Abstract The efficiency of suspension seat can be influenced by several factors such as the input vibration, the dynamic characteristics of the seat and the dynamic characteristics of the human body. The objective of this paper is to study the effect of sitting postures and vibration magnitude on the vibration transmissibility of a suspension system of an agricultural tractor seat. Eleven (11) healthy male subjects participated in the study. All subjects were asked to sit on the suspension system. Four (4) different sitting postures were investigated – i) “relax”, ii) “slouch”, iii) “tense”, and iv) “with backrest support”. All subjects were exposed to random vertical vibration in the range of 1–20 Hz, at three vibration magnitudes - 0.5, 1.0 and 2.0 m/s2 r.m.s for 60 s. The results showed that there were three pronounced peaks in the seat transmissibility, with the primary resonance was found at 1.75–2.5 Hz for every sitting postures. The “backrest” condition had the highest transmissibility resonance (1.46), while the “slouch” posture had the highest Seat Effective Amplitude Transmissibility (SEAT) values (64.7%). Changes in vibration magnitude for “relax” posture from 0.5 to 2.0 m/s2 r.m.s resulted in greater reduction in the primary resonance frequency of seat transmissibility. The SEAT values decreased with increased vibration magnitude. It can be suggested that variations in posture and vibration magnitude affected the vibration transmission through the suspension system, indicating the non-linear effect on the interaction between the human body and the suspension system. Relevance to industry: Investigating the posture adopted during agricultural activities, and the effects of various magnitudes of vibration on the suspension system's performance are beneficial to the industry. The findings regarding their influence on the human body may be used to optimize the suspension system's performance.

中文翻译：

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姿态和振动幅度对拖拉机悬挂系统垂直振动传递率的影响

摘要 悬浮座椅的效率受输入振动、座椅动态特性和人体动态特性等多种因素的影响。本文的目的是研究坐姿和振动幅度对农用拖拉机座椅悬挂系统振动传递率的影响。十一 (11) 名健康男性受试者参与了该研究。所有受试者都被要求坐在悬挂系统上。研究了四 (4) 种不同的坐姿——i)“放松”，ii)“懒散”，iii)“紧张”，以及 iv)“有靠背支撑”。所有受试者均暴露于 1-20 Hz 范围内的随机垂直振动，三种振动幅度 - 0.5、1.0 和 2.0 m/s2 rms，持续 60 秒。结果表明，座椅传递率有三个明显的峰值，每个坐姿的主要共振频率为 1.75-2.5 Hz。“靠背”条件具有最高的传递共振（1.46），而“懒散”姿势具有最高的座椅有效振幅传递（SEAT）值（64.7%）。“放松”姿势的振动幅度从 0.5 到 2.0 m/s2 rms 的变化导致座椅传递性的主要共振频率的更大降低。SEAT 值随着振动幅度的增加而降低。可以认为姿势和振动幅度的变化影响了通过悬架系统的振动传递，表明对人体与悬架系统之间的相互作用的非线性影响。与行业的相关性：调查农业活动中采取的姿势，以及各种振动幅度对悬挂系统性能的影响，对行业有益。关于它们对人体影响的研究结果可用于优化悬架系统的性能。