One of the most dangerous phenomena associated with chainsaw use is kickback. This occurs when the upper quadrant of the chainsaw bar’s tip catches on the work-piece, accelerating the saw toward the user. Safety devices currently installed on chainsaws rely on the rotational acceleration of the saw to move a difficult-to-design mechanical linkage and activate a band brake. Even with a well-designed braking linkage, the saw must rotate through a large angle (approximately 45°) before actuating the brake. A more effective kickback detection and chain-braking system is needed—one that is capable of (i) early detection of the kickback event and (ii) rapid braking of the moving chain. This paper deals with a method of detecting such a kickback event. The approach taken in this work determines the key kinematic parameters associated with kickback using an electronics package of accelerometers and a gyroscope attached to a typical chainsaw. Testing consisted of (i) performing a series of normal cuts through wooden poles, and (ii) purposely initiating kickback via several common scenarios. Data analysis consisted of comparing magnitude, duration, and frequency of sensor output between normal cutting and kickback scenarios. After data filtering, a method of scaling factor variation was used to extract the optimum detection algorithm of a single gyroscope with appropriate signal conditioning, Kickback is detected within 30 milliseconds, before the saw loses contact with the work-piece. The gyroscope magnifies the signal corresponding to the kickback event while attenuating signals corresponding to normal use. This method presents the possibility of a significantly improved chainsaw kickback control system.

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