Piezoelectric Pressing Sensor Vibration Reset
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Solution Overview
Problem
Conventional piezoelectric sensors for detecting pressing force suffer from cumulative errors due to temperature drift, AD conversion errors, and plastic deformation, and struggle to accurately detect stable or slowly changing pressing forces, leading to complex sensor structures and increased processing loads.
Innovation Solution
A pressing sensor with a piezoelectric sensor, a current-voltage conversion circuit, a deformation amount detector, a minute vibration sensor, and an integration reset processor that resets the integrated value upon absence of minute vibration, allowing for accurate detection of pressing states with stable or slowly changing forces without complicating the sensor structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If integration processing is used to detect pressing force from piezoelectric sensor signal, then pressing force can be detected, but cumulative error occurs due to temperature drift, AD conversion error, and plastic deformation
Solution Approach 1:
The system performs preliminary detection of minute vibrations during the pressing operation. By detecting vibrations in advance, the system can determine when pressing has ended and reset the integrated value before cumulative error significantly affects measurement accuracy, thus maintaining reliable detection over time.
Solution Approach 2:
The system uses feedback from the minute vibration detection to control the reset timing of the integrated value. When vibrations are detected, the system continues integration; when vibrations cease, the system resets. This feedback mechanism ensures the integrated value is reset at the appropriate moment, preventing cumulative error while maintaining detection accuracy.
2Reliability
If contact detection sensor is added to reset integrated value, then cumulative error can be avoided, but sensor structure becomes complicated
Solution Approach 1:
The piezoelectric sensor serves multiple functions: it detects both the pressing force (through integration of its signal) and the presence of minute vibrations. This multi-functionality eliminates the need for a separate contact detection sensor, avoiding increased device complexity while still enabling cumulative error avoidance through vibration-based reset control.
Solution Approach 2:
The piezoelectric sensor detects its own operational state by monitoring minute vibrations generated during pressing. This self-service capability allows the sensor system to determine when resetting is needed without external sensors, simplifying the overall structure while maintaining reliability.
3Adaptability or versatility
If separate signal processing is performed for pressing force detection and contact detection, then both functions can be achieved, but arithmetic processing load increases
Solution Approach 1:
The system merges the detection functions by using the piezoelectric sensor's signal for both pressing force detection (through integration) and contact detection (through vibration analysis). This combination reduces the need for separate signal processing chains, lowering the arithmetic processing load while maintaining comprehensive detection capabilities.
Solution Approach 2:
The single piezoelectric sensor performs multiple detection tasks simultaneously. By processing its output signal for both integration-based force measurement and vibration-based contact detection, the system achieves versatile functionality without the increased processing burden of multiple independent sensors and processing paths.
4Device complexity
If threshold-based detection is used for piezoelectric signal, then simple detection is achieved, but pressing states with constant or slowly changing force cannot be detected
Solution Approach 1:
The system performs preliminary integration of the piezoelectric sensor signal to obtain the pressing force value before applying threshold-based detection. This preliminary integration transforms the differential signal into a cumulative measure that reflects both dynamic and static pressing states, enabling threshold detection to work effectively for stable or slowly changing forces while maintaining simplicity.
Solution Approach 2:
The integrated value acts as an intermediary between the piezoelectric sensor's differential output and the threshold-based detection system. This intermediary transformation allows the simple threshold method to detect pressing states that would otherwise be invisible to it, including constant and slowly changing forces, without complicating the overall detection architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively avoids cumulative errors and detects pressing states with stable or slowly changing forces, reducing processing load and maintaining sensor simplicity, enabling accurate detection of human operation even with weak or slowly changing pressing forces.
Implementation Method 1
a piezoelectric sensor that generates a detection voltage corresponding to a deformation amount of the pressing portion
Data Source
AI summary
A pressing sensor that includes a pressing portion deformed by pressing, a piezoelectric sensor that generates a detection voltage based on the deformation amount, and a first current-voltage conversion circuit that converts a charge/discharge current for a capacitance of the piezoelectric sensor into a voltage signal and outputs the voltage signal. Moreover, a deformation amount detector obtains an integrated value of an output voltage and detects the integrated value as the deformation amount of the pressing portion. A minute vibration sensor detects presence or absence of minute vibration of the pressing portion according to presence or absence of a minute fluctuation state of the output voltage and an integration reset processor resets the integrated value in response to absence of the minute vibration.