Capacitive sensing system for power cutting tool
First Claim
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1. A system for sensing contact between an object and a movable blade of a power cutting tool comprising:
- a plate positioned adjacent to a side of the moveable blade wherein the plate is for capacitively coupling a time-varying drive signal to the movable blade;
a current sensing element coupled to the plate for generating a current sense signal indicative of the instantaneous current drawn by the movable blade; and
a processor in communication with the current sensing element for detecting a condition indicative of contact between the object and the movable blade based on variations in both an in-phase current component signal and a quadrature current component signal, wherein the in-phase current component signal and the quadrature current component signal are generated from the current sense signal.
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Abstract
A capacitive sensing system for use with a power cutting tool of the type which has an exposed, moveable blade adjacent a work surface is disclosed. The sensing system drives an excitation voltage onto the exposed blade and monitors the current drawn from the blade, detects changes in the amplitude and phase and analyzes the characteristics of the changes to selectively trigger a reaction system.
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Citations
20 Claims
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1. A system for sensing contact between an object and a movable blade of a power cutting tool comprising:
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a plate positioned adjacent to a side of the moveable blade wherein the plate is for capacitively coupling a time-varying drive signal to the movable blade; a current sensing element coupled to the plate for generating a current sense signal indicative of the instantaneous current drawn by the movable blade; and a processor in communication with the current sensing element for detecting a condition indicative of contact between the object and the movable blade based on variations in both an in-phase current component signal and a quadrature current component signal, wherein the in-phase current component signal and the quadrature current component signal are generated from the current sense signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A system for sensing contact between an object and a movable blade of power cutting tool comprising:
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a plate adjacent to a side of the blade, wherein the plate is for capacitively coupling a time-varying drive signal to the movable blade; a current sensing element coupled to the plate for generating a current sense signal indicative of the instantaneous current drawn by the movable blade; an I/Q decomposition module in communication with the current sensing element that generates from the current sense signal an in-phase current component signal and a quadrature current component signal; and a signal variation detection module in communication with the I/Q decomposition module that detects the condition indicative of contact between the object and the movable blade based on variations in both the in-phase current component signal and the quadrature current component signal. - View Dependent Claims (13)
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14. A power cutting tool comprising:
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a movable blade; a table having an opening, wherein the movable blade is disposed in the opening such that a portion of the movable blade projects above the table; and a capacitive sensing system that senses contact between an object and the movable blade comprising; a plate adjacent to a side of the blade, wherein the plate is for capacitively coupling a time-varying drive signal to the movable blade; a current sensing element coupled to the plate for generating a current sense signal indicative of the instantaneous current drawn by the movable blade; and a processor in communication with the current sensing element for detecting a condition indicative of contact between the object and the movable blade based on variations in both an in-phase current component signal and a quadrature current component signal, wherein the in-phase current component signal and the quadrature current component signal are generated from the current sense signal. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification