PID coefficient adjustment for respiratory heater closed loop control
AssigneeSmiths Medical ASD, Inc.
InventorsCary E. McGhin, Jerry F. Wasinger
Life of this patent
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Abstract
A heater system is provided for a respiratory system having a PID feedback control in which the coefficients are adjusted, such as in a warm-up process, to correspond to a likely flow rate of gas through a chamber of heated water based on the difference between heat input and heat output in relation to a temperature set point without the need to directly monitor flow rate or humidity level. A steady-state adjustment of the coefficients based on the behavior of the measured temperature in relation to the set point is also disclosed.
Claims26
A method of controlling the heating of a breathable gas to be supplied to a patient in which a PID feedback control having a set of coefficients is used comprising:
- heating water in a chamber;
- passing the breathable gas through the chamber to heat the breathable gas;
- and
- adjusting the coefficients based on a heat differential between the heat input to the water and the heat output from the chamber in relation to a temperature set point.
A method of controlling the heating of a breathable gas to be supplied to a patient in which a PID feedback control having a set of coefficients is used comprising:
- heating water in a chamber;
- passing the breathable gas through the chamber to heat the breathable gas;
- and
- adjusting the coefficients based on a heat differential between the heat input to the water and the heat output from the chamber in relation to a temperature set point, wherein there are a plurality of sets of coefficients each corresponding to a respective band of flow rates, a first set of coefficients corresponding to a low flow rate band, a second set of coefficients corresponding to a high flow rate band, and at least a third set of coefficients corresponding to an intermediate flow rate band between the low and high flow rate bands, the method further comprising initially operating with a set of coefficients and wherein adjusting the coefficients includes selecting one of the sets of coefficients.
A method of controlling the heating of a breathable gas to be supplied to a patient in which a PID feedback control having a set of coefficients is used comprising:
- heating water in a chamber;
- passing the breathable gas through the chamber to heat the breathable gas;
- and
- adjusting the coefficients in relation to an error signal between a set point temperature and an actual measured temperature, wherein the coefficients are adjusted for a lower flow rate if a standard deviation of the error signal exceeds a minimum threshold.
A method of controlling the heating of a breathable gas to be supplied to a patient in which a PID feedback control having a set of coefficients is used comprising:
- heating water in a chamber;
- passing the breathable gas through the chamber to heat the breathable gas;
- and
- adjusting the coefficients in relation to an error signal between a set point temperature and an actual measured temperature, wherein the coefficients are adjusted for a higher flow rate if a steady-state of the error signal exceeds a minimum threshold.
Dependencies are inferred from the claim text.