The Joint Angle and Muscle Signature (JAMS) System developed at the
University of Maryland Space Systems Laboratory is designed to provide
accurate, quantitative information describing joint motion of the hand and
muscle activity of the associated extensor and flexor groups in the forearm
during extravehicular activities (EVA). The system was built to aid in
understanding the biomechanics of the EVA-gloved hand/forearm, from both
a kinematic and neuromuscular standpoint.
The JAMS system noninvasively monitors joint motion of the right hand and
muscle activity of the large hand flexors and extensors, and is compact and
lightweight enough to be used within an extravehicular mobility unit (EMU).
The JAMS system, shown in Figure 1, is completely self-contained, requiring
no external power or data lines. Noninvasive surface electrodes are placed
on the large extensor and flexor muscle groups of the hand, located in the
forearm, to monitor muscle electrical activity. Fiberoptic cables which
transmit light in inverse proportion to fiber deflection are used to track
composite joint angles in each of the five digits. Data conditioning,
acquisition, and storage units are mounted on a vest which is worn within
the hard upper torso (HUT) of the EMU. The system is capable of collecting
data for approximately one hour total; currently the limiting factor is the
size of the flash RAM data storage card. Data acquisition is controlled via
a reed switch located inside the soft lower torso assembly (LTA) where an
externally-placed magnet can be used to activate the system after suit ingress.
System status, including data acquisition activity, processor, power, and
sensor status, is displayed to the suited subject via an LED panel mounted
on the communications carrier cap. For more information about the JAMS System,
see AIAA paper #96-4222, Joint Angle and Muscle Fatigue Detection in the Hand
During EVA Simulation Operations, presented at the Space Programs and
Technologies Conference in September 1996.
The JAMS System was used to collect data describing hand motion and muscle
activity during simulated EVA operations in the Neutral Buoyancy Simulator
(NBS) at MSFC in August-September, 1996 (Fig 2) Taskboard-based activities
incorporating simple tasks (gripping tools and turning knobs) and complex
activities (j-hook operation and beam assembly) were completed by all
subjects. JAMS data was acquired during the first and last 20-25 minute
taskboard cycles of each ~3 hour test session. Six right-handed male
volunteers, ages 20-40, participated in the study. Of these, three test
subjects had experience in EVA suits while the remainder were novices.
Results of the JAMS system tests are currently being studied and should
be available by mid-1997.