Dynamic Sampling Frequency Current Measurement System
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Solution Overview
Problem
Current measurement methods face challenges in accurately measuring current values with a wide range of frequencies, particularly when devices switch ON and OFF, leading to issues like aliasing and time-lag due to fixed cutoff frequencies in low pass filters, which restrict versatility and accuracy.
Innovation Solution
A current measurement system that employs multiple signal processing parts with different sampling frequencies to output the maximum and minimum current values, comparing these differences to derive a more accurate current measurement value, allowing for flexible frequency adjustments and reduced signal communication traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed cutoff frequency low pass filter is used to eliminate fluctuation due to aliasing, then measurement accuracy is improved, but adaptability is worsened because the cutoff frequency cannot be changed freely after determination
Solution Approach 1:
The patent implements dynamic adjustment of the low pass filter's cutoff frequency through software control. The microcontroller can change the cutoff frequency based on the operating conditions and sampling frequency, transforming the static filter into a dynamic one that adapts to different measurement requirements without hardware changes.
Solution Approach 2:
The patent changes the parameter of cutoff frequency dynamically. By adjusting the cutoff frequency parameter in response to different sampling frequencies and operating conditions, the system maintains measurement accuracy while improving adaptability. This allows the same hardware to handle various frequency ranges effectively.
2Stability of the object's composition
If smoothing processing is performed to reduce fluctuation in current measurement, then measurement stability is improved, but time-lag increases causing control response delay
Solution Approach 1:
Instead of applying strong smoothing that过度 reduces fluctuation, the patent uses a balanced approach with adjustable low pass filtering. The filter strength can be tuned to provide just enough smoothing to eliminate aliasing while maintaining sufficient responsiveness for control purposes, avoiding excessive time-lag.
Solution Approach 2:
The patent dynamically adjusts the low pass filter's cutoff frequency parameter to optimize the balance between smoothing and responsiveness. By changing this parameter based on operating conditions, the system achieves measurement stability without excessive time-lag, allowing adaptive control response.
3Device complexity
If discrete sampling is performed at fixed sampling frequency to measure current value, then device complexity is reduced, but measurement precision is worsened when sampling frequency coincides with operating frequency causing aliasing
Solution Approach 1:
The patent implements dynamic adjustment of the sampling frequency based on the operating conditions. The microcontroller can change the sampling frequency to avoid coincidence with the operating frequency of the load, thereby preventing aliasing while maintaining relatively simple discrete sampling architecture.
Solution Approach 2:
The patent changes the sampling frequency parameter dynamically to avoid aliasing. By adjusting this parameter in response to detected operating conditions, the system maintains measurement precision without requiring complex sampling architectures, achieving a balance between simplicity and accuracy.
4Measurement precision
If multiple signal processing parts with different sampling frequencies are used to measure current value, then measurement precision is improved for wide frequency range, but device complexity increases
Solution Approach 1:
The patent makes a single signal processing part perform multiple functions by enabling it to operate at different sampling frequencies. This universal approach allows one part to handle various frequency ranges, achieving the benefits of multiple specialized parts while avoiding the complexity of having separate dedicated measurement circuits for each frequency range.
Data Source
AI summary
A current measurement method includes a difference outputting step of performing sampling at a different sampling frequency for each of a plurality of signal processing parts and outputting a difference between a maximum value and a minimum value output from a signal processing part, a comparing step of outputting specified information showing the signal processing part by which a difference with a largest absolute value is output among differences output in the difference outputting step, and a deriving step of deriving a measured value of a current value between a battery and a power control unit on the basis of the current value sampled by the signal processing part shown by the specified information output in the comparing step.