A Single-Servo Gear-Coupled HSA Gripper: Finite Element Evaluation of Material Hardness and Thickness on Grip Performance

Flexible grippers based on handed shearing auxetics (HSA) have demonstrated potential advantages over pneumatic solutions with respect to lightweighting and energy savings. However, there is a paucity of systematic research on how material hardness and geometric thickness affect the grasping force and contact pressure distribution. To address this issue, this paper proposes a single-servo gear-coupling mechanism that can simultaneously drive four HSA cylinders to achieve a flexible bending grasp of delicate crops. The finite-element analysis (FEA) method was employed to systematically investigate the impact of material parameters, including wall thickness and material hardness, on grasping force and pressure distribution. The study shows that harder and thicker HSA cylinders enhance grip force but create localized high pressure, whereas softer or thinner designs lower peak pressure and improve uniformity at the cost of force. These results highlight that an appropriate balance between hardness and thickness is essential for different grasping tasks and can serve as a practical reference for future HSA-gripper design.