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27
Receding horizon temporal logic planning
- IEEE Transactions on Automatic Control
, 2012
"... Abstract We present a methodology for automatic synthesis of embedded control software that incorporates a class of linear temporal logic (LTL) specifications sufficient to describe a wide range of properties including safety, stability, progress, obligation, response and guarantee. To alleviate th ..."
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Cited by 35 (11 self)
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Abstract We present a methodology for automatic synthesis of embedded control software that incorporates a class of linear temporal logic (LTL) specifications sufficient to describe a wide range of properties including safety, stability, progress, obligation, response and guarantee. To alleviate the associated computational complexity of LTL synthesis, we propose a receding horizon framework that effectively reduces the synthesis problem into a set of smaller problems. The proposed control architecture consists of a goal generator, a trajectory planner, and a continuous controller. The goal generator reduces the trajectory generation problem into a sequence of smaller problems of short horizon while preserving the desired system-level temporal properties. Subsequently, in each iteration, the trajectory planner solves the corresponding short-horizon problem with the currently observed state as the initial state and generates a feasible trajectory to be implemented by the continuous controller. Based on the simulation property, we show that the composition of the goal generator, trajectory planner and continuous controller and the corresponding receding horizon framework guarantee the correctness of the system with respect to its specification regardless of the environment in which the system operates. In addition, we present a response mechanism to handle failures that may occur due to a mismatch between the actual system and its model. The effectiveness of the proposed technique is demonstrated through an example of an autonomous vehicle navigating an urban environment. This example also illustrates that the system is not only robust with respect to exogenous disturbances but is also capable of properly handling violation of the environment assumption that is explicitly stated as part of the system specification .
Correct, Reactive Robot Control from Abstraction and Temporal Logic Specifications
- IEEE RAM
"... We describe recent advances in formal synthesis of robot controllers from temporal logic specifications. In particular, we consider reactive specifications where the robot continuously gathers information about its environment and decides its action at run time based on this information. The automat ..."
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Cited by 16 (4 self)
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We describe recent advances in formal synthesis of robot controllers from temporal logic specifications. In particular, we consider reactive specifications where the robot continuously gathers information about its environment and decides its action at run time based on this information. The automatically generated controller is provably correct with respect to a given specification for all the valid environment behaviors. We discuss the main limitation of such controller synthesis – the state explosion problem – and two different approaches that mitigate this problem. Computational tools that implement these approaches are also described. An autonomous vehicle navigating an urban-like environment is used as an illustrative example throughout the paper.
Distributed Power Allocation for Vehicle Management Systems
"... Abstract — We consider the problem of designing distributed control protocols-for aircraft vehicle management systemsthat cooperatively allocate electric power while meeting certain higher level goals and requirements, and dynamically reacting to the changes in the internal system state and external ..."
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Cited by 14 (11 self)
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Abstract — We consider the problem of designing distributed control protocols-for aircraft vehicle management systemsthat cooperatively allocate electric power while meeting certain higher level goals and requirements, and dynamically reacting to the changes in the internal system state and external environment. A decentralized control problem is posed where each power distribution unit is equipped with a controller that implements a local protocol to allocate power to a certain subset of loads. We use linear temporal logic as the specification language for describing correct behaviors of the system (e.g., safe operating conditions) as well as the admissible dynamic behavior of the environment due to, for example, wind gusts and changes in system health. We start with a global specification and decompose it into local ones. These decompositions allow the protocols for each local controller to be separately synthesized and locally implemented while guaranteeing the global specifications to hold. Through a design example, we show that by refining the interface rules between power distribution units, it is possible to reduce the total power requirement. I.
A case study on reactive protocols for aircraft electric power distribution
- In Proc. IEEE Conference on Decision and Control
, 2012
"... Abstract — We consider the problem of designing a control protocol for the aircraft electric power system that meets system requirements and reacts dynamically to changes in internal system states. We formalize these requirements by translating them into a temporal logic specification language descr ..."
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Cited by 8 (5 self)
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Abstract — We consider the problem of designing a control protocol for the aircraft electric power system that meets system requirements and reacts dynamically to changes in internal system states. We formalize these requirements by translating them into a temporal logic specification language describing the correct behaviors of the system, and apply formal methods to automatically synthesize a controller protocol that satisfies system properties and requirements. Through an example, we perform a design exploration to show the benefits and tradeoffs between centralized and distributed control architectures. I.
Efficient reactive controller synthesis for a fragment of linear temporal logic
- in IEEE International Conference on Robotics and Automation (ICRA
, 2013
"... Abstract — Motivated by robotic motion planning, we de-velop a framework for control policy synthesis for both non-deterministic transition systems and Markov decision processes that are subject to temporal logic task specifications. We introduce a fragment of linear temporal logic that can be used ..."
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Cited by 7 (2 self)
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Abstract — Motivated by robotic motion planning, we de-velop a framework for control policy synthesis for both non-deterministic transition systems and Markov decision processes that are subject to temporal logic task specifications. We introduce a fragment of linear temporal logic that can be used to specify common motion planning tasks such as safe navigation, response to the environment, persistent coverage, and surveillance. This fragment is computationally efficient; the complexity of control policy synthesis is a doubly-exponential improvement over standard linear temporal logic for both non-deterministic transition systems and Markov decision processes. This improvement is possible because we compute directly on the original system, as opposed to the automata-based approach commonly used. We give simulation results for representative motion planning tasks and compare to generalized reactivity(1). I.
On Synthesizing Robust Discrete Controllers under Modeling Uncertainty
, 2012
"... We investigate the robustness of reactive control protocols synthesized to guarantee system’s correctness with respect to given temporal logic specifications. We consider uncertainties in open finite transition systems due to unmodeled transitions. The resulting robust synthesis problem is formulate ..."
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Cited by 6 (1 self)
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We investigate the robustness of reactive control protocols synthesized to guarantee system’s correctness with respect to given temporal logic specifications. We consider uncertainties in open finite transition systems due to unmodeled transitions. The resulting robust synthesis problem is formulated as a temporal logic game. In particular, if the specification is in the so-called generalized reactivity [1] fragment of linear temporal logic, so is the augmented specification in the resulting robust synthesis problem. Hence, the robust synthesis problem belongs to the same complexity class with the nominal synthesis problem, and is amenable to polynomial time solvers. Additionally, we discuss reasoning about the effects of different levels of uncertainties on robust synthesizability and demonstrate the results on a simple robot motion planning scenario.
Conformance testing as falsification for cyber-physical systems
- In ICCPS 2014
, 2014
"... In Model-Based Design of Cyber-Physical Systems (CPS), it is often desirable to develop several models of varying fidelity. Models of different fidelity levels can enable mathe-matical analysis of the model, control synthesis, faster simu-lation etc. Furthermore, when (automatically or manually) tra ..."
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Cited by 6 (3 self)
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In Model-Based Design of Cyber-Physical Systems (CPS), it is often desirable to develop several models of varying fidelity. Models of different fidelity levels can enable mathe-matical analysis of the model, control synthesis, faster simu-lation etc. Furthermore, when (automatically or manually) transitioning from a model to its implementation on an ac-tual computational platform, then again two different ver-sions of the same system are being developed. In all previous cases, it is necessary to define a rigorous notion of confor-mance between different models and between models and their implementations. This paper argues that conformance should be a measure of distance between systems. Albeit a range of theoretical distance notions exists, a way to com-pute such distances for industrial size systems and models has not been proposed yet. This paper addresses exactly this problem. A universal notion of conformance as close-ness between systems is rigorously defined, and evidence is presented that this implies a number of other application-dependent conformance notions. An algorithm for detect-ing that two systems are not conformant is then proposed, which uses existing proven tools. A method is also proposed to measure the degree of conformance between two systems. The results are demonstrated on a range of models. 1.
An Aircraft Electric Power Testbed for Validating Automatically Synthesized Reactive Control Protocols
, 2013
"... Modern aircraft increasingly rely on electric power for subsys-tems that have traditionally run on mechanical power. The complexity and safety-criticality of aircraft electric power sys-tems have therefore increased, rendering the design of these systems more challenging. This work is motivated by t ..."
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Cited by 4 (2 self)
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Modern aircraft increasingly rely on electric power for subsys-tems that have traditionally run on mechanical power. The complexity and safety-criticality of aircraft electric power sys-tems have therefore increased, rendering the design of these systems more challenging. This work is motivated by the potential that correct-by-construction reactive controller syn-thesis tools may have in increasing the effectiveness of the elec-tric power system design cycle. In particular, we have built an experimental hardware platform that captures some key elements of aircraft electric power systems within a simplified setting. We intend to use this platform for validating the ap-plicability of theoretical advances in correct-by-construction control synthesis and for studying implementation-related challenges. We demonstrate a simple design workflow from
Abstraction, Discretization, and Robustness in Temporal Logic Control of Dynamical Systems∗
"... Abstraction-based, hierarchical approaches to control syn-thesis from temporal logic specifications for dynamical sys-tems have gained increased popularity over the last decade. Yet various issues commonly encountered and extensively dealt with in control systems have not been adequately dis-cussed ..."
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Cited by 3 (1 self)
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Abstraction-based, hierarchical approaches to control syn-thesis from temporal logic specifications for dynamical sys-tems have gained increased popularity over the last decade. Yet various issues commonly encountered and extensively dealt with in control systems have not been adequately dis-cussed in the context of temporal logic control of dynamical systems, such as inter-sample behaviors of a sampled-data system, effects of imperfect state measurements and unmod-eled dynamics, and the use of time-discretized models to de-sign controllers for continuous-time dynamical systems. We discuss these issues in this paper. The main motivation is to demonstrate the possibility of accounting for the mis-matches between a continuous-time control system and its various types of abstract models used for control synthesis. We do this by incorporating additional robustness measures in the abstract models. Such robustness measures are gained at the price of either increased nondeterminism in the ab-stracted models or relaxed versions of the specification being realized. Under a unified notion of abstraction, we provide concrete means of incorporating these robustness measures and establish results that demonstrate their effectiveness in dealing with the above mentioned issues.
Optimal control of nonlinear systems with temporal logic specifications
- In Proc. of the International Symposium on Robotics Research (ISRR
, 2013
"... Abstract We present a mathematical programming-based method for optimal con-trol of nonlinear systems subject to temporal logic task specifications. We specify tasks using a fragment of linear temporal logic (LTL) that allows both finite- and infinite-horizon properties to be specified, including ta ..."
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Cited by 2 (1 self)
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Abstract We present a mathematical programming-based method for optimal con-trol of nonlinear systems subject to temporal logic task specifications. We specify tasks using a fragment of linear temporal logic (LTL) that allows both finite- and infinite-horizon properties to be specified, including tasks such as surveillance, pe-riodic motion, repeated assembly, and environmental monitoring. Our method di-rectly encodes an LTL formula as mixed-integer linear constraints on the system variables, avoiding the computationally expensive process of creating a finite ab-straction. Our approach is efficient; for common tasks our formulation uses signifi-cantly fewer binary variables than related approaches and gives the tightest possible convex relaxation. We apply our method on piecewise affine systems and certain classes of differentially flat systems. In numerical experiments, we solve temporal logic motion planning tasks for high-dimensional (10+ continuous state) systems. 1
