Assessment of a ride comfort number for agricultural tractors: A simplified approach

Abstract

Farming activities cause operators to experience whole body vibration (WBV), which may result in back injuries. Studies have shown that despite a wide variability when operating a tractor, the accelerations arising from “ground input” have similar spectral trends making it possible to simplify and standardise the driver comfort testing procedures. Based on the recommendations of three standards on WBV measurement, a single scalar value (Ride Number – RN) has been defined and used to characterise the vibration comfort of agricultural tractors. The operation of ten tractors equipped with different damping systems on a standard test track (ISO 5008:2002) at three speeds (10, 12, 14 km h−1) has resulted in the acquisition of accelerations along the x, y and z axes at the seat. The RN was calculated by averaging the overall total values of vibration (aw) calculated for each speed. Data processing has shown that machine settings (tyre size and pressure, tractor mass) significantly affect the RN so as to achieve the recommendations for proper tractor settings. It has been observed that at each speed, the relative contribution of the components (aw10, aw12 and aw14) ranged from −12% to +11.5% showing that obtaining the RN by averaging them arithmetically was a suitable procedure. According to principal component analysis, great part of the accounted variance can be explained by accelerations acquired on the y and z axes, distinguishing between tractors with and without suspension. Thus the RN obtained can be used to compare a given tractor when provided with different equipment.