Nonlinear Oscillations: Exact Solutions and their Approximations

A handover is a complex collaboration, where actors coordinate in time and space to transfer control of an object. This coordination comprises two processes: the physical process of moving to get close enough to transfer the object, and the cognitive process of exchanging information to guide the transfer. Despite this complexity, we humans are capable of performing handovers seamlessly in a wide variety of situations, even when unexpected. This suggests a common procedure that guides all handover interactions. Our goal is to codify that procedure.To that end, we first study how people hand over objects to each other in order to understand their coordination process and the signals and cues that they use and observe with their partners. Based on these studies, we propose a coordination structure for human-robot handovers that considers the physical and social-cognitive aspects of the interaction separately. This handover structure describes how people approach, reach out their hands, and transfer objects while simultaneously coordinating the what, when, and where of handovers: to agree that the handover will happen (and with what object), to establish the timing of the handover, and to decide the configuration at which the handover will occur. We experimentally evaluate human-robot handover behaviors that exploit this structure and offer design implications for seamless human-robot handover interactions.

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Toward seamless human-robot handovers

Nonlinear energy sink (NES) is an appropriately designed nonlinear oscillator without positive linear stiffness. NES can suppress vibrations over a wide frequency range due to its targeted energy transfer characteristics. Thus, investigations on NES have attracted a lot of attention since a NES was proposed. Designs, analysis, and applications of NESs are still active since different configurations are needed in various practical circumstances. The present work provides a comprehensive review of state-of-the-art researches on NESs. The work begins with a survey of the generation of a NES and its important vibration control characteristics. The work highlights possible complex dynamics resulting in a NES coupled to a structure. The work also summarizes some significant design on the implements of optimal damping effects and the offsets of NES shortcomings. Then, the work details the applications of NESs in all engineering fields. The concluding remarks suggest further promising directions, such as NESs for multidirectional vibration reduction, NESs with nonlinearities beyond the cubic, potential deterioration caused by a NES, low-cost NESs, NESs for extremely low frequency range, and NESs integrated into active vibration controls. There are 383 references in the review, including some publications of the authors.

Designs, analysis, and applications of nonlinear energy sinks

Nonlinear breathing vibrations of eccentric rotating composite laminated circular cylindrical shell subjected to temperature, rotating speed and external excitations

Elimination of multimode resonances of composite plate by inertial nonlinear energy sinks

Nonlinear static and dynamic hygrothermal buckling analysis of imperfect functionally graded porous cylindrical shells

This paper investigates the nonlinear free vibration and nonlinear dynamic hygrothermal buckling behavior of imperfect functionally graded carbon nanotube-reinforced composite (FG-CNTRC) cylindrical panels under hygrothermal environment. The nonlinear temperature distribution is assumed along the thickness direction. The structure is resting on a generalized nonlinear viscoelastic foundation which is composed of a two-parameter Winkler-Pasternak foundation augmented by a Kelvin-Voigt viscoelastic model with a nonlinear cubic stiffness and damping considerations. The nonlinear von Karman strain-displacement relations and the classical shell theory are considered to derive the governing equations of the cylindrical panels. The discretized equations of motion are obtained using the Galerkin method. The fourth order Runge-Kutta method is utilized to analyze the nonlinear dynamic hygrothermal buckling. The influences of the four CNTs distribution types, consist of the FG-O, FG-Λ, FG-X, and UD, are considered for the cylindrical panel. The effects of temperature, moisture, nonlinear viscoelastic foundations, initial imperfection, and material parameters on the nonlinear free vibration and nonlinear dynamic hygrothermal buckling behavior of the system are investigated.

Nonlinear hygrothermal vibration and buckling analysis of imperfect FG-CNTRC cylindrical panels embedded in viscoelastic foundations

Nonlinear vibration of imperfect FG-CNTRC cylindrical panels under external pressure in the thermal environment

Investigations of energy absorption using tuned bistable nonlinear energy sink with local and global potentials

In this paper, an analytical method is used to study the nonlinear primary resonance of imperfect spiral stiffened functionally graded (SSFG) cylindrical shells with internal stiffeners. The SSFG cylindrical shell is surrounded by linear and nonlinear elastic foundation and the effect of structural damping on the system response is also considered. The material properties of the shell and stiffeners are assumed to be continuously graded in the thickness direction. Three-parameter nonlinear elastic foundation model is consists of two-parameter linear elastic foundation (Winkler and Pasternak) and one hardening/softening cubic nonlinearity parameter. Based on the von Karman nonlinear equations and the classical plate theory of shells, the strain–displacement relations are derived. The smeared stiffener technique is used to the model of the internal stiffeners. Using the Galerkin method, the partial differential equations of motion are discretized. The nonlinear primary resonance is analyzed by means of the multiple scales method. The effects of various geometrical characteristics, material parameters and elastic foundation coefficients are investigated on the nonlinear primary resonance.

Nonlinear primary resonance of imperfect spiral stiffened functionally graded cylindrical shells surrounded by damping and nonlinear elastic foundation

Habib Ahmadi

Papers

Nonlinear static and dynamic hygrothermal buckling analysis of imperfect functionally graded porous cylindrical shells

Nonlinear hygrothermal vibration and buckling analysis of imperfect FG-CNTRC cylindrical panels embedded in viscoelastic foundations

Nonlinear vibration of imperfect FG-CNTRC cylindrical panels under external pressure in the thermal environment

Investigations of energy absorption using tuned bistable nonlinear energy sink with local and global potentials

Nonlinear primary resonance of imperfect spiral stiffened functionally graded cylindrical shells surrounded by damping and nonlinear elastic foundation