2021
[BBF+21] Giovanni Bacci, Patricia Bouyer, Uli Fahrenberg, Kim Guldstrand Larsen, Nicolas Markey, and Pierre-Alain Reynier. Optimal and Robust Controller Synthesis Using Energy Timed Automata with Uncertainty. Formal Aspects of Computing 33(1):3-25. Springer-Verlag, January 2021.
Abstract

In this paper, we propose a novel framework for the synthesis of robust and optimal energy-aware controllers. The framework is based on energy timed automata, allowing for easy expression of timing-constraints and variable energy-rates. We prove decidability of the energy-constrained infinite-run problem in settings with both certainty and uncertainty of the energy-rates. We also consider the optimization problem of identifying the minimal upper bound that will permit existence of energy-constrained infinite runs. Our algorithms are based on quantifier elimination for linear real arithmetic. Using Mathematica and Mjollnir, we illustrate our framework through a real industrial example of a hydraulic oil pump. Compared with previous approaches our method is completely automated and provides improved results.

@article{fac2020-BBFLMR,
  author =              {Bacci, Giovanni and Bouyer, Patricia and Fahrenberg,
                         Uli and Larsen, Kim Guldstrand and Markey, Nicolas
                         and Reynier, Pierre-Alain},
  title =               {Optimal and Robust Controller Synthesis Using Energy
                         Timed Automata with Uncertainty},
  publisher =           {Springer-Verlag},
  journal =             {Formal Aspects of Computing},
  volume =              {33},
  number =              {1},
  pages =               {3-25},
  year =                {2021},
  month =               jan,
  doi =                 {10.1007/s00165-020-00521-4},
  abstract =            {In~this paper, we~propose a novel framework for the
                         synthesis of robust and optimal energy-aware
                         controllers. The~framework is based on energy timed
                         automata, allowing for easy expression of
                         timing-constraints and variable energy-rates.
                         We~prove decidability of the energy-constrained
                         infinite-run problem in settings with both certainty
                         and uncertainty of the energy-rates. We~also
                         consider the optimization problem of identifying the
                         minimal upper bound that will permit existence of
                         energy-constrained infinite runs. Our~algorithms are
                         based on quantifier elimination for linear real
                         arithmetic. Using Mathematica and Mjollnir,
                         we~illustrate our framework through a real
                         industrial example of a hydraulic oil pump. Compared
                         with previous approaches our method is completely
                         automated and provides improved results.},
}
[BHJ+21] Patricia Bouyer, Léo Henry, Samy Jaziri, Thierry Jéron, and Nicolas Markey. Diagnosing timed automata using timed markings. International Journal on Software Tools for Technology Transfer 23(2):229-253. Springer-Verlag, April 2021.
Abstract

We consider the problems of efficiently diagnosing (and predicting) what did (and will) happen after a given sequence of observations of the execution of a partially-observable one-clock timed automaton. This is made difficult by the facts that timed automata are infinite-state systems, and that they can in general not be determinized.

We introduce timed markings as a formalism to keep track of the evolution of the set of reachable configurations over time. We show how timed markings can be used to efficiently represent the closure under silent transitions of such automata. We report on our implementation of this approach compared to the approach of [Tripakis, Fault diagnosis for timed automata, 2002], and provide some insight to a generalization of our approach to n-clock timed automata.

@article{sttt23(2)-BHJJM,
  author =              {Bouyer, Patricia and Henry, L{\'e}o and Jaziri, Samy
                         and J{\'e}ron, Thierry and Markey, Nicolas},
  title =               {Diagnosing timed automata using timed markings},
  publisher =           {Springer-Verlag},
  journal =             {International Journal on Software Tools for
                         Technology Transfer},
  volume =              {23},
  number =              {2},
  pages =               {229-253},
  year =                {2021},
  month =               apr,
  doi =                 {10.1007/s10009-021-00606-2},
  abstract =            {We~consider the problems of efficiently diagnosing
                         (and~predicting) what did (and~will) happen after a
                         given sequence of observations of the execution of a
                         partially-observable one-clock timed automaton. This
                         is made difficult by the facts that timed automata
                         are infinite-state systems, and that they can in
                         general not be determinized. \par We~introduce timed
                         markings as a formalism to keep track of the
                         evolution of the set of reachable configurations
                         over time. We show how timed markings can be used to
                         efficiently represent the closure under silent
                         transitions of such automata. We report on our
                         implementation of this approach compared to the
                         approach of [Tripakis, Fault diagnosis for timed
                         automata,~2002], and provide some insight to a
                         generalization of our approach to {{\(n\)}}-clock
                         timed automata.},
}
[HMR21] Loïc Hélouët, Nicolas Markey, and Ritam Raha. Reachability games with relaxed energy constraints. Information and Computation. Elsevier, 2021. To appear.
Abstract

We study games with reachability objectives under energy constraints. We first prove that under strict energy constraints (either only lower-bound constraint or interval constraint), those games are LOGSPACE-equivalent to energy games with the same energy constraints but without reachability objective (i.e., for infinite runs). We then consider two relaxations of the upper-bound constraints (while keeping the lower-bound constraint strict): in the first one, called weak upper bound, the upper bound is absorbing, i.e., when the upper bound is reached, the extra energy is not stored; in the second one, we allow for temporary violations of the upper bound, imposing limits on the number or on the amount of violations.

We prove that when considering weak upper bound, reachability objectives require memory, but can still be solved in polynomial-time for one-player arenas; we prove that they are in NP in the two-player setting. Allowing for bounded violations makes the problem PSPACE-complete for one-player arenas and EXPTIME-complete for two players. We then address the problem of existence of bounds for a given arena. We show that with reachability objectives, existence can be a simpler problem than the game itself, and conversely that with infinite games, existence can be harder.

@article{icomp2021-HMR,
  author =              {H{\'e}lou{\"e}t, Lo{\"\i}c and Markey, Nicolas and
                         Raha, Ritam},
  title =               {Reachability games with relaxed energy constraints},
  publisher =           {Elsevier},
  journal =             {Information and Computation},
  year =                {2021},
  doi =                 {10.1016/j.ic.2021.104806},
  note =                {To~appear},
  abstract =            {We study games with reachability objectives under
                         energy constraints. We first prove that under strict
                         energy constraints (either only lower-bound
                         constraint or interval constraint), those games are
                         LOGSPACE-equivalent to energy games with the same
                         energy constraints but without reachability
                         objective (i.e., for infinite runs). We then
                         consider two relaxations of the upper-bound
                         constraints (while keeping the lower-bound
                         constraint strict): in the first one, called weak
                         upper bound, the upper bound is absorbing, i.e.,
                         when the upper bound is reached, the extra energy is
                         not stored; in the second one, we allow for
                         temporary violations of the upper bound, imposing
                         limits on the number or on the amount of violations.
                         \par We prove that when considering weak upper
                         bound, reachability objectives require memory, but
                         can still be solved in polynomial-time for
                         one-player arenas; we prove that they are in NP in
                         the two-player setting. Allowing for bounded
                         violations makes the problem PSPACE-complete for
                         one-player arenas and EXPTIME-complete for two
                         players. We then address the problem of existence of
                         bounds for a given arena. We show that with
                         reachability objectives, existence can be a simpler
                         problem than the game itself, and conversely that
                         with infinite games, existence can be harder.},
}
[AZZ+21] Jie An, Bohua Zhan, Naijun Zhan, and Miaomiao Zhang. Learning nondeterministic real-time automata. ACM Transactions on Embedded Computing Systems 20(5s):99:1-99:26. ACM Press, October 2021.
@article{tecs20(5s)-AZZZ,
  author =              {An, Jie and Zhan, Bohua and Zhan, Naijun and Zhang,
                         Miaomiao},
  title =               {Learning nondeterministic real-time automata},
  publisher =           {ACM Press},
  journal =             {ACM Transactions on Embedded Computing Systems},
  volume =              {20},
  number =              {5s},
  pages =               {99:1-99:26},
  year =                {2021},
  month =               oct,
  doi =                 {10.1145/3477030},
}
Coauthor list