Safety apparatus and fault detection method

摘要

A safety apparatus includes: a latch circuit which retains an inconsistent state record when input signals from a plurality of sensors are in an inconsistent state, and frees the inconsistent state record when the input signals from the plurality of sensors are all in an OFF state; and an AND circuit which performs a sensor fault determination at timing when the input signals from the plurality of sensors are all in an ON state, the sensor fault determination including determining that at least one of the plurality of sensors is failed if the latch circuit retains the inconsistent state record and determining that none of the plurality of the sensors is failed if the latch circuit retains no inconsistent state record.

主权项

1. A safety apparatus comprising:
an input signal determination unit for determining whether input signals from a plurality of sensors each detecting a safety state of equipment are all in an ON state, all in an OFF state, or in an inconsistent state between the sensors; a first latch storage unit for retaining an inconsistent state record if the input signal determination unit determines that the input signals from the plurality of sensors are in an inconsistent state, and freeing the inconsistent state record if the input signal determination unit determines that the input signals from the plurality of sensors are all in an OFF state; a sensor fault determination unit for performing a sensor fault determination at first timing when the input signal determination unit determines that the input signals from the plurality of sensors are all in an ON state, the sensor fault determination including determining that at least one of the plurality of sensors is failed if the first latch storage unit retains the inconsistent state record and determining that none of the plurality of the sensors is failed if the first latch storage unit does not retain the inconsistent state record; and an operation enable/disable unit for enabling/disabling an operation of the equipment based on the input signals from the plurality of sensors and a determination result of the sensor fault determination by the sensor fault determination unit.