Study of the Velocity and Direction of Piezoelectric Robot Driven by Traveling Waves

Self-running piezoelectric robots have the advantages of being low cost, high load ratio and fast speed of operation, as well as showing few limitations in confined spaces or for underwater applications. Controlling the speed of motion of such robots by adjusting the standing wave ratio (SWR) along the vibration plate of the robot is important. Compared to the conventional dual-mode excitation method which is based on the adjustment of the excitation frequency, f, a novel SWR-based control method, using the adjustment of the temporal phase shift, θ, has been first derived by the authors. It has been found that the traveling wave component could be maximized using both methods, either by setting the value of f to the root mean square of the two adjacent modal frequencies, or by programming θ to have a sum of π when added to the spatial phase difference. It can be seen that using the “θ-based” traveling wave control method, smoother motion and higher resolution of the motion speed is achieved. In this article, by using the novel θ-based method to drive the robot, its motion characteristics, such as voltage-speed, load capacity and ability to move on different surface materials, have been tested through a series of experiments carried out and reported.

I. Introduction

Self-running piezoelectric robots have many potential applications for use in confined spaces [1], [2] or underwater [3], [4], [5], due to their favorable characteristics, such as having a simple structure, being low cost to manufacture and having both a high load ratio and fast speed of operation, as well as no restrictions on the material on which they can walk. Compared to traditional robots with movable joints, piezoelectric robots generate neither strong electromagnetic radiation, nor produce undesired noise or dust in their operation. These advantages allow the self-running piezoeletric robot to have a potential amphibious ability that can enable it to “fly on the ground”—to do this on the ground with any material and to “dive in water” in a liquid medium.