An optical waveguide ridge has a side with a flat portion extending uniformly from a top of the ridge to a surface of a semiconductor substrate, the flat portion being in contact with an exposed surface of the substrate. The method for drive-controlling electric machinery, in which a multiphase motor is used as a driving source of an assist mechanism, is performed by a control unit including a driving circuit for driving the multiphase motor. Permanent magnets are mounted in permanent magnet insertion holes located at the tip of each of the individual propeller blades. A resilient member is coupled to the base portion of the metallic pin-lock and to a mobile phone housing.