Abstract
Pendulum structure refers to release the rotational freedom of the structure and the foundation, so that the structure and component can lift, swing with descending manner or rotate with ...fixed center under the action of external forces, so as to control the intraformational deformation distribution mode of the structure. Because the building structure is inevitably damaged to a certain extent under the action of strong earthquake, the purpose of “repairable” will be achieved if the damaged part and degree of the structure can be effectively controlled. In this case, Housner found out in the 1960s that the upward lifting of buildings could protect the structure itself, which became the initial discussion of modern pendulum shock absorption system. Currently, pendulum structures have developed into a variety of branches and damping forms. This article classifies and summarizes the new developments of pendulum structures in the past 20 years from three directions, namely pendulum walls, pendulum columns and pendulum frames. It gives its own views and prospects on the future development of pendulum structures.
This article presents an energy-based method for examining the dynamics of an autoparametric double pendulum with quadratic coupling. The method is based on decomposing the total energy (Hamiltonian) ...into partial terms and studying these terms in the time domain. The article then demonstrates using this method to analyse internal resonances in various regimes, including regular periodic, quasiperiodic, and chaotic motion. This study also explores higher-order resonances linked to the geometric tuning parameter and initial energy, which enrich the complexity of the system. The work focuses on identifying conditions that lead to the development of internal resonances and analysing energy exchange mechanisms at various initial energy levels. This analysis uses Fast Lyapunov Indicators and Poincaré maps for these higher energy levels to identify chaotic regimes. Within these regimes, the assessment of coupling energy contributes to a deeper understanding of the studied system. Moreover, the research demonstrates how energy-based methods can be used to investigate auto-parametric systems.
•Energy-based approach for autoparametric pendulum with quadratic coupling.•In-depth exploration of internal resonances across motion types.•Chaos detection using Fast Lyapunov Indicators.•Higher-order resonances linked to system parameters revealed.•Method applicable for various autoparametric systems.
In this paper, pole placement and two optimal control techniques which are the linear quadratic regulator and linear quadratic Gaussian are compared. A cart and inverted pendulum which is an ...inherently unstable dynamical system is used as a case study to analyze their performance and stability margins. Lagrangian equations defining the system dynamics are converted to linear state-space representation. The objective is to keep the pendulum in an upright position as the cart on which it is mounted moves from one position to another. MATLAB is used to solve the optimization problem and simulate the step response of the system. The robustness of both controllers is measured by giving uncertain model parameters to the system and observing the level of uncertainty these controllers can handle. The simulation results justify the relative advantages of these control schemes.
The paper investigates a nonlinear vibration mitigation strategy of a variable length pendulum subjected to a harmonic external excitation. A nonlinear absorber in a form of a tri-pendulum system is ...used to reduce the response of the primary pendulum. Thus, the paper investigates a non-stationary problem of nonlinear vibration mitigation of the primary pendulum using another nonlinear passive pendulum absorber. Due to genuine interest in capturing the nonlinear dynamic interaction, the paper numerically studies the performance of the primary mass and absorber, first, by constructing 2D maps in the unrestrained parametric space, which demonstrate the qualitative behavior of the system. Then, the surrogate optimization technique is used to tune the absorber’s parameters within a given bounded set of parameters’ values. The optimization is conducted based on a priori known reeling speed or acceleration/deceleration of the primary pendulum, thereby completely removing the need for acquiring a current system states essential for active feedback control. The obtained numerical results validate the proposed strategy and demonstrate high performance of the nonlinear passive absorber when it is properly tuned.
This paper introduces a method for identifying internal resonance regimes in free-vibrating systems with multiple nonlinear couplings, illustrated using a chain of two Rott’s pendula. The method ...based on decomposing Hamiltonian and subsequent treatment of the coupling energies allows for a comprehensive understanding of autoparametric system behaviour. A novel signal-processing-based coupling energy evaluation significantly enhances the effectiveness of the method, revealing internal resonances with slow energy exchange. In the theoretical part, a general step-by-step procedure applicable to any conservative coupled oscillators is introduced. We demonstrate that concerning such free-vibrating systems, the proposed method effectively uncovers internal resonances influenced by system parameters, initial conditions, and the initial energy of the system. Through an illustrative example of the system with multiple quadratic couplings, we also show that slow energy exchange occurs for sum and difference internal resonances.
•Identifying internal resonances using decomposition of Hamiltonian.•General procedure applicable to any conservative oscillator.•Novel signal-processing boosts efficiency, revealing slow energy exchange modes.•Illustrative demonstration via chain of two Rott’s pendula.
Triboelectric nanogenerator (TENG) has received tremendous attention in ambient energy harvesting, especially for ocean wave energy. However, the technology is generally challenged to obtain ...excellent durability and high efficiency simultaneously, which primarily overshadows their further industrial‐scale applications. Here, a dual‐mode and frequency multiplied TENG with ultrahigh durability and efficiency for ultralow frequency mechanical energy harvesting via the elastic connection and soft contact design is proposed. By introducing the spring and flexible dielectric fluff to the novel pendulum‐like structural design, the surface triboelectric charges of TENG are replenished in soft contact mode under the intermittent mechanical excitation, while the robustness and durability are enhanced in non‐contact working mode. The fabricated TENG results in a continuous electrical output for 65 s by one stimulus with a high energy conversion efficiency, as well as negligible change of output performance after a total of 2 000 000 cycles. Moreover, integrated with the power management circuit, the TENG array is demonstrated to drive the electronics by effectively harvesting wind and water wave energy as a sustainable energy source. This work paves a new pathway to enhance the robustness, durability, and efficiency of the TENG that resolves the bottleneck of its practical applications and industrialization.
An elastic‐connection and soft‐contact strategy to simultaneously promote the robustness, durability, and efficiency of a triboelectric nanogenerator by introducing an assisted spring and flexible dielectric fluff with a pendulum‐like structural design is proposed, achieving continuous long‐term working and an energy conversion efficiency of 29.7% for one stimulus due to the multiplied frequency output performance.
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