Dr Bjorn Ruffer
Lecturer
School of Mathematical and Physical Sciences (Mathematics)
 Email:bjorn.ruffer@newcastle.edu.au
 Phone:(02) 491 38169
Career Summary
Biography
Dr Rüffer graduated with a Master of Science in Mathematics from the University of Warwick, UK in 2004 and with a PhD in applied mathematics from the University of Bremen, Germany in 2007.
In Bremen, Dr Rüffer was a member of the Collaborative Research Centre 637 “Autonomous Cooperating Logistic Processes — A paradigm shift and its limitations” from September 2004 to September 2007. From October 2007 to June 2009 he was a member of the Signal Processing Microelectronics (SPM) group and the School of Electrical Engineering and Computer Science at the University of Newcastle, Australia. From July 2009 to January 2011 he was a Research Fellow within the Department of Electrical and Electronic Engineering at the University of Melbourne, Australia. In early 2010 he has undertaken a three months research fellowship at the Kyushu Institute of Technology, Japan, under the auspices of the Japan Society for the Promotion of Science (JSPS). From February 2011 to February 2015 he was an "Akademischer Rat auf Zeit" (assistant professor) with the Institute of Electrical Engineering at the University of Paderborn, Germany. In the summer term of 2014 he was a visiting professor at the University of Passau, Germany.
Dr Rüffer's research focuses on the qualitative theory of dynamical and control systems, in particular robust stability. Wellrecognised contributions include results on the stability of arbitrarily many interconnected, heterogeneous systems in the inputtostate stability framework. His interests further include synchronisation and consensus problems, all aspects of Lyapunov theory, as well as positive and monotone systems.
Teaching Expertise
Dr Rüffer has a teaching track record spanning more than a decade. He has taught at five different universities, covering subjects from mathematics as well as electrical engineering, and reaching students in a wide range of degree programs.
Administrative Expertise
Dr Rüffer has filled a number of administrative roles in the past, both at the university/discipline level as well as for the research community. Past roles include student advisor in an industrial engineering discipline, head of departmental computer labs, and member of various standing boards of examiners. Currently Dr Rüffer is an associate editor for Systems & Control Letters and serves on a number of programme committees for international conferences.
Collaborations
Dr Rüffer has past and ongoing collaborations with research partners in Australia, France, Germany, Iran, Israel, Japan, Russia, Sweden, the Netherlands, the United Kingdom, and the United States.
Qualifications
 PhD, University of Bremen  Germany
 Master of Science, University of Warwick  England
Keywords
 Control Theory
 Differential Equations
 Dynamical Systems
 Mathematical Systems Theory
 Mathematics
 Networks of dynamical systems
 Stability Theory
Languages
 German (Fluent)
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
UON Appointment
Title  Organisation / Department 

Lecturer  University of Newcastle School of Mathematical and Physical Sciences Australia 
Academic appointment
Dates  Title  Organisation / Department 

1/04/2014  1/09/2014  Visiting Professor  University of Passau Faculty of Computer Science and Mathematics Germany 
1/01/2012   Editorial Board  International Symposium on Mathematical Theory of Networks and Systems / Member of the international programme committee Australia 
1/01/2012   Editorial Board  International Symposium on Positive Systems / Member of the international programme committee Australia 
1/02/2011  1/02/2015  Assistant Professor (Akademischer Rat)  University of Paderborn Faculty of Electrical Engineering, Computer Science, and Mathematics Germany 
1/01/2010   Editorial Board  Systems & Control Letters / Associate Editor Australia 
1/07/2009  1/01/2011  Senior Research Fellow  The University of Melbourne Department of Electrical and Electronic Engineering Australia 
1/01/2008   Membership  American Mathematical Society United States 
1/01/2008   Membership  Institute of Electrical and Electronics Engineers United States 
1/10/2007  1/06/2009  Senior Research Associate  University of Newcastle School of Electrical Engineering and Computing Australia 
1/09/2004  1/09/2007  Research Associate  University of Bremen Faculty of Mathematics and Computer Science Germany 
1/01/2002   Membership  German Mathematicians Association Germany 
Teaching
Code  Course  Role  Duration 

MATH1110 
Mathematics 1 The University of Newcastle  Faculty of Science and IT Covers the parts of calculus and algebra which have proved fundamental to all of mathematics and its applications. It is the first of a pair of courses, MATH1110 and MATH1120, designed to cover a range of mathematical topics of importance to students in the Sciences, Engineering or Commerce. In algebra, students learn concepts and symbolic manipulation when calculating with large numbers of variables. In calculus, they learn concepts used when working with continuously changing variables. Both ways of thinking are essential in the mathematics met by students in the Sciences, Engineering and Commerce. 
Lecturer  1/03/2015  5/06/2015 
MATH2310 
Calculus of Science and Engineering The University of Newcastle  Faculty of Science and IT Provides the essential mathematical techniques of Physical Science and Engineering. These are the methods of Multivariable Calculus and Differential Equations. Multivariable Calculus involves a study of the differential and integral calculus of functions of two or more variables. In particular it covers introductory material on the differential calculus of scalar and vector fields, and the integral calculus of scalar and vector functions. Differential Equations arise from mathematical models of physical processes. Also includes the study of the main analytical and numerical methods for obtaining solutions to first and second order differential equations. The course also introduces students to the use of mathematical software in the investigation of problems in multivariable calculus and differential equations. 
Lecturer  27/07/2015  6/11/2015 
MATH3700 
Advanced Differential Equations The University of Newcastle  Faculty of Science and IT This course introduces students to the modern theory and methods of ordinary and partial differential equations. It builds on the classical foundations of differential equations studied in second year. Ordinary and partial differential equations form an essential part of the mathematical background required for engineering and the physical sciences. A large number of reallife problems can be modelled using differential equations, making the subject one of the most widely applicable areas of mathematics. The course concentrates on some fundamental analytical and numerical methods for applied differential equations arising from the mathematical modelling of physical, chemical and biological systems. 
Lecturer  27/07/2015  6/11/2015 
Publications
For publications that are currently unpublished or inpress, details are shown in italics.
Highlighted Publications
Year  Citation  Altmetrics  Link  

2010 
Ruffer BS, Kellett CM, Weller SR, 'Connection between cooperative positive systems and integral inputtostate stability of largescale systems', Automatica, 46 10191027 (2010) [C1]


2010 
Ruffer BS, 'Monotone inequalities, dynamical systems, and paths in the positive orthant of Euclidean nspace', Positivity, 14 257283 (2010) [C1]

Chapter (1 outputs)
Year  Citation  Altmetrics  Link  

2007 
ScholzReiter B, Wirth F, Freitag M, Dashkovskiy S, Jagalski T, De Beer C, Ruffer BS, 'Mathematical models of autonomous logistic processes', Understanding Autonomous Cooperation and Control in Logistics: The Impact of Autonomy on Management, Information, Communication and Material Flow, Springer, Berlin Heidelberg 121138 (2007)

Journal article (17 outputs)
Year  Citation  Altmetrics  Link  

2015 
Dirr G, Ito H, Rantzer A, Rueffer BS, 'SEPARABLE LYAPUNOV FUNCTIONS FOR MONOTONE SYSTEMS: CONSTRUCTIONS AND LIMITATIONS', DISCRETE AND CONTINUOUS DYNAMICAL SYSTEMSSERIES B, 20 24972526 (2015) [C1]


2014  Ruffer BS, 'Inputtostate stability for discretetime monotone systems', Proceedings of the 21st International Symposium om Mathematics Theory of Networks and Systems (MTNS), 96102 (2014)  
2013 
Ruffer BS, Van De Wouw N, Mueller M, 'Convergent systems vs. incremental stability', Systems and Control Letters, 62 277285 (2013)


2013 
Ito H, Jiang ZP, Dashkovskiy SN, Ruffer BS, 'Robust stability of networks of iISS systems: Construction of sumtype Lyapunov functions', IEEE Transactions on Automatic Control, 58 11921207 (2013)


2012 
Dashkovskiy SN, Jiang ZP, Ruffer BS, 'Special issue on robust stability and control of largescale nonlinear systems', Mathematics of Control, Signals, and Systems, 24 12 (2012)


2011  Ruffer BS, 'Discussion on: "On a small gain theorem for ISS networks in dissipative lyapunov form"', European Journal of Control, 17 366367 (2011)  
2011 
RÃ¼ffer BS, Wirth FR, 'Stability verification for monotone systems using homotopy algorithms', Numerical Algorithms, 58 529543 (2011) A monotone selfmapping of the nonnegative orthant induces a monotone discretetime dynamical system which evolves on the same orthant. If with respect to this system the origin i... [more] A monotone selfmapping of the nonnegative orthant induces a monotone discretetime 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 componentwise 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 socalled generalized smallgain conditions that appear in the stability theory of largescale systems. Â© 2011 Springer Science+Business Media, LLC.


2010 
Ruffer 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 11881200 (2010) [C1]


2010 
Ruffer BS, Sailer R, Wirth FR, 'Comments on "A Multichannel IOS Small Gain Theorem for Systems With Multiple TimeVarying Communication Delays', IEEE Transactions on Automatic Control, 55 17221725 (2010)


2010 
Dashkovskiy SN, Ruffer BS, 'Local ISS of largescale interconnections and estimates for stability regions', Systems and Control Letters, 59 241247 (2010)


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 40894118 (2010)


2010 
Ruffer BS, Kellett CM, Weller SR, 'Connection between cooperative positive systems and integral inputtostate stability of largescale systems', Automatica, 46 10191027 (2010) [C1]


2010 
Ruffer BS, 'SmallGain Conditions and the Comparison Principle', IEEE TRANSACTIONS ON AUTOMATIC CONTROL, 55 17321736 (2010)


2007 
Dashkovskiy S, Ruffer BS, Wirth FR, 'An ISS small gain theorem for general networks', Mathematics of Control, Signals, and Systems, 19 93122 (2007)


Show 14 more journal articles 
Conference (28 outputs)
Year  Citation  Altmetrics  Link  

2017 
RÃ¼ffer BS, 'Nonlinear left and right eigenvectors for maxpreserving maps' (2017) [E1]


2016 
Tran DN, RÃ¼ffer BS, Kellett CM, 'Incremental stability properties for discretetime systems', 2016 IEEE 55th Conference on Decision and Control, CDC 2016 (2016) [E1]


2016 
Fernando DAIP, Ruffer B, 'A preliminary model for understanding how life experiences generate human emotions and behavioural responses', Neural Information Processing. 23rd International Conference, ICONIP 2016 (2016) [E1]


2015 
Ruffer BS, Ito H, 'Sumseparable Lyapunov functions for networks of ISS systems: A gain function approach', Proceedings of the IEEE Conference on Decision and Control (2015) [E1]


2014 
Noroozi N, Ruffer BS, 'Nonconservative dissipativity and smallgain theory for ISS networks', Proceedings of the IEEE Conference on Decision and Control (2014) Â© 2014 IEEE.This paper addresses inputtostate stability (ISS) analysis for discretetime systems using the notion of finitestep ISS Lyapunov functions. Here, finitestep Lyapu... [more] Â© 2014 IEEE.This paper addresses inputtostate stability (ISS) analysis for discretetime systems using the notion of finitestep ISS Lyapunov functions. Here, finitestep Lyapunov functions are energy functions that decay after a fixed but finite number of steps, rather than at every time step. We establish nonconservative dissipativity and smallgain conditions for ISS of networks of discretetime systems, by generalizing results in [1] and [2] to the case of ISS. The effectiveness of the results is illustrated through two examples.


2014 
Ito H, Ruffer BS, Rantzer A, 'Max and sumseparable Lyapunov functions for monotone systems and their level sets', Proceedings of the IEEE Conference on Decision and Control (2014) Â© 2014 IEEE.For interconnected systems and systems of large size, aggregating information of subsystems studied individually is useful for addressing the overall stability. In th... [more] Â© 2014 IEEE.For interconnected systems and systems of large size, aggregating information of subsystems studied individually is useful for addressing the overall stability. In the Lyapunovbased analysis, summation and maximization of separately constructed functions are two typical approaches in such a philosophy. This paper focuses on monotone systems which are common in control applications and elucidates some fundamental limitations of maxseparable Lyapunov functions in estimating domains of attractions. This paper presents several methods of constructing sum and maxseparable Lyapunov functions for second order monotone systems, and some comparative discussions are given through illustrative examples.


2013 
Pogromsky AY, Matveev AS, Chaillet A, Ruffer BS, 'Inputdependent stability analysis of systems with saturation in feedback', Proceedings of the IEEE Conference on Decision and Control (2013)


2013 
Chaillet A, Pogromsky AY, Ruffer BS, 'A Razumikhin approach for the incremental stability of delayed nonlinear systems', Proceedings of the IEEE Conference on Decision and Control (2013)


2013 
Rantzer A, Ruffer BS, Dirr G, 'Separable Lyapunov functions for monotone systems', Proceedings of the IEEE Conference on Decision and Control (2013)


2013 
Ito H, Ruffer BS, 'A twophase approach to stability of networks given in iISS framework: Utilization of a matrixlike criterion', Proceedings of the American Control Conference (2013) This article is concerned with global asymptotic stability (GAS) of dynamical networks. The case when subsystems are integral inputtostate stable (iISS) has been recognized as n... [more] This article is concerned with global asymptotic stability (GAS) of dynamical networks. The case when subsystems are integral inputtostate stable (iISS) has been recognized as notoriously difficult to deal with in the literature. In fact, the lack of energy dissipation for large input denies direct application of the smallgain argument for inputtostate stable (ISS) subsystems. Here for networks consisting of iISS subsystems it is demonstrated that a twophase approach allows us to make use of the ISS smallgain argument by separating a trajectory into a transient and a subsequent ISSlike phase. In contrast to the previous iISS results, the twophase approach immediately leads to a sufficiency criterion for GAS of general nonlinear networks, which is given in a matrixlike form (order condition). Â© 2013 AACC American Automatic Control Council. 

2012 
Ruffer BS, Van De Wouw N, Mueller M, 'From convergent dynamics to incremental stability', Proceedings of the IEEE Conference on Decision and Control (2012)


2012 
Ito H, Jiang ZP, Dashkovskiy SN, RÃ¼ffer BS, 'A cyclic smallgain condition and an equivalent matrixlike criterion for iISS networks', Proceedings of the IEEE Conference on Decision and Control (2012)


2012 
Dashkovskiy SN, Ruffer BS, Wirth FR, 'Small gain theorems for large scale systems and construction of ISS Lyapunov functions', Proceedings of the IEEE Conference on Decision and Control (2012)


2011 
Ito H, Jiang ZP, Dashkovskiy SN, Ruffer BS, 'A smallgain theorem and construction of sumtype Lyapunov functions for networks of iISS systems', Proceedings of the American Control Conference (2011)


2010 
Ruffer BS, Ito H, Dower PM, 'Computing asymptotic gains of largescale interconnections', Proceedings of the IEEE Conference on Decision and Control (2010)


2009 
Ruffer BS, Kellett CM, Weller SR, 'Integral inputtostate stability of interconnected iISS systems by means of a lowerdimensional comparison system', Proceedings of the 48th IEEE Conference on Decision and Control, 2009 held jointly with the 2009 28th Chinese Control Conference, CDC/CCC 2009 (2009) [E1]


2007 
Dashkovskiy SN, Ruffer BS, Wirth FR, 'Numerical verification of local inputtostate stability for large networks', PROCEEDINGS OF THE 46TH IEEE CONFERENCE ON DECISION AND CONTROL, VOLS 114 (2007)


2007  Dashkovskiy SN, Ruffer BS, Wirth FR, 'A Lyapunov ISS smallgain theorem for strongly connected networks', IFAC Proceedings Volumes (IFACPapersOnline) (2007)  
2005 
Dashkovskiy S, Ruffer BS, Wirth FR, 'A smallgain type stability criterion for large scale networks of ISS systems', Proceedings of the 44th IEEE Conference on Decision and Control, and the European Control Conference, CDCECC '05 (2005)


Show 25 more conferences 
Report (2 outputs)
Year  Citation  Altmetrics  Link 

2008  Ruffer BS, Kellett CM, 'Implementing the Belief Propagation Algorithm in MATLAB', Department of Electrical Engineering and Computer Science, University of Newcastle (2008)  
2006  Dashkovskiy SN, Ruffer BS, 'Construction of ISS Lyapunov functions for networks', ZeTeM, Universitat Bremen, Germany (2006) 
Thesis / Dissertation (1 outputs)
Year  Citation  Altmetrics  Link 

2007  Ruffer BS, Monotone dynamical systems, graphs, and stability of largescale inter connected systems, Universitat Bremen, Germany (2007) 
Research Supervision
Number of supervisions
Total current UON EFTSL
Current Supervision
Commenced  Level of Study  Research Title  Program  Supervisor Type 

2017  PhD  A PostKeynesian SFC Model of GFC and Secular Stagnation  PhD (Economics), Faculty of Business and Law, The University of Newcastle  CoSupervisor 
2015  PhD  Nonlinear Model Predictive Path Following Control for Model Robot  PhD (Electrical Engineering), Faculty of Engineering and Built Environment, The University of Newcastle  CoSupervisor 
Research Collaborations
The map is a representation of a researchers coauthorship with collaborators across the globe. The map displays the number of publications against a country, where there is at least one coauthor 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  25  
Australia  15  
Japan  8  
Netherlands  4  
United States  4  
More... 
Dr Bjorn Ruffer
Position
Lecturer
School of Mathematical and Physical Sciences
Faculty of Science
Focus area
Mathematics
Contact Details
bjorn.ruffer@newcastle.edu.au  
Phone  (02) 491 38169 
Fax  (02) 492 16898 
Links 
Google+ Personal webpage 
Office
Room  V227 

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