Automatic process controller with bumpless operation
AssigneeBeckman Instruments, Inc.
InventorsThomas M. Bleak, Paul L. Hansen
Life of this patent
Estimating the term…
Abstract
An electronic process controller is disclosed having automatically bumpless operation. Changes such as transfer between manual and automatic modes, switching between set point sources and adjustment of control parameter values are all accomplished bumplessly with the aid of a settle circuit which adjusts the automatic control signal for bumpless switching while the manual memory freezes the process control signal at its last value before the change was initiated.
Claims18
An improved automatic process controller having adjustable parameters operable in manual and automatic modes of the type having:
- automatic control means for generating an automatic control signal during the automatic mode related to the deviation of a process value signal from a set-point signal,
- manual memory means for generating an adjustable manual control signal during the manual mode,
- an output switch for selectively applying one of the control signals to the process to be controlled,
- means to cause the automatic control signal to track the signal applied to the process during the manual mode, and
- means to cause the manual control signal to track the signal applied to the process during the automatic mode, wherein the improvement comprises:
- bumpless adjust means for initiating a change in the operation of the automatic control means;
- first logic means responsive to actuation of the bumpless adjust means to operate the output switch to apply the manual control signal to the process;
- a settle circuit for causing the automatic control signal to become equal to the signal applied to the process only when actuated;
- second logic means responsive to actuation of the bumpless adjust means for generating a settle time period and for activating the settle circuit during the settle time period;
- and
- third logic means for operating the output switch to apply the automatic control signal to the process at the end of the settle time period.
The method of automatically bumplessly operating a process controller having automatic means for generating an automatic control signal and manual means for generating a manual control signal while changing the operation of the automatic means, comprising the steps of:
- applying the automatic control signal to the process to be controlled during an automatic mode while causing the manual control signal to track the signal applied to the process;
- applying the manual control signal to the process during a manual mode while causing the automatic control signal to track the signal applied to the process;
- determining a transfer period when a change is initiated that would result in a bump in the signal applied to the process;
- applying the manual control signal to the process during thhe transfer period;
- accomplishing the change during the transfer period,
- providing a settle circuit to make the automatic control signal equal to the manual control signal during the transfer period, and
- reapplying the automatic control signal to the process at the end of the transfer period.
Dependencies are inferred from the claim text.