Valve positioner system

A method for detecting limit cycling in a valve, the method comprising the steps of:

• measuring a lag associated with the valve;
• measuring a period for the valve;
• determining a ratio of lag vs. period;
• comparing the ratio to a predetermined value;
• and
• if the ratio is greater than the predetermined value, reporting limit cycling.

A positioner capable of detecting limit cycling in a valve, the positioner comprising:

• means for measuring a plurality of actuator pressures for the valve;
• means for measuring a plurality of positions of the valve;
• means for determining zero crossings for the position and pressure measurements;
• means for determining a phase relationship from the zero crossings;
• means for comparing the phase relationship to a predetermined value;
• and
• means for determining limit cycling in the valve only if the phase relationship exceeds predetermined value by a predetermined amount.

A system for detecting limit cycling in a valve, comprising:

• means for measuring a lag associated with the valve;
• means for measuring a period for the valve;
• means for determining a ratio of lag vs. period;
• means for comparing the ratio to a predetermined value;
• and
• means for reporting limit cycling if the ratio is greater than the predetermined value.

For an electronically controllable valve, method for bumpless transfer from a manual mode of operation to an automatic mode of operation, the method comprising:

• determining when the automatic mode has been selected;
• receiving a position signal from the automatic mode for a new position;
• receiving a valve position from the valve;
• comparing the new position to the valve position;
• if the new position is within a predefined limit of the valve position, allowing the valve to enter automatic mode;
• and
• if the new position is outside of the predefined limit from the valve position, performing the steps of:
• i) holding the valve in a current position;
• ii) informing a user of the discrepancy in positions;
• iii) instructing the user to manually adjust the valve closer to the new position.

A positioner for an electronically controllable valve capable of providing bumpless transfer from a manual mode of operation to an automatic mode of operation, the positioner comprising:

• means for determining when the automatic mode has been selected;
• a means for receiving a position signal from the automatic mode for a new position;
• means for receiving a valve position from the valve;
• means for comparing the new position to the valve position;
• means for allowing the valve to enter automatic mode if the new position is within a predefined limit of the valve position;
• and
• means for informing a user of the discrepancy in positions if the new position is outside of the predefined limit from the valve position.

A control method for use by a valve positioner, the method comprising:

• allowing the valve to move in a first direction;
• repeatedly calculating a BIAS value for the positioner;
• a repeatedly averaging the BIAS value over a period of time;
• comparing a current BIAS value to the average;
• if the current BIAS value differs significantly from the average BIAS value, stopping the repeated averaging;
• and
• if the positioner tries to move the valve in a second direction, replacing the current BIAS value with the average BIAS value.

A method for adjusting a BIAS for a spool valve in an automatically positionable valve, the method comprising:

• maintaining an average of the BIAS over a period of time;
• measuring a first value for BIAS;
• updating the BIAS for the spool valve with the first value;
• measuring a second value for BIAS after measuring the first value;
• and
• updating the BIAS for the spool valve with the second value;
• wherein, if the second value of BIAS is between the first value and the average, the BIAS is updated quickly towards the average and if the second value of BIAS is not between the first value and the average, the BIAS is updated slowly towards the average.

A valve positioner comprising:

• an output signaling device for sending output signals;
• a control device for controlling a valve responsive to the output signals;
• means for repeatedly averaging the output signals over a period of time as the valve moves in a first direction;
• means for comparing a new output signal from the output signaling device to the average;
• and
• means for replacing the new output signal with the average if the positioner tries to move the valve in a second direction;
• wherein the averaging means stops averaging if the new output signal differs significantly from the average.

A positioner for an automatically positionable valve comprising:

• a spool valve for controlling an actuator, the spool valve being responsive to a BIAS output;
• means for consecutively calculating first and second BIAS values;
• means for maintaining an average of at least the first and second BIAS values;
• means for consecutively calculating third and fourth BIAS values;
• means for determining the BIAS output from the BIAS values;
• and
• means for adjusting the BIAS output towards the average if the fourth BIAS value is between the third BIAS value and the average.

A method for measuring a valve signature for a valve having an actuator, the method comprising:

• opening a spool valve of the actuator to increase actuator pressure;
• measuring a plurality of pressure data for the actuator and position data for the valve as the valve is opening;
• closing the spool valve to decrease the actuator pressure;
• measuring a plurality of pressure data for the actuator and position data for the valve as the valve is closing;
• analyzing the measured data to determine friction and hysteresis for the valve;
• and
• determining the valve signature from the analyzed data.

A method for diagnosing a valve having position feedback capabilities and controlled through an actuator, the method comprising:

• positioning the valve at a first location;
• sampling a position of the valve at the first location;
• adjusting a fluid supply to the actuator to move the valve to a second location;
• sampling a position of the valve at the second location;
• and
• determining a first valve signature from the sampled positions.

A positioner for controlling a valve with an actuator and capable of determining a valve signature, the positioner comprising:

• a spool valve connected to the actuator;
• a pressure feedback for reporting actuator pressure;
• a position feedback for reporting valve position;
• means for opening the spool valve to increase the actuator pressure;
• means for measuring a plurality of actuator pressures and valve positions as the valve is opening;
• means for closing the spool valve to decrease the actuator pressure;
• means for measuring a plurality of actuator pressures and valve positions as the valve is closing;
• means for analyzing the measured data to determine a friction measurement and hysteresis value for the valve;
• and
• means for calculating the valve signature from the friction measurement and hysteresis value.

A system for diagnosing a valve having position feedback capabilities and controlled through an actuator, the system comprising:

• a spool valve for supplying a fluid to the actuator;
• means for positioning the valve at a first location using the position feedback capabilities;
• means for sampling a position of the valve at the first location and for sampling a position of the valve after the fluid supply has been adjusted in the first direction
• means for adjusting the fluid supply in a first direction;
• and
• means for determining a first valve signature from the sampled positions for diagnosing the valve.

A method for performing diagnostics on a valve having an actuator, the method comprising:

• positioning the valve at a first end of a test range of valve positions;
• incrementing fluid pressure to the actuator until it reaches a second end of the test range;
• decrementing fluid pressure to the actuator until it reaches the first end of the test range;
• sampling valve position and actuator pressure data during the incrementing and decrementing;
• storing the sampled position and pressure data in memory;
• and
• analyzing the stored data.

A system for performing diagnostics on a valve having an actuator, comprising:

• means for positioning the valve at a first end of a test range of valve positions;
• means for incrementing a fluid pressure to the actuator until it reaches a second end of the test range and decrementing the fluid pressure to the actuator until it reaches the first end of the test range;
• means for sampling valve position and actuator pressure data as the fluid pressure is incrementing and decrementing;
• memory for storing the sampled position and pressure data;
• and
• means for analyzing the stored data.

A method for providing valve response feedback to a user, the method comprising:

• defining a characterization function for the valve;
• receiving a position set point for the valve;
• receiving an actual valve position from the valve;
• displaying the actual valve position on a graph;
• and
• displaying a characterization of the position set point on the graph;
• wherein if the valve is operating correctly, the actual valve position and the characterization of the set point will align on the graph.

A method for providing valve response feedback to a user, the method comprising:

• defining a characterization function for the valve;
• determining an inverse function of the characterization function;
• receiving a position set point for the valve;
• receiving an actual valve position from the valve;
• determining a predicted set point from the actual valve position and the inverse function;
• displaying the predicted set point on a graph;
• and
• displaying the position set point on the graph;
• wherein if the valve is operating correctly, the predicted set point and the position set point will align on the graph.

A system for providing valve response feedback to a user, comprising:

• means for performing a characterization function for a valve;
• means for receiving a position set point for the valve;
• means for receiving an actual valve position from the valve;
• and
• a display for showing the actual valve position and a characterization of the position set point on a single graph;
• wherein if the valve is operating correctly, the actual valve position and the characterization of the set point will align on the graph.

A system for providing valve response feedback to a user, comprising:

• means for performing an inverse characterization function for a valve;
• means for receiving a position set point for the valve;
• means for receiving an actual valve position of the valve;
• means for determining a predicted set point from the actual valve position and the inverse characterization function;
• and
• a display for showing the predicted set point and the position set point on a single graph;
• wherein if the valve is operating correctly, the predicted set point and the position set point will align on the graph.

A method for providing automatic compensation for twist of a shaft of a rotary-type valve to a valve positioner, the method comprising:

• calibrating the valve positioner while the valve is in a no-force condition;
• determining a gradient for the angular displacement of the rotary valve verses positioner signal;
• measuring a difference in actuator pressure for a predetermined valve position when the valve is in the no-force condition and when the valve is in a force condition;
• and
• determining a correction function for the valve from the gradient and the difference in actuator pressures.

A positioner for a rotary-type valve, the positioner comprising:

• memory for storing a calibration value of the valve while the valve is in a no-force condition and a gradient for describing the angular displacement of the rotary valve verses positioner signal;
• means for receiving an actuator pressure from an actuator controlling the valve;
• means for receiving a position signal for indicating valve position;
• means for measuring a difference in the actuator pressure for a predetermined valve position when the valve is in the no-force condition and when the valve is in a force condition;
• and
• means for determining a correction function for the valve from the gradient and the difference in actuator pressures.

A method for providing nonlinear position control to a valve, the method comprising:

• calculating a first gain for the valve moving in a first direction;
• calculating a second gain for the valve moving in a second direction;
• calculating an adjustable gain to compensate for size-related and position-related valve nonlinearities;
• receiving a desired position signal for the valve;
• and
• adjusting the desired position by the adjustable gain and either the first or second gain to determine a calculated position signal for the valve.

A positioner for providing nonlinear position control to a valve, comprising:

• means for calculating a first gain for the valve moving in a first direction;
• means for calculating a second gain for the valve moving in a second direction;
• means for calculating an adjustable gain to compensate for size-related and position-related valve nonlinearities;
• means for receiving a desired position signal for the valve;
• and
• means for adjusting the desired position by the adjustable gain and either the first or second gain to determine a calculated position signal for the valve.

In a pneumatically controllable valve responsive to electronic positioning signals from a current-to-pressure (I/P) transducer, a self-adjusting method for positioning the valve comprising:

• finding a BIAS current to the I/P transducer;
• performing an open-loop test on the valve by using the found BIAS current for obtaining a system characteristic and a control parameter;
• and
• tuning the control parameter to achieve an improved dynamic response of the valve.

A self-adjusting positioner for controlling a pneumatically controllable valve responsive to electronic positioning signals from a current-to-pressure (I/P) transducer, the positioner comprising:

• means for determining a BIAS current to the I/P transducer;
• means for performing an open-loop test on the valve by using the found BIAS current for obtaining a system characteristic and a control parameter;
• and
• means for tuning the control parameter to achieve an improved dynamic response of the valve.

In a controllable valve responsive to positioning signals, a method for characterizing the valve to obtain uniformity of control performance comprising:

• providing a cross-reference table to the positioner;
• providing a first position signal to move the valve;
• measuring at least one process variable from the valve responsive to the first position signal;
• storing the process variable in the cross-reference table;
• receiving a position set point into a positioner for the valve;
• adjusting the position set point by the cross-reference table;
• and
• providing the adjusted position set point as a second positioning signal to the valve.

A system for providing a uniform control performance of a controllable valve responsive to positioning signals, comprising:

• a cross-reference table;
• means for receiving a first position signal to move the valve;
• means for measuring at least one process variable from the valve responsive to the first position signal;
• means for storing the process variable in the cross-reference table with the first position;
• means for receiving a position set point for the valve;
• means for adjusting the position set point by using the cross-reference table;
• and
• means for providing the adjusted position set point as a second positioning signal to the valve.

In a valve having a pneumatic actuator responsive to position control signals and a position feedback, a method to position the valve comprising:

• storing a plurality of pressures corresponding to a plurality of positions in a storage device;
• receiving a desired position;
• attempting to position the valve by adjusting the actuator until the position feedback matches the desired position;
• determining if the valve can be positioned by using the position feedback;
• and
• if the positioning feedback signal fails, choosing one of the stored positions and providing the corresponding actuator pressure for positioning the valve.

A positioner for a valve having a pneumatic actuator responsive to position control signals, comprising:

• a position feedback connected to the valve for positioning the valve;
• memory for storing a plurality of pressures corresponding to a plurality of positions from the position feedback;
• means for receiving a desired position;
• means for attempting to position the valve by adjusting the actuator until the position feedback matches the desired position;
• means for determining if the valve can be positioned by using the position feedback;
• and
• means for choosing one of the stored positions and providing the corresponding actuator pressure for positioning the valve if positioning with the positioning feedback fails.

A method for detecting seat leakage in an electronically positionable valve comprising:

• setting a minimum controllable valve lift point;
• determining if the valve is within the minimum controllable valve lift point;
• recording a time that the valve is within the minimum controllable valve lift point;
• comparing the recorded time to a predetermined limit;
• and
• performing a maintenance action in response to the recorded time exceeding the predetermined limit.

A method for detecting seat leakage in an electronically positionable valve comprising:

• determining an exact valve position when the valve is closed;
• closing the valve;
• receiving a position feedback indicating a position of the valve;
• comparing the position of the valve with the exact valve position;
• and
• performing a maintenance action in response to the position of the valve exceeding the exact valve position.

A system for detecting seat leakage in an electronically positionable valve comprising:

• means for setting a minimum controllable valve lift point;
• means for determining if the valve is within the minimum controllable valve lift point;
• means for recording a time that the valve is within the minimum controllable valve lift point;
• means for comparing the recorded time to a predetermined limit;
• and
• means for performing a maintenance action in response to the recorded time exceeding the predetermined limit.

A positioner capable of detecting seat leakage in an electronically positionable rotary valve comprising:

• means for determining an exact valve position when the valve is closed;
• means for closing the valve;
• a position feedback indicating a position of the valve;
• means for comparing the position of the valve with the exact valve position;
• and
• means for performing a maintenance action in response to the position of the valve exceeding the exact valve position.

A method for providing custom characterization of a valve while imposing constraints to prevent a detrimental valve characteristic, comprising:

• providing a graph including a plurality of points relating flow capacity to valve position, the points illustrating the valve characteristic;
• receiving a position change request of one of the points from a user;
• determining if there is a slope reversal of the valve characteristic responsive to the requested position change;
• and
• if there is a slope reversal, prompting a user for another position change.

A system for imposing constraints on a valve to prevent detrimental characterization comprising:

• a graph including a plurality of points relating flow capacity to valve position, the points illustrating the valve characteristic;
• means for receiving a position change request from a user;
• means for determining if there is an undesirable change in slope of the valve characteristic;
• and
• means for prompting a user for another position change if there is an undesirable change in the valve characteristic.