Vibration analysis during grass harvesting according to ISO vibration standards
This research evaluated the working efficiency and comfort of operation by measuring vibration acceleration of tractors during grass harvesting. A real-time kinematic global positioning system and an inertial measurement unit installed in a tractor normally used by farmers during grass harvesting were used to acquire tractor vibration acceleration data. Analysis of the position and vibration acceleration data of tractors by a Fourier transformation yielded a power spectrum of vibration acceleration at each frequency (110Hz) and position. The root mean square of vibration acceleration at each frequency (110Hz) was calculated with the center frequency of the 1/3 octave bands (1.0,1.25,1.6,2.0,2.5,3.15,4,5,6.3,8,and 10Hz) based on ISO standards. To evaluate the working efficiency in the grassland, geographical information system maps were generated using the power spectrum of vibration acceleration and the limit on working time for each frequency that negatively affected the tractor driver. The vibration acceleration in the longitudinal (ax) and lateral (ay) directions at the center frequency of the 1/3 octave band below 2.0Hz exceeded the fatigue-decreased proficiency and reduced the comfort boundaries stipulated in ISO 2631 (1974). In the area where working characteristics are severe, the vibration acceleration in the vertical direction (az) is high. The vibration acceleration in the az direction at the center frequency of the 1/3 octave band (510Hz) clearly indicates discomfort during grass harvesting and a decrease in the work efficiency beyond 1h. The total vibration acceleration (a?) at the center frequency of 5.0Hz of the 1/3 octave band served to evaluate comfort in the whole field during grass harvestingthe a? value is higher than that at other frequencies. The area with severe working characteristics showed a higher a? value at the center frequency of 8.0Hz than that at other frequencies.
vibration acceleration fourier transformation iso standard rtk-gps imu 1/3 octave band center frequency