PHAVer: algorithmic verification of hybrid systems past HyTech

Abstract

Abstract. In 1995, HyTech broke new ground as a potentially powerful tool for verifying hybrid systems -yet it has remained severely limited in its applicability to more complex systems. We address the main problems of HyTech with PHAVer, a new tool for the exact verification of safety properties of hybrid systems with piecewise constant bounds on the derivatives. Affine dynamics are handled by on-the-fly overapproximation and by partitioning the state space based on user-definable constraints and the dynamics of the system. PHAVer's exact arithmetic is robust due to the use of the Parma Polyhedra Library, which supports arbitrarily large numbers. To manage the complexity of the polyhedral computations, we propose methods to conservatively limit the number of bits and constraints of polyhedra. Experimental results for a navigation benchmark and a tunnel diode circuit show the effectiveness of the approach.

Real-Time Reachability for Verified Simplex Design

“…Reachability analysis of hybrid systems has also been extensively researched in the last 20 years [36]. Reachability analysis tools exist for classes of systems with timed [37], rectangular [38], [39], linear [17], [39], and nonlinear [40], [41] dynamics, with varying degrees of accuracy and scalability. However, to the best of our knowledge, the algorithms in earlier reachability tools were all designed for offline analysis, and not for real-time, in-the-loop computation.…”

“…This work, however, treats the reachability computation as a black-box, which may or may not complete (because it does not use a real-time reachability algorithm). Another work also uses existing reachability approaches such as PHAVer [39] in a medical safeguard system [45], and results in a system which may add safety, but only if the computation completes on time. While a theoretical upper bound on execution time may be formulated due to decidability of the particular class of hybrid automata considered [46], the implementation of PHAVer does not provide such guarantees, and it is not clear that such a bound would be usable or too pessimistic.…”

Supporting Heterogeneity in Cyber-Physical Systems Architectures

“…For model-based verification, heterogeneous abstractions have been used for specific pairs of formalisms, such as hybrid abstractions of nonlinear systems [36], [37], linear hybrid automata abstractions of linear hybrid systems [38], discrete abstractions of hybrid systems [39]- [41] and continuous abstractions of hybrid systems [42]. Our objective is to create a general framework for abstraction that applies to any set of heterogeneous formalisms.…”

Deriving simulators for hybrid Chi models

“…PHAVer (Polyhedral Hybrid Automaton Verifyer) [26] is a tool for analyzing linear hybrid automata. Currently, PHAVer is used as a verification engine for the hybrid automata obtained by the formal translation from χ specifications to hybrid automata (see [2] for more details about this translation).…”