Patent ID: 8671973
Filing Date: 2014-03-18
Classification: G05D,Y10T

Abstract:
1. A mass flow controller comprising, a gas flow line; a control valve to control a flow rate of a gas flowing through the gas flow line; a control module that operates in feed forward mode, without input from a flow sensor, to apply a final control signal to the control valve by adjusting, when the control valve experiences hysteresis, an ascending control signal with a hysteresis adjustment signal to generate the final control signal, and when the control valve is not experiencing hysteresis, a particular ascending control signal value places the control valve at a particular valve displacement position and the control module does not adjust the ascending control signal; an ascending control component that produces the ascending control signal responsive to a currently requested flow rate utilizing ascending valve characterization data, the ascending valve characterization data relates control signal values to corresponding valve displacement positions when the control valve does not exhibit hysteresis; a hysteresis adjustment component that selects, based upon the currently requested flow rate and a history of prior requested flow values, at least one adjustment value from hysteretic characterization data, and the hysteresis adjustment component generates the hysteresis adjustment signal utilizing the at least one adjustment value; and a memory that includes the ascending valve characterization data that remains unchanged during operation, and the memory includes the hysteretic characterization data that remains unchanged during operation and includes adjustment values to characterize differences between the control signal values when the control valve does not exhibit hysteresis and control signal values when the valve experiences hysteresis.