Power Tool Implement Motion Detection Using Electrical Signal Analysis
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Solution Overview
Problem
Existing power tool detection systems are unreliable in identifying the movement of an implement when the actuator is deactivated, often requiring external sensors and increasing complexity.
Innovation Solution
A method and system that utilize a clock source to generate a time-varying electrical signal passing through the implement, with a controller sampling and processing the signal to determine if the implement is moving or not by analyzing parameters such as max-min values or variance, without the need for additional external sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external sensors are used to detect implement movement after actuator deactivation, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The implement itself serves as the sensing element by utilizing its inherent electrical properties (capacitance, inductance, or resistance) to generate detectable signals during movement. The controller monitors these natural electrical characteristics without requiring external sensors, making the implement self-sufficient for detection purposes while reducing system complexity
Solution Approach 2:
The electrical signal infrastructure already present in the power tool (clock source, signal pathways, controller) is made to serve dual purposes: both actuator control and movement detection. This multi-functionality eliminates the need for separate external sensing systems while maintaining reliable detection capability
2Measurement precision
If additional external sensors are added to detect implement movement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
External mechanical or optical sensors are replaced with an electrical field-based detection system that utilizes the implement's inherent electrical properties. The controller measures changes in capacitance, inductance, or resistance signals generated by the implement's movement through the electrical field, providing precise measurement without mechanical or optical components
Solution Approach 2:
The system detects movement by monitoring changes in electrical parameters (capacitance, inductance, or resistance) of the implement as it moves through the electrical field generated by the clock source. These parameter changes provide precise movement detection information while using only the existing electrical infrastructure of the power tool
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
Enables accurate identification of implement movement within power tools even after the actuator is deactivated, reducing complexity and reliance on external sensors, thereby enhancing safety and operational efficiency.
Implementation Method 1
The capacitance between the first object and the saw table (or power line ground if one is present) is in the range of approximately 30-50 pF in the embodiment of FIG. 1.
Implementation Method 2
The signal on line 26 is indicative of the instantaneous current drawn by the blade 22.
Data Source
AI summary
A method of operating a power tool identifies motion of an implement in a power tool. The method includes obtaining a plurality of samples of an electrical signal that passes through the implement, identifying a parameter for the plurality of samples corresponding to a variation in values of predetermined groups of samples in the plurality of samples, updating a status for the implement with a first status indicating that the implement is not moving with reference to the identified parameter being less than a predetermined threshold, and updating a status for the implement with a second status indicating that the implement is moving with reference to the identified parameter being greater than the predetermined threshold.