The article presents the idea of the response compression technique called signature analysis used to validate PLC software in terms of functional control safety. The method of implementation of the developed validation idea, having practical application, was presented on the simulation examples. The research results based on a selected example are presented.

The progressing automation and robotization in the industrial plants as well as the increasing complexity of the control systems of integrated machines make it necessary to constantly improve the functional safety of machines through the correct validation of safety systems. Despite the validation process carried out, the potential software errors may reveal during the usage of the machine as hidden security breaches. The article presents examples of security breaches of real machine tools and attempts to implement solutions of automated mechanisms for detecting security problems. Another aspect of the article is the new approach for detecting hidden security breaches. Using the „digital twin” model of the machine, a program that generates a sequence of events for testing control systems, and the use of a virtual reality (visual verification of the safety programs), it is possible to maximize the functional safety functions of the machine.