Flow control system for medical ventilator

A method for controlling the flow of a pressurized gas through a flow control valve in a pressurized gas conduit system in response to an electrical input signal indicative of the desired flow rate comprised of the steps of:

• providing upstream and downstream electrical pressure signals from pressure measurements upstream and downstream of the flow control valve,
• providing a gas temperature electrical signal from a measurement of the temperature of the gas flowing through said flow control valve,
• generating a valve orifice signal indicative of the effective orifice area within said flow control valve,
• processing said upstream and downstream pressure signals and said gas temperature signal together with said valve orifice signal to generate a flow signal in a feedback loop indicative of the actual flow rate of gas flow through said flow control valve,
• subtracting said flow signal from said volume input signal to generate a correction signal which is indicative of the magnitude and direction of the difference between said flow signal and said volume input signal,
• forming a flow reference signal by adding said correction signal to an immediately previous flow reference signal,
• generating a control valve position signal from said flow reference signal,
• inputting said control valve position signal to valve control means for varying the effective orifice flow area in said flow control valve in response to a control valve position signal to change the flow rate through said flow control valve,
• after a predetermined short time interval repeating the steps by first generating a new flow signal and subtracting it from the then current input signal so as to continually correct the flow rate through said flow control valve based on the difference between the actual flow rate through the flow control valve and the desired flow rate;
• wherein the valve orifice signal is generated based on a second predetermined relationship using the then current control valve position signal.

A method for controlling the flow of a pressurized gas through a flow control valve in a pressurized gas conduit system in response to an electrical pressure input signal indicative of the desired pressure at a specific location in said gas conduit system comprised of the steps of:

• generating a delta pressure signal in a feedback loop indicative of the negative of the actual effective pressure at said specific location in the pressurized gas conduit system,
• adding said delta pressure signal from said pressure input signal to generate a pressure error signal which is indicative of the magnitude and direction of the difference between said pressure input signal and said actual effective pressure,
• forming a pressure flow correction signal by processing said pressure error signal,
• forming a flow reference signal by adding said pressure flow correction signal to the immediately previous flow reference signal,
• generating a control valve position signal from said flow reference signal based on a first predetermined relationship,
• inputting said control valve position signal to valve control means for varying the effective orifice flow area in said flow control valve in response to a control valve position signal to change the flow rate through said flow control valve,
• after a predetermined short time interval repeating the steps by first generating a new delta pressure signal and subtracting it from the then current pressure input signal so as to continually correct the flow rate through said flow control valve based on the difference between the measured effective pressure at said specific location and the desired pressure.

A method for controlling the flow of a pressurized gas through a flow control valve in a pressurized gas conduit system in response to electrical volume and pressure input signals indicative of the desired flow rate and the desired pressure comprised of the steps of:

• generating a flow signal in a feedback loop indicative of the actual flow rate of gas flow through said flow control valve,
• subtracting said flow signal from said volume input signal to generate a correction signal which is indicative of the magnitude and direction of the difference between said flow signal and said volume input signal,
• forming a volume flow reference signal by adding said correction signal to the immediately previous volume flow reference signal,
• generating a delta pressure signal in a feedback loop indicative of the negative of the actual effective pressure at a specific location in the pressurized gas conduit system,
• adding said delta pressure signal from said pressure input signal to generate a pressure error signal which is indicative of the magnitude and direction of the difference between said pressure input signal and said delta pressure signal,
• forming a pressure flow correction signal by processing said pressure error signal,
• forming a pressure flow reference signal by adding said pressure flow correction signal to the immediately previous pressure flow reference signal,
• comparing said pressure flow reference signal to said volume flow reference signal and allowing the larger of the two signals to become the flow reference signal,
• generating a control valve position signal from said flow reference signal based on a first predetermined relationship,
• inputting said control valve position signal to valve control means for varying the effective orifice flow area in said flow control valve in response to a control valve position signal to change the flow rate through said flow control valve,
• after a predetermined short time interval repeating the steps by first generating a new flow signal and subtracting it from the then current input signal so as to continually correct the flow rate through said flow control valve based on the difference between the actual flow rate through the flow control valve and the desired flow rate and the difference between the effective pressure at a predetermined position in the circuit and the desired pressure at that position, whichever demands the higher flow rate.

A flow control valve system for use in a pressurized gas system including:

• input means for providing a volume input signal indicative of the flow rate desired through a portion of said pressurized gas system,
• a flow control valve located within said portion of said pressurized gas system, including means for defining a flow control orifice and a movable valve element adapted to be moved so as to change the effective flow control orifice area,
• valve element drive means for moving said valve element in response to a control valve position signal to said drive means,
• gas source means for providing a source of pressurized gas to the input of said flow control valve,
• flow rate means for determining the actual flow rate through said flow control valve and generating a flow signal indicative of said actual flow rate,
• correction means for taking the difference between said flow signal and said volume input signal to generate a correction signal which is indicative of the magnitude and direction of the difference between said flow signal and said volume input signal,
• loop means for forming a flow reference signal by adding said correction signal to the immediately previous flow reference signal which has been stored,
• valve position means for generating a control valve position signal from said flow reference signal based on a first predetermined relationship and inputting said control valve position signal to said valve element drive means.

A flow control valve system for use in a pressurized gas system including:

• input means for providing a volume input signal indicative of the flow rate desired through a portion of said pressurized gas system,
• a flow control valve located within said portion of said pressurized gas system, including means for defining a flow control orifice and a movable valve element adapted to be moved so as to change the effective flow control orifice area,
• valve element drive means for moving said valve element in response to a control valve position signal to said drive means,
• gas source means for providing a source of pressurized gas to the input of said flow control valve,
• flow rate means for determining the actual flow rate through said flow control valve and generating a flow signal indicative of said actual flow rate, said flow rate means including
• pressure means for measuring the pressures of the gas upstream and downstream of said flow control valve and generating pressure signals indicative thereof,
• temperature means for measuring the temperature of the gas flowing through said flow control valve and generating a temperature signal indicative thereof,
• orifice area means for converting said control valve position signal to a valve orifice signal indicative of the effective orifice area within said flow control valve, and
• flow processing means for processing said pressure signals, temperature signal and valve orifice signal to form a signal indicative of the actual flow through said flow control valve,
• correction means for taking the difference between said flow signal and said volume input signal to generate a correction signal which is indicative of the magnitude and direction of the difference between said flow signal and said volume input signal,
• loop means for forming a flow reference signal by adding said correction signal to the immediately previous flow reference signal which has been stored,
• valve position means for generating a control valve position signal from said flow reference signal and inputting said control valve position signal to said valve element drive means.

A flow control valve system for use in a pressurized gas system including:

• input means for providing a pressure input signal indicative of a desired effective pressure at a specific location in said gas system,
• a flow control valve located within said portion of said pressurized gas system, including means for defining a flow control orifice and a movable valve element adapted to be moved so as to change the effective flow control orifice area,
• valve element drive means for moving said valve element in response to a control valve position signal to said drive means,
• gas source means for providing a source of pressurized gas to the input of said flow control valve,
• delta pressure means for generating a delta pressure signal in a feedback loop indicative of negative of the actual effective pressure at said specific location in the gas system,
• pressure correction means for comparing said delta pressure signal with said pressure input signal to generate a pressure error signal,
• pressure processing means for forming a pressure flow correction signal by processing said pressure error signal,
• pressure reference means for forming a flow reference signal by adding said pressure flow correction signal to the immediately previous flow reference signal which has been stored, and
• valve position means for generating a control valve position signal from said flow reference signal based on a first predetermined relationship and inputting said control valve position signal to said valve element drive means.

A flow control valve system for use in a pressurized gas system including:

• first input means for providing a pressure input signal indicative of a desired effective pressure at a specific location in said gas system,
• a flow control valve located within said portion of said pressurized gas system, including means for defining a flow control orifice and a movable valve element adapted to be moved so as to change the effective flow control orifice area,
• valve element drive means for moving said valve element in response to a control valve position signal to said drive means,
• gas source means for providing a source of pressurized gas to the input of said flow control valve,
• delta pressure means for generating a delta pressure signal in a feedback loop indicative of the negative of the actual effective pressure at said specific location in the gas system,
• pressure correction means for comparing said delta pressure signal with said pressure input signal to generate a pressure error signal,
• pressure processing means for forming a pressure flow correction signal by processing said pressure error signal,
• pressure reference means for forming a pressure flow reference signal by adding said pressure flow correction signal to the immediately previous pressure flow reference signal which has been stored,
• second input means for providing a volume input signal indicative of the flow rate desired through a portion of said pressurized gas system,
• flow rate means for determining the actual flow rate through said flow control valve and generating a flow signal indicative of said actual flow rate,
• correction means for comparing said flow signal with said volume input signal to generate a correction signal which is indicative of the magnitude and direction of the difference between said flow signal and said volume input signal,
• loop means for forming a volume flow reference signal by adding said correction signal to the immediately previous volume flow reference signal which has been stored,
• pressure augmentation means for comparing said volume flow reference signal to said pressure flow reference signal and allowing the larger of the two signals to become the flow reference signal,
• valve position means for generating a control valve position signal from said flow reference signal based on a first predetermined relationship and inputting said control valve position signal to said valve element drive means, and
• valve position means for generating a control valve position signal from said flow reference signal based on a first predetermined relationship and inputting said control valve position signal to said valve element drive means.