5-DOF cone-shaped piezoelectric positioning robot for optical systems

The paper presents a numerical and experimental investigation of a 5-DOF piezoelectric robot that is used for angular and planar positioning of optical devices and systems. The robot has a simple design and consists of an aluminum cone-shaped stator, two piezoelectric rings, and six alumina oxide contacts. Sphere shaped rotor is placed on the top of the robot and is moved in the plane or rotated about three axes. The special design of a cone-shaped stator allows obtaining precise planar or angular motion of the rotor independently when the top or bottom piezoelectric ring is excited using a saw-tooth waveform electric signal. Electrodes of both piezoelectric rings are divided into three equal sections and the corresponding section is excited to obtain a particular degree of motion. The planar motion of the robot and payload is obtained when the first in-plane vibration mode of the bottom piezoelectric ring is excited while the third radial mode of the top piezoelectric ring is employed to obtain rotation of the payload. Results of numerical investigations have shown that angular and planar motion of the load can be generated using the aforementioned vibration modes and excitation signals. Moreover, frequency response analysis showed that vibrations of the active piezoelectric ring make a minor influence on the motion of the passive ring while the coupling ratio of vibration amplitudes is in the range of 44.08–136.13 times. A prototype of the robot was made and an experimental investigation was performed. Results of dynamic characteristics measurements have shown that the robot can provide a maximum rotation speed of 21.1 RPM and a planar speed of 30.12 mm/s.