Fig. 6: Cooperation of the tactile palm and soft fingers.

a Demonstration of TacPalm SoftHand picking up a card on a desk. A finger pulls the card away from the desk using a single-finger gait strategy circularly until the card edge touches the palm, followed by the palm withstanding the card and providing subtle tactile feedback of line-shaped indentation to control all fingers for grasping. b Illustration of the single-finger gait with five time points (T0, T1, T2, T3, T4). The fingertip has a free trajectory in its workspace and a constraint trajectory when interacting conformably with the card on the desk. c Actuation and control system of the finger-palm cooperation strategy for picking up the card. d Variations of actuation pressures and tactile sensing states during the picking up task. Actuation pressures are described by P = [p₁₁, p₂₁, p₁₂, p₂₂, p₁₃, p₂₃]. The first subscript denotes whether the finger segment is proximal or distal. The second subscript denotes the finger number. e TacPalm SoftHand continuously detects subtle flaws on a variegated fabric using cyclic finger gaits. f Distinct indentation differences between the flaw and flawless cases in representative tactile images. CDM (color difference metric) is a dimensionless parameter calculated by summing the color variations between the highest and lowest RGB values in the tactile image. The value of CDM ≥ 40 indicates a flaw, while CDM < 40 indicates a flawless surface (showing only fingertip indentation). Flaws typically create discontinuous geometries that generate image regions with a wider range of color variation. Flawless regions produce more uniform tactile images showing only the finger indentation. g TacPalm SoftHand adjusts the grasping pose during teapot pouring. The tactile palm continuously monitors the subtle changes of the geometric feature on the teapot’s bottom and informs the finger to adjust the teapot’s pose to avoid it falling. h Demonstration of the tracked geometries on the teapot’s bottom and the corresponding contour area in the tactile image. i Actuation and control system of the finger-palm cooperation strategy for the teapot pouring task. j Variations of actuation pressures and tactile sensing states during the teapot pouring task.