Kinematic Rules for Upper and Lower Arm Contributions to Grasp Orientation

Abstract

The purpose of the current study was to investigate the contribution of upper and lower arm torsion to grasp orientation during a reaching and grasping movement. In particular, we examined how the visuomotor system deals with the conflicting demands of coordinating upper and lower arm torsion and maintaining Donders' Law of the upper arm (a behavioral restriction of the axes of arm rotation to a two-dimensional “surface”). In experiment 1, subjects reached out and grasped a target block that was presented in one of 19 orientations (5° clockwise increments from horizontal to vertical) at one position in a vertical presentation board. In experiment 2, target blocks were presented in one of three orientations (horizontal, three-quarter, and vertical) at nine different positions in the presentation board. If reach and grasp commands control the proximal and distal arms separately, then one would only expect the lower arm to contribute to grasp orientations and that Donders' Law would hold for the upper arm—independent of grasp orientations. Instead, as the required grasp orientation increased from horizontal to vertical, there was a significant clockwise torsional rotation in the upper arm, which accounted for 9% of the final vertical grasp orientation, and the lower arm, which accounted for 42%. A linear relationship existed between the torsional rotations of the upper and lower arm, which indicates that the components of the arm rotate in coordination with one another. The location-dependent aspects of upper and lower arm torsion remained invariant, however, yielding consistently shaped Donders' “surfaces” (with different torsional offsets) for different grasp orientations. These observations suggest that the entire arm-hand system contributes to grasp orientation, and therefore, the reach/grasp distinction is not directly reflected in proximal-distal kinematics but is better reflected in the distinction between these coordinated orienting rules and the location-dependent kinematic rules for the upper arm that result in Donders' Law for one given grasp orientation.

The continuous end-state comfort effect: weighted integration of multiple biases

“…Most importantly, the data show that the forearm orientation is a reliable operationalization of the grasp orientation. The contribution of the forearm rotation to the overall rotation in Experiment 1 exceeded previous accounts, which showed that wrist and fingers as well as the forearm contributed roughly equally when grasping or manipulating objects (Herbort and Butz 2010;Marotta et al 2003). Most likely, the higher forearm contribution results from the task, which requires-unlike in the previous experimentsthat the fingers support the grasped object.…”

“…Even though fixating the accelerometer to the forearm did not enable measuring the hand's orientation directly, we used this method because in this way, no sensors at the fingers hindered the participants' interactions with the dial. Moreover, previous studies have shown that the orientation of the forearm is highly correlated with the orientation of the hand and thus a suitable operationalization (Herbort and Butz 2010;Marotta et al 2003).…”

A novel robotic system for quantifying arm kinematics and kinetics: Description and evaluation in therapist-assisted passive arm movements post-stroke

“…These data complement a number of extant studies that have made important contributions to neuroscience by documenting the spatiotemporal patterns of hand movement in various workspace configurations. For example, studies have explored how the shoulder and elbow angles are coordinated in pointing and reach-to-grasp tasks (Soechting and Lacquaniti, 1981;Lacquaniti and Soechting, 1982;Marotta et al, 2003) and tasks requiring pronation and supination of the forearm towards and away from the body (Alazmani et al, 2009). In contrast, there have been only a few studies that have contributed towards our understanding of the motive forces and torques required to affect movement of the upper limb joints.…”

Analysis of task feasibility for a home robot using prismatic joints

“…Many studies have shown that humans tend to think about grabbing objects in a hand-centric coordinate system, which implies that reaching motion also optimizes the distance the hand travels through the environment. Considering this observation along with motion capture experiments on people performing reaching tasks [17], we see that the hand roughly follows a linear trajectory to the target object roughly optimizing distance traveled in the workspace. Instead of designing a robot arm with an anthropomorphic structure as the first priority, we motivate the importance of translational motion in pick-and place tasks and design a robot arm that prioritizes translation (Fig.…”

“…For example, object fetching task from floor in house is combination of retrieving motion in x-axial direction and lifting up motion in z-axial direction to a desired height. Based on the observation that a human arm roughly follows a linear trajectory [17], we design a prismatic mechanism in the the forearm and upper arm of the robot.…”