Trigger Potentiometer Range Limiting for Fault Detection
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Solution Overview
Problem
Existing electric tools with variable speed functions using electrical position indicators, such as potentiometers, face challenges in detecting failures like fully open or fully short conditions, which can lead to unexpected tool behavior or safety risks.
Innovation Solution
Configuring the electrical position indicator to operate only within a predefined middle range (e.g., 5% to 95% of its total range) and using a control unit to detect deviations from this range, allowing for the identification of potential faults and prevention of unsafe power-on conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrical position indicator operates across its full range, then the complete operational range of the trigger is covered, but failures at extreme positions (fully open or fully short) cannot be detected
Solution Approach 1:
The system performs preliminary detection of position indicator failures by monitoring signals before they cause unsafe operations. The control unit checks for fully open or fully short conditions during normal operation, enabling early detection and prevention of unintended tool activation.
Solution Approach 2:
The patent changes the operational parameters of the position indicator by defining specific operational range limits (e.g., 5% to 95% of full scale). By constraining the indicator to operate within this middle range and monitoring for deviations, the system can detect failures while maintaining full trigger functionality.
2Ease of operation
If the position indicator operates at extreme positions, then full trigger range is utilized, but unsafe power-on conditions may occur due to undetected failures
Solution Approach 1:
The control unit continuously monitors the position indicator signal and provides feedback to detect fully open or fully short conditions. This feedback mechanism enables real-time detection of failures that could lead to unsafe operations, allowing the system to alert the user or prevent unintended activation.
Solution Approach 2:
The system applies preliminary anti-action by detecting potential failures before they can cause harmful effects. By monitoring for extreme position signals during normal operation, the system prevents unsafe power-on conditions from occurring in the first place.
Data Source
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AI summary
An electric hand tool (100) that includes an electric motor (120), an electrical position indicator (140) for operation by a user, and a control unit (130) for controlling power delivery from a power supply (110) to an electric motor (120), based on signals received from the electrical position indicator (140). The electrical position sensor may be coupled to a trigger (150) operable by a user, and the electrical position sensor may be configured to detect the relative position of the trigger (150) and to only operate in the middle of its possible range. The control unit (130) may determine if the signals received from the electrical position indicator (140) are out of a defined range. If the signals received from the electrical position indicator (140) are out of a defined range, the control unit (130) may register a fault, such as a fully open and/or fully short fault.