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This paper considers basket grasps, where a two-finger robot hand forms a basket that can safely lift and carry rigid objects in a 2-D gravitational environment. The two-finger basket grasps form special points in a high-dimensional configuration space of the object and two-finger robot hand. This paper establishes that all two-finger basket grasps can be found in a low-dimensional contact space that parametrizes the two-finger contacts along the supported object boundary. Using contact space, each basket grasp is associated with its depth that provides a security measure while carrying the object, as well as its safety margin away from a critical finger opening where the object drops-off into its intended destination. Geometric techniques that compute the depth and drop-off finger opening are described and illustrated with detailed graphical and numerical examples., QC 20210315

During exposure to microgravity in parabolic flights, it has been shown that the control of interaction forces when manipulating an object adapts partially to the lack of gravity, yet evidence indicates that anticipation of gravity's effects persists in the short term. The motivation for these experiments to be performed in long-duration space flight is to understand how the central nervous system adapts to an environment without gravity and what will be the consequences of long-term adaptation when an individual returns to a normal (Earth) or partial (Moon or Mars) gravitational field. The experiment "Dexterous Manipulation in Microgravity" (DEX) will target specific questions about the effects of gravity on dexterous manipulation. Some questions have already been studied over the last ten years in experiments conducted in parabolic flights, during which the way how the nervous system copes with repeated transitions between different gravitational environments has been investigated. Results from these experiments provide initial data about short-term adaptation to 0g. The experiments proposed for ISS draws from these short-term precursor experiments, but will emphasize long-term adaptation of sensorimotor processes to 0g and re-adaptation to 1 g. A first conceptual definition phase of a DEX instrument has been completed under an ESA contract. The DEX instrument is now in the design and development phase in view of a launch on ISS in the 2013- 2014 timeframe. The science background is recalled and several experiments performed during parabolic flights are presented, showing how these early breadboards testing in microgravity have helped to refine the DEX conceptual design and how it could be used on ISS. ©(2012) by the International Astronautieal Federation.

The purpose of this study was to determine the effect of altered gravity on human jump performance and intermuscular control. A musculoskeletal model was used to determine jump height, muscle power and energy delivered to the skeletal system (jump performance), and changes in muscle neuroexcitation and activation patterns (intermuscular control) for different values of gravity. The different values of gravity ranged from 0.2 to 1.8 times earth gravity. Prior to analyzing the musculoskeletal model solutions, the model solutions were validated by comparing predicted jump heights, time-required-to-jump, ground reaction force, joint kinematics and muscle neuroexcitations to measured experimental data collected in increased gravitational environments. JMD