Grasp Taxonomy (Power Grasp vs. Precision Grasp / Pinch)

A classification of hand grasps by how the hand contacts an object, split at the top level into power grasps and precision grasps.

Grasp taxonomy organizes the ways a human or robotic hand can grip something into a system of categories. In 1956, John Napier split human grasping into two broad types: a power grasp wraps the object with the palm and all four fingers, favoring stability and force, while a precision grasp mainly opposes the thumb pad against the pads of the other fingers, favoring fine position control. Pinching falls under precision grasping, holding a small object with just the fingertips or the sides of the fingers. In 1989, Mark Cutkosky observed manufacturing workers using tools and proposed a grasp taxonomy tree aimed at robotic hand design; Feix and colleagues later surveyed over a dozen sources and compiled 33 grasp types, further broken down by the opposition type (palm, fingertip, or finger side) and thumb posture, publishing this as the GRASP taxonomy in 2016. It's commonly used to decide which degrees of freedom a dexterous hand needs to keep, and as a category label in grasping datasets.

ExampleGripping a hammer handle to drive a nail is a power grasp; pinching a screw between thumb and index fingertip is a precision grasp. Evaluating a new dexterous hand often means checking, one by one, whether it can reproduce these standard grasp types.

Also called

Power Grasp, Precision Grasp, Pinch Grasp, Cutkosky Grasp Taxonomy, GRASP Taxonomy

Related

Grasping · Dexterous Hand · Dexterous Manipulation · Hand Synergies · Thumb Opposition · Grasp Planning

Sources

A comprehensive grasp taxonomy (Feix et al., RSS 2009 Workshop)
The GRASP Taxonomy of Human Grasp Types (Feix et al., IEEE THMS 2016)
On grasp choice, grasp models, and the design of hands for manufacturing tasks (Cutkosky, 1989)