#$%^&*AU2016101803A420161117.pdf#####ABSTRACT A power tool includes an electric motor, a functional accessory capable of being driven by the electric motor, a detection device for detecting a rotational speed of the electric motor, and a controller for controlling the electric motor with a control signal. The control is operable to estimate a load parameter according to a duty cycle of the control signal and the rotational speed of the electric motor such that the electric motor is caused to be operated by the controller with a lower rotational speed under a lower load and a higher rotational speed under a higher load.2/3 detecting the rotating speed 30 S of the electric motor 302 S<；the set rotational speed 303 NO YES reducing PWM increasing PW 04 305 alculating difference AF of the load parameter 306 AF>；F NO YES 307 A NO YES 308 AF>；I NO YES setting the rotational setting the rotational setting the rotational setting the rotationa speed to be S3 speed to be S2 speed to be SI speed to be SO 309 31 3 1 3 2 F IG. 2
