Search Results for author: Karl H. Johansson

Found 61 papers, 7 papers with code

Safe Reinforcement Learning Using Black-Box Reachability Analysis

1 code implementation15 Apr 2022 Mahmoud Selim, Amr Alanwar, Shreyas Kousik, Grace Gao, Marco Pavone, Karl H. Johansson

Reinforcement learning (RL) is capable of sophisticated motion planning and control for robots in uncertain environments.

Motion Planning reinforcement-learning +2

Logical Zonotopes: A Set Representation for the Formal Verification of Boolean Functions

1 code implementation16 Oct 2022 Amr Alanwar, Frank J. Jiang, Samy Amin, Karl H. Johansson

A logical zonotope, which is a new set representation for binary vectors, is introduced in this paper.

Formal Verification with Constrained Polynomial Logical Zonotope

1 code implementation27 Mar 2024 Ahmad Hafez, Frank J. Jiang, Karl H. Johansson, Amr Alanwar

To address this, we formulate constrained polynomial logical zonotopes, which maintain the computational efficiency and exactness of polynomial logical zonotopes for reachability analysis while supporting exact intersections.

Computational Efficiency

Adaptive Sampling of Algal Blooms Using Autonomous Underwater Vehicle and Satellite Imagery: Experimental Validation in the Baltic Sea

1 code implementation1 May 2023 Joana Fonseca, Sriharsha Bhat, Matthew Lock, Ivan Stenius, Karl H. Johansson

The performance of this method is evaluated through realistic simulations for an algal bloom front in the Baltic sea, using the models of the AUV and the chlorophyll a sensor.

Secure Set-Based State Estimation for Linear Systems under Adversarial Attacks on Sensors

1 code implementation10 Sep 2023 Muhammad Umar B. Niazi, Michelle S. Chong, Amr Alanwar, Karl H. Johansson

When a strategic adversary can attack multiple sensors of a system and freely choose a different set of sensors at different times, how can we ensure that the state estimate remains uncorrupted by the attacker?

Formal Verification of Linear Temporal Logic Specifications Using Hybrid Zonotope-Based Reachability Analysis

1 code implementation4 Apr 2024 Loizos Hadjiloizou, Frank J. Jiang, Amr Alanwar, Karl H. Johansson

In this paper, we introduce a hybrid zonotope-based approach for formally verifying the behavior of autonomous systems operating under Linear Temporal Logic (LTL) specifications.

Distributed Online Convex Optimization with Time-Varying Coupled Inequality Constraints

no code implementations6 Mar 2019 Xinlei Yi, Xiuxian Li, Lihua Xie, Karl H. Johansson

Assuming Slater's condition, we show that the algorithm achieves smaller bounds on the constraint violation.

A Primal-Dual SGD Algorithm for Distributed Nonconvex Optimization

no code implementations4 Jun 2020 Xinlei Yi, Shengjun Zhang, Tao Yang, Tianyou Chai, Karl H. Johansson

The distributed nonconvex optimization problem of minimizing a global cost function formed by a sum of $n$ local cost functions by using local information exchange is considered.

Optimization and Control

How to Secure Distributed Filters Under Sensor Attacks

no code implementations11 Apr 2020 Xingkang He, Xiaoqiang Ren, Henrik Sandberg, Karl H. Johansson

The resilience of the secured filter with detection is verified by an explicit relationship between the upper bound of the estimation error and the number of detected attacked sensors.

Community Structure Recovery and Interaction Probability Estimation for Gossip Opinion Dynamics

no code implementations19 Feb 2021 Yu Xing, Xingkang He, Haitao Fang, Karl H. Johansson

The considered problem is to jointly recover the community labels of the agents and estimate interaction probabilities between the agents, based on a single trajectory of the model.

Community Detection

Stability Conditions for Remote State Estimation of Multiple Systems over Multiple Markov Fading Channels

no code implementations9 Apr 2021 Wanchun Liu, Daniel E. Quevedo, Karl H. Johansson, Branka Vucetic, Yonghui Li

We investigate the stability conditions for remote state estimation of multiple linear time-invariant (LTI) systems over multiple wireless time-varying communication channels.

Scheduling

Stochastic Stability of Discrete-time Phase-coupled Oscillators over Uncertain and Random Networks

no code implementations12 Apr 2021 Matin Jafarian, Mohammad H. Mamduhi, Karl H. Johansson

We assume constant exogenous frequencies and derive sufficient conditions for achieving both stochastic phase-cohesive and phase-locked solutions, i. e., stochastic phase-cohesiveness with respect to the origin.

Regret and Cumulative Constraint Violation Analysis for Distributed Online Constrained Convex Optimization

no code implementations1 May 2021 Xinlei Yi, Xiuxian Li, Tao Yang, Lihua Xie, Tianyou Chai, Karl H. Johansson

This is a sequential decision making problem with two sequences of arbitrarily varying convex loss and constraint functions.

Decision Making

Geometrical Characterization of Sensor Placement for Cone-Invariant and Multi-Agent Systems against Undetectable Zero-Dynamics Attacks

no code implementations10 May 2021 Jianqi Chen, Jieqiang Wei, Wei Chen, Henrik Sandberg, Karl H. Johansson, Jie Chen

Undetectable attacks are an important class of malicious attacks threatening the security of cyber-physical systems, which can modify a system's state but leave the system output measurements unaffected, and hence cannot be detected from the output.

A Model Randomization Approach to Statistical Parameter Privacy

no code implementations22 May 2021 Ehsan Nekouei, Henrik Sandberg, Mikael Skoglund, Karl H. Johansson

To ensure parameter privacy, we propose a filter design framework which consists of two components: a randomizer and a nonlinear transformation.

Regret and Cumulative Constraint Violation Analysis for Online Convex Optimization with Long Term Constraints

no code implementations9 Jun 2021 Xinlei Yi, Xiuxian Li, Tao Yang, Lihua Xie, Tianyou Chai, Karl H. Johansson

A novel algorithm is first proposed and it achieves an $\mathcal{O}(T^{\max\{c, 1-c\}})$ bound for static regret and an $\mathcal{O}(T^{(1-c)/2})$ bound for cumulative constraint violation, where $c\in(0, 1)$ is a user-defined trade-off parameter, and thus has improved performance compared with existing results.

Event-Triggered Distributed Estimation With Decaying Communication Rate

no code implementations10 Mar 2021 Xingkang He, Yu Xing, Junfeng Wu, Karl H. Johansson

We show that given the step size, adjusting the decay speed of the triggering threshold can lead to a tradeoff between the convergence rate of the estimation error and the decay speed of the communication rate.

Multi-Layer SIS Model with an Infrastructure Network

no code implementations20 Sep 2021 Philip E. Pare, Axel Janson, Sebin Gracy, Ji Liu, Henrik Sandberg, Karl H. Johansson

We develop a layered networked spread model for a susceptible-infected-susceptible (SIS) pathogen-borne disease spreading over a human contact network and an infrastructure network, and refer to it as a layered networked susceptible-infected-water-susceptible (SIWS) model.

Computing Complexity-aware Plans Using Kolmogorov Complexity

no code implementations21 Sep 2021 Elis Stefansson, Karl H. Johansson

We present two algorithms obtaining low-complexity policies, where the first algorithm obtains a low-complexity optimal policy, and the second algorithm finds a policy maximising performance while maintaining local (stage-wise) complexity constraints.

Distributed Optimal Allocation with Quantized Communication and Privacy-Preserving Guarantees

no code implementations29 Sep 2021 Jakob Nylöf, Apostolos I. Rikos, Sebin Gracy, Karl H. Johansson

It is shown that the proposed privacy-preserving resource allocation algorithm performs well with an appropriate convergence rate under privacy guarantees.

Privacy Preserving

Finite Time Exact Quantized Average Consensus with Limited Resources and Transmission Stopping for Energy-Aware Networks

no code implementations1 Oct 2021 Apostolos I. Rikos, Christoforos N. Hadjicostis, Karl H. Johansson

Motivated by these novel requirements, in this paper, we present and analyze a novel distributed average consensus algorithm, which (i) operates exclusively on quantized values (in order to guarantee efficient communication and data storage), and (ii) relies on event-driven updates (in order to reduce energy consumption, communication bandwidth, network congestion, and/or processor usage).

Autonomous Vehicles

Data-driven Set-based Estimation of Polynomial Systems with Application to SIR Epidemics

no code implementations8 Nov 2021 Amr Alanwar, Muhammad Umar B. Niazi, Karl H. Johansson

The offline phase utilizes past input-output data to estimate a set of possible coefficients of the polynomial system.

Truck Platoon Formation at Hubs: An Optimal Release Time Rule

no code implementations18 Feb 2022 Alexander Johansson, Valerio Turri, Ehsan Nekouei, Karl H. Johansson, Jonas Mårtensson

The vehicles wait at the hub, and a platoon coordinator, at each time-step, decides whether to release the vehicles from the hub in the form of a platoon or wait for more vehicles to arrive.

Finite Time Privacy Preserving Quantized Average Consensus with Transmission Stopping

no code implementations17 Jul 2022 Apostolos I. Rikos, Christoforos N. Hadjicostis, Karl H. Johansson

Furthermore, we present topological conditions under which the proposed algorithm allows nodes to preserve their privacy.

Privacy Preserving

Distributed Finite Time k-means Clustering with Quantized Communucation and Transmission Stopping

no code implementations17 Jul 2022 Apostolos I. Rikos, Gabriele Oliva, Christoforos N. Hadjicostis, Karl H. Johansson

The goal of $k$-means is to partition the network's agents in mutually exclusive sets (groups) such that agents in the same set have (and possibly share) similar information and are able to calculate a representative value for their group. During the operation of our distributed algorithm, each node (i) transmits quantized values in an event-driven fashion, and (ii) exhibits distributed stopping capabilities.

Clustering

A Sample-Based Algorithm for Approximately Testing $r$-Robustness of a Digraph

no code implementations25 Jul 2022 Yuhao Yi, YuAn Wang, Xingkang He, Stacy Patterson, Karl H. Johansson

In this paper, we propose a sample-based algorithm to approximately test $r$-robustness of a digraph with $n$ vertices and $m$ edges.

A Zeroth-Order Momentum Method for Risk-Averse Online Convex Games

no code implementations6 Sep 2022 Zifan Wang, Yi Shen, Zachary I. Bell, Scott Nivison, Michael M. Zavlanos, Karl H. Johansson

Specifically, the agents use the conditional value at risk (CVaR) as a risk measure and rely on bandit feedback in the form of the cost values of the selected actions at every episode to estimate their CVaR values and update their actions.

Secure State Estimation against Sparse Attacks on a Time-varying Set of Sensors

no code implementations10 Nov 2022 Zishuo Li, Muhammad Umar B. Niazi, Changxin Liu, Yilin Mo, Karl H. Johansson

At each time step, the local estimates of sensors are fused by solving an optimization problem to obtain a secure estimation, which is then followed by a local detection-and-resetting process of the decentralized observers.

Safe Reinforcement Learning using Data-Driven Predictive Control

no code implementations20 Nov 2022 Mahmoud Selim, Amr Alanwar, M. Watheq El-Kharashi, Hazem M. Abbas, Karl H. Johansson

If there is an intersection between the reachable set of the robot using the proposed action, we call the data-driven predictive controller to find the closest safe action to the proposed unsafe action.

Continuous Control Decision Making +3

Distributed Optimization with Quantized Gradient Descent

no code implementations20 Nov 2022 Apostolos I. Rikos, Wei Jiang, Themistoklis Charalambous, Karl H. Johansson

For solving this distributed optimization problem, we combine a gradient descent method with a distributed quantized consensus algorithm (which requires the nodes to exchange quantized messages and converges in a finite number of steps).

Distributed Optimization

Distributed Computation of Exact Average Degree and Network Size in Finite Number of Steps under Quantized Communication

no code implementations29 Nov 2022 Apostolos I. Rikos, Themistoklis Charalambous, Christoforos N. Hadjicostis, Karl H. Johansson

We present two distributed algorithms which rely on quantized operation (i. e., nodes process and transmit quantized messages), and are able to calculate the exact solutions in a finite number of steps.

Quantization

Rollout-Based Charging Strategy for Electric Trucks with Hours-of-Service Regulations (Extended Version)

no code implementations15 Mar 2023 Ting Bai, Yuchao Li, Karl H. Johansson, Jonas Mårtensson

We assume that a collection of charging and rest stations is given along a pre-planned route with known detours and that the problem data are deterministic.

Online Control Synthesis for Uncertain Systems under Signal Temporal Logic Specifications

no code implementations16 Mar 2021 Pian Yu, Yulong Gao, Frank J. Jiang, Karl H. Johansson, Dimos V. Dimarogonas

It is shown that when the STL formula is robustly satisfiable and the initial state of the system belongs to the initial root node of the tTLT, it is guaranteed that the trajectory generated by the control synthesis algorithm satisfies the STL formula.

Policy Evaluation in Distributional LQR

no code implementations23 Mar 2023 Zifan Wang, Yulong Gao, Siyi Wang, Michael M. Zavlanos, Alessandro Abate, Karl H. Johansson

Distributional reinforcement learning (DRL) enhances the understanding of the effects of the randomness in the environment by letting agents learn the distribution of a random return, rather than its expected value as in standard RL.

Distributional Reinforcement Learning

Learning Flow Functions from Data with Applications to Nonlinear Oscillators

no code implementations29 Mar 2023 Miguel Aguiar, Amritam Das, Karl H. Johansson

We show that the proposed architecture is able to approximate the flow function by exploiting the system's causality and time-invariance.

Efficient and Reconfigurable Optimal Planning in Large-Scale Systems Using Hierarchical Finite State Machines

no code implementations29 Mar 2023 Elis Stefansson, Karl H. Johansson

In this paper, we consider a planning problem for a large-scale system modelled as a hierarchical finite state machine (HFSM) and develop a control algorithm for computing optimal plans between any two states.

Secure State Estimation with Asynchronous Measurements against Malicious Measurement-data and Time-stamp Manipulation

no code implementations30 Mar 2023 Zishuo Li, Anh Tung Nguyen, André Teixeira, Yilin Mo, Karl H. Johansson

To deal with such attacks, we propose the design of local estimators based on observability space decomposition, where each local estimator updates the local state and sends it to the fusion center after sampling a measurement.

Blocking

Distributed Optimization for Quadratic Cost Functions over Large-Scale Networks with Quantized Communication and Finite-Time Convergence

no code implementations2 Apr 2023 Apostolos I. Rikos, Andreas Grammenos, Evangelia Kalyvianaki, Christoforos N. Hadjicostis, Themistoklis Charalambous, Karl H. Johansson

We prove that our algorithms converge in a finite number of iterations to the exact optimal solution depending on the quantization level, and we present applications of our algorithms to (i) optimal task scheduling for data centers, and (ii) global model aggregation for distributed federated learning.

Distributed Optimization Federated Learning +2

Universal approximation of flows of control systems by recurrent neural networks

no code implementations1 Apr 2023 Miguel Aguiar, Amritam Das, Karl H. Johansson

In this paper, we prove that an architecture based on discrete-time recurrent neural networks universally approximates flows of continuous-time dynamical systems with inputs.

Parameterization-Free Observer Design for Nonlinear Systems: Application to the State Estimation of Networked SIR Epidemics

no code implementations7 Apr 2023 Muhammad Umar B. Niazi, Karl H. Johansson

In this paper, we present an observer design approach for estimating the state of nonlinear systems, without requiring any parameterization of the system's nonlinearities.

Complexity reduction for resilient state estimation of uniformly observable nonlinear systems

no code implementations18 Apr 2023 Junsoo Kim, Jin Gyu Lee, Henrik Sandberg, Karl H. Johansson

As a result, although a portion of measurements are compromised, they can be locally identified and excluded from the state estimation, and thus the true state can be recovered.

What is the Expected Transient Behavior of Opinion Evolution for Two Communities?

no code implementations24 Apr 2023 Yu Xing, Karl H. Johansson

Moreover, it is shown that the expected states of the agents in the same community concentrate around the initial average opinion of that community, if the weights within communities are larger than between.

Distributed Online Convex Optimization with Adversarial Constraints: Reduced Cumulative Constraint Violation Bounds under Slater's Condition

no code implementations31 May 2023 Xinlei Yi, Xiuxian Li, Tao Yang, Lihua Xie, Yiguang Hong, Tianyou Chai, Karl H. Johansson

Moreover, if the loss functions are strongly convex, then the network regret bound is reduced to $\mathcal{O}(\log(T))$, and the network cumulative constraint violation bound is reduced to $\mathcal{O}(\sqrt{\log(T)T})$ and $\mathcal{O}(\log(T))$ without and with Slater's condition, respectively.

Joint Learning of Network Topology and Opinion Dynamics Based on Bandit Algorithms

no code implementations25 Jun 2023 Yu Xing, Xudong Sun, Karl H. Johansson

We study joint learning of network topology and a mixed opinion dynamics, in which agents may have different update rules.

regression

Online Distributed Learning with Quantized Finite-Time Coordination

no code implementations13 Jul 2023 Nicola Bastianello, Apostolos I. Rikos, Karl H. Johansson

Online distributed learning refers to the process of training learning models on distributed data sources.

Federated Learning

Data-Driven Reachability Analysis of Pedestrians Using Behavior Modes

no code implementations21 Aug 2023 August Söderlund, Frank J. Jiang, Vandana Narri, Amr Alanwar, Karl H. Johansson

Previous approaches to predicting the future state sets of pedestrians either do not provide safety guarantees or are overly conservative.

Descriptive

Online Distributed Learning over Random Networks

no code implementations1 Sep 2023 Nicola Bastianello, Diego Deplano, Mauro Franceschelli, Karl H. Johansson

The recent deployment of multi-agent systems in a wide range of scenarios has enabled the solution of learning problems in a distributed fashion.

Distributed Optimization via Gradient Descent with Event-Triggered Zooming over Quantized Communication

no code implementations8 Sep 2023 Apostolos I. Rikos, Wei Jiang, Themistoklis Charalambous, Karl H. Johansson

Distributed methods in which nodes use quantized communication yield a solution at the proximity of the optimal solution, hence reaching an error floor that depends on the quantization level used; the finer the quantization the lower the error floor.

Distributed Optimization Quantization

Gain and Phase: Decentralized Stability Conditions for Power Electronics-Dominated Power Systems

no code implementations14 Sep 2023 Linbin Huang, Dan Wang, Xiongfei Wang, Huanhai Xin, Ping Ju, Karl H. Johansson, Florian Dörfler

This paper proposes decentralized stability conditions for multi-converter systems based on the combination of the small gain theorem and the small phase theorem.

Optimal Privacy-Aware Dynamic Estimation

no code implementations10 Nov 2023 Chuanghong Weng, Ehsan Nekouei, Karl H. Johansson

In our setup, a private process, modeled as a first-order Markov chain, derives the states of the system, and the state estimates are shared with an untrusted party who might attempt to infer the private process based on the state estimates.

Almost Exact Recovery in Gossip Opinion Dynamics over Stochastic Block Models

no code implementations5 Dec 2023 Yu Xing, Karl H. Johansson

It is shown that, when the influence of stubborn agents is small and the link probability within communities is large, an algorithm based on clustering transient agent states can achieve almost exact recovery of the communities.

Clustering Community Detection

Learning flow functions of spiking systems

no code implementations19 Dec 2023 Miguel Aguiar, Amritam Das, Karl H. Johansson

We propose a framework for surrogate modelling of spiking systems.

Survey of Distributed Algorithms for Resource Allocation over Multi-Agent Systems

no code implementations28 Jan 2024 Mohammadreza Doostmohammadian, Alireza Aghasi, Mohammad Pirani, Ehsan Nekouei, Houman Zarrabi, Reza Keypour, Apostolos I. Rikos, Karl H. Johansson

This survey paper provides a comprehensive analysis of distributed algorithms for addressing the distributed resource allocation (DRA) problem over multi-agent systems.

Distributed Optimization Scheduling

MaxCUCL: Max-Consensus with Deterministic Convergence in Networks with Unreliable Communication

no code implementations28 Feb 2024 Apostolos I. Rikos, Themistoklis Charalambous, Karl H. Johansson

Our proposed algorithm is the first algorithm that achieves max-consensus in a deterministic manner (i. e., nodes always calculate the maximum of their states regardless of the nature of the probability distribution of the packet drops).

Enhancing Privacy in Federated Learning through Local Training

no code implementations26 Mar 2024 Nicola Bastianello, Changxin Liu, Karl H. Johansson

In this paper we propose the federated private local training algorithm (Fed-PLT) for federated learning, to overcome the challenges of (i) expensive communications and (ii) privacy preservation.

Federated Learning

Risk-averse Learning with Non-Stationary Distributions

no code implementations3 Apr 2024 Siyi Wang, Zifan Wang, Xinlei Yi, Michael M. Zavlanos, Karl H. Johansson, Sandra Hirche

Considering non-stationary environments in online optimization enables decision-maker to effectively adapt to changes and improve its performance over time.

Guaranteed Completion of Complex Tasks via Temporal Logic Trees and Hamilton-Jacobi Reachability

no code implementations12 Apr 2024 Frank J. Jiang, Kaj Munhoz Arfvidsson, Chong He, Mo Chen, Karl H. Johansson

By ensuring a temporal logic tree has no leaking corners, we know the temporal logic tree correctly verifies the existence of control policies that satisfy the specified task.

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