Back to results
US 11,571,831 B2Granted
System and method for kickback detection based on blade speed in a power tool
AssigneeRobert Bosch GmbH
InventorsDeepak Padmanabhan, Brett Huber
Life of this patent
Estimating the term…
Abstract
A method of detecting and mitigating kickback in a saw includes identification of a running average speed (RPM) of a saw blade, the speed at a given time sample relative to the running average speed, the percentage change in speed from one speed sample to the previous speed sample, and the percentage change in average speed based on the current speed of the saw blade. If the identified speed profile from the samples indicates a kickback is imminent, then the saw identifies an imminent kickback event and removes power from the saw motor to mitigate kickback.
Claims13
A method of operating a power saw, comprising:
- detecting whether a kickback event of a saw blade of the power saw has occurred by:
- sensing a rotation speed of the saw blade using a sensor, and using the sensor to output a signal indicative of the rotation speed of the saw blade as the saw blade is being operated;
- using a controller to sample the output signal at a predetermined sampling rate to determine the rotation speed of the saw blade;
- after each sample of the output signal, determining a current average blade speed, the current average blade speed corresponding to an average of the rotation speed indicated by a current sample of the output signal with the rotation speeds indicated by a predetermined number of previous samples of the output signal;
- and
- after determining the current average blade speed, comparing the current average blade speed with a previous average blade speed, the previous average blade speed corresponding to the current average blade speed calculated for a previous sample of the output signal,
- wherein the comparison of the current average blade speed with the previous average blade speed further comprises:
- determining a first percentage difference between the current average blade speed and the previous average blade speed, and
- determining that the kickback event of the saw blade has occurred when the first percentage difference is greater than a first predetermined percentage difference threshold value, and
- wherein the method further comprises:
- comparing the rotation speed indicated by the current sample to the rotation speed indicated by the previous sample;
- determining a second percentage difference between the rotation speed indicated by the current sample to the rotation speed indicated by the previous sample;
- and
- determining that the kickback event of the saw blade has occurred when the first percentage difference is greater than a first predetermined percentage difference threshold value and the second percentage difference is greater than a second predetermined percentage difference threshold value.
11 more elements
Dependencies are inferred from the claim text.