Modeling time invariance in human arm motion coordination

2013

Exp Brain Res

This paper examines up to third-order geometric properties of wrist path and the first-order property of wrist trajectory (wrist speed) for spatial pointing movements. Previous studies report conflicting data regarding the time invariance of wrist-path shape, and most analyses are limited to the second-order geometric property (straightness, or strictly speaking, curvature). Subjects performed point-to-point reaching movements between targets whose locations ensured that the wrist paths spanned a range of lengths and lay in various portions of the arm's spatial workspace. Movement kinematics were recorded using electromagnetic sensors located on the subject's arm segments and thorax. Analysis revealed that wrist paths tend to lie in planes and to curve more as movement speed decreases. The orientation of the wrist-path plane depends on the reaching task but does not vary significantly with movement speed. The planarity of wrist paths indicates that the paths have close to zero torsion-a third-order geometric property. Wrist-speed profiles showed multiple peaks for sufficiently slow and long lasting movements, indicating deviation from the well-known, bell-shaped profile. These kinematic findings are discussed in light of various motor control theories.

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Section: Discussionmentioning

confidence: 99%

Section: Wrist-speed Profilesmentioning

confidence: 96%

Invariant geometric characteristics of spatial arm motion

2013

Exp Brain Res

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“…Equations (14), (15), and (16) can be solved to obtain the speed ratios up to the third order. In fact, the p th −order coordination equation is r (λλ...p times)0 ×T = 0.…”

Section: Tracking Straight Linesmentioning

confidence: 99%

“…The first-and second-order coordination equations for this case are the same as Eqn. (14) and Eqn. (15), respectively.…”

Section: Inflection Points On the Desired Pathmentioning

confidence: 99%

See 1 more Smart Citation

Geometric, Spatial Path Tracking Using Non-Redundant Manipulators via Speed-Ratio Control

Volume 2: 34th Annual Mechanisms and Robotics Conference, Parts a and B

Stanisˇic

2010

Path tracking can be accomplished by separating the control of the desired trajectory geometry and the control of the path variable. Existing methods accomplish tracking of up to third-order geometric properties of planar paths and up to second-order properties of spatial paths using non-redundant manipulators, but only in special cases. This paper presents a novel methodology that enables the geometric tracking of a desired planar or spatial path to any order with any non-redundant regional manipulator. The governing first-order coordination equation for a spatial path-tracking problem is developed, the repeated differentiation of which generates the coordination equation of the desired order. In contrast to previous work, the equations are developed in a fixed global frame rather than a configuration-dependent canonical frame, providing a significant practical advantage. The equations are shown to be linear, and therefore, computationally efficient. As an example, the results are applied to a spatial 3-revolute mechanism that tracks a spatial path. Spatial, rigid-body guidance is achieved by applying the technique to three points on the end-effector of a six degree-of-freedom robot. A spatial 6-revolute robot is used as an illustration.

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Time-Invariant Strategies in Coordination of Human Reaching

Advances in Robot Kinematics: Analysis and Design

2008