Touch Detection Algorithm for Capacitive Sensor Noise Suppression
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Solution Overview
Problem
Existing touch detection systems in electronic devices face challenges in simultaneously operating 3D gesture detection and 2D touch sensing systems due to interference, leading to missed quick touches and latency issues from conventional noise suppression methods like low-pass filtering.
Innovation Solution
A low-latency touch detection algorithm using a stochastic Unscented Kalman Filter to suppress sinusoidal noise, allowing a 3D gesture detection system to activate a touch controller with minimal delay and avoid interference, enabling simultaneous operation of 3D gesture recognition and 2D touch information systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low-pass filtering is applied to suppress power grid noise, then noise suppression is improved, but latency increases and quick touches are missed
Solution Approach 1:
The patent replaces the conventional low-pass filtering approach (analog signal processing) with a stochastic Unscented Kalman Filter (computational algorithm). This substitution allows for more sophisticated noise modeling that accounts for the specific characteristics of power grid interference (50/60 Hz sinusoidal patterns) while maintaining temporal resolution. The UKF uses a state-space model to predict and subtract noise components in real-time without the inherent phase lag of traditional filters, thus achieving noise suppression with minimal latency.
Solution Approach 2:
The patent changes the fundamental parameters of the filtering approach by transitioning from fixed cutoff frequency filters to adaptive state estimation. The Unscented Kalman Filter dynamically adjusts its noise modeling based on the actual signal characteristics, using process noise and measurement noise parameters to optimally weigh predictions versus observations. This allows the system to maintain sensitivity to rapid touch events while selectively attenuating power grid noise through statistically optimal parameter selection rather than fixed frequency-domain filtering.
2Adaptability or versatility
If 3D gesture detection system and touch controller operate simultaneously, then system versatility is improved, but mutual interference occurs
Solution Approach 1:
The patent extracts and separately models the noise characteristics generated by the 3D gesture detection system's transmit signal. By identifying the specific frequency components (50/60 Hz power grid noise) that result from the interaction between the CSS transmit signal and the touch controller, the system can selectively target and remove only these harmful frequency components. This extraction approach allows the beneficial signals from both systems to coexist while isolating and eliminating the specific interference patterns they generate when operating simultaneously.
Solution Approach 2:
The stochastic Unscented Kalman Filter acts as an intermediary processing stage between the raw sensor signals and the final touch detection output. This intermediate layer models the complex interaction between the CSS and touch controller signals, separating the useful touch information from the interference generated by simultaneous operation. The filter serves as a mediator that reconciles the conflicting signals by applying statistical models that distinguish between genuine touch events and artifacts caused by the other system's transmit signal.
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 algorithm effectively suppresses noise and reduces latency, enabling precise and high-resolution 2D touch detection without missing quick touches, while allowing for simultaneous operation of 3D gesture recognition and 2D touch sensing systems.
Implementation Method 1
A 3D gesture detection system is configured to work with a quasi-static alternating electric field, for example, using a 100-200 kHz square-wave signal fed to a transmitter electrode to build up such a field
Implementation Method 2
Touch detection systems are generally capacitive or resistive measurement systems that determine a change in capacitance or resistance caused by, for example, a finger touching a respective touch surface
Data Source
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AI summary
A system has a two-dimensional (2D) touch detection system operable to be activated and de-activated and an additional sensor operable in communication with the 2D touch detection system. The additional sensor is capable to determine whether a touch event has occurred or is about to occur and to activate the 2D touch detection system if a touch event has occurred or is about to occur.