GB1360807A - Auto-manual electrically-operable controller - Google Patents

Abstract

1360807 Auto/manual controller PRZEMYSLOWY INSTYTUT AUTOMATYKI I POMIAROW 2 Nov 1971 [16 Nov 1970] 50811/71 Heading G3R In an auto/manual controller, smooth switching is effected between a manual control, including an integrator, and an automatic control having a proportional and integral characteristic. As shown, a process variable Xwe is fed to a differential circuit D, and is compared, in summer S1 with a pre-set value X o to produce an error signal E which is fed to a proportional circuit P and integrator I, the PID circuits forming the auto controller. When the auto mode is selected, ganged contacts Sk1, Sk2, of switch Pr, are connected to contacts A, the output Z of the integrator I being fed through resistor R1 to a further integrator C, which forms part of the manual controller, and which acts as a time delay in the auto selected mode due to feedback resistor R2. A smooth auto to manual changeover is achieved since the controller output V is held by the time delay at its last value before changeover until selection of manual control, when control signals +U or -U are fed directly to integrator C via contacts R of switch Pr. Changeover from manual to auto is also smoothed because the output Z of integrator I, which acts as a time delay in the manual selected mode, follows the controller output V, due to feedback resistors R1 R2. In Fig. 2 (not shown) the integrating, proportional differential circuits and summer S2 are amplifiers with appropriate feedback elements, which may include potentiometers to vary the parameters of the automatic control.