The Experts below are selected from a list of 1830 Experts worldwide ranked by ideXlab platform

Calin Belta - One of the best experts on this subject based on the ideXlab platform.

  • ACC - Continuous-Time Signal Temporal Logic Planning with Control Barrier Functions.
    2020 American Control Conference (ACC), 2020
    Co-Authors: Guang Yang, Calin Belta, Roberto Tron
    Abstract:

    Temporal Logic (TL) guided control problems have gained enormous interests in recent years. A wide range of properties, such as liveness and safety, can be specified through TL. On the other hand, Control Barrier Functions (CBF) have shown success in the context of safety critical applications that require constraints on the system states. In this paper, we consider linear cyber-physical systems with continuous dynamics, where controls are generated by digital computers in discrete time. We propose an offline trajectory planner for such systems subject to linear constraints given as Signal Temporal Logic (STL) formulas. The proposed planner is based on a Mixed Integer Quadratic Programming (MIQP) formulation that utilizes CBFs to produce system trajectories that are valid in continuous time; moreover we allow STL predicates with arbitrary time constraints, in which asynchronous control updates are allowed. We validate our theoretical results through numerical simulations.

  • average based robustness for continuous time Signal temporal logic
    Conference on Decision and Control, 2019
    Co-Authors: Noushin Mehdipour, Cristianioan Vasile, Calin Belta
    Abstract:

    We propose a new robustness score for Continuous-Time Signal Temporal Logic (STL) specifications. Instead of considering only the most severe point along the evolution of the Signal, we use average scores to extract more information from the Signal, emphasizing robust satisfaction of all the specifications’ subformulae over their entire time interval domains. We demonstrate the advantages of this new score in falsification and control synthesis problems in systems with complex dynamics and multi-agent systems.

  • continuous time Signal temporal logic planning with control barrier function
    arXiv: Systems and Control, 2019
    Co-Authors: Guang Yang, Roberto Tron, Calin Belta
    Abstract:

    Temporal Logic (TL) guided control problems have gained interests in recent years. By using the TL, one can specify a wide range of temporal constraints on the system and is widely used in cyber-physical systems. On the other hand, Control Barrier Functions have also gained interests in the context of safety critical applications. However, most of the existing approaches only focus on discrete-time dynamical systems. In this paper, we propose an offline trajectory planner for linear systems subject to safety and temporal specifications. Such specifications can be expressed as logical junctions or disjunctions of linear CBFs, or as STL specifications with linear predicates. Our planner produces trajectories that are valid in continuous time, while assuming only discrete-time control updates and arbitrary time interval in the STL formula. Our planner is based on a Mixed Integer Quadratic Programming (MIQP) formulation, where the linear STL predicates are encoded as set of linear constraints to guarantee satisfaction at on a finite discrete set of time instants, while we use CBFs to derive constraints that guarantee continuous satisfaction between time instants. Moreover, we have shown the predicates can be encoded as time-based CBF constraints for system with any relative degrees. We validate our theoretical results and formulation through numerical simulations.

  • CDC - Average-based Robustness for Continuous-Time Signal Temporal Logic
    2019 IEEE 58th Conference on Decision and Control (CDC), 2019
    Co-Authors: Noushin Mehdipour, Cristianioan Vasile, Calin Belta
    Abstract:

    We propose a new robustness score for Continuous-Time Signal Temporal Logic (STL) specifications. Instead of considering only the most severe point along the evolution of the Signal, we use average scores to extract more information from the Signal, emphasizing robust satisfaction of all the specifications’ subformulae over their entire time interval domains. We demonstrate the advantages of this new score in falsification and control synthesis problems in systems with complex dynamics and multi-agent systems.

Jose C. M. Bermudez - One of the best experts on this subject based on the ideXlab platform.

  • On the compensation of the (sin x)/x distortion in discrete-time to Continuous-Time Signal conversions
    IEEE Transactions on Circuits and Systems I: Fundamental Theory and Applications, 1995
    Co-Authors: Rui Seara, Jose C. M. Bermudez, Sidnei Noceti Filho, J. Mayer
    Abstract:

    Discrete-time to Continuous-Time Signal conversions introduce the well known (sin x)/x spectral distortion. This paper presents an analytical methodology which adjusts the Q-factors and/or the pole magnitudes of the system to compensate the distortion. From this methodology three compensation methods are derived. Each method establishes a distinct tradeoff between precision and computational effort. The compensation techniques are very simple to implement and do not modify the order of the uncompensated system. The initial formulation is extended to include the compensation of z-domain transfer functions. Examples and comparisons demonstrate the effectiveness and applicability of the proposed methodology. >

  • A new method for the compensation of the (sin x)/x distortion in discrete-time to Continuous-Time Signal conversions
    IEEE International Symposium on Circuits and Systems, 1
    Co-Authors: Sidnei Noceti Filho, Rui Seara, Jose C. M. Bermudez
    Abstract:

    A method is proposed for the compensation of the (sin x)/x distortion inherent to the conversion from discrete-time to Continuous-Time Signal waveforms. The correction of the transfer function of the system is performed by the iterative adjustment of the Q factors of its poles. The algorithm is very simple to implement and leads to very good results, as verified by the examples presented. >

Roberto Tron - One of the best experts on this subject based on the ideXlab platform.

  • ACC - Continuous-Time Signal Temporal Logic Planning with Control Barrier Functions.
    2020 American Control Conference (ACC), 2020
    Co-Authors: Guang Yang, Calin Belta, Roberto Tron
    Abstract:

    Temporal Logic (TL) guided control problems have gained enormous interests in recent years. A wide range of properties, such as liveness and safety, can be specified through TL. On the other hand, Control Barrier Functions (CBF) have shown success in the context of safety critical applications that require constraints on the system states. In this paper, we consider linear cyber-physical systems with continuous dynamics, where controls are generated by digital computers in discrete time. We propose an offline trajectory planner for such systems subject to linear constraints given as Signal Temporal Logic (STL) formulas. The proposed planner is based on a Mixed Integer Quadratic Programming (MIQP) formulation that utilizes CBFs to produce system trajectories that are valid in continuous time; moreover we allow STL predicates with arbitrary time constraints, in which asynchronous control updates are allowed. We validate our theoretical results through numerical simulations.

  • continuous time Signal temporal logic planning with control barrier function
    arXiv: Systems and Control, 2019
    Co-Authors: Guang Yang, Roberto Tron, Calin Belta
    Abstract:

    Temporal Logic (TL) guided control problems have gained interests in recent years. By using the TL, one can specify a wide range of temporal constraints on the system and is widely used in cyber-physical systems. On the other hand, Control Barrier Functions have also gained interests in the context of safety critical applications. However, most of the existing approaches only focus on discrete-time dynamical systems. In this paper, we propose an offline trajectory planner for linear systems subject to safety and temporal specifications. Such specifications can be expressed as logical junctions or disjunctions of linear CBFs, or as STL specifications with linear predicates. Our planner produces trajectories that are valid in continuous time, while assuming only discrete-time control updates and arbitrary time interval in the STL formula. Our planner is based on a Mixed Integer Quadratic Programming (MIQP) formulation, where the linear STL predicates are encoded as set of linear constraints to guarantee satisfaction at on a finite discrete set of time instants, while we use CBFs to derive constraints that guarantee continuous satisfaction between time instants. Moreover, we have shown the predicates can be encoded as time-based CBF constraints for system with any relative degrees. We validate our theoretical results and formulation through numerical simulations.

George J. Pappas - One of the best experts on this subject based on the ideXlab platform.

  • robustness of temporal logic specifications for continuous time Signals
    Theoretical Computer Science, 2009
    Co-Authors: Georgios Fainekos, George J. Pappas
    Abstract:

    In this paper, we consider the robust interpretation of Metric Temporal Logic (MTL) formulas over Signals that take values in metric spaces. For such Signals, which are generated by systems whose states are equipped with non-trivial metrics, for example continuous or hybrid, robustness is not only natural, but also a critical measure of system performance. Thus, we propose multi-valued semantics for MTL formulas, which capture not only the usual Boolean satisfiability of the formula, but also topological information regarding the distance, @e, from unsatisfiability. We prove that any other Signal that remains @e-close to the initial one also satisfies the same MTL specification under the usual Boolean semantics. Finally, our framework is applied to the problem of testing formulas of two fragments of MTL, namely Metric Interval Temporal Logic (MITL) and closed Metric Temporal Logic (clMTL), over Continuous-Time Signals using only discrete-time analysis. The motivating idea behind our approach is that if the Continuous-Time Signal fulfills certain conditions and the discrete-time Signal robustly satisfies the temporal logic specification, then the corresponding Continuous-Time Signal should also satisfy the same temporal logic specification.

  • FORMATS - Robust sampling for MITL specifications
    Lecture Notes in Computer Science, 1
    Co-Authors: Georgios Fainekos, George J. Pappas
    Abstract:

    Real-time temporal logic reasoning about trajectories of physical systems necessitates models of time which are continuous. However, discrete time temporal logic reasoning is computationally more efficient than continuous time. Moreover, in a number of engineering applications only discrete time models are available for analysis. In this paper, we introduce a framework for testing MITL specifications on continuous time Signals using only discrete time analysis. The motivating idea behind our approach is that if the dynamics of the Signal fulfills certain conditions and the discrete time Signal robustly satisfies the MITL specification, then the corresponding continuous time Signal should also satisfy the same MITL specification.

Alan V. Oppenheim - One of the best experts on this subject based on the ideXlab platform.

  • Sinc Interpolation of Nonuniform Samples
    IEEE Transactions on Signal Processing, 2011
    Co-Authors: Shay Maymon, Alan V. Oppenheim
    Abstract:

    It is well known that a bandlimited Signal can be uniquely recovered from nonuniformly spaced samples under certain conditions on the nonuniform grid and provided that the average sampling rate meets or exceeds the Nyquist rate. However, reconstruction of the Continuous-Time Signal from nonuniform samples is typically more difficult to implement than from uniform samples. Motivated by the fact that sinc interpolation results in perfect reconstruction for uniform sampling, we develop a class of approximate reconstruction methods from nonuniform samples based on the use of time-invariant lowpass filtering, i.e., sinc interpolation. The methods discussed consist of four cases incorporated in a single framework. The case of sub-Nyquist sampling is also discussed and nonuniform sampling is shown as a possible approach to mitigating the impact of aliasing.

  • randomized sinc interpolation of nonuniform samples
    European Signal Processing Conference, 2009
    Co-Authors: Shay Maymon, Alan V. Oppenheim
    Abstract:

    It is well known that a bandlimited Signal can be uniquely determined from nonuniformly spaced samples, provided that the average sampling rate exceeds the Nyquist rate. However, reconstruction of the Continuous-Time Signal from nonuniform samples is more difficult than from uniform samples. This paper develops and compares simpler approximate methods for Signal reconstruction from nonuniform samples.

  • EUSIPCO - Randomized sinc interpolation of nonuniform samples
    2009
    Co-Authors: Shay Maymon, Alan V. Oppenheim
    Abstract:

    It is well known that a bandlimited Signal can be uniquely determined from nonuniformly spaced samples, provided that the average sampling rate exceeds the Nyquist rate. However, reconstruction of the Continuous-Time Signal from nonuniform samples is more difficult than from uniform samples. This paper develops and compares simpler approximate methods for Signal reconstruction from nonuniform samples.