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Falsification of LTL Safety Properties in Hybrid Systems
"... This paper develops a novel computational method for the falsification of safety properties specified by syntactically safe linear temporal logic (LTL) formulas φ for hybrid systems with general nonlinear dynamics and input controls. The method is based on an effective combination of robot motion p ..."
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Cited by 21 (6 self)
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This paper develops a novel computational method for the falsification of safety properties specified by syntactically safe linear temporal logic (LTL) formulas φ for hybrid systems with general nonlinear dynamics and input controls. The method is based on an effective combination of robot motion planning and model checking. Experiments on a hybrid robotic system benchmark with nonlinear dynamics show significant speedup over related work. The experiments also indicate significant speedup when using minimized DFA instead of nonminimized NFA, as obtained by standard tools, for representing the violating prefixes of φ.
Controlling wild bodies using linear temporal logic
 In Proceedings Robotics: Science and Systems
, 2011
"... Fig. 1. a) Our vehicle of study is a $4 weasel ball; b) it consists entirely of a battery and slowly oscillating motor mounted to a plastic shell. Abstract—There is substantial interest controlling a group of bodies from specifications of tasks given in a highlevel, humanlike language. This paper p ..."
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Cited by 21 (4 self)
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Fig. 1. a) Our vehicle of study is a $4 weasel ball; b) it consists entirely of a battery and slowly oscillating motor mounted to a plastic shell. Abstract—There is substantial interest controlling a group of bodies from specifications of tasks given in a highlevel, humanlike language. This paper proposes a methodology that creates lowlevel hybrid controllers that guarantee that a group of bodies execute a highlevel specified task without dynamical system modeling, precise state estimation or state feedback. We do this by exploiting the wild motions of very simple bodies in an environment connected by gates which serve as the system inputs, as opposed motors on the bodies. We present experiments using inexpensive hardware demonstrating the practical feasibility of our approach to solving tasks such as navigation, patrolling, and coverage. I.
Probabilistic Analysis of Correctness of HighLevel Robot Behavior with Sensor Error
"... Abstract—This paper presents a method for reasoning about the effects of sensor error on highlevel robot behavior. We consider robot controllers that are synthesized from a set of highlevel, temporal logic task specifications, such that the resulting robot behavior is guaranteed to satisfy these sp ..."
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Cited by 16 (1 self)
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Abstract—This paper presents a method for reasoning about the effects of sensor error on highlevel robot behavior. We consider robot controllers that are synthesized from a set of highlevel, temporal logic task specifications, such that the resulting robot behavior is guaranteed to satisfy these specifications when assuming perfect sensors and actuators. We relax the assumption of perfect sensing, and calculate the probability with which the controller satisfies a set of temporal logic specifications. We consider parametric representations, where the satisfaction probability is found as a function of the model parameters, and numerical representations, allowing for the analysis of large examples. We illustrate our approach with three examples of varying size that provide insight into unintuitive effects of sensor error that can inform the specification design process. I.
Iterative Temporal Motion Planning for Hybrid Systems in Partially Unknown Environments
"... This paper considers the problem of motion planning for a hybrid robotic system with complex and nonlinear dynamics in a partially unknown environment given a temporal logic specification. We employ a multilayered synergistic framework that can deal with general robot dynamics and combine it with a ..."
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Cited by 13 (4 self)
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This paper considers the problem of motion planning for a hybrid robotic system with complex and nonlinear dynamics in a partially unknown environment given a temporal logic specification. We employ a multilayered synergistic framework that can deal with general robot dynamics and combine it with an iterative planning strategy. Our work allows us to deal with the unknown environmental restrictions only when they are discovered and without the need to repeat the computation that is related to the temporal logic specification. In addition, we define a metric for satisfaction of a specification. We use this metric to plan a trajectory that satisfies the specification as closely as possible in cases in which the discovered constraint in the environment renders the specification unsatisfiable. We demonstrate the efficacy of our framework on a simulation of a hybrid secondorder carlike robot moving in an office environment with unknown obstacles. The results show that our framework is successful in generating a trajectory whose satisfaction measure of the specification is optimal. They also show that, when new obstacles are discovered, the reinitialization of our framework is computationally inexpensive.
PartialObservation Stochastic Games: How to Win when Belief Fails
, 2011
"... Abstract. In twoplayer finitestate stochastic games of partial observation on graphs, in every state of the graph, the players simultaneously choose an action, and their joint actions determine a probability distribution over the successor states. The game is played for infinitely many rounds and ..."
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Cited by 12 (6 self)
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Abstract. In twoplayer finitestate stochastic games of partial observation on graphs, in every state of the graph, the players simultaneously choose an action, and their joint actions determine a probability distribution over the successor states. The game is played for infinitely many rounds and thus the players construct an infinite path in the graph. We consider reachability objectives where the first player tries to ensure a target state to be visited almostsurely (i.e., with probability 1) or positively (i.e., with positive probability), no matter the strategy of the second player. We classify such games according to the information and to the power of randomization available to the players. On the basis of information, the game can be onesided with either (a) player 1, or (b) player 2 having partial observation (andtheotherplayerhasperfect observation),or twosided with (c) both players having partial observation. On the basis of randomization, (a) the players may not be allowed to use randomization
What is Decidable about Partially Observable Markov Decision Processes with omegaRegular Objectives
, 2013
"... We consider partially observable Markov decision processes (POMDPs) with ωregular conditions specified as parity objectives. The qualitative analysis problem given a POMDP and a parity objective asks whether there is a strategy to ensure that the objective is satisfied with probability 1 (resp. pos ..."
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Cited by 10 (7 self)
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We consider partially observable Markov decision processes (POMDPs) with ωregular conditions specified as parity objectives. The qualitative analysis problem given a POMDP and a parity objective asks whether there is a strategy to ensure that the objective is satisfied with probability 1 (resp. positive probability). While the qualitative analysis problems are known to be undecidable even for very special cases of parity objectives, we establish decidability (with optimal EXPTIMEcomplete complexity) of the qualitative analysis problems for POMDPs with all parity objectives under finitememory strategies. We also establish optimal (exponential) memory bounds.
Reachabilitybased synthesis of feedback policies for motion planning under bounded disturbances
 in 2011 IEEE International Conference on Robotics and Automation (ICRA
, 2011
"... Abstract — The task of planning and controlling robot motion in practical applications is often complicated by the effects of model uncertainties and environment disturbances. We present in this paper a systematic approach for generating robust motion control strategies to satisfy high level specifi ..."
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Cited by 10 (3 self)
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Abstract — The task of planning and controlling robot motion in practical applications is often complicated by the effects of model uncertainties and environment disturbances. We present in this paper a systematic approach for generating robust motion control strategies to satisfy high level specifications of safety, target attainability, and invariance, under unknown but bounded, continuous disturbances. The motion planning task is decomposed into the two subproblems of finite horizon reach with avoid and infinite horizon invariance. The set of states for which each of the subproblems is robustly feasible is computed via iterative reachability calculations under a differential game framework. We discuss how the results of this computation can be used to inform selections of control inputs based upon state measurements at runtime and provide an algorithm for implementing the corresponding feedback control policies. Finally, we demonstrate an experimental application of this method to the control of an autonomous helicopter in tracking a moving ground vehicle. I.
Automated Feedback For Unachievable HighLevel Robot Behaviors
"... Abstract — One of the main challenges in robotics is the generation of controllers for autonomous, highlevel robot behaviors comprising a nontrivial sequence of actions. Recently, formal methods have emerged as a powerful tool for automatically generating autonomous robot controllers that guarant ..."
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Cited by 10 (4 self)
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Abstract — One of the main challenges in robotics is the generation of controllers for autonomous, highlevel robot behaviors comprising a nontrivial sequence of actions. Recently, formal methods have emerged as a powerful tool for automatically generating autonomous robot controllers that guarantee desired behaviors expressed by a class of temporal logic specifications. However, when there is no controller that fulfills the specification, these approaches do not provide the user with a source of failure, making the troubleshooting of specifications an unstructured and timeconsuming process. In this paper, we describe a procedure for analyzing an unsynthesizable specification to identify causes of failure. We also provide an interactive game for exploring possible causes of failure, in which the user attempts to fulfill the robot specification against an adversarial environment. Our approach is implemented within the LTLMoP toolkit for robot mission planning. I.
Formalizing and reasoning about quality
, 2012
"... Abstract. Traditional formal methods are based on a Boolean satisfaction notion: a reactive system satisfies, or not, a given specification. We generalize formal methods to also address the quality of systems. As an adequate specification formalism we introduce the linear temporal logic LTL[F]. The ..."
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Cited by 9 (6 self)
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Abstract. Traditional formal methods are based on a Boolean satisfaction notion: a reactive system satisfies, or not, a given specification. We generalize formal methods to also address the quality of systems. As an adequate specification formalism we introduce the linear temporal logic LTL[F]. The satisfaction value of an LTL[F] formula is a number between 0 and 1, describing the quality of the satisfaction. The logic generalizes traditional LTL by augmenting it with a (parameterized) set F of arbitrary functions over the interval [0, 1]. For example, F may contain the maximum or minimum between the satisfaction values of subformulas, their product, and their average. The classical decision problems in formal methods, such as satisfiability, model checking, and synthesis, are generalized to search and optimization problems in the quantitative setting. For example, model checking asks for the quality in which a specification is satisfied, and synthesis returns a system satisfying the specification with the highest quality. Reasoning about quality gives rise to other natural questions, like the distance between specifications. We formalize these basic questions and study them for LTL[F]. By extending the automatatheoretic approach for LTL to a setting that takes quality into an account, we are able to solve the above problems and show that reasoning about LTL[F] has roughly the same complexity as reasoning about traditional LTL. 1
Decentralized multiagent control from local LTL specifications
 51ST IEEE CONFERENCE ON DECISION AND CONTROL
, 2012
"... Abstract—We propose a methodology for decentralized multiagent control from Linear Temporal Logic (LTL) specifications. Each agent receives an independent specification to formally synthesize its own hybrid controller. Mutual satisfiability is not a priori guaranteed. Due to limited communication ..."
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Cited by 7 (4 self)
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Abstract—We propose a methodology for decentralized multiagent control from Linear Temporal Logic (LTL) specifications. Each agent receives an independent specification to formally synthesize its own hybrid controller. Mutual satisfiability is not a priori guaranteed. Due to limited communication, the agents utilize meeting events to exchange their controller automata and verify satisfiability through model checking. Local interaction only when common atomic propositions exist reduces the overall computational cost, facilitating scalability. Provably correct collision avoidance and convergence is ensured by Decentralized MultiAgent Navigation Functions. I.