A watchdog device can greatly improve the overall safety of a system. We recommend to periodically reset such a watchdog from within the main time domain of the control system, e.g. the time domain which runs your actuators. Set the watchdog time to a reasonable multiple of the period of the time domain. Now, if your system gets stuck and your time domain does not run within its desired limit, the watchdog will timeout and switch off your drives. For further information about the use of a watchdog timer see Using a Watchdog.