Online Reset for STL Monitoring

Online monitoring is a popular validation approach in which the temporal behavior of a system is checked to assess whether it satisfies a given specification expressed, e.g., in Signal Temporal Logic (STL). This is done by employing a monitor that, at each time point, states the specification validity: satisfied, violated, or unknown. In some settings, monitoring should continue even after a violation episode is detected, to detect possible future violation episodes. However, for a monitor just relying on STL semantics, this is not possible, as, once the specification is violated by an input signal, any continuation of the signal still violates the specification. To tackle this problem, we here propose an optimal reset technique that, at runtime, detects the end of a violation episode and shifts the evaluation of the monitor to skip such episode. In this way, the monitoring can continue to detect possible other future violation episodes. We propose a framework that integrates the reset technique with an existing monitoring approach. Experiments on two Simulink models show that the technique can effectively reset the monitor and report all the violation episodes, with a negligible overhead on the monitoring cost.

System requirement

Operating system: Linux or MacOS;
Matlab (Simulink/Stateflow) version
Breach

Installation of Breach

start matlab, set up a C/C++ compiler using the command mex -setup. (Refer to here for more details.)
navigate to home in Matlab commandline, and run InstallBreach

Note that we customized InstallBreach. It only compiles the online monitoring component. For the full functionality of Breach, please refer to the original repository

Instructions on reproduction of experiment results

The online monitoring feature is in the folder Online/. Scripts for AFC are in Online/examples/AFC_online/plot_examples.m; scripts for AT are in Online/examples/Autotrans_online/init_monitor

Configuration of mode

the variable d:
- d = 0: Mode 1--monitor only
- d = 1: Mode 2--monitor with online diagnostics
- d = 2: Mode 3--monitor with reset
For AFC: Line 23
For AT: Line 9

Input data

Select one input signal by uncommenting out one line, and commenting out the other lines.

For AFC: Line 12-21
For AT: Line 14-23

Extended experimental results

In Online/experiment/