Joint Angle and Muscle Signature (JAMS)
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.