Ergonomic evaluation of self-propelled Alfalfa harvester

Abstract

This study focused on the ergonomic evaluation of a developed alfalfa harvester by analyzing various factors that impact operator comfort and safety. Ten subjects, aged between 21 and 42 years, were randomly selected for the ergonomic investigation. Key
parameters measured included vibrations, noise levels, heart rate, energy expenditure, Limit of Continuous Performance (LCP), Overall Discomfort Rating (ODR) and Body Part Discomfort Score (BPDS). Vibration levels were evaluated in both vertical and
horizontal directions under transportation and working conditions. The results indicated that vibrations were higher during working conditions, especially as engine speeds increased, following a similar trend as previous studies. Noise levels, measured for both operators and bystanders, also increased with engine speed, with the highest noise level recorded at 92.86 dB for operators at 3000 RPM during work. Heart rate measurements showed an average working heart rate of 108.8 beats.min-1, with energy expenditure
varying from 3.32 to 4.91 kcal.min⁻¹, classifying the harvesting operation as light work. The work pulse (ΔHR) values were all below the LCP threshold of 40 beats.min-1, indicating the suitability of the harvester for continuous operation. The overall discomfort rating (ODR) averaged 3.8, indicating more than light discomfort during operation. The Body Part Discomfort Score (BPDS) averaged 45.5, with maximum discomfort observed in the shoulders, arms, and wrists. These results highlight areas where ergonomic improvements could further enhance operator comfort and reduce strain during alfalfa harvesting.