Safety network system, safety slaves unit, safety controller and communication method and information collecting method and monitoring method for the safety network system

A safety slave unit for connecting to a safety network system constructed by connecting a safety controller and the safety slave unit through a safety network, comprising:

• a safety information transmission function for transmitting safety information for determining whether a safe state or a hazardous state prevails and an unsafety information transmission function for transmitting the unsafety information containing no safety information;
• and
• configured such that the unsafety information transmission function transmits the unsafety information on condition that the safety slave unit is in a safe state.

A safety controller adapted to be connected to a safety network system constructed by connecting the safety controller and safety slave units through a safety network, comprising:

• a fail-safe processing function for analyzing the contents of safety information, the safety information for determining whether a safe state or a hazardous state prevails, received from the safety slave units and in the case where it is determined that no safe state prevails, executing a predetermined process;
• and
• a function of estimating that the safety slave unit at the transmitting end is in a safe state in the case where unsafety information is received, the unsafety information containing no safety information.

A communication method for a safety network system constructed by connecting a safety controller and a safety slave unit to each other through a safety network, the method comprising:

• transmitting, by the safety slave unit, one of safety information for determining whether a safe state or a hazardous state prevails and unsafety information containing no safety information toward the safety controller through the safety network at an appropriate timing;
• and
• transmitting the unsafety information on condition that the safety slave unit is in a safe state.