Method for detecting nonlinear oscillation during industrial process based on improved variational mode decomposition

Abstract

The invention discloses a method for detecting a nonlinear oscillation during an industrial process based on improved variational mode decomposition. The method comprises the following steps: (1) collecting a set of loop output signals of a to-be-detected industrial process; (2) calculating a frequency spectrum and a phase correction signal mean frequency spectrum of the loop output signals to determine the mode number and the center frequency initial value; (3) setting the search range and the step size of a penalty coefficient; (4) calculating the sum permutation entropy obtained through a VMD decomposition corresponding to different penalty coefficients, and determining an optimal penalty coefficient; (5) performing the VMD decomposition adopting the determined mode number, the center frequency initial value and the penalty coefficient to select an effective mode; and (6) calculating whether a multiple relation exists between center frequencies of the effective mode, and judging whether a nonlinear oscillation exists or not. According to the method for detecting the nonlinear oscillation during the industrial process based on improved variational mode decomposition, the accuracyand the reliability of a nonlinear detection for the control loop of the industrial process can be improved, a data support is provided for performance evaluations and fault diagnoses, and a foundation is laid for a subsequent positioning work of multi-loop nonlinear oscillation sources.

Description

technical field [0001] The invention belongs to the field of performance evaluation and fault diagnosis in industrial control systems, in particular to an industrial process nonlinear oscillation detection method based on improved variational mode decomposition. Background technique [0002] With the rapid development of fault diagnosis and performance evaluation technology of industrial control loops, oscillation detection has become one of the main tasks of fault diagnosis of control loops. Oscillations generated in one loop usually propagate to other loops due to the connections and couplings between control system loops. These oscillations cause problems such as energy loss, wasted raw material and reduced product quality. Valve stickiness, controller imbalance, and external disturbances are the three main causes of oscillations. [0003] It has been pointed out in the literature that the nonlinear links in the control system, such as valve viscosity, may be the main r...

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Problems solved by technology

However, the decomposition effect of the basic variational mode is heavily dependent on the number of modes, the initial value of the center frequency and the penalty coefficient. The current research mostly uses iterative or swarm intelligence optimization methods to select parameters

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