Automation system

An automation system implemented through a communication network and comprising:

• a first programmable logic controller connected to the communication network and configured to execute a first automation application;
• a first set of input/output modules controlled by the first programmable logic controller through the communication network;
• a second programmable logic controller connected to the communication network and configured to execute a second automation application;
• a second set of input/output modules controlled by the second programmable logic controller through the communication network;
• and
• a third programmable logic controller, as a backup programmable logic controller, connected to the communication network and configured to:
• detect, using a dedicated monitoring link directly connected to the third programmable logic controller and each of the first and second programmable logic controllers, when one or both of the first programmable logic controller and the second programmable logic controller are taken out of service, and
• respectively stand in for one or both the first programmable logic controller and the second programmable logic controller in response to the detection that one or both of the first programmable logic controller and the second programmable logic controller are taken out of service,
• wherein the third programmable logic controller as the backup programmable logic controller is inactive until the detection that one or both of the first programmable logic controller and the second programmable logic controller are taken out of service,
• wherein the dedicated monitoring link is distinct from the communication network,
• wherein the third programmable logic controller as the backup programmable logic controller includes memory configured to store both the first automation application and the second automation application, and, upon activation, is configured to:
• execute the first automation application to stand in for the first programmable logic controller and control the first set of input/output modules responsive to the detection that the first programmable logic controller is taken out of service, and
• execute the second automation application to stand in for the second programmable logic controller and control the second set of input/output modules responsive to the detection that the second programmable logic controller is taken out of service,
• wherein each of the first and second programmable logic controllers is configured to serve as the backup programmable logic controller when the third programmable logic controller is not serving as the backup programmable logic controller, and
• wherein the automation system has only one backup programmable logic controller active at any one time.