Within the Networked Control group at the IST, we work towards having a more detailed view of the communication system and taking these details into account when designing controllers.
The main concept behind all of our approaches is to describe important aspects and potentials from communication theory in a mathematically rigorous fashion, and use them to address relevant control theoretic questions.
In Networked Control Systems, a predominant goal is bridging the gap between control systems and communication systems. In particular, this includes the design of network models that can serve as a basis for control systems providing a guaranteed quality of control. On the other hand, these network models should allow for an efficient implementation in communication infrastructures. To achieve results of such interdisciplinary value, appropriate network models play a key role.
One example for such a model is the communication abstraction, which was developed in our group in collaboration with the Distributed Systems group of the Institute for Parallel and Distributed Systems at the University of Stuttgart (Head: Prof. Rothermel). The major characteristic of this abstraction is the distinction between deterministic (reliable) transmissions for guaranteeing stability, and opportunistic (unreliable) transmissions for optimizing quality of control. The mathematical formulation of such an abstraction is closely related to the concept of weakly hard realtime constraints, a specification concept from the realtime systems area. We are constantly working on improving and extending this model as well as on characterizing research questions for classical control theoretic results that are of particular interest under such an abstraction.
Contact Persons: Frank Allgöwer, Steffen Linsenmayer, Stefan Wildhagen, Michael Hertneck
Publications:
 Steffen Linsenmayer, Ben W. Carabelli, Frank Dürr, Jonathan Falk, Frank Allgöwer, Kurt Rothermel
Integration of Communication Networks and Control Systems Using a Slotted Transmission Classification Model
in Proc. 16th IEEE Annual Consumer Communications and Networking Conference (CCNC) – 1st IEEE Workshop on CyberPhysical Networking (CPN2019), Las Vegas, NV, USA, 2019, pp. 1  6.  Steffen Linsenmayer, Frank Allgöwer
Stabilization of networked control systems with weakly hard realtime dropout description
in Proc. 56th IEEE Conference on Decision and Control (CDC), Melbourne, Australia, 2017, pp. 4765  4770.  Rainer Blind, Frank Allgöwer
Towards networked control systems with guaranteed stability: Using weakly hard realtime constraints to model the loss process
in Proc. 54th IEEE Conference on Decision and Control (CDC), Osaka, Japan, 2015, pp. 7510  7515.
When information is transmitted over a shared and possibly wireless channel, a number of applications communicate over the same network. Especially in such scenarios, communication resources are limited, such that it is advantageous to use the offered resources in an optimal way. For control applications in particular, a priori designed data transmission schedules (e.g. periodic schedules) are almost always suboptimal: control tasks require a lot of communication during precarious operating conditions, while when in a converged state, a much lower amount of communiation typically suffices.
With our research, we consider the novel approach to use an explicit dynamical model of the network's communication capacity, the token bucket model, to determine when information should be sent. By leveraging Model Predictive Control (MPC) to control both plant and network in a unified manner, both transmissions of new control values are scheduled and the corresponding control values are determined, optimizing a finitehorizon performance criterion. We investigate the interplay between control applications and the network and determine criteria under which desired control objectives, such as stability and a certain level of performance, can be ensured.
Contact Persons: Frank Allgöwer, Stefan Wildhagen
Publications:
 S. Wildhagen, M. A. Müller and F. Allgöwer.
Economic MPC Using a Cyclic Horizon with Application to Networked Control Systems
in Proc. 11th IFAC Symposium on Nonlinear Control Systems (NOLCOS), Vienna, Austria, 2019 (Accepted).
 S. Wildhagen, M. A. Müller and F. Allgöwer.
Predictive control over a dynamical tokenbucket network
in IEEE Control Systems Letters, Vol. 3, Iss. 4, pp. 859  864, 2019.
 S. Linsenmayer and F. Allgöwer.
Performance oriented triggering mechanisms with guaranteed traffic characterization for linear discretetime systems
in Proc. European Control Conference (ECC), Limassol, Cyprus, 2018, pp. 14741479.
When communication resources are limited, it may be favourable to determine transmission instants online based on the current system state instead of using traditional periodic sampling with fixed transmission intervals. This leads to a feedback interpretation of the communication process instead of the open loop approach that results from periodic transmissions.
Important questions in this area include not only identifying suitable trigger conditions but also finding appropriate descriptions for the resulting closedloop system properties, considering network effects, and understanding how these differ between timetriggered, eventtriggered, and selftriggered control. In our research, besides developing new triggering concepts, we also focus on better understanding of existing triggering concepts and on the mathematically rigorous analysis and comparison of the performance of event and selftriggered control to timetriggered control when network effects are taken into account.
In this research direction, we collaborate with Prof. Dragan Nešić from the University of Melbourne, Prof. Duarte Antunes from the Eindhoven Eindhoven University of Technology and Alejandro Maass from the Pontificia Universidad Católica de Chile.
Contact Persons: Frank Allgöwer, Michael Hertneck, David Meister
When studying stabilization problems for continuoustime control systems, the state is usually sampled periodically before being coded and sent over a channel. In such a scenario, fundamental bounds on the necessary bit rate for stabilization are known. On the other hand, a study of Kofman and Braslavsky in 2006 showed that using a sampling mechanism that employs state information, the necessary bit rate for stabilizing an unstable control system with one input and one output can be made arbitrarily small. Recently, this initiated research on the influence of such eventbased sampling strategies on the necessary bit rates for given control tasks.
In our research, we consider a setup where the controller is assumed to be static and the coder and decoder are assumed to be memoryless. The first control goal that we are interested in is containability. This system property was first introduced by Wong and Brockett in 1997 for a similar scenario but without eventbased sampling. Firstly, we analyzed scalar, unstable, linear control systems with timevarying but bounded transmission delays. After extending our results to uncertainties in the system dynamics, our current research focusses on more general system classes.
In this research direction, we collaborate with Prof. Hideaki Ishii from the Tokyo Institute of Technology.
Contact Persons: Frank Allgöwer, Steffen Linsenmayer
Publications:

Steffen Linsenmayer, Matthias A. Müller, Hideaki Ishii, Frank Allgöwer
Eventbased Containability for Linear Systems with Arbitrary Small Bit Rates
in Proc. 8th IFAC Workshop on Distributed Estimation and Control in
Networked Systems (NecSys), Chicago, IL, USA, 2019, to appear.  Steffen Linsenmayer, Hideaki Ishii, and Frank Allgöwer
Containability with eventbased sampling for scalar systems with timevarying delay and uncertainty
in IEEE Control Systems Letters, Vol. 2, No. 4, pp. 725–730, 2018.
 Steffen Linsenmayer, Rainer Blind and Frank Allgöwer
Delaydependent data rate bounds for containability of scalar systems
in Proc. of the 19th IFAC World Congress, Toulouse, France, 2017, pp. 7875  7880.
Publications
 M. Seidel, M. Hertneck, P. Yu, S. Linsenmayer, D. V. Dimarogonas, and F. Allgöwer, “A Windowbased Periodic Eventtriggered Consensus Scheme for Multiagent Systems,” IEEE Transactions on Control of Network Systems, vol. 11, no. 1, Art. no. 1, Mar. 2024, doi: 10.1109/tcns.2023.3285863.
 M. Hertneck and F. Allgöwer, “Robust dynamic selftriggered control for nonlinear systems using hybrid Lyapunov functions,” Nonlinear Analysis: Hybrid Systems, vol. 53, p. 101485, 2024, doi: 10.1016/j.nahs.2024.101485.
 D. Meister, F. Aurzada, M. A. Lifshits, and F. Allgöwer, “Time versus eventtriggered consensus of a singleintegrator multiagent system,” Nonlinear Analysis: Hybrid Systems, vol. 53, p. 101494, 2024, doi: 10.1016/j.nahs.2024.101494.
 M. Seidel, S. Lang, and F. Allgöwer, “On l2performance of weaklyhard realtime control systems,” European Journal of Control, p. 101056, Jun. 2024, doi: 10.1016/j.ejcon.2024.101056.
 M. Hertneck and F. Allgöwer, “Reverse average dwell time constraints enable arbitrary maximum allowable transmission intervals,” in Proc. 12th IFAC Symp. Nonlinear Control Systems (NOLCOS), in Proc. 12th IFAC Symp. Nonlinear Control Systems (NOLCOS). Canberra, Australia, 2023, pp. 379–384. doi: 10.1016/j.ifacol.2023.02.064.
 S. Schlor, R. Strässer, and F. Allgöwer, “Koopman interpretation and analysis of a publickey cryptosystem: DiffieHellman key exchange,” in Proc. 22nd IFAC World Congress, in Proc. 22nd IFAC World Congress. Yokohama, Japan, 2023, pp. 984–990. doi: 10.1016/j.ifacol.2023.10.1693.
 M. Hertneck and F. Allgöwer, “Selftriggered output feedback control for nonlinear networked control systems based on hybrid Lyapunov functions,” in Proc. 22nd IFAC World Congress, in Proc. 22nd IFAC World Congress. Tokyo, Japan, 2023, pp. 5748–5753. doi: 10.1016/j.ifacol.2023.10.165.
 D. Meister, F. Dürr, and F. Allgöwer, “Shared Network Effects in Time versus EventTriggered Consensus of a SingleIntegrator MultiAgent System,” in 22nd IFAC World Congress, in 22nd IFAC World Congress. Yokohama, Japan, 2023, pp. 5975–5980. doi: 10.1016/j.ifacol.2023.10.636.
 D. Meister and F. Allgöwer, “Performance implications of different pnorms in leveltriggered sampling,” in Proc. 62nd IEEE Conf. on Decision and Control (CDC), in Proc. 62nd IEEE Conf. on Decision and Control (CDC). Singapore, Singapore, 2023, pp. 3878–3883. doi: 10.1109/CDC49753.2023.10384009.
 D. Antunes, D. Meister, T. Namerikawa, F. Allgöwer, and W. P. M. H. Heemels, “Consistent eventtriggered consensus on complete graphs,” in Proc. 62nd IEEE Conf. on Decision and Control (CDC), in Proc. 62nd IEEE Conf. on Decision and Control (CDC). Singapore, Singapore, 2023, pp. 3911–3916. doi: 10.1109/CDC49753.2023.10384026.
 D. Meister, F. Aurzada, M. A. Lifshits, and F. Allgöwer, “Analysis of Time versus EventTriggered Consensus for a SingleIntegrator MultiAgent System,” in Proc. 61st IEEE Conf. on Decision and Control (CDC), in Proc. 61st IEEE Conf. on Decision and Control (CDC). Cancun, Mexico, 2022, pp. 441–446. doi: 10.1109/CDC51059.2022.9993301.
 M. Hertneck and F. Allgöwer, “Dynamic selftriggered control for nonlinear systems with delays,” in Proc. 9th IFAC Conf. on Networked Systems (NECSYS), in Proc. 9th IFAC Conf. on Networked Systems (NECSYS). Zürich, Switzerland, 2022, pp. 312–317. doi: 10.1016/j.ifacol.2022.07.278.
 M. Hertneck, S. Linsenmayer, and F. Allgöwer, “Efficient stability analysis approaches for nonlinear weaklyhard realtime control systems,” Automatica, vol. 133, p. 109868, 2021, doi: https://doi.org/10.1016/j.automatica.2021.109868.
 J. Berberich, S. Wildhagen, M. Hertneck, and F. Allgöwer, “Datadriven analysis and control of continuoustime systems under aperiodic sampling,” in Proc. 19th IFAC Symp. System Identification (SYSID), in Proc. 19th IFAC Symp. System Identification (SYSID). Padova, Italy, 2021, pp. 210–215. doi: 10.1016/j.ifacol.2021.08.360.
 M. Hertneck and F. Allgöwer, “Dynamic selftriggered control for nonlinear systems based on hybrid Lyapunov functions,” in Proc. 60th IEEE Conf. Decision and Control (CDC), in Proc. 60th IEEE Conf. Decision and Control (CDC). Austin, TX, USA, 2021, pp. 533–539. doi: 10.1109/CDC45484.2021.9682784.
 S. Schlor, M. Hertneck, S. Wildhagen, and F. Allgöwer, “Multiparty computation enables secure polynomial control based solely on secretsharing,” in Proc. 60th IEEE Conf. Decision and Control (CDC), in Proc. 60th IEEE Conf. Decision and Control (CDC). Austin, TX, USA, 2021, pp. 4882–4887. doi: 10.1109/CDC45484.2021.9683026.
 M. Hertneck and F. Allgöwer, “A Simple Approach to Increase the Maximum Allowable Transmission Interval,” in Proc. 3rd IFAC Conf. on Modelling, Identification and Control of Nonlinear Systems (MICNON), in Proc. 3rd IFAC Conf. on Modelling, Identification and Control of Nonlinear Systems (MICNON). Tokyo, Japan, 2021, pp. 443–448. doi: 10.1016/j.ifacol.2021.10.390.
 S. Linsenmayer, M. Hertneck, and F. Allgöwer, “Linear Weakly Hard RealTime Control Systems: Time and EventTriggered Stabilization,” IEEE Trans.\ Automat.\ Control, vol. 66, no. 4, Art. no. 4, 2021, doi: 10.1109/TAC.2020.3000981.
 M. Hertneck, S. Linsenmayer, and F. Allgöwer, “Stabilization of Nonlinear Weakly Hard RealTime Control Systems,” in Proc. 21st IFAC World Congress, in Proc. 21st IFAC World Congress. Berlin, Germany, 2020, pp. 2632–2637. doi: 10.1016/j.ifacol.2020.12.307.
 M. Hertneck, S. Linsenmayer, and F. Allgöwer, “Stability Analysis for Nonlinear Weakly Hard RealTime Control Systems,” in Proc. 21st IFAC World Congress, in Proc. 21st IFAC World Congress. Berlin, Germany, 2020, pp. 2632–2637. doi: 10.1016/j.ifacol.2020.12.307.
 M. Hertneck, S. Linsenmayer, and F. Allgöwer, “ModelBased Nonlinear Periodic EventTriggered Control for ContinuousTime Systems with SampledData Prediction,” in Proc. European Control Conf. (ECC), in Proc. European Control Conf. (ECC). Saint Petersburg, Russia, 2020, pp. 1814–1819.
 M. Hertneck and F. Allgöwer, “Exploiting Information for Decentralized Periodic EventTriggered Control,” in Proc. 59th IEEE Conf. Decision and Control (CDC), in Proc. 59th IEEE Conf. Decision and Control (CDC). Jeju, South Korea, 2020, pp. 4999–5004. doi: 10.1109/CDC42340.2020.9304456.
 M. Hertneck, S. Linsenmayer, and F. Allgöwer, “Nonlinear Dynamic Periodic EventTriggered Control with Robustness to Packet Loss Based on NonMonotonic Lyapunov Functions,” in Proc. 58th IEEE Conf. Decision and Control (CDC), in Proc. 58th IEEE Conf. Decision and Control (CDC). Nice, France, 2019, pp. 1680–1685. doi: 10.1109/CDC40024.2019.9029770.