N:1 BACKUP SYSTEM OF HIERARCHY DECENTRALIZED SYSTEM

PURPOSE:To improve the reliability with a multi-controller system consisting of controllers set with hierarchy decentraliization and in response to the plant characteristics, by providing a backup controller to (n) units of subcontrollers. CONSTITUTION:Subloop controllers SLC32 which are provided in N areas in response to control subject processes perform the control for each function system. A master controller MC performs the integrated control of controllers SLC32. A device controller 35 is connected to the SLC32 and a backup controller 33 via internal serious buses 39 and 40 respectively and performs the control every function system in a normal state of the SLC32. The state of the controller 35 is monitored through the self-diagnosis, the diagnosis done by a controller MC31 and the controller 35. When a fault of the SLC32 is detected, this fault is informed to a switch controller 34 via lines 41, 42 and 44. Then a fault is decided by a logic. Thus a backup command is delivered to the controller 33, and a program of a faulty SLC is loaded to the controller 33. The control is carried out via the bus 40.