Flow ratio controllers with mass accumulation compensation and gas distribution systems utilizing mass accumulation compensation

Abstract

To provide flow ratio controllers and precision gas distribution systems.SOLUTION: A flow ratio controller includes: an inlet; an inlet pressure sensor; a first outlet and a second outlet; a first flow valve and a second flow valve; a first position sensor and a second position sensor; a first outlet pressure sensor and a second outlet pressure sensor; and a control circuit section. The control circuit section is configured to: control the first flow valve and the second flow valve on the basis of a predetermined flow ratio for the first outlet and the second outlet, an inlet pressure, a first valve position, a second valve position, a first outlet pressure, and a second outlet pressure; determine a rate of change of the inlet pressure on the basis of measurement values from the inlet pressure sensor; and on the basis of the inlet pressure and the rate of change of the inlet pressure, control the first flow valve and the second flow valve to maintain the inlet pressure within a predetermined range of a predetermined inlet pressure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [Related Applications] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 553,960, filed February 15, 2024, entitled "FLOW RATIO CONTROLLERS WITH MASS ACCUMULATION COMPENSATION AND GAS DISTRIBUTION SYSTEMS UTILIZING MASS ACCUMULATION COMPENSATION," the entirety of which is expressly incorporated herein by reference.

[0002] This disclosure relates generally to flow control, and more particularly to flow ratio controllers with mass storage compensation and gas distribution systems utilizing mass storage compensation. [Background technology]

[0003] A flow ratio controller receives one or more gas flows and distributes the flows among multiple outputs according to a defined ratio. Summary of the Invention

[0004] A flow ratio controller with mass storage compensation and a gas distribution system utilizing mass storage compensation are disclosed substantially as shown and described in connection with at least one of the drawings, and more fully set forth in the claims.

[0005] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read in conjunction with the accompanying drawings, in which like reference characters represent like parts throughout. [Brief explanation of the drawings]

[0006] [Figure 1]FIG. 1 is a block diagram of an example gas distribution system including multiple sources of gas and flow ratio controllers for controlling and distributing the gases, according to aspects of the present disclosure.

[0007] [Figure 2] FIG. 2 is a schematic diagram of an exemplary flow valve that can be used to implement each of the flow valves in the flow ratio controller of FIG. 1.

[0008] [Figure 3] FIG. 3 illustrates elements of a flow model that the control circuitry of FIG. 1 can use to control the flow valve of FIG. 2 and / or to determine the flow rate through the flow valve without the use of a dedicated flow meter.

[0009] [Figure 4A] 3 is a graph of an exemplary valve flow model that can be used by the control circuitry of FIG. 1 to control the flow valve of FIG. 2 and / or to determine the flow rate through the flow valve without the use of a dedicated flow meter. [Figure 4B] 3 is a graph of an exemplary valve flow model that can be used by the control circuitry of FIG. 1 to control the flow valve of FIG. 2 and / or to determine the flow rate through the flow valve without the use of a dedicated flow meter.

[0010] [Figure 5] 2 is a flowchart representing example machine-readable instructions that may be executed to implement the control circuitry of FIG. 1 to provide controlled delivery of gas. DETAILED DESCRIPTION OF THE INVENTION

[0011] The drawings are not necessarily to scale. Where appropriate, like or identical reference numbers are used to refer to like or identical components.

[0012] For the purposes of promoting an understanding of the principles of the claimed technology and setting out its best currently understood mode of operation, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same, it being understood, however, that no limitation on the scope of the claimed technology is intended, and it is contemplated that such changes and further modifications in the illustrated apparatus, and such further applications of the principles of the claimed technology as described therein, would typically occur to one skilled in the art to which the claimed technology pertains.

[0013] Flow ratio controllers are used to deliver precise ratios of gases to different areas of a wafer in applications such as semiconductor manufacturing. Such semiconductor manufacturing applications benefit from faster response times, repeatable results, and consistent results, in addition to cost-effectiveness. Conventional flow ratio controllers include inlet and outlet pressure sensors for each channel, as well as mass flow meters and control valves, which can introduce errors in flow ratio distribution due to differences between sensors.

[0014] The disclosed example flow ratio controller provides improved stability and accuracy as well as improved response time to changing flow rates compared to conventional flow ratio controllers. The disclosed example flow ratio controller uses piezoelectric valves and an inlet pressure sensor shared among all outlet channels of the flow ratio controller to provide accurate and repeatable gas distribution to multiple channels without using flow sensors for flow detection. Instead, the disclosed example uses a valve flow model, inlet and outlet pressure sensors, and a valve position sensor to determine the flow rate through each channel.

[0015] An exemplary flow ratio controller disclosed includes an inlet configured to receive an incoming (input) process gas flow, an inlet pressure sensor configured to measure an inlet pressure of the incoming process gas flow, a first outlet configured to output a first portion of the incoming process gas flow, a second outlet configured to output a second portion of the incoming process gas flow, a first flow valve configured to control the flow of the incoming process gas to the first outlet, a second flow valve configured to control the flow of the incoming process gas to the second outlet, a first position sensor configured to measure a first valve position of the first flow valve, and a first outlet pressure sensor configured to measure a first outlet pressure of the first outlet. The system includes a force sensor, a second position sensor configured to measure a second valve position of the second flow valve, a second outlet pressure sensor configured to measure a second outlet pressure of the second outlet, and control circuitry configured to control the first flow valve and the second flow valve based on a predetermined flow ratio for the first outlet and the second outlet, the inlet pressure, the first valve position, the second valve position, the first outlet pressure, and the second outlet pressure, determine a rate of change of the inlet pressure based on measurements from the inlet pressure sensor, and control the first flow valve and the second flow valve to maintain the inlet pressure within a predetermined range of the predetermined inlet pressure based on the inlet pressure and the rate of change of the inlet pressure.

[0016] In some example flow ratio controllers, the control circuitry is configured to: determine a first flow rate at the first outlet based on the inlet pressure, the first outlet pressure, and the first valve position without the use of a flow meter; determine a second flow rate at the second outlet based on the inlet pressure, the second outlet pressure, and the second valve position without the use of a flow meter; and control at least one of the first flow valve and the second flow valve based on the first flow rate, the second flow rate, and a predetermined flow ratio. In some example flow ratio controllers, the control circuitry is configured to control the first flow valve to create a choked flow condition through the first flow valve while the first flow valve is open, and to control the second flow valve to create a choked flow condition through the second flow valve while the second flow valve is open.

[0017] In some example flow ratio controllers, the first flow valve includes a first loss area continuous with the second loss area, and the control circuitry is configured to control the first flow valve based on calculating a first laminar flow through the first loss area and a first occlusion flow through the second loss area. In some example flow ratio controllers, the second flow valve includes a third orifice and a fourth orifice, and the control circuitry is configured to control the second flow valve based on calculating a second laminar flow through the third orifice and a second occlusion flow through the fourth orifice.

[0018] In some example flow ratio controllers, the first flow valve and the second flow valve each include a piezoelectric valve. In some example flow ratio controllers, the first position sensor and the second position sensor each include a capacitive position sensor, a strain gauge position sensor, a Hall effect position sensor, or an optical position sensor. Some example flow ratio controllers further include a manifold configured to distribute the flow of the incoming process gas to the first flow valve and the second flow valve, and the inlet pressure sensor configured to measure an inlet pressure at the manifold.

[0019] An exemplary precision gas distribution system is disclosed that includes a plurality of mass flow controllers configured to control the flow rate of respective gases to respective outlets; and a flow ratio controller configured to receive gas from the mass flow controllers via an inlet, control delivery of respective portions of the gas to the plurality of outlets of the flow ratio controller by controlling the plurality of flow valves based on an inlet pressure at the inlet, valve positions of the plurality of flow valves, and outlet pressures of the plurality of outlets according to predetermined flow ratios for the plurality of outlets, determine a rate of change of the inlet pressure based on measurements from an inlet pressure sensor, and control the plurality of flow valves to maintain the inlet pressure within a predetermined range of the predetermined inlet pressure based on the inlet pressure and the rate of change of the inlet pressure.

[0020] In some example precision gas distribution systems, the flow ratio controller includes an inlet pressure sensor configured to measure an inlet pressure of an incoming process fluid flow including gas at an inlet, the plurality of outlets including a first outlet configured to discharge a first portion of the incoming process gas flow and a second outlet configured to discharge a second portion of the incoming process gas flow, and the plurality of flow valves including a first flow valve configured to control the flow of the incoming process gas to the first outlet and a second flow valve configured to control the flow of the incoming process gas to the second outlet. The flow ratio controller further includes a first position sensor configured to measure a first valve position of the first flow valve, a first outlet pressure sensor configured to measure a first outlet pressure of the first outlet, a second position sensor configured to measure a second valve position of the second flow valve, a second outlet pressure sensor configured to measure a second outlet pressure of the second outlet, and control circuitry configured to control the first flow valve and the second flow valve based on the predetermined flow ratio, the inlet pressure, the first valve position, the second valve position, the first outlet pressure, and the second outlet pressure for the first outlet and the second outlet.

[0021] In some exemplary precision fluid distribution systems, the control circuitry is configured to control the first flow valve to create a sonic flow condition through the first flow valve while the first flow valve is open, and to control the second flow valve to create a sonic flow condition through the second flow valve while the second flow valve is open. In some exemplary precision fluid distribution systems, the first flow valve includes a first loss region continuous with a second loss region, and the control circuitry is configured to control the first flow valve based on calculating a first laminar flow through the first loss region and calculating a first sonic flow through the second loss region. In some exemplary precision fluid distribution systems, the first flow valve and the second flow valve each include a piezoelectric valve. In some exemplary precision fluid distribution systems, the first position sensor and the second position sensor each include at least one of a capacitive position sensor, a strain gauge position sensor, a Hall effect position sensor, or an optical position sensor.

[0022] In some examples, the flow ratio controller includes three or more flow valves, including a first flow valve and a second flow valve, each of the three or more flow valves having an orifice, a position sensor, and an outlet pressure sensor, and the control circuitry is configured to calculate a flow rate through each of the three or more flow valves and control each of the three or more flow valves to satisfy a predetermined division ratio.

[0023] Some example precision fluid distribution systems further include a manifold configured to distribute the flow of incoming process fluid to the first flow valve and the second flow valve, wherein the inlet pressure sensor is configured to measure the inlet pressure at the manifold. Some example precision fluid distribution systems further include a temperature sensor configured to measure the temperature of the flow of incoming process gas, and the control circuitry is configured to control the first flow valve and the second flow valve based on the temperature.

[0024] 1 is a block diagram of an example gas distribution system 100 including a source of multiple gases 102a-102n and a flow ratio controller 104 for controlled distribution of the gases 102a-102n, such as a predetermined mixture of two or more gases 102a-102n. The gases 102a-102n may be different types of process gases, such as process gases for semiconductor manufacturing.

[0025] An example gas distribution system 100 includes a series of mass flow controllers 106a-106n that control the respective flow rates for each of the gases 102a-102n. The mass flow controllers 106a-106n direct each of the gases 102a-102n to a manifold 108 or other mixing volume, which feeds an inlet 110 of a flow ratio controller 104.

[0026] 1 receives respective portions of inlet process gas streams (e.g., gases 102a-102n) via inlet 110 (e.g., as a mixture) and controls the delivery of the inlet process gas streams to a series of outlets 112a-112m. As disclosed in detail below, flow ratio controller 104 controls the delivery of the inlet process gas streams according to predetermined flow ratios for the series of outlets 112a-112m by controlling a series of flow valves using a valve flow model and based on the inlet pressure at inlet 110, the valve positions of the plurality of flow valves, and the outlet pressures of the plurality of outlets 112a-112m. Inlet 110 and outlets 112a-112m can be any single type or combination of multiple types of releasable or permanent connection(s), such as threaded connections, quick-connect connections, welded or soldered connections, and / or any other suitable type(s). The outlets 112a-112m can be connected (e.g., via hoses, pipes, ducts, and / or any other rigid, semi-rigid, and / or flexible lines) to corresponding outlet locations 114a-114m from which the flow of inlet process gas should be discharged.

[0027] The example flow ratio controller 104 includes a series of flow valves 116a-116m, each controlling flow from a shared inlet 110 to a corresponding outlet 112a-112m. The inlet pressure at the inlet 110, i.e., the inlet pressure at the inlet to the flow valves 116a-116m, is measured via an inlet pressure sensor 118. As will be described in more detail with reference to FIG. 2, each of the flow valves 116a-116m includes a position sensor 120a-120m that measures the valve position of the corresponding flow valve 116a-116m.

[0028] In some examples, the flow ratio controller 104 includes a manifold that distributes the flow of the inlet process gas to the first flow valve and the second flow valve, and the inlet pressure sensor is configured to measure the pressure at the manifold.

[0029] Each gas path from the inlet 110 to one of the outlets 112a-112m is referred to herein as an "outlet channel." Each outlet channel 126a-126m includes a corresponding flow valve 116a-116m (with a corresponding position sensor 120a-120m), a corresponding outlet 112a-112m, and a corresponding outlet pressure sensor 122a-122m. The outlet pressure sensor 122a-122m measures the outlet pressure of the corresponding outlet 112a-112m (e.g., between the outlet of the flow valve 116a-116m and the outlet 112a-112m).

[0030] The example flow ratio controller 104 further includes control circuitry 124 that controls the flow valves 116a-116m to discharge gas into two or more outlet channels 126a-126m. The example control circuitry 124 can be an integrated processing system, a programmable logic controller, a general-purpose computer, a laptop computer, a tablet computer, and / or any other type of processing system configured to communicate with the sensors 120a-120m, 122a-122m and the flow valves 116a-116m of the flow ratio controller 104. For example, the control circuitry 124 includes a processor 128, a memory 130, and a storage device 132. The example processor 128 can be any general-purpose central processing unit (CPU) from any manufacturer. In some other examples, the processor 128 can include one or more specialized processing units, such as a RISC processor with an ARM core, a graphics processing unit, a digital signal processor, and / or a system-on-chip (SoC). The processor 128 executes machine-readable instructions 134, which may be stored locally in the processor (e.g., in an internal cache or on the SoC), in memory (e.g., random access memory or other volatile memory, read-only memory or other non-volatile memory such as flash memory), and / or in a storage device 132. An example storage device 132 may be a hard drive, a solid-state storage drive, a hybrid drive, a RAID array, and / or any other mass data storage device.

[0031] 1, control circuitry 124 controls flow valves 116a-116m using predetermined (e.g., stored, received) flow ratios. The predetermined flow ratios may be stored in memory 130 and / or storage device 132 and / or may be received at the processor from an external control system (e.g., via communications circuitry).

[0032] 1, the flow ratio controller 104 does not have a flow sensor that directly measures the outlet flow rate through the outlet channels 126a-126m. Instead, the example control circuitry 124 controls the flow valves 116a-116m according to one or more valve flow models. The valve flow model(s) may be stored in the memory of the control circuitry 124 or other storage device. One example valve flow model that the control circuitry 124 may use relates valve position, inlet pressure, outlet pressure, and flow rate for each example flow valve 116a-116m. The control circuitry 124 may use different valve flow models for different flow valves 116a-116m, for example, due to the different flow valves 116a-116m having different configurations.

[0033] The example flow ratio controller 104 further includes a temperature sensor 136 that measures the temperature of the gas received through the inlet 110 and / or multiple temperature sensors configured to measure the temperature of the gas distributed through the flow valves 116a-116m. In many cases, the temperatures of the gas distributed to the different outlet channels 126a-126m will be substantially equal, but the control circuitry 124 can use the measured temperature(s) to compensate or correct for flow rate and / or pressure changes.

[0034] Figure 2 is a schematic diagram of an example flow valve 200 that can be used to implement each of the flow valves 116a-116m in the flow ratio controller 104 of Figure 1. The example flow valve 200 of Figure 2 is a piezoelectric valve that includes a stacked piezoelectric actuator 202 coupled to a control plate 204 that controls the size of a gas path between a valve inlet 206 (e.g., coupled to inlet 110 in Figure 1) and a valve outlet 208 (e.g., coupled to outlet 112) in a base 210. The valve inlet 206 and the valve outlet 208 are selectively coupled via a flow channel 212 in a housing 214 of the flow valve 200.

[0035] The exemplary piezoelectric flow valve 200 is a normally open valve that allows gas to be vented to a desired location in the event of a power outage instead of being trapped within the gas distribution system 100. In other examples, the flow valve 200 is a normally closed valve.

[0036] Flow channel 212 is adjustable by controlling piezoelectric actuator 202 to move control plate 204. For example, control plate 204 can be moved away from base 210 to increase the size of flow channel 212, and can be moved toward base 210 to decrease the size of flow channel 212 and / or close flow channel 212.

[0037] The piezoelectric actuator 202 is coupled to the control plate 204 via a stem 216, rod, or other rigid joint. To detect the position of the flow valve 200, the example position sensor 120 detects the distance between the position sensor 120 and a target 218 coupled to the stem 216. When the stem 216 is actuated to move by the piezoelectric actuator 202, the target 218 moves toward and away from the position sensor 120. The position sensor 120 can be a capacitive position sensor, a strain gauge position sensor, an optical position sensor, a Hall effect sensor, and / or any other type of position sensor, and the target 218 can be a type of target appropriate for the type of position sensor 120.

[0038] The example control circuitry 124 may include multiple elements in a flow model for the valve 200. For example, the flow model may represent multiple sources of flow constraints, such as a first pressure loss region (e.g., a viscous flow region) and a second loss region (e.g., a non-viscous flow region). Figure 3 illustrates elements of a flow model that the control circuitry 124 of Figure 1 may use to control the flow valve 200 of Figure 2 and / or to determine the flow rate through the flow valve without the use of a dedicated flow meter.

[0039] Flow valve 200 of FIG. 2 and elements 302-308 of FIG. 3 may be identical for each of the example flow valves 116a-116m of FIG.

[0040] 3, the distance between the control plate 204 and the valve seat 302 controls the size of the viscous flow region 304 and the size of the inviscid flow region 306. The example inviscid flow region 306 can include an orifice 308, which can vary between different ones of the flow valves 116a-116m of FIG.

[0041] The control circuitry 124 determines the flow rate through the valve 200 by determining the flow rate through the viscous flow region 304 and the inviscid flow region 306 based on the position of the valve 200 (e.g., the position of the control plate 204 as measured by the position sensor 120), based on the inlet pressure (e.g., measured by the inlet pressure sensor 118 of FIG. 1), based on the outlet pressure (e.g., measured by the outlet pressure sensor 122 coupled to the valve outlet 208), the size of the orifice 308, and based on the properties of the gas being pumped (e.g., the viscosity, temperature, and gas density of the gas).

[0042] The control circuitry 124 determines a first pressure drop across the viscous flow region 304 using Equation 1 to determine the intermediate pressure P x and the corresponding flow rate Q vis Determine.

[0043]

number

[0044] In equation 1, Q vis is the mass flow rate through the viscous flow region 304, P is the inlet pressure (as measured by the inlet pressure sensor 118), and P xis the intermediate pressure between the viscous flow region 304 and the inviscid flow region 306, H is the distance between the control plate 204 and the valve seat 302, μ is the kinematic viscosity of the gas, w is the width of the viscous flow region 304, L is the flow path length of the viscous flow region 304, and R is the gas constant.

[0045] Control circuitry 124 further determines a second pressure drop across inviscid flow region 306 using Equation 2 (for sonic flow conditions) or Equation 3 (for subsonic flow conditions).

[0046]

number

[0047]

number

[0048] In Formula 2 and Formula 3, C d is the emission coefficient, k is the specific heat ratio of the gas, M is the molecular weight of the gas, T is the temperature of the gas, Dia is the diameter of the orifice 308, and T ref is the reference temperature, and P ref is the reference pressure and R u is the universal gas constant, and h is the distance between the control plate 204 and the valve seat 302.

[0049] Sonic flow occurs when the condition expressed in Equation 4 applies.

[0050]

number

[0051] During sonic flow, a standing shock wave forms, which restricts the flow rate through the orifice even as the upstream pressure increases relative to the downstream pressure. By operating the flow valve 200 under sonic flow conditions, the control circuitry 124 can more reliably determine the flow rate through the flow valve 200.

[0052] Using Equations 1-4, the control circuitry 124 calculates Q based on measurements of P1 (the inlet pressure) and P2 (the outlet pressure for that channel 126). vis and Q inv The intermediate pressure value P at which x Q vis and Q inv is the intermediate pressure P x The flow rate that is equal for the same value of is the flow rate through the valve 200 and therefore through the corresponding outlet channel.

[0053] In some examples, the control circuitry 124 controls the flow valves 116a-116m to operate consistently at sonic flow conditions when the flow valves 116a-116m are open, such as by controlling the pressure drop across the flow valves 200 to satisfy Equation 4. In some other examples, the control circuitry 124 can control the flow valves 116a-116m to operate at subsonic flow conditions. However, operation at subsonic flow conditions may require additional computation by the control circuitry 124.

[0054] 4A and 4B are graphs of example valve flow models 400, 402 that the control circuitry 124 of FIG. 1 can use to control the flow valve 200 of FIG. 2 and / or to determine the flow rate through the flow valve 200 without a dedicated flow meter. For example, the valve flow models 400, 402 can be stored in a database in the memory 130 and / or storage device 132 of FIG. 1. The example valve flow model 400 relates valve position (e.g., the distance between the control plate 204 and the valve seat 302) to the flow rate through the valve 200 for a given orifice size, inlet pressure, and outlet pressure. Similarly, the valve flow model 400 relates valve position to the flow rate through the valve 200 for larger orifice sizes, inlet pressures, and outlet pressures. The example memory 130 and / or storage device 132 of FIG. 1 can include additional sets of inlet and outlet pressures for each orifice size and / or sets of flow rates for different combinations of valve position, inlet pressure, and outlet pressure for each orifice size present in the series of flow valves 116a-116m.

[0055] 1, in some examples, the control circuitry 124 is further configured to compensate for changes in inlet pressure caused by changes in inlet flow rate from the gases 102a-102n (e.g., via the MFCs 106a-106n). In conventional flow control systems, changes in flow rate result in corresponding changes in inlet pressure as gas mass accumulates in pipes, ducts, manifolds, and / or other gas carriers. Conventional systems that respond to stable pressure may need to wait a significant amount of time before responding to make any necessary flow control adjustments, thereby slowing the response time of the overall gas distribution system.

[0056] The example control circuitry 124 improves response time when a change in flow rate occurs at the inlet 110 by monitoring both inlet pressures (measured by the inlet pressure sensor 118) and determining the rate of change of the inlet pressure based on the measurement by the inlet pressure sensor 118. If the rate of change of the inlet pressure increases beyond a predetermined threshold, the control circuitry 124 responds by maintaining the inlet pressure within a predetermined range of the predetermined inlet pressure. The predetermined inlet pressure may be a pressure determined by the control circuitry 124 (e.g., using Equation 4) to maintain sonic flow conditions through the flow valves 116a-116m and / or any other target pressure determined by the control circuitry 124 to achieve a desired flow rate. In some examples, the predetermined range of the rate of change of the inlet pressure is selected to maintain sufficient sensitivity to pressure changes caused by changes in flow rate while avoiding changes due to noise.

[0057] For example, if MFCs 106a-106n increase their flow rates (e.g., due to a process or recipe change), the resulting increase in flow rate causes a corresponding increase in pressure measured by inlet pressure sensor 118. Control circuitry 124 detects that the rate of change of the inlet pressure is increasing and determines a corresponding change to the position of each of flow valves 116a-116m to maintain both the predetermined flow rate and target pressure. For example, if the rate of change of pressure is higher, control circuitry 124 may determine a larger change in valve position. Conversely, if the rate of change of pressure is lower, control circuitry 124 may determine a smaller change in valve position.

[0058] Figure 5 is a flowchart illustrating example machine-readable instructions 500 that may be executed to implement control circuitry 124 of Figure 1 to provide controlled distribution of gas from outlet channels 126a-126m. Example instructions 500 are described below with reference to gas distribution system 100 of Figure 1 and valve 200 of Figure 2.

[0059] In block 502, control circuitry 124 determines flow ratios for outlet channels 126a-126m. The flow ratios may be stored in memory 130 or storage device 132 and / or received via I / O interfaces and / or communications circuitry.

[0060] In block 504, control circuitry 124 determines whether to initiate gas delivery. For example, control circuitry 124 detects that it is receiving a flow of inlet process gas from MFCs 106a-106n based on a change in inlet pressure (e.g., as measured by inlet pressure sensor 118). If gas delivery has not yet begun (block 504), control returns to block 502.

[0061] When gas distribution begins (block 504), in block 506, the control circuitry 124 determines a target flow valve position for each of the flow valves 116a-116m based on the flow valve orifice size(s), the inlet pressure, and the target outlet pressure to deliver a target flow rate for each of the outlet channels 126a-126m that corresponds to the flow ratio. For example, the control circuitry 124 references the flow models 400, 402 and / or Equations 1-4 to set the desired flow rate for each outlet channel specified in the flow ratio so that the total flow rate through the outlet channels 126a-126m is equal to the flow rate at the inlet 110. In some examples, to reduce the complexity of the target valve position calculation, the control circuitry 124 can control the flow valves 116a-116m to set sonic flow conditions.

[0062] In block 508, the control circuitry 124 controls the flow valves 116a-116m according to their respective determined valve positions. For unused outlet channels 126a-126m, the control circuitry 124 controls the corresponding flow valves 116a-116m to close. The control circuitry 124 can use closed-loop control of the piezoelectric actuators 202 based on position feedback from the position sensors 120a-120m to control the flow valves 116a-116m to the correct valve positions.

[0063] In block 510, the control circuitry 124 determines the inlet pressure and the rate of change of the inlet pressure. For example, the control circuitry 124 may receive inlet pressure data from the inlet pressure sensor 118 and calculate the rate of change of the inlet pressure. In block 512, the control circuitry 124 determines whether the inlet pressure and / or the rate of change exceeds a threshold. If the rate of change of the inlet pressure exceeds the threshold (block 512), in block 514, the control circuitry 124 adjusts the flow valve positions of all open flow valves 116a-116m to limit the rate of change of the inlet pressure. For example, the flow valve positions are adjusted to maintain a predetermined flow ratio in each of the outlet channels 126a-126m and reduce the settling time for changes in flow rate.

[0064] After adjusting the flow valve position (block 514), or if the rate of change of the inlet pressure is less than or equal to the threshold (block 512), control circuitry 124 determines whether the flow rate has changed in block 516. If the flow rate has changed (block 516), control returns to block 506 to determine a new target flow valve position.

[0065] If the flow rate ratio has changed (block 516), then control circuitry 124 determines whether gas delivery should end in block 518. If gas delivery should continue (block 518), then control returns to block 508 to continue controlling flow valves 116a-116m. If gas delivery should end (block 518), then example instruction 500 ends.

[0066] As used herein, "and / or" means any one or more of the items in the list connected by "and / or." As an example, "x and / or y" means any element of the three-element set {(x), (y), (x, y)}. In other words, "x and / or y" means "one or both of x and y." As another example, "x, y and / or z" means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, "x, y and / or z" means "one or more of x, y and z." As used herein, the term "exemplary" means serving as a non-limiting example, instance, or illustration. As used herein, the term "for example" begins a list of one or more non-limiting examples, instances, or illustrations.

[0067] Although the present method and / or system has been described with reference to certain specific embodiments, those skilled in the art will recognize that various modifications and equivalent substitutions may be made without departing from the scope of the present method and / or system. For example, blocks and / or components of the disclosed examples may be combined, divided, rearranged, and / or otherwise modified. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the scope of the present disclosure. Therefore, the present method and / or system is not limited to the particular embodiments disclosed. Instead, the present method and / or system includes all embodiments falling within the scope of the appended claims, both literally and under the doctrine of equivalents.

Claims

1. 1. A flow ratio controller comprising: an inlet configured to receive a flow of input process gas; an inlet pressure sensor configured to measure an inlet pressure of the inlet process gas flow; a first outlet configured to allow a first portion of the inlet process gas flow to exit; a second outlet configured to discharge a second portion of the inlet process gas flow; a first flow valve configured to control the flow of the inlet process gas to the first outlet; a second flow valve configured to control the flow of the inlet process gas to the second outlet; a first position sensor configured to measure a first valve position of the first flow valve; a first outlet pressure sensor configured to measure a first outlet pressure at the first outlet; a second position sensor configured to measure a second valve position of the second flow valve; a second outlet pressure sensor configured to measure a second outlet pressure at the second outlet; A control circuit unit, controlling the first flow valve and the second flow valve based on a predetermined flow ratio for the first outlet and the second outlet, the inlet pressure, the first valve position, the second valve position, the first outlet pressure, and the second outlet pressure; determining a rate of change of the inlet pressure based on measurements from the inlet pressure sensor; controlling the first flow valve and the second flow valve based on the inlet pressure and the rate of change of the inlet pressure to maintain the inlet pressure within a predetermined range of a predetermined inlet pressure; and control circuitry configured to perform A flow ratio controller comprising:

2. The control circuit unit determining a first flow rate at the first outlet based on the inlet pressure, the first outlet pressure, and the first valve position without the use of a flow meter; determining a second flow rate at the second outlet based on the inlet pressure, the second outlet pressure, and the second valve position without the use of a flow meter; controlling at least one of the first flow valve and the second flow valve based on the first flow rate, the second flow rate, and the predetermined flow rate ratio; 10. The flow ratio controller of claim 1 configured to perform:

3. The control circuit unit controlling the first flow valve to create a choked flow condition through the first flow valve while the first flow valve is open; controlling the second flow valve to create a choked flow condition through the second flow valve while the second flow valve is open; 10. The flow ratio controller of claim 1 configured to perform:

4. 2. The flow ratio controller of claim 1, wherein the first flow valve includes a first loss area contiguous with a second loss area, and the control circuitry is configured to control the first flow valve based on calculating a first laminar flow through the first loss area and calculating a first occluded flow through the second loss area.

5. 5. The flow ratio controller of claim 4, wherein the second flow valve includes a third loss area and a fourth loss area, and the control circuitry is configured to control the second flow valve based on calculating a second laminar flow through the third loss area and calculating a second occluded flow through the fourth loss area.

6. The flow ratio controller of claim 1 , wherein the first flow valve and the second flow valve each comprise a piezoelectric valve.

7. The flow ratio controller of claim 1 , wherein each of the first position sensor and the second position sensor comprises a capacitive position sensor, a strain gauge position sensor, a Hall effect position sensor, or an optical position sensor.

8. 10. The flow ratio controller of claim 1, further comprising a manifold configured to distribute the flow of the inlet process gas to the first flow valve and the second flow valve, and wherein the inlet pressure sensor is configured to measure the inlet pressure at the manifold.

9. 2. The flow ratio controller of claim 1, wherein the flow ratio controller comprises three or more flow valves including the first flow valve and the second flow valve, each of the three or more flow valves having an orifice, a position sensor, and an outlet pressure sensor, and the control circuitry is configured to calculate a flow rate through each of the three or more flow valves and control each of the three or more flow valves to satisfy a predetermined division ratio.

10. 1. A precision gas distribution system comprising: a plurality of mass flow controllers configured to control the flow rate of respective gases to respective outlets; 1. A flow ratio controller comprising: receiving the gas from the mass flow controller via an inlet; controlling delivery of respective portions of the gas to a plurality of outlets of the flow ratio controller according to predetermined flow ratios for the plurality of outlets by controlling the plurality of flow valves based on an inlet pressure at the inlet, valve positions of a plurality of flow valves, and outlet pressures of a plurality of outlets of the flow ratio controller; determining a rate of change of the inlet pressure based on measurements from an inlet pressure sensor; controlling the plurality of flow valves based on the inlet pressure and the rate of change of the inlet pressure to maintain the inlet pressure within a predetermined range of a predetermined inlet pressure; a flow ratio controller configured to perform A precision gas distribution system comprising:

11. The flow ratio controller the inlet pressure sensor configured to measure the inlet pressure of an incoming process fluid flow comprising the gas at the inlet; It is equipped with the plurality of outlets including a first outlet configured to allow a first portion of the inlet process gas flow to exit and a second outlet configured to allow a second portion of the inlet process gas flow to exit; the plurality of flow valves including a first flow valve configured to control a flow of the incoming process gas to the first outlet and a second flow valve configured to control a flow of the incoming process gas to the second outlet; The flow ratio controller a first position sensor configured to measure a first valve position of the first flow valve; a first outlet pressure sensor configured to measure a first outlet pressure at the first outlet; a second position sensor configured to measure a second valve position of the second flow valve; a second outlet pressure sensor configured to measure a second outlet pressure at the second outlet; control circuitry configured to control the first flow valve and the second flow valve based on a predetermined flow ratio for the first outlet and the second outlet, the inlet pressure, the first valve position, the second valve position, the first outlet pressure, and the second outlet pressure; 11. The precision gas distribution system of claim 10, further comprising:

12. The control circuit unit controlling the first flow valve to create a sonic flow condition through the first flow valve while the first flow valve is open; controlling the second flow valve to create a sonic flow condition through the second flow valve while the second flow valve is open; 12. The precision fluid dispensing system of claim 11 configured to perform:

13. 12. The precision fluid distribution system of claim 11, wherein the first flow valve includes a first loss area continuous with a second loss area, and the control circuitry is configured to control the first flow valve based on calculating a first laminar flow through the first orifice and calculating a first sonic flow through the second orifice.

14. 12. The precision fluid dispensing system of claim 11, wherein the first flow valve and the second flow valve each comprise a piezoelectric valve.

15. 12. The precision fluid dispensing system of claim 11, wherein each of the first position sensor and the second position sensor comprises at least one of a capacitive position sensor, a strain gauge position sensor, a Hall effect position sensor, or an optical position sensor.

16. 12. The precision fluid distribution system of claim 11, further comprising a manifold configured to distribute the flow of the incoming process fluid to the first flow valve and the second flow valve, and wherein the inlet pressure sensor is configured to measure the inlet pressure at the manifold.

17. 12. The precision fluid distribution system of claim 11, further comprising a temperature sensor configured to measure a temperature of the inlet process gas flow, and wherein the control circuitry is configured to control the first flow valve and the second flow valve based on the temperature.

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