There is disclosed a mobile robot including an image processor that generates recognition information regarding a target object included in a taken image, and a main controller integrally controlling the robot based on this recognition information. The procedure first sets multiple areas adjacent to one another in an image expressed by master image data, where each of the multiple areas corresponds to each unit page to be printed. An epitaxial growth of a nitride-based compound semiconductor crystal is made with an initial transient epitaxial growth, which fills the voids, and a subsequent main epitaxial growth over the porous metal layer. The head portion of the cylinder is provided on one side thereof with a sensor mounting hole opening directly under an upstream end opening portion of an intake port. The planet wheels of the second set are supported by means of a resilient central element for radial displacement.