| 1. |
- Ardeshiri, Tohid, et al.
(författare)
-
Variational Iterations for Smoothing with Unknown Process and Measurement Noise Covariances
- 2015
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this technical report, some derivations for the smoother proposed in [1] are presented. More specifically, the derivations for the cyclic iteration needed to solve the variational Bayes smoother for linear state-space models with unknownprocess and measurement noise covariances in [1] are presented. Further, the variational iterations are compared with iterations of the Expectation Maximization (EM) algorithm for smoothing linear state-space models with unknown noise covariances.[1] T. Ardeshiri, E. Özkan, U. Orguner, and F. Gustafsson, ApproximateBayesian smoothing with unknown process and measurement noise covariances, submitted to Signal Processing Letters, 2015.
|
|
| 2. |
- Carvalho Bittencourt, André, 1984-
(författare)
-
Data-driven estimation of Gramian based interaction measures for control structure selection
- 2016
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Interaction measures quantify the input-output relations in MIMO processes and can support the selection of control structures (CSS). Interaction measures are typically computed based on an existing process models. The study of input-output interactions based on data can complement missing information on a model, e.g., revealing unknown relations in a complex system or adjusting for a time dependent behavior. This paper presents a unified approach for data-driven estimation of Gramian based interaction measures from input-output data. Given open or closed-loop data, a high-order Vector ARX (VARX) model is identified and its parameters are used to calculate predictor Markov parameters, together with a covariance estimate. Three interaction measures based on the Hankel, Hilbert-Schmidt-Hankel and H2 norms are calculated from the estimated predictor Markov parameters and uncertainty estimates are provided for the last two, allowing for robust CSS. A solution which is recursive in the data points is presented, making it practical for applications to large datasets. The approach is verified through simulations and several possible extensions are discussed. As the method is suitable for open and closed-loop data and for large datasets, it opens up for data-driven control structure selection based on operational data from entire plants.
|
|
| 3. |
- Cerqueira, Jorge, et al.
(författare)
-
Introducing CDIO at The Military Institue of Engineering in Brazil
- 2016
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report describes the motivation, the current state and the future actions of an improvement process in engineering education at the Brazilian higher education institution called the Military Institute of Engineering. Based on the reasons for why and how to change, the CDIO framework was chosen, at the end of 2014, as the kernel of this improvement process. The activities realized, the plan for the future actions and the open questions are presented in this report.
|
|
| 4. |
|
|
| 5. |
- Helmersson, Anders, 1957-
(författare)
-
Generalized Riccati Equations for Hinfinity Synthesis
- 2015
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Conditions for the existence of controllers for lineartime-varying (LTV) systems is given. The closed loop performance isspecified in terms of energy gain, which also includes terminalconstraints. The conditions can be formulated either as linear matrixinequalities (LMIs) or as solutions to Riccati differental equationswith algebraic constraints.
|
|
| 6. |
- Karami, Farzaneh, et al.
(författare)
-
Automated Model Generation for Analysis of Large-scale Interconnected Uncertain Systems
- 2015
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The first challenge in robustness analysis of large-scale interconnected uncertain systems is to provide a model of such systems in a standard-form that is required within different analysis frameworks. This becomes particularly important for large-scale systems, as analysis tools that can handle such systems heavily rely on the special structure within such model descriptions. We here propose an automated framework for providing such models of large-scale interconnected uncertain systems that are used in Integral Quadratic Constraint (IQC) analysis. Specifically, in this paper we put forth a methodological way to provide such models from a block-diagram and nested description of interconnected uncertain systems. We describe the details of this automated framework using an example.
|
|
| 7. |
- Linder, Jonas, 1984-, et al.
(författare)
-
Identification and prediction in dynamic networks with unobservable nodes
- 2016
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The interest for system identification in dynamic networks has increased recently with a wide variety of applications. In many cases, it is intractable or undesirable to observe all nodes in a network and thus, to estimate the complete dynamics. If the complete dynamics is not desired, it might even be challenging to estimate a subset of the network if key nodes are unobservable due to correlation between the nodes. In this contribution, we will discuss an approach to treat this problem. The approach relies on additional measurements that are dependent on the unobservable nodes and thus indirectly contain information about them. These measurements are used to form an alternative indirect model that is only dependent on observed nodes. The purpose of estimating this indirect model can be either to recover information about modules in the original network or to make accurate predictions of variables in the network. Examples are provided for both recovery of the original modules and prediction of nodes.
|
|
| 8. |
- Linder, Jonas, 1984-, et al.
(författare)
-
Modeling for IMU-based Online Estimation of a Ship's Mass and Center of Mass
- 2015
-
Ingår i: Proceedings of the 10th Conference on Manoeuvring and Control of Marine Craft. - Linköping : Elsevier BV.
-
Konferensbidrag (refereegranskat)abstract
- 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 the sensitivity is low for the desired parameters.
|
|
| 9. |
- Linder, Jonas, et al.
(författare)
-
On Indirect Input Measurements
- 2015
-
Ingår i: Proceedings of the 17th IFAC Symposium on System Identification. - : Elsevier BV. ; , s. 104-109
-
Konferensbidrag (refereegranskat)abstract
- A common issue with many system identification problems is that the true input to the system is unknown. In this paper, a framework, based on indirect input measurements, is proposed to solve the problem when the input is partially or fully unknown, and cannot be measured directly. The approach relies on measurements that indirectly contain information about the unknown input. The resulting indirect model formulation, with both direct and indirect input measurements as inputs, can be used to estimate the desired model of the original system. Due to the similarities with closed-loop system identification, an iterative instrumental variable method is proposed to estimate the indirect model. To show the applicability of the proposed method, it is applied to data from an inverted pendulum experiment with good results.
|
|
| 10. |
- Linder, Jonas, 1984-, et al.
(författare)
-
Online Estimation of Ship's Mass and Center of Mass Using Inertial Measurements
- 2015
-
Ingår i: Proceedings of the 10th Conference on Manoeuvring and Control of Marine Craft. - Linköping : Elsevier BV.
-
Konferensbidrag (refereegranskat)abstract
- 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 were 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.
|
|
