Dr Bjorn Ruffer

Dr Bjorn Ruffer

Lecturer

School of Mathematical and Physical Sciences (Mathematics)

Career Summary

Biography

Dr Rüffer received the MSc (w/ distinction) in mathematics degree from
the University of Warwick, UK, in 2004, and the Dr. rer. nat. (PhD)
degree in mathematics from the University of Bremen, Germany, in 2007.

After a sequence of post-doctoral appointments at the University of
Newcastle (2007-2009), the University of Melbourne (2009-2011), and
the University of Paderborn (2011-2015), he re-joined the University
of Newcastle in 2015. He has held visiting positions at the Kyushu
Institute of Technology, Japan, the University of Passau, Germany, and
the University of British Columbia, Canada.

To the research community Dr Rüffer contributes as a referee for a
number of scientific journals and conferences, as an organiser of
scientific conferences, as associate editor for two flagship journals,
and as reviewer for a couple of European research funding bodies. At
the University of Newcastle he has served as a member of the Academic
Senate and a member of the Faculty Board of the Faculty of Science
(both 2016-2017).


Qualifications

  • PhD, University of Bremen - Germany
  • Master of Science, University of Warwick - England

Keywords

  • Systems theory and control
  • Decentralized and large scale systems
  • Robust, asymptotic, input-output stability
  • Scalar and vector Lyapunov functions
  • Theory of error-correcting codes
  • Homotopy methods
  • Ordinary differential equations
  • Semirings
  • Dynamical systems and ergodic theory
  • Difference and functional equations
  • Operator theory

Fields of Research

Code Description Percentage
010109 Ordinary Differential Equations, Difference Equations and Dynamical Systems 35
010203 Calculus of Variations, Systems Theory and Control Theory 50
010204 Dynamical Systems in Applications 15

Professional Experience

Academic appointment

Dates Title Organisation / Department
28/04/2018 - 28/06/2018 Visiting Professor University of British Columbia
Canada
1/04/2014 - 1/09/2014 Visiting Professor University of Passau
Faculty of Computer Science and Mathematics
Germany

Membership

Dates Title Organisation / Department
15/05/2018 -  Associate Editor Automatica J. IFAC
Netherlands
1/01/2016 -  Member, SIAM Society for Industrial and Applied Mathematics (SIAM)
United States
1/01/2010 -  Associate Editor Systems & Control Letters
Netherlands
1/01/2008 -  Senior Member, IEEE Institute of Electrical and Electronics Engineers
United States

Awards

Recognition

Year Award
2018 Outstanding reviewer for 2016-2017
Automatica J. IFAC

Research Award

Year Award
2012 Premium Award (best paper)
IET

Teaching

Code Course Role Duration
SSP Study Leave
School of Mathematical and Physical Sciences
Currently on study leave. No more courses in 2018. 1/05/2018 - 31/10/2018
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Publications

For publications that are currently unpublished or in-press, details are shown in italics.

Highlighted Publications

Year Citation Altmetrics Link
2007 Dashkovskiy S, Ruffer BS, Wirth FR, 'An ISS small gain theorem for general networks', Mathematics of Control, Signals, and Systems, 19 93-122 (2007)
DOI 10.1007/s00498-007-0014-8
Citations Scopus - 202Web of Science - 176
2010 Dashkovskiy SN, Ruffer BS, Wirth FR, 'Small gain theorems for large scale systems and construction of ISS Lyapunov functions', SIAM Journal on Control and Optimization, 48 4089-4118 (2010)
DOI 10.1137/090746483
Citations Scopus - 175Web of Science - 149
2010 Ruffer BS, Kellett CM, Weller SR, 'Connection between cooperative positive systems and integral input-to-state stability of large-scale systems', Automatica, 46 1019-1027 (2010) [C1]
DOI 10.1016/j.automatica.2010.03.012
Citations Scopus - 40Web of Science - 35
Co-authors Chris Kellett, Steven Weller
2013 Ruffer BS, Van De Wouw N, Mueller M, 'Convergent systems vs. incremental stability', Systems and Control Letters, 62 277-285 (2013) [C1]
DOI 10.1016/j.sysconle.2012.11.015
Citations Scopus - 35Web of Science - 31

Journal article (15 outputs)

Year Citation Altmetrics Link
2018 Noroozi N, Geiselhart R, Gruene L, Ruffer BS, Wirth FR, 'Nonconservative Discrete-Time ISS Small-Gain Conditions for Closed Sets', IEEE TRANSACTIONS ON AUTOMATIC CONTROL, 63 1231-1242 (2018) [C1]
DOI 10.1109/TAC.2017.2735194
2018 Guiver C, Logemann H, Rüffer B, 'Small-gain stability theorems for positive Lur¿e inclusions', Positivity, (2018)

© 2018, The Author(s). Stability results are presented for a class of differential and difference inclusions, so-called positive Lur¿e inclusions which arise, for example, as the ... [more]

© 2018, The Author(s). Stability results are presented for a class of differential and difference inclusions, so-called positive Lur¿e inclusions which arise, for example, as the feedback interconnection of a linear positive system with a positive set-valued static nonlinearity. We formulate sufficient conditions in terms of weighted one-norms, reminiscent of the small-gain condition, which ensure that the zero equilibrium enjoys various global stability properties, including asymptotic and exponential stability. We also consider input-to-state stability, familiar from nonlinear control theory, in the context of forced positive Lur¿e inclusions. Typical for the study of positive systems, our analysis benefits from comparison arguments and linear Lyapunov functions. The theory is illustrated with examples.

DOI 10.1007/s11117-018-0605-2
2015 Dirr G, Ito H, Rantzer A, Rueffer BS, 'SEPARABLE LYAPUNOV FUNCTIONS FOR MONOTONE SYSTEMS: CONSTRUCTIONS AND LIMITATIONS', DISCRETE AND CONTINUOUS DYNAMICAL SYSTEMS-SERIES B, 20 2497-2526 (2015) [C1]
DOI 10.3934/dcdsb.2015.20.2497
Citations Scopus - 17Web of Science - 12
2014 Rüffer BS, 'Input-to-state stability for discrete-time monotone systems', Proceedings of the 21st International Symposium on Mathematics Theory of Networks and Systems (MTNS), 96-102 (2014)
2013 Ruffer BS, Van De Wouw N, Mueller M, 'Convergent systems vs. incremental stability', Systems and Control Letters, 62 277-285 (2013) [C1]
DOI 10.1016/j.sysconle.2012.11.015
Citations Scopus - 35Web of Science - 31
2013 Ito H, Jiang Z-P, Dashkovskiy SN, Rüffer BS, 'Robust stability of networks of iISS systems: Construction of sum-type Lyapunov functions', IEEE Transactions on Automatic Control, 58 1192-1207 (2013) [C1]
DOI 10.1109/TAC.2012.2231552
Citations Scopus - 40Web of Science - 34
2011 Rüffer BS, Wirth FR, 'Stability verification for monotone systems using homotopy algorithms', Numerical Algorithms, 58 529-543 (2011) [C1]

A monotone self-mapping of the nonnegative orthant induces a monotone discrete-time dynamical system which evolves on the same orthant. If with respect to this system the origin i... [more]

A monotone self-mapping of the nonnegative orthant induces a monotone discrete-time dynamical system which evolves on the same orthant. If with respect to this system the origin is attractive then there must exist points whose image under the monotone map is strictly smaller than the original point, in the component-wise partial ordering. Here it is shown how such points can be found numerically, leading to a recipe to compute order intervals that are contained in the region of attraction and where the monotone map acts essentially as a contraction. An important application is the numerical verification of so-called generalized small-gain conditions that appear in the stability theory of large-scale systems. © 2011 Springer Science+Business Media, LLC.

DOI 10.1007/s11075-011-9468-3
Citations Scopus - 5Web of Science - 3
2010 Rüffer BS, Kellett CM, Dower PM, Weller SR, 'Belief propagation as a dynamical system: The linear case and open problems', IET Control Theory and Applications, 4 1188-1200 (2010) [C1]
DOI 10.1049/iet-cta.2009.0233
Citations Scopus - 9Web of Science - 7
Co-authors Steven Weller, Chris Kellett
2010 Ruffer BS, Sailer R, Wirth FR, 'Comments on "A Multichannel IOS Small Gain Theorem for Systems With Multiple Time-Varying Communication Delays', IEEE Transactions on Automatic Control, 55 1722-1725 (2010)
DOI 10.1109/TAC.2010.2048938
Citations Scopus - 5Web of Science - 5
2010 Dashkovskiy SN, Ruffer BS, 'Local ISS of large-scale interconnections and estimates for stability regions', Systems and Control Letters, 59 241-247 (2010)
DOI 10.1016/j.sysconle.2010.02.001
Citations Scopus - 25Web of Science - 20
2010 Dashkovskiy SN, Ruffer BS, Wirth FR, 'Small gain theorems for large scale systems and construction of ISS Lyapunov functions', SIAM Journal on Control and Optimization, 48 4089-4118 (2010)
DOI 10.1137/090746483
Citations Scopus - 175Web of Science - 149
2010 Ruffer BS, Kellett CM, Weller SR, 'Connection between cooperative positive systems and integral input-to-state stability of large-scale systems', Automatica, 46 1019-1027 (2010) [C1]
DOI 10.1016/j.automatica.2010.03.012
Citations Scopus - 40Web of Science - 35
Co-authors Chris Kellett, Steven Weller
2010 Rüffer BS, 'Small-Gain Conditions and the Comparison Principle', IEEE TRANSACTIONS ON AUTOMATIC CONTROL, 55 1732-1736 (2010)
DOI 10.1109/TAC.2010.2048053
Citations Scopus - 21Web of Science - 18
2010 Ruffer BS, 'Monotone inequalities, dynamical systems, and paths in the positive orthant of Euclidean n-space', Positivity, 14 257-283 (2010) [C1]
DOI 10.1007/s11117-009-0016-5
Citations Scopus - 42Web of Science - 33
2007 Dashkovskiy S, Ruffer BS, Wirth FR, 'An ISS small gain theorem for general networks', Mathematics of Control, Signals, and Systems, 19 93-122 (2007)
DOI 10.1007/s00498-007-0014-8
Citations Scopus - 202Web of Science - 176
Show 12 more journal articles
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Grants and Funding

Summary

Number of grants 1
Total funding $463,458

Click on a grant title below to expand the full details for that specific grant.


20161 grants / $463,458

Activating Lyapunov-Based Feedback - Nonsmooth Control Lyapunov Functions$463,458

Funding body: ARC (Australian Research Council)

Funding body ARC (Australian Research Council)
Project Team Professor Christopher Kellett, Professor Lars Grune, Dr Sigurdur Hafstein, Doctor Bjoern Rueffer, Grunene, Lars, Hafstein, Sigurdur
Scheme Discovery Projects
Role Investigator
Funding Start 2016
Funding Finish 2018
GNo G1500106
Type Of Funding Aust Competitive - Commonwealth
Category 1CS
UON Y
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Research Supervision

Number of supervisions

Completed0
Current3

Current Supervision

Commenced Level of Study Research Title Program Supervisor Type
2018 Masters Investigating the Dynamics of Human Relationships and Emotions using a Mathematical Theory for Social Networks M Philosophy (Mathematics), Faculty of Science, The University of Newcastle Principal Supervisor
2017 PhD A Post-Keynesian SFC Model of GFC and Secular Stagnation PhD (Economics), Faculty of Business and Law, The University of Newcastle Co-Supervisor
2015 PhD Advances in Stability Analysis for Nonlinear Discrete-Time Dynamical Systems PhD (Electrical Engineering), Faculty of Engineering and Built Environment, The University of Newcastle Co-Supervisor
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Research Collaborations

The map is a representation of a researchers co-authorship with collaborators across the globe. The map displays the number of publications against a country, where there is at least one co-author based in that country. Data is sourced from the University of Newcastle research publication management system (NURO) and may not fully represent the authors complete body of work.

Country Count of Publications
Germany 27
Australia 17
Japan 8
Netherlands 4
United States 4
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Dr Bjorn Ruffer

Position

Lecturer
School of Mathematical and Physical Sciences
Faculty of Science

Focus area

Mathematics

Contact Details

Email bjorn.ruffer@newcastle.edu.au
Phone (02) 491 38169
Fax (02) 492 16898
Links Personal webpage
Research Networks

Office

Room V227
Building Mathematics Building
Location Callaghan
University Drive
Callaghan, NSW 2308
Australia
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