Patent ID: 8359112
Filing Date: 2013-01-22
Classification: G05B,G06F

Abstract:
1. A pair of redundant controllers in a process control network, wherein the redundant controllers are communicatively linked to each other and to other devices of the process control network by a bus, wherein the controllers and the devices transmit process control messages over the bus, each of the redundant controllers comprising: a plurality of control areas each having a process control application program for performing process control functions, wherein each control area includes state variables that are used by the process control application program to perform the process control functions, and that is are updated when the control area executes to perform process control, and wherein values of the state variables are stored at the controller and is are not transmitted to the other devices; and a redundant communication module, wherein one redundant controller operates as a primary controller to perform process control by executing the process control applications of the control areas, and the other redundant controller operates as a backup controller, wherein at least two of the control areas of the primary controller execute at different frequencies, wherein the redundant communication module of the primary controller transmits a synchronization message to the backup controller after the process control application program of a control area executes to perform process control, the synchronization message containing values of the state variables from the control area, wherein synchronization messages for control areas having higher frequencies of execution are transmitted without waiting for the execution of control areas having lower frequencies of execution, and wherein the backup controller updates the values of the state variables of a control area of the backup controller corresponding to the executed control area of the primary controller with the values of the state variables from the synchronization message in response to receiving the synchronization message at the backup controller.