ES350327A1 - Improvements in Transfer Stations for Regulating Industrial Units - Google Patents

Abstract

In a control system for an industrial process of the type comprising a plurality of regulators each controlling a respective variable of the process under the supervision of a digital computer which is connected to the regulators in a numerical multiplex manner, Fig. 4 (not shown), a respective transfer station 3 is provided for the regulation of each variable and comprises a first regulating loop including the computer 2 and a storage circuit 31 and a second regulating loop K1, 33 with proportional action which produces a signal V to control the variable of the process 4. The computer 2 is fed with a set-point signal Co representative of the desired value of the variable, with a signal M representative of the measured value of the variable and with the co-efficient K2 of integral action which is related to the coefficient K1 of proportional action of the second regulating loop. The computer is programmed to produce at fixed sampling intervals of time, a signal U which relates the parameters Co, K2 and the sum of the regulation deviations preceding the considered sampling interval, the last mention mentioned parameter being derived from the signals Co and M applied to the computer. The analogue signal U is memorized in the storage circuit 31 under the control of selection pulses S controlling the multiplexing of the different stations connected to the computer. The circuit 31 derives a modified set point signal Cm which is similar to the signal U and is applied to a comparator 32 for comparison therein with the signal M, the error signals so produced being applied to the amplifier K1 whose gain corresponds to the co-efficient Kl. Member 33 is a function switch providing for change over from automatic to manual control. The modified signal Cm is such as to compensate for the static deviation of the second regulating loop. The circuit for obtaining the signals U and Cm is described, Fig. 2 (not shown) and comprises basically a series combination of a comparator, a sampler, an amplifier and an integrator whose output feeds the storage circuit 31 through a further comparator. The circuit 31 comprises a relay controlled by the pulses S and an operational amplifier shunted by a capacitor, Fig. 5 (not shown). Should the station 3 become isolated from the computer, proportional regulation is retained at the setpoint value existing immediately prior to isolation. The operation of the second regulating loop during such isolation is discussed. Fig. 3 (not shown).