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A fixed-lag smoother for solving joint input and state estimation problems in structural dynamics
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).ORCID iD: 0000-0001-9862-1144
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis we have investigated different numerical filters for joint input and state estimation, with the aim of designing a robust algorithm capable of monitoring the continuous motion and loading in a truck chassis. The algorithm has to be able to use sparse measurements of the motion on different parts of the truck as it is excited by road induced vibrations, and transform this data into knowledge of the state in the entire system. To do this, the algorithm has to be supplied with information about the dynamic properties of the current system.

In Paper A we have developed and implemented a fixed-lag smoother for joint input and state estimation in linear time-invariant dynamic structures. A fixed-lag smoother maximizes the use of information available in the measurements by allowing a small time lag in the estimation. As input, external forces as well as support motions can be computed. Furthermore, both measurement noise and model errors are accounted for and simulated as stochastic processes. The filter is firstly verified with straightforward numerical simulations of a simply supported beam, followed by a more involved simulation of a truck fuel tank. It is shown that the fixed-lag smoother performs very well, it estimates both input and states with a high accuracy even though the signals are contaminated with noise and the model contains errors.

In Paper B the fixed-lag smoother is applied on real measurements. We investigate the capabilities of the proposed filter by analysing acceleration measurements from a truck side skirt excited by road induced vibrations. In this study, we focus on estimating the state in the side skirt body from a minimum number of measurement sensors. The dynamic properties of the side skirt are obtained experimentally from an operational modal analysis. It is shown that the fixed-lag smoother estimates the state very well. The results also shows that the smoothing effect is larger when fewer measurement sensors are used.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , 12 p.
Series
TRITA-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 602
Keyword [en]
Joint input-state estimation, Fixed-lag smoother, Structural dynamics
National Category
Other Mechanical Engineering
Research subject
Solid Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-193054ISBN: 978-91-7729-141-1OAI: oai:DiVA.org:kth-193054DiVA: diva2:974832
Presentation
2016-10-28, Seminarierummet Hållfasthetslära, Teknikringen 8D, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20160928

Available from: 2016-09-28 Created: 2016-09-27 Last updated: 2016-10-28Bibliographically approved
List of papers
1. A fixed-lag smoother for solving input force and support motion identification problems in structural dynamics
Open this publication in new window or tab >>A fixed-lag smoother for solving input force and support motion identification problems in structural dynamics
2016 (English)Manuscript (preprint) (Other academic)
Abstract [en]

In this work, the problem of joint input and state estimation based on measured response in a dynamic system is addressed.A fixed-lag smoother for support motion or input force estimation in linear structural dynamics is proposed. The unknown inputs are estimated in conjunction with the states in an augmented state description of the system. A fixed-lag smoother maximizes the use of information available in the measurements by allowing a small time lag in the estimation, leading to a recursive non-causal filter. This type of filter has not previously been implemented in the field of structural dynamics. The filter is capable of handling any combination of measured displacement, velocity and acceleration; furthermore are both measurement noise and model errors accounted for and simulated as stochastic processes. In this study, estimations are based on sparse noisy measurements of system displacement and model errors are simulated through the use of deliberately incorrect model descriptions. The proposed algorithm is verified by numerical simulations and the qualities of the estimations are compared to those of the augmented Kalman filter.It is shown that with this filter, significant improvements of the input estimations are achieved, especially of inputs located far away from measurement sensors. The improvement consists of noise reduction, phase correction and by a more accurate division of the individual contribution of multiple inputs.

26 p.
Keyword
Joint input-state estimation, Fixed-lag smoother, Force identification, Structural dynamics
National Category
Other Mechanical Engineering
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:kth:diva-193052 (URN)
Note

QC 20160928

Available from: 2016-09-27 Created: 2016-09-27 Last updated: 2016-09-28Bibliographically approved
2. Dynamic response identification based on state estimation and operational modal analysis applied to a truck side skirt
Open this publication in new window or tab >>Dynamic response identification based on state estimation and operational modal analysis applied to a truck side skirt
2016 (English)Manuscript (preprint) (Other academic)
Abstract [en]

This work presents an experimental verification of a fixed-lag smoother for solving joint state and input estimation problems.Sparse acceleration measurements from a truck side skirt excited by road induced vibrations from the Scania vibration test track are analysed. The system model is obtained experimentally from an operational modal analysis, reducing the modelling errors and avoiding the need of a numerical model. The work is focused on estimating the motion of the side skirt in positions where no measurements are available. The estimated motions are compared to those of a joint input-state estimation algorithm and to the actual measured motion. Two sensor configurations are studied: one where the number of measurement sensors is high compared to the number of estimated motions and participating modes, and another where the number of sensors are reduced. With the first configuration, both algorithms perform very well. With the reduced numbers of sensors, the fixed-lag smoother excels the joint input-state estimator in capturing the individual motion of each position on the side skirt.

22 p.
Keyword
Joint input-state estimation, Fixed-lag smoother, Experimental verification, Structural dynamics
National Category
Other Mechanical Engineering
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:kth:diva-193053 (URN)
Note

QC 20160928

Available from: 2016-09-27 Created: 2016-09-27 Last updated: 2016-09-28Bibliographically approved

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Lagerblad, Ulrika
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