DETECTION SYSTEM FOR POWER TOOL
First Claim
1. A method of sensing contact between an object and a movable blade of a power tool, the power tool comprising an excitation plate positioned proximate and capacitively coupled to the movable blade, the method comprising:
- providing a drive signal to the excitation plate to capacitively couple the drive signal to the movable blade;
sensing a blade current signal indicative of the instantaneous current drawn by the movable blade;
generating an in-phase component signal and a quadrature component signal from the blade current signal;
calculating, by a circuit in communication with the excitation plate, an energy of the blade current signal considering the in-phase component and the quadrature component; and
comparing by the circuit the energy of the blade current signal to an adaptive trigger threshold to detect contact between the blade and the object based on whether the energy of the blade current signal is greater than the adaptive trigger threshold, wherein the adaptive trigger threshold is based on a sum of a first plurality of values comprising a fixed direct current (DC) offset, and a mean of the energy of the blade current signal.
1 Assignment
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Accused Products
Abstract
A power tool is disclosed. The power tool may comprise a movable blade and a detection system for detecting contact between the blade and an object. The detection system may comprise an excitation plate capacitively coupling the drive signal to the movable blade and a circuit in communication with the excitation plate. The circuit may be configured to generate an in-phase component signal and a quadrature component signal from a blade current signal indicative of the instantaneous current drawn by the movable blade and calculate an energy of the blade current signal considering the in-phase component and the quadrature component. The circuit may be further programmed to compare the energy of the blade current signal to an adaptive trigger threshold to detect contact between the blade and the object based on whether the energy of the blade current signal is greater than the adaptive trigger threshold. The adaptive trigger threshold may be based on a sum of a first plurality of values comprising a fixed direct current (DC) offset, and a mean of the energy of the blade current signal.
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Citations
17 Claims
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1. A method of sensing contact between an object and a movable blade of a power tool, the power tool comprising an excitation plate positioned proximate and capacitively coupled to the movable blade, the method comprising:
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providing a drive signal to the excitation plate to capacitively couple the drive signal to the movable blade; sensing a blade current signal indicative of the instantaneous current drawn by the movable blade; generating an in-phase component signal and a quadrature component signal from the blade current signal; calculating, by a circuit in communication with the excitation plate, an energy of the blade current signal considering the in-phase component and the quadrature component; and comparing by the circuit the energy of the blade current signal to an adaptive trigger threshold to detect contact between the blade and the object based on whether the energy of the blade current signal is greater than the adaptive trigger threshold, wherein the adaptive trigger threshold is based on a sum of a first plurality of values comprising a fixed direct current (DC) offset, and a mean of the energy of the blade current signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A power tool comprising:
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a movable blade; and a detection system for detecting contact between the blade and an object, the detection system comprising; an excitation plate capacitively coupling the drive signal to the movable blade; and a circuit in communication with the excitation plate, wherein the circuit is configured to detect contact between the object and the movable blade based on whether periodicity in at least one signal selected from the group consisting of the blade current signal, a signal derived from the blade current signal, the blade voltage signal, and a signal derived from the blade voltage signal exceeds a predetermined threshold.
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16. A power tool comprising:
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a movable blade; and a detection system for detecting contact between the blade and an object, the detection system comprising; an excitation plate capacitively coupling the drive signal to the movable blade; a signal sensor coupled to the excitation plate for generating a first signal selected from the group consisting of a blade current signal indicative of the instantaneous current drawn by the movable blade and a blade voltage signal indicative of the instantaneous voltage drop between the excitation plate and the blade; and a circuit in communication with the excitation plate, wherein the circuit is configured to detect contact between the object and the movable blade based on whether a correlation between the first signal and one of a plurality of signal templates exceeds a predetermined threshold, wherein each signal template corresponds to energy levels of the first signal indicative of contact between the object the movable blade.
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17. A power tool comprising:
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a movable blade; and a detection system for detecting contact between the blade and an object, the detection system comprising; an excitation plate capacitively coupling the drive signal to the movable blade; a signal sensor coupled to the excitation plate for generating a signal selected from the group consisting of a blade current signal indicative of the instantaneous current drawn by the movable blade and a blade voltage signal indicative of the instantaneous voltage drop between the excitation plate and the blade; and a circuit in communication with the excitation plate, wherein the circuit is configured to detect contact between the first object and the movable blade based on whether high frequency artifacts are present in the signal.
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Specification