Abstract: An asymmetric volume booster assembly includes an actuator movable in a first direction and a second direction, a first booster in fluid communication with the actuator, and a second booster in fluid communication with the actuator. The first booster includes a first supply passage and a first exhaust passage, wherein the first supply passage supplies fluid to the actuator and the first exhaust passage exhausts fluid from the actuator. The first exhaust passage is configured to produce a first fluid flow resistance. The second booster includes a second supply passage and a second exhaust passage, wherein the second supply passage supplies fluid to the actuator and the second exhaust passage exhausts fluid from the actuator. The second exhaust passage is configured to produce a second resistance to fluid flow. The first fluid flow resistance is greater than the second fluid flow resistance, such that the actuator moves substantially symmetrically in the first direction and the second direction.

Abstract: An asymmetric volume booster assembly includes an actuator movable in a first direction and a second direction, a first booster in fluid communication with the actuator, and a second booster in fluid communication with the actuator. The first booster includes a first supply passage and a first exhaust passage, wherein the first supply passage supplies fluid to the actuator and the first exhaust passage exhausts fluid from the actuator. The first exhaust passage is configured to produce a first fluid flow resistance. The second booster includes a second supply passage and a second exhaust passage, wherein the second supply passage supplies fluid to the actuator and the second exhaust passage exhausts fluid from the actuator. The second exhaust passage is configured to produce a second resistance to fluid flow. The first fluid flow resistance is greater than the second fluid flow resistance, such that the actuator moves substantially symmetrically in the first direction and the second direction.

Abstract: Systems and methods for urging a valve plug off a seat of a control valve and toward a set point in the absence of significant delay. Adjustable, user-selected input parameters to the input of a lead-lag filter in communication with the input of a control loop facilitates achieving tunable response by a control valve upon application of small amplitude inputs.

Abstract: A method and apparatus determines the presence of and source of instabilities, such as limit cycles, within a process control loop while the process control loop operates on-line within a process environment. The method and apparatus measures one or more signals within a process control loop when the process control loop is connected on-line within a process control environment, stores the measured signal as signal data and then performs one or more statistical analyses on the stored signal data to determine whether instabilities exist and, if so, whether the source of an instability is within a servo loop or outside of a servo loop and is due to friction, external forces or mechanical anomalies.

Abstract: A control loop of a control valve is operated using outlet pressure from a pneumatic amplifier as the control parameter. The control loop may be operated continuously in pressure control mode, or may be switched from another mode, such as travel control mode, to pressure control mode in response to certain operating conditions such as operation in the cutoff range, operation with the throttling element engaging a travel stop, or as a backup in the event of primary control parameter sensor failure. Operating the control loop in pressure control mode further allows diagnostics to be performed on the control loop components, even when the system is operating in cutoff range or has engaged a travel stop. The diagnostics may be performed using pressure and displacement sensors normally provided with a positioner. A processor may be programmed to receive data from the sensors and generate fault signals according to a logic sub-routine.

Abstract: Method and apparatus for performing diagnostics in a pneumatic control loop for a control valve. Pressure and displacement sensors normally provided with a positioner are used to detect operating parameters of the control loop. A processor is programmed to receive feedback from the sensors and generate fault signals according to a logic sub-routine. The logic sub-routine may include calculating mass flow of control fluid through spool valve outlet ports and comparing other operating parameters of the control fluid to detect leaks and blockages in the control loop. Once a fault is detected, the location of the root cause of the fault may be identified by characterizing operating parameters of the control loop at the time of the fault.

Abstract: A control loop of a control valve is operated using outlet pressure from a pneumatic amplifier as the control parameter. The control loop may be operated continuously in pressure control mode, or may be switched from another mode, such as travel control mode, to pressure control mode in response to certain operating conditions such as operation in the cutoff range, operation with the throttling element engaging a travel stop, or as a backup in the event of primary control parameter sensor failure. Operating the control loop in pressure control mode further allows diagnostics to be performed on the control loop components, even when the system is operating in cutoff range or has engaged a travel stop. The diagnostics may be performed using pressure and displacement sensors normally provided with a positioner. A processor may be programmed to receive data from the sensors and generate fault signals according to a logic sub-routine.

Abstract: A method and apparatus determines the presence of and source of instabilities, such as limit cycles, within a process control loop while the process control loop operates on-line within a process environment. The method and apparatus measures one or more signals within a process control loop when the process control loop is connected on-line within a process control environment, stores the measured signal as signal data and then performs one or more statistical analyses on the stored signal data to determine whether instabilities exist and, if so, whether the source of an instability is within a servo loop or outside of a servo loop and is due to friction, external forces or mechanical anomalies.

Abstract: Method and apparatus for performing diagnostics in a pneumatic control loop for a control valve. Pressure and displacement sensors normally provided with a positioner are used to detect operating parameters of the control loop. A processor is programmed to receive feedback from the sensors and generate fault signals according to a logic sub-routine. The logic sub-routine may include calculating mass flow of control fluid through spool valve outlet ports and comparing other operating parameters of the control fluid to detect leaks and blockages in the control loop. Once a fault is detected, the location of the root cause of the fault may be identified by characterizing operating parameters of the control loop at the time of the fault.

Abstract: Method and apparatus for performing diagnostics in a pneumatic control loop for a control valve. Pressure and displacement sensors normally provided with a positioner are used to detect operating parameters of the control loop. A processor is programmed to receive feedback from the sensors and generate fault signals according to a logic sub-routine. The logic sub-routine may include calculating mass flow of control fluid through spool valve outlet ports and comparing other operating parameters of the control fluid to detect leaks and blockages in the control loop. Once a fault is detected, the location of the root cause of the fault may be identified by characterizing operating parameters of the control loop at the time of the fault.

Abstract: Method and apparatus for performing diagnostics in a pneumatic control loop for a control valve. Pressure and displacement sensors normally provided with a positioner are used to detect operating parameters of the control loop. A processor is programmed to receive feedback from the sensors and generate fault signals according to a logic sub-routine. The logic sub-routine may include calculating mass flow of control fluid through spool valve outlet ports and comparing other operating parameters of the control fluid to detect leaks and blockages in the control loop. Once a fault is detected, the location of the root cause of the fault may be identified by characterizing operating parameters of the control loop at the time of the fault.

Abstract: A method and apparatus statistically determines estimates of one or more process control loop parameters, such as bearing friction, seal friction, total friction, dead band, dead time, oscillation, shaft windup or backlash associated with a device or a control loop within a process control environment. The method and apparatus measures one or more signals within a process control loop when the process control loop is connected on-line within a process control environment, stores the measured signal as signal data and then performs one of a number of statistical analyses on the stored signal data to determine the desired parameter estimate.

Abstract: A method and apparatus determines the presence of and source of instabilities, such as limit cycles, within a process control loop while the process control loop operates on-line within a process environment. The method and apparatus measures one or more signals within a process control loop when the process control loop is connected on-line within a process control environment, stores the measured signal as signal data and then performs one or more statistical analyses on the stored signal data to determine whether instabilities exist and, if so, whether the source of an instability is within a servo loop or outside of a servo loop and is due to friction, external forces or mechanical anomalies.

Abstract: A diagnostic test unit for deterministically measuring one or more parameters, such as dead band, dead time, response time, gain, or overshoot, of a process control device that is connected in a process control loop during operation of a process includes a switch controller, a signal generator, a switch, a response accumulator mechanism, and an analyzer mechanism. The switch controller monitors a process signal during operation of the process to determine whether the process signal is substantially stable. In the event that the process signal is substantially stable, the switch replaces a control signal with a diagnostic test signal generated by the signal generator. The response accumulator is in communication with the process control loop to obtain an indication of the response of the process control device to the diagnostic test signal. The analyzer unit then determines the device parameter from the test signal and the response indication.

Abstract: A device and method that automatically tune a valve controller coupled to a process control loop generate a plurality of sets of tuning parameters for use by the controller, deliver a test signal, such as a blocked sinusoidal signal, to the controller to force the process control loop through a test cycle while each of the plurality of sets of tuning parameters are being used by the controller and measure a response of the process control loop during each of the test cycles. The device and method then calculate a performance index for each of the plurality of sets of tuning parameters based on the measured responses and select one of the sets of tuning parameters based on the calculated performance indices. The selected set of tuning parameters is then loaded into the controller for use during normal operation of the process control loop.

Abstract: An apparatus for nonobtrusively determining one or more parameters, such as dead band, dead time, or response time of a process control device that is connected on-line in a process control loop includes a measurement unit and a processing unit. The measurement unit is coupled to the process control loop to detect stochastic changes in a control signal sent to the process control device and to detect an indication of the response of the process control device to the changes in the control signal while the process control device is operating on-line. The processing unit calculates the device parameters from one or more sets of the detected changes in the control signal and the detected response indication.