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Knorn, Steffi
Publications (10 of 17) Show all publications
Chen, Z., Zhang, H., Zhu, L., Knorn, S. & Cheng, Z. (2017). Advanced Techniques for Networked Systems with Applications. Mathematical problems in engineering (Print), Article ID 3849019.
Open this publication in new window or tab >>Advanced Techniques for Networked Systems with Applications
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2017 (English)In: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147, article id 3849019Article in journal, Editorial material (Refereed) Published
Place, publisher, year, edition, pages
HINDAWI LTD, 2017
National Category
Computer and Information Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-322036 (URN)10.1155/2017/3849019 (DOI)000399055700001 ()
Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2018-01-13Bibliographically approved
Ferguson, J., Donaire, A., Knorn, S. & Middleton, R. H. (2017). Decentralized control for l(2) weak string stability of vehicle platoon. In: 20th IFAC World Congress: . Paper presented at 20th World Congress of the International-Federation-of-Automatic-Control (IFAC), JUL 09-14, 2017, Toulouse, FRANCE (pp. 15012-15017). Elsevier, 50(1)
Open this publication in new window or tab >>Decentralized control for l(2) weak string stability of vehicle platoon
2017 (English)In: 20th IFAC World Congress, Elsevier, 2017, Vol. 50, no 1, p. 15012-15017Conference paper, Published paper (Refereed)
Abstract [en]

In this paper we present a method of bidirectional control of a vehicle string that achieves l(2) weak string stability. Previous work required short-range communications between vehicles within the string. Here, we utilise some recent results on integral action to remove the requirement of communications altogether. (C) 2017, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2017
Series
IFAC-PapersOnLine, E-ISSN 2405-8963 ; 50:1
Keywords
Multi-vehicle systems, Lagrangian and Hamiltonian systems, Disturbance rejection
National Category
Computer Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-350697 (URN)10.1016/j.ifacol.2017.08.2572 (DOI)000423965400023 ()
Conference
20th World Congress of the International-Federation-of-Automatic-Control (IFAC), JUL 09-14, 2017, Toulouse, FRANCE
Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-07-06Bibliographically approved
Herman, I., Knorn, S. & Ahlén, A. (2017). Disturbance scaling in bidirectional vehicle platoons with different asymmetry in position and velocity coupling. Automatica, 82, 13-20
Open this publication in new window or tab >>Disturbance scaling in bidirectional vehicle platoons with different asymmetry in position and velocity coupling
2017 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 82, p. 13-20Article in journal (Refereed) Published
Abstract [en]

This paper considers a string of vehicles where the local control law uses the states of the vehicle's immediate predecessor and follower. The coupling towards the preceding vehicle can be chosen different to the coupling with the following vehicle, which is referred to as an asymmetric bidirectional string. Further, the asymmetry for the velocity coupling can be chosen differently to the asymmetry in the position coupling. It is investigated how the effect of the disturbance on the control errors in the string depends on the string length. It is shown, that in case of symmetric position coupling and asymmetric velocity coupling, linear scaling can be achieved. For symmetric interactions, the errors scale quadratically in the number of vehicles. When the coupling in position is asymmetric, exponential scaling may occur or the system might even become unstable. The paper thus gives a comprehensive overview of the achievable performance in linear, asymmetric, bidirectional platoons. The results reveal that symmetry in the position coupling and asymmetry in velocity coupling qualitatively improve the performance of the string. Extensive numerical results illustrate the theoretical findings.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2017
Keywords
Port-Hamiltonian systems, Vehicular platoons, Multi-vehicle systems, Scaling, Asymmetry
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-328962 (URN)10.1016/j.automatica.2017.04.010 (DOI)000403984300002 ()
Available from: 2017-09-12 Created: 2017-09-12 Last updated: 2017-09-12Bibliographically approved
Knorn, S., Varagnolo, D., Melles, R. & Dewitte, M. (2017). Mathematical Modelling Of Pressure Versus Pain Relations In Women Suffering From Dyspareunia. Journal of Sexual Medicine, 14(5), E335-E335
Open this publication in new window or tab >>Mathematical Modelling Of Pressure Versus Pain Relations In Women Suffering From Dyspareunia
2017 (English)In: Journal of Sexual Medicine, ISSN 1743-6095, E-ISSN 1743-6109, Vol. 14, no 5, p. E335-E335Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
dyspareunia, model, pain
National Category
Obstetrics, Gynecology and Reproductive Medicine Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-348323 (URN)10.1016/j.jsxm.2017.04.587 (DOI)000424205700454 ()
Funder
Swedish Research Council
Available from: 2018-04-24 Created: 2018-04-24 Last updated: 2018-05-03Bibliographically approved
Knorn, S. & Dey, S. (2017). Optimal energy allocation for linear control with packet loss under energy harvesting constraints. Automatica, 77, 259-267
Open this publication in new window or tab >>Optimal energy allocation for linear control with packet loss under energy harvesting constraints
2017 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 77, p. 259-267Article in journal (Refereed) Published
Abstract [en]

This paper studies a closed loop linear control system over a lossy communication link. A sensor computes a state estimate of the observed discrete-time system and sends it (in the form of packetized transmission) to the controller in the receiver block over a randomly time-varying (fading) packet dropping link. The receiver sends an ACK/NACK packet to the transmitter over an acknowledgement channel which might also be prone to packet loss. It is assumed that the energy used in packet transmission depletes a battery of limited capacity at the sensor, but is also replenished by an energy harvester which has access to a source of everlasting but random harvested energy. Under an assumption of finite-state Markov chain models of the energy harvesting and the fading channel gain processes, the objective is to design an optimal energy allocation policy at the transmitter and an optimal control policy at the receiver so that an average infinite horizon linear quadratic Gaussian (LQG) control cost is minimized. It is shown that in the case of perfect channel feedback a separation principle holds, the optimal LQG controller is linear and the optimal energy allocation policy at the transmitter can be obtained via solving the Bellman dynamic programming equation. A Q-learning algorithm is used to approximate the optimal energy allocation policy in case the system parameters are unknown. Numerical simulation examples show that the dynamic programming based policies outperform various simple heuristic policies, especially at higher battery capacities.

Keywords
Kalman filtering (KF), Energy harvesting, Imperfect acknowledgements
National Category
Computer and Information Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-306985 (URN)10.1016/j.automatica.2016.11.036 (DOI)000395354700028 ()
Available from: 2016-11-08 Created: 2016-11-08 Last updated: 2018-01-13Bibliographically approved
Varagnolo, D., Knorn, S., MeIles, R. & Dewitte, M. (2017). Qualitative modeling of pressure vs. pain relations in women suffering from dyspareunia. Paper presented at 20th World Congress of the International-Federation-of-Automatic-Control (IFAC), JUL 09-14, 2017, Toulouse, FRANCE. IFAC-PapersOnLine, 50(1), 2043-2050
Open this publication in new window or tab >>Qualitative modeling of pressure vs. pain relations in women suffering from dyspareunia
2017 (English)In: IFAC-PapersOnLine, ISSN 1045-0823, E-ISSN 1797-318X, Vol. 50, no 1, p. 2043-2050Article in journal (Refereed) Published
Abstract [en]

Genital pain / penetration disorders affect a significant portion of the female population and diminish significantly the quality of life of the subjects. Treatments, that often consist in stretching opportunely the vaginal duct by means of opportune vaginal dilators, are known to be invasive, lengthy and uncomfortable. Designing better treatments (e.g., more efficient locations and levels of pressures) nonetheless requires understanding better how the pressure developed in the vaginal channel affects the patient and leads to subjective pain. Here we take a control-oriented approach to the problem, and aim at describing the dynamics of the pressure vs. pain mechanisms by means of opportune state space representations. In particular, we first collect and discuss the medical literature, that describes how the variables that are involved in the treatment of genital pain / penetration disorders with vaginal dilators, are logically related. After this we translate (and complete) this set of logical relations into a qualitative model that allows control oriented analyses of the dynamics. The obtained state space model is then proved to both mimic correctly what is expected from logical perspectives and reproduce behaviors measured in clinical settings.

Keywords
genital pain, penetration disorders, state space models
National Category
Obstetrics, Gynecology and Reproductive Medicine Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-354390 (URN)10.1016/j.ifacol.2017.08.207 (DOI)000423845200329 ()
Conference
20th World Congress of the International-Federation-of-Automatic-Control (IFAC), JUL 09-14, 2017, Toulouse, FRANCE
Funder
Swedish Research Council
Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-07-06Bibliographically approved
Knorn, S. & Middleton, R. H. (2016). Asymptotic and exponential stability of nonlinear two-dimensional continuous-discrete Roesser models. Systems & control letters (Print), 93, 35-42
Open this publication in new window or tab >>Asymptotic and exponential stability of nonlinear two-dimensional continuous-discrete Roesser models
2016 (English)In: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 93, p. 35-42Article in journal (Refereed) Published
Abstract [en]

Sufficient conditions guaranteeing Lyapunov stability, asymptotic stability and exponential stability of nonlinear two-dimensional continuous-discrete systems are proposed. Special attention is paid to neutrally stable systems such as some two-dimensional system descriptions of vehicle platoons, which may be stable or asymptotically stable but never exponentially stable. Our conditions for Lyapunov stability and asymptotic stability only require the corresponding two-dimensional Lyapunov function to have a negative semidefinite divergence. They are thus suitable for the analysis of non-exponential versions of 2D stability. Examples are given to illustrate the results.

Keywords
Two-dimensional (2D), Nonlinear systems, Stability, Continuous-discrete
National Category
Control Engineering
Identifiers
urn:nbn:se:uu:diva-299709 (URN)10.1016/j.sysconle.2016.03.004 (DOI)000378461600005 ()
Available from: 2016-07-26 Created: 2016-07-26 Last updated: 2017-11-28Bibliographically approved
Knorn, S. & Ahlén, A. (2016). Deviation bounds in multi agent systems described by undirected graphs. Automatica, 67, 205-210
Open this publication in new window or tab >>Deviation bounds in multi agent systems described by undirected graphs
2016 (English)In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 67, p. 205-210Article in journal (Refereed) Published
Abstract [en]

The theory of port-Hamiltonian systems is used to derive upper bounds for the state deviations in multi agent systems described by undirected graphs pinned to a reference signal. The upper bounds for the deviations in networks of first or second order agents, respectively, depend on the minimal eigenvalue of the extended Laplacian of the system. In networks of first order agents, the deviations decay exponentially with a rate depending on the same minimal eigenvalue. In case networks of second order systems meet specific design properties, it can be shown that the deviations also decay exponentially with half the rate compared to first order systems.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-283644 (URN)10.1016/j.automatica.2016.01.038 (DOI)000373540300023 ()
Available from: 2016-04-14 Created: 2016-04-14 Last updated: 2017-11-30Bibliographically approved
Knorn, S., Chen, Z. & Middleton, R. (2016). Overview: Collective control of multi-agent systems. IEEE Transactions on Control of Network Systems, 3(4), 334-347
Open this publication in new window or tab >>Overview: Collective control of multi-agent systems
2016 (English)In: IEEE Transactions on Control of Network Systems, E-ISSN 2325-5870, Vol. 3, no 4, p. 334-347Article in journal (Refereed) Published
Abstract [en]

Collective control of amultiagent system is concerned with designing strategies for a group of autonomous agents operating in a networked environment. The aim is to achieve a global control objective through distributed sensing, communication, computing, and control. It has attracted many researchers from a wide range of disciplines, including the literature of automatic control. This paper aims to give a general framework that is able to accommodate many of these outcomes. Within this framework, the development on this topic is systematically reviewed and the representative outcomes can be sorted out from four aspects: 1) agent dynamics; 2) network topologies; 3) feedback and communication mechanisms; and 4) collective behaviors. Thus, the state-of-the-art approach and technology is described. Moreover, within this framework, further interesting and promising directions on this research topic are envisioned.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-268664 (URN)10.1109/TCNS.2015.2468991 (DOI)000390945400001 ()
Funder
Australian Research Council, DP130103039
Available from: 2015-12-09 Created: 2015-12-09 Last updated: 2017-02-02Bibliographically approved
Knorn, S., Dey, S., Ahlén, A. & Quevedo, D. E. (2015). Distortion Minimization in Multi-Sensor Estimation Using Energy Harvesting and Energy Sharing. IEEE Transactions on Signal Processing, 63(11), 2848-2863
Open this publication in new window or tab >>Distortion Minimization in Multi-Sensor Estimation Using Energy Harvesting and Energy Sharing
2015 (English)In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 63, no 11, p. 2848-2863Article in journal (Refereed) Published
Abstract [en]

This paper investigates an optimal energy allocation problem for multisensor estimation of a random source where sensors communicate their measurements to a remote fusion center (FC) over orthogonal fading wireless channels using uncoded analog transmissions. The FC reconstructs the source using the best linear unbiased estimator (BLUE). The sensors have limited batteries but can harvest energy and also transfer energy to other sensors in the network. A distortion minimization problem over a finite-time horizon with causal and noncausal centralized information is studied and the optimal energy allocation policy for transmission and sharing is derived. Several structural necessary conditions for optimality are presented for the two sensor problem with noncausal information and a horizon of two time steps. A decentralized energy allocation algorithm is also presented where each sensor has causal information of its own channel gain and harvested energy levels and has statistical information about the channel gains and harvested energies of the remaining sensors. Various other suboptimal energy allocation policies are also proposed for reducing the computational complexity of dynamic programming based solutions to the energy allocation problems with causal information patterns. Numerical simulations are included to illustrate the theoretical results. These illustrate that energy sharing can reduce the distortion at the FC when sensors have asymmetric fading channels and asymmetric energy harvesting processes.

Keywords
Energy allocation, energy harvesting, energy sharing, fading channels, multisensor estimation
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-256216 (URN)10.1109/TSP.2015.2416682 (DOI)000354382100010 ()
Available from: 2015-07-06 Created: 2015-06-22 Last updated: 2017-12-04Bibliographically approved
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