1,724,280 research outputs found
Robust Controller Synthesis in Timed Automata
Full text linkWe consider the fundamental problem of Büchi acceptance in timed automata in a robust setting. The problem is formalised in terms of controller synthesis: timed automata are equipped with a parametrised game-based semantics that models the possible perturbations of the decisions taken by the controller. We characterise timed automata that are robustly controllable for some parameter, with a simple graph theoretic condition, by showing the equivalence with the existence of an aperiodic lasso that satisfies the winning condition (aperiodicity was defined and used earlier in different contexts to characterise convergence phenomena in timed automata). We then show decidability and PSPACE-completeness of our problem
Code for Paper: Distributed H2 Controller Synthesis for Multi-Agent Systems with Stochastic Packet Loss
No full textThis is the code to produce the figures from the paper "Distributed H2 Controller Synthesis for Multi-Agent Systems with Stochastic Packet Loss" as submitted for the initial review
Controller synthesis using interval methods
No full textThis thesis investigates whether interval methods can be employed in the construction of a novel controller synthesis algorithm based on backward induction. Interval methods are methods employing interval arithmetic, which is an arithmetic defined on real-valued intervals rather than on real-valued numbers. In the controller synthesis algorithm presented in this thesis interval methods are used to determine pre-images, represent approximations of closed sets, implement operations on these sets, and solve non-linear constrained optimisation problems without the need for derivatives. While interval methods only impose modest requirements, i.e., they require that interval extensions of the difference equation describing (or approximating) the plant dynamics, cost function, and inequality constraints can be constructed, they do however suffer from the curse of dimensionality. In the presented synthesis algorithm the curse of dimensionality limits practical use to systems for which the number of states and control inputs are relatively low. The thesis can be divided into four parts: - The first part of this thesis (Chapters 2, 3 and 4) introduces interval arithmetic, a number of interval methods, and set computation. - In the second part of the thesis (Chapter 5) the controller synthesis algorithm is presented and implemented using the concepts presented in the first part of the thesis. - In the third part of the thesis (Chapter 6) the implemented synthesis algorithm is successfully used to generate, and test the viability of, controllers for two benchmark problems. - The fourth part (Chapter 7) concludes the thesis, gives recommendations for improving the synthesis algorithm and suggests a number of topics worth considering for future research. In conclusion, this thesis shows that interval methods can be used to construct a controller synthesis algorithm for non-trivial control problems.Systems & ControlDelft Center for Systems and ControlMechanical, Maritime and Materials Engineerin
Quantitative multi-objective verification for probabilistic systems
Full text linkWe present a verification framework for analysing multiple quantitative objectives of systems that exhibit both nondeterministic and stochastic behaviour. These systems are modelled as probabilistic automata, enriched with cost or reward structures that capture, for example, energy usage or performance metrics. Quantitative properties of these models are expressed in a specification language that incorporates probabilistic safety and liveness properties, expected total cost or reward, and supports multiple objectives of these types. We propose and implement an efficient verification framework for such properties and then present two distinct applications of it: firstly, controller synthesis subject to multiple quantitative objectives; and, secondly, quantitative compositional verification. The practical applicability of both approaches is illustrated with experimental results from several large case studies
Controller Synthesis for Hyperproperties
No full textWe investigate the problem of controller synthesis for hyperproperties specified in the temporal logic HyperLTL. Hyperproperties are system properties that relate multiple execution traces. Hyperproperties can elegantly express information-flow policies like noninterference and observational determinism. The controller synthesis problem is to automatically design a controller for a plant that ensures satisfaction of a given specification in the presence of the environment or adversarial actions. We show that the controller synthesis problem is decidable for HyperLTL specifications and finite-state plants. We provide a rigorous complexity analysis for different fragments of HyperLTL and different system types: tree-shaped, acyclic, and general graphs
Controller Synthesis for Hyperproperties
No full textWe investigate the problem of controller synthesis for hyperproperties specified in the temporal logic HyperLTL. Hyperproperties are system properties that relate multiple execution traces. Hyperproperties can elegantly express information-flow policies like noninterference and observational determinism. The controller synthesis problem is to automatically design a controller for a plant that ensures satisfaction of a given specification in the presence of the environment or adversarial actions. We show that the controller synthesis problem is decidable for HyperLTL specifications and finite-state plants. We provide a rigorous complexity analysis for different fragments of HyperLTL and different system types: tree-shaped, acyclic, and general graphs
Formal Controller Synthesis via Genetic Programming
No full textThis paper presents an automatic controller synthesis method for nonlinear systems with reachability and safety specifications. The proposed method consists of genetic programming in combination with an SMT solver, which are used to synthesize both a control Lyapunov function and the modes of a switched state feedback controller. The resulting controller consists of a set of analytic expressions and a switching law based on the control Lyapunov function, which together guarantee the imposed specifications. The effectiveness of the proposed approach is shown on a 2D pendulum.Team Tamas Keviczk
Structured controller synthesis for mechanical servo-systems: Algorithms, relaxations and optimality certificates
No full textIn many application areas of mechanical servo-systems the high demands on the performance often imply a tightly tuned feedback controller, that takes dynamical interaction into account. Model-based H-optimal controller synthesis is a well-suited technique for this purpose. However, the state-of-the-art synthesis approach yields controllers with high McMillan degree that can not be implemented in real-time at high sampling-rates, because of the limited computational capacity. This motivates to constrain the McMillan degree of the controller. The aim of this thesis is to provide numerical tools for H-optimal degree constrained (or otherwise structured) controller synthesis. For this problem we have developed relaxations that are based on Sum-Of-Squares polynomials. Their optimal values are lower bounds on the globally optimal structured controller synthesis problem and can be computed by solving LMI problems. It is guaranteed, that the bounds converge to best achievable performance as we improve our relaxations. To make this technique feasible for plants with high McMillan degree, we proposed a computationally less demanding scheme based on partial dualization. The Sum-Of-Squares relaxations have also been applied to robust polynomial Semi-Definite Programs (SDPs). Also for this case a sequence of relaxations has been developed, whose optimal values converge from below to the optimal value of the robust SDP. Furthermore for the structured controller synthesis problem an Interior Point algorithm has been developed. It is shown how this algorithm can be made more efficient, by exploiting the control-theoretic characteristics of the problem. Conditions have been derived to verify local optimality of the optimized controller. Finally, it has been illustrated by real-time experiments that the algorithms described in this thesis can be used to synthesize high-performing fixed-order controllers for a new prototype of a wafer stage.Mechanical Maritime and Materials Engineerin
Substructural controller synthesis
Full text linkA decentralized design procedure which combines substructural synthesis, model reduction, decentralized controller design, subcontroller synthesis, and controller reduction is proposed for the control design of flexible structures. The structure to be controlled is decomposed into several substructures, which are modeled by component mode synthesis methods. For each substructure, a subcontroller is designed by using the linear quadratic optimal control theory. Then, a controller synthesis scheme called Substructural Controller Synthesis (SCS) is used to assemble the subcontrollers into a system controller, which is to be used to control the whole structure
Controller synthesis for probabilistic systems
No full textSupported by the DFG-Project “VERIAM ” and the DFG-NWO-Project “VOSS”. Supported by the European Research Training Network “Games”. Abstract Controller synthesis addresses the question of how to limit the internal behavior of a given implementation to meet its specification, regardless of the behavior enforced by the environment. In this paper, we consider a model with probabilism and nondeterminism where the nondeterministic choices in some states are assumed to be controllable, while the others are under the control of an unpredictable environment. We first consider probabilistic computation tree logic as specification formalism, discuss the role of strategy-types for the controller and show the NP-hardness of the controller synthesis problem. The second part of the paper presents a controller synthesis algorithm for automata-specifications which relies on a reduction to the synthesis problem for PCTL with fairness. 1
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