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DC link filter capacitors used in electric drives for automotive applications are most of the time aluminum electrolytic capacitors. However their high sensitivity to temperature results in very we...

Aluminum electrolytic capacitors are the most cost effective solution for DC-link decoupling design in comparison to other technologies such as tantalum ones. However they are also the weakest part of static power converters. Thus, a lot of studies have been made in order to estimate their aging particularly through the Equivalent Series Resistance value (ESR) i.e. the real part of the impedance. Nowadays, aluminum electrolytic capacitor manufacturers have successfully created more sustainable high temperature components especially for automotive applications. In this context, most of electrical models found in the literature are not accurate over a broad frequency range. Furthermore, some studies show that the ESR is not always representative of the capacitor lifetime. As a consequence, an improved impedance model with the add of a diffusive element is proposed in this paper. Its purpose is to bring an efficient tool to quantify the evolution during the aging of each impedance part and not only the global real part for automotive dedicated DC-link capacitors.

The aim of this paper is to present the design process and the use of an ageing test bench for electrolytic capacitors dedicated to automotive applications. For this purpose, a small electric vehicle (Renault Twizy) powertrain has been taken as an example in order to choose adapted capacitors, to evaluate their stress in a “real world” application and to determine the best solution for an accelerated ageing study. Thus, specific static converters used in a controlled oven have been designed. On the basis of these tests (and capacitors' impedance analysis), an accurate model of these components has been developed and the ageing process is to be continued after more 7000 hours already done.

Electrolytic aluminum capacitors used in electric drive for automotive are deemed to be the weakest components of static power converters. A lot of studies have been made to estimate their aging but only for a nominal point. This paper presents a specific operation cycle implementation to study the impact of a variable and more realistic thermal cycling. Moreover, an improvement of the classical electrical model for an electrolytic capacitor is proposed by adding a diffusion-relative element called “anomalous diffusion”. Experimental results show the interest of this element for an impedance-fitting. Finally, thermal measurements validate thermal cycling simulations.

International audience; Research in stereoscopic 3D coding, transmission and subjective assessment methodology depends largely on the availability of source content that can be used in cross-lab evaluations. While several studies have already been presented using proprietary content, comparisons between the studies are difficult since discrepant contents are used. Therefore in this paper, a freely available dataset of high quality Full-HD stereoscopic sequences shot with a semiprofessional 3D camera is introduced in detail. The content was designed to be suited for usage in a wide variety of applications, including high quality studies. A set of depth maps was calculated from the stereoscopic pair. As an application example, a subjective assessment has been performed using coding and spatial degradations. The Absolute Category Rating with Hidden Reference method was used. The observers were instructed to vote on video quality only. Results of this experiment are also freely available and will be presented in this paper as a first step towards objective video quality measurement for 3DTV.

International audience; Crosstalk is one of the main display-related perceptual factors degrading image quality and causing visual discomfort on 3D-displays. It causes visual artifacts such as ghosting effects, blurring, and lack of color fidelity which are considerably annoying and can lead to difficulties to fuse stereoscopic images. On stereoscopic LCD with shutter-glasses, crosstalk is mainly due to dynamic temporal aspects: imprecise target luminance (highly dependent on the combination of left-view and right-view pixel color values in disparity regions) and synchronization issues between shutter-glasses and LCD. These different factors influence largely the reproducibility of crosstalk measurements across laboratories and need to be evaluated in several different locations involving similar and differing conditions. In this paper we propose a fast and reproducible measurement procedure for crosstalk based on high-frequency temporal measurements of both display and shutter responses. It permits to fully characterize crosstalk for any right/left color combination and at any spatial position on the screen. Such a reliable objective crosstalk measurement method at several spatial positions is considered a mandatory prerequisite for evaluating the perceptual influence of crosstalk in further subjective studies.

International audience; In this paper, a subjective study is presented which aims to measure the minimum perceivable depth difference on an autostereoscopic display in order to provide an indication for visual fatigue. The developed experimental setup was used to compare the subject's performance before and after 3D excitation on an autostereoscopic display. By comparing the results to a verification session with 2D excitation, the effect of 3D visual fatigue can be isolated. It was seen that it is possible to reach the threshold of acuity for stereo disparity on that autostereoscopic display. It was also found that the measured depth acuity is slightly higher after 3D viewing than after 2D viewing.

International audience; Broadcasting of high definition (HD) stereobased 3D (S3D) TV are planned, or has already begun, in Europe, the US, and Japan. Specific data processing operations such as compression and temporal and spatial resampling are commonly used tools for saving network bandwidth when IPTV is the distribution form, as this results in more efficient recording and transmission of 3DTV signals, however at the same time it inevitably brings quality degradations to the processed video. This paper investigated observers quality judgments of state of the art video coding schemes (simulcast H.264/AVC or H.264/MVC), with or without added temporal and spatial resolution reduction of S3D videos, by subjective experiments using the Absolute Category Rating method (ACR) method. The results showed that a certain spatial resolution reduction working together with high quality video compressing was the most bandwidth efficient way of processing video data when the required video quality is to be judged as "good" quality. As the subjective experiment was performed in two different laboratories in two different countries in parallel, a detailed analysis of the interlab differences was performed.

International audience; The transmission of 3DTV sequences over packet based networks may result in degradations of the video quality due to packet loss. In the conventional 2D case, several different strategies are known for extrapolating the missing information and thus concealing the error. In 3D however, the residual error after concealment of one view might leads to binocular rivalry with the correctly received second view. In this paper, three simple alternatives are presented: frame freezing, a reduced playback speed, and displaying only a single view for both eyes, thus effectively switching to 2D presentation. In a subjective experiment the performance in terms of quality of experience of the three methods is evaluated for different packet loss scenarios. Error-free encoded videos at different bit rates have been included as anchor conditions. The subjective experiment method contains special precautions for measuring the Quality of Experience (QoE) for 3D content and also contains an indicator for visual discomfort. The results indicate that switching to 2D is currently the best choice but difficulties with visual discomfort should be expected even for this method.

International audience; Autostereoscopic displays simplify the presentation of 3D content because they do not require any glasses and they allow the perception of motion parallax. While the perception of depth is certainly an added value, the technical rendering process of the current display technology also introduces artifacts. For the viewer, the tradeoff may be expressed in terms of quality of experience. However, quality of experience assessment related to 3D is still an open issue. Towards this goal, several original subjective test methods are proposed and compared that are meant for assessing the quality of experience. A split-screen setup simultaneously displays a 2D and a 3D presentation. The observers vote according to their preference in terms of quality of experience. In four experiments, the influence of the depth rendering process is evaluated. The results indicate that the degradation by the depth rendering process may easily dominate the added value of depth in a content specific manner.