The association between fear of falling and smoothness of lower trunk oscillation in gait varies according to gait speed in community-dwelling older adults

BackgroundFear of falling (FoF) is common in community-dwelling older adults. FoF and increased walking speed are associated with lower trunk oscillation during gait in older adults. We hypothesized that older adults with FoF would struggle to walk safely when instructed to walk faster than usual.MethodsParticipants included 260 community-dwelling older adults aged over 65 years (mean age = 71.9 ± 3.9 years) who were able to walk independently without an assistive device. Participants were instructed to walk along a 15-m smooth horizontal walkway at self-selected normal and fast gait speeds. During the middle 10 m of the walk, oscillation of the lower trunk and stride times were measured with two accelerometers. We examined associations between gait variables, including harmonic ratio (HR) in vertical, mediolateral (HR-ML) and anteroposterior (HR-AP) directions as indicators of smoothness of lower trunk oscillation, as well as stride time variability (STV) and FoF.ResultsGait-speed- and STV- adjusted models showed that FoF was significantly associated with HR-ML in the normal-gait condition (HR-ML: β = - .135, p = .040), while FoF was significantly associated with HR-AP in the fast-gait condition (HR-AP: β = - .154, p = .017).ConclusionsFoF-related changes in gait vary with gait speed. In older adults with FoF, lower trunk oscillation was less smooth in the lateral direction when they walked at their usual pace. In addition, lower trunk oscillation was also less smooth in the direction of travel when they walked at a faster pace than their usual walking speed

Experimental verification of an inertial mass electromagnetic transducer with mechanical motion rectifier

15th International Workshop on Advanced Smart Materials and Smart Structures Technology (ANCRiSST 2024) to be held in July 2024 at Kyoto University, Japan.Various kinds of devices employing inerter technologies, which can produce an amplified inertial force proportional to the relative acceleration of both ends, have been proposed for the purposes of structural control and energy harvesting. In these devices, generally, a viscous damping element to absorb vibration energy is employed along with the inerter. In the conventional inerter mechanism, however, the velocity of the inerter decays to zero when the direction of vibration changes, resulting in a reduction in the energy absorption capability of the viscous damping element. To address this issue, inerter-integrated devices that use a mechanical motion rectifier (MMR) to constrain the behavior of the inerter in one direction have been proposed in the field of vibration energy harvesting. In this research, a prototype of an inertial mass electromagnetic transducer with MMR is fabricated. The inertial mass electromagnetic transducer has the same configuration as an inertial mass damper (IMD) and consists of an inerter and a motor instead of a viscous damper. Sinusoidal waves are input to the prototype using an actuator, and the behaviors of the proposed mechanism under various conditions are examined. The obtained results show that the prototype behaves as expected and can absorb vibration energy efficiently

Numerical evaluation of a two-body point absorber wave energy converter with a tuned inerter

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Feasibility Study of Actively-Controlled Tuned Inertial Mass Electromagnetic Transducers for Seismic Protection

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Development and performance evaluation of an electromagnetic transducer with a tuned variable inerter

This paper proposes a novel vibration energy harvesting device employing a tuned variable inerter. The inerter is a device that can produce an amplified inertial mass effect by ball screw or rack and pinion mechanisms. Originally, the inerter was developed for suspensions in automobiles, and various kinds of inerter technologies have been widely studied not only in structural control but also in energy harvesting so far. As an example of such devices, the tuned inertial mass electromagnetic transducer has been proposed, and its effectiveness as an energy harvesting device has been shown already. However, at the same time, previous studies suggested that further performance improvement is possible if the inerter is variable according to changes in disturbance conditions. Thus, in this research, a prototype which can change the value of the inerter is designed, and a system to change the inerter based on the dominant frequency detected online by the fast Fourier transform of the measured data is developed. Then, it is shown through experimental studies that the proposed device can improve the energy harvesting performance compared to the existing tuned inertial mass electromagnetic transducer for disturbances with varying dominant frequencies.journal articl

Structural control strategies for earthquake response reduction of buildings

Destructive seismic events continue to demonstrate the importance of mitigating these hazards to building structures. Structural control has been considered one of the most effective strategies to protect buildings from extreme dynamic events such as earthquakes and strong winds, and has been applied to numerous real buildings in recent years. Structural control strategies can be divided into four categories: passive, active, semi-active, and hybrid control. Because passive control systems are well understood and require no external power source, they have been accepted widely by the engineering community. However, these passive systems have the limitation of not being able to adapt to structural changes and to varying usage patterns and loading conditions. While active systems are able to adapt various conditions, they require a significant amount of power to generate the necessary large control forces; guaranteeing the availability of such power during seismic events is challenging. Moreover, the stability of active systems is not ensured. To compensate for the drawbacks of passive and active systems, semi active control systems have been proposed. Semi-active control devices possess the adaptability to flexible external inputs, do not require large power sources, and do not have the potential to destabilize the structural system. However, semi-active control has been slow to be accepted by engineering practitioners. The focus of this dissertation is the improvement and the validation of semi-active control strategies, especially with magnetorheological (MR) dampers, for building protection from severe earthquakes. To make semi-active control strategies more practical, further studies on both the numerical and experimental aspects of the problem are conducted. In the numerical studies, new algorithms for semi-active control are proposed. First, the nature of control forces produced by active control systems is investigated. The relationship between force-displacement hysteresis loops produced by the linear quadratic regulator (LQR) and the linear quadratic Gaussian (LQG) algorithms is explored. Then, new simple algorithms are proposed, which can produce versatile hysteresis loops. Moreover, the proposed algorithms do not require a model of the target structure to be implemented, which is a significant advantage. The seismic performance of the proposed algorithms on a scaled three-story building model is compared with the LQG-based clipped-optimal semi active control and LQG active control cases. In the experimental studies, the effectiveness of semi-active control strategies are shown through real-time hybrid simulation (RTHS) in which a MR damper is tested physically. In this dissertation, two new structural control methods proposed in the literature recently are investigated, i.e., smart outrigger damping systems for high-rise buildings and smart base isolation systems consisting of passive base isolations and semi-active control devices. The accuracy of the RTHS employing the model-based compensator for MDOF structures with a semi-active device is discussed as well. The research presented in this dissertation contributes the improvement and prevalence of semi-active control strategies in building structures to mitigate seismic damage

Structural control with tuned inertial mass electromagnetic transducers

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Outrigger tuned inertial mass electromagnetic transducers for high-rise buildings subject to long period earthquakes

This paper proposes outrigger tuned inertial mass electromagnetic transducer (TIMET) systems for high-rise buildings subject to long period earthquake excitations. The proposed outrigger TIMET systems consist of the outrigger and TIMET parts. The outrigger damping systems have been proposed as a novel energy dissipation approach to high-rise buildings, in which control devices are installed vertically between the outrigger and perimeter columns to achieve large energy dissipation. While the TIMET has been developed based on the mechanism of the tuned viscous mass damper (TVMD) which can improve energy absorbing capability by taking advantage of resonance effect. However, instead of a viscous material, the damping of the TIMET is provided by a motor which can convert mechanical energy to electrical energy. The focus of this study is to investigate the structural control performance and energy harvesting efficiency of the proposed outrigger TIMET system for high-rise buildings subjected to long period earthquakes through numerical simulations

Numerical study of a point absorber wave energy converter with tuned variable inerter

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Structural Control Strategies for Earthquake Response Reduction of Buildings

Destructive seismic events continue to demonstrate the importance of mitigating these hazards to building structures. To protect buildings from such extreme dynamic events, structural control has been considered one of the most effective strategies. Structural control strategies can be divided into four classes: passive, active, semi-active, and hybrid control. Because passive control systems are well understood and require no external power source, they have been accepted widely by the engineering community. However, these passive systems have the limitation of not being able to adapt to varying conditions. While active systems are able to do that, they require a significant amount of power to generate large control forces. Moreover, the stability of active systems is not ensured. The focus of this report is the improvement and the validation of semi-active control strategies, especially with MR dampers, for building protection from severe earthquakes. To make semi active control strategies more practical, further studies on both the numerical and experimental aspects of the problem are conducted. The research presented in this report contributes the improvement and prevalence of semi-active control strategies in building structures to mitigate seismic damage.Financial support for this research was provided in part by the Long Term Fellowship for Study Abroad by the MEXT (Ministry of Education, Culture, Sports, Science, and Technology, Japan) and the Newmark Account.Ope