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An Online tilt Estimation and Compensation algorithm for a Small Satellite Camera

INTERNATIONAL JOURNAL OF AERONAUTICAL AND SPACE SCIENCES 2018年第1期19卷 172-182页

作者： Lee, Da-Hyun Hwang, Jai-hyuk Def Agcy Technol & Qual Precedent Study Planning Team IT Venture Town Complex 5F35Techno 9 Ro Daejeon 52851 South Korea Korea Aerosp Univ Dept Aerosp & Mech Engn 76 Hanggongdaehak Ro Goyang Si 10540 Gyeonggi Do South Korea

In the case of a satellite camera designed to execute an Earth observation mission, even after a pre-launch precision alignment process has been carried out, misalignment will occur due to external factors during the launch and in the operating environment. In particular, for high-resolution satellite cameras, which require submicron accuracy for alignment between optical components, misalignment is a major cause of image quality degradation. To compensate for this, most high-resolution satellite cameras undergo a precise realignment process called refocusing before and during the operation process. However, conventional Earth observation satellites only execute refocusing upon de-space. Thus, in this paper, an online tilt estimation and compensation algorithm that can be utilized after de-space correction is executed. Although the sensitivity of the optical performance degradation due to the misalignment is highest in de-space, the MTF can be additionally increased by correcting tilt after refocusing. The algorithm proposed in this research can be used to estimate the amount of tilt that occurs by taking star images, and it can also be used to carry out automatic tilt corrections by employing a compensation mechanism that gives angular motion to the secondary mirror. Crucially, this algorithm is developed using an online processing system so that it can operate without communication with the ground.

关键词： tilt algorithm Online algorithm Small satellite camera Refocusing

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On enhanced tilt strategies for tilting trains

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10th International Conference on Computer System Design and Operation in the Railway and Other Transit Systems

作者： Kufver, B. Persson, R. Ferroplan Sweden Bombardier Sweden

ISBN: (纸本)1845641779

Many railways have taken tilting trains into operation on lines with horizontal curves with small radii. tilting trains have vehicle bodies that can roll inwards, thus reducing the lateral acceleration perceived by the passengers. Hence, tilting trains can run through curves at an enhanced speed. However, too much tilt can cause motion sickness among sensitive passengers. The tilt motions, generated by computer-controlled actuators should be optimised with care, taking the local track geometry and actual train speed into account. This paper presents tilt algorithms aimed at balancing conflicting objectives. Furthermore, the paper discusses the usefulness of route files (track geometry data) onboard the train and possible positioning systems.

关键词： tilting train tilt algorithm tilt strategy alignment cant passenger comfort motion sickness

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Strategies for less motion sickness on tilting trains

Strategies for less motion sickness on tilting trains

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12th International Conference on Computer System Design and Operation in the Railway and other Transit Systems

作者： Persson, R. Kufver, B. KTH Stockholm Sweden Ferroplan Linkoping Sweden

ISBN: (纸本)9781845644680

Many railways have put tilting trains into operation on lines with horizontal curves with small radii. tilting trains have vehicle bodies that can roll inwards, reducing the lateral acceleration perceived by the passengers. tilting trains can therefore run through curves at higher speeds. However, excessive tilt motions can cause motion sickness in sensitive passengers. On the other hand, too little tilting will cause discomfort from high lateral acceleration and jerk. The present paper presents new tilt algorithms aimed at balancing the conflicting objectives of ride comfort and less motion sickness. An enhanced approach is taken, where the amount of tilt depends on the local track conditions and the train speed. The paper shows how selected tilt algorithms influence certain motion sickness related carbody motions. Speed profiles designed to avoid local peaks in the risk of motion sickness are another possibility. The speed profiles for both tilting and non-tilting trains are today set from safety and comfort perspectives only, thus minimizing the running time. The present paper shows how speed profiles could be used to balance the conflicting objectives of running time and less risk of motion sickness. The result is derived from simulations and put in relation to today's tilt algorithms and speed profiles on the Stockholm-Gothenburg main line in Sweden (457 km).

关键词： tilting train tilt algorithm tilt strategy passenger comfort motion sickness running time simulation

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