Falsifying Cyber-Physical Systems -- a Hybrid Optimization-Free and an
Optimization-Based Line-Search Approach
Abstract
Cyber-physical systems (CPSs) are complex and exhibit both continuous
and discrete dynamics, hence it is difficult to guarantee that they
satisfy given specifications, i.e., the properties that must be
fulfilled by the system. Falsification of temporal logic properties is a
testing approach that searches for counterexamples of a given
specification, which can be used to increase the confidence that a CPS
does fulfill its specifications. Falsification can be done using random
search methods or optimization methods. In this paper, a method based on
combining random parameters together with considering extreme
combinations of parameter values is proposed. Evaluation results on
benchmark problems show that this method performs well on many of the
problems. Optimization methods are needed when optimization-free methods
do not perform well in falsification. The efficiency of the
falsification is affected by the optimization methods used to search for
inputs that might falsify the specifications. This paper presents a new
optimization method for falsification, Line-search falsification, where
optimization is done over line segments through a vector of inputs in
the n-dimensional parameter space. The evaluation results on the
benchmark problems show that using this method improves the
falsification performance by reducing the number of simulations
necessary to falsify a specification.