Inlet pressure perturbation insensitive mass flow controller

Patent metadata

Field	Value
Publication number	US-10345829-B2
Application number	US-201615211249-A
Country	US
Kind code	B2
Filing date	Jul 15, 2016
Priority date	Jul 17, 2015
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

Abstract

A mass flow controller ( 10 ) comprises a fluid inlet ( 15 ) and at least one first flow meter ( 11 ) to measure a first flow rate (F 1 ) and to output a first flow signal (FS 1 ); at least one second flow meter ( 12 ) to measure a second flow (F 2 ) rate and to output a second flow signal (FS 2 ); a control device ( 13 ) connected to said first and second flow meters ( 11,12 ) and configured and arranged to generate a control signal (C); and at least one control valve ( 14 ) connected to said control device ( 13 ) to control a total flow rate (F out ) through the mass flow controller ( 10 ) in response to the control signal (C). The control signal (C) is generated as a function of both the first and second flow signals (FS 1 ,FS 2 ) such that the mass flow controller's ( 10 ) sensitivity to perturbations of said inlet pressure is minimized.

First claim

The invention claimed is:

1. A mass flow controller comprising:
a fluid inlet for supplying with an inlet pressure a fluid into said mass flow controller so as to establish a flow therethrough;
at least one first flow meter configured and arranged to measure a first flow rate and a second flow rate and to output a first flow signal FS 1 ;
at least one second flow meter configured and arranged to measure the second flow rate and to output a second flow signal FS 2 ;
a control device connected to said first and second flow meters and configured and arranged to generate a control signal;
integrated circuitry; and
at least one control valve connected to said control device and configured and arranged to control an outlet flow rate out of the mass flow controller in response to the control signal;
wherein the at least one first meter and the at least one second flow meter are of an identical type or of an identical design,
wherein the control signal is calculated from the first and second flow signals such that the mass flow controller's sensitivity to perturbations of said inlet pressure is minimized, and
wherein the integrated circuitry is configured:
to receive the first flow signal FS 1 and the second flow signal FS 2 , to calculate the control signal that is substantially independent of the inlet pressure perturbations; and
to output said control signal to the control valve, wherein the control valve is controlled using the calculated control signal.

2. The mass flow controller according to claim 1 , wherein the first flow meter has a first sensor response time constant and the second flow meter has a second sensor response time constant, wherein said first and second flow meters are constructed such that said first and second sensor response time constants are shorter than or equal to 200 milliseconds, or shorter than or equal to 100 milliseconds, or shorter than or equal to 50 milliseconds.

3. The mass flow controller according to claim 1 , wherein said first and second flow meters are constructed such that their first and second sensor response time constants are substantially equal to one another.

4. The mass flow controller according to claim 1 , wherein the first and second flow meters are thermal flow meters.

5. The mass flow controller according to claim 1 , wherein the first flow meter is arranged in a first fluid path of the mass flow controller and the second flow meter is arranged in a second fluid path of the mass flow controller, wherein the first and second fluid paths are extending separate to one another.

6. The mass flow controller according to claim 5 , wherein the first fluid path extends from the first flow meter to the control valve and wherein the second fluid path extends from the second flow meter and terminates in a dead end in the mass flow controller.

7. The mass flow controller according to claim 6 , wherein the control signal is generated on the basis of a first difference Δ 1 between the first flow signal FS 1 and the second flow signal FS 2 , under a proviso that
Δ 1 =ƒ(FS 1 (flow))− g (FS 2 ),

wherein ƒ and g are selected from the group comprising polynomial functions and an identity function and correlations stored in a lookup table.

8. The mass flow controller according to claim 1 , wherein the first flow meter is arranged in a first fluid path of the mass flow controller and the second flow meter is arranged in a second fluid path of the mass flow controller, wherein the first and second fluid paths are arranged in a series connection with respect to one another.

9. The mass flow controller according to claim 8 , wherein the control signal is generated on the basis of a second difference Δ 2 between the first flow signal FS 1 and the second flow signal FS 2 , under a proviso that
Δ 2 =ƒ(FS 2 (flow))−[ g (FS 1 (flow))−ƒ(FS 2 (flow))],

wherein ƒ and g are a selected from the group comprising polynomial functions and the identity function and correlations stored in a lookup table.

10. The mass flow controller according to claim 5 , wherein the first flow path has a first pneumatic characteristic and the second path has a second pneumatic characteristic, wherein the first and second pneumatic characteristics are substantially equal to one another.

11. The mass flow controller according to claim 1 ,
wherein the first and second flow meters are configured to sense inlet pressure shocks occurring on a time scale of equal to or less than 100 milliseconds, or equal to or less than 50 milliseconds, or equal to or of less than 5 milliseconds, and
wherein the control device is configured to keep the control valve stable during said inlet pressure shocks occurring on a time scale of equal to or less than 100 milliseconds, or equal to or less than 50 milliseconds, or equal to or of less than 5 milliseconds.

12. The mass flow controller according to claim 1 , wherein the control signal is calculated by subtracting the first flow signal FS 1 or a derivative thereof from the second flow signal FS 2 or a derivative thereof; or
wherein the control signal is calculated by subtracting the second flow signal FS 2 or a derivative thereof from the first flow signal FS 1 or a derivative thereof.

13. A non-transitory computer-readable storage medium comprising a computer program code, wherein the program code which is executable in a mass flow controller, the mass flow controller comprising:
a fluid inlet for supplying with an inlet pressure a fluid into said mass flow controller so as to establish a flow therethrough;
at least one first flow meter configured and arranged to measure a first flow rate and a second flow rate to output a first, flow signal FS 1 ;
at least one second flow meter configured and arranged to measure the second flow rate and to output a second flow signal FS 2 ;
a control device connected to said first and second flow meters and configured and arranged to generate a control signal;
integrated circuitry; and
at least one control valve connected to said control device and configured and arranged to control an outlet flow rate out of the mass flow controller in response to the control signal;
wherein the at least one first meter and the at least one second flow meter are of an identical type or of an identical design,
wherein the control signal is calculated from the first and second flow signals such that the mass flow controller's sensitivity to perturbations of said inlet pressure is minimized,
said program code, when carried out in the integrated circuitry of the mass flow controller, causes said control device:
to receive the first flow signal FS 1 and second flow signal FS 2 ;
to calculate from said first flow signal FS 1 and second flow signal FS 2 the control signal that is substantially independent of the inlet pressure perturbations: and
to output said control signal to the control valve, wherein the control valve is controlled using the calculated control signal.

14. A mass flow controller comprising:
a fluid inlet for supplying with an inlet pressure a fluid into said mass flow controller so as to establish a flow therethrough;
at least one first flow meter configured and arranged to measure a first flow rate and to output a first flow signal FS 1 ;
at least one second flow meter configured and arranged to measure a second flow rate and to output a second flow signal FS 2 ;
a control device connected to said first and second flow meters and configured and arranged to generate a control signal;
integrated circuitry; and
at least one control valve connected to said control device and configured and arranged to control an outlet flow

Assignees

• Sensirion Ag

Inventors

• Hornung Mark
• Huber Thomas
• Reibisch Philipp
• Rüegg Andreas

Classifications

• G05B2219/41303

  Flow rate valve controls speed · CPC title

• G05D16/2013 Primary

  using throttling means as controlling means · CPC title

• G05D7/0635 Primary

  by action on throttling means (G05D7/0688, G05D7/0694 take precedence) · CPC title

• G05D7/0617

  specially adapted for fluid materials · CPC title