Abstract    Among different goals defined in vehicle design process, fuel consumption (FC) is one of the most important objectives, which significantly has taken into account lately, both by the customers and vehicle manufacturers. One of the significant parameters which impacts the vehicle FC is the efficiency of vehicle's power train. In this paper, a half-toroidal continuously variable transmission (CVT) is considered as the vehicle power train. Its efficiency is sensitive to its geometry, and variation of its geometry can result the vehicle FC reduction. On the other hand, geometry variation affects its weight and fatigue life, which are considered as major contributing factors in the power train design. This paper aims to optimize half-toroidal CVT in order to minimize its weight, FC of the vehicle equipped with it, and provide the desired fatigue life. After introducing half-toroidal CVT, the method of calculating the mentioned objective functions is presented. A specific importance weight for each objective is considered. These weights are functions of their related objectives. A single objective optimization is implemented for each objective, and their optimal values are obtained. Then, these objectives are optimized simultaneously using Global Criterion method.

Keywords    Continuously Variable Transmission, Half-Toroidal, Fuel Consumption, Fatigue Life, Multi-objective Optimization, Importance Weight, Global Criterion

چکیده    در میان اهداف معرفی شده در پروسه طراحی خودرو یکی از مهمترین معیارها مقدار مصرف سوخت خودرو است، که مدنظر هر دو گروه سازنده خودرو و مشتری است. یکی از پارامترهای موثر بر مصرف سوخت خودرو، بازده سیستم انتقال قدرت است. در این مقاله سیستم انتقال قدرت پیوسته (CVT) نصف چنبره، به عنوان سیستم انتقال قدرت خودرو در نظر گرفته می­شود. بازده این مجموعه به هندسه آن وابسته است و تغییر آن می­تواند به کاهش مصرف سوخت خودرو انجامد. از طرفی، تغییر هندسه آن روی وزن و عمر خستگی آن نیز تاثیر می­گذارد. در این مقاله، هدف بهینه­سازی CVT نصف چنبره در جهت کاهش مصرف سوخت خودرو، کاهش وزن آن و تامین مطلوبات سازنده در زمینه عمر خستگی آن است. پس از معرفی CVT نصف چنبره، روش محاسبه توابع هدف بیان شده ارائه می­شود. برای هر کدام از این توابع یک ضریب وزنی تعریف می­شود که مقدار آن به مقدار تابع هدف بستگی دارد. هرکدام از توابع هدف به تنهایی بهینه می­شوند و مقادیر بهینه آنها بدست می­آید. در نهایت، این توابع هدف به صورت همزمان به کمک روش Global Criterion بهینه­یابی می­شوند.

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