Gerald J Cronin

US Patent:

44173121, Nov 22, 1983

Filed:

Jun 8, 1981

Appl. No.:

6/271306

Inventors:

Gerald F. Cronin - Worcester MA
Howard J. Fuller - Shrewsbury MA

Assignee:

Worcester Controls Corporation - West Boylston MA

International Classification:

G05B 1100

US Classification:

364510

Abstract:

An electronic controller is provided to control the energization of an electrical actuator to readjust a valve which controls the flow of a fluid in a controllable process. The controller is responsive to two signals, one of which is produced by a process sensor to represent the instantaneous magnitude of a predetermined process parameter and the second of which constitutes a set signal representative of a desired magnitude of the parameter. The signals are compared, and the sense of any resulting error signal is used to control the direction of movement of the actuator while the instantaneous magnitude of the error signal, during a succession of equal time intervals, is used to control the rate of movement of the actuator by controlling the extent of movement of the actuator during each of the time intervals. The actuator is jointly responsive to these two controls and moves in a series of incremental steps, the sizes of which decrease exponentially to match the process loop variable's exponential change with time, as the error signal reduces to zero.