Алгоритм уникнення зіткнень для безпілотних літальних апаратів

Описано галузі застосування безпілотної техніки. Зроблено аналіз існуючих систем уникнення зіткнення. На основі математичної моделі руху матеріальної точки запропоновано алгоритм уникнення зіткнення для безпілотних літальних апаратів. Він може бути основою майбутніх розробок та алгоритмів у цій галузі

Система прийняття рішень для безпілотних літаків

Описано підхід для розробки системи прийняття рішень для уникнення зіткнення безпілотних літаків. Розглянуто існуючі системи уникнення зіткнення, розроблено фази руху літака в просторі та розроблено підхід для оцінки ризику для даної системи через оцінку потенційних втрат.Описан подход для разработки системы принятия решений для избежания столкновения беспилотных самолетов. Рассмотрены существующие системы избежания столкновений, разработаны фазы движения самолета в пространстве и разработан подход для оценки риска для данной системы через оценку потенциальных потерь.Approach for development of ruled-based system for collision avoidance of unmanned airplanes is described. The existent systems of collission avoidence are considered, the phases of motion of airplane in space are worked out and approach for the estimation of risk for this system through the estimation of potential losses is worked ou

Efficient Constraint-Based Dynamic Strategies For Generating Counterexamples

Rapport de RechercheChecking safety properties is mandatory in the validation process of critical software. When formal verification tools fail to prove some properties, testing is necessary. Generation of counterexamples violating some properties is therefore an important issue, especially for tricky programs the test cases of which are very difficult to compute. We propose in this paper different constraint based dynamic strategies for generating structural test cases that violate a postcondition of C or JAVA programs. These strategies have been evaluated on standard benchmarks and on real applications. Experiments on a real industrial Flasher Manager controller and on the public available implementation of the Traffic Collision Avoidance System (TCAS) show that our system outperforms state of the art model checking tools and constraint based test generation systems

A finite state machine framework for robust analysis and control of hybrid systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 107-115).Hybrid systems, describing interactions between analog and discrete dynamics, are pervasive in engineered systems and pose unique, challenging performance verification and control synthesis problems. Existing approaches either lead to computationally intensive and sometimes undecidable problems, or make use of highly specialized discrete abstractions with questionable robustness properties. The thesis addresses some of these challenges by developing a systematic, computationally tractable approach for design and certification of systems with discrete, finite-valued actuation and sensing. This approach is inspired by classical robust control, and is based on the use of finite state machines as nominal models of the hybrid systems. The development does not assume a particular algebraic or topological structure on the signal sets. The thesis adopts an input/output view of systems, proposes specific classes of inequality constraints to describe performance objectives, and presents corresponding 'small gain' type arguments for robust performance verification. A notion of approximation that is compatible with the goal of controller synthesis is defined. An approximation architecture that is capable of handling unstable systems is also proposed.(cont.) Constructive algorithms for generating finite state machine approximations of the hybrid systems of interest, and for efficiently computing a-posteriori bounds on the approximation error are presented. Analysis of finite state machine models, which reduces to searching for an appropriate storage function, is also shown to be related to the problem of checking for the existence of negative cost cycles in a network, thus allowing for a verification algorithm with polynomial worst-case complexity. Synthesis of robust control laws is shown to reduce to solving a discrete, infinite horizon min-max problem. The resulting controllers consist of a finite state machine state observer for the hybrid system and a memoryless full state feedback switching control law. The use of this framework is demonstrated through a simple benchmark example, the problem of stabilizing a double integrator using switched gain feedback and binary sensing. Finally, some extensions to incremental performance objectives and robustness measures are presented.by Danielle C. Tarraf.Ph.D

A verification framework for hybrid systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 193-205) and index.Combining; discrete state transitions with differential equations, Hybrid system models provide an expressive formalism for describing software systems that interact with a physical environment. Automatically checking properties, such as invariance and stability, is extremely hard for general hybrid models, and therefore current research focuses on models with restricted expressive power. In this thesis we take a complementary approach by developing proof techniques that are not necessarily automatic, but are applicable to a general class of hybrid systems. Three components of this thesis, namely, (i) semantics for ordinary and probabilistic hybrid models, (ii) methods for proving invariance, stability, and abstraction, and (iii) software tools supporting (i) and (ii), are integrated within a common mathematical framework. (i) For specifying nonprobabilistic hybrid models, we present Structured Hybrid I/O Automata (SHIOAs) which adds control theory-inspired structures, namely state models, to the existing Hybrid I/O Automata, thereby facilitating description of continuous behavior. We introduce a generalization of SHIOAs which allows both nondeterministic and stochastic transitions and develop the trace-based semantics for this framework. (ii) We present two techniques for establishing lower-bounds on average dwell time (ADT) for SHIOA models. This provides a sufficient condition of establishing stability for SHIOAs with stable state models. A new simulation-based technique which is sound for proving ADT-equivalence of SHIOAs is proposed. We develop notions of approximate implementation and corresponding proof techniques for Probabilistic I/O Automata. Specifically, a PIOA A is an E-approximate implementation of B, if every trace distribution of A is c-close to some trace distribution of B-closeness being measured by a metric on the space of trace distributions.(cont.) We present a new class of real-valued simulation functions for proving c-approximate implementations, and demonstrate their utility in quantitatively reasoning about probabilistic safety and termination. (iii) We introduce a specification language for SHIOAs and a theorem prover interface for this language. The latter consists of a translator to typed high order logic and a set of PVS-strategies that partially automate the above verification techniques within the PVS theorem prover.by Sayan Mitra.Ph.D

High-Level Modeling and Analysis of TCAS

In this paper, we demonstrate a high-level approach to modeling and analyzing complex safety-critical systems through a case study in the area of air traffic management. In particular, we focus our attention on the Traffic Alert and Collision Avoidance System (TCAS) [11, 12]; an on-board conflict detection and resolution system which alerts pilots to the presence of nearby aircraft that pose a mid-air collision threat and issues conflict resolution advisories. Due to the complexity of the TCAS software and the hybrid nature of the closed-loop system, the traditional testing techniques through simulation do not constitute a viable verification approach. To aid people in analyzing and designing such systems, we advocate defining high-level mathematical system models that capture the behavior not only of the software, but also of the airplanes, sensors, and pilots— that is, high-level hybrid system models. In particular, we show how the core components of this complex system can be captured by relatively simple Hybrid I/O Automata (HIOA) [9, 10], which are amenable to formal analysis. We then outline a methodology for establishing conditions under which the conflict resolution advisories issued by TCAS guarantee sufficient separation in altitude for aircraft involved in mid-air collision threats. Although our results are intended only as illustrations of high-level modeling and analysis techniques, the TCAS system models provide a foundation for study of a wide range of properties of the system’s behavior