Abstract-There is an ever increasing demand for intelligent and efficient urban vehicle systems that fulfill several requirements, e.g., low cost maintainability and high passenger comfort. Concerning these goals reliable methods are needed to model and to evaluate the imposed performances. In this paper a spectral analysis of the suspension system of a commercial city bus is presented. Based on experimental data taken on a city bus, the vibrations emerging on the wheels and the body are analyzed in the frequency domain. The goal of the analysis is to characterize the main eigenfrequencies of the suspension system and its damping in amplitude and also to evaluate both the road and the suspension system in terms of passenger comfort according to ISO standards.

The financial reports of the automotive companies' are measured in a standardized manner; therefore, they are transparent and comparable to each other, but this is not valid for the sustainability reports and it is not possible to compare their sustainability performances. Standard-setting organizations are currently searching for better reporting procedures. This study aims to investigate the connection between sustainability and financial reports for the most dominant European car manufacturers. It reviews the traceability of the sustainability elements back to the financial statements, which helps transparency, comparability, and impact measurement of the disclosed items and issues. This investigation allowed us to additionally review whether these companies are targeting to disclose the most harmful pollution impacts, or only focus to disclose the required obligatory items. Given the financial and sustainability reports magnitude manual testing would not provide complete and proper coverage, therefore we utilized an automated and AI-assisted content analysis with natural language processing. In this new review method, the sustainable elements of the textual reports were automatically retrieved following the 5-stage model of Landrum & Ohsowski (2018). The study highlights the lack of true sustainability information content of reports and the potential discrepancies and connections between the financial and the sustainability reports. Findings concluded that sustainability disclosures at the reviewed companies from several aspects could be improved and quantified, traced back to the financial disclosures, and to be comparable to each other if they apply a similar review method. Graphic abstract

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Abstract-Concerning the increasing demand for intelligent and efficient urban vehicle systems with low cost maintainability and high passenger comfort, reliable methods are needed to model and to evaluate the imposed performances. The measurements, vibrations emerging on the wheels and the body, that has ben taken on a city bus are analyzed in the frequency domain. In this paper a parametric spectral analysis (AR/ARMA method) of the suspension system of a commercial city bus is presented. The goal of the analysis is to find the right structure for the systems. Parametric methods used in this paper justify and extend the results obtained by non-parametric ones and provide more accurate results for vibration analysis. One of the main conclusions of the investigations is that the quartercar model structure based on first principles does not reflect the true frequency domain behavior of the system. Thus the identification of the physical model must be complemented with a suitable uncertainty modeling and classification.

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Abstract-Using only vertical acceleration measurements for the sprung and unsprung masses of a suspension system of a commercial city bus, the goal of the paper is to develop an analysis method to find the vibration modes of the mechanical system from data measured during real life operation. The identified vibration modes can be used to (in)validate first principle physical models of the system, while the identified ARMA models can be used to develop uncertainty models. The challenge in the problem is that the measurements are subject to very high level of noise due to maneuvering of the vehicle, nonlinear effects of the suspension system, vibration of the engine and the gear system, and sensor noise. Nonparametric and parametric modeling methods are applied to evaluate the quality of the measurements and find the invariant properties of the suspension system. It is shown based on multiple experiments that independently of the actual road properties and operating conditions, eigen-frequencies of some vibration modes can be determined with relatively small uncertainty, while the corresponding damping factors have varying amount of uncertainty. Comparing the results with the modes of a full car vehicle model developed based on physical considerations, it can be concluded that an identification algorithm for obtaining the parameters of the physical model must be complemented with a suitable uncertainty modeling and classification.

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