A Millimeter-Scale Rolling Microrobot Driven by a Micro-Geared Ultrasonic Motor

摘要

We present a millimeter-scale rolling microrobot driven by a set of a micro ultrasonic motor and a micro planetary gear train. The micro ultrasonic motor, consisting of a metallic cube with a side length of 2 mm, can produce a torque of 60 μNm and speed exceeding 4500 rpm. By attaching a micro planetary gear train with a gear ratio of 64, the assembled geared motor obtains high torque that can lift a payload with a maximum torque of 1 mNm. The prototype microrobot, with continuously rolling wheels driven by the geared motor, measures 14 mm in length, 10 mm in width, and 7 mm in height and weighs 640 mg. This microrobot is one of the smallest and most powerful mobile robots available at the millimeter scale. In the experiments, the microrobot is operated on planes with the slopes of 0 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , 15 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , 30 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> , and 45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> for evaluating its locomotion performance. The microrobot reaches a velocity of 5.6 mm/s on a horizontal plane and maintains its speed even on sharp slopes with a sufficiently high friction coefficient, even though slopes with low friction reduce the velocity owing to the slip of wheels.