# Analysis and synthesis of combined cooperative control and topology control over wireless network models

## PIs: Hannes Frey (U Koblenz-Landau), Herbert Werner (TU Hamburg-Harburg)

In this project we consider cooperative control of mobile agents or nodes that interact over a wireless network. The network is set up by the nodes, i.e. no external communication infrastructure is assumed. Due to hardware constraints, in many cases only distributed approaches can be implemented. In such distributed cooperative control schemes, where each agent is equipped with a local control unit, the overall system performance is achieved by information exchange over a wireless communication network. Due to the broadcast property of the wireless network, agents can send samples in one transmission to their immediate neighbors. The subset of neighbors which further process the received samples in their local control is described by the interaction topology. This is a subgraph on top of the wireless communication graph. It is evident that a change in the topology as well as non-ideal communication will affect the performance and robustness of the interconnected system.

Cooperative control of multi-agent systems, as well as topology control in communication networks, have been studied extensively, but separately. Research on cooperative control of multi-agent systems usually assumes the interaction topology to be given (possibly uncertain). Research on topology control usually aims at improving the network in the sense of communication properties. However, as the interaction topology in a network of mobile agents has a considerable effect on the achievable cooperative control performance, a control scheme that combines dynamic control of the agents’ motion with adapting the interaction structure to the time-varying conditions of the communication network is expected to significantly improve the achievable performance. To the best of the applicants’ knowledge, to date such a combined control scheme has not been reported in the literature.

## Objectives

1. Local topology control will maintain the highest level of algebraic connectivity (aiming at high performance and robustness) while taking into account SINR constraints. This will be achieved by control of the wireless network graph and the interaction graph. Methods of investigation are graph spanners, backbones, and node relocation.
2. A distributed cooperative control scheme will be developed for LPV agent models and gain- scheduled local feedback controllers; this will allow to consider mobile robots and vehicles subject to nonholonomic constraints. Analysis and synthesis conditions will be derived that guarantee stability and performance in the sense of the L2 -norm, with a complexity independent of the number of agents while taking constraints on communication resources into account.
3. Local information about network properties will be gathered and used for topology control as well as for cooperative control to adapt interconnection weights. Our focus is on distributed and local solutions with the goal to support any system scale.
4. Proof of concept will be given by simulation studies based on source-seeking scenarios, which will be selected to highlight the various features of the proposed integrated collaborative control and topology control scheme.

## Involved PhD candidates

• Daniel Schneider (U Koblenz-Landau): (2012-2015) Working student/intern at Nuance Communications, site Ulm, (2016) Diploma (M.Sc.) in Mathematics, Ulm University, (2017) Research fellow at University of Koblenz within the project analysis and synthesis of combined cooperative control and topology control over wireless network models.

## Publications

1. Furugh Mirali and Herbert Werner: Distributed weighting strategies for improved convergence speed of first-order consensus, American Control Conference (ACC), IEEE, 2017.
2. Furugh Mirali, Antonio Mendez Gonzalez, and Herbert Werner: First-Order Average Consensus for Cooperative Control Problems Using Novel Weighting Strategies, IFAC-PapersOnLine 50.1 (2017): 14302-14307.
3. Jovan Radak, Lukas Baulig, Dawid Bijak, Christian Schowalter, Hannes Frey: Moving Towards Wireless Sensors using RSSI Measurements and Particle Filtering, 14th ACM Symposium on Performance Evaluation of Wireless Ad Hoc, Sensor, & Ubiquitous Networks - PE-WASUN (pp. 33–40), 2017.
4. Adwait Datar, Daniel Schneider, Furugh Mirali, Herbert Werner, Hannes Frey: A Memory Weighted Protocol for Sampled-Data Systems Subjected to Packet Dropouts, American Control Conference (ACC), IEEE, 2018.
5. Shashank Jadhav, Adwait Datar, Herbert Werner: Distributed Approach to Dynamic Quantization for Multi-Agent Systems, American Control Conference (ACC), IEEE, 2018.
6. Dennis Grewe, Marco Wagner, Sebastian Schildt, Mayutan Arumaithurai, Hannes Frey: Caching-as-a-Service in Virtualized Caches for Information-Centric Connected Vehicle Environments, IEEE Vehicular Networking Conference (VNC) (pp. 1–8), 2018.
7. Furugh Mirali and Herbert Werner: A Novel Sequence Weighting Method for First-Order Consensus Problems, IEEE Conference on Decision and Control (CDC), pp. 97-102, 2018.
8. Avi Turgeman, Adwait Datar and Herbert Werner: Gradient Free Source-Seeking Using Flocking Behavior, American Control Conference (ACC), IEEE, 2019. accepted
9. Christine Kloock and Herbert Werner: Distributed Model Predictive Control with Obstacle Communication, American Control Conference (ACC), IEEE, 2019. accepted
10. Jovan Radak, Daniel Schneider, Christian Henke and Hannes Frey: Performance of Consensus and Formation Control subject to Bernoulli, Slotted Aloha and IEEE 802.11p Simulation Models, Wireless and Mobile Networking Conference (WMNC), 2019. accepted
11. Daniel Schneider and Hannes Frey: Joint Optimization of Gain and Beaconing for First Order Consensus under Rayleigh Fading, IEEE International Conference on Computer Communications and Networks (ICCCN), 2019. accepted
12. Saadabadi, Hamideh and Werner, Herbert (2020). Event-Triggered Dynamic Output Feedback Control For Discrete-Time Polytopic Linear Parameter-Varying Systems. 59th IEEE Conference on Decision and Control. 98–103
13. Mirali, Furugh and Werner, Herbert (2020). A Dynamic Quasi-Taylor Approach for Distributed Consensus Problems with Packet Loss. 2020 Annual American Control Conference (ACC). 701–706
14. Kloock, Christine and Werner, Herbert (2020). Collision-Freeness and Feasibility in Non-Iterative Distributed Model Predictive Control with Prediction Mismatch. 59th IEEE Conference on Decision and Control
15. Hespe, Christian and Datar, Adwait and Werner, Herbert (2020). Distributed Control of Mobile LTI and LPV Agents Using Induced L2 to L$\infty$ Norms. 59th IEEE Conference on Decision and Control. 4360–4365
16. Attallah, Aly and Werner, Herbert (2020). Information Flow in Formation Control for Nonholonomic Agents Modeled as LPV Systems. European Control Conference. 459–464
17. Attallah, Aly and Datar, Adwait and Werner, Herbert (2020). Flocking of Linear Parameter Varying Agents: Source Seeking Application with Underwater Vehicles. 21st IFAC World Congress
18. Saadabadi, Hamideh and Werner, Herbert (2021).* Event-Triggered $L$ 2 -Optimal Formation Control for Agents Modeled as LPV Systems.* 2021 60th IEEE Conference on Decision and Control (CDC). 1256–1262
19. Datar, Adwait and Werner, Herbert (2021). Distributed Control of Heterogeneous Networks of Vehicles with Positive Systems Theory and Generalized H2 Norm. 60th IEEE Conference on Decision and Control.
20. Attallah, Aly and Werner, Herbert (2021). An Information Flow Filter Approach to Formation Control for Heterogeneously Scheduled LPV Agents. 60th IEEE Conference on Decision and Control.
21. Saadabadi, Hamideh and Hespe, Christian and Werner, Herbert (2022). Distributed Event-Triggered Consensus with Non-Identical Bernoulli Packet Dropout. 2022 European Control Conference (ECC). 1818–1823
22. Razzaghpour, Mahdi and Datar, Adwait and Schneider, Daniel and Zaman, Mahdi and Werner, Herbert and Frey, Hannes and Mohammadpour Velni, Javad and Fallah, Yaser (2022). Finite State Markov Modeling of {C-V2X} Erasure Links For Performance and Stability Analysis of Platooning Applications. 16th Annual IEEE International Systems Conference (SYSCON2022)
23. Gebhardt, Gerald and Saadabadi, Hamideh and Werner, Herbert (2022). Event-Triggered l{_}2-Optimal Formation Control with State-Estimation for Agents Modeled as LPV Systems. 61st IEEE Conference on Decision and Control.