, we propose a robust fault detection and isolation method for linear input time-delay systems under unknown disturbances. The factorization approach in the frequency domain is used to obtain results. A parameterization for all residual generators for fault detection is proposed. Based on the results of parameterizations, the robust residual generator design is studied. A performance index that contains a measure of the effects of disturbances and faults is introduced. It is shown that the residual is robust against the disturbance and sensitive to the fault. The application of residual evaluation for such systems is also discussed.
Decentralized Stabilization
Authors: Shahin Ali , Perez Ronald 
Published: July 2023

Abstract
This paper gives an existence condition for decentralized stability which not only includes all known previous results as special cases but also yields a criterion for the solution of the input-output pairing problem. General existence conditions under which the stability of the individual loops of a square multivariable system imply the global asymptotic stability of the multivariable system itself are very useful in practice. They indicate when in principle it is possible to obtain stable closed loop performance of a multivariable system by tuning every loop separately. Such conditions are particularly pertinent in the design of fault tolerant control systems. Of major interest in such design situations is the improved input-output control structure assignment which enhances the desired decentralized stability and control.
A Higher-Order Method for Dynamic Optimization of a Class of Linear Systems
Authors: Agrawal S. K. , Veeraklaew T. 
Published: July 2023

Abstract
This paper deals with optimization of a class of linear dynamic systems with n states and m control inputs, commanded to move between two fixed states in a prescribed final time. This problem is solved conventionally using Lagrange’s multipliers and it is well known that the optimal solution satisfies 2n first-order linear differential equations in the state and Lagrange multiplier variables.
In this paper, a new procedure for dynamic optimization is presented that does not use Lagrange multipliers. In this new procedure applied to a class of linear systems with controllability index p=nm, optimal solution satisfies m differential equations of order 2p. The boundary conditions on these m variables are computed in terms of higher derivatives (up to p – 1) at the initial and final time. These higher-order differential equations are solved using classical weighted residual methods, methods relatively unknown to controls community but extremely popular with researchers in mechanics. This new procedure for dynamic optimization, higher order necessary condition solved by weighted residual method, is computationally more efficient compared to other conventional procedures, offering benefits for real-time applications.
Perturbation Analysis of Global Bifurcations in Parametrically Excited Systems With Zero-to-One Internal Resonance
Authors: Feng Z. C. 
Published: July 2023

Abstract
In this work we study the existence of Silnikov homo-clinic orbits in the averaged equations representing the modal interactions between two modes with zero-to-one internal resonance. The fast mode is parametrically excited near its resonance frequency by a periodic forcing. The slow mode is coupled to the fast mode when the amplitude of the fast mode reaches a critical value so that the equilibrium of the slow mode loses stability. Using the analytical solutions of the unperturbed integrable Hamiltonian system, we evaluate a generalized Melnikov function which measures the separation of the stable and the unstable manifolds of an annulus containing the resonance band of the fast mode. This Melnikov function is used together with the information of the resonances of the fast mode to predict the region of physical parameters for the existence of Silnikov homoclinic orbits.
On an Improved Simple Cell Mapping Unravelling Algorithm
Authors: Guttalu Ramesh S. 
Published: July 2023

Abstract
The cell mapping method has attractive features for studying global behavior of nonlinear dynamical systems, especially for locating stable periodic solutions and their domains of attractions. A major hurdle in practical implementation of the method for analyzing higher order system is due to its computational memory requirements. The storage of the cell map itself forms a significant portion of the overall memory requirement for cell mapping analysis. In this paper, we outline a procedure for eliminating the storage requirement for the cell map by modifying the existing simple cell mapping unraveling algorithm. The key factor in the modification comes from the analysis of an individual cell sequence originating from a given cell and how its ultimate mapping sequence is determined before a new sequence is generated. Since such a sequence must terminate in either a sink cell or a periodic motion, we propose a modified algorithm which combines this feature effectively with the existing algorithm. The utility of the proposed unraveling algorithm is demonstrated by computing bifurcation of periodic solutions of a strongly nonlinear mechanical system. Some features of the dynamic behavior are analyzed to show the existence of periodic solutions and chaotic behavior.
Analysis of a Coulomb Friction Damper for Suppressing Oscillations of Drive Shafts of Vehicles
Authors: Wang Xinchao , Noah Sherif , Vahabzadeh Hamid 
Published: July 2023

Abstract
To improve fuel efficiency of automatic transmissions, their torque converters are typically locked up at about 40 mph after which 100% of the torque is transmitted from the engine to the transmission. One cause of fuel inefficiency is the viscous losses in the torque converter at lower vehicle speeds due to slippage between the pump and turbine of the transmission’s torque converter. Consequently, the automotive industry has been experimenting with imposing an early lock-up of the torque converter to enhance fuel efficiency. However, damping in the driveline would drastically be reduced. A sudden excitation could then lead to oscillation of the drive shafts which is transmitted to the occupants of the vehicle. This could cause an unpleasant driving experience.
One proposed solution concerns an inline friction damper to be integrated with the drive shafts of the vehicle in such a way that friction damping only occurs when oscillations of the shafts occur. The study reported here deals with a comprehensive nonlinear transient analysis of the proposed Coulomb friction damper which was performed to assess the effectiveness of the damper.
Two cases involving a sudden loading of the drive shafts at two levels of disturbance (at second and third gear) are studied. One case considers the response of the driveline to a sudden application of torque when the torque converter is already locked. The second case examines the consequences of a sudden lock-up of the converter clutch.
The study shows that the second case will create more severe oscillatory response of the drive shaft. The results of the parametric study for the effects of the friction damper on the oscillations of the drive shafts reveal varied levels of generated damping and overshoot. For some parameters, the amount of damping and/or reduction of overshoot is not significantly improved. This has been found to result from a non-slip condition which occurs at the friction damper surfaces. To remedy this situation, a passive slip control mechanism is used to vary the normal force on the surfaces of the friction pads with the angle of shaft twist. Another approach was to use a preloading arrangement with the friction damper. A discussion is included to provide physical insight into the performance of the friction damper in controlling the transient response of the drive shafts.
Lyapunov Feedback Design for Stabilization of Stall and Surge in Axial Compressors
Authors: Krstić Miroslav 
Published: July 2023

Abstract
We design a feedback controller that globally stabilizes stall and surge instabilities in a nonlinear compressor model. This is achieved with a backstepping design which avoids cancellation of the system’s useful nonlinearities — the nonlinearities that would otherwise be cancelled in a feedback linearizing design. The resulting control law is extremely simple and optimal with respect to a non-quadratic cost functional that is meaningful for the compressor model. As in a previous bifurcation-theoretic design, we change the character of the bifurcation at the stall inception point from subcritical to supercritical, however, since we use Lyapunov tools, our controller also achieves global stability.
Global Chaos Control in a Periodically Forced Oscillator
Authors: Lenci S. , Rega G. 
Published: July 2023

Abstract
The problem of controlling the chaotic response of a simple mechanical system — an inverted pendulum subjected to an external periodic base excitation — has been analyzed.
The controlling procedure consists in inhibiting the transverse homoclinic intersection by acting on the shape of the excitation. The optimal solution of the global control problem, i.e., the excitation which simultaneously breaks the right and left intersections and thus reduces the chaos region as much as possible, has been obtained.
A preliminary numerical analysis has been carried out in order to test the theoretical predictions of the global problem as well as of the one side problem previously analysed by the same and by other authors.
Feedback Control of Chaos via Liapunov-Floquet Transformation
Authors: Ravindra B. , Boghiu Dan , Sinha S. C. 
Published: July 2023

Abstract
A general framework for local control of chaos in non-autonomous systems using feedback strategies is considered in this work. The present approach falls under the attempts to use conventional Lyapunov type methods to control chaos in nonlinear systems. It is important to note that in the past, some studies related to control of chaos in non-autonomous systems were incorrect because the authors ignored time varying nature of the problem. In the present work, due consideration is given to the non-autonomous nature of the problem in choosing the control law. The general approach presented is specialised to the case of a sinusoidally driven Duffing’s oscillator to illustrate the control scheme.
Stability of Multi-Degree of Freedom Stochastic Nonlinear Systems
Authors: Whalen Timothy M. 
Published: July 2023

Abstract
Melnikov’s method for finding necessary conditions for homoclinic chaos is extended to a class of stochastically forced multi-degree of freedom nonlinear systems. The stochastic forcing induces a stochastic Melnikov process, and simple zeros of this process imply transversal intersection of appropriate stable and unstable manifolds. This process can also provide information on probabilities of escape and mean exit rates from regions of phase space. In generalizing results from single degree of freedom stochastic systems, however, some new concepts (and reinterpretations of old concepts) are addressed.
Applications are presented to the dynamics of a feedback controlled buckled column subject to stochastic forcing. The stochastic Melnikov process is calculated, and illustrations of the effect of system parameters on system dynamics and chaos are given. The use of the Melnikov process as an estimator of mean exit rates from preferred regions of phase space is investigated.
Nonlinear Control of Flexible Structures
Authors: Oueini Shafic S. , Nayfeh Ali H. , Pratt Jon R. 
Published: July 2023

Abstract
An approach for implementing an active nonlinear vibration absorber for distributed-parameter systems is presented. The technique is based on exploiting the saturation phenomenon exhibited by multidegree-of-freedom systems with quadratic nonlinearities possessing a two-to-one autoparametric resonance. The strategy consists of introducing a second-order controller and coupling it with the plant through a sensor and an actuator, where both the feedback and control signals are quadratic. Once the plant is forced near resonance, its response saturates to a small value, and the remaining oscillatory energy is channeled into the controller. We present theoretical and experimental results of the application of the proposed saturation controller. The plant under consideration consists of a flexible beam. The feedback signal is generated by a strain gage, and the actuation is achieved through piezoceramic patches attached to the beam. The equations of motion are developed and analyzed through perturbation techniques. Then, the controller is built in electronic components, and the strategy is tested by regulating the response of a steel cantilevered beam.
Modal Coupling of a Cantilever Beam Attached to a Rotating Body
Authors: Lee Christopher L. , Murphy Kevin D. 
Published: July 2023

Abstract
This is an investigation into the nonlinear dynamics of a cantilever beam attached to a rotating body; specifically, the near resonant response of one in-plane mode and one out-of-plane mode of the beam (with respect to the horizontal plane of rotation) driven by a periodic out-of-plane excitation. The modes are coupled through quadratic and cubic nonlinear terms arising from nonlinear axial stretching and large amplitude displacements. The natural frequencies of the modes are commensurate in a near one-to-one ratio.
The existence and stability of periodic solutions are examined using a second-order perturbation analysis. Regions for system parameters are identified where single or multi-mode responses occur.
The effects of beam foreshortening and centrifugal stiffening as well as gyroscopic effects are included which capture the dominant characteristics of rotating systems such as helicopter blades, robot arms, flexible machinery, and satellite bodies with flexible appendages.
Instabilities in a Two Degree of Freedom Torsional System Driven by a Hooke’s Joint
Authors: Asokanthan Samuel F. , Meehan Paul A. 
Published: July 2023

Abstract
Torsional instabilities in a drive-line which incorporates a Hooke’s joint due to fluctuating angular velocity ratio across the joint are examined. Numerical simulations and bifurcation analysis performed on the full nonlinear equations further demonstrate the existence of parametric, quasi-periodic and chaotic instabilities. Onset of chaotic motion was shown to be characterised by a quasi-periodic route. Predicted instabilities indicate the range of drive shaft speeds to be avoided during the design of a drive-line which employs a Hooke’s joint.
Prediction and Control of Dynamics for a Class of Oscillators With Nonlinear Restoring Force
Authors: Natsiavas S. , Mitsi S. , Tsiafis I. 
Published: July 2023

Abstract
An analysis is presented for two degree of freedom weakly nonlinear oscillators, with symmetric restoring force. Conditions of 1:3 internal resonance and subharmonic resonance of the lower linear natural mode are assumed to be satisfied simultaneously. Initially, a set of slow-flow equations is derived, governing the amplitudes and phases of approximate response, by applying an asymptotic analytical method. Determination of approximate periodic steady-state motions of the system is then reduced to solution of sets of polynomial equations which is performed analytically. Then, a systematic search is performed based on this analysis, revealing effects of the system parameters on the existence and stability properties of periodic steady-state motions for an example mechanical system. The results are first presented in the form of frequency-response diagrams and attention is focused on understanding the evolution and interaction of the various solution branches as the internal resonance detuning parameter is varied. In addition, numerical integration of the slow-flow equations reveals that for some parameter combinations they accept periodic solutions, corresponding to quasiperiodic motions of the mechanical system.
Nonlinear Dynamics of a Fluid-Conveying Cantilevered Pipe With a Small Mass Attached at the Free End
Authors: Païdoussis Michael P. , Semler Christian 
Published: July 2023

Abstract
In this paper, the planar dynamics of a fluid-conveying cantilevered pipe with a small mass attached at the free end (’end-mass’, for short) is examined theoretically and experimentally. An experimental study is undertaken with elastomer pipes conveying water, with metal or plastic end-masses. The main purpose is to extend the work of Copeland and Moon on a modified configuration: the motion is constrained to be planar instead of three-dimensional, and the pipe is modelled as a beam having a non-negligible flexural rigidity instead of a string hanging under gravity. As in previous studies, it is demonstrated that for the system with no end-mass, only one stable periodic solution exists, at least for the parameters considered. On the other hand, in the presence of a small end-mass, the dynamics is much richer and different types of periodic solutions are found to exist. Jump phenomena as well as chaotic oscillations are observed both in the experiments and numerically, revealing the importance of even a small mass on the dynamics. Qualitative and quantitative agreement between theory and experiments is rather good.
Modeling of Porosity Effects in Gas-Filled Composites Using Biot’s Parameter
Authors: Salamon N. J. , Ganesan R. 
Published: July 2023

Abstract
Modeling of porosity effects on the thermal-chemical decomposition of porous, polymer composites at high temperature is treated analytically for no gas flow and compared with finite element results which permit gas flow. A function is proposed for the variation of Biot’s pressure-stress coupling factor in terms of porosity and a constant which can be determined from experiments. The results show this function adequately describes the coupling factor and that the inclusion of gas flow (permeability) is essential to accurate results.
A Micromechanical Model for Layered Porous Materials
Authors: Wu Yinan , Katsube Noriko 
Published: July 2023

Abstract
A micromechanical model for porous layered materials has been developed. The micromechanical approach for layered materials is combined with a poroelastic constitutive model. Explicit expressions for effective elastic moduli, thermal expansion coefficients, and poroelastic moduli are obtained. The effect of pore pressure on the overall deformation of the composites is described by the effective poroelastic constants. The obtained results reduce to those of layered materials when there are no pores. Applications of the obtained model to thermochemically decomposing composites are discussed.
Microscopic Examination of Titanium Matrix Composites Subjected to Testing Designed to Cause Varying Dominant Damage Mechanisms
Authors: Calcaterra J. R. , Johnson W. S. 
Published: July 2023

Abstract
Titanium Matrix Composites (TMC’s) like SCS-6/Timetal 21S are envisioned for use as a structural material for advanced aircraft and in the next generation of turbine engine. In general, damage in representative temperature and load regimes can be dominated by either mechanical, environmental or time dependent deformation and damage mechanisms. Mechanical deformation, present under all load conditions, includes mechanisms such as matrix yielding and fiber/matrix debonding. Time dependent deformation refers to either the creep or relaxation of the matrix and will typically occur at moderately high elevated temperatures. Environmental damage is also time dependent but is distinguished by the fact that it describes the chemical interaction of the composite and the environment. Environmental damage in SCS-6/Timetal 21S composites is commonly thought to be caused by the oxygen embrittlement of the matrix. This damage type becomes prevalent at high elevated temperatures which are near the operational limit of the material. Testing has been completed at Georgia Tech to separate the three damage types listed above. This test matrix involved isothermal constant amplitude fatigue tests at temperatures of 400, 500 and 650°C with hold times at the maximum stress varying from 1 to 100 seconds. Testing was conducted on laminates with stacking sequences of both [0/±45/90]s and [90/±45/0]s. The changes in stacking sequence yielded significant differences in cyclic lives for identical test conditions. Fractographic examination of the specimens indicate that the true cause for environmental attack is not the formation of brittle oxides, but the coarsening of the alpha grains in the microstructure. This form of damage is shown to affect the fracture morphology of specimens at all temperatures, but proper selection of the stacking sequence can reduce the importance of this effect and increase cyclic lives.
Edge Stresses in a Laminated Composite Strip Subjected to Axial Temperature Gradients
Authors: Swett Dwight W. , Shiflett Geoffrey R. 
Published: July 2023

Abstract
One of the most severe problems associated with the use of laminated composite structures in thermal environments is the susceptibility to delamination due to the edge effect stresses arising from the thermal expansion mismatch between the constituent laminae. In addition, the problem may be compounded by the introduction of extreme thermal gradient effects as well. Trade studies to develop a satisfactory design for these types of thermal environments have heretofore been rather limited due to the lack of accurate analytical assessments for the edge effects that arise from these thermal loads. The predominant amount of investigation for these types of thermal gradient problems has been restricted to detailed numerical finite element analyses that do not lend to rapid concurrent engineering design processes. No analytical solution has been available to address the thermoelastic edge effects in composite laminates resulting from thermal gradients.
In this paper, a combination of Airy stress functions and direct displacement functions is utilized to obtain the plane elasticity solution for the stresses and displacements in a multilayer laminated anisotropic strip subjected to a temperature gradient that is arbitrarily symmetric in the longitudinal direction. The solution cannot be guaranteed to satisfy the free edge normal traction requirement since only resultant force is enforced to zero; however, convergence for enforced zero transverse slope at the strip ends can be established, as the eigenfunctions are orthogonal. Thus the solution is exact for these edge conditions. Numerical results are presented for several examples and compared to those obtained from our own MSC/NASTRAN finite element analyses. The correlation with the finite element numerical results was determined to verify the solution and indicated application of the solution as an approximation to free edge engineering problems is very reasonable for a broad range of practical cases involving temperature gradient effects.
Structural Response of Oxidation Resistant Carbon-Carbon Composites
Authors: Ashley T. H. , Ochoa O. O. 
Published: July 2023

Abstract
The experimental assessment as well computational simulation of time, temperature, and oxidation dependent material properties of carbon-carbon composites with inhibited matrix is undertaken. The material system examined is HITCO 2D CC137EH, highly inhibited (boron carbide particulates), eight harness satin weave, RT42 CVD SiC coated carbon-carbon composite laminate.
Two representative cells; namely in-plane and through-the-thickness of this architecture, are developed to interpret the material properties and mechanical response of the laminate with two dimensional finite elements. The mechanical loading is treated as both monotonic and cyclic. Effective properties and the thermo-mechanical response of the laminate simulated by the models follow closely the experimental data.