초록 ▼

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 magnit

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.

대표청구항 ▼

An electronic controller for use in a process control system to control the energization of an electrical actuator, said actuator being of the type having a first input which when energized causes said actuator to move in one direction and a second input which when energized causes the actuator to m

An electronic controller for use in a process control system to control the energization of an electrical actuator, said actuator being of the type having a first input which when energized causes said actuator to move in one direction and a second input which when energized causes the actuator to move in the opposite direction, and said actuator being adapted to be connected to a valve operative to vary the flow of a fluid in a controllable process thereby to control the magnitude of a predetermined parameter in said process, said controller comprising input means for receiving first and second electrical signals, said first signal being produced by a process sensor which monitors the existing magnitude of said predetermined parameter in the process being controlled and said first signal being representative of the instantaneous magnitude of the said process parameter, the said second signal being a set signal representative of a desired magnitude of said process parameter, said first and second signals each being substantially independent of the instantaneous positions of said valve and actuator, comparison means coupled to said input means for producing a process parameter error signal when there is a difference between said first and second signals, power supply means for producing a train of power pulses, means responsive to the sense of said process parameter error signal for coupling said power supply means to a selected one of said actuator inputs thereby to determine the direction of movement of said actuator and to cause said actuator to move in said direction in a series of incremental steps during the application of each of said power pulses respectively, and means responsive to the magnitude of said process parameter error signal for controlling the time duration portion of each of said power pulses which energizes said selected actuator input as said actuator repositions said valve incrementally to reduce said process parameter error signal towards zero, said last-named means including means for adjusting the rate of movement of said actuator so that, as said process parameter error signal reduces toward zero, the movement of said actuator substantially matches the time constant of the process being controlled.