Abstract:
Lazy linear hybrid automata (LLHA) model the discrete time behavior of
control systems containing finite-precision sensors and actuators
interacting with their environment under bounded inertial delays.
In this paper, we present a symbolic technique for reachability
analysis of lazy linear hybrid automata. The model permits invariants and
guards to be nonlinear functions but requires flow values to be constants.
Assuming finite precision, flows represented by uniform linear predicates can be reduced to
those containing values from a finite set of constants. We present an abstraction hierarchy for LLHA. Our verification technique is based on bounded model
checking and k-induction for reachability analysis at different levels of the
abstraction hierarchy within an abstraction-refinement framework. The
counterexamples obtained during BMC are used to construct refinements
in each iteration. Our technique is practical and compares favorably with state-of-the-art tools,
as demonstrated on examples that include the Air Traffic Alert and Collision Avoidance System (TCAS).
Paper available in PDF format.