Flow rate control apparatus and program recording medium having recorded therein program for flow rate control apparatus

A flow rate control apparatus comprising:

• a valve provided with a position sensor to measure an opening degree and disposed in a flow channel that permits passage of a fluid;
• a flow rate sensor disposed downstream of the valve and provided with a fluid resistance element, the flow rate sensor being designed to output a first flow rate;
• a first pressure sensor disposed downstream of the fluid resistance element and disposed upstream of the valve, wherein the first pressure sensor is configured to measure a first pressure of the fluid between the fluid resistance element and the valve;
• a control circuit configured to:
• store a characteristic map indicating a relationship between at least an opening degree of the valve, a differential pressure before and after the valve, and a flow rate of a fluid passing through the flow channel;
• calculate a second flow rate from the characteristic map on a basis of a measured opening degree measured by the position sensor and the first pressure being measured by the first pressure sensor;
• determine whether a flow rate of the fluid passing through the flow channel is in a stable state or a transient state;
• and
• control the valve so that the flow rate of the fluid passing through the flow channel reaches a target flow rate,
• wherein, when the flow rate is determined to be in a stable state, control an opening degree of the valve on a basis of the target flow rate and the first flow rate outputted from the flow rate sensor,
• wherein, when the flow rate is determined to be in a transient state, control an opening degree of the valve on a basis of the target flow rate and a second flow rate,
• the flow rate sensor further comprising:
• a high resistance flow channel provided with the fluid resistance element;
• a low resistance flow channel disposed in parallel to the high resistance flow channel and joined through a terminal end to the high resistance flow channel;
• and
• a switching valve to perform switching between the high resistance flow channel and the low resistance flow channel so that a fluid passes through one of the flow channels,
• wherein, when the flow rate is determined to be in a transient state, the switching valve is designed to permit passage of a fluid into the low resistance flow channel.

A flow rate control apparatus comprising:

• a valve provided with a position sensor to measure an opening degree and disposed in a flow channel that permits passage of a fluid;
• a flow rate sensor disposed upstream of the valve and provided with a fluid resistance element;
• a first pressure sensor disposed downstream of the fluid resistance element and disposed upstream of the valve, wherein the first pressure sensor is configured to measure a first pressure of the fluid between the fluid resistance element and the valve;
• a second pressure sensor disposed downstream of the valve;
• and
• a control circuit configured to:
• store a characteristic map indicating a relationship between at least an opening degree of the valve, a differential pressure before and after the valve, and a flow rate of a fluid passing through the flow channel;
• and
• control an opening degree of the valve so that a flow rate of a fluid passing through the flow channel reaches a target flow rate,
• wherein, when a target flow rate is in a transient state, determine a target opening degree from the characteristic map on a basis of the target flow rate being accepted and the first pressure measured by the first pressure sensor, and control an opening degree of the valve so that a measured opening degree measured by the position sensor reaches the target opening degree.

A memory storage device having recorded therein a program for a flow rate control apparatus comprising a valve provided with a position sensor to measure an opening degree and disposed in a flow channel that permits passage of a fluid, a flow rate sensor disposed upstream of the valve and provided with a fluid resistance element, the flow rate sensor being designed to output a first flow rate, and a first pressure sensor disposed downstream of the fluid resistance element and disposed upstream of the valve, wherein the first pressure sensor is configured to measure a first pressure of the fluid between the fluid resistance element and the valve,

• the program recording medium causing a computer to:
• store a characteristic map indicating a relationship between at least an opening degree of the valve, a differential pressure before and after the valve, and a flow rate of a fluid passing through the flow channel;
• calculate a second flow rate from the characteristic map on a basis of a measured opening degree measured by the position sensor and the first pressure measured by the first pressure sensor;
• determine whether a flow rate of a fluid passing through the flow channel is in a stable state or a transient state;
• and
• control the valve so that a flow rate of the fluid passing through the flow channel reaches a target flow rate,
• wherein, when the flow rate is determined to be in a stable state, control an opening degree of the valve on a basis of the target flow rate and the first flow rate outputted from the flow rate sensor, and
• wherein, when the flow rate is determined to be in a transient state, control an opening degree of the valve on a basis of the target flow rate and a second flow rate on a basis of a measured opening degree measured by the position sensor.