Disturbed Variable Measurement Using Period-Synchronous Averaging
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Solution Overview
Problem
Existing methods for measuring disturbed variables, such as currents or voltages, are prone to delays and instabilities due to periodic disturbances caused by control signals, leading to undesirable signal peaks and reduced sensitivity.
Innovation Solution
The approach involves digitizing the disturbed signal with a multibit sampling frequency and averaging over a period duration or its integer multiple, allowing for reduced delay by starting averaging with a time offset, thereby minimizing the impact of periodic disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement methods are used to measure disturbed variables, then the measurement can be performed, but the measurement is subject to periodic disturbances and peaks causing delays and instabilities
Solution Approach 1:
The patent applies periodic action by using a moving average filter that processes samples at a frequency synchronized with the periodic disturbance. The filter calculates averages over periods matching the disturbance frequency, effectively filtering out periodic components while maintaining accurate measurement of the underlying variable. This resolves the contradiction by making the measurement process periodic and synchronized with the disturbance, thereby achieving both accuracy and stability.
2Measurement precision
If averaging is performed over the disturbance period to reduce periodic disturbances, then the measurement accuracy improves, but the delay in measurement output increases
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing multiple averaged values at different time offsets before they are needed for control decisions. The filter maintains a buffer of pre-computed averages, allowing the system to retrieve the most relevant average without performing the full averaging calculation at the moment of need. This reduces measurement delay while maintaining accuracy.
Solution Approach 2:
The patent applies dynamics by making the averaging window adaptive rather than fixed. The filter dynamically adjusts its operation based on the specific disturbance characteristics and timing requirements of the application. By allowing the averaging process to be flexible in its timing and duration, the system can optimize between accuracy and delay depending on real-time conditions.
3Speed
If the measurement frequency is increased to reduce delay, then the responsiveness improves, but the sensitivity to periodic disturbances increases
Solution Approach 1:
The patent implements feedback by using the output of the moving average filter to inform subsequent measurement and control decisions. The filtered measurement values are fed back into the control system, creating a closed-loop measurement process that continuously refines the measurement quality. This feedback mechanism allows the system to maintain high response speed while systematically reducing sensitivity to periodic disturbances through iterative filtering.
Data Source
AI summary
Provided are apparatuses and methods, in which a disturbed measurement variable is converted to a digital signal. The digital signal is then averaged over a number of sampling values which corresponds to a period of the disturbances.