Intrinsic Contact Sensing and Object Perception of an Adaptive Fin-Ray Gripper Integrating Compact Deflection Sensors

Owing to their tremendous adaptability to free-form objects, soft grippers with fin-ray structure have a wide range of applications. However, kinetostatics analysis and contact sensing for such soft grippers are quite a challenge due to large structural deformations. In this article, a model-based method for intrinsic contact sensing, object perception, and interactive manipulation, is proposed for this kind of adaptive grippers. The contributions arise from the integration of compact strain-gauge sensors, that are particularly fabricated for slender flexible beams undergoing large deformations. Using a discretization-based approach, the contact condition can be identified efficiently in light of the local deformations gathered via the deflection sensors. Prototypes are developed using simple materials and manufacturing methods, on which various validation experiments are conducted. Owing to the contact sensing capability, the developed adaptive fin-ray gripper is able to perceive the boundary geometry and structural compliance of unstructured objects. Moreover, sensor-based feed-back control can be accomplished to perform interactive manipulation, in which the contact force between the finger and object can be regulated precisely (around $5\,\%$ RMS error) in real-time.