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Wearable Sensor System for Monitoring Soldier Body Dynamics


OBJECTIVE: Develop a portable, lightweight, ruggedized, and comfortable wearable system for monitoring body and equipment dynamics during naturalistic movement outside the laboratory environment. DESCRIPTION: As new equipment, body armor, and technologies are being developed for the dismounted Soldier, it is vital the effects of this equipment on Soldier movement can be evaluated in an operationally relevant environment. Kinematics and kinetics are two useful areas of science which can be applied towards evaluating the effects of clothing, weapon systems, and equipment on Soldier movement and performance. Current technology does not allow the collection of kinematic and kinetic data in an operationally relevant environment. There are two ways that are primarily used to collect or derive this data: 1) with a camera-based motion capture system and 2) inertial sensor systems. With a motion capture system, data collection is limited to a relatively small capture volume and markers must be attached to landmarks on the body, which can be blocked by equipment and body armor. When these markers are blocked, useful data cannot be collected. The commercially available inertial sensor systems are heavy and the sensors are too large for the systems to be worn comfortably under clothing. Additionally, these inertial systems are designed to track only body motion, not weapon or equipment movement, which is important for characterizing marksmanship performance. These problems inhibit our ability to collect kinetic and kinematic data to evaluate Soldier performance in an operationally relevant environment. The U.S. Army requires a system that can measure the 3-D position, velocity and acceleration of the Soldier"s head, trunk, limbs and equipment using small, lightweight sensors that don"t interfere with uniforms, body armor, or equipment. The system must be accurate to 0.5mm within a local coordinate system for the position of body segments and equipment. The system and software need to provide, derive, or integrate the following signals to sufficiently capture each Soldier"s movement: linear and angular acceleration, linear and angular velocity, position and orientation, joint torques and segment kinematic energy. In addition to the body kinematics, the system would be used to monitor the movement of the weapon and to track the weapon aim trace. At 25 m, the accuracy of the weapon aim point at the target should be 1.0 cm. This data should be transmitted wirelessly and viewable in real-time, as well as saved to a computer. The system should be weatherproof, rugged for data collection in any environment, and not impede Soldier movement. The system needs to attach firmly to the body, be resistant to breakage, loosening, and minimize motion artifact. Each sensor should be 2 cm x 2cm or smaller, and weigh less than 5 grams, including the rechargeable battery. The system should include a graphical user interface (GUI) for experimenter to use when collecting and processing data, as well as access to source code for data analysis. PHASE I: Develop hardware for body worn sensor array and approaches for analyzing 3-D segment and joint kinematics. A prototype system is expected at the end of phase I. PHASE II: Refine kinematic measurement processes and expand the capability of the sensor array to quantify body kinetics. Demonstrate ability to collect kinematic and kinetic against current gold standards (3-D motion capture and force plates). Demonstrate feasibility by conducting a pilot study where the U.S. Army or U.S. Marine Corps shooters perform walking, running, and shooting trials, indoors and outdoors at range facilities at Aberdeen Proving Grounds or an alternate military facility. Provide results, including body segment kinematics and kinetics, weapon kinematics and kinetics, and weapon aim point. Provide source code and GUI for data collection and processing. At the conclusion of phase II, the system should be ready to collect biomechanical measures of Soldiers in field studies. Additionally, work with ARL personnel to seek customers and transitions for the system. PHASE III: There is a wide variety of application for the end state of this research project. Future military uses include evaluation of weapon systems, Soldier equipment and body armor. Additionally, this system could be used for ergonomic evaluations of tasks and vehicles. Clinical applications for monitoring body dynamics include rehabilitation, prosthetics, sports medicine, and occupational health. REFERENCES: 1) Department of the Army. (2008). Rifle marksmanship m16-/m4-series weapons (FM 3-22.9). Retrieved from website: 2) Roetenberg, D., Luinge, H., & Sylcke, P. (2009). Xsens mvn: Full 6dof human motion tracking using miniature inertial sensors. XSENS Technologies, Retrieved from 3) Harned, N. (2011). Army S & T Strategic Direction: Areas for Industry Participation
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