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Flow measurement and control with bubble detectionRelated Patent Categories: Data Processing: Generic Control Systems Or Specific Applications, Specific Application, Apparatus Or Process, Hvac Control, Flow Control (e.g., Valve Or Pump Control)Flow measurement and control with bubble detection description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070191990, Flow measurement and control with bubble detection. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority under 35 U.S.C. .sctn. 119(e) to U.S. Provisional Patent Application No. 60/707,628, filed Aug. 12, 2005, entitled "Bubble Algorithm Design," which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION [0002] 1. Field of Invention [0003] The present invention relates to systems and methods for measuring and controlling liquid flow, and more specifically to systems and methods for measuring and controlling liquid flow in environments where bubbles may be present in the liquid flow. [0004] 2. Discussion of Related Art [0005] Several techniques exist for measuring a flow rate of a liquid flowing in a conduit, pipe, or tube. These include thermal flow meters, coriolis force flow meters, differential pressure flow meters, and ultrasonic flow meters. Generally, liquid flow meters sense one or more parameters of the flow that can be calibrated to correspond to the rate (e.g., volumetric or mass) of flow of the liquid. Such flow meters can be used either as passive monitors of liquid flow through a system of interest (i.e., used as a flow meter), or as a sensor element in a closed-loop feedback system that controls liquid flow in the system of interest (i.e., as a flow meter in a flow rate controller). SUMMARY OF INVENTION [0006] When a bubble enters a sensor conduit of any type of flow meter, the signal upon which the flow meter bases its flow measurement may be disturbed. This can result in spurious measurements. Where the flow meter is operating as the sensor element of a closed-loop flow controller, the closed loop system may react to the spurious signal and attempt to compensate for what it interprets as a change in the flow rate of the liquid. This can lead to instability in the controlled flow, which interferes with the purpose of the controller to provide a stable flow at a rate corresponding to a (typically user-set) setpoint. [0007] Although the presence of bubbles can affect any type of flow meter or controller (and to varying degrees), it is especially problematic for ultrasonic-type flow meters, particularly where such ultrasonic flow meters are used to measure or control relatively low flow rates (e.g., between 5 to 50 ml/min, or less). Applicants have recognized that conventional ultrasonic flow meters and flow controllers lack the ability to detect and respond to the presence of a bubble in a sensor conduit and to remain in a stable state despite the presence of the bubble in the sensor conduit, especially where they are used to measure and/or control such relatively low flow rates. [0008] Applicants have developed systems and methods for achieving stable operation of liquid flow controls even when a bubble passes through the sensor system. The systems and methods developed by applicants can minimize the effect of the bubble on liquid flow measurements or on controlled liquid flow rates. [0009] In exemplary embodiments, a liquid flow sensor system of the present invention senses a flow signal indicative of the flow rate of the liquid flowing in a sensor conduit. The system analyzes the flow signal to determine, for example, by detecting characteristic changes in the signal, whether a bubble is present in the sensor conduit. Where the system determines that a bubble is present, it may generate an alarm signal indicative of the presence of the bubble. In exemplary embodiments of a flow control system that incorporates the flow sensor as a feedback source for closed-loop control and includes bubble detection, the flow control system may respond to the detection of a bubble by temporarily freezing the flow control parameters until the bubble has exited the sensor conduit. In this way, the system may avoid instabilities in flow rate caused by the closed-loop flow control attempting to track spurious flow sensor signals caused by the presence of the bubble. [0010] In accordance with an aspect of the present invention, a method of measuring a flow rate of a liquid flowing in a liquid flow sensor is provided, the liquid flow sensor including a sensor conduit and the liquid including a plurality of bubbles formed therein. The method comprises acts of repeatedly sensing a flow signal indicative of the flow rate of the liquid flowing in the sensor conduit; determining, based upon at least one parameter of the flow signal, whether at least one bubble is disposed in the liquid within the sensor conduit; providing, in response to a determination that no bubble is disposed in the liquid within the sensor conduit, a flow rate signal indicative of the flow rate of the liquid flowing in the liquid flow sensor based upon a most recently sensed flow signal; and providing, in response to a determination that the at least one bubble is disposed in the liquid within the sensor conduit, at least one of: a) a flow rate signal based upon the most recently sensed flow signal and an alert signal indicative of a presence of the at least one bubble, and b) a flow rate signal indicative of the flow rate of the liquid flowing in the liquid flow sensor based upon other than the most recently sensed flow signal. [0011] In accordance with one embodiment wherein the liquid flow sensor comprises an ultrasonic liquid flow sensor, the at least one parameter of the flow signal comprises an ultrasonic flow signal amplitude. In accordance with this embodiment, the method may further comprise an act of calculating, responsive to the act of repeatedly sensing, a weighted sum, such as a running average, of a value of the ultrasonic flow signal amplitude, wherein the act of determining includes an act of determining whether a most recently sensed value of the ultrasonic flow signal amplitude deviates from the weighted sum by more than a determined amount. [0012] In accordance with another embodiment wherein the liquid flow sensor comprises an ultrasonic liquid flow sensor, and wherein the flow signal comprises an ultrasonic time-of-flight difference flow signal, the at least one parameter of the flow signal includes a magnitude of the ultrasonic time-of-flight difference flow signal. In accordance with a further embodiment, the act of determining includes an act of determining whether the magnitude of the ultrasonic time-of-flight difference flow signal deviates from the magnitude of a prior ultrasonic time-of-flight difference flow signal by more than a threshold value. In accordance with a still further embodiment of the present invention, the magnitude of the ultrasonic time-of-flight difference flow signal may be used in combination with detection of a bubble based upon the ultrasonic flow signal amplitude to provide early detection of the presence of a bubble in the sensor conduit. [0013] In accordance with another aspect of the present invention, a method of controlling the flow rate of a liquid through a flow conduit that is coupled to a controllable valve and a liquid flow sensor is provided. The liquid flow sensor includes a sensor conduit and the liquid includes a plurality of bubbles formed therein, and the method comprises acts of repeatedly sensing a flow signal indicative of the flow rate of the liquid flowing in the sensor conduit; determining, based upon at least one parameter of the flow signal, whether at least one bubble is disposed in the liquid within the sensor conduit; providing, in response to a determination that no bubble is disposed in the liquid within the sensor conduit, control parameters for the controllable valve based upon the most recently sensed flow signal; providing, in response to a determination that the at least one bubble is disposed in the liquid within the sensor conduit, control parameters for the controllable valve based upon other than the most recently sensed flow signal; and controlling the controllable valve according to the control parameters. [0014] In accordance with one embodiment, the method further includes an act of calculating, responsive to the act of repeatedly sensing, a weighted sum, such as a running average, of a value of the at least one parameter of the flow signal, wherein the act of determining includes an act of determining whether a most recently sensed value of the at least one parameter of the flow signal deviates from the weighted sum by more than a determined amount. In accordance with another embodiment, the act of providing control parameters based upon other than the most recently sensed flow signal includes providing the most recently provided control parameters for which it was previously determined that no bubble was disposed in the liquid within the sensor conduit. [0015] In accordance with yet a further embodiment, the method further comprises acts of waiting a predetermined period of time in response to a determination that the at least one bubble is disposed in the liquid within the sensor conduit, determining, after the predetermined period of time, whether the at least one bubble is still disposed in the liquid within the sensor conduit, based upon the at least one parameter of the flow signal, and executing, in response to a determination that the at least one bubble is still disposed in the liquid within the sensor conduit, a controlled force procedure to remove the at least one bubble from the liquid within the sensor conduit. In one embodiment, the controlled force procedure includes opening and shutting the controllable valve. [0016] In accordance with a further aspect of the present invention, a system for measuring a flow rate of a liquid flowing in a flow conduit is provided for a liquid that may include a plurality of bubbles formed therein. The system comprises a liquid flow sensor that includes a sensor conduit fluidly coupled to the flow conduit and a bubble detection module. The liquid flow sensor is configured to sense a flow rate of the liquid flowing in the sensor conduit and provide a flow signal indicative of the flow rate of the liquid flowing in the sensor conduit. The bubble detection module is coupled to the liquid flow sensor to receive the flow signal and determine, based upon at least one parameter of the flow signal, whether at least one bubble is disposed in the liquid within the sensor conduit. The bubble detection module is configured to provide, in response to a determination that no bubble is disposed in the liquid within the sensor conduit, a flow rate signal indicative of the flow rate of the liquid flowing in the liquid flow sensor based upon a most recently sensed flow signal, and to provide, in response to a determination that the at least one bubble is disposed in the liquid within the sensor conduit, at least one of: a) a flow rate signal based upon the most recently sensed flow signal and an alert signal indicative of a presence of the at least one bubble, and b) a flow rate signal indicative of the flow rate of the liquid flowing in the liquid flow sensor based upon other than the most recently sensed flow signal. [0017] In accordance with one embodiment directed to a flow controller, the system further comprises a controllable valve in fluid communication with the flow conduit, to control the flow rate of the fluid flowing in the flow conduit based upon control parameters provided to the controllable valve, and a controller, coupled to the liquid flow sensor and the controllable valve, to receive the flow signal from the liquid flow sensor and provide the control parameters to the controllable valve. In accordance with one embodiment, the bubble detection module is implemented in the controller, wherein, upon the determination that no bubble is disposed in the liquid within the sensor conduit, the controller provides the control parameters to the controllable valve based upon the most recently sensed flow signal, and wherein, upon a determination that the at least one bubble is disposed in the liquid within the sensor conduit, the controller provides the control parameters to the controllable valve based upon other than the most recently sensed flow signal. [0018] In an alternative embodiment directed to a flow controller, wherein the bubble detection module provides the flow rate signal based upon the most recently sensed flow signal and the alert signal indicative of the presence of the at least one bubble in response to the determination that the at least one bubble is disposed in the liquid within the sensor conduit, the system further comprises a controllable valve in fluid communication with the flow conduit, to control the flow rate of the fluid flowing in the flow conduit based upon control parameters provided to the controllable valve, and a controller, coupled to the bubble detection module, to receive the flow rate signal and the alert signal and provide the control parameters to the controllable valve. [0019] In a further embodiment, in response to the alert signal, the controller freezes the control parameters provided to the controllable valve at a prior value. In yet another embodiment, in response to the alert signal, the controller is configured to wait for a predetermined period of time, and upon a determination that the at least one bubble is still disposed in the liquid within the sensor conduit and the predetermined period of time has elapsed, implement a controlled force procedure to remove the at least one bubble from the liquid within the sensor conduit. BRIEF DESCRIPTION OF DRAWINGS [0020] Exemplary embodiments of systems and methods according to the present invention will be understood with reference to the accompanying drawings, which are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like designator. For purposes of clarity, not every component may be labeled in every drawing. In the drawings: Continue reading about Flow measurement and control with bubble detection... Full patent description for Flow measurement and control with bubble detection Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Flow measurement and control with bubble detection patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Flow measurement and control with bubble detection or other areas of interest. ### Previous Patent Application: Remote monitoring and servicing of computer data centers Next Patent Application: System and method for fluid regulation Industry Class: Data processing: generic control systems or specific applications ### FreshPatents.com Support Thank you for viewing the Flow measurement and control with bubble detection patent info. 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