乘員約束系統(tǒng)參數(shù)篩選與正交試驗(yàn)優(yōu)化設(shè)計(jì)

田晟

(華南理工大學(xué) 土木與交通學(xué)院，廣東 廣州 510640)

乘員約束系統(tǒng)參數(shù)篩選與正交試驗(yàn)優(yōu)化設(shè)計(jì)

田晟

(華南理工大學(xué) 土木與交通學(xué)院，廣東 廣州 510640)

摘要：為了在汽車碰撞測(cè)試中獲得較高的分值，需要對(duì)乘員約束系統(tǒng)進(jìn)行參數(shù)篩選與優(yōu)化設(shè)計(jì)。初步挑選出對(duì)乘員約束系統(tǒng)影響較大的7個(gè)參數(shù)，然后由WIC加權(quán)法則、一階響應(yīng)面法結(jié)合7因素2水平的正交試驗(yàn)設(shè)計(jì)篩選出4個(gè)優(yōu)化設(shè)計(jì)參數(shù)即排氣孔面積A、限力值L、安全帶延伸率B和預(yù)緊力N。再采用4因素5水平的正交試驗(yàn)優(yōu)化這4個(gè)設(shè)計(jì)參數(shù)，因正交試驗(yàn)不是全面試驗(yàn)，對(duì)試驗(yàn)結(jié)果采取直接觀察找出的組合不能完全保證就是最優(yōu)組合，所以需要進(jìn)行極差分析和方差分析。由極差分析法和方差分析法綜合權(quán)衡后選擇最優(yōu)組合A5L1B1N5，比較了優(yōu)化前后的假人x向胸部減速度等圖形曲線，結(jié)果表明：WIC和HIC等主要傷害指標(biāo)值得到下降，同時(shí)胸部x向減速度峰值與設(shè)計(jì)計(jì)算的峰值接近；優(yōu)化后的乘員約束系統(tǒng)性能得到了明顯的改善。

關(guān)鍵詞：正面碰撞；乘員約束系統(tǒng)；正交試驗(yàn)設(shè)計(jì)；參數(shù)篩選；優(yōu)化設(shè)計(jì)

網(wǎng)絡(luò)出版地址：http://www.cnki.net/kcms/detail/23.1390.U.20151105.0910.002.html

乘員約束系統(tǒng)是指在汽車碰撞事故中對(duì)乘員起保護(hù)作用的裝置，包括安全帶、安全氣囊、安全座椅、吸能式轉(zhuǎn)向管柱與轉(zhuǎn)向盤、軟化的內(nèi)飾件等[1-2]，乘員保護(hù)系統(tǒng)中最早采用安全帶，在車輛發(fā)生前撞及翻滾時(shí)約束乘員相對(duì)于車輛的運(yùn)動(dòng)，對(duì)保護(hù)乘員能起到顯著的效果[3]。安全氣囊也常常用來(lái)保護(hù)車內(nèi)的乘員，它與安全帶的聯(lián)合使用可對(duì)乘員進(jìn)行有效的保護(hù)[4-5]。為了保護(hù)乘員艙的乘員,需要避免乘員與艙內(nèi)部件發(fā)生二次碰撞，良好的乘員約束系統(tǒng)通過(guò)優(yōu)化設(shè)計(jì)后能夠與假人和車體合理匹配[6-9]。例如YANG Yang等研究了人車較好地匹配耦合后具有較低的碰撞傷害[10]，YANCHAR等調(diào)查了加拿大某地區(qū)居民對(duì)兒童乘員約束系統(tǒng)安全知識(shí)的掌握和實(shí)際運(yùn)用的差異并給出了建議[11]，吳俊通過(guò)兒童乘員約束系統(tǒng)模型得到影響6至12歲兒童乘員損傷的顯著性參數(shù)，并提出該年齡段兒童的約束系統(tǒng)最佳設(shè)計(jì)[12]。李勇等研究證實(shí)乘員約束系統(tǒng)的參數(shù)都存在一個(gè)合理的數(shù)值或范圍，能顯著減輕對(duì)乘員的傷害[13]。由此可見(jiàn)乘員約束系統(tǒng)參數(shù)的選擇和優(yōu)化設(shè)計(jì)是汽車正面碰撞安全設(shè)計(jì)的關(guān)鍵問(wèn)題之一，本研究采用正交試驗(yàn)設(shè)計(jì)對(duì)乘員約束系統(tǒng)進(jìn)行參數(shù)篩選和優(yōu)化設(shè)計(jì)。

1乘員約束系統(tǒng)參數(shù)的選擇

乘員約束系統(tǒng)包括安全帶、安全氣囊、座椅等部件，而每一部件又包含不同的特征參數(shù)。根據(jù)工程經(jīng)驗(yàn)，選擇表1中7個(gè)設(shè)計(jì)變量作為乘員約束系統(tǒng)的基本參數(shù)，表1中還列出7個(gè)設(shè)計(jì)參數(shù)的變化范圍。

表1　設(shè)計(jì)參數(shù)變化范圍Table 1　Variation range of design parameters

1990年通用公司的Viano和Arepally[14]引入加權(quán)因子，將各項(xiàng)傷害指標(biāo)用加權(quán)的方法綜合到一起，來(lái)評(píng)價(jià)人體傷害程度，即采用加權(quán)傷害準(zhǔn)則WIC (weighted injury criterion)來(lái)全面評(píng)價(jià)乘員約束系統(tǒng)的性能，WIC值越低，說(shuō)明約束系統(tǒng)的保護(hù)性能越好；反之，則越差。WIC計(jì)算式為

(1)

式中：HIC(head injury criterion)為頭部綜合性能指標(biāo)，C3ms為胸部3 ms加速度值，Ccomp為胸部壓縮量，F(xiàn)FL為左大腿最大軸向壓力，F(xiàn)FR為右大腿最大軸向壓力。式中每項(xiàng)指標(biāo)前的權(quán)系數(shù)表明了該種傷害類型的重要程度，而重要程度則來(lái)自于對(duì)大量事故的統(tǒng)計(jì)分析和仿真模擬，例如蘭鳳崇等[15]建立生物力學(xué)有限元仿真模型評(píng)價(jià)人體胸-腹部損傷程度。

根據(jù)7個(gè)設(shè)計(jì)參數(shù)對(duì)WIC值的影響程度以及工程經(jīng)驗(yàn)，選擇排氣孔面積A、限力值L、安全帶延伸率B、預(yù)緊力N作為優(yōu)化設(shè)計(jì)的參數(shù)。

2乘員約束系統(tǒng)優(yōu)化設(shè)計(jì)

選出4個(gè)參數(shù)(即4因素)作為乘員約束系統(tǒng)優(yōu)化設(shè)計(jì)變量后，考慮在初始值上下對(duì)稱變化4次即得到5個(gè)水平數(shù)如表2所示，這是一個(gè)4因素5水平的正交試驗(yàn)設(shè)計(jì)，選取正交表L25(56)。

表2　4因素5水平表Table 2　Four factors and five levels

表3　乘員約束系統(tǒng)傷害指標(biāo)輸出結(jié)果Table 3　Injury indexes output results of occupant restraint system

2.1　極差分析

(a)排氣孔面積A

(b)限力值L

(c)安全帶延伸率B

(d)預(yù)緊力值N 圖1　各因素與WIC的關(guān)系Fig.1　Relationship between WIC and optimization parameters

(a)排氣孔面積A

(b)限力值L

(c)安全帶延伸率B

(d)預(yù)緊力值N圖2　各因素與胸部x向減速度峰值omax的關(guān)系Fig.2　Relationship between omaxand optimization parameters

由表4得出，按照Rj從大到小排列，4個(gè)因素對(duì)WIC的影響程度從大到小的排列順序?yàn)榕艢饪酌娣eA、預(yù)緊力N、限力值L、安全帶延伸率B。由表4和圖1得出各因素的水平最優(yōu)組合為A5L1B1N5。

表4以WIC為目標(biāo)的極差分析表
Table 4Range analysis for WIC

ALBNK10.53790.49800.49850.5061K20.52080.49960.50000.5034K30.50090.50270.50250.5016K40.48260.50270.50260.4989K50.46500.50420.50370.4972Rj0.07290.00620.00520.0089

表5　以omax為目標(biāo)的極差分析表Table 5　Range analysis for omax

WIC是直接反映乘員約束系統(tǒng)的性能指標(biāo)，前面提到WIC越小表明乘員約束系統(tǒng)性能越好。圖1顯示出隨著A和N的增大，WIC的趨勢(shì)反而減小；圖1同時(shí)顯示出隨著L和B的增大，WIC的值也隨著增大；即圖1總體反映了WIC隨著各個(gè)因素變化的趨勢(shì)，然而A、L、B和N這4個(gè)因素變化程度對(duì)WIC的影響還需要進(jìn)一步分析。

2.2　方差分析

通過(guò)表6和表7，可以得出如下分析結(jié)果：

表6　WIC方差分析表Table 6　Variance analysis for WIC

表7　胸部x向減速度峰值方差分析表Table 7　Variance analysis for omax

1)從表6得出各因素對(duì)WIC(反映乘員約束系統(tǒng)性能)的影響，按從大到小的順序排列：排氣孔面積A、預(yù)緊力N、限力值L、安全帶延伸率B，即調(diào)整A的大小對(duì)WIC影響最大，也與極差分析的結(jié)果一致，同時(shí)也看到這4個(gè)因素都與WIC顯著相關(guān)或高度顯著相關(guān)，說(shuō)明選擇這4個(gè)因素作為乘員約束系統(tǒng)優(yōu)化設(shè)計(jì)參數(shù)是合適的。

綜上所述，優(yōu)化的候選方案包括A5L2B1N5、A5L1B1N5、A4L4B2N5，其中A5L2B1N5和A4L4B2N5即是表3中22號(hào)方案和19號(hào)方案(表3中黑體顯示)，而A5L1B1N5組合沒(méi)有出現(xiàn)在表3中，需要重新在MADYMO(mathematical dynamic model)模型里仿真計(jì)算，結(jié)果如表8所示，且與優(yōu)化前的方案(0號(hào)方案)、19號(hào)和22號(hào)方案進(jìn)行比較。

表8　方案比選Table 8　Choosing scheme

由MADYMO 后處理分別輸出優(yōu)化前后的左右大腿軸向受力曲線，胸部x向減速度曲線、胸部合成加速度曲線,頭部合成加速度和胸部壓縮量曲線，如圖3~5所示。

(a)左大腿

(b)右大腿圖3　左右大腿軸向受力優(yōu)化前后對(duì)比Fig.3　Force comparison of left and right femurs before and after optimization

(a)胸部x向減速度

(b)胸部合成加速度圖4　胸部x向減速度和合成加速度優(yōu)化前后對(duì)比Fig.4　Chest deceleration(x) and resultant acceleration comparison before and after optimization

(b)胸部壓縮量圖5　頭部合成加速度和胸部壓縮量?jī)?yōu)化前后對(duì)比Fig.5　Head resultant acceleration and chest compression comparison before and after optimization

3結(jié)論

1)在乘員約束系統(tǒng)參數(shù)篩選中，通過(guò)WIC加權(quán)法則和正交試驗(yàn)設(shè)計(jì)，綜合考慮之后選出排氣孔面積A、限力值L、安全帶延伸率B和預(yù)緊力N作為4個(gè)優(yōu)化設(shè)計(jì)參數(shù)；

2)采用4因素5水平的正交試驗(yàn)優(yōu)化設(shè)計(jì)該4個(gè)參數(shù)，選擇比較接近-42.2g的胸部x向減速度峰值，由極差分析法和方差分析法綜合權(quán)衡后選擇最優(yōu)組合為A5L1B1N5；

3)利用MADYMO后處理軟件輸出優(yōu)化前后的假人x向胸部減速度等6個(gè)圖形曲線；

4)優(yōu)化結(jié)果表明：正面碰撞乘員傷害WIC值降低了8.67%，約束系統(tǒng)性能得到了優(yōu)化改善，同時(shí)優(yōu)化后的假人x向胸部減速度峰值等于-42.28g，最接近設(shè)計(jì)計(jì)算峰值-42.2g。

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Parameter selection and orthogonal experimental

optimization design for an occupant restraint system

TIAN Sheng

(School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, China)

Abstract：In order to obtain better scores in car crash tests, an occupant restraint system needs parameter selection and optimization design. Here, seven initial parameters which have greater influence on an occupant restraint system are chosen. Then four optimization design parameters, namely vent area A, load limit L, seat belt extension ratio B, and pretension force N, are selected by the weighted injury criteria (WIC) rule, the first-order response surface method, and the orthogonal test design of seven factors and two levels. The four parameters are optimized using an orthogonal test design of four factors and five levels. Because the orthogonal test is partly done, direct observation of the test results shows the combination cannot fully guarantee an optimal combination, it needs to do range analysis and variance analysis. The optimal combination A5L1B1N5is chosen comprehensively by range analysis and variance analysis. Comparing some graphics curves, including dummy chest deceleration(x), before and after optimization, shows that the main harm index values such as WIC and HIC decrease. At the same time, the dummy chest deceleration(x) peak value approaches the peak value of the design calculation. The optimized performance of the occupant restraint system is obviously improved.

Keywords：full frontal impact; occupant restraint system; orthogonal experimental design; parameters selection; optimization design

通信作者：田晟，E-mail:shitian1@scut.edu.cn.

作者簡(jiǎn)介：田晟(1969-), 男, 副教授,博士.

基金項(xiàng)目：國(guó)家科技支撐計(jì)劃資助項(xiàng)目(2011BAG02B02).

收稿日期：2014-10-20.網(wǎng)絡(luò)出版日期：2015-11-05.

中圖分類號(hào)：U461.91

文獻(xiàn)標(biāo)志碼：A

文章編號(hào)：1006-7043(2015)12-1565-06

doi:10.11990/jheu.201410035