Search Results for author: Andrew Clark

Found 18 papers, 2 papers with code

Fault Tolerant Neural Control Barrier Functions for Robotic Systems under Sensor Faults and Attacks

1 code implementation28 Feb 2024 Hongchao Zhang, Luyao Niu, Andrew Clark, Radha Poovendran

Control barrier function (CBF)-based approaches have been proposed to guarantee the safety of robotic systems.

Neural Lyapunov Control for Discrete-Time Systems

1 code implementation NeurIPS 2023 Junlin Wu, Andrew Clark, Yiannis Kantaros, Yevgeniy Vorobeychik

However, finding Lyapunov functions for general nonlinear systems is a challenging task.

Pre-processing training data improves accuracy and generalisability of convolutional neural network based landscape semantic segmentation

no code implementations28 Apr 2023 Andrew Clark, Stuart Phinn, Peter Scarth

Our results showed: a stratified random sampling approach for producing training patches improved the accuracy of classes with a smaller area while having minimal effect on larger classes; a smaller number of larger patches compared to a larger number of smaller patches improves model accuracy; applying data augmentations and scaling are imperative in creating a generalised model able to accurately classify LULC features in imagery from a different date and sensor; and producing the output classification by averaging multiple grids of patches and three rotated versions of each patch produced and more accurate and aesthetic result.

Earth Observation Semantic Segmentation

Risk-Aware Distributed Multi-Agent Reinforcement Learning

no code implementations4 Apr 2023 Abdullah Al Maruf, Luyao Niu, Bhaskar Ramasubramanian, Andrew Clark, Radha Poovendran

We then propose a distributed MARL algorithm called the CVaR QD-Learning algorithm, and establish that value functions of individual agents reaches consensus.

Decision Making Multi-agent Reinforcement Learning +1

Cooperative Perception for Safe Control of Autonomous Vehicles under LiDAR Spoofing Attacks

no code implementations14 Feb 2023 Hongchao Zhang, Zhouchi Li, Shiyu Cheng, Andrew Clark

In this paper, we propose an approach to detect and mitigate LiDAR spoofing attacks by leveraging LiDAR scan data from other neighboring vehicles.

Autonomous Vehicles Fault Detection

A Semi-Algebraic Framework for Verification and Synthesis of Control Barrier Functions

no code implementations31 Aug 2022 Andrew Clark

Based on these conditions, we propose a framework for verifying safety of CBF-based control including single CBFs, high-order CBFs, multi-CBFs, and systems with trigonometric dynamics and actuation constraints.

Abstraction-Free Control Synthesis to Satisfy Temporal Logic Constraints under Sensor Faults and Attacks

no code implementations22 Aug 2022 Luyao Niu, Zhouchi Li, Andrew Clark

We develop a class of fault-tolerant finite time convergence control barrier functions (CBFs) to guarantee that a dynamical system reaches a set within finite time almost surely in the presence of malicious attacks.

Barrier Certificate based Safe Control for LiDAR-based Systems under Sensor Faults and Attacks

no code implementations11 Aug 2022 Hongchao Zhang, Shiyu Cheng, Luyao Niu, Andrew Clark

We prove that the synthesized control input guarantees system safety using control barrier certificates.

Safety-Critical Control Synthesis for Unknown Sampled-Data Systems via Control Barrier Functions

no code implementations28 Sep 2021 Luyao Niu, Hongchao Zhang, Andrew Clark

By satisfying the constructed CBF constraint at each sampling time, we guarantee the unknown sampled-data system is safe for all time.

A Game-Theoretic Framework for Controlled Islanding in the Presence of Adversaries

no code implementations3 Aug 2021 Luyao Niu, Dinuka Sahabandu, Andrew Clark, Radha Poovendran

In this paper, we study the controlled islanding problem of a power system under disturbances introduced by a malicious adversary.

Verification and Synthesis of Control Barrier Functions

no code implementations28 Apr 2021 Andrew Clark

Our approach is to show that safety of CBFs is equivalent to the non-existence of solutions to a family of polynomial equations, and then prove that this nonexistence is equivalent to a pair of sum-of-squares constraints via the Positivstellensatz of algebraic geometry.

Reinforcement Learning Beyond Expectation

no code implementations29 Mar 2021 Bhaskar Ramasubramanian, Luyao Niu, Andrew Clark, Radha Poovendran

In this paper, we consider a setting where an autonomous agent has to learn behaviors in an unknown environment.

reinforcement-learning Reinforcement Learning (RL)

LQG Reference Tracking with Safety and Reachability Guarantees under Unknown False Data Injection Attacks

no code implementations28 Feb 2021 Zhouchi Li, Luyao Niu, Andrew Clark

For each possible set of compromised sensors, we maintain a state estimator disregarding the sensors in that set, and calculate the optimal LQG control input at each time based on this estimate.

Potential-Based Advice for Stochastic Policy Learning

no code implementations20 Jul 2019 Baicen Xiao, Bhaskar Ramasubramanian, Andrew Clark, Hannaneh Hajishirzi, Linda Bushnell, Radha Poovendran

This paper augments the reward received by a reinforcement learning agent with potential functions in order to help the agent learn (possibly stochastic) optimal policies.

Q-Learning

Group theory, group actions, evolutionary algorithms, and global optimization

no code implementations27 Dec 2012 Andrew Clark

In this paper we use group, action and orbit to understand how evolutionary solve nonconvex optimization problems.

Evolutionary Algorithms

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