Hand-Held Tool Grip Sensing With Grounded Interference Shielding
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Solution Overview
Problem
Hand-held machine tools with capacitive sensors are prone to incorrect detections due to interference from nearby components, leading to potential operational issues.
Innovation Solution
Grounding elements are strategically placed around the capacitive sensor elements to shield them from interference, ensuring accurate detection only occurs in desired regions by connecting them to the machine tool's negative pole or grounding line, and using a control device to manage sensor interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a capacitive sensor element is arranged in the grip region to detect user's hand, then the machine tool can be actuated via a power switch, but the drive device can have a negative impact on the sensor functionality and lead to incorrect detection
Solution Approach 1:
A grounded element is introduced as an intermediary component between the capacitive sensor element and the drive device. This grounded element acts as a shield that blocks the electromagnetic interference from the drive device from reaching the sensor element, thereby maintaining sensor detection accuracy while allowing the drive device to function normally.
Solution Approach 2:
The electrical potential of the element in the grip region is changed from floating or active to grounded (zero potential). By grounding the element, its electrical parameters are modified to create a reference potential that is immune to interference from the drive device, thereby improving the reliability of capacitive sensing in the grip region.
2Measurement precision
If a capacitive sensor element is used for detection, then the machine tool can detect user's hand presence, but contact in undesired regions of the sensor may lead to false detection
Solution Approach 1:
The sensor system is segmented into multiple regions by selectively grounding specific elements. The grip region elements are left ungrounded to maintain sensitivity for hand detection, while other elements are grounded to create dead zones that prevent false detection from contact in undesired regions.
Solution Approach 2:
Different electrical properties are applied to different regions of the sensor system. The grip region maintains capacitive sensitivity for detection, while other regions are grounded to have zero electrical potential, creating local zones with different functional qualities - detection zones and non-detection zones.
3Reliability
If grounding elements are added to shield the capacitive sensor, then incorrect detection risk is reduced, but the device complexity increases
Solution Approach 1:
Existing structural elements of the machine tool are assigned multiple functions: they serve both as mechanical components and as grounding elements for electromagnetic shielding. This eliminates the need for separate shielding components, reducing overall device complexity while maintaining reliability.
Solution Approach 2:
The machine tool's own electrical system provides the grounding function needed for sensor protection. The existing power supply and grounding infrastructure of the tool is utilized to ground the shield elements, rather than requiring an external or separate grounding system.
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 approach significantly reduces the risk of incorrect detections by shielding the sensor elements from interference, allowing precise and reliable operation of the machine tool only when a user's hand is present in the intended detection region.
Implementation Method 1
at least one capacitive sensor element operatively connected to the control device is provided
Implementation Method 2
at least one element of the machine tool that is arranged in the region of the capacitive sensor element is grounded
Data Source
AI summary
A hand-held machine tool (1) including a drive device (4) by which a tool that can be brought into operative connection with the machine tool (1) can be actuated, with a control device (8) for actuating the drive device (4) and at least one capacitive sensor element (30, 35) operatively connected to the control device (8) being provided. The at least one element (2, 75) of the machine tool that is arranged in the region of the capacitive sensor element (30, 35) is grounded.