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This paper discusses the development and prototype construction of a powered hand exoskeleton that is designed to fit over the gloved hand of an astronaut. The exoskeleton is designed to offset the stiffness of the pressurized space suit and keep the productive time spent in the space suit from being constrained by hand fatigue. The exoskeleton has a three-finger design. The motions of the hand are monitored by an array of pressure sensors mounted between the exoskeleton and the hand, and the resultant controller commands are determined by a state of the art programmable controller. These commands are then applied to a DC motor array which power the device.

A new method of analyzing the kinematics of joint motion is developed in this study. Magnetic Resonance Imaging (MRI) offers several distinct advantages. Past methods of studying anatomic joint motion have usually centered on four approaches. These methods are x-ray projection, goniometric linkage analysis, sonic digitization, and landmark measurement of photogrammetry. Of these four, only x-ray is applicable for in vivo studies. The remaining three methods utilize other types of projections of inter-joint measurements, which can cause various types of error. MRI offers accuracy in measurement due to its tomographic nature (as opposed to projection) without the problems associated with x-ray dosage. Once the data acquisition of MR images was complete, the images for this study were processed using a 3-D volume rendering workstation. In this study, the metacarpalphalangeal (MCP) joint of the left index finger was selected and reconstructed into a three-dimensional graphic display.

Structural modelling of the EVA glove indicates that flexibility in the metacarpophalangeal (MCP) joint can be improved by selectively lowering the elasticity of the glove fabric. Two strategies are used to accomplish this. One method uses coil springs on the back of the glove to carry the tension in the glove skin due to pressurization. These springs carry the loads normally borne by the glove fabric, but are more easily deformed. An active system was also designed for the same purpose and uses gas filled bladders attached to the back of the EVA glove that change the dimensions of the back of the glove and allow the glove to bend at the MCP joint, thus providing greater flexibility at this joint. A threshold control scheme was devised to control the action of the joint actuators. Input to the controller was provided by thin resistive pressure sensors placed between the hand and the pressurized glove.

The most recent generation of space suit EVA gloves has addressed the problem of loose fit and stiffness in the fingers, but it remains difficult to build a glove assembly with low metacarpophalangeal joint stiffness. Fatigue due to constantly displacing the glove from a neutral position has been reported as the limiting factor in some EVA activities. This paper outlines an actuation system that uses gas filled bladders attached to the back of the EVA glove to provide the necessary force to bend the glove at the metacarpal joint, thus providing greater endurance during finger grasping tasks. A simple on-off controller senses hand movement through small pressure sensors between the finger and the glove restraint. The controller then fills or exhausts the bladders on the back of the glove to effectively move the neutral position of the glove as the hand inside moves.

Wheel runout can be reduced by better wheel design, coupled with improved manufacturing processes. For example, it appears that runout is less if the spokes are eliminated, providing a continuous flange, thus permitting a reduction in press fit. The resulting disc is easier to form, tooling and maintenance of dies have been simplified, and when the disc is assembled to the rim, it should be more uniform, with less concentrated distortion. A new machine, to be used on a semiproduction basis, is proposed for measuring wheel runout more accurately.