Exponential Control Barrier Functions for enforcing high relative-degree safety-critical constraints

Nguyen, Quan; Sreenath, Koushil

doi:10.1109/acc.2016.7524935

Cited by 365 publications

(375 citation statements)

References 19 publications

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“…However, these barrier certificates are often overly restrictive by requiring the barrier function to always descend. A more permissive control barrier function was proposed in [14], [18], and [19] with correctness guarantees. In particular, in this paper, we use this type of more permissive control barrier functions to synthesize safety certificates-these provide the minimum modification necessary to formally guarantee safety.…”

Section: Introductionmentioning

confidence: 99%

Safety Barrier Certificates for Collisions-Free Multirobot Systems

2017

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Abstract-This paper presents safety barrier certificates that ensure scalable and provably collision-free behaviors in multirobot systems by modifying the nominal controllers to formally satisfy safety constraints. This is achieved by minimizing the difference between the actual and the nominal controllers subject to safety constraints. The resulting computation of the safety controllers is done through a quadratic programming problem that can be solved in real-time and in this paper, we describe a series of problems of increasing complexity. Starting with a centralized formulation, where the safety controller is computed across all agents simultaneously, we show how one can achieve a natural decentralization whereby individual robots only have to remain safe relative to nearby robots. Conservativeness and existence of solutions as well as deadlockavoidance are then addressed using a mixture of relaxed control barrier functions, hybrid braking controllers, and consistent perturbations. The resulting control strategy is verified experimentally on a collection of wheeled mobile robots whose nominal controllers are explicitly designed to make the robots collide.

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Section: Introductionmentioning

confidence: 99%

Safety Barrier Certificates for Collisions-Free Multirobot Systems

2017

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“…In this section we provide a brief introduction to CBFs, and refer the reader to [14], [15], [20], [21] for complete details. CBFs can be applied to continuous time affine control systems of the form:…”

Section: A Control Barrier Function Implementationmentioning

confidence: 99%

“…However, the velocity and acceleration with which the robot approaches the restricted region should matter because a fast approach towards the object is less safe than a slow approach. Nguyen and Sreenath and Xiao and Belta developed methods to include higherorder derivatives of the barrier function in the safety constraint while guaranteeing safety [20], [21]. Following these methods, in this paper we implement safety constraints of the form:…”

Section: A Control Barrier Function Implementationmentioning

confidence: 99%

Haptic Teleoperation of UAVs Through Control Barrier Functions

Zhang

Yang

Khurshid

2020

IEEE Trans. Haptics

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This paper presents a novel approach to haptic teleoperation. Specifically, we use control barrier functions (CBFs) to generate force feedback to help human operators safely fly quadrotor UAVs. CBFs take a control signal as input and output a control signal that is as close as possible to the initial control signal, while also meeting specified safety constraints. In the proposed method, we generate haptic force feedback based on the difference between a command issued by the human operator and the safe command returned by a CBF. In this way, if the user issues an unsafe control command, the haptic feedback will help guide the user towards the safe input command that is closest to their current command. We conducted a within-subject user study, in which 12 participants flew a simulated UAV in a virtual hallway environment. Participants completed the task with our proposed CBFbased haptic feedback, no haptic feedback, and haptic feedback generated via parametric risk fields, which is a state-of-the-art method described in the literature. The results of this study show that CBF-based haptic feedback can improve a human operator's ability to safely fly a UAV and reduce the operator's perceived workload, without sacrificing task efficiency.

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“…Extensions to incorporate signal temporal logic constraints were developed in [13]. A framework for exponential CBFs that enable safety guarantees in high relative-degree systems was proposed in [16]. While the present paper also considers high relative-degree systems, we propose a different approach and, moreover, consider the problem in a stochastic setting.…”

Section: Related Workmentioning

confidence: 99%

Control Barrier Functions for Complete and Incomplete Information Stochastic Systems

Clark

2019

2019 American Control Conference (ACC)

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Control Barrier Functions (CBFs) aim to ensure safety by constraining the control input at each time step so that the system state remains within a desired safe region. This paper presents a framework for CBFs in stochastic systems in the presence of Gaussian process and measurement noise. We first consider the case where the system state is known at each time step, and present reciprocal and zero CBF constructions that guarantee safety with probability 1. We extend our results to high relative degree systems with linear dynamics and affine safety constraints. We then develop CBFs for incomplete state information environments, in which the state must be estimated using sensors that are corrupted by Gaussian noise. We prove that our proposed CBF ensures safety with probability 1 when the state estimate is within a given bound of the true state, which can be achieved using an Extended Kalman Filter when the system is linear or the process and measurement noise are sufficiently small. We propose control policies that combine these CBFs with Control Lyapunov Functions in order to jointly ensure safety and stochastic stability. Our results are validated via numerical study on an adaptive cruise control example.

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Exponential Control Barrier Functions for enforcing high relative-degree safety-critical constraints

Cited by 365 publications

References 19 publications

Safety Barrier Certificates for Collisions-Free Multirobot Systems

Safety Barrier Certificates for Collisions-Free Multirobot Systems

Haptic Teleoperation of UAVs Through Control Barrier Functions

Control Barrier Functions for Complete and Incomplete Information Stochastic Systems

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