Abstract
When driving force and braking force are simultaneously add to the model rotor system containing a direct current motor, the unbalance between two force occurs the vibration of the model rotor system. In the experiments, motor current and vibration of the model rotor system are measured. The following was obtained. (1) Variation in the current of the motor and vibration of the model rotor system were influenced by the configuration of brush in contact with the commutator. (2) The frequency of the rotor vibration equals to the natural frequency of the motor.
