Three-jaw gripper driven by rhombic dielectric elastomer actuators

Abstract

This paper proposes a three-jaw gripper driven by rhombic dielectric elastomer (DE) actuators to address the inadequate adaptability and potential workpiece damage of conventional rigid grippers, as well as the complex drive mechanisms, limited clamping force, and insufficient adaptability of existing flexible grippers. The gripper integrates three rhombic DE actuators with a symmetrical three-jaw configuration and a rhombic telescopic transmission mechanism, converting the in-plane expansion of the DE into synchronous radial jaw displacement. An electro-induced deformation-mechanical equilibrium model was established to describe the force-transmission and voltage-regulation mechanisms. The device was fabricated using a biaxially prestretched three-layer VHB4905 membrane and had overall dimensions of 116 × 116 × 108 mm. Experiments showed that the actuator achieved a maximum displacement of 16 mm at 6.5 kV, requiring approximately 11 s for full actuation and 16 s for recovery after voltage removal. It sustained axial loads of 0–0.5 N. The gripper adaptively grasped screws, nuts, gaskets, and steel balls measuring 6–25 mm and weighing 0–55 g, and completed automated grasping, transfer, and release. In 100 repeated cycles, the gripper achieved a 94% success rate without electrical or structural failure of the dielectric films. Under identical testing conditions using the same cylindrical workpiece and a driving voltage of 6.5 kV, five repeated gripping tests yielded an average jaw closure displacement of 5.02 mm with a coefficient of variation (CV) of 4.07%, and an average axial pull-off force of 3.04 N with a CV of 1.33%. These results demonstrate the proposed gripper’s good jaw closure repeatability and consistent gripping capability, providing a promising structural design and theoretical basis for the miniaturization and practical implementation of dielectric-elastomer-driven flexible grippers.