Capacitive Sensor Noise Filtering for Indoor Localization
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Solution Overview
Problem
Existing capacitive sensors operating in load mode have limited sensing ranges and are prone to interference from electric and electromagnetic noise, making them ineffective for indoor activity monitoring beyond short distances due to their small size and high sensitivity, which complicates installation and increases costs.
Innovation Solution
A system that filters the time evolution of capacitance detected by a load mode capacitive sensor to reduce noise levels, allowing for extended sensing ranges without increasing sensor size, using a combination of data processing techniques and digital filters to enhance sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If small-size capacitive sensors are used, then device complexity and cost are reduced, but sensing range is limited to short distances
Solution Approach 1:
The sensing space is divided into multiple zones using an array of discrete capacitive sensors rather than one large sensor. Each sensor operates independently in load mode, and their collective data provides comprehensive spatial coverage, effectively extending the overall sensing range while keeping individual sensors small and simple
Solution Approach 2:
The capacitive sensors operate in load mode, using the human body or objects of interest as the second plate, eliminating the need for complex two-plate configurations. This universal approach allows the same simple sensor design to be used throughout the monitoring space, reducing device complexity while maintaining extended sensing capability through spatial distribution
2Measurement precision
If high sensitivity load mode capacitive sensors are used, then sensing capability is improved, but interference from electric and electromagnetic noise increases
Solution Approach 1:
The system continuously monitors capacitance changes and uses signal processing algorithms to distinguish genuine objects of interest from noise sources. By analyzing temporal patterns and comparing readings across multiple sensors, the system provides feedback-based discrimination that maintains high sensitivity while rejecting electromagnetic and electric noise
Solution Approach 2:
Signal processing algorithms act as intermediaries between the raw capacitive measurements and the final detection output. These algorithms filter and process the high-sensitivity sensor signals, separating true objects of interest from noise sources, thereby preserving sensing capability while eliminating harmful interference
3Area of stationary object
If floor-based capacitive sensing devices are installed, then sensing coverage is improved, but installation complexity and cost increase
Solution Approach 1:
Instead of installing large floor-based sensing systems, the solution segments the sensing function across multiple small, discrete capacitive sensors that can be mounted on existing surfaces. This approach achieves comprehensive spatial coverage while avoiding complex floor installation, reducing both device complexity and installation burden
Solution Approach 2:
The system transitions from two-dimensional floor-based sensing to three-dimensional spatial sensing by distributing sensors throughout the monitoring volume. This allows comprehensive coverage to be achieved through vertical and lateral distribution of simple sensors rather than extensive floor coverage, simplifying installation while maintaining sensing effectiveness
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 significantly extends the range of capacitive sensors, enabling effective low-cost, low-power, tag-less monitoring of human presence and location within indoor environments, overcoming limitations of existing small-size sensors by reducing noise and improving sensitivity.
Implementation Method 1
Capacitive sensors use capacitive transducers that can operate in one of the following modes: load mode - it needs only one plate on the transducer because it uses the human body or any other object of interest as a constant-potential second plate. The distance between the transducer and the body is one of the factors that change its capacitance
Implementation Method 2
shunt mode - it uses transducers with two plates. The human body partially shields the electrical field between the plates
Data Source
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AI summary
The invention relates to a system and a method for localizing an object of interest in a monitored space. The system comprises a plurality of capacitive sensors (2) for sensing changes in the status of a space, adapted to electrically interact in a contactless way with a ground surface so as to provide a capacitance varying on the basis of such changes, and adapted to detect at least a time evolution of said capacitance and to produce a capacitance- depending signal, a filtering unit (25) configured for reducing the noise level in said time evolution of such capacitance by filtering the capacitance-depending signal provided by the capacitive sensors (2), so that corresponding filtered signals are produced, and a central device in signal communication with said capacitive sensors (2). The central device is configured for acquiring the filtered signals of each capacitive sensor (2), and for determining the position of the object of interest inside said space by inferring at least a distance of said object on the basis of the filtered signals acquired from at least one of the sensors (2) detecting said object, and by combining said at least a distance with positional data defining the positions of said plurality of capacitive sensors (2) in the monitored space.