Enhancing gripping stability for delicate object handling: frictional insights into textured soft pads

Abstract Soft pads are increasingly utilized in robotic grippers for applications requiring secure handling, such as fruit harvesting and delicate object manipulation. However, the interplay of material compliance, surface texture, and environmental conditions (e.g., moisture, wind) complicates selecting the optimal frictional performance. This paper investigates four soft pad textures—flat, cavity, protrusion, and hybrid—fabricated from two silicone rubbers with different Shore hardness (10A and 30A). Their frictional behavior was tested under varying loads (0–200 g), speeds (14–84 mm/s), and wet/dry conditions. A Friction Stability Index (FSI) was then introduced to capture both friction magnitude and slip oscillations. Results show that while flat pads provide the highest mean friction, they exhibit pronounced stick–slip, specially at higher speeds. Textured pads (cavity, protrusion, hybrid) yield more stable friction, particularly in wet, outdoor-like scenarios, albeit with somewhat lower peak friction. The findings underscore the importance of balancing high friction against stability for safe handling.