| 摘要 |
1,201,189. Automatic control. HONEYWELL Inc. Sept.25, 1967 [Oct.25, 1966; Sept.26, 1966; June 21, 1967], No.43514/67. Heading G3R. A control signal or a stand-by signal is selected by switching means to adjust the value of a process variable, the control signal also being applied through second switching means for comparison with a desired value signal from a digital computer so that any error is effective through third switching means and an amplifier to produce the control signal, a manually controlled signal also being applied to the amplifier and all the switching means being controlled by the computer. In Fig.4, with a switch 500 in the "A" position and switches 405, 406, which may be transistors, in the "a" position, an amplifier 501, comparing the magnitude of a measured process variable with a desired value determined by the setting of a potentiometer 513, produces an error signal which is applied through an operational amplifier 88 to correct the variable by adjusting a process control element such as a valve 90. Resistance - capacity feedback associated with amplifier 88 introduces differential and integral components of control which may be modified for certain modes of control. With switch 500 in the "M" position and switches 405, 406 in the "b" position, the process variable may be controlled manually by operation of a potentiometer MANUAL. If switches 405, 406 are operated periodically between positions "a" and "b" under the control of a digital computer 87 the process variable is controlled by signals from the computer which are converted to analogue form and transferred to amplifier 88 through switches 405, 406 and the storage capacitor inter-connecting them. The output of amplifier 88 is then fed back to the computer through a switch K 3 and an analogue to digital converter 89 to eliminate error between actual and desired values of the output of amplifier 88. When in control, the computer closes a switch 522 so that a servomotor 521 controlled by the output of amplifier 501 maintains the setting of potentiometer 513 at a value corresponding to the magnitude of the process variable in readiness for smooth changeover to process control by amplifier 501. Failure of the computer causes switches K 2 , K 5 , to change over from the positions shown so that a back-up signal from a potentiometer PRESET adjusts the process control element 90 to a stand-by position. Switch 522 is also opened after a delay to prevent operation of servomotor 521, and control of the process by amplifier 501 is substituted. |
