An efficient timestamp-based monitoring approach to test timing constraints of cyber-physical systems

Abstract

Formal specifications on temporal behavior of Cyber-Physical Systems (CPS) is essential for verification of performance and safety. Existing solutions for verifying the satisfaction of temporal constraints on a CPS are compute and resource intensive since they require buffering signals from the CPS prior to constraint checking. We present an online approach, based on Timestamp Temporal Logic (TTL), for monitoring the timing constraints in CPS. The approach reduces the computation and memory requirements by processing the timestamps of pertinent events reducing the need to capture the full data set from the signal sampling. The signal buffer size bears a geometric relationship to the dimension of the signal vector, the time interval being considered, and the sampling resolution. Since monitoring logic is typically implemented on Field Programmable Gate Arrays (FPGAs) for efficient monitoring of multiple signals simultaneously, the space required to store the buffered data becomes the limiting resource. The monitoring logic, for the timing constraints on the Flying Paster (a printing application requiring synchronization between two motors), is illustrated in this paper to demonstrate a geometric reduction in memory and computational resources in the realization of an online monitor. CCS CONCEPTS • Computer systems organization → Embedded and cyberphysical systems; Embedded software;

A calibration of timing accuracy in the NIST cyber-physical systems testbed

“…Internet and timestamp errors, which can provide useful contextual information on the clock and timestamp quality on time-dependent measurements and other applications when a reference source is unavailable in a CPS environment. To compensate for prediction errors based on imperfect models and whims of the physical world, another solution is online monitoring of the distributed system [20] [21]. This technical note documents the initial effort to build the test infrastructure and explore test methodologies for online monitoring of time errors, while striving to base the methodologies upon the foundational elements of time and frequency metrology [4][6][22] [23].…”