<p>As a daily means for transportation, a personal mobility (PM) attracts attention. However, most of conventional PM are expensive and unavailable to use freely on Japanese public roads because of Road Traffic Act. Therefore, our laboratory developed a PM"Oteller"with a driving wheel for the purpose of low cost and using on the public roads freely. However, the PM has some problems; its driving speed becomes uncontrollable by sunlight that changes DC offset of signals from an optical sensor for measuring the speed, and a fall of the driver by a sudden stop of the driving wheel due to battery exhaustion. In this paper, the speed becomes controllable under the sun by using a circuit which converts the signals with AC coupling. In addition, the fall is prevented by stopping the PM automatically while gently decelerating after detecting battery exhaustion.</p>