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  • 51.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Investigating stability of Laplacians on signed digraphs via eventual positivity2019Inngår i: 2019 IEEE 58th Conference on Decision and Control (CDC), IEEE, 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Signed Laplacian matrices generally fail to be diagonally dominant and may fail to be stable. For both undirected and directed graphs, in this paper we present conditions guaranteeing the stability of signed Laplacians based on the property of eventual positivity, a Perron-Frobenius type of property for signed matrices. Our conditions are necessary and sufficient for undirected graphs, but only sufficient for digraphs, the gap between necessity and sufficiency being filled by matrices who have this Perron-Frobenius property on the right but not on the left side (i.e., on the transpose). An exception is given by weight balanced signed digraphs, where eventual positivity corresponds to positive semidefinitness of the symmetric part of the Laplacian. Analogous conditions are obtained for signed stochastic matrices.

    Fulltekst (pdf)
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  • 52.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Involutive flows and discretization errors for nonlinear driftless control systems2017Inngår i: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 110, s. 29-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a continuous-time nonlinear driftless control system, an involutive flow is a composition of input profiles that does not excite any Lie bracket. Such flow composition is trivial, as it corresponds to a "forth and back" cyclic motion obtained rewinding the system along the same path. The aim of this paper is to show that, on the contrary, when a (nonexact) discretization of the nonlinear driftless control system is steered along the same trivial input path, it produces a net motion, which is related to the gap between the discretization used and the exact discretization given by a Taylor expansion. These violations of involutivity can be used to provide an estimate of the local truncation error of numerical integration schemes. In the special case in which the state of the driftless control system admits a splitting into shape and phase variables, our result corresponds to saying that the geometric phases of the discretization need not obey an area rule, i.e., even zero-area cycles in shape space can lead to nontrivial geometric phases. (C) 2017 Elsevier B.V. All rights reserved.

    Fulltekst (pdf)
    fulltext
  • 53.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Minimal eventually positive realizations of externally positive systems2016Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 68, s. 140-147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is a well-known fact that externally positive linear systems may fail to have a minimal positive realization. In order to investigate these cases, we introduce the notion of minimal eventually positive realization, for which the state update matrix becomes positive after a certain power. Eventually positive realizations capture the idea that in the impulse response of an externally positive system the state of a minimal realization may fail to be positive, but only transiently. As a consequence, we show that in discrete-time it is possible to use downsampling to obtain minimal positive realizations matching decimated sequences of Markov coefficients of the impulse response. In continuous-time, instead, if the sampling time is chosen sufficiently long, a minimal eventually positive realization leads always to a sampled realization which is minimal and positive.

    Fulltekst (pdf)
    fulltext
  • 54.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Nonintegrable discrete-time driftless control systems: geometric phases beyond the area rule2016Inngår i: 2016 IEEE 55th Conference on Decision and Control (CDC), IEEE Press, 2016, s. 4692-4697Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In a continuous-time nonlinear driftless control system, a geometric phase is a consequence of nonintegrability of the vector fields, and it describes how cyclic trajectories in shape space induce non-periodic motion in phase space, according to an area rule. The aim of this paper is to shown that geometric phases exist also for discrete-time driftless nonlinear control systems, but that unlike their continuous-time counterpart, they need not obey any area rule, i.e., even zero-area cycles in shape space can lead to nontrivial geometric phases. When the discrete-time system is obtained through Euler discretization of a continuous-time system, it is shown that the zero-area geometric phase corresponds to the gap between the Euler discretization and an exact discretization of the continuous-time system.

    Fulltekst (pdf)
    Nonintegrable discrete-time driftless control systems: geometric phases beyond the area rule
  • 55.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Representing externally positive systems through minimal eventually positive realizations2015Inngår i: Proceedings of the IEEE 54th Annual Conference on Decision and Control (CDC),, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 6385-6390Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to investigate the cases in which an externally positive discrete-time system fails to have a minimal positive realization, in this paper we introduce the notion of minimal eventually positive realization, fr which the state update matrix becomes positive after a certain power. This property captures the idea that in the impulse response of an externally positive system the state of a minimal realization may fail to be positive, but only transiently. It is shown in the paper that whenever a minimal eventually positive realization exists, then the sequence of Markov parameters of the impulse response admits decimated subsequences for which minimal positive realizations exist and can be obtained by downsampling the eventually positive realization.

    Fulltekst (pdf)
    fulltext
  • 56.
    Altafini, Claudio
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Ceragioli, Francesca
    Politecn Torino, Italy.
    Signed bounded confidence models for opinion dynamics2018Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 93, s. 114-125Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this paper is to modify continuous-time bounded confidence opinion dynamics models so that "changes of opinion" (intended as changes of the sign of the initial states) are never induced during the evolution. Such sign invariance can be achieved by letting opinions of different sign localized near the origin interact negatively, or neglect each other, or even repel each other. In all cases, it is possible to obtain sign-preserving bounded confidence models with state-dependent connectivity and with a clustering behavior similar to that of a standard bounded confidence model. (C) 2018 Elsevier Ltd. All rights reserved.

    Fulltekst (pdf)
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  • 57.
    Alvenkrona, Miranda
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Hylander, Tilda
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Semi-Automatic ImageAnnotation Tool2023Independent thesis Advanced level (degree of Master (Two Years)), 28 hpOppgave
    Abstract [en]

    Annotation is essential in machine learning. Building an accurate object detec-tion model requires a large, diverse dataset, which poses challenges due to thetime-consuming nature of manual annotation. This thesis was made in collabora-tion with Project Ngulia, which aims at developing technical solutions to protectand monitor wild animals. A contribution of this work was to integrate an effi-cient semi-automatic image annotation tool within the Ngulia system, with theaim of streamlining the annotation process and improving the employed objectdetection models. Through research into available annotation tools, a custom toolwas deemed the most cost-effective and flexible option. It utilizes object detec-tion model predictions as annotation suggestions, improving the efficiency of theannotation process. The efficiency was evaluated through a user test, with partic-ipants achieving an average reduction of approximately 2 seconds in annotationspeed when utilizing suggestions. This reduction was supported as statisticallysignificant through a one-way ANOVA test.

    Additionally, it was investigated which images should be prioritized for an-notation in order to obtain the the most accurate predictions. Different samplingmethods were investigated and compared. The performance of the obtained mod-els remained relatively consistent, although with the even distribution methodat top. This indicate that the choice of sampling method may not substantiallyimpact the accuracy of the model, as the performance of the methods was rela-tively comparable. Moreover, different methods of selecting training data in there-training process was compared. The difference in performance was consider-ately small, likely due to the limited and balanced data pool. The experimentsdid however indicate that incorporating previously seen data with unseen datacould be beneficial, and that a reduced dataset can be sufficient. However, furtherinvestigation is required to fully understand the extent of these benefits.

    Fulltekst (pdf)
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  • 58.
    Amirijoo, Mehdi
    et al.
    Ericsson AB, Sweden.
    Frenger, Pål
    Ericsson AB, Sweden.
    Gunnarsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Moe, Johan
    Ericsson AB, Sweden.
    Zetterberg, Kristina
    Ericsson AB, Sweden.
    On Self-Optimization of the Random Access Procedure in 3G Long Term Evolution2009Inngår i: Proceedings of the 11th IFIP/IEEE International Symposium on Integrated Network Management, IEEE , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Operationally efficient radio networks typically feature a high degree of self-organization. This means less planning efforts and manual intervention, and a potential for better radio resource utilization when network elements adapts its operation to the observed local conditions. The focus in this paper is selfoptimization of the random access channel (RACH) in the 3G Long Term Evolution (LTE). A comprehensive tutorial about the RACH procedure is provided to span the complexity of the selfoptimization. Moreover, the paper addresses RACH key performance metrics and appropriate modeling of the various steps and components of the procedure. Finally, some coupling between parameters and key performance metrics as well as selfoptimization examples are presented together with a feasibility discussion. The main ambition with this workshop paper is to present and define a relevant set of self-optimization problems, rather than to provide a complete solution.

  • 59.
    Amirijoo, Mehdi
    et al.
    Ericsson AB, Sweden.
    Frenger, Pål
    Ericsson AB, Sweden.
    Gunnarsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Moe, Johan
    Ericsson AB, Sweden.
    Zetterberg, Kristina
    Ericsson AB, Sweden.
    Towards Random Access Channel Self-Tuning in LTE2009Inngår i: Proceedings of the 69th IEEE Vehicular Technology Conference, 2009, s. 1-5Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Future radio access networks are expected to show a high degree of self-organization. This paper addresses self-tuning of the random access channel (RACH) in the 3G Long Term Evolution (LTE). The feasibility of self-tuning is investigated by means of simulation, where the coupling between several parameters and the performance of RACH is provided. The conclusion of the simulations is that RACH self-tuning is indeed possible given that UE assisted measurements are available for the self-tuning mechanism.

  • 60.
    Amirijoo, Mehdi
    et al.
    Linköpings universitet, Institutionen för datavetenskap, RTSLAB - Laboratoriet för realtidssystem. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Jörgen
    Software Engineering Institute, Carnegie Mellon University, Pittsburgh, PA, USA.
    Son, Sang H.
    University of Virginia, USA.
    Quantifying and Suppressing the Measurement Disturbance in Feedback Controlled Real-Time Systems2008Inngår i: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 40, nr 1, s. 44-76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the control of continuous and physical systems, the controlled system is sampled sufficiently fast to capture the dynamics of the system. In general, this property cannot be applied to the control of computer systems as the measured variables are often computed over a data set, e.g., deadline miss ratio. In this paper we quantify the disturbance present in the measured variable as a function of the data set size and the sampling period, and we propose a feedback control structure that suppresses the measurement disturbance. The experiments we have carried out show that a controller using the proposed control structure outperforms a traditional control structure with regard to performance reliability.

  • 61.
    Amirijoo, Mehdi
    et al.
    Linköpings universitet, Institutionen för datavetenskap, RTSLAB - Laboratoriet för realtidssystem. Linköpings universitet, Tekniska högskolan.
    Hansson, Jörgen
    Linköpings universitet, Institutionen för datavetenskap, RTSLAB - Laboratoriet för realtidssystem. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Son, Sang H.
    University of Virginia, VA, USA.
    Enhancing Feedback Control Scheduling Performance by On-line Quantification and Suppression of Measurement Disturbance2005Inngår i: Proceedings of the 11th IEEE Real-Time and Embedded Technology and Applications Symposium, 2005, s. 2-11Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the control of continuous and physical systems, the controlled system is sampled sufficiently fast to capture the system dynamics. In general, this property cannot be applied to the control of computer systems as the measured variables are often computed over a data set, e.g., deadline miss ratio. In this paper we quantize the disturbance present in the measured variable as a function of the sampling period and we propose a measurement disturbance suppressive control structure. The experiments we have carried out show that a controller using the proposed control structure outperforms a traditional control structure with regard to performance reliability and adaptation.

  • 62.
    Amirijoo, Mehdi
    et al.
    Linköpings universitet, Institutionen för datavetenskap, RTSLAB - Laboratoriet för realtidssystem. Linköpings universitet, Tekniska högskolan.
    Hansson, Jörgen
    Linköpings universitet, Institutionen för datavetenskap, RTSLAB - Laboratoriet för realtidssystem. Linköpings universitet, Tekniska högskolan.
    Son, Sang H.
    University of Virginia, USA.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Experimental Evaluation of Linear Time-Invariant Models for Feedback Performance Control in Real-Time Systems2007Inngår i: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 35, nr 3, s. 209-238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In recent years a new class of soft real-time applications operating in unpredictable environments has emerged. Typical for these applications is that neither the resource requirements nor the arrival rates of service requests are known or available a priori. It has been shown that feedback control is very effective to support the specified performance of dynamic systems that are both resource insufficient and exhibit unpredictable workloads. To efficiently use feedback control scheduling it is necessary to have a model that adequately describes the behavior of the system. In this paper we experimentally evaluate the accuracy of four linear time-invariant models used in the design of feedback controllers. We introduce a model (DYN) that captures additional system dynamics, which a previously published model (STA) fails to include. The accuracy of the models are evaluated by validating the models with regard to measured data from the controlled system and through a set of experiments where we evaluate the performance of a set of feedback control schedulers tuned using these models. From our evaluations we conclude that second order models (e.g., DYN) are more accurate than first order models (e.g. STA). Further we show that controllers tuned using second order models perform better than controllers tuned using first order models.

  • 63.
    Amlinger, Hanna
    Linköpings universitet, Institutionen för systemteknik.
    Application of a New Software Tool for the Automated Test of Automotive Electronic Control Unit Software2009Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Testing plays a very important role for assuring the quality of developed software. In a modern vehicle, more and more of the functionality is controlled by software and the complexity of the software always increases. The expectations on automating the testing process are to save time and to reach an even higher quality.

    In this thesis, which was performed at ZF Friedrichshafen AG, a new tool for automated tests is studied. The tool is used for software in the loop simulation based system tests. The user specifies which outputs that shall be observed and which inputs that can be controlled. Based on these prerequisites, test cases are generated.

    It has been studied how to apply the tool, how the test case generation can be influenced, on which systems it successfully could be used and which results that could be reached with the tool. The tool has been evaluated on the hand of two real-life examples; the software of an automatic transmission and of a pressure controller, a module of this software. It was found that there are many interesting possibilities to apply the tool in order to support the present testing process.

    Fulltekst (pdf)
    FULLTEXT01
  • 64.
    Amrr, Syed
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten. Indian Inst Technol Delhi, India; Indian Inst Technol Delhi, India.
    Saidi, Abdelaziz Salah
    King Khalid Univ, Saudi Arabia; Univ Tunis Manar, Tunisia.
    Nabi, M.
    Indian Inst Technol Delhi, India.
    Event-driven fault-tolerant attitude control of spacecraft with finite-time disturbance observer under input saturation2023Inngår i: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 33, nr 5, s. 3227-3246Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the attitude stabilization problem for a bandwidth-constrained spacecraft subjected to model uncertainty, external disturbances, actuator faults, and saturated input. The proposed attitude controller is developed by combining the disturbance observer with an event-trigger technique to provide disturbance attenuation meanwhile respecting the constraint on the wireless control network. The proposed disturbance observer estimates the lumped disturbance within a finite time, and its output is then fed to the composite control law. The presented control scheme relaxes the use of a priori upper bound knowledge of disturbance and resolves the unwinding problem in the quaternion-based attitude representation. The closed-loop stability analysis under the proposed algorithm shows the uniformly ultimately bounded convergence of state trajectories. Moreover, the designed event trigger approach avoids the Zeno behavior. The numerical simulation with comparative analysis illustrates the efficacy of the proposed controller in terms of convergence time, steady-state bound, rate of control update, and energy consumption.

  • 65.
    Andersen, Martin
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Khoshfetrat Pakazad, Sina
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Rantzer, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Distributed Robust Stability Analysis of Interconnected Uncertain Systems2012Inngår i: Proceedings of the 51st IEEE Conference on Decision and Control, 2012, s. 1548-1553Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers robust stability analysis of a large network of interconnected uncertain systems. To avoid analyzing the entire network as a single large, lumped system, we model the network interconnections with integral quadratic constraints. This approach yields a sparse linear matrix inequality which can be decomposed into a set of smaller, coupled linear matrix inequalities. This allows us to solve the analysis problem efficiently and in a distributed manner. We also show that the decomposed problem is equivalent to the original robustness analysis problem, and hence our method does not introduce additional conservativeness.

  • 66.
    Andersen, Martin S.
    et al.
    Technical University of Denmark, Lyngby, Denmark.
    Khoshfetrat Pakazad, Sina
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Hansson, Anders
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Rantzer, Anders
    Lund University, Sweden.
    Robust stability analysis of sparsely interconnected uncertain systems2014Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 59, nr 8, s. 2151-2156Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider robust stability analysis of large-scale sparsely interconnected uncertain systems. By modeling the interconnections among the subsystems with integral quadratic constraints, we show that robust stability analysis of such systems can be performed by solving a set of sparse linear matrix inequalities. We also show that a sparse formulation of the analysis problem is equivalent to the classical formulation of the robustness analysis problem and hence does not introduce any additional conservativeness. The sparse formulation of the analysis problem allows us to apply methods that rely on efficient sparse factorization techniques, and our numerical results illustrate the effectiveness of this approach compared to methods that are based on the standard formulation of the analysis problem.

    Fulltekst (pdf)
    fulltext
  • 67.
    Anderson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    On Optimal Dimension Reduction for Sensor Array Signal Processing1993Inngår i: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 30, nr 2, s. 245-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The computational complexity for direction-of-arrival estimation using sensor arrays increases very rapidly with the number of sensors in the array. One way to lower the amount of computations is to employ some kind of reduction of the data dimension. This is usually accomplished by employing linear transformations for mapping full dimension data into a lower dimensional space. Different approaches for selecting these transformations have been proposed. In this paper, a transformation matrix is derived that makes it possible to theoretically attain the full-dimension Cramér-Rao bound also in the reduced space. A bound on the dimension of the reduced data set is given, above which it is always possible to obtain the same accuracy for the estimates of the source localizations, using the lower-dimension data, as that achievable by using the full dimension data. Furthermore, a method is devised for designing the transformation matrix. Numerical examples, using this design method, are presented, where the achievable performance of the (optimal) Weighted Subspace Fitting method with full dimension data is compared to the performance obtained with reduced dimension data. The problem of estimating parameters of sinusoidal signals from noisy data is also addressed by a direct application of the results derived herein.

  • 68.
    Andersson, Amanda
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Näsholm, Elin
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Fast Real-Time MPC for Fighter Aircraft2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The main topic of this thesis is model predictive control (MPC) of an unstable fighter aircraft. When flying it is important to be able to reach, but not exceed the aircraft limitations and to consider the physical boundaries on the control signals. MPC is a method for controlling a system while considering constraints on states and control signals by formulating it as an optimization problem. The drawback with MPC is the computational time needed and because of that, it is primarily developed for systems with a slowly varying dynamics.

    Two different methods are chosen to speed up the process by making simplifications, approximations and exploiting the structure of the problem. The first method is an explicit method, performing most of the calculations offline. By solving the optimization problem for a number of data sets and thereafter training a neural network, it can be treated as a simpler function solved online. The second method is called fast MPC, in this case the entire optimization is done online. It uses Cholesky decomposition, backward-forward substitution and warm start to decrease the complexity and calculation time of the program.

    Both methods perform reference tracking by solving an underdetermined system by minimizing the weighted norm of the control signals. Integral control is also implemented by using a Kalman filter to observe constant disturbances. An implementation was made in MATLAB for a discrete time linear model and in ARES, a simulation tool used at Saab Aeronautics, with a more accurate nonlinear model.

    The result is a neural network function computed in tenth of a millisecond, a time independent of the size of the prediction horizon. The size of the fast MPC problem is however directly affected by the horizon and the computational time will never be as small, but it can be reduced to a couple of milliseconds at the cost of optimality.

    Fulltekst (pdf)
    fulltext
  • 69.
    Andersson, Anders
    Linköpings universitet, Institutionen för systemteknik.
    Implementation, validation and evaluation of an ESC system during a side impact using an advanced driving simulator2009Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The objective of this thesis is to implement a basic, yet realistic, ESC system into the VTI simulator environment. This system is then validated to assure that it is working properly and provides a realistic behavior.

    The implemented ESC system is used in a study, where the ESC system could be turned on and off, to evaluate the benefits of an ESC system after a side impact. This study shows that an ESC system may aid the driver in such a critical situation when the driver is unaware that a side impact will occur. With the ESC system active no driver lost control while with the system inactive there were five drivers that lost control, but deviations in initial speed give statistical difficulties, thus more tests are needed. In the case where the driver knows that an impact will occur the ESC system showed to stabilize the automobile faster and it is shown that an expected improvement in stabilization time is between 40 to 62 percent. It was also seen during this part of the scenario that 2 percent loss of control occurred with an active ESC system and 45 percent without.

    Fulltekst (pdf)
    FULLTEXT01
  • 70.
    Andersson, David
    et al.
    Linköpings universitet, Institutionen för systemteknik.
    Fjellström, Johan
    Linköpings universitet, Institutionen för systemteknik.
    Vehicle Positioning with Map Matching Using Integration of a Dead Reckoning System and GPS2004Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    To make driving easier and safer, modern vehicles are equipped with driver support systems. Some of these systems, for example navigation or curvature warning systems, need the global position of the vehicle. To determine this position, the Global Positioning System (GPS) or a Dead Reckoning (DR) system can be used. However, these systems have often certain drawbacks. For example, DR systems suffer from error growth with time and GPS signal masking can occur. By integrating the DR position and the GPS position, the complementary characteristics of these two systems can be used advantageously.

    In this thesis, low cost in-vehicle sensors (gyroscope and speedometer) are used to perform DR and the GPS receiver used has a low update frequency. The two systems are integrated with an extended Kalman filter in order to estimate a position. The evaluation of the implemented positioning algorithmshows that the system is able to give an estimated position in the horizontal plane with a relatively high update frequency and with the accuracy of the GPS receiver used. Furthermore, it is shown that the system can handle GPS signal masking for a period of time.

    In order to increase the performance of a positioning system, map matching can be added. The idea with map matching is to compare the estimated trajectory of a vehicle with roads stored in a map data base, and the best match is chosen as the position of the vehicle. In this thesis, a simple off-line map matching algorithm is implemented and added to the positioning system. The evaluation shows that the algorithm is able to distinguish roads with different direction of travel from each other and handle off-road driving.

    Fulltekst (pdf)
    FULLTEXT01
  • 71.
    Andersson, Emma
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Intuitive Mission Handling with Automatic Route Re-planning using Model Predictive Control2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The system for mission handling in the Gripen fighter aircraft, and in its ground supporting system, consists for example of ways to plan mission routes, create mission points and validate performed missions. The system is complex and for example, the number of different mission points used increases due to changing demands and needs. This master thesis presents suggestions for improvements and simplifications for the mission handling system, to make it more intuitive and more friendly to use. As a base for the suggestions, interviews with pilots from Saab, TUJAS and FMV have been conducted, this is to obtain opinions and ideas from those using the system and have deep knowledge about it.

    Another possible assistance and improvement is to provide the possibility of on-line automatic re-planning of the mission route in case of obstacles. MPC (Model Predictive Control) has been used to estimate the obstacle’s flight path,and calculate a new route to the next mission point which does not conflict with the estimated enemy’s path. This system has been implemented in Matlab and the concept is demonstrated with different test scenarios where the design parameters (prediction horizon and penalty in the cost function) for the controller are varied, and stationary and moving obstacles are induced.

    Fulltekst (pdf)
    fulltext
  • 72.
    Andersson Granberg, Tobias
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Jonson, Carl-Oscar
    Linköpings universitet, Institutionen för biomedicinska och kliniska vetenskaper, Avdelningen för kirurgi, ortopedi och onkologi. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Regionledningskontoret, Katastrofmedicinskt centrum.
    Prytz, Erik
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system. Linköpings universitet, Filosofiska fakulteten.
    Steins, Krisjanis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Waldemarsson, Martin
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Sensor Requirements for Logistics Analysis of Emergency Incident Sites2020Inngår i: Proceedings of the 17th ISCRAM Conference / [ed] Amanda Lee Hughes, Fiona McNeill, Christopher Zobe, Information Systems for Crisis Response and Management , 2020, s. 952-960Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Using sensors to collect data at emergency incident sites can facilitate analysis of the logistic operations. This can be used to improve planning and preparedness for new operations. Furthermore, real-time information from the sensors can serve as operational decision support. In this work in progress, we investigate the requirements on the sensors, and on the sensor data, to facilitate such an analysis. Through observations of exercises, the potential of using sensors for data collection is explored, and the requirements are considered. The results show that the potential benefits are significant, especially for tracking patients, and understanding the interaction between the response actors. However, the sensors need to be quite advanced in order to capture the necessary data.

    Fulltekst (pdf)
    fulltext
  • 73.
    Andersson, Henrik
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem.
    Model Based Control of Throttle, EGR and Wastegate: A System Analysis of the Gas Flows in an SI-Engine2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Due to governmental requirements on low exhaust gas emissions and the drivers request of fast response, it is important to be able to control the gas flow in a spark ignited engine accurately. The air into the cylinder is directly related to the torque generated by the engine. The technique with recirculation of exhaust gases (EGR) affect the air flow into the cylinder and increase the complexity of the control problem. In this thesis a mean value model for a spark ignited engine has been created. The basis was a diesel model from Linköping University that has been modified and parameterized with data from a test cell. The model has been used to study the gas exchange system with respect to the dynamic behaviors and nonlinearities that occur when the three actuators (throttle, wastegate and EGR-valve) are changed. Based on this analysis, some different control strategies have been developed and tested on the model. The presented results show that different control strategies give different behaviors and there is a trade-off between fast torque response and high precision for controlling the EGR-ratio. A control strategy is proposed containing two main feedback loops, prefiltering of the reference signal and a feedforward part.

    Fulltekst (pdf)
    fulltext
  • 74.
    Andersson, Håkan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Hilding, Daniel
    DYNAmore Nordic AB, Brigadgatan 5, 587 58 Linköping, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, 587 58 Linköping, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit2017Inngår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Petter Krus, Liselott Ericson and Magnus Sethson, Linköping: Linköping University Electronic Press, 2017, Vol. 144, s. 225-235Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study a previously developed co-simulation method that is based on a 1D system model representing the fluid components of a hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies, is further developed. The fluid system model consists of ordinary differential equation sub-models that are computationally very inexpensive, but still represents the fluid dynamics very well. The co-simulation method has been shown to work very well for a simple model representing a hydraulic driven machinery. A more complex model was set up in this work, in which two cylinders in the hydraulic circuit were evaluated. Such type of models, including both the main piston and control valves, are necessary as they represent the real application to a further extent than the simple model, of only one cylinder. Two models have been developed and evaluated, from the simple rigid body representation of the structural mechanics model, to the more complex model using linear elastic representation. The 3D FE-model facilitates evaluation of displacements, stresses, and strains on a local level of the model. The results can be utilised for fatigue assessment, wear analysis and for predictions of noise radiation.

    Fulltekst (pdf)
    System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit
  • 75.
    Andersson, Johan
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A framework for evaluation of iterative learning control2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    I många industriella tillämpningar används robotar för tunga och repetetiva uppgifter. För dessa tillämpningar är iterative learning control (ILC) ett sätt att fånga upp och utnyttja repeterbarheten för att förbättra någon form av referenseföljning.

    I det här examensarbetet har det tagits fram ett ramverk som ska hjälpa en användare att kunna untyttja ILC. Det visas handgripliga exempel på hur man enkelt kan avända ramverket. Övergången från den betydligt mer vanliga diskreta ILC algoritmen till det kontinuerliga tillvägagångssättet som anänds av ramverket underlättas av teroretisk  underbygga inställningsregler. Den uppnåeliga prestandan demonstreras med hjälp av ramverkets inbyggda plotfunktioner.

    Fulltekst (pdf)
    fulltext
  • 76.
    Andersson, Karl
    Linköpings universitet, Institutionen för systemteknik.
    Modellering av kontrollenhet för JAS39 Gripens hjälpkraftsystem2007Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Simulation is an important tool for verification and validation. Time and money can be saved using simulation instead of flight tests. Achieving satisfying results demands precise models. A new model for JAS39 Gripen’s auxiliary power and engine starting system, APESS, is presented. The objective of this thesis is to develop a more accurate model of APESS and its control unit, APECU. The model was created in MATRIXX. Models are created in MATRIXX using a graphical interface. In MATRIXX, it is possible to generate C-code which is a useful feature.

    Models for the APECU, APU, valves and sensors has been created. The models are then tested and verified using data from test flights.

    The result is a more accurate model for SYSIM. The created control unit model can be used in Easy5. Simulation in MATRIXX has become a useful educational tool.

    One model for three purposes will decrease the amount of nesesary work each system or model update brings. Keeping the model description up to date is also easier.

    Fulltekst (pdf)
    FULLTEXT01
  • 77.
    Andersson, Magnus
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Experimental Design and Updating of Finite Element Models1997Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with two partly related topics: model updating and actuator/sensor placement concerning finite element (FE) models of large, flexible mechanical structures.

    The importance of accurate dynamical FE models of mechanical structures in, e.g., aviation/aerospace applications are steadily increasing. For instance, a sufficient accurate model may reduce the expenses for ground vibration testing and wind-tunnel experiments substantially. It is therefore of high industrial interest to obtain accurate models of flexible structures. One approach is to improve a parameterized, initial FE model using measurements of the real structure, so-called model updating. For a fast, successful model updating, three requirements must be fulfilled. The model updating must be computationally cheap, which requires an efficient model reduction technique. The cost function describing the deviation between the model output and the measurements must have good convexity properties so that an estimation of the parameters corresponding to the global optimum is likely to be obtained. Finally, the optimization methods must be reliable. A novel mode-pairing free cost function is presented, and together with a proposed general procedure for model updating, a cheap model updating formulation with good parameter estimation properties is obtained.

    Actuator and sensor placement is a part of the experimental design. It is performed in advance of the vibrational experiment in order to ensure high quality measurements. Using a nominal FE model of the structure, an actuator/sensor placement can be made. Actuator/sensor placement tasks are generally discrete, non-convex optimization problems of high complexity. One is therefore restricted to the use of sub-optimal algorithms in order to fulfill time and memory storage requirements. A computationally cheap algorithm for general actuator/sensor placement objectives are proposed. A generalization of an actuator/sensor placement criterion for model updating, and a novel noise-robust actuator placement criterion for experimental modal analysis are proposed.

  • 78.
    Andersson, Magnus
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Model Updating - Identification of Mechanical Structures using Finite Element Models1996Inngår i: Proceedings of Reglermöte 1996, 1996, s. 51-55Konferansepaper (Annet vitenskapelig)
  • 79.
    Andersson, Magnus
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Noise Robust Actuator Placement on Flexible Structures1997Rapport (Annet vitenskapelig)
    Abstract [en]

    A novel criterion for placement of actuators on flexible mechanical structures is presented. Using simulated "measured modes" obtained from the model, the proposed criterion maximizes the correlation of the measured modes and the normal modes. The measured modes deviate from the normal modes due to damping, measurement noise and process noise. The statistical properties of the criterion are investigated. In simulations the computed actuator locations on a small aircraft-like model shows increased robustness properties against damping, for an acceptable loss of correlation. A computationally cheap actuator placement algorithm is proposed.

    Fulltekst (pdf)
    fulltext
    Fulltekst (ps)
    FULLTEXT01
  • 80.
    Andersson, Magnus
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan. SAAB AB, Sweden.
    Abrahamsson, Tom
    SAAB AB, Sweden.
    Avoiding Mode Pairing when Updating Finite Element Models1997Rapport (Annet vitenskapelig)
    Abstract [en]

    Updating nite element models of complex mechanical structures requires some extra considerations. It is stressed that the two most important aspects on updating finite element models are parameter estimation properties and computational expenses. A novel mode-pairing free model updating formulation is found to hav egood parameter estimation properties. The computational expenses are reduced with a semi-fixed modal basis, kept fixed during several iterations.

    Fulltekst (pdf)
    fulltext
    Fulltekst (ps)
    FULLTEXT01
  • 81.
    Andersson, Magnus
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Glad, Torkel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Norrlöf, Mikael
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Simulation and Animation Tool for Studying Multivariable Control2002Inngår i: Proceedings of the 15th IFAC World Congress, 2002, s. 1432-1432Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A simulation and animation tool for education in multivariable control is presented. The purpose of the tool is to support studies of various aspects of multivariable dynamical systems and design of multivariable feedback control systems. Different ways to use this kind of tool in control education are also presented and discussed.

  • 82.
    Andersson, Maria
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Migrering av styrsystem2006Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Holmen Paper AB är en av Europas ledande tillverkare av trähaltigt tryckpapper. De maskiner som tillverkar pappret har tills nyligen styrts av Siemens Teleperm M. Under 2005 gjordes en migrering av styrsystemet på en av pappersmaskinerna från Teleperm M till Siemens PcS7. Mjukvaruverktyget som skulle sköta migreringen kunde inte konvertera hela mjukvaran så en del av arbetet utfördes för hand. Detta resulterade i att funktionen blev enligt önskemål men koden blev onödigt komplicerad. Då det är eftersträvansvärt att ha en enkel kod för att underlätta felsökning är syftet med detta examensarbete att undersöka om samma förmåga fanns i två kretsar. Om så var fallet skulle en lösning hittas för att plocka bort den överflödiga kretsen.

    Arbetet resulterade i slutsatsen att det var möjligt att plocka bort ett av funktionsblocken samt förslag på koppling och implementering av detta. Resultatet ledde till förenklade kretsar.

    Fulltekst (pdf)
    FULLTEXT01
  • 83.
    Andersson, Maria
    et al.
    Swedish Defence Research Agency, Sweden.
    Gustafsson, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    St-Laurent, Louis
    INO, Canada.
    Prevost, Donald
    INO, Canada.
    Recognition of Anomalous Motion Patterns in Urban Surveillance2013Inngår i: IEEE Journal on Selected Topics in Signal Processing, ISSN 1932-4553, E-ISSN 1941-0484, Vol. 7, nr 1, s. 102-110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the unsupervised K-means clustering and the semi-supervised hidden Markov model (HMM) to automatically detect anomalous motion patterns in groups of people (crowds). Anomalous motion patterns are typically people merging into a dense group, followed by disturbances or threatening situations within the group. The application of K-means clustering and HMM are illustrated with datasets from four surveillance scenarios. The results indicate that by investigating the group of people in a systematic way with different K values, analyze cluster density, cluster quality and changes in cluster shape we can automatically detect anomalous motion patterns. The results correspond well with the events in the datasets. The results also indicate that very accurate detections of the people in the dense group would not be necessary. The clustering and HMM results will be very much the same also with some increased uncertainty in the detections.

    Fulltekst (pdf)
    fulltext
  • 84.
    Andersson, Markus
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik.
    Automatic Tuning of Motion Control System for an Autonomous Underwater Vehicle2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The interest for marine research and exploration has increased rapidly during the past decades and autonomous underwater vehicles (AUV) have been found useful in an increased amount of applications. The demand for versatile platform AUVs, able to perform a wide range of tasks, has become apparent. A vital part of an AUV is its motion control system, and an emerging problem for multipurpose AUVs is that the control performance is affected when the vehicle is configured with different payloads for each mission. Instead of having to manually re-tune the control system between missions, a method for automatic tuning of the control system has been developed in this master’s thesis.

    A model-based approach was implemented, where the current vehicle dynamics are identified by performing a sequence of excitation maneuvers, generating informative data. The data is used to estimate model parameters in predetermined model structures, and model-based control design is then used to determine an appropriate tuning of the control system.

    The performance and potential of the suggested approach were evaluated in simulation examples which show that improved control can be obtained by using the developed auto-tuning method. The results are considered to be sufficiently promising to justify implementation and further testing on a real AUV.

    The automatic tuning process is performed prior to a mission and is meant to compensate for dynamic changes introduced between separate missions. However, the AUV dynamics might also change during a mission which requires an adaptive control system. By using the developed automatic tuning process as foundation, the first steps towards an indirect adaptive control approach have been suggested.

    Also, the AUV which was studied in the thesis composed another interesting control problem by being overactuated in yaw control, this because yawing could be achieved by using rudders but also by differential drive of the propellers. As an additional and separate part of the thesis, an approach for using both techniques simultaneously have been proposed.

    Fulltekst (pdf)
    Automatic tuning of motion control system for an AUV
  • 85. Bestill onlineKjøp publikasjonen >>
    Andersson Naesseth, Christian
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Machine learning using approximate inference: Variational and sequential Monte Carlo methods2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Automatic decision making and pattern recognition under uncertainty are difficult tasks that are ubiquitous in our everyday life. The systems we design, and technology we develop, requires us to coherently represent and work with uncertainty in data. Probabilistic models and probabilistic inference gives us a powerful framework for solving this problem. Using this framework, while enticing, results in difficult-to-compute integrals and probabilities when conditioning on the observed data. This means we have a need for approximate inference, methods that solves the problem approximately using a systematic approach. In this thesis we develop new methods for efficient approximate inference in probabilistic models.

    There are generally two approaches to approximate inference, variational methods and Monte Carlo methods. In Monte Carlo methods we use a large number of random samples to approximate the integral of interest. With variational methods, on the other hand, we turn the integration problem into that of an optimization problem. We develop algorithms of both types and bridge the gap between them.

    First, we present a self-contained tutorial to the popular sequential Monte Carlo (SMC) class of methods. Next, we propose new algorithms and applications based on SMC for approximate inference in probabilistic graphical models. We derive nested sequential Monte Carlo, a new algorithm particularly well suited for inference in a large class of high-dimensional probabilistic models. Then, inspired by similar ideas we derive interacting particle Markov chain Monte Carlo to make use of parallelization to speed up approximate inference for universal probabilistic programming languages. After that, we show how we can make use of the rejection sampling process when generating gamma distributed random variables to speed up variational inference. Finally, we bridge the gap between SMC and variational methods by developing variational sequential Monte Carlo, a new flexible family of variational approximations.

    Delarbeid
    1. Capacity estimation of two-dimensional channels using Sequential Monte Carlo
    Åpne denne publikasjonen i ny fane eller vindu >>Capacity estimation of two-dimensional channels using Sequential Monte Carlo
    2014 (engelsk)Inngår i: 2014 IEEE Information Theory Workshop, 2014, s. 431-435Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We derive a new Sequential-Monte-Carlo-based algorithm to estimate the capacity of two-dimensional channel models. The focus is on computing the noiseless capacity of the 2-D (1, ∞) run-length limited constrained channel, but the underlying idea is generally applicable. The proposed algorithm is profiled against a state-of-the-art method, yielding more than an order of magnitude improvement in estimation accuracy for a given computation time.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-112966 (URN)10.1109/ITW.2014.6970868 (DOI)
    Konferanse
    Information Theory Workshop
    Tilgjengelig fra: 2015-01-06 Laget: 2015-01-06 Sist oppdatert: 2018-11-09
    2. Sequential Monte Carlo for Graphical Models
    Åpne denne publikasjonen i ny fane eller vindu >>Sequential Monte Carlo for Graphical Models
    2014 (engelsk)Inngår i: Advances in Neural Information Processing Systems, 2014, s. 1862-1870Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We propose a new framework for how to use sequential Monte Carlo (SMC) algorithms for inference in probabilistic graphical models (PGM). Via a sequential decomposition of the PGM we find a sequence of auxiliary distributions defined on a monotonically increasing sequence of probability spaces. By targeting these auxiliary distributions using SMC we are able to approximate the full joint distribution defined by the PGM. One of the key merits of the SMC sampler is that it provides an unbiased estimate of the partition function of the model. We also show how it can be used within a particle Markov chain Monte Carlo framework in order to construct high-dimensional block-sampling algorithms for general PGMs.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-112967 (URN)
    Konferanse
    Neural Information Processing Systems (NIPS)
    Tilgjengelig fra: 2015-01-06 Laget: 2015-01-06 Sist oppdatert: 2018-11-09bibliografisk kontrollert
    3. Nested Sequential Monte Carlo Methods
    Åpne denne publikasjonen i ny fane eller vindu >>Nested Sequential Monte Carlo Methods
    2015 (engelsk)Inngår i: Proceedings of The 32nd International Conference on Machine Learning / [ed] Francis Bach, David Blei, Journal of Machine Learning Research (Online) , 2015, Vol. 37, s. 1292-1301Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We propose nested sequential Monte Carlo (NSMC), a methodology to sample from sequences of probability distributions, even where the random variables are high-dimensional. NSMC generalises the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correct SMC algorithm. Furthermore, NSMC can in itself be used to produce such properly weighted samples. Consequently, one NSMC sampler can be used to construct an efficient high-dimensional proposal distribution for another NSMC sampler, and this nesting of the algorithm can be done to an arbitrary degree. This allows us to consider complex and high-dimensional models using SMC. We show results that motivate the efficacy of our approach on several filtering problems with dimensions in the order of 100 to 1 000.

    sted, utgiver, år, opplag, sider
    Journal of Machine Learning Research (Online), 2015
    Serie
    JMLR Workshop and Conference Proceedings, ISSN 1938-7228 ; 37
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-122698 (URN)2-s2.0-84969760860 (Scopus ID)9781510810587 (ISBN)
    Konferanse
    32nd International Conference on Machine Learning, Lille, France, 6-11 July, 2015
    Tilgjengelig fra: 2015-11-16 Laget: 2015-11-16 Sist oppdatert: 2021-07-20bibliografisk kontrollert
    4. Interacting Particle Markov Chain Monte Carlo
    Åpne denne publikasjonen i ny fane eller vindu >>Interacting Particle Markov Chain Monte Carlo
    Vise andre…
    2016 (engelsk)Inngår i: Proceedings of the 33rd International Conference on Machine Learning (ICML), 2016, Vol. 48, s. 2616-2625Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    We introduce interacting particle Markov chain Monte Carlo (iPMCMC), a PMCMC method based on an interacting pool of standard and conditional sequential Monte Carlo samplers. Like related methods, iPMCMC is a Markov chain Monte Carlo sampler on an extended space. We present empirical results that show significant improvements in mixing rates relative to both non-interacting PMCMC samplers and a single PMCMC sampler with an equivalent memory and computational budget. An additional advantage of the iPMCMC method is that it is suitable for distributed and multi-core architectures.

    Serie
    Proceedings of Machine Learning Research, ISSN 2640-3498 ; 48
    Emneord
    Sequential Monte Carlo, Probabilistic programming, parallelisation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-130043 (URN)
    Konferanse
    International Conference on Machine Learning (ICML), New York, USA, June 19-24, 2016
    Prosjekter
    CADICS
    Forskningsfinansiär
    Cancer and Allergy Foundation
    Tilgjengelig fra: 2016-07-05 Laget: 2016-07-05 Sist oppdatert: 2022-03-01bibliografisk kontrollert
    5. Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms
    Åpne denne publikasjonen i ny fane eller vindu >>Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms
    2017 (engelsk)Inngår i: Proceedings of the 20th International Conference on Artificial Intelligence and Statistics, PMLR , 2017Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Variational inference using the reparameterization trick has enabled large-scale approximate Bayesian inference in complex probabilistic models, leveraging stochastic optimization to sidestep intractable expectations. The reparameterization trick is applicable when we can simulate a random variable by applying a differentiable deterministic function on an auxiliary random variable whose distribution is fixed. For many distributions of interest (such as the gamma or Dirichlet), simulation of random variables relies on acceptance-rejection sampling. The discontinuity introduced by the accept-reject step means that standard reparameterization tricks are not applicable. We propose a new method that lets us leverage reparameterization gradients even when variables are outputs of a acceptance-rejection sampling algorithm. Our approach enables reparameterization on a larger class of variational distributions. In several studies of real and synthetic data, we show that the variance of the estimator of the gradient is significantly lower than other state-of-the-art methods. This leads to faster convergence of stochastic gradient variational inference.

    sted, utgiver, år, opplag, sider
    PMLR, 2017
    Serie
    Proceedings of Machine Learning Research, ISSN 1938-7228 ; 54
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-152645 (URN)000509368500053 ()
    Konferanse
    Artificial Intelligence and Statistics, 20-22 April 2017, Fort Lauderdale, FL, USA
    Tilgjengelig fra: 2018-11-09 Laget: 2018-11-09 Sist oppdatert: 2024-02-01
    6. Variational Sequential Monte Carlo
    Åpne denne publikasjonen i ny fane eller vindu >>Variational Sequential Monte Carlo
    2018 (engelsk)Inngår i: Proceedings of International Conference on Artificial Intelligence and Statistics, 9-11 April 2018, Playa Blanca, Lanzarote, Canary Islands / [ed] Amos Storkey and Fernando Perez-Cruz, PMLR , 2018, Vol. 84, s. 968-977Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Many recent advances in large scale probabilistic inference rely on variational methods. The success of variational approaches depends on (i) formulating a flexible parametric family of distributions, and (ii) optimizing the parameters to find the member of this family that most closely approximates the exact posterior. In this paper we present a new approximating family of distributions, the variational sequential Monte Carlo (VSMC) family, and show how to optimize it in variational inference. VSMC melds variational inference (VI) and sequential Monte Carlo (SMC), providing practitioners with flexible, accurate, and powerful Bayesian inference. The VSMC family is a variational family that can approximate the posterior arbitrarily well, while still allowing for efficient optimization of its parameters. We demonstrate its utility on state space models, stochastic volatility models for financial data, and deep Markov models of brain neural circuits.

    sted, utgiver, år, opplag, sider
    PMLR, 2018
    Serie
    Proceedings of Machine Learning Research, ISSN 2640-3498 ; 84
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-152646 (URN)000509385300102 ()2-s2.0-85057232074 (Scopus ID)
    Konferanse
    The 21st International Conference on Artificial Intelligence and Statistics, Playa Blanca, Lanzarote, Canary Islands, April 9-11, 2018
    Tilgjengelig fra: 2018-11-09 Laget: 2018-11-09 Sist oppdatert: 2024-02-01bibliografisk kontrollert
    Fulltekst (pdf)
    Machine learning using approximate inference: Variational and sequential Monte Carlo methods
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  • 86.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Schön, Thomas
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Capacity estimation of two-dimensional channels using Sequential Monte Carlo2014Inngår i: 2014 IEEE Information Theory Workshop, 2014, s. 431-435Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We derive a new Sequential-Monte-Carlo-based algorithm to estimate the capacity of two-dimensional channel models. The focus is on computing the noiseless capacity of the 2-D (1, ∞) run-length limited constrained channel, but the underlying idea is generally applicable. The proposed algorithm is profiled against a state-of-the-art method, yielding more than an order of magnitude improvement in estimation accuracy for a given computation time.

    Fulltekst (pdf)
    fulltext
  • 87.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Lindsten, Fredrik
    The University of Cambridge, Cambridge, United Kingdom.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Nested Sequential Monte Carlo Methods2015Inngår i: Proceedings of The 32nd International Conference on Machine Learning / [ed] Francis Bach, David Blei, Journal of Machine Learning Research (Online) , 2015, Vol. 37, s. 1292-1301Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose nested sequential Monte Carlo (NSMC), a methodology to sample from sequences of probability distributions, even where the random variables are high-dimensional. NSMC generalises the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correct SMC algorithm. Furthermore, NSMC can in itself be used to produce such properly weighted samples. Consequently, one NSMC sampler can be used to construct an efficient high-dimensional proposal distribution for another NSMC sampler, and this nesting of the algorithm can be done to an arbitrary degree. This allows us to consider complex and high-dimensional models using SMC. We show results that motivate the efficacy of our approach on several filtering problems with dimensions in the order of 100 to 1 000.

    Fulltekst (pdf)
    fulltext
  • 88.
    Andersson Naesseth, Christian
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Lindsten, Fredrik
    University of Cambridge, Cambridge, UK.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Sequential Monte Carlo for Graphical Models2014Inngår i: Advances in Neural Information Processing Systems, 2014, s. 1862-1870Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a new framework for how to use sequential Monte Carlo (SMC) algorithms for inference in probabilistic graphical models (PGM). Via a sequential decomposition of the PGM we find a sequence of auxiliary distributions defined on a monotonically increasing sequence of probability spaces. By targeting these auxiliary distributions using SMC we are able to approximate the full joint distribution defined by the PGM. One of the key merits of the SMC sampler is that it provides an unbiased estimate of the partition function of the model. We also show how it can be used within a particle Markov chain Monte Carlo framework in order to construct high-dimensional block-sampling algorithms for general PGMs.

    Fulltekst (pdf)
    fulltext
  • 89.
    Andersson, Olov
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Ljungqvist, Oskar
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Tiger, Mattias
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Axehill, Daniel
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Heintz, Fredrik
    Linköpings universitet, Institutionen för datavetenskap, Artificiell intelligens och integrerade datorsystem. Linköpings universitet, Tekniska fakulteten.
    Receding-Horizon Lattice-based Motion Planning with Dynamic Obstacle Avoidance2018Inngår i: 2018 IEEE Conference on Decision and Control (CDC), Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 4467-4474Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A key requirement of autonomous vehicles is the capability to safely navigate in their environment. However, outside of controlled environments, safe navigation is a very difficult problem. In particular, the real-world often contains both complex 3D structure, and dynamic obstacles such as people or other vehicles. Dynamic obstacles are particularly challenging, as a principled solution requires planning trajectories with regard to both vehicle dynamics, and the motion of the obstacles. Additionally, the real-time requirements imposed by obstacle motion, coupled with real-world computational limitations, make classical optimality and completeness guarantees difficult to satisfy. We present a unified optimization-based motion planning and control solution, that can navigate in the presence of both static and dynamic obstacles. By combining optimal and receding-horizon control, with temporal multi-resolution lattices, we can precompute optimal motion primitives, and allow real-time planning of physically-feasible trajectories in complex environments with dynamic obstacles. We demonstrate the framework by solving difficult indoor 3D quadcopter navigation scenarios, where it is necessary to plan in time. Including waiting on, and taking detours around, the motions of other people and quadcopters.

    Fulltekst (pdf)
    Receding-Horizon Lattice-based Motion Planning with Dynamic Obstacle Avoidance
  • 90.
    Andersson, Per
    et al.
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Eriksson, Lars
    Linköpings universitet, Institutionen för systemteknik, Fordonssystem. Linköpings universitet, Tekniska högskolan.
    Observer Based Feedforward Air-Fuel Control of Turbocharged SI-Engines2005Inngår i: Proceedings of 16th Triennial World Congress, Prague, Czech Republic, IFAC Papers Online, 2005, Vol. 38, s. 200-205Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Air-fuel control on turbocharged (TC) SI-engines require precise prediction of the cylinder air-charge (CAC). Using an observer it is possible to both estimate the necessary system states and to provide a framework to design the necessary CAC feedforward controller. Here a mean value engine model of a TC SI-engine is used to develop an observer. The output of the observer is fed as an initial condition to a predictor which is used for feedforward of the CAC for air-fuel control. The resulting controller is experimentally validated on a SAAB 2.0 dm3 TC engine using tip-in and tip-out transients. The results show that the excursions in Λ are less than 5%

  • 91.
    Andersson, Peter
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Forgetting in Recursive Identification through Multiple Models1984Inngår i: Analysis and Optimization of Systems: Proceedings of the Sixth International Conference on Analysis and Optimization of Systems, Nice, France, 19-22 June, 1984 / [ed] A. Bensoussan, J. L. Lions, New York: Springer Berlin/Heidelberg, 1984, s. 171-185Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    A new recursive identification method, Adaptive Forgetting through Multiple Models — AFMM, is presented and evaluated using computer simulations. AFMM is especially suited for identification of systems with jumping parameters or parameters that change in an irregular fashion. It can be viewed as a particular way of implementing adaptive gains or adaptive forgetting factors for recursive identification. The new method essentialy consists of multiple Recursive Least Squares (RLS) algorithms running in parallel, each with a corresponding weighting factor. The simulations indicate that AFMM is able to track rapidly changing parameters well, and that the method is robust in several respects.

  • 92.
    Andersson, Peter
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Forgetting in Recursive Identification through Multiple Models1984Rapport (Annet vitenskapelig)
    Abstract [en]

    A new recursive identification method, adaptive forgetting through multiple models (AFMM) is presented and evaluated using computer simulations. AFMM is especially suited for identification of systems with jumping or rapidly changing parameters. It can be viewed as a particular way of implementing adaptive gains or adaptive forgetting factors for recursive identification. The new method essentially consists of multiple recursive least-squares (RLS) algorithms running in parallel, each with a corresponding weighting factor. The simulations indicate that AFMM is able to track rapidly changing parameters well, and that the method is robust in several respects.

  • 93.
    Andersson, Peter
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Forgetting in Recursive Identification through Multiple Models1983Rapport (Annet vitenskapelig)
    Abstract [en]

    A new recursive identification method, adaptive forgetting through multiple models (AFMM) is presented and evaluated using computer simulations. AFMM is especially suited for identification of systems with jumping or rapidly changing parameters. It can be viewed as a particular way of implementing adaptive gains or adaptive forgetting factors for recursive identification. The new method essentially consists of multiple recursive least-squares (RLS) algorithms running in parallel, each with a corresponding weighting factor. The simulations indicate that AFMM is able to track rapidly changing parameters well, and that the method is robust in several respects.

  • 94.
    Andersson, Peter
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Forgetting in Recursive Identification through Multiple Models1983Rapport (Annet vitenskapelig)
    Abstract [en]

    A new recursive identification method, adaptive forgetting through multiple models (AFMM) is presented and evaluated using computer simulations. AFMM is especially suited for identification of systems with jumping or rapidly changing parameters. It can be viewed as a particular way of implementing adaptive gains or adaptive forgetting factors for recursive identification. The new method essentially consists of multiple recursive least-squares (RLS) algorithms running in parallel, each with a corresponding weighting factor. The simulations indicate that AFMM is able to track rapidly changing parameters well, and that the method is robust in several respects.

  • 95.
    Andersson, Peter
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Forgetting in Recursive Identification through Multiple Models1985Inngår i: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 42, nr 5, s. 1175-1193Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new recursive identification method, adaptive forgetting through multiple models (AFMM) is presented and evaluated using computer simulations. AFMM is especially suited for identification of systems with jumping or rapidly changing parameters. It can be viewed as a particular way of implementing adaptive gains or adaptive forgetting factors for recursive identification. The new method essentially consists of multiple recursive least-squares (RLS) algorithms running in parallel, each with a corresponding weighting factor. The simulations indicate that AFMM is able to track rapidly changing parameters well, and that the method is robust in several respects.

  • 96.
    Andersson, Peter
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Adaptive Forgetting through Multiple Models and Adaptive Control of Car Dynamics1983Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    A new recursive identif ication method, Adaptive Forgetting through Multiple Models - AFMM, is presented and evaluated using computer simulations. AFMM is specif ically suited for identification of systems with jumping or rapidly changing parameters. It can be viewed as a particular way of implementing adaptive gains or adaptive forgetting factors for recursive identif ication. The new method essentiallyconsists of multiple Recursive Least Squares (RLS) algorithms running in parallel, each with a corresponding weighting factor. The simulations indicate that AFMM is able to track rapidly changing parameters well, and that the method is robust in several respects.

  • 97.
    Andersson, Peter
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Control of a Diesel Generator with Varying Dynamics: A Comparison of Different Adaptive and Constant Regulators1984Rapport (Annet vitenskapelig)
  • 98.
    Andersson, Peter
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Test Case for Adaptive Control: Car Steering1981Rapport (Annet vitenskapelig)
  • 99.
    Andersson, Peter
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Ljung, Lennart
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    A Test Case for Adaptive Control: Car Steering1981Inngår i: Proceedings of the 1981 IFAC Symposium on Theory and Applications of Digital Control, 1981Konferansepaper (Fagfellevurdert)
  • 100.
    Andersson, Sören
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Asymptotic Analysis of Subspace Methods for Beamspace Direction-of-Arrival Estimation using Large Arrays1992Rapport (Annet vitenskapelig)
    Abstract [en]

    Asymptotic analysis methods for performance prediction of so-called subspace directionof -arrival estimation methods has been developed earlier, assuming that a large-enough number of array measurements, or snapshots, is collected. This paper also addresses the problem of making performance predictions, but for beamspace-based subspace methods. The novel approach in this paper assumes the number of array elements to be large, while the number of snapshots is arbitrary. The perturbation effect, due to additive sensor noise, on a certain subspace is used for establishing the asymptotic behavior of direction-of-arrival estimates. The asymptotic estimation errors for the estimators resulting from Signal Subspace Fitting methods, such as WSF, and Noise Subspace Fitting (NSF) methods, such as MUSIC and a multi-dimensional counterpart to WSF, are shown to be asymptotically unbiased and normally distributed. Provided that the array response vectors become orthogonal when the number of array elements increases, the NSF methods are shown to give consistent estimates even in the case of fully coherent emitter signals, and the WSF method is shown to be consistent for coherent emitter signals even without this assumption. Comparisons with results for Maximum-Likelihood methods yield conditions for guaranteeing efficiency of the methods. Some simulation examples are also included.

    Fulltekst (ps)
    FULLTEXT01
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