Positioner
AssigneeAzbil Corporation
InventorKazuhisa Inoue
Life of this patent
Estimating the term…
Abstract
A first table defines the relationship between the sliding resistance index μk of a packing gland and the ambient temperature for each type of the packing gland is provided. A second table defines control parameters corresponding to hysteresis levels for each size of the setting/operating device is provided. By repeating, at regular intervals, the acquisition of the sliding resistance index μk at present corresponding to the ambient temperature at present and the type of a packing gland from the first table and the selection of the control parameter corresponding to the size of the setting/operating device and the hysteresis level obtained from the sliding resistance index μk at present from the second table, the valve opening of the regulating valve is controlled using the selected control parameter.
Claims7
A positioner, comprising:
- a controller including a processor and configured to output, as a control output, an electric signal according to a difference between a valve opening setting value sent from a higher-level device and an actual opening value fed back from a regulating valve;
- an electric-pneumatic converting portion configured to convert the control output from the controller to an air pressure and outputting the air pressure to a setting/operating device of the regulating valve;
- a characteristic value/ambient temperature relationship non-transitory memory storing a relationship between (1) a sliding resistance index μk as a characteristic value indicating a sliding performance of a valve stem of the regulating valve, the sliding performance changing depending on an ambient temperature, and (2) the ambient temperature;
- a control parameter non-transitory memory storing a correspondence between the characteristic value and a control parameter used to control a valve opening of the regulating valve;
- and
- a temperature sensor configured to measure a current ambient temperature of the regulating valve,
- wherein the controller is further configured to
- acquire as a current characteristic value, a characteristic value corresponding to the measured current ambient temperature based on the relationship stored in the characteristic value/ambient temperature relationship non-transitory memory,
- select, from the control parameter non-transitory memory, a control parameter corresponding to the current characteristic value,
- acquire the current characteristic value and select the control parameter corresponding to the current characteristic value repeatedly at regular intervals, and
- control the valve opening of the regulating valve using the selected control parameter.
A method, comprising:
- outputting, as a control output, an electric signal according to a difference between a valve opening setting value sent from a higher-level device and an actual opening value fed back from a regulating valve;
- converting the control output to an air pressure and outputting the air pressure to a setting/operating device of the regulating valve;
- storing, in a first memory, a relationship between (1) a sliding resistance index μk as a characteristic value indicating a sliding performance of a valve stem of the regulating valve, the sliding performance changing depending on an ambient temperature, and (2) the ambient temperature;
- storing in a second memory, a correspondence between the characteristic value and a control parameter used to control a valve opening of the regulating valve;
- measuring, using a temperature sensor, the current ambient temperature of the regulating valve;
- acquiring, as a current characteristic value, a characteristic value corresponding to the measured ambient temperature based on the relationship stored in the second memory,
- selecting, from the second memory, a control parameter corresponding to the current characteristic value;
- acquiring the current characteristic value and selecting the control parameter corresponding to the current characteristic value repeatedly at regular intervals;
- and
- controlling the valve opening of the regulating valve using the selected control parameter.
Dependencies are inferred from the claim text.