| 1. |
- Anguelova, Milena, 1978, et al.
(författare)
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An Efficient Method for Structural Identiability Analysis of Large Dynamic Systems
- 2012
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Ingår i: 16th IFAC Symposium on System Identification. - 1474-6670. - 9783902823069 ; 16:1, s. 941-946
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Konferensbidrag (refereegranskat)abstract
- Ordinary differential equation models often contain a large number of parameters that must be determined from measurements by parameter estimation. For a parameter estimation procedure to be successful, there must be a unique set of parameters that can have produced the measured data. This is not the case if a model is not structurally identifiable with the given set of outputs selected as measurements. We describe the implementation of a recent probabilistic semi-numerical method for testing local structural identifiability based on computing the rank of a numerically instantiated Jacobian matrix (observability/identifiability matrix). To obtain this, matrix parameters and initial conditions are specialized to random integer numbers, inputs are specialized to truncated random integer coefficient power series, and the corresponding output of the state space system is computed in terms of a truncated power series, which then is utilized to calculate the elements of a Jacobian matrix. To reduce the memory requirements and increase the speed of the computations all operations are done modulo a large prime number. The method has been extended to handle parametrized initial conditions and is demonstrated to be capable of handling systems in the order of a hundred state variables and equally many parameters on a standard desktop computer.
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| 2. |
- Hjalmarsson, Håkan, 1963, et al.
(författare)
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A Mathematica Toolbox for Signals, Systems and Identification System Identification
- 2012
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902823069 ; 16:1, s. 1541-1546
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Konferensbidrag (refereegranskat)abstract
- In this contribution we provide a status report for the Mathematica toolbox that is described in Sjöberg 2008. The toolbox covers a comprehensive set of functions for handling deterministic and stochastic signals and models. On top of this the toolbox provides signal processing and system identification methods ranging from non-parametric to parametric, and from linear models to a wide class of non-linear models. Algorithms are tailored to be able to efficiently handle large scale data sets and models as well as symbolic computations. This allows theory to be handled alongside practice, implying that the toolbox provides an environment suitable both for education and data processing. In regards to system identification, one of the novel features is graphical support for building block-based nonlinear models. Another novel feature is that modeling errors can be propagated through applications.
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| 3. |
- Lindsten, Fredrik, et al.
(författare)
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A non-degenerate rao-blackwellised particle filter for estimating static parameters in dynamical models
- 2012
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902823069 ; 16:1, s. 1149-1154
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Konferensbidrag (refereegranskat)abstract
- The particle filter (PF) has emerged as a powerful tool for solving nonlinear and/or non-Gaussian filtering problems. When some of the states enter the model linearly, this can be exploited by using particles only for the "nonlinear" states and employing conditional Kalman filters for the "linear" states; this leads to the Rao-Blackwellised particle filter (RBPF). However, it is well known that the PF fails when the state of the model contains some static parameter. This is true also for the RBPF, even if the static states are marginalised analytically by a Kalman filter. The reason is that the posterior density of the static states is computed conditioned on the nonlinear particle trajectories, which are bound to degenerate over time. To circumvent this problem, we propose a method for targeting the posterior parameter density, conditioned on just the current nonlinear state. This results in an RBPF-like method, capable of recursive identification of nonlinear dynamical models with affine parameter dependencies.
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| 4. |
- Marconato, A., et al.
(författare)
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Identification of the Silverbox Benchmark Using Nonlinear State-Space Models
- 2012
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902823069 ; 16:1, s. 632-637
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Konferensbidrag (refereegranskat)abstract
- This work presents the application of an initialization scheme for nonlinear state-space models on a real data benchmark example: the Silverbox problem. The goal of the proposed approach is to transform the identification of a nonlinear dynamic system into an approximate static problem, so that system dynamics and nonlinear terms are identified separately. Classic identification techniques are used to handle dynamics, while regression methods from the statistical learning community are introduced to estimate the nonlinearities in the model. Results obtained on the Silverbox problem are discussed and compared with the performance of other related methods.
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| 5. |
- McKelvey, Tomas, 1966, et al.
(författare)
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Non-parametric frequency response estimation using a local rational model
- 2012
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. - 9783902823069 ; 16:1, s. 49-54
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Konferensbidrag (refereegranskat)abstract
- A review of the relationship between the frequency response function of linear system and the DFT of the input and output signals show that the output DFT is a sum of two terms. The first term contain the FRF multiplied with the input DFT and the second term capture the effect when the system is not operating in a periodic fashion. The utilization of these two terms when performing non-parametric frequency response function estimation has led to the previously developed Local Polynomial Method. This paper acknowledge that the two terms can better be approximated by local rational functions with a common denominator polynomial and a new method called Local Rational Method has been developed. Numerical simulations illustrate the performance of the new rational method in comparison with the polynomial one. The results suggest that the new rational method gives better performance when the system has a resonant behavior.
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| 6. |
- Hang, Chang C., et al.
(författare)
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Practical Aspects of PID Auto-Tuners Based on Relay Feedback
- 1988
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Ingår i: 2nd International IFAC Symposium on Adaptive Control of Chemical Processes 1988 (ADCHEM '88), Lyngby, Copenhagen, Denmark, 17-19 August. - 1474-6670. ; 21:7, s. 153-158
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Konferensbidrag (refereegranskat)
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| 7. |
- Johansson, Rolf
(författare)
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Lyapunov Design for Adaptive Control of Robots
- 1989
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 1474-6670. ; 22:3
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents algorithms for continuous-time direct adaptive control of robot manipulators. Lyapunov theory is used for controller design and stability investigation. Algorithms for rapid continuous-time adaptive control are presented.
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| 8. |
- Källström, Claes, et al.
(författare)
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Adaptive Autopilots for Large Tankers
- 1978
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Ingår i: 7th Triennial World Congress of the IFAC : A Link Between Science and Applications of Automatic Control, Helsinki, Finland, 12-16 June - A Link Between Science and Applications of Automatic Control, Helsinki, Finland, 12-16 June. - 1474-6670. ; 11:1, s. 477-484
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Konferensbidrag (refereegranskat)abstract
- The adaptive autopilots are based on velocity scheduling, a self-tuning regulator for steady state course keeping, a high gain turning regulator with variable structure, and a Kalman filter. Results from simulations and full-scale experiments on three different tankers are presented. The autopilots are shown to work excellently under different loads, speed and weather conditions.
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| 9. |
- Olsson, Gustaf, et al.
(författare)
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Estimation and Control of Biological Activity in the Activated Sludge Process Using Dissolved Oxygen Measurements
- 1977
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Ingår i: IFAC Symposium on Environmental Systems Planning, Design and Control, Kyoto, Japan, 1-5 August. - 1474-6670. ; 10:7, s. 745-755
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Konferensbidrag (refereegranskat)abstract
- The control of an activated sludge process is considered. It is discussed how the organism activity is a crucial information for the control. It is shown, how the concentration profile of dissolved oxygen (DO) in the biological reactor is related to the sludge activity. As a result the DO profile is a useful measurement information for control purposes
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| 10. |
- Åström, Karl Johan, et al.
(författare)
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Analysis of a Scheme for Iterated Identification and Control
- 1994
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Ingår i: IFAC Symposium on System Identification (SYSID'94), Copenhagen, Denmark, 4-6 July. - 1474-6670. ; 27:8, s. 473-478
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Konferensbidrag (refereegranskat)abstract
- This paper presents analysis of a scheme for iterated identification and control design. The approach is based on least squares identification in closed loop and pole placement design. It has previously been shown that the criteria for control and identification are the same provided that the data filters are chosen properly. The iterated scheme may be viewed as a recursion in model parameters. Each step consists of system identification and control design. Interesting questions are then: What are the fix points? Are the fix points stable? These questions are investigated for some simple examples. Relations to other problems like model reduction and adaptive control are also discussed.
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