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Models and Critical Maneuvers for Road Vehicles

機(jī)譯：道路車輛的模型和關(guān)鍵演習(xí)

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摘要

As manufacturers are pushing their research and development toward more simulation based and computer aided methods, vehicle dynamics modeling and simulation become more important than ever. The challenge lies in how to utilize the new technology to its fullest, delivering the best possible performance given certain objectives and current restrictions. Here, optimization methods in different forms can be a tremendous asset. However, the solution to an optimization problem will always rely on the problem formulation, where model validity plays a crucial role. The main emphasis in this thesis lies within methodology and analysis of optimal control oriented topics for safety-critical road-vehicle maneuvers. A crucial element here is the vehicle models. This is investigated as a first study, evaluating the degree to which different model configurations can represent the lateral vehicle dynamics in critical maneuvers, where it is shown that even the low-complexity models describe the most essential vehicle characteristics surprisingly well. How to formulate the optimization problems and utilize optimal control tools is not obvious. Therefore, a methodology for road-vehicle maneuvering in safety-critical driving scenarios is presented, and used in evaluation studies of various vehicle model configurations and different road-surface conditions. It was found that the overall dynamics is described similarly for both the high- and low-complexity models, as well as for various road-surface conditions. If more information about the surroundings is available, the best control actions might differ from the ones in traditional safety systems. This is also studied, where the fundamental control strategies of classic electronic stability control is compared to the optimal strategy in a safety-critical scenario. It is concluded that the optimal braking strategy not only differs from the traditional strategies, but actually counteracts the fundamental intentions from which the traditional systems are based on. In contrast to passenger cars, heavy trucks experience other characteristics due to the different geometric proportions. Rollover is one example, which has to be considered in critical maneuvering. Model configurations predicting this phenomenon are investigated using optimal control methods. The results show that the simple first go-to models have to be constrained very conservatively to prevent rollover in more rapid maneuvers. In vehicle systems designed for path following, which has become a trending topic with the expanding area of automated driving, the requirements on vehicle modeling can be very high. These requirements ultimately depend on several various properties, where the path restrictions and path characteristics are very influential factors. The interplay between these path properties and the required model characteristics is here investigated. In situations where a smooth path is obtained, low-complexity models can suffice if path deviation tolerances are set accordingly. In more rapid and tricky maneuvers, however, vehicle properties such as yaw inertia are found to be important. Several of the included studies indicate that vehicle models of lower complexity can describe the overall dynamics sufficiently in critical driving scenarios, which is a valuable observation for future development.
機(jī)譯：隨著制造商將研究和開發(fā)推向更多基于仿真和計(jì)算機(jī)輔助的方法，車輛動力學(xué)建模和仿真比以往任何時候都變得越來越重要。挑戰(zhàn)在于如何充分利用新技術(shù)，在特定目標(biāo)和當(dāng)前限制下，如何提供最佳性能。在這里，不同形式的優(yōu)化方法可能是一筆巨大的財(cái)富。但是，對優(yōu)化問題的解決方案始終取決于問題的表述，而模型的有效性起著至關(guān)重要的作用。本論文的主要重點(diǎn)在于針對安全關(guān)鍵型道路車輛操縱的面向最優(yōu)控制的方法論和分析。這里的關(guān)鍵因素是車輛模型。這是一項(xiàng)首次研究，其目的是評估不同模型配置在臨界操作中代表橫向車輛動力學(xué)的程度，這表明即使是低復(fù)雜度的模型也能很好地描述最基本的車輛特性。如何制定優(yōu)化問題并利用優(yōu)化控制工具還不是很清楚。因此，提出了一種在關(guān)鍵安全駕駛場景下進(jìn)行機(jī)動車輛操縱的方法，并將其用于各種車輛模型配置和不同路面狀況的評估研究中。結(jié)果發(fā)現(xiàn)，對于高復(fù)雜度模型和低復(fù)雜度模型以及各種路面狀況，總體動力學(xué)情況都是類似的。如果可以獲得有關(guān)周圍環(huán)境的更多信息，則最佳控制措施可能與傳統(tǒng)安全系統(tǒng)中的控制措施有所不同。還將對此進(jìn)行研究，將經(jīng)典電子穩(wěn)定性控制的基本控制策略與安全關(guān)鍵場景中的最佳策略進(jìn)行比較。結(jié)論是，最佳制動策略不僅不同于傳統(tǒng)制動策略，而且實(shí)際上抵消了傳統(tǒng)制動系統(tǒng)所基于的基本意圖。與乘用車相比，重型卡車由于幾何比例不同而具有其他特征。翻轉(zhuǎn)是一個示例，在關(guān)鍵操作中必須考慮這一點(diǎn)。使用最佳控制方法研究了預(yù)測此現(xiàn)象的模型配置。結(jié)果表明，必須非常保守地限制簡單的首次進(jìn)入模型，以防止在更快速的操作中發(fā)生側(cè)翻。在設(shè)計(jì)用于路徑跟蹤的車輛系統(tǒng)中，隨著自動駕駛領(lǐng)域的發(fā)展，該系統(tǒng)已成為一個趨勢主題，對車輛建模的要求可能很高。這些要求最終取決于多種特性，其中路徑限制和路徑特性是非常有影響力的因素。這些路徑屬性和所需的模型特征之間的相互作用在這里進(jìn)行了研究。在獲得平滑路徑的情況下，如果相應(yīng)地設(shè)置路徑偏差公差，則低復(fù)雜度模型就足夠了。然而，在更快速和棘手的操縱中，發(fā)現(xiàn)諸如偏航慣性的車輛特性很重要。其中包括的幾項(xiàng)研究表明，復(fù)雜性較低的車輛模型可以在關(guān)鍵駕駛場景中充分描述整體動力學(xué)，這對于未來的發(fā)展具有重要意義。

著錄項(xiàng)

  • 作者

    Lundahl, Kristoffer;

  • 作者單位
  • 年度 2016
  • 總頁數(shù)
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類

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