Power tiller vibration transmitted to hand and body of operator in transportation mode on asphalt rural road.

Power tillers are used for field applications as well as on transportation of agricultural products and human beings on rural roads. These machines generate high levels of vibrations due to lack of suspension system. The power tiller operators work in harsh environment and then their ergonomic characteristics has a great importance. In the present paper, the vibration transmitted to hand-arm and whole-body of a power tiller operator was evaluated. The vibration acceleration signals for evaluation were obtained in a field experiment using a 13-hp power tiller. Experiments were conducted at five levels of engine speed, four levels of transmission gear ratio, two positions of accelerometer, and in the lateral, longitudinal and vertical directions in transportation mode on asphalt rural road. Number of three accelerometers was used for measuring the vibration acceleration. An analogue output of the accelerometers was converted to digital ones by using A/D converter. The time domain vibration acceleration signals were stored in laptop computer hard disk. The recorded digital signals in time domain were converted to frequency domain using a developed fast Fourier transform (FFT) computer program. The amount of vibration damage on operator's body and the exposure limits were calculated in accordance with the ISO standards. The results showed that the vibration acceleration was increased with increasing the engine speed at all gear ratios and directions for both positions of handle and seat. The vibration acceleration was the highest values at vertical direction for all of experiments. For 8 hours daily exposure was observed that the vibration transmitted to the hand was more than 11 m/s and then after 2.4 year exposure in 10% of operators of the power tiller various diseases and disorders, and depreciation on their fingers may occur. As the results the equivalent vibration transmitted from the power tiller seat to body of operator was in the range of 0.5 to 1 m/s (uncomfortable range). So the exposure time should be lower than 8 hours/day. It is necessary to reduce the vibration transmitted to the user’s hand and body by designing and developing adequate insulating systems or isolators.