Notch filter, external force estimator, a motor control device and a robot system

It is an object to dampen vibration components generated by the rotation of the motor. To solve this problem, the notch filter according to the embodiment includes a filtering unit, and a damping controller. Filtering unit acquires a signal including vibrational components generated with the rotation of the motor, performing the attenuation of the vibration component. Attenuation control unit controls the attenuation amount of the attenuation according to the rotational speed of the motor.