Diagnostic device for use in process control system

• US 20080033693A1
• Filed: 07/26/2007
• Published: 02/07/2008
• Est. Priority Date: 02/15/2005
• Status: Active Grant

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: Invernizzi, Giovanni, Moroni, Andrea, Andenna, Andrea
• Granted Patent: US 7,634,382 B2
• Time in Patent Office: Days
• US Class Current: 702/179
• CPC Class Codes: G05B 23/0221 Preprocessing measurements, e.g. data collection rate adjustment; Standardization of measurements; Time series or signal analysis, e.g. frequency analysis or wavelets; Trustworthiness of measurements; Indexes therefor; Measurements using easily measured parameters to estimate parameters difficult to measure; Virtual sensor creation; De-noising; Sensor fusion; Unconventional preprocessing inherently present in specific fault detection methods like PCA-based methods
• CPC Class Codes: G05B 23/024 Quantitative history assessment, e.g. mathematical relationships between available data; Functions therefor; Principal component analysis [PCA]; Partial least square [PLS]; Statistical classifiers, e.g. Bayesian networks, linear regression or correlation analysis; Neural networks

Abstract

The diagnostic device comprises a receiving means for receiving process variable values (x(t)) of a process variable of a process medium of a process, a measurement processing means for extracting and recording measurement statistics data from such process variable values, which are measured during a measuring phase, a training processing means for extracting and recording training statistics data from such process variable values, which are measured during a training phase, and a comparison means for comparing the measurement statistics data with training statistics data recorded before the measurement statistics data. Preferably, the training statistics data include a training empirical statistical distribution, which can be a distribution of a function of process variable values, which are measured during a training phase, or a distribution of a function of coefficients X_t(k), which are coefficients of a function of a transform of process variable values (x(t)), which are measured during a training phase.

Claims

1. A diagnostic device comprising

a receiving means for receiving process variable values of a process variable of a process medium of a process,

a measurement processing means for extracting and recording measurement statistics data from such process variable values, which are measured during a measuring phase,

a training processing means for extracting and recording training statistics data from such process variable values which are measured during a training phase, for calculating a training empirical statistical distribution whereby the distribution is a distribution of a function of process variable values which are measured during a training phase and for calculating a training analytical distribution function approximating the training empirical statistical distribution and comprising

a comparison means for comparing the measurement statistics data with training statistics data recorded before the measurement statistics data,

wherein the measurement statistics data comprise a measurement empirical statistical distribution, which is a distribution of a function of such process variable values, which are measured during a measuring phase, and that the training statistics data comprise the training analytical distribution function, and that the comparison means outputs a failure indication in case that the confidence level derived from a statistical test of the consistency of the measurement empirical statistical distribution with the training analytical distribution function is below a prescribable threshold value.

3. The diagnostic device according to claim 1, comprising a sensing means for measurement of the process variable and for generating the process variable values.

4. The diagnostic device according to claim 1, wherein the comparison means has a condition output related to a condition of the process, wherein the condition of the process is different from a measure for the process variable.

5. The diagnostic device according to claim 1, wherein the condition output is related to the condition of the sensing means.

6. The diagnostic device according to claim 1, wherein the measurement statistics data and the training statistics data relate to noise carried in the process medium.

7. The diagnostic device according to claim 6, wherein the transform is one of the group of Fourier transform and wavelet transform.

8. The diagnostic device according to claim 7, wherein the training analytical distribution function is a Gamma distribution function.

9. The diagnostic device according to claim 1, wherein the statistical test is one of the group of Chi²-test and Kolmogorov-Smirnov-test.

2. A diagnostic device comprising

a receiving means for receiving process variable values of a process variable of a process medium of a process,

a measurement processing means for extracting and recording measurement statistics data from such process variable values, which are measured during a measuring phase and for calculating a transform of process variable values, which are measured during a measuring phase, into coefficients X_m(k) of a set of orthogonal functions, and comprising

a training processing means for extracting and recording training statistics data from such process variable values which are measured during a training phase for calculating a training empirical statistical distribution, for calculating a transform of process variable values, which are measured during a measuring phase, into coefficients X_m(k) of a set of orthogonal functions, whereby the training empirical statistical distribution is a distribution of a function of the coefficients X_t(k) and for calculating a training analytical distribution function approximating the training empirical statistical distribution, and comprising

a comparison means for comparing the measurement statistics data with training statistics data recorded before the measurement statistics data

wherein the measurement statistics data comprise a measurement empirical statistical distribution, which is a distribution of the function of the coefficients X_m(k), and that the training statistics data comprise the training analytical distribution function, and that the comparison means outputs a failure indication in case that the confidence level of a statistical test of the consistency of the measurement empirical statistical distribution with the training analytical distribution function is below a prescribable threshold value.

10. A process control system comprising a diagnostic device according to