Piezoelectric MEMS Sensor for Intrusion Detection
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Solution Overview
Problem
Existing security sensors, particularly those with MEMS accelerometric transducers, face challenges in distinguishing between intrusion signals and wind-induced oscillations, leading to false alarms and missed detection of weaker intrusion attempts like cutting through metal meshes or break-ins in closed environments.
Innovation Solution
A security sensor system utilizing a combination of piezoelectric and MEMS accelerometric transducers with a processing unit that applies weighted signal fusion to differentiate between intrusion and environmental events, using a calculation function to process digital samples from both transducers and adjust weighting coefficients based on event types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MEMS accelerometric transducers are used to detect fence oscillations, then sensitivity to intrusion movements is improved, but false alarms increase due to wind-induced oscillations
Solution Approach 1:
The patent combines two different transducer types (piezoelectric and MEMS accelerometric) into a single security sensor system. The piezoelectric transducer detects mechanical stress from cutting attempts, while the MEMS accelerometric transducer detects oscillations from climbing or wind. By merging these complementary detection capabilities and processing their signals together, the system achieves both high sensitivity to intrusions and reliability by distinguishing true threats from wind-induced false alarms through signal comparison and analysis.
2Measurement precision
If sensitivity is increased to detect weaker intrusion signals, then detection capability is improved, but false alarms from wind increase
Solution Approach 1:
The patent introduces a processing unit as an intermediary that receives and analyzes signals from both piezoelectric and MEMS accelerometric transducers. This intermediary component compares signals from both sensors, identifies patterns characteristic of wind versus intrusion, and makes intelligent decisions about alarm generation. The processing unit acts as a mediator that filters out wind interference while preserving genuine intrusion signals, enabling the system to maintain high sensitivity without proportionally increasing false alarms.
3Reliability
If algorithms reduce sensitivity in wind conditions, then false alarms are reduced, but detection of weaker intrusion attempts is lost
Solution Approach 1:
The patent implements dynamic, adaptive sensitivity control through its processing unit that continuously analyzes signals from both transducers. Rather than uniformly reducing sensitivity during wind conditions, the system dynamically adjusts its response based on real-time signal characteristics. The processing unit can selectively lower the response threshold for wind-induced oscillations while maintaining high sensitivity for cutting attempts detected by the piezoelectric transducer, achieving both false alarm reduction and sustained intrusion detection capability through dynamic parameter adjustment.
4Reliability
If piezoelectric transducers are used for stress detection, then immunity to environmental disturbances is improved, but device size increases
Solution Approach 1:
The patent merges a piezoelectric transducer with a MEMS accelerometric transducer in a single integrated security sensor. The piezoelectric component provides environmental immunity and detects cutting attempts through stress detection, while the compact MEMS accelerometer adds oscillation detection capability for climbing intrusions or wind events. This combination allows the system to maintain the environmental robustness of piezoelectric sensors while incorporating the space-efficient benefits of MEMS technology, achieving comprehensive detection without excessive size increase.
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 system effectively detects various intrusion and environmental events, reducing false alarms and improving sensitivity to weaker signals, enabling accurate detection of attempts like cutting or climbing, while maintaining robustness against environmental disturbances.
Implementation Method 1
an anti-intrusion security system comprising so-called 'piezodynamic' security sensors is described, which, by virtue of a piezoelectric disc and a mobile inertial mass
Implementation Method 2
Security sensors are also known which use accelerometric transducers, in particular, MEMS accelerometers
Data Source
AI summary
A security sensor is provided which has a container body and a signal acquisition and processing module housed in the container body. The signal acquisition and processing module has a piezoelectric transducer configured to convert a mechanical stress to which the piezoelectric transducer is subjected into a first electrical signal, an accelerometric transducer configured to convert an acceleration to which the accelerometric transducer is subjected into a second electrical signal, and processing unit operatively connected to the piezoelectric transducer and to the accelerometric transducer for receiving the first and second electrical signals. The accelerometric transducer is a MEMS accelerometric transducer.