Ergonomic characteristics of a power tiller Vibration in transportation

Power tillers or two wheel tractor are the main sources of power supply in small and medium size farms. They also engaged on transportation of agricultural products and human beings on rural roads. Due to lack of suspension system, and operators work in harsh environment, these machines generate high levels of vibrations, so their ergonomic characteristic has a great importance. In this research, hand-arm transmitted vibration (HTV) and whole-body vi-bration (WBV), transmitted from a power tiller on transportation mode, investigated throughout experiments that conducted at five levels of engine speed, four levels of transmis-sion gear ratio, two position of accelerometer (handle and trailer seat) and in the lateral, lon-gitudinal and vertical directions in transportation on asphalt rural road. The recorded digital time domain signals, were converted to frequency domain and then 1/3 octave spectrum of vibration acceleration was calculated. 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 increased with increasing the engine speed at all gear ratios and directions. The vibration acceleration was the highest values at vertical direction for all of experiments. For 8-hour daily exposure was observed that the vibration transmitted to the hand was more than 11 m/s2 and then after 2.32 year exposure in 10% of operators. 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/s2 (uncomfortable range), and 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.

کلیدواژه ها:

power tiller ، vibration ، ergonomic ، exposure limits