| 摘要 |
PURPOSE:To reduce the burden of the operator and to switch the control system not to cause variations in the process, by controlling with one system and switching the control valve of the other system, during the other system is in the waiting state as the spare system. CONSTITUTION:With the system A in control and with the system B in waiting as spare system, when the spare system is switched to the system A, if a change-over switch 13 selects the control from the system A to B, the output of the system A is switched from the output of a PID controller 3 to that of a limiter 4 for rate of change. The limiter 4 reduces the output value of the PID controller 3, and controls the control valve 6 to totally close it. Further, the system A is switched from automatic to manual. The system B is switched from manual to automatic, the output is switched from a signal generator to the PID controller 9, and the control valve 12 is gradually opened in response to the close operation of the control valve 6 of the system B, to suppress the variation of the process. The output of the PID controller 9 is always input to the limiter 10, to obtain the output value of the limiter 10 at start when the system B is switched to the spare system. |
