Development of a Small Two-Dimensional Robotic Spherical Joint Using a Bonded-Type Piezoelectric Actuator

Piezoelectric actuator (PEA) is one of the most promising candidates for the robotic joints to realize high-resolution linear or rotary motions. In this article, a small 2-D robotic spherical joint using a bonded-type PEA was proposed to achieve the high-resolution rotary motions around two orthogonal axes. The configuration and operating principle of the robotic spherical joint were first formulated. Then theoretical analyses were carried out to design the PEA, and a prototype of the joint was fabricated. Finally, a series of tests were performed to verify the theoretical results and investigate the mechanical output performances of the joint. The experimental results revealed that maximum rotary velocities of 1.03 rad/s around the X-axis and 1.14 rad/s around the Y-axis were achieved under voltage of 400 Vp-p and frequency of 750 Hz. Meanwhile, the displacement resolutions were tested to be about 4.64 μrad around the X-axis and 4.76 μrad around the Y-axis. The proposed joint with small size and compact structure could accomplish the 2-D precision rotary motion with merits of high resolution and large motion range.