Advanced pressure based mass flow controllers and diagnostics

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.

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.