A Refined Iv Method for Closed-Loop System Identification

A ship's roll dynamics is very sensitive to changes in the loading conditions and a worst-case scenario is the loss of stability. This paper proposes an approach for online estimation of a ship's mass and center of mass. Instead of focusing on a sensor-rich environment where all possible signals on a ship can be measured and a complete model of the ship can be estimated, a minimal approach is adopted. A model of the roll dynamics is derived from a well-established model in literature and it is assumed that only motion measurements from an inertial measurement unit together with measurements of the rudder angle are available. Furthermore, identifiability properties and disturbance characteristics of the model are presented. Due to the properties of the model, the parameters are estimated with an iterative instrumental variable approach to mitigate the influence of the disturbances and it uses multiple datasets simultaneously to overcome identifiability issues. Finally, a simulation study is presented to investigate the sensitivity to the initial conditions and it is shown that there is a low sensitivity for the desired parameters.

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“…An iterative method based on Gilson et al (2006) is used in this paper. Here, z i indicates that z belongs to the dataset i.…”

Section: The Iterative Instrumental Variable Methodsmentioning

confidence: 99%

Modeling for IMU-based Online Estimation of a Ship's Mass and Center of Mass

et al. 2015

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“…In order to obtain an unbiased estimate in the closed loop environment, the instrumental variable (IV) methods [5]- [7] have been proposed, which require a few iterations to obtain unbiased estimate. These methods are based on the indirect approach of the closed loop identification or at least the instrumental variables are produced based on the reference input signal.…”

Section: Introductionmentioning

confidence: 99%

Bias Compensation of Recursive Least Squares Estimate in Closed Loop Environment

Ikeda

Mogami

Shimomura

2008

SICE Journal of Control, Measurement, and System Integration

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In this paper, an asymptotic bias of the recursive least squares (RLS) estimate in the closed loop environment is analyzed and its compensation method is proposed under the assumption that the noise is white. Namely, a bias compensated RLS method in the closed loop environment based on output error (OE) model is proposed. A posteriori error is also analyzed for the estimation of the noise variance.

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“…See, for instance, Söderström and Stoica (1989) or Ljung (1999) for more details on the instrumental variable method. The method presented in this section is based on the method of Gilson et al (2006) where the parameters are estimated in an iterative scheme. In each iteration, the instruments are created by simulating the inputs and the outputs from the rudder angle by using the latest parameter estimates and the iterations are terminated when the parameters have converged.…”

Section: The Instrumental Variable Estimatormentioning

confidence: 99%

Online Estimation of Ship's Mass and Center of Mass Using Inertial Measurements

Linder¹,

Enqvist²,

Fossen³

et al. 2015

IFAC-PapersOnLine

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A ship's roll dynamics is sensitive to the mass and mass distribution. Changes in these physical properties might introduce unpredictable behavior of the ship and a worst-case scenario is that the ship will capsize. In this paper, a recently proposed approach for online estimation of mass and center of mass is validated using experimental data. The experiments were performed using a scale model of a ship in a wave basin. The data was collected in free run experiments where the rudder angle was recorded and the ship's motion was measured using an inertial measurement unit. The motion measurements are used in conjunction with a model of the roll dynamics to estimate the desired properties. The estimator uses the rudder angle measurements together with an instrumental variable method to mitigate the influence of disturbances. The experimental study shows that the properties can be estimated with quite good accuracy but that variance and robustness properties can be improved further.

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A Refined Iv Method for Closed-Loop System Identification

Cited by 18 publications

References 20 publications

Modeling for IMU-based Online Estimation of a Ship's Mass and Center of Mass

Modeling for IMU-based Online Estimation of a Ship's Mass and Center of Mass

Bias Compensation of Recursive Least Squares Estimate in Closed Loop Environment

Online Estimation of Ship's Mass and Center of Mass Using Inertial Measurements

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