Power Tool Fastener Setting via Current Monitoring
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Solution Overview
Problem
Existing fastener driving power tools face challenges in accurately detecting the stopping position of fasteners due to noisy motor current signals, leading to inaccuracies and false triggers of the electronic clutch, particularly during 'cam out' conditions where the drill bit slips and re-engages.
Innovation Solution
The implementation of a rotary potentiometer/switch assembly and advanced algorithms that monitor motor current changes and torque settings to improve the accuracy of fastener setting, avoiding false triggers by ignoring sudden increases in motor current following a 'cam out' condition and using linear regression to filter noise in current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If motor current behavior is monitored to detect fastener stopping position, then automated fastener setting is enabled, but measurement precision deteriorates due to noisy sensor signals
Solution Approach 1:
The system performs preliminary actions by detecting cam-out conditions (sudden current drops) before they can cause false triggers. When a cam-out is detected, the algorithm prepares by resetting its detection state, so that subsequent current increases are recognized as cam-out recovery rather than fastener seating events. This preliminary detection and preparation prevents the measurement precision deterioration that would otherwise occur.
Solution Approach 2:
The system implements feedback by continuously monitoring motor current behavior and using this information to adjust its detection algorithm. The algorithm analyzes the sequence of current changes (drops indicating cam-out, increases indicating potential seating) and uses this feedback to determine whether to accept or reject current increase events as valid fastener stopping signals. This feedback mechanism enables automated fastener setting while compensating for signal noise.
2Extent of automation
If sudden increases in motor current are used to trigger electronic clutch, then fastener setting automation is achieved, but reliability deteriorates due to false triggers after cam out conditions
Solution Approach 1:
The algorithm performs preliminary detection of cam-out conditions by monitoring for sudden current drops. When a cam-out is detected, the system preliminarily identifies this event and prepares by resetting its trigger acceptance state. This preliminary action ensures that subsequent current increases are not mistakenly interpreted as valid fastener seating events, thereby preventing false clutch triggers and improving reliability.
Solution Approach 2:
The system uses feedback from continuous current monitoring to dynamically adjust clutch triggering behavior. By analyzing the sequence of current changes and providing feedback to the control algorithm, the system can distinguish between genuine fastener seating events and cam-out recovery events. This feedback mechanism enables reliable automated fastener setting by preventing false triggers while maintaining automation.
3Measurement precision
If linear regression is applied to filter noise in current measurements, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical noise filtering hardware with a computational approach using linear regression algorithms. Instead of using physical filters or additional sensors, the system uses software-based statistical analysis to distinguish signal from noise in the current measurements. This substitution achieves improved measurement precision while avoiding the complexity of additional mechanical or electronic filtering components.
Data Source
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AI summary
A method is provided for setting a fastener in a workpiece. The method includes: monitoring a parameter of the power tool during operation of the power tool, where the parameter is indicative of the placement of a fastener being driven by the power tool in relation to the workpiece; detecting a change in the parameter, where the detected change in the parameter indicates that the power tool became disengaged with the fastener; modifying operation of the power tool in response to the detected change in the parameter; subsequently detecting a second change in the parameter; and interrupting transmission of torque to the output spindle in response the detected second change in the parameter, thereby properly setting the placement of the fastener in relation to the workpiece.