[동력전달계부문] 자동차용 휠 베이렁 유닛의 해석 및 설계 방법에 관한 연구 : Part 2 - 최적 설계

This is the second part of two companion papers, the first of which is "A Study on the Analysis and Design Method of Automotive Wheel Bearing Unit: Part I - System Life Evaluation." A design method for determining design variables of an automotive wheel-bearing unit of double-row angular-contact ball bearing type is proposed by using a genetic algorithm. The desired performance of the wheel-bearing unit is to maximize system life while satisfying geometrical and operational constraints without enlarging mounting space. The use of gradient-based optimization methods for the design of the unit is restricted because this design problem is characterized by the presence of discrete design variables such as the number of balls and standard ball diameter. Therefore, the design problem of rolling element bearings is a constrained discrete optimization problem. A genetic algorithm using real coding and dynamic mutation rate is used to efficiently find the optimum discrete design values. To effectively deal with the design constraints, a ranking method is suggested for constructing a fitness function in the genetic algorithm. A computer program is developed and applied to the design of a real wheel-bearing unit model to evaluate the proposed design method. Optimum design results demonstrate the effectiveness of the design method suggested in this study by showing that the system life of an optimally designed wheel-bearing unit is enhanced in comparison with that of the current design without any constraint violations.