초록 ▼

Methods and systems for performing online valve diagnostics. Valve characteristics such as step response, friction and spring range are determined while the valve is operating in a process without intervention by a controller deriving the valve diagnostics. Valve information is obtained while the v

Methods and systems for performing online valve diagnostics. Valve characteristics such as step response, friction and spring range are determined while the valve is operating in a process without intervention by a controller deriving the valve diagnostics. Valve information is obtained while the valve operates in response to a control signal controlling a process while the valve operates through a series of gradual movements. Valve characteristics are then determined from the valve information.

대표청구항 ▼

What is claimed is: 1. A method of performing online valve diagnostics for a valve operating in a plant process, the method comprising: obtaining valve information while said valve operates in response to a plurality of setpoints determined for controlling said plant process, said valve operating t

What is claimed is: 1. A method of performing online valve diagnostics for a valve operating in a plant process, the method comprising: obtaining valve information while said valve operates in response to a plurality of setpoints determined for controlling said plant process, said valve operating through a series of gradual movements; said valve information including at least two of setpoint data, position data and pressure data; deriving at least one of step response, friction and spring range for said valve based on said valve information. 2. The method of claim 1 further comprising: deriving a model of valve response to setpoint changes in response to said valve information; adjusting said model in response to error between predictions generated by said model and actual position information; and applying a step input to said model to generate a step response. 3. The method of claim 2 wherein: adjusting said model includes adjusting a first parameter affecting response time. 4. The method of claim 3 wherein: adjusting said model includes adjusting a second parameter affecting overshoot. 5. The method of claim 2 wherein: said deriving said model includes taking a derivative of a setpoint data and taking a derivative of position data; solving for a set of coefficients that minimizes the error estimating said derivative of position data from said derivative of input data to define a wavelet; said applying said step input to said model includes integrating said wavelet; and deriving response time and overshoot from said step response. 6. The method of claim 2 wherein: said deriving said model includes obtaining plurality of wavelets in response to setpoint changes; said adjusting includes selecting one of said wavelets with minimal error; deriving a step response by applying said wavelet to an impulse; and deriving response time and overshoot from said step response. 7. The method of claim 1 further comprising: deriving a distribution of said position data by transforming said pressure data and said position data in response to a spring range of said valve; determining friction of said valve in response to said distribution. 8. The method of claim 7 wherein: said determining friction includes determining a difference between an upper percentile and a lower percentile of said distribution. 9. The method of claim 8 wherein: said upper percentile is 90 percent and said lower percentile is 10 percent. 10. The method of claim 7 wherein: said deriving said distribution includes projecting position data to a pressure axis along a slope corresponding to said spring range. 11. The method of claim 1 further comprising: deriving a plurality of distributions of said position data in response to a plurality of spring ranges of said valve; selecting one of said spring ranges in response to variance of said plurality of distributions. 12. A system for deriving valve characteristics of a valve operating in a plant process, the system comprising: a process controller generating a plurality of setpoints determined for controlling said plant process, said plurality of setpoints operating said valve through a series of gradual movements; a positioner receiving said plurality of setpoints and generating a signal for positioning said valve; a controller receiving valve information from said positioner while it is operating based on the setpoints, said valve information including at least two of setpoint data, position data and pressure data; said controller deriving at least one of step response, friction and spring range for said valve based on said valve information. 13. A storage medium encoded with machine-readable computer program code for deriving valve characteristics of a valve operating in a plant process, the storage medium including instructions for causing a controller to implement a method comprising: obtaining valve information while said valve operates in response to a plurality of setpoints determined for controlling said plant process, said valve operating through a series of gradual movements; said valve information including at least two of setpoint data, position data and pressure data; deriving at least one of step response, friction and spring range for said valve based on said valve information.