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Browse Prior Art Database

Supervisory Analog Controller Station

IP.com Disclosure Number: IPCOM000090649D
Original Publication Date: 1969-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Liu, CC: AUTHOR

Abstract

This supervisory analog controller is coupled between a digital computer and a process to be controlled. Process control computer 10 selects one of a plurality of stations by providing a signal to close the associated switch S1... Sn. The set point signal is coupled from the computer through digital-to-analog converter DAC to one differentially connected inputs of controller amplifier 12. The set point signal is also stored in capacitor 14. The other of the differential input signals to amplifier 12 is provided by a process variable signal PV which is fed back from the process to computer 10. Amplifier 12 comprises a pair of MOS field effect transistors 16a and 16b as the input stage. This is followed by output amplifying stage 18. 1A and 1B are current sources which set the operating point of transistors 16a and 16b.

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Supervisory Analog Controller Station

This supervisory analog controller is coupled between a digital computer and a process to be controlled. Process control computer 10 selects one of a plurality of stations by providing a signal to close the associated switch S1... Sn. The set point signal is coupled from the computer through digital-to-analog converter DAC to one differentially connected inputs of controller amplifier 12. The set point signal is also stored in capacitor 14. The other of the differential input signals to amplifier 12 is provided by a process variable signal PV which is fed back from the process to computer 10. Amplifier 12 comprises a pair of MOS field effect transistors 16a and 16b as the input stage. This is followed by output amplifying stage 18. 1A and 1B are current sources which set the operating point of transistors 16a and 16b.

The output voltage from amplifier 18 is coupled to actuator 20 from which a feedback path is provided through capacitor 22 and resistor 24 to the input stage of amplifier 12 to provide a form of negative feedback which yields a differential input controller amplifier. The two-mode controller equation is generated by taking the ratio of Z1 to Z2 where Z1 = R24 + 1/j omega C22 and Z2 = R2. The set point signal and signal PV are coupled by double-pole double-throw switch 26 as differential input signals. To provide direct action in which an increase in set point value results in an increase in output current, switc...