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Micromotors are of great interest not only for the miniaturization of current products but also for the realization of future micromachines that can explore challenging environments. The speed of downsizing actuators is slower than that of semiconductor components, but developments over the last two decades have overcome several difficulties and enabled engineers to start designing applications. In this paper, we review the existing micromotors ranging from famous papers to state-of-the-art, in particular recent developments and their applications. We deal with three representative principles for rotary and linear micromotors: electromagnetics, electrostatics, and piezoelectricity. Another purpose of this paper is to suggest design criteria and physical limitations on these principles for engineers who design millimeter-scale automation devices. Incorporating micromotors can permit space saving and improve design flexibility in application designs, such as smartphones and medical devices.

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We propose a miniature rotating mirror system using a micro-ultrasonic motor that employs a 45 • angle mirror as its rotor for enlarging the angle of view of cameras. The motor assy, measuring 2 mm in diameter and 4 mm in length, is one of the smallest motors and is expected for medical applications such as endoscopes. In this paper, we build a micromirror assembly, install it into a visual feedback system with an optical system, and demonstrate a motor control with a quick and wide angle-of-view observation. The high-speed camera vision embedded in the system measures the quick motion of the motor in real-time and enables accurate positioning of the mirror angle by p-control using burst waves. The proposed system demonstrates the visual feedback control of the miniature rotating mirror to the angle information obtained by the high-speed camera. The feasibility of the mirror system driven by the micro-ultrasonic motor is shown via demonstration.