Analysis and optimization of vehicle design by using a mathematical model

Matematik modelleme yardımıyla taşıt tasarımının analizi ve optimizasyonu

Abstract

A new designed vehicle has to have a character which is describing itself. Factors forming the character of the car are its properties. Necessary modification has to be applied in the early design phases to achieve desired properties. But any re-design causes a feedback study in the design phase. The earlier these modifications are applied the shorten is the design phase and the lower are the costs invested for design. One of the most important method to reduce design and development time is to being able to analyze and optimize vehicle properties and being able to recognize the effects of the change of design parameters on properties even in early design phases. The optimization of vehicle properties such as comfort, economic, safety and performance form the most significant stage of the vehicle design. Nowadays, vehicles are expected to provide a lot of properties at the same time. But unfortunately, improving some properties is mostly resulted that other properties are affected in a negative way by this change. Parameters which form the properties of the vehicle can be changed in definite limits to keep some other properties in desired values. This kind of studies on this subject is forming an optimization problem. The common result which will be reached at the end of these researches is having a lot of alternative solutions due to the complex effects of vehicle properties with each other. Furthermore, if we examine vehicle properties, it is clear that there will be various solutions for each special goal. In other words it is clear that there can not be a unique reasonable solution for a vehicle design. Priority properties and rank of important of characteristics are being evaluated. These evaluations will be fruitful for us to determine which properties are much more essential in this stage. It is clear that, the more property the system has, the better solutions it will have. However, the properties which are increased by the wishes will raise the probability of having contradictory results with each other in the same proportion. These interactions form the contradictions which are often noticed between the properties. The target of this study is to give some information about providing restrictions or improvements of varieties permitted in some properties and parameters by examining the items which are identified above. Moreover, serving solution approaches for vehicle mathematical modeling in order to assist designers in decision by various probabilities. A model in which variable number is more than correlation number has been examined by utilizing optimization techniques due to its structure. Simplex method, which is widespread and effective among lots of techniques is used in the study. A software (ACANO) is formed in order to use the model much more easily and effectively. This software can be used by designers and styling experts by the help of being user friendly and inter-actively. The basic property and other properties altogether guide designers about what kind of interaction can be in vehicle parameters because of the variety which is occurred in vehicle properties or parameters by its structure. ACANO consists of “Additional Analyze” modules; Use-Value-, Weak Spot analysis and Property Detail Analysis (to apply detailed analyses of a property), defining some vehicle parameters in numerical (especially driving parameters) and to compare a new designed vehicle with the properties of a different vehicle in the same segment. By the application example of the software ACANO, a concept vehicle called FUNNY, which is a city car, is introduced. Target function is chosen as “Fuel Economy”, properties and design parameters are analyzed and determined in order to optimize target function in defined ranges. In two step analysis fuel economy and other characteristics are improved by using “Property Detail Analysis”. Also vehicle parameters, especially driving parameters are defined numerical. Later weak points of the concept vehicle is determined using “Use-Value” and “Weak Spot “analysis. At least FUNNY is compared with a different vehicle in the same segment and advantages and disadvantages according to the compared vehicle is determined. It is clear that solution approaches in which the model has been explained that is formed with correlations according to vehicle properties an parameters will be beneficial for people who decide since they will direct and guide people’s intuitions. However, any mathematical method or technique can not take its place of the people who decide, yet it will assist them.

Özet

Yeni taşıtın tasarlanmasında önemli olan aşama ana taşıt parametrelerinin belirlenmesidir. Bu parametreler taşıt özelliklerinin (emniyet, performans, seyir özellikleri…) ortaya çıkmasında etkili olmaktadır. Tasarımın başlangıç fazından itibaren amaç konstrüktiv taşıt parametrelerinin taşıt özelliklerine etkilerini tanımak ya da en azından tahmin edebilmektir. Bir taşıttan birçok özelliği sağlaması istenmektedir. Ancak kaçınılmaz olarak birbirleriyle çelişen hedefler ortaya çıkmaktadır. Belirli özelliklerin iyileştirilmesi genellikle diğer bazı özelliklerden ödün vermeyi gerektirmektedir. Ne kadar çok istek sıralanırsa, çelişkiye düşme olasılığı da o kadar artmaktadır. Taşıt özelliklerinin istekler listesine uygun olarak tasarımın erken aşamalarında optimize edilmesi arzulanan bir durumdur. Böylece tasarım süresi kısalacak ve maliyetler azalacaktır. Çalışmada bu amaçla tasarımın erken aşamalarında taşıt parametrelerinde meydana gelecek değişiklikler sonucu taşıt özeliklerinin analiz ve optimizasyonu için bir matematik model oluşturulmuştur. Değişken sayısı bağıntı sayısından büyük olan model, yapısı gereği optimizasyon tekniklerinden yararlanılarak irdelenmiştir. Oluşturulan modelin kolay ve verimli bir şekilde kullanılabilmesi amacıyla bir program (ACANO) yazılmıştır. Programın yapısı gereği taşıt özellikleri veya parametrelerinde meydana gelecek değişim sonucu hedef özellik ve diğer özellikle birlikte taşıt parametrelerinde ne yönde bir etkileşim olabileceği konusunda tasarımcıya yol göstermektedir. Programın sahip olduğu ek analizler yardımıyla tasarlanacak taşıt aynı sınıf içersinde yer alan farklı bir taşıt ile karşılaştırılabilecek, fayda değer ve zayıf nokta analizi ile konsept taşıtın zaafları tespit edilebilecek, özellik ayrıntı analizi ile her bir özelliğin ayrıntılı olarak analiz edilebilecek ve bazı taşıt parametreleri (özellikle seyir parametreleri) sayısal olarak ifade edilebilecektir.