Transmission characteristics of suspension seats in multi-axis vibration environments

Abstract

The multi-axis vibration transmission characteristics of selected suspension seats were investigated in the laboratory. Subjects were exposed to a flat acceleration spectrum and two low frequency signals extracted from multi-axis acceleration data recorded at the floor of a passenger locomotive. Triaxial accelerations were measured at the floor of the vibration table and at the interfaces between the subject and mounted seat (seat pan and seat back). The transmission ratios between the overall seat pan and seat back accelerations and floor accelerations provided an effective tool for evaluating the effects of measurement site, vibration direction, and posture among the selected seating systems. The results showed that the system transfer matrix, estimated using a multiple-input/single-output model, would be less than ideal for predicting low frequency operational seat vibration when using suspension seats. The Seat Effective Amplitude Transmissibility (SEAT), estimated for the tested locomotive seats, was used to predict the weighted seat pan accelerations and Vibration Total Values for assessing a 1-h operational exposure in accordance with ISO 2631-1: 1997. Relevance to industry Multi-axis SEAT values can be estimated for seating systems tested in the laboratory using representative operational exposures. These values can be applied to monitored vehicle floor accelerations to target potentially harmful vibration in accordance with ISO 2631-1: 1997, assuming the operational exposures have similar frequency and magnitude characteristics. The transmission at the seat back should be considered when substantial low frequency multi-axis vibration is present.