preshape

Preshape is the initial configuration of an object, device, or limb after planning but before executing an action. In common use, it refers to the hand or gripper shaping itself in anticipation of grasping an object.

In robotics and biomechanics, preshape describes the pre-contact posture of a robotic hand during a reach, aimed at matching the target object's size, orientation, and cross-section. The preshape is generated from visual or sensor data and is integrated with reach trajectory planning. Successful preshape reduces approach errors and increases chances of a secure grasp.

In human motor control, people naturally preshape their hand during reaching. The finger aperture tends to scale with object size and orientation. Preshaping occurs early in the movement and interacts with grip type and task constraints. Neuromuscular noise and object uncertainty can modulate the accuracy of preshape.

In prosthetics and rehabilitation, preshape concepts guide the design of powered or myoelectric hands. Systems may set a pre-grasp configuration or trigger a rapid pre-shape based on intention signals, improving speed and grip success.

Beyond grasping, preshape can refer to any preliminary shape used as a starting point in manufacturing or design, such as a preform or contour that guides final shaping or molding.