Piezoelectric Body Movement Sensor with Elastic Tensioning
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Solution Overview
Problem
Conventional body movement detection sensors face challenges such as safety issues with electric current, noise interference, and limited size reduction due to structural constraints, particularly with piezoelectric film-based sensors.
Innovation Solution
A body movement detection sensor design featuring a piezoelectric film, non-elastic belt members, and an elastic sheet that expands and contracts to generate voltage, allowing for a compact and thin form factor by housing the piezoelectric film within a case and using adjustable belt members to accommodate thoracic movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric film is used in a bridge shape for body movement detection, then detection sensitivity is improved, but the device size increases due to required deflection space
Solution Approach 1:
The piezoelectric film is configured in a planar layout within the cover member rather than requiring three-dimensional bridge deflection space. The elastic member applies tension along the length direction of the film, enabling detection functionality in a flattened, two-dimensional configuration that reduces overall device volume while maintaining sensitivity.
Solution Approach 2:
A thin piezoelectric film is used as the sensing element, housed within a flat cover member structure. This thin-film approach combined with the planar configuration enables compact integration while preserving the piezoelectric effect for accurate body movement detection.
2Volume of moving object
If winding roll members and locking roll members are added to house the piezoelectric film, then device compactness is improved, but structural complexity increases limiting further size reduction
Solution Approach 1:
The complex winding roll and locking roll mechanisms are completely removed from the design. Instead, the piezoelectric film is simply housed within a flat cover member, and the elastic member directly tensions the film along its length direction, achieving compactness without the mechanical complexity of rolling mechanisms.
Solution Approach 2:
The device is divided into functionally independent components: the cover member houses the piezoelectric film, the elastic member provides tensioning force, and the band member transmits body movement. This segmentation allows each component to be optimized independently, achieving compact integration without complex interlocking mechanisms.
3Measurement precision
If the elastic sheet length is increased to accommodate thorax expansion, then detection accuracy is improved, but device size increases
Solution Approach 1:
The elastic member is designed with specific mechanical parameters: it has high elasticity in the width direction to accommodate thorax expansion, while maintaining controlled tension in the length direction. The ratio of width to length is optimized so the elastic member can stretch sufficiently for accurate detection without requiring excessive device length.
Solution Approach 2:
The elastic member uses material composition and structural design that provides anisotropic properties: high elasticity in the width direction for thorax accommodation, while maintaining sufficient tensile strength and controlled elasticity in the length direction for accurate signal transmission to the piezoelectric film.
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
This design enhances detection accuracy and enables significant size reduction while maintaining sensitivity, suitable for various applications including breathing and heartbeat monitoring.
Implementation Method 1
a piezoelectric film, which exhibits piezoelectric effect in a length direction
Data Source
AI summary
Problem: To provide a body movement detection sensor using a piezoelectric film which improves detection accuracy and has a structure to allow for size reduction. Solution: A body movement detection sensor includes a sensor section having a piezoelectric film, a right belt member extending from a right side of the sensor section, a left belt member extending from a left side of the sensor section, and an engagement member configured to engage an end portion of the right belt member and an open-end portion of the left belt member with each other. In the body movement detection sensor, the piezoelectric film exhibits piezoelectric effect in a length direction, the right belt member and the left belt member have substantially no elasticity, the body movement detection sensor further includes an elastic sheet directly or indirectly connected to the right belt member and the left belt member, the piezoelectric film and the elastic sheet are arranged substantially without irregularities when viewed from a side, and the elastic sheet has a maximum amount of expansion larger than an amount of change of a thorax during breathing and has a length equal to or smaller than one-sixth of a total length of the right belt member and the left belt member.