Preliminary evaluation and experimentation of the push-slip method for achieving micrometer and submicrometer step sizes with a miniature piezoactuated three-legged robot operating under high normal

Abstract

The NanoWalker is a miniature autonomous wireless robot under development. The robot is designed to accomplish complex tasks at the molecular and atomic scales. One concern is the total mass of the robot. With all the components including the mechanical structure and the complex electronic system necessary to embed the required functionality of throughput for such tasks, the mass of such a robot is estimated to be in the range of 100-200 grams depending on tradeoffs in the final design. With such a mass and limitations on the maximum voltage and current outputs that can be generated in a small form factor to deflect the piezo-ceramic legs with high-precision, a preliminary evaluation and experimentation phase of the motion behavior is essential prior to completing the final desing. It is shown both theoretically and experimentally that adequate motions are possible under such high normal forces. This was achieved through a new walking strategy referred to here as the push-slip method. The method uses the high normal forces combined with the resulting coefficient of friction between the termination of each leg and the walking surface to create initial opposite forces to the bending forces of each leg. These opposite forces, bounded by the maximum static force of friction, can be used for pushing or slipping through additional torque if the bending forces are applied reciprocal or in the direction of intended motions respectively. With the right parameters combined with tight and proper synchronizations of the legs, very effective motions can be achieved.