بررسي ارگونوميكي مكانيزم‌هاي ترمز و گاز تراكتورهاي MF285 و MF399 به روش الكتروميوگرافي

Ergonomic assessment of brake and accelerator mechanisms of MF285 and MF399 tractors using electromyography method

توجه به وضعیت ارگونومیكی كاربران ماشین‌های كشاورزی یكی از اهداف مكانیزاسیون كشاورزی می‌باشد. از ‌این‌‌رو، این پژوهش با به‌كارگیری روشی جدید به بررسی وضعیت ارگونومیك مكانیزم‌های ترمز و گاز تراكتورهای MF285 و MF399 پرداخت، بدین‌ترتیب كه فعالیت الكتریكی عضلات دوقلوی داخلی، دوقلوی خارجی، پهن داخلی، پهن خارجی، كوادراتوس لومباروم و تراپزیوس فوقانی كاربران قبل، در حین و پس از استراحت بعد از فشردن پدال‌های ترمز و گاز توسط دستگاه بیوویژن ثبت شد. نتایج تجزیه و تحلیل داده‌ها نشان داد كه عضلات پهن داخلی و دوقلوی داخلی با نسبت RMS بعد از 60 ثانیه فشردن پدال نسبت به قبل آن به‌ترتیب با 47/2 و 97/1 بیش‌ترین فعالیت الكتریكی را در حین استفاده از مكانیزم ترمز تراكتور MF285 داشتند. عضلات دوقلوی داخلی و دوقلوی خارجی كاربران نیز بیش‌ترین تنش را در هنگام فشردن پدال ترمز تراكتور MF399 داشتند. به‌طور كلی، عضلات پهن داخلی و تراپزیوس فوقانی در حین استفاده از ترمز تراكتور MF285 تحت تنش بیش‌تری نسبت به تراكتور MF399 قرار گرفتند، در حالی‌كه عضلات دوقلوی داخلی، دوقلوی خارجی، پهن خارجی و كوادراتوس لومباروم طی به‌كارگیری مكانیزم ترمز تراكتور MF285 تحت تنش كم‌تری نسبت به تراكتور دیگر قرار گرفتند. عضلات كوادراتوس لومباروم و دوقلوی داخلی كاربران در حین فشردن پدال گاز تراكتور MF285 به‌ترتیب بیش‌ترین نسبت فعالیت الكتریكی را داشتند. درحالی‌كه كاربران تراكتور MF399 بیش‌ترین تنش را در حین استفاده از پدال گاز بر روی عضلات پهن داخلی و دوقلوی خارجی متحمل می‌شوند. به‌طور كلی، نسبت فعالیت الكتریكی تمام عضلات به‌جز عضله پهن خارجی در حین استفاده از پدال گاز تراكتور MF285 بیش‌تر از تراكتور MF399 بود و كاربران این تراكتور در حین استفاده از مكانیزم گاز این تراكتور در شرایط نامطلوب‌تری قرار داشتند.

Introduction: Too many people are working in the agricultural sector and therefore, pay more attention to the safety and health at work in the agricultural sector is important. This issue is more important in developing industrial countries where the level of the ergonomic working condition is less than that of developed countries. Attention to ergonomic condition of agricultural machinery drivers is one of the goals of agricultural mechanization. Therefore, in this study the ergonomic conditions of brake and accelerator mechanisms for MF285 and MF399 tractor 's drivers were investigated using a new method. Materials and Methods: 25 people were selected for experiment. The electrical activity of Medialis gastrocnemius, Lateralis gastrocnemius, Vastus medialis, Vastus lateralis, Quadratus Lumborum and Trapezius muscles of drivers before and during pressing the pedal and after rest time were recorded using Biovision device. Measurements were performed for each person on each muscle 30 seconds before pressing the pedal, 60 seconds after pressing the pedal and after 60 seconds of rest. For all drivers, the muscles on the right side (brake and accelerator side) have been selected and tested. The measurements were performed in compliance with appropriate time intervals between the measurements. Results and Discussion: Ergonomic assessment of brake pedal: The results showed that the RMS electrical activity of muscles of Vastus medialis and Medial gastrocnemius, during 60 seconds braking were 2.47 and 1.97. So, Vastus medialis and Medial gastrocnemius had the highest stress during pressing the MF399 tractor 's brake pedal. Moreover, the Medial gastrocnemius and Lateral gastrocnemius with RMS electrical activity ratio of 2.47 and 1.74 had the highest RMS electrical activity ratio respectively, during 60 seconds braking compared to before braking of MF285 tractor. The comparison of results showed that the Vastus medialis and Trapezius had the higher stress during braking of MF285 tractor than that of MF399 tractor, while, muscles of Medialis gastrocnemius, Lateralis gastrocnemius, Vastus lateralis, Trapezius and Quadratus Lumborum showed the lower stress during braking of MF285 tractor. Ergonomic assessment of accelerator: During 60 seconds pressing the accelerator pedal for MF285 the RMS electrical activity of muscles of Quadratus Lumborum and Medialis gastrocnemius were 3.25 and 2.15. So, these muscles had the highest stress during pressing the accelerator pedal for MF285. Drivers of MF399 tractor experienced high stress in their Vastus lateralis and Lateralis gastrocnemius muscles during pressing the accelerator pedal. The results highlighted that for all muscles, except Vastus lateralis, the electrical activity ratio during pressing the accelerator pedal of MF285 tractor were higher than that for MF399 tractor. Conclusions: To conclude, Vastus medialis and Trapezius had the higher stress during braking of MF285 tractor than that of MF399 tractor, while, muscles of Medialis gastrocnemius, Lateralis gastrocnemius, Vastus lateralis, Trapezius and Quadratus Lumborum showed the lower stress during braking of MF285 tractor as compared with the other model of tractor. Generally in all muscles, except Vastus lateralis, the electrical activity ratio during pressing the accelerator pedal of MF285 tractor was higher than that for MF399 tractor and the drivers need more effort while pressing the accelerator pedal and drivers of this tractor had adverse condition while using the accelerator mechanism. Acknowledgements: The research leading to these results has received funding from the Ferdowsi University of Mashhad, Iran, is gratefully acknowledged. Gratitude also goes to Dr. Mohammad Hossein Abbaspour-Fard, Hossein Fallahi and Mehdi Mahjour for their guidance and support throughout parts of this research.