An Agile 3 cm-Scale Quadruped Piezoelectric Robot with a Rigid Ring-Shaped Structure

Miniature piezoelectric robots can perform various tasks in narrow spaces, due to their small sizes and agile motions. However, there is key challenge of reconciling large load capacity with agile motions, which limits the integration of functional units. In this work, a miniature agile quadruped piezoelectric robot (AQPR) inspired by hard-shell animals is proposed. The prominent feature of AQPR is the rigid ring structure, which can be utilized to achieve large load capacity with its high stiffness; the degeneracy of different vibration modes is used to generate multi-dimensional trajectories at the foot, which can achieve linear and rotational motions. A prototype with size of 30 × 30 × 14.3 mm³ and weight of 6.9 g is produced. The experimental results show that the maximum linear and rotational speed is 255 mm s⁻¹ and 1265°s⁻¹, respectively. The load capacities reach 200 g (≈30 times self-weight). By using an impulse signal, the resolutions of linear and rotational motions reach 0.25 µm and 32.7 µrad, respectively. Benefiting from small size, large load capacity, high resolution, agile, and fast speed, AQPR shows great potential for applying micro-operations in narrow spaces, such as large-scale wafer transport and detection.