Omnidirectional Piezoelectric Accelerometer for Compact Medical Devices
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Solution Overview
Problem
Current accelerometer devices cannot effectively handle both low-frequency, low-amplitude human activity and high-frequency, high-amplitude physical impacts in a physically small, cost-effective, and power-efficient package, especially in medical devices that require omnidirectional sensitivity.
Innovation Solution
A monolithic omnidirectional accelerometer device with a piezoelectric sensor element and mass-supporting arms, featuring a proof mass and connecting rod, which generates distinct sensor signals at electrically distinct sensor electrodes, allowing for equal sensitivity in all directions and efficient power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional accelerometer devices are used, then they can detect either low-frequency human activity or high-frequency impacts, but they cannot effectively handle both excitation modes simultaneously in a compact package
Solution Approach 1:
The patent combines multiple sensor elements (capacitive sensors and piezoelectric sensors) into a single integrated accelerometer device. The capacitive sensors detect low-frequency human activity while piezoelectric sensors detect high-frequency impacts, allowing both detection capabilities to coexist in one compact unit rather than requiring separate devices.
Solution Approach 2:
The accelerometer device is designed with universal sensing capabilities to detect both low-frequency excitation (human activity) and high-frequency excitation (physical impacts) using the same physical structure. The sensor array can respond to a wide frequency range, making the device versatile for multiple detection purposes without requiring separate specialized sensors.
2Adaptability or versatility
If direction-insensitive omnidirectional detection is implemented, then the device can detect acceleration in any direction, but this increases device complexity and size
Solution Approach 1:
The patent uses an asymmetric arrangement of sensor elements around the proof mass, with capacitive sensors positioned on opposite sides and piezoelectric sensors positioned at angles. This asymmetric configuration enables omnidirectional detection capability while maintaining a compact form factor, as the different sensor types complement each other to provide full directional coverage without requiring a complex multi-axis sensor array.
3Measurement precision
If multiple sensor elements are integrated to detect both excitation modes, then detection capability is improved, but power consumption increases
Solution Approach 1:
The piezoelectric sensor elements generate electrical charge directly from mechanical stress without requiring external power for the sensing mechanism itself. When the proof mass accelerates, the piezoelectric materials automatically produce voltage signals proportional to the applied force, eliminating the need for powered transducers and reducing overall system power consumption while maintaining high-frequency detection capability.
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 device enables reliable detection of human activity and impacts in medical devices, ensuring accurate operation and user safety while maintaining a compact, cost-effective, and power-efficient design.
Implementation Method 1
acceleration of the proof mass causes deflection of the piezoelectric material, which generates respective sensor signals at one or more of the sensor electrodes
Data Source
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AI summary
A portable medical device is provided with an internal accelerometer device. The medical device includes a circuit board, the accelerometer device, and a response module coupled to the accelerometer device. The accelerometer device is mechanically and electrically coupled to the circuit board, and it includes a plurality of mass-supporting arms for a plurality of electrically distinct sensor electrodes, piezoelectric material for the mass-supporting arm, and a proof mass supported by the mass-supporting arms. Each of the mass-supporting arms has one of the sensor electrodes located thereon. Acceleration of the proof mass causes deflection of the piezoelectric material, which generates respective sensor signals at one or more of the sensor electrodes. The response module is configured to initiate an acceleration-dependent operation of the portable medical device in response to generated sensor signals present at the sensor electrodes.