Advanced pressure based mass flow controllers and diagnostics
A mass flow controller for controlling flow rate comprising a controller, a valve assembly, and at least one pressure sensor, valve position sensor, and temperature sensor; wherein, at least one of the sensors is a semiconductor based sensor. The valve assembly is in fluid communication with at least one upstream location and at least one downstream location. The at least one pressure sensor is in in fluid communication with the at least one upstream location and the at least one downstream location. The valve assembly can comprise at least one piezoelectric or solenoid valve. The controller is communicable coupled with the valve assembly and at least one of the sensors. The controller determines at least one of: pressure; position; and temperature. The controller further causes an adjustment to valve stroke based on an actual fluid flow rate and at least one of the pressure, position, temperature, and a predetermined value.
1. A mass flow controller for controlling fluid flow rate, the mass flow controller comprising:
a valve assembly comprising at least one valve and being in fluid communication with at least one upstream location and at least one downstream location in a same flow path as the upstream location, wherein the at least one valve has a valve stem and a valve seat;
at least one semiconductor based pressure sensor in fluid communication with the at least one upstream location and the at least one downstream location;
a position sensor communicably coupled with the at least one valve; and
a controller communicably coupled with the valve assembly and the at least one pressure sensor, wherein the controller is configured to:
determine pressures for the upstream location and the downstream location; and
control the valve assembly to adjust a valve stroke of the at least one valve in fluid communication with the upstream and downstream locations based on an actual fluid flow rate and a desired positive fluid flow rate;
receive a value indicative of a measurement of an actual position of the valve stem from the position sensor as the valve stem moves from the valve seat following the adjustment; and
perform diagnostics on the mass flow controller by comparing the actual position of the valve stem relative to a predetermined position of the valve stem, the predetermined position of the valve stem determined in response to the desired positive fluid flow rate, the predetermined position determined from a predetermined relationship between the pressures for the upstream location and the downstream location and the position of the valve stem, and determined from a predetermined relationship between the desired positive fluid flow rate and the valve stroke.
2. The mass flow controller of claim 1 , wherein:
the at least one valve is either a piezoelectric or solenoid valve; and
the pressure sensor is at least one of an absolute pressure sensor and differential pressure sensor.
3. The mass flow controller of claim 1 , wherein the at least one semiconductor based pressure sensor comprises an absolute pressure sensor and a differential pressure sensor, and wherein both the absolute pressure sensor and the differential pressure sensor are integrated on a single cell.
4. The mass flow controller of claim 1 , wherein the position sensor is one of a semiconductor based position sensor, capacitance based position sensor, resistance based position sensor, piezo resistive based position sensor, and capacitance based position sensor.
5. The mass flow controller of claim 3 , wherein the controller:
determines a further measurement of the position of at least one valve;
causes an adjustment to valve stroke of the at least one valve based on the actual fluid flow rate and at least the further measurement, and another predetermined value.
6. The mass flow controller of claim 3 , wherein the controller:
determines the position of at least one valve; and
causes an adjustment to the position of the least one valve based on a shutdown signal and the actual fluid flow rate and at least the measurement, the predetermined value, and another predetermined value.
7. The mass flow controller of claim 1 , further comprising a position sensor and a temperature sensor, wherein the position sensor is integral to the at least one valve.
8. The mass flow controller of claim 7 , wherein at least one of the position sensor and the temperature sensor is a semiconductor based sensor.
9. The mass flow controller of claim 7 , wherein the controller:
determines position of the at least one valve;
determines temperature; and
causes an adjustment to valve stroke of at least one valve based on the actual fluid flow rate and at least the position, temperature, and the predetermined value.
10. A method of controlling fluid flow rate using a mass flow controller, the method comprising:
controlling fluid flow rate between at least one upstream location and at least one downstream location in a same flow path as the upstream location;
sensing pressure at the at least one upstream location and the at least one downstream location using at least one semiconductor based pressure sensor;
determining pressure at the at least one upstream location and the at least one downstream location;
adjusting the flow rate by causing an adjustment of a valve stroke of at least one valve in fluid communication with the upstream location and the downstream location based on an actual fluid flow rate, the pressures at the at least one upstream location and the at least one downstream location, and a predetermined valve position based on pressure a-priori information, wherein the at least one valve has a valve stem and a valve seat;
receiving measurement data from the position sensor to determine the position of the valve stem as the valve stem transitions away from the valve seat; and
performing diagnostics on the mass flow controller by comparing the actual measurement of valve displacement relative to a predetermined value of calculated valve displacement based on position a-priori information and the pressure a-priori information.
11. The method of claim 10 , wherein receiving data from the at least one semiconductor based pressure sensor comprises receiving data from an absolute pressure sensor and a differential pressure sensor, and wherein both the absolute pressure sensor and the differential pressure sensor are integrated on a single cell.
12. The method of claim 11 , wherein the position sensor is one of a semiconductor based position sensor, capacitance based position sensor, resistance based position sensor, and capacitance based position sensor.
13. The method of claim 10 , further comprising:
sensing position of the at least one valve using a position sensor integrated within the at least one valve during movement of the at least one valve away from a valve seat;
sensing temperature in a valve assembly using a temperature sensor;
determining position of the at least one valve;
determining temperature;
determining fluid flow rate; and
causing an adjustment to valve stroke of at least one valve in fluid communication with at least one of the upstream location and the at least one downstream location based on an actual fluid flow rate, temperature, and a predetermined value.
14. The method of claim 13 , wherein at least one of the position sensor and the temperature sensor is a semiconductor based position sensor.
15. The method of claim 10 , wherein the predetermined value is a fluid flow rate based, at least in part, on characteristics of a laminar flow element, and a value position provided by a signal from the position sensor.
16. A mass flow controller for controlling fluid flow rate, the mass flow controller comprising:
a valve assembly comprising at least one valve and being in fluid communication with at least one upstream location and at least one downstream location in a same flow path as the upstream location, wherein the at least one valve has a valve stem and a valve seat;
at least one position sensor communicably coupled with at least one valve of the valve assembly;
a controller communicably coupled with the valve assembly and the at least one position sensor, wherein the controller is configured to:
determine a position of the valve stem for the at least one valve in response to measurement data received from the position sensor, wherein the position of the valve stem is used to perform diagnostics on the mass flow controller by comparing an actual measurement of valve displacement during transition away from the valve seat relative to a predetermined value of calculated valve displacement, the predetermined value of calculated valve displacement determined from a predetermined relationship between the pressures for the upstream location and the downstream location and the position of the valve stem, and determined from a predetermined relationship between the desired positive fluid flow rate and the position of the valve stem; and
control the valve assembly to adjust a valve stroke of the at least one valve in fluid communication with the upstream and downstream locations based on an actual fluid flow rate, pressure measurements associated with the at least one upstream location and the at least one downstream location, the position of the valve stem, and the predetermined value.
17. The mass flow controller of claim 16 , wherein the predetermined value is based on a-priori position information.
18. The mass flow controller of claim 16 , further comprising: a semiconductor based temperature sensor;
wherein the controller:
determines position of at least one valve;
determines temperature; and
causes an adjustment to valve stroke of the at least one valve based on the actual fluid flow rate and at least the pressure measurement, the position, the temperature, and the predetermined value.