Frequency Control in Closed Loop Systems
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Solution Overview
Problem
Closed loop control systems face issues with periodic disturbances in feedback signals, leading to improper corrections and unaddressed periodic deviations in process variables, as these disturbances can be misinterpreted by the control system.
Innovation Solution
A process controller that calculates the magnitude and phase of frequency components in the feedback signal and generates compensating waveforms to cancel out these disturbances, ensuring accurate control signals are applied to the system under control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard closed loop control is used to maintain process variable at set point, then the control system responds to deviations, but periodic disturbances in feedback signal cause improper corrections
Solution Approach 1:
The patent extracts and removes periodic disturbances from the feedback signal through spectral analysis and notch filtering. The control system identifies frequency components in the feedback signal and selectively attenuates periodic disturbance frequencies before the feedback reaches the controller, preventing improper corrections while preserving valid process variable information.
Solution Approach 2:
The patent introduces an intermediary signal processing stage between the feedback sensor and the controller. This intermediary layer performs spectral analysis and applies frequency-selective filtering to separate periodic disturbances from legitimate process variations, allowing the controller to receive cleaned feedback information without direct exposure to corrupting periodic signals.
2Stability of the object's composition
If closed loop control generates correction based on feedback deviations, then process variable is maintained, but periodic disturbances cause unnecessary corrections that deviate from desired set point
Solution Approach 1:
The patent applies preliminary anti-action by preemptively removing periodic disturbances from the feedback signal before they can trigger unnecessary corrections. The system performs spectral analysis and applies notch filters at identified disturbance frequencies, preventing the controller from generating harmful corrective actions in response to spurious feedback deviations.
Solution Approach 2:
The patent converts the harmful periodic disturbances into beneficial information by performing spectral analysis on the feedback signal. The identified frequency components and their characteristics are used to design targeted notch filters, transforming the problematic periodic signals into the basis for their own elimination and improving overall control accuracy.
3Loss of information
If feedback signal contains periodic disturbances from system characteristics or sensors, then measurement is obtained, but these disturbances appear as false deviations requiring improper control actions
Solution Approach 1:
The patent performs preliminary spectral analysis and identifies periodic disturbance frequencies before control decisions are made. By pre-characterizing the disturbance spectrum and configuring notch filters in advance, the system prepares the feedback signal processing pathway to automatically reject known disturbance frequencies while preserving legitimate process information.
Solution Approach 2:
The patent implements dynamic frequency analysis and adaptive filtering where the system continuously monitors the feedback signal spectrum and adjusts notch filter parameters accordingly. This dynamic approach allows the control system to adapt to changing disturbance characteristics while maintaining rejection of periodic disturbances, balancing information preservation with disturbance elimination.
Data Source
AI summary
Process controllers, methods, and systems provide for frequency control to account for the effects of periodic disturbances in the feedback signal of closed loop control systems. The frequency components of the feedback signal are determined, including the magnitude and phase of each. Waveforms for each frequency component are generated with substantially the same magnitude and substantially the opposite phase of each frequency component. The waveforms are then summed to produce a compensating waveform that is summed within the output of the control system so that the effects of the periodic disturbances are cancelled from the control system output being provided to the system under control.