Search Results for author: Christos G. Cassandras

Found 35 papers, 8 papers with code

Reinforcement Learning-based Receding Horizon Control using Adaptive Control Barrier Functions for Safety-Critical Systems

1 code implementation26 Mar 2024 Ehsan Sabouni, H. M. Sabbir Ahmad, Vittorio Giammarino, Christos G. Cassandras, Ioannis Ch. Paschalidis, Wenchao Li

Unfortunately, both performance and solution feasibility can be significantly impacted by two key factors: (i) the selection of the cost function and associated parameters, and (ii) the calibration of parameters within the CBF-based constraints, which capture the trade-off between performance and conservativeness.

Bilevel Optimization Model Predictive Control +1

Spline Trajectory Tracking and Obstacle Avoidance for Mobile Agents via Convex Optimization

no code implementations25 Mar 2024 Akua Dickson, Christos G. Cassandras, Roberto Tron

We propose an output feedback control-based motion planning technique for agents to enable them to converge to a specified polynomial trajectory while imposing a set of safety constraints on our controller to avoid collisions within the free configuration space (polygonal environment).

Motion Planning

Performance-Guaranteed Solutions for Multi-Agent Optimal Coverage Problems using Submodularity, Curvature, and Greedy Algorithms

no code implementations20 Mar 2024 Shirantha Welikala, Christos G. Cassandras

We consider a class of multi-agent optimal coverage problems in which the goal is to determine the optimal placement of a group of agents in a given mission space so that they maximize a coverage objective that represents a blend of individual and collaborative event detection capabilities.

Event Detection

Optimal Sequencing and Motion Control in a Roundabout with Safety Guarantees

no code implementations14 Mar 2024 Yingqing Chen, Christos G. Cassandras, Kaiyuan Xu

This paper develops a controller for Connected and Automated Vehicles (CAVs) traversing a single-lane roundabout.

Model Predictive Control

Secure Control of Connected and Automated Vehicles Using Trust-Aware Robust Event-Triggered Control Barrier Functions

1 code implementation4 Jan 2024 H M Sabbir Ahmad, Ehsan Sabouni, Akua Dickson, Wei Xiao, Christos G. Cassandras, Wenchao Li

We address the security of a network of Connected and Automated Vehicles (CAVs) cooperating to safely navigate through a conflict area (e. g., traffic intersections, merging roadways, roundabouts).

Navigate

Safe Optimal Interactions Between Automated and Human-Driven Vehicles in Mixed Traffic with Event-triggered Control Barrier Functions

no code implementations1 Oct 2023 Anni Li, Christos G. Cassandras, Wei Xiao

This paper studies safe driving interactions between Human-Driven Vehicles (HDVs) and Connected and Automated Vehicles (CAVs) in mixed traffic where the dynamics and control policies of HDVs are unknown and hard to predict.

Scaling up the Optimal Safe Control of Connected and Automated Vehicles to a Traffic Network: A Hierarchical Framework of Modular Control Zones

no code implementations6 Aug 2023 Kaiyuan Xu, Christos G. Cassandras

We consider the problem of scaling up optimal and safe controllers for Connected and Automated Vehicles (CAVs) from a single Control Zone (CZ) around a traffic conflict area to an entire network.

Maximizing Safety and Efficiency for Cooperative Lane-Changing: A Minimally Disruptive Approach

1 code implementation29 May 2023 Andres S. Chavez Armijos, Anni Li, Christos G. Cassandras

This paper addresses cooperative lane-changing maneuvers in mixed traffic, aiming to minimize traffic flow disruptions while accounting for uncooperative vehicles.

Merging control in mixed traffic with safety guarantees: a safe sequencing policy with optimal motion control

no code implementations26 May 2023 Ehsan Sabouni, H. M. Sabbir Ahmad, Christos G. Cassandras, Wenchao Li

We address the problem of merging traffic from two roadways consisting of both Connected Autonomous Vehicles (CAVs) and Human Driven Vehicles (HDVs).

Autonomous Vehicles

Trust-Aware Resilient Control and Coordination of Connected and Automated Vehicles

1 code implementation26 May 2023 H M Sabbir Ahmad, Ehsan Sabouni, Wei Xiao, Christos G. Cassandras, Wenchao Li

We address the security of a network of Connected and Automated Vehicles (CAVs) cooperating to navigate through a conflict area.

Navigate

Scalable Adaptive Traffic Light Control Over a Traffic Network Including Transit Delays

no code implementations15 May 2023 Yingqing Chen, Christos G. Cassandras

We study the Traffic Light Control (TLC) problem for a traffic network with multiple intersections in an artery, including the effect of transit delays for vehicles moving from one intersection to the next.

Cooperative Lane Changing in Mixed Traffic can be Robust to Human Driver Behavior

no code implementations29 Mar 2023 Anni Li, Andres S. Chavez Armijos, Christos G. Cassandras

We derive time and energy-optimal control policies for a Connected Autonomous Vehicle (CAV) to complete lane change maneuvers in mixed traffic.

Bilevel Optimization

Adaptive Traffic Light Control for Competing Vehicle and Pedestrian Flows

no code implementations14 Mar 2023 Yingqing Chen, Christos G. Cassandras

We study the Traffic Light Control (TLC) problem for a single intersection, considering both straight driving vehicle flows and corresponding crossing pedestrian flows with the goal of achieving a fair jointly optimal sharing policy in terms of average waiting times.

Learning Feasibility Constraints for Control Barrier Functions

no code implementations10 Mar 2023 Wei Xiao, Christos G. Cassandras, Calin A. Belta

It has been shown that optimizing quadratic costs while stabilizing affine control systems to desired (sets of) states subject to state and control constraints can be reduced to a sequence of Quadratic Programs (QPs) by using Control Barrier Functions (CBFs) and Control Lyapunov Functions (CLFs).

Autonomous Driving

Optimal Merging Control of an Autonomous Vehicle in Mixed Traffic: an Optimal Index Policy

no code implementations7 Nov 2022 Ehsan Sabouni, Christos G. Cassandras

We derive an optimal index policy which prescribes the merging position of the AV within the group of HDVs.

Optimal Control of Connected Automated Vehicles with Event/Self-Triggered Control Barrier Functions

no code implementations26 Sep 2022 Ehsan Sabouni, Christos G. Cassandras, Wei Xiao, Nader Meskin

We address the problem of controlling Connected and Automated Vehicles (CAVs) in conflict areas of a traffic network subject to hard safety constraints.

Generalized Policy Improvement Algorithms with Theoretically Supported Sample Reuse

2 code implementations28 Jun 2022 James Queeney, Ioannis Ch. Paschalidis, Christos G. Cassandras

Data-driven, learning-based control methods offer the potential to improve operations in complex systems, and model-free deep reinforcement learning represents a popular approach to data-driven control.

Continuous Control Decision Making

Sequential Cooperative Energy and Time-Optimal Lane Change Maneuvers for Highway Traffic

no code implementations31 Mar 2022 Andres S. Chavez Armijos, Rui Chen, Christos G. Cassandras, Yasir K. Al-Nadawi, Hossein Noukhiz Mahjoub, Hidekazu Araki

We derive optimal control policies for a Connected Automated Vehicle (CAV) and cooperating neighboring CAVs to carry out a lane change maneuver consisting of a longitudinal phase where the CAV properly positions itself relative to the cooperating neighbors and a lateral phase where it safely changes lanes.

Self-Triggered Coordination Control of Connected Automated Vehicles in Traffic Networks

no code implementations24 Mar 2022 Nader Meskin, Ehsan Sabouni, Wei Xiao, Christos G. Cassandras

The safety constraints and the vehicle limitations are considered using the Control Barrier Function (CBF) framework and a self-triggered scheme is proposed using the CBF constraints.

Optimal Control of Connected Automated Vehicles with Event-Triggered Control Barrier Functions

no code implementations22 Mar 2022 Ehsan Sabouni, Christos G. Cassandras, Wei Xiao, Nader Meskin

We address the problem of controlling Connected and Automated Vehicles (CAVs) in conflict areas of a traffic network subject to hard safety constraints.

Feasibility Guaranteed Traffic Merging Control Using Control Barrier Functions

no code implementations8 Mar 2022 Kaiyuan Xu, Wei Xiao, Christos G. Cassandras

We consider the merging control problem for Connected and Automated Vehicles (CAVs) aiming to jointly minimize travel time and energy consumption while providing speed-dependent safety guarantees and satisfying velocity and acceleration constraints.

Minimax Multi-Agent Persistent Monitoring of a Network System

no code implementations17 Jan 2022 Samuel C. Pinto, Shirantha Welikala, Sean B. Andersson, Julien M. Hendrickx, Christos G. Cassandras

For a given visiting sequence, we prove that in an optimal dwelling time allocation the peak uncertainty is the same among all the targets.

Traveling Salesman Problem

Generalized Proximal Policy Optimization with Sample Reuse

1 code implementation NeurIPS 2021 James Queeney, Ioannis Ch. Paschalidis, Christos G. Cassandras

In real-world decision making tasks, it is critical for data-driven reinforcement learning methods to be both stable and sample efficient.

Decision Making

Decentralized Time and Energy-Optimal Control of Connected and Automated Vehicles in a Roundabout

no code implementations13 Apr 2021 Kaiyuan Xu, Christos G. Cassandras, Wei Xiao

The paper considers the problem of controlling Connected and Automated Vehicles (CAVs) traveling through a three-entry roundabout so as to jointly minimize both the travel time and the energy consumption while providing speed-dependent safety guarantees, as well as satisfying velocity and acceleration constraints.

A Semidefinite Programming Approach to Discrete-time Infinite Horizon Persistent Monitoring

no code implementations1 Apr 2021 Samuel C. Pinto, Sean B. Andersson, Julien M. Hendrickx, Christos G. Cassandras

We investigate the problem of persistent monitoring, where a mobile agent has to survey multiple targets in an environment in order to estimate their internal states.

Event-Triggered Safety-Critical Control for Systems with Unknown Dynamics

no code implementations29 Mar 2021 Wei Xiao, Calin Belta, Christos G. Cassandras

We define a HOCBF for a safety requirement on the unmodelled system based on the adaptive dynamics and error states, and reformulate the safety-critical control problem as the above mentioned QP.

Event-Driven Receding Horizon Control of Energy-Aware Dynamic Agents For Distributed Persistent Monitoring

no code implementations25 Feb 2021 Shirantha Welikala, Christos G. Cassandras

This paper addresses the persistent monitoring problem defined on a network where a set of nodes (targets) needs to be monitored by a team of dynamic energy-aware agents.

Uncertainty-Aware Policy Optimization: A Robust, Adaptive Trust Region Approach

no code implementations19 Dec 2020 James Queeney, Ioannis Ch. Paschalidis, Christos G. Cassandras

In order for reinforcement learning techniques to be useful in real-world decision making processes, they must be able to produce robust performance from limited data.

Decision Making

Event-Driven Receding Horizon Control for Distributed Estimation in Network Systems

no code implementations24 Sep 2020 Shirantha Welikala, Christos G. Cassandras

We consider the problem of estimating the states of a distributed network of nodes (targets) through a team of cooperating agents (sensors) persistently visiting the nodes so that an overall measure of estimation error covariance evaluated over a finite period is minimized.

Computational Efficiency

Feasibility-Guided Learning for Robust Control in Constrained Optimal Control Problems

no code implementations6 Dec 2019 Wei Xiao, Calin A. Belta, Christos G. Cassandras

In this paper, we further improve the feasibility robustness (i. e., feasibility maintenance in the presence of time-varying and unknown unsafe sets) through the definition of a High Order CBF (HOCBF) that works for arbitrary relative degree constraints; this is achieved by a proposed feasibility-guided learning approach.

Data-driven Estimation of Origin-Destination Demand and User Cost Functions for the Optimization of Transportation Networks

2 code implementations29 Oct 2016 Jing Zhang, Sepideh Pourazarm, Christos G. Cassandras, Ioannis Ch. Paschalidis

In earlier work (Zhang et al., 2016) we used actual traffic data from the Eastern Massachusetts transportation network in the form of spatial average speeds and road segment flow capacities in order to estimate Origin-Destination (OD) flow demand matrices for the network.

Systems and Control 90B06

Optimal control for a robotic exploration, pick-up and delivery problem

no code implementations5 Jul 2016 Vladislav Nenchev, Christos G. Cassandras, Jörg Raisch

This paper addresses an optimal control problem for a robot that has to find and collect a finite number of objects and move them to a depot in minimum time.

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