ASIC Difference Filter for Force Press Signal Detection
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Solution Overview
Problem
Existing sensor technologies face difficulties in accurately detecting force presses due to unwanted direct current and slow-changing signals, making it challenging to quantify force applied and calculate multistage force presses effectively.
Innovation Solution
An integrated circuit with a difference filter configured to subtract the output of an earlier boxcar filter from a later boxcar filter, using a coefficient set of [1 1 1 1 −1 −1 −1 −1] to remove direct current stress signals and reduce slow-changing signals, producing filtered values that are more effective than low-pass IIR filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If direct current stress signals and slow-changing signals are present in sensor output, then the sensor can detect a wider range of signal types, but the measurement precision of force presses deteriorates
Solution Approach 1:
The patent extracts and removes the unwanted direct current stress signals and slow-changing signals from the sensor output through a difference filter. The filter subtracts earlier boxcar filter outputs from later boxcar filter outputs, effectively isolating and eliminating the problematic signal components while preserving the force press information.
Solution Approach 2:
The difference filter acts as an intermediary processing stage between the sensor and the final measurement system. It mediates by transforming the raw sensor signal into a filtered signal that removes unwanted components, allowing the system to maintain both wide signal detection capability and high force press measurement precision.
2Measurement precision
If complex filtering algorithms are used to remove unwanted signals, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent employs a simple difference filter with coefficients of just 1 and -1, which is computationally inexpensive and easy to implement in hardware or software. This simple filtering approach provides effective removal of direct current and slow-changing signals without requiring complex algorithms or substantial processing resources.
Solution Approach 2:
The filter uses a specific parameter configuration (difference filter with coefficients [1 1 1 1 -1 -1 -1 -1]) that transforms the filtering operation into a simple subtraction process. This parameter choice changes the complexity of implementation while maintaining effective signal separation capabilities.
3Ease of operation
If prefixed thresholds are used to quantitate force applied, then the operation simplicity improves, but the reliability deteriorates due to moving pre-press target
Solution Approach 1:
The difference filter performs preliminary processing by removing direct current stress signals and slow-changing signals before the force press measurement is taken. This preliminary action stabilizes the baseline (pre-press) by eliminating the moving target effect, making subsequent threshold-based quantitation reliable and accurate.
Solution Approach 2:
The filter creates a stabilized reference level by subtracting earlier signal states from later states, providing a feedback mechanism that continuously adjusts for drift and stress changes. This feedback approach maintains a stable pre-press baseline that enables reliable threshold comparison.
Data Source
AI summary
Disclosed is an integrated circuit having a sensor configured to sense a stimulus and in response to output an analog signal, and an analog-to-digital converter configured to receive the analog signal and to output a stream of digital values that are in proportion to the analog signal. A difference filter is configured to receive the digital values and to subtract an N number of the digital values from an M number of the digital values to generate filtered values, wherein M and N are counting numbers.