When an external force applied condition that an external force that causes a decrease in a rotational speed of an electric motor is applied to the contact member moved by the electric motor is satisfied while the actuation controller is performing a first control for continuously performing a process of providing the electric motor with a command value that depends on an error between an actual rotational speed of the electric motor and a first target rotational speed so as to cause the actual rotational speed to approach the first target rotational speed, then the actuation controller, subsequent to the first control, performs a second control for providing the electric motor with a command value that allows the actual rotational speed of the motor to be equal to, and to fall below, the first target rotational speed at a time of the external force applied condition becoming satisfied.