﻿ 基于遗传算法的AT换挡元件方案优选
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Selection of shifting element design based on genetic algorithm
Ma Mingyue, Liu Yanfang, Xu Xiangyang, Wang Yi
School of Transportation Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Abstract:Based on the kinematic analysis of planetary gear mechanism and shifting element, an intelligent algorithm applied for selection of the shifting element design of automatic transmission was presented. Unlike traditional design methods, the characteristic parameters of the planetary gear mechanism were optimized based on genetic algorithm. According to the condition of the shifting logical, the offset value of the design was defined, and the fitness function of the shifting element design optimal algorithm was constructed. This method took the ratio sequence and shifting logical into account at the same time to shorten the design cycle. Based on MATLAB, selection of the shifting element design of ZF-8AT was realized and 3 optimal shifting element designs were obtained. The results demonstrate that the selection algorithm proposed is effectively able to realize shifting element design.
Key words: automatic transmission     shifting element     design selection     optimization theory     genetic algorithm

1 AT换挡元件方案的数学模型

 图 1 编码后ZF-8AT的结构简图[10]Fig. 1 Coded diagram of ZF-8AT[10]

AT换挡元件根据布置位置的不同,可以分为制动器和离合器,制动器的基本功能是制动行星齿轮机构中的独立旋转构件,离合器的基本功能是连接或分离行星齿轮机构中的两个独立旋转构件.AT换挡元件方案是指实现行星齿轮机构以不同传动比来传递转矩和转速所需制动器与离合器的组合.为构建换挡元件方案数学模型,对制动器和离合器进行编码,编码规则如下:①制动器的编码由字母B和与制动器相连的构件编码组合而成,记为BX,其中X为构件编码;②离合器的编码由字母C和与离合器相连的两构件编码组合而成,记为CXY,其中X和Y均为构件编码.对图 1所示的ZF-8AT的制动器PA和PB及离合器PC,PD,PE进行编码,其换挡元件方案的矩阵表示为

 方案序号 换挡元件方案矩阵 1 [B3 B4 B5 C13 C14 C15] 2 [B3 B4 B5 C13 C14 C16] 3 [B3 B4 B5 C13 C14 C17] 4 [B3 B4 B5 C13 C14 C23] 1140 [B3 B4 B5 C56 C57 C67]
2 换挡元件方案的运动学分析

3 换挡元件方案的优选

 图 2 平均适应度与最大适应度曲线Fig. 2 Average fitness and optimal fitness

 图 3 优选算法流程图Fig. 3 Data flow of optimization algorithm
4 方案优选案例

 图 4 适应度最小值曲线Fig. 4 Minimal fitness

 方案序号 方案矩阵 fm 39 [B3 B4 C18 C27 C67] 0.006 40 [B3 B4 C18 C27 C68] 0.006 41 [B3 B4 C18 C27 C78] 0.006
 图 5 最优方案的结构简图及换挡逻辑矩阵Fig. 5 Optimal design diagrams and clutching sequences

5 结 论

1) 建立了易于计算机识别的行星齿轮变速机构及换挡元件的数学模型,并基于MATLAB运算平台提出了较高效率的AT传动比求解算法,实现了对换挡元件方案的预筛选;

2) 基于传动比序列和换挡元件闭合有序化的设计要求,采用实际传动比序列与目标传动比序列的相对误差与误差偏移值之和作为遗传算法的换挡元件方案的适应度函数；

3) 以遗传算法和梯度法相结合的方式寻找到AT换挡元件的最优方案,并计算出相应的最优行星排特性参数、传动比序列及其对应的换挡逻辑；对ZF-8AT自动变速器的换挡元件方案进行了优选,最终得到包括原方案在内的3组最优方案，验证了本文所提出的优选算法的可行性和准确性.

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#### 文章信息

Ma Mingyue, Liu Yanfang, Xu Xiangyang, Wang Yi

Selection of shifting element design based on genetic algorithm

JOURNAL OF BEIJING UNIVERSITY OF AERONAUTICS AND A, 2014, 40(10): 1372-1377.
http://dx.doi.org/10.13700/j.bh.1001-5965.2013.0619