System and method for flow monitoring and control

System and method for flow monitoring and control

The embodiments of the present invention are generally related to the field of flow monitoring and control, and more specifically, to monitoring and/or controlling flow within a range of flow rates.

In semiconductor manufacturing, accurate control of the fluid flow through the manufacturing tool is critical for the precise manufacture of circuits on the substrate. To control the fluid flow rate in the current semiconductor manufacturing system, a mass flow meter determines the flow rate of the fluid in the system, and if the flow rate should be adjusted, a mass flow controller opens or closes a valve accordingly. Although thermal mass flow meters are becoming more common, many current systems still rely on differential pressure mass flow meters. In a differential pressure mass flow meter, two pressure sensors read the pressure drop across a constriction, which acts as a pressure loss sensing element, which has a known area to be based on the known The principle of fluid dynamics calculates the flow rate of a gas. Using the calculated gas flow rate, the mass flow controller can adjust a valve to increase or decrease the flow rate.

Prior art systems that rely on the pressure difference between the two ends of a contraction usually have a limited operating range. More specifically, the operating range is often limited to low flow rates because the pressure difference between the two sensors becomes so small that it is almost difficult to identify compared to system noise. Therefore, for example, even if the flow controller can physically control the flow rate at a rate of 0-100 mL per second, the controller may still only be able to accurately control the flow rate at a rate of 20-100 mL per second, because Below 20 mL per second, the pressure difference from the two pressure sensors is unrecognizable.

In order to extend the working range to lower flow rates, in some prior art systems, a constriction with a smaller cross-sectional area is used to increase the pressure difference induced. Although this may allow the flow meter to detect lower flow rates, the use of a more restrictive constriction reduces the maximum flow capacity of the flow meter for a given fluid supply pressure and it is often an unsatisfactory solution. Program.

The embodiments of the present invention provide a system and method for flow monitoring and control, which reduce the defects of the previously developed flow monitoring and control system and method. More specifically, the embodiment of the present invention provides a flow control device that can use a single pressure sensor to control the flow.

Embodiments of the present invention may also include a flow control device, which can determine whether a change that may require recalibration of the flow control device occurs. In one embodiment of the present invention, a controller can monitor the fluctuation of a pressure sensor (for example, a downstream pressure sensor). If the fluctuation exceeds a predetermined amount, the controller can generate an alarm indicating that the flow device may have to be recalibrated.

An embodiment of the present invention may include a flow control device including an inlet; an outlet in fluid communication with the inlet; a pressure loss element formed between the inlet and the outlet, and formed with the inlet and the outlet Fluid communication; a pressure sensor that must be located upstream of the pressure loss element, which is configured to measure the first pressure of the fluid flowing through the flow control device; a pressure sensor that must be downstream of the pressure loss element, which is configured to measure the first pressure of the fluid flowing through the flow control device; To measure the second pressure of the fluid flowing through the flow control device; and a controller coupled to the first pressure sensor and the second pressure sensor to generate a valve drive signal. During a first operating mode, the controller can generate a valve control signal based on the difference between the first pressure and the second pressure. During a second operation mode, the controller can also generate a valve control signal based on the measured pressure at a specific pressure sensor. The operation mode can be automatically switched based on a predetermined parameter (for example, a preset difference, a preset pressure at one of the sensors, fluctuations in the readings of a particular sensor, or other parameters).

Another embodiment of the present invention may include a computer program product including a set of computer instructions, the set of computer instructions is stored on at least one computer-readable medium and can be executed by at least one processor to: receive a first pressure Receive a measurement of a second pressure; operate according to a first mode of operation, wherein the computer instructions are executable to calculate a flow rate based on the difference between the first pressure and the second pressure; Operate according to a second operation mode, wherein the computer instructions are executable to calculate the flow rate based on the measured pressure at a specific pressure sensor; and based on a predetermined parameter in the first operation mode and the second operation Switch between modes.

Another embodiment of the present invention may include measuring a first pressure; measuring a second pressure; in the first operating mode, generating a valve control signal based on the difference between the first pressure and the second pressure; In the second operation mode, the valve control signal is generated based on the measured pressure at a specific pressure sensor; and the first operation mode and the second operation mode are switched according to a predetermined parameter.

Another embodiment of the present invention may include a set of computer commands that are executable to receive pressure measurements from a sensor, monitor the fluctuations of the pressure measurements, compare the fluctuations with a predetermined limit, and if the fluctuations are greater than The predetermined limit generates an alarm.

Another embodiment of the present invention may include a set of computer instructions executable to receive upstream pressure from an upstream sensor that must be located upstream of a pressure loss element, and receive a downstream pressure amount from downstream of the pressure loss element Measure, monitor the valve position of a valve, determine the difference between the measured pressures, and determine a control resolution based on the difference between the measured pressures, the valve position, and a valve resolution.

Another embodiment of the present invention may include a method for monitoring flow, which includes measuring a first pressure; measuring a second pressure; in the first operating mode, based on the difference between the first pressure and the second pressure And determine a flow rate; in the second operation mode, determine the flow rate based on the measured pressure at a specific pressure sensor; and determine the flow rate based on a predetermined parameter between the first operation mode and the second operation mode Switch between.

Another embodiment of the present invention may include a computer program product including a set of computer instructions, the set of computer instructions is stored on at least one computer-readable medium and can be executed by at least one processor to: receive a first pressure Measurement of; receiving a measurement of a second pressure; operating according to a first mode of operation, wherein the computer instructions are executable to generate a valve control signal based on the difference between the first pressure and the second pressure Operate according to a second operating mode, wherein the computer instructions are executable to generate the valve control signal based on the measured pressure at a specific pressure sensor; and according to a predetermined parameter in the first operating mode and the first Switch between two operating modes.

Another embodiment of the present invention includes a flow control device including an inlet; an outlet in fluid communication with the inlet; a first pressure sensor, which may be the only pressure sensor of the fluid control device; and a The controller coupled to the pressure sensor. The controller can be configured to generate a valve control signal based on the measured pressure at a single pressure sensor (ie, the first pressure sensor of the fluid control device).

Another embodiment of the present invention includes a method for adjusting the flow rate through a flow control device based on a measurement from a single pressure sensor, the method comprising measuring the pressure at a first pressure sensor, based on The pressure measurement from the first pressure sensor and a set of calibration parameters calculate a flow rate, compare the flow rate with a set point; and generate a valve control signal based on the difference between the calculated flow rate and the set point .

Another embodiment of the present invention includes a computer program product that includes a set of computer instructions, the set of computer instructions has a number of instructions, the instructions are executable to receive a pressure measurement from a first pressure sensor, based on the The pressure measurement of the first pressure sensor and a set of calibration parameters calculate a flow rate, compare the flow rate with a set point, and generate a valve control signal based on the difference between the calculated flow rate and the set point.

One of the advantages provided by the embodiments of the present invention over the prior art flow control device is to provide a wider range of flow control.

Another advantage provided by the embodiments of the present invention over prior art flow control devices is that they provide greater accuracy in measuring the flow rate at low flow rates.

Another advantage provided by the embodiments of the present invention over the prior art flow control device is to provide monitoring to indicate whether recalibration is required or whether an error has occurred.

The preferred embodiments of the present invention are illustrated in the figures, in which the same numerals are used to denote the same and corresponding parts in each figure.

Embodiments of the present invention provide a flow controller that can reduce or eliminate the problems associated with prior art flow control systems and methods. An embodiment of the present invention includes a flow controller having an upstream pressure sensor and a downstream pressure sensor. In an operating mode, the flow controller can control the flow rate based on the pressure difference between pressure measurements from the upstream and downstream sensors. In another mode of operation, the flow controller can control the flow rate based on the pressure sensed by a specific pressure sensor (such as the downstream pressure sensor). The flow controller may include logic to automatically switch between the operating modes. The first mode of operation may be associated with a higher flow rate, and the second mode of operation may be associated with a lower flow rate.

FIG. 1 is a diagram of a flow control device 30 according to an embodiment of the present invention. The flow control device 30 may include an inlet 32 for receiving a flow; an outlet 34 for guiding a flow to other elements of a flow system; a pressure loss element 36 (for example, an orifice plate, small diameter Tube, a narrow area or other pressure loss element); a pressure sensor 38 (referred to as "upstream pressure sensor") upstream of the pressure loss element 36, which is configured to measure the upstream pressure; one in the pressure loss element 36 The downstream pressure sensor 40 (referred to as "downstream pressure sensor") is configured to measure the downstream pressure; a controller 42 may include a controller 42 for determining a fluid flow rate and/or for generating a valve The processor, memory, and software commands that control the signal; and a valve 44 (for example, throttle valve, poppet valve, butterfly valve, pneumatically driven valve or other valves known in the art), which responds to valve control Signal and adjust the fluid flow.

The upstream pressure sensor 38 and the downstream pressure sensor 40 may be of capacitive type, piezoresitive type, converter type, or other types of pressure sensors known in the art. The portion of the upstream pressure sensor 38 and the downstream pressure sensor 40 exposed to the fluid flowing through the flow control device 30 may be chemically inert with respect to the fluid. The controller 42 may be coupled to the upstream pressure sensor 38, the downstream pressure sensor 40, and the valve 44 via, for example, electrical connections. The valve may include a valve drive that has components such as a microcontroller to process the valve control signal and open or close the valve 44 in response to the valve control signal.

Fluid (gas or liquid) can enter the flow control device 30 at the inlet 32, pass through the valve 44 and the pressure loss element 36, and exit the flow control device 30 at the outlet 34. The upstream pressure sensor 38 and the downstream pressure sensor 40 can generate an upstream pressure signal 46 and a downstream pressure signal 48, which can be digital or analog signals representing the pressure measurement at the upstream pressure sensor 38 and the downstream pressure sensor 40, respectively .

The controller 42 using, for example, software instructions stored on a computer-readable medium can generate a valve control signal 50 to open or close the valve 44 based on the pressure generated by the upstream pressure sensor 38 and/or the downstream pressure sensor 40 Measure the pressure to achieve the desired flow rate. According to an embodiment of the present invention, the controller 42 can determine the difference between the upstream pressure measurement and the downstream pressure measurement. The difference can be any representation of the difference between the pressure measurement at the upstream pressure sensor 38 and the downstream pressure sensor 40. For example, the difference can be expressed as a pressure value (e.g., 100 Pa) or a signal with a specific voltage value (e.g., 100 mV), or any other format that expresses the difference between the pressure measurements. The controller 42 can be based on any control scheme (for example, a proportional-integral ("PI") control scheme, a proportional-integral-derivative ("PID") control scheme, or any other control scheme known or developed in the art ) And compare the difference with a set point to generate a valve control signal 50. Based on the control signal 50, the valve 44 can be opened or closed to adjust the flow rate.

Calculating the flow rate based on the difference between the measured pressure at the upstream pressure sensor 38 and the downstream pressure sensor 40 can provide acceptable accuracy at high flow rates. However, as the flow rate decreases, the signal-to-noise ratio between the upstream pressure sensor 38 and the downstream pressure sensor 40 may become so low that it is difficult to make an accurate flow rate calculation based on the difference in measured pressure. In other words, at low flow rates, the pressure difference can become indistinguishable from noise. To solve this problem, the controller 42 according to an embodiment of the present invention can be switched to calculate the flow rate based on the pressure measured at a single flow sensor.

The controller 42 may calculate the flow rate based on the pressure sensed by a specific pressure sensor based on a known fluid dynamic equation and/or an empirical comparison of sensor readings with the flow rate established during calibration. According to an embodiment of the present invention, the flow control device 30 can be calibrated during installation to determine the correlation between the sensed pressure at a specific sensor and the flow rate in the system in which the flow control device 30 is installed. This may include calibrating the flow control device 30 to account for pressure losses caused by downstream components of the flow control device 30 that affect the calculated flow rate. Based on the correction, the controller 42 can respond to a pressure signal from a specific sensor (for example, the upstream pressure sensor 38 or the downstream pressure sensor 40) to generate a valve control signal 50 to adjust the fluid flow rate. It should be noted that when the controller 42 is generating a control signal based on the measurement of a specific sensor, other sensors may be in the "off" state or may continue to send pressure measurements to the controller 42.

Switching between calculating the flow rate based on a difference and calculating the flow rate based on the pressure measured by a specific pressure sensor can occur at any arbitrarily defined point. For example (but not limiting), the controller 42 can make the difference small enough that the measured pressure at a specific sensor drops below a predetermined level or in either sensor or both sensors Switch when the fluctuation exceeds a limit, and a single sensor can provide more accurate flow.

Therefore, an embodiment of the present invention may include a flow control device including an inlet, an outlet, a pressure loss element in fluid communication with the inlet and the outlet, an upstream pressure sensor, a downstream pressure sensor, and One controller. The upstream pressure sensor can measure upstream pressure and the downstream pressure sensor can measure downstream pressure. In the first range of flow rate, the controller can generate a valve control signal based on the difference in the measured pressure. In the second range of flow rate, the controller can generate a valve control signal based on the pressure measured at the upstream or downstream pressure sensor. The flow control device may further include a valve, which can be opened or closed in response to the valve control signal. The controller can automatically switch between the first operation mode (that is, the control signal is based on the difference) and the second operation mode (the control signal is based on the pressure at a specific sensor) at a predetermined point.

FIG. 2 is a diagram of an embodiment of the flow control device 30. The flow control device 30 may include an inlet 32 for receiving a flow; an outlet 34 for guiding a flow to other elements of a flow system; and a flow channel 35 for guiding the fluid from the inlet 32 To the outlet 34; a pressure loss element 36; an upstream pressure sensor 38; a downstream pressure sensor 40; a controller 42 for generating a valve control signal; and a valve 44 for responding to valve control Signal and adjust the fluid flow.

The controller 42 can receive signals representing the measured pressure at each sensor from the upstream pressure sensor 38 and the downstream pressure sensor 40. The signal can be an analog or digital signal, which can represent the measured pressure by a voltage level, such as a bit representing the measured pressure or any other way known in the art to represent the pressure. The controller 42 can determine the difference between the measured pressures by, for example, generating a difference signal and/or calculating a pressure difference. The controller 42 may generate a valve control signal based on the difference or based on the pressure signal received from the upstream and/or downstream pressure sensors. The valve 44 can be opened or closed in response to the received valve control signal.

FIG. 3 is a diagram of an embodiment of a controller 42. The controller 42 may include an analog-to-digital (A/D) converter 52 to receive signals from the upstream pressure sensor and the downstream pressure sensor and convert the received signals into a digital format. The processor 54 (for example, a CPU, an ASIC, or other processors known in the art) can receive a digital value representing the measured pressure from the A/D converter 52 and calculate a difference. Based on the difference or the measured pressure from the upstream or downstream sensor, the processor 54 can generate a digital control signal that indicates how much the valve should be opened or closed to adjust the fluid flow. The A/D converter 52 can convert the digital value into an analog valve control signal and send the analog valve control signal to the valve.

The processor 54 can generate the digital control signal by executing a software program. The software program may include a control algorithm, which is stored as a set of computer commands 56 in a computer-readable memory 58 (for example, EEPROM, RAM, ROM, fast Flash memory, magnetic storage, optical storage, or other computer-readable memory known in the art can be accessed by the processor 54. In one mode of operation, the control algorithm can use manipulators, calibration, and/or factory parameters to calculate digital control signals based on the difference between the measured pressures, or in another mode of operation, the control algorithm can Use the measured pressure at the upstream or downstream pressure sensor to calculate the digital control signal. The control algorithm can automatically switch between the first mode and the second mode at a predetermined point. For example, when the difference drops below a predetermined level, the control algorithm can switch from the first mode to the second mode. The processor 54 can determine whether to switch between the first operation mode and the second operation mode every cycle or according to a predetermined schedule.

The control algorithm can use any control scheme known in the art to calculate the digital control signal for a specific operation mode, including (but not limited to) PID, modified PID with compensation, or other controls known in the art Algorithm. The basic operation generates an error signal. The error signal is then corrected for the specific valve. The A/D converter 52 converts the corrected error signal from a digital format into an analog signal, and sends the obtained analog signal to a voltage-current converter, which drives the control valve to a new position.

The controller 42 may include additional input/output capabilities. For example, the controller 42 may include a serial interface to support administrative functions such as updating computer commands 56. In addition, the controller 42 may include a network interface to communicate with other flow control devices, administrative computers, or other devices capable of communicating on the network.

Computer instructions can implement the control algorithm in a variety of ways. For example, the control signal may be based on comparing a calculated value (for example, a calculated pressure value, a pressure difference value, or a calculated flow rate value) with a set point. As another example, the controller can calculate the difference between the measured pressures by using an adder to generate a difference signal instead of digitally calculating the difference between the measured pressures. In this case, the control signal in the first operating mode can be based on comparing the difference signal with a set point. In the second operating mode, the controller can compare a pressure signal with a set point instead of a calculated pressure value.

FIG. 4 is a flowchart illustrating a method of controlling flow according to an embodiment of the present invention. The method of FIG. 4 can be implemented by a controller having one or more processors that execute a set of computer instructions (eg, software programs) stored on a computer-readable medium. The controller can use many input parameters when generating a control signal, including pressure difference threshold 60, preset flow correction parameter 62, in situ flow correction parameter 64 and set point 66, and can be based on Measure the difference between pressures or the pressure at a specific sensor to calculate a flow rate. The input parameters can be stored on a computer-readable medium (for example, RAM, ROM, magnetic storage or other computer-readable medium known in the art).

The pressure difference threshold 60 can be used to determine when the controller switches between generating the control signal based on the difference between the sensed pressures or a specific sensed pressure. According to an embodiment of the present invention, the pressure difference threshold 60 can be calculated based on the downstream pressure, the differential pressure, the supply pressure, and the valve position. When determining the pressure difference threshold 60, the fluid can be allowed to flow through the flow control device until a differential pressure (ie, supply pressure) of approximately 10% of the full scale of the flow control device is reached. For example, if the supply pressure is 100 psi, the controller can adjust the valve until a differential pressure of 10 psi is reached. At this time, the downstream pressure and valve position can be measured by the controller. The downstream pressure determines the "load" of the system, and the valve position gives an indication of the supply pressure and the effective remaining range of the valve.

Using the above values, the control resolution of the flow control device can be determined as follows: Res = (dP%/(valve position%)) * valve resolution (psi/step) [EQ.1] where: dP% = as the flow rate The differential pressure as a percentage of the supply pressure of the control device, the valve position% = the percentage of valve opening; the valve resolution = the resolution of a specific valve, usually determined by the valve manufacturer.

If the control resolution determined by [EQ.1] is insufficient compared with the desired control resolution, it means that the slope is too high, and the controller can adjust the valve to achieve a higher pressure difference. When the control resolution produced by [EQ.1] is deemed sufficient, the corresponding differential pressure can be selected as the pressure differential threshold 60. This point acts as a proxy to the point where the sensor's signal-to-noise ratio prevents accurate pressure difference readings. According to an embodiment of the present invention, the determination of the pressure difference threshold 60 can be automatically performed by the controller. It should be noted that in other embodiments of the present invention, the pressure difference threshold 60 can be determined by other schemes or can be determined arbitrarily.

The in-situ flow correction parameters 64 may include parameters calculated for a specific flow control device based on the installation of the flow control device in a flow system. The in-situ flow correction parameter reflects the fact that the device downstream of the flow control device will affect the pressure sensed at the flow control device. Although this may have a small effect on the flow rate calculated based on the pressure difference, it can significantly affect the flow rate calculated from a specific pressure sensor. Therefore, a flow control device can be recalibrated after installation to establish an in-situ flow correction parameter 64 that addresses downstream devices. The in-situ calibration can be done, for example, by manually inputting specific values into the system or by automated software control device common programs. Since the controller will usually determine the flow rate based on the pressure at the specific sensor at a lower flow rate, according to an embodiment of the present invention, the correction parameters can be established based on the laminar flow of the fluid flowing through the fluid control device 64. As long as the flow rate corresponds to the laminar flow, only one compensation value is required for the compensation of fluid viscosity and downstream pressure loss to be used as the in-situ flow correction parameter 64.

The preset flow correction parameter 62 may include a parameter for calculating a flow rate based on the gas type, the configuration of the flow control device, or other parameters. The preset flow correction parameter 62 can be established according to any correction technique known in the art. Set point 66 represents the desired flow rate. The calculated flow rate can be compared with the set point 66 to determine how much the valve should be opened or closed. For example, the set point 66 can be automatically updated by a remote computer, an operator, or in any manner known in the art.

The controller can receive pressure measurements from the upstream and downstream pressure sensors in step 70, and can calculate a pressure difference in step 72. In step 74, the controller may compare the calculated pressure difference with a pressure difference threshold 60. If the calculated pressure difference is greater than the pressure difference threshold 60, the control can be passed to step 76, otherwise the control can be passed to step 78.

In step 76, the controller may use the preset flow correction parameter 62 to calculate the flow rate based on the difference between the measured pressures. This can be done according to any scheme known in the art for calculating a flow rate based on the difference in measured pressure. On the other hand, in step 78, the controller may use the in-situ flow correction parameter 64 to determine the flow rate. This can be done according to any scheme for calculating a flow rate based on a single pressure, which includes comparing the measured pressure with a calibration curve of the flow rate (e.g., stored in the memory of the controller or the controller can store Taken from other computer readable media).

In step 80, the controller may compare the calculated flow rate to a set point. If the flow rate is not equal to the set point, then in step 82, the controller may calculate an error gain based on the pressure from a specific sensor (for example, the measured pressure from a downstream sensor). Conversely, if the flow rate is equal to the set point, the controller may calculate the error gain based on the difference between the measured pressures (step 84). In step 86, the controller can convert the error gain into an analog valve control signal and communicate the valve control signal to a valve. Repeat steps 70-84.

It should be noted that in step 74, the controller determines whether to calculate the flow rate based on the difference in measured pressure or based on the pressure at a specific sensor. This determination can be made every time a flow rate is to be calculated. In another embodiment of the present invention, the determination may be made according to a predetermined schedule (for example, every 30 milliseconds). In this embodiment of the present invention, before determining whether a specific operation mode should be converted to another operation mode, the controller may calculate the flow according to the specific operation mode (for example, according to step 76 or step 78) within a predetermined period of time. rate. In addition, steps 70-78 can be performed by a mass flow meter to determine a flow rate. In this case, the pressure difference threshold 60 (or other preset parameters) can be determined arbitrarily.

As discussed in conjunction with Figure 4, by calibrating the flow control device during installation, the flow rate can be calculated based on the pressure reading from a single sensor to account for the pressure drop caused by the downstream components. If the downstream components change, the required offset (offset) may also change. This can happen if new pipes are installed, the flow control unit is moved, the downstream filter is restricted, loose pipes move during the dispensing process, or any other event that can affect the sensor readings occurs.

According to an embodiment of the present invention, one or both of the upstream and downstream sensors can be monitored using computer instructions stored in a computer-readable medium accessible by the controller to ensure that the pressure measurement of the sensor does not fluctuate to Outside the required range. For example, if the upstream pressure sensor measures .75 psi and the downstream pressure sensor measures .25 psi during a dispensing process, the controller can be configured to If the sensor reading is outside the +/-.05 psi limit (.45 to .55 psi difference), an alarm is generated and the downstream sensor is used for control. An alarm based on fluctuations in a pressure sensor can indicate that the system has changed, the flow control device needs to be recalibrated, or the flow control device is not operating normally. If the controller does not monitor fluctuations, the downstream sensor reading will increase to .5psi (indicating an increase of .25 psi pressure from the system after the controller), thereby changing the decrease in the actual flow rate (for example, 50% of calculated value).

Figure 5 is a flowchart illustrating an embodiment of a monitoring process. In step 90, the controller may receive the pressure measurement from a sensor (for example, the downstream sensor in FIG. 1). In step 92, the controller may compare the current pressure reading with one or more previous pressure readings to determine fluctuations in the pressure sensor. If the fluctuation is outside the preset range, as determined in step 93, the controller can generate an alarm in step 94. The alarm can be an email notification, an audible alarm, a visual alarm, or any other notification of error conditions known in the art. Optionally repeat steps 90-94. The monitoring process in Figure 5 can be implemented as a set of computer instructions in any flow control device capable of executing computer instructions and is not limited to the flow control device that provides multiple modes of flow control as described in conjunction with Figures 1-4.

FIG. 6 is a diagram of another embodiment of a flow control device 100. The flow control device 100 may include an inlet 102 for receiving a flow; an outlet 104 for guiding a flow to other elements of a flow system; and a pressure loss element 106 (e.g., orifice plate, small diameter Tube, narrow area or other pressure loss element); a pressure sensor 108 (referred to as "upstream pressure sensor") upstream of the pressure loss element 106, which is used to sense an upstream pressure; a pressure sensor 108 downstream of the pressure loss element 106 A pressure sensor 110 (referred to as a "downstream pressure sensor"), which is used to sense a downstream pressure; a controller 112, which is used to generate valve control signals; and a valve 114 (e.g., throttle valve, poppet valve, Butterfly valves, pneumatically driven valves or other valves known in the art), which respond to valve control signals to adjust fluid flow.

The upstream pressure sensor 108 and the downstream pressure sensor 110 may be capacitor type, piezoresistive type, converter, or other types of pressure sensors known in the art. The controller 112 may be coupled to the upstream pressure sensor 108, the downstream pressure sensor 110, and the valve 114 via, for example, electrical connections. Although not shown for simplicity, there may be intervention logic between the controller 112, the upstream pressure sensor 108, the downstream pressure sensor 110, and the valve 114. The valve 114 may further include components such as a microcontroller to process the valve control signal and open or close the valve in response to the valve control signal. The operation of the fluid control device 100 can be similar to that of the fluid control device 30 of FIG. 1, except that the fluid will flow through the pressure loss element before flowing through the valve.

It should be noted that in the embodiment of FIG. 6, since the downstream pressure sensor 110 is upstream of the valve 114, the pressure at the downstream pressure sensor 110 may fluctuate due to changes in the valve 114. Therefore, in order to determine whether the downstream system has been changed and whether it needs to be recalibrated, a third sensor can be added downstream of the valve 114. As described in conjunction with FIG. 5, the controller can monitor the fluctuation of the pressure at the third sensor, and if the fluctuation is too large, an alarm can be generated. In another embodiment, the valve position can be monitored. If the change in the valve position is greater than a predetermined amount, the controller can generate an alarm.

FIG. 7 is a diagram of a flow control device 700 according to an embodiment of the invention. The flow control device 700 may include an inlet 702 for receiving a flow; an outlet 704 for guiding a flow to other components of a flow system; a pressure sensor 708; and a controller 712, which may include Processor, memory, and software instructions for determining a fluid flow rate and/or for generating a valve control signal; and a valve 714 (for example, throttle valve, poppet valve, butterfly valve, pneumatically driven valve or Other valves known in the art) respond to valve control signals to adjust fluid flow.

The pressure sensor 708 can be a capacitor type, a piezoresistive type, a converter type, or other types of pressure sensors known in the art. The portion of the upstream pressure sensor 708 exposed to the fluid flowing through the flow control device 700 may be chemically inert with respect to the fluid. The controller 712 is coupled to the pressure sensor 708 and the valve 714 via, for example, electrical connections. The valve may include a valve driver with components such as a microcontroller to process the valve control signal and open or close the valve 714 in response to the valve control signal.

Fluid (gas or liquid) can enter the flow control device 700 at the inlet 702, pass through the valve 704, and exit the flow control device 700 at the outlet 704. The pressure sensor 708 can generate a pressure signal 716, which can be a digital or analog signal representing the pressure measurement at the pressure sensor 708.

The controller 712 using, for example, software instructions stored on a computer-readable medium can generate a valve control signal 720 to open or close the valve 714 to achieve a desired flow rate based on the pressure measured by the pressure sensor 708. According to an embodiment, the controller 712 may calculate the flow rate based on the pressure measured at a single flow sensor.

The controller 712 may calculate the flow rate based on the pressure sensed by a specific pressure sensor based on a known fluid dynamic equation and/or an empirical comparison of sensor readings with the flow rate established during calibration. According to an embodiment of the present invention, the flow control device 700 can be calibrated during installation to determine the correlation between the sensed pressure at the sensor 708 and the flow rate in the system in which the flow control device 700 is installed. This may include calibrating the flow control device 700 to account for pressure losses caused by downstream components of the flow control device 700 that affect the calculated flow rate. Based on the correction, the controller 712 can generate a valve control signal 720 in response to a pressure signal from a specific sensor (for example, the sensor 708) to adjust the fluid flow rate.

FIG. 8 is a diagram of another embodiment of the flow control device 800. The flow control device 800 may include an inlet 802 for receiving a flow; an outlet 804 for guiding a flow to other components of a flow system; a pressure sensor 810 for sensing a pressure; Controller 812, which is used to generate a valve control signal; and a valve 814 (for example, throttle valve, poppet valve, butterfly valve, pneumatically driven valve or other valves known in the art), which responds to the valve The control signal is used to adjust the fluid flow.

The pressure sensor 810 can be a capacitor type, a piezoresistive type, a converter, or other types of pressure sensors known in the art. The controller 812 may be coupled to the pressure sensor 810 and the valve 814 via, for example, an electrical connection. Although not shown for simplicity, there may be intervention logic between the controller 812, the pressure sensor 810, and the valve 814. The valve 814 may further include components such as a microcontroller to process the valve control signal and open or close the valve in response to the valve control signal. The fluid control device 800 is similar to the fluid control device 700 of FIG. 7 except that the pressure sensor is positioned downstream of the valve.

It should be noted that in the embodiment of FIG. 8, since the pressure sensor 810 is downstream of the valve 814, the pressure at the downstream pressure sensor 810 may fluctuate due to changes in the valve 814. Therefore, in order to determine whether the downstream system has changed and whether it needs to be recalibrated, an additional sensor can be added downstream of the valve 814. As described in conjunction with Figure 5, the controller can monitor pressure fluctuations at the additional sensor, and if the fluctuations are too large, an alarm can be generated. In another embodiment, the valve position can be monitored. If the change in the valve position is greater than a predetermined amount, the controller can generate an alarm.

FIG. 9 is a flowchart illustrating an embodiment of a method for flow control using a single sensor. The method of FIG. 9 can be implemented by a controller having one or more processors that execute a set of computer instructions (eg, software programs) stored on a computer-readable medium. The controller can use many input parameters (including the in-situ flow correction parameter 904) when generating a control signal. The input parameters can be stored on a computer-readable medium (for example, RAM, ROM, magnetic storage or other computer-readable medium known in the art).

The in-situ flow correction parameters 904 may include parameters calculated for a specific flow control device based on the installation of the flow control device in a flow system. The in-situ flow correction parameter reflects the fact that the device downstream of the flow control device will affect the pressure sensed at the flow control device. Although this may have a small effect on the flow rate calculated based on a pressure difference, it can significantly affect the flow rate calculated from a specific pressure sensor. Therefore, a flow control device can be recalibrated after installation to establish an in-situ flow correction parameter 904 that addresses downstream devices. The in-situ calibration can be done, for example, by manually inputting specific values into the system or by automated software control device common programs. Since the controller will generally determine the flow rate based on the pressure at a specific sensor at a lower flow rate, according to an embodiment of the present invention, the parameter 904 can be established based on the laminar flow of the fluid flowing through the fluid control device. . As long as the flow rate corresponds to the laminar flow, only one compensation value is required for the compensation of fluid viscosity and downstream pressure loss to be used as the in-situ flow correction parameter 904.

In step 910, the controller may receive pressure measurement from a pressure sensor. In step 912, the controller may use the in-situ flow correction parameter 904 to determine the flow rate. This can be done according to any scheme for calculating the flow rate based on a single pressure, including comparing the measured pressure with a calibration curve of the flow rate (for example, stored in the memory of the controller or other accessible by the controller) Computer readable media).

In step 914, the controller may compare the calculated flow rate to a set point. If the flow rate is not equal to the set point, then in step 916, the controller may calculate an error gain based on the pressure from a specific sensor. In step 918, the controller may convert the error gain into an analog valve control signal and communicate the valve control signal to a valve. If needed or necessary, you can repeat the steps in Figure 9 at will. In addition, it should be noted that control can occur based on PI control common programs, PID control common programs, or other control common programs.

Therefore, a flow control device with a single pressure sensor can control the flow in the same way as a flow control device with multiple sensors that operate according to an operation mode that uses a single sensor to control the flow. . The single pressure sensor flow controller may also include the ability to monitor the fluctuation of the pressure measurement at the single sensor (or other sensor) or the fluctuation of the valve position to generate an alarm that can indicate the change of the downstream pressure.

As mentioned above, by calibrating the flow control device during installation, the flow rate can be calculated based on the pressure reading from a single sensor to account for the pressure drop caused by the downstream components. If these downstream components change, the required compensation may also change. This can happen if a new pipe is installed, the flow control unit is moved, the downstream filter is restricted, the new pipe is moved during a dispensing process, or any other event that can affect the sensor reading occurs. If the downstream components change, the flow control unit can be recalibrated to account for the changes in the overall system (that is, the local calibration parameters can be updated).

It should be noted that the repeatability of control using a single sensor depends on the downstream pressure drop, and the repeatability usually increases as the downstream pressure drop increases. If the downstream pressure drop in a specific in-situ configuration is not enough to produce sufficient repeatability, additional pipes such as coils can be added downstream of the pressure sensor to increase the downstream pressure drop and increase repeatability.

Although the present invention has been described with reference to specific embodiments, it should be understood that these embodiments are only illustrative and the scope of the present invention is not limited to these embodiments. Many changes, modifications, additions, and improvements to the above embodiments are possible. It is expected that these changes, corrections, additions and improvements belong to the scope of the present invention described in detail in the scope of the following patent applications.

<p>30. . . Flow control device</p><p>32. . . Entrance</p><p>34. . . exit</p><p>35. . . Flow channel</p><p>36. . . Pressure loss element</p><p>38. . . Upstream pressure sensor</p><p>40. . . Downstream pressure sensor</p><p>42. . . Controller</p><p>44. . . valve</p><p>46. . . Upstream pressure signal</p><p>48. . . Downstream pressure signal</p><p>50. . . Valve control signal</p><p>52. . . Digital-to-analog converter</p><p>54. . . processor</p><p>56. . . Computer instructions</p><p>58. . . Computer readable memory</p><p>100. . . Flow control device</p><p>102. . . Entrance</p><p>104. . . exit</p><p>106. . . Pressure loss element</p><p>108. . . Upstream pressure sensor</p><p>110. . . Downstream pressure sensor</p><p>112. . . Controller</p><p>114. . . valve</p><p>700. . . Flow control device</p><p>702. . . Entrance</p><p>704. . . exit</p><p>708. . . Pressure sensor</p><p>712. . . Controller</p><p>714. . . valve</p><p>716. . . Stress signal</p><p>720. . . Valve control signal</p><p>800. . . Flow control device</p><p>802. . . Entrance</p><p>804. . . exit</p><p>810. . . Pressure sensor</p><p>812. . . Controller</p><p>814. . . valve</p>

Fig. 1 is a schematic diagram of a flow control device according to an embodiment of the present invention; Fig. 2 is a diagram of an embodiment of a flow control device; Fig. 3 is a diagram of an embodiment of a controller; 4 is a flowchart of an embodiment of a method for controlling flow; FIG. 5 is a flowchart of a method of monitoring a pressure sensor to determine whether a downstream system has changed; FIG. 6 is a flowchart of another method according to the present invention A schematic diagram of a flow control device of an embodiment; Figure 7 is a diagram of a flow control device using a single pressure sensor; Figure 8 is another embodiment of a flow control device using a single pressure sensor Figure 9; and Figure 9 is a flow chart illustrating an embodiment of using measurements from a single pressure sensor to control flow.