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

1. 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;

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 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 a 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.

2. The flow rate control apparatus according to claim 1 , wherein the control circuit is further configured to update the characteristic map when the flow rate is determined to be in a stable state, on a basis of the first flow rate being measured by the flow rate sensor, the first pressure being measured by the first pressure sensor, and a measured opening degree being measured by the position sensor.

3. The flow rate control apparatus according to claim 1 , wherein the characteristic map indicates a relationship between a temperature of the fluid, 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.

4. The flow rate control apparatus according to claim 1 , further comprising a second pressure sensor disposed downstream of the valve,

wherein the control circuit is further configured to calculate a second flow rate from the characteristic map on a basis of a measured opening degree being measured by the position sensor, the first pressure being measured by the first pressure sensor, and a second pressure being measured by the second pressure sensor.

5. The flow rate control apparatus according to claim 4 , wherein, when the flow rate is determined to be in a stable state, the control circuit is further configured to update the characteristic map on a basis of the first flow rate being measured by the flow rate sensor, the first pressure being measured by the first pressure sensor, a second pressure being measured by the second pressure sensor, and a measured opening degree being measured by the position sensor.

6. The flow rate control apparatus according to claim 1 , wherein the flow rate sensor further comprises

an upstream-side pressure sensor disposed upstream of the fluid resistance element, wherein the control circuit is further configured

to calculate the first flow rate on a basis of an upstream-side pressure measured by the upstream-side pressure sensor and the first pressure measured by the first pressure sensor.

7. The flow rate control apparatus according to claim 1 , wherein the flow rate sensor further comprises:

a branch pipe branched from an upstream side of the fluid resistance element and joined to a downstream side of the fluid resistance element; and

a pair of winding resistances disposed in the branch pipe,

wherein the control circuit is further configured to calculate the first flow rate on a basis of output of the pair of winding resistances.

8. 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.

9. 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.

10. 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.