Handheld Electric Tool Capacitive Grip Sensing for Touch Accuracy
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Solution Overview
Problem
Existing handheld electric tools with capacitive sensors face issues in distinguishing between fingertip contact capacitance and proximity capacitance, leading to erroneous touch detection or loss of detection, increasing sensor complexity and electronics complexity.
Innovation Solution
The capacitive sensor system is designed with a length greater than the expected maximum length of the object to be detected, allowing contact points anywhere in the gripping region, and varying sensitivity to minor hand movements, using multiple sensor elements arranged in parallel to ensure accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor electrode couples with the approaching hand before contact with the fingertip to detect proximity, then proximity detection capability is improved, but erroneous touch detection occurs due to inability to distinguish proximity capacitance from contact capacitance
Solution Approach 1:
The sensor system is divided into multiple sensor elements (first sensor element, second sensor element, etc.) arranged in different gripping regions. Each sensor element independently detects capacitance changes in its specific region, allowing the system to segment the detection space and distinguish between proximity effects and actual touch contacts by comparing signals from different segments.
Solution Approach 2:
The control device acts as an intermediary that processes signals from multiple sensor elements. It evaluates the relationship between capacitance changes from different sensors to determine whether a touch contact has actually occurred, filtering out false proximity detections through intermediate signal processing and logical evaluation.
2Measurement precision
If the sensor electrode area is increased to improve detection sensitivity, then sensitivity to minor hand movements is improved, but device complexity increases due to larger sensor size and more extensive sensor electronics
Solution Approach 1:
Instead of using one large complex sensor, the system segments the sensing function across multiple smaller sensor elements distributed in different gripping regions. This segmentation maintains high sensitivity while distributing the electronic complexity across manageable components that can be independently processed.
Solution Approach 2:
The sensor elements are arranged in different spatial dimensions (different gripping regions, different orientations) rather than simply increasing the area of a single sensor. This dimensional distribution achieves comprehensive coverage and high sensitivity without requiring a single large sensor element, thereby reducing overall system complexity.
3Reliability
If multiple sensor elements are arranged in parallel in the gripping direction, then detection coverage and reliability are improved, but device complexity increases due to additional sensor elements and control logic
Solution Approach 1:
Multiple sensor elements serve universal detection functions across different gripping regions. Each sensor element can detect both proximity effects and touch contacts in its respective region, and the control device uses universal evaluation logic to process signals from all sensors, reducing the need for region-specific processing complexity.
Solution Approach 2:
The control device continuously monitors and evaluates the relationship between signals from multiple sensor elements, using feedback logic to determine actual touch contact based on the pattern of capacitance changes across sensors. This feedback mechanism improves reliability by cross-validating detections while managing complexity through systematic signal evaluation.
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 sensitivity to minor hand movements, reduces erroneous detection, and allows safe operation by specifying desired gripping positions, improving the reliability and simplicity of the sensor system.
Implementation Method 1
A handheld electric tool with a capacitive sensor is known from practice. By means of a capacitive sensor, for example, a power switch may be activated
Data Source
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AI summary
The present invention relates to a handheld electric tool, comprising a drive device by means of which an insert operably connectable to the electric tool can be actuated, and a controller for actuating the drive device, and at least one capacitive sensor element operably connected to the controller. The electric tool further comprising at least one gripping part, the gripping part comprising a gripping region defining a gripping direction, for holding and guiding the electric tool by means of one or both hands of a user contacting the gripping region at least partially around the gripping direction. A length of the at least one sensor element in the gripping direction is not less than a length of the gripping region.