The SDM Hand: A Highly Adaptive Compliant Grasper for Unstructured Environments

Abstract

The inherent uncertainty associated with unstructured grasping tasks makes establishing a successful grasp difficult. Traditional approaches to this problem involve hands that are complex, fragile, require elaborate sensor suites, and are difficult to control. Alternatively, by carefully designing the mechanical structure of the hand to appropriately incorporate features such as compliance and adaptability, the uncertainty inherent in unstructured grasping tasks can be more easily accommodated. These features can reduce the need for complicated sensing and control by passively adapting to the object properties and positioning, making the hand easier to operate and with greater reliability. In this paper, we demonstrate a novel adaptive and compliant grasper that is both simple and robust. The four-fingered hand is driven by a single actuator, yet can grasp objects spanning a wide range of size, shape, and mass. The hand is constructed using polymer-based Shape Deposition Manufacturing (SDM), with joints formed by elastomeric flexures and actuator and sensor components embedded in tough rigid polymers. The hand has superior robustness properties, able to withstand large impacts without damage and capable of grasping objects in the presence of large positioning errors.