Safety control of piece-wise continuous order preserving systems

This paper is concerned with safety control of systems with imperfect state information and disturbance input. Specifically, we consider the class of systems whose dynamics preserve a partial ordering. We provide necessary and sufficient conditions under which a given set of initial states is steerable away from a specified bad set. Moreover, a control strategy is provided that guarantees that the bad set is avoided. Such characterization is achieved for order preserving systems while for general systems only an approximated solution is achievable. A method for implementation of the control strategy is provided and the effectiveness of the proposed method is illustrated via a numerical example and employed for obstacle avoidance of a ship.National Science Foundation (U.S.) (NSF CAREER AWARD # CNS-0642719

Cooperative Collision Avoidance at Intersections: Algorithms and Experiments

In this paper, we leverage vehicle-to-vehicle (V2V) communication technology to implement computationally efficient decentralized algorithms for two-vehicle cooperative collision avoidance at intersections. Our algorithms employ formal control theoretic methods to guarantee a collision-free (safe) system, whereas overrides are only applied when necessary to prevent a crash. Model uncertainty and communication delays are explicitly accounted for by the model and by the state estimation algorithm. The main contribution of this work is to provide an experimental validation of our method on two instrumented vehicles engaged in an intersection collision avoidance scenario in a test track

Provably safe design of driver-assist systems through hybrid automata with hidden modes

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 71-73).In this thesis, I consider the problem of collision avoidance between two vehicles approaching an intersection. These vehicles are human driven and one or both are equipped with an on-board driver assist system that provides warnings and can apply automatic braking/throttle when needed. This type of system will establish an intermediary step in the progression towards fully autonomous vehicles. It will allow human drivers to retain control of their vehicles while providing the guidance for drivers to apply the necessary inputs to prevent collisions before autonomous control becomes necessary. A formal approach to the design of the driver assist system is taken, employing a hybrid automaton model. This model has hidden modes, which arise from the driver making decisions about whether or not to follow the provided warnings. As a consequence, the driver assist system design is formulated as a safety control problem for a hybrid automaton with hidden modes. The solution approach is based on a mode estimator that keeps track of the possible driver decisions and, on their basis, provides warning and control inputs that ensure safety. The resulting algorithm is computationally efficient as it leverages the order preserving properties of the vehicle dynamics.by Cassidy Martin Palas.S.M

Control for Safety Specifications of Systems With Imperfect Information on a Partial Order

In this paper, we consider the control problem for uncertain systems with imperfect information, in which an output of interest must be kept outside an undesired region (the bad set) in the output space. The state, input, output, and disturbance spaces are equipped with partial orders. The system dynamics are either input/output order preserving with output in R[superscript 2] or given by the parallel composition of input/output order preserving dynamics each with scalar output. We provide necessary and sufficient conditions under which an initial set of possible system states is safe, that is, the corresponding outputs are steerable away from the bad set with open loop controls. A closed loop control strategy is explicitly constructed, which guarantees that the current set of possible system states, as obtained from an estimator, generates outputs that never enter the bad set. The complexity of algorithms that check safety of an initial set of states and implement the control map is quadratic with the dimension of the state space. The algorithms are illustrated on two application examples: a ship maneuver to avoid an obstacle and safe navigation of an helicopter among buildings.National Science Foundation (U.S.) (CAREER Award CNS-0642719