Patent ID: 8219218

Claim:
A plant controlling system that controls a process value of a plant by operating a plurality of operation targets, comprising: a velocity-type proportional-integral-derivative controlling unit configured to receive a control deviation between the process value and a control set value, and calculate and output a manipulated variable deviation for the operation targets; a switching unit configured to switch and then output the manipulated variable deviation from the velocity-type proportional-integral-derivative controlling unit to the operation targets; a plurality of manual operating units, having an integration function, that are associated with the operation targets and output either one of a manipulated variable calculated by the integration of the manipulated variable deviation output from the switching unit and a manipulated variable based on a manually set value to the respective associated operation targets based on a control mode of the operation targets; and a switch controlling unit configured to control operation of the switching unit based on the control mode of the operation targets and the manipulated variables output to the operation targets, and wherein the operation targets are operating valves, the switch controlling unit is configured to output a control signal to control operation of the switching unit based on whether the operating valves are fully opened, the operating valves are fully closed, or the operating valves are in a manual mode, and based on a use priority order that indicates the order of priority of the use of the operating valves.