Chris E. Perry

A sensor platform capable of aerial and terrestrial locomotion

A sensor platform has been developed that is capable of both aerial and terrestrial locomotion, as well as transitioning between the two. The morphing micro air-land vehicle (MMALV) implements biological inspiration in both flying and walking. MMALV integrates the University of Floridas micro air vehicle (MAV) technology with the terrain mobility of Mini-Whegs/spl trade/. Fabricated of lightweight carbon fiber, the UF-MAV employs a flexible wing design to achieve improved stability over other MAVs of similar size. Mini-Whegs/spl trade/ employs the patented (pending) wheel leg running gear that makes the Whegs/spl trade/ and Mini-Whegs/spl trade/ line of robots fast, agile, and efficient. MMALV has a 30.5cm wingspan, and is 25.4cm long. Terrestrial locomotion is achieved using two independently controlled wheel legs, which are differentially actuated to perform turning. The vehicle successfully performs the transition from flight to walking. Furthermore, MMALV is capable of transitioning from terrestrial to aerial locomotion by walking off a structure of only 20 feet. A wing retraction mechanism improves the portability of the vehicle, as well as its terrestrial stealth and ability to enter small openings.

New Sensors to Track Head Acceleration during Possible Injurious Events

Abstract : Instrumented earplugs were first introduced in 2000 by the Air Force Research Lab (AFRL) as a means of measuring head accelerations in race car drivers after it was shown that instrumented helmets slipped on the head during impact events. A version of these earplugs was adopted by the Indy Racing League and Championship Auto Race Teams (CART) in 2003. In 2006, Begeman, Melvin, Troxel and Mellor reported that signals from earplugs mounted in cadavers showed a phase shift at 50 and 100 Hz vibration indicating less than perfect coupling with the head. This led to the development of a new miniature tri-axial accelerometer that is small enough to be placed in the ear canal portion of communication earplugs (earpieces) thereby improving the coupling and thus the reliability of the recordings from drivers undergoing multi-axial crash events.

Examining the relationship between whiplash kinematics and a direct neurologic injury mechanism

Despite the prevalence of whiplash-related injuries, a connection between clinical symptoms and injury mechanism has been elusive. Previous studies have attempted to correlate the whiplash kinematic response to injury mechanisms; however, none has specifically examined the potential for neurologic involvement due to foraminal occlusion. This biomechanical study measured cadaver cervical spine whiplash kinematics and compared these with changes in the neural space geometry of the cervical spine, providing a measure of the direct neurologic injury potential. Extension and shear displacements of each cervical level were measured and found to be similar to that reported in the literature and within the tissues physiologic limits. Further, changes to the spinal canal and intervertebral foraminal geometry were recorded during whiplash and cross-sectional area changes were documented (up to 15.3%). Because these foraminal occlusions were smaller in magnitude than those resulting from normal cervical motion, our findings do not support direct neurologic injury resulting from segmental vertebral kinematics as a whiplash injury mechanism.

Dynamic tensile failure mechanics of the musculoskeletal neck using a cadaver model.

Although the catapult phase of pilot ejections has been well characterized in terms of human response to compressive forces, the effect of the forces on the human body during the ensuing ejection phases (including windblast and parachute opening shock) has not been thoroughly investigated. Both windblast and parachute opening shock have been shown to induce dynamic tensile forces in the human cervical spine. However, the human tolerance to such loading is not well known. Therefore, the main objective of this research project was to measure human tensile neck failure mechanics to provide data for computational modeling, anthropometric test device development, and improved tensile injury criteria. Twelve human cadaver specimens, including four females and eight males with a mean age of 50.1+/-9 years, were subjected to dynamic tensile loading through the musculoskeletal neck until failure occurred. Failure load, failure strain, and tensile stiffness were measured and correlated with injury type and location. The mean failure load for the 12 specimens was 3100+/-645 N, mean failure strain was 16.7+/-5.4%, and mean tensile stiffness was 172+/-54.5 N/mm. The majority of injuries (8) occurred in the upper cervical spine (Oc-C3), and none took place in the midcervical region (C3-C5). The results of this study assist in filling the existing void in dynamic tensile injury data and will aid in developing improved neck injury prevention strategies.

Development of an updated tensile neck injury criterion

BACKGROUND Ejection neck safety remains a concern in military aviation with the growing use of helmet mounted displays (HMDs) worn for entire mission durations. The original USAF tensile neck injury criterion proposed by Carter et al. (4) is updated and an injury protection limit for tensile loading is presented to evaluate escape system and HMD safety. METHODS An existent tensile neck injury criterion was updated through the addition of newer post mortem human subject (PMHS) tensile loading and injury data and the application of Survival Analysis to account for censoring in this data. The updated risk function was constructed with a combined human subject (N = 208) and PMHS (N = 22) data set. RESULTS An updated AIS 3+ tensile neck injury criterion is proposed based upon human and PMHS data. This limit is significantly more conservative than the criterion proposed by Carter in 2000, yielding a 5% risk of AIS 3+ injury at a force of 1136 N as compared to a corresponding force of 1559 N. DISCUSSION The inclusion of recent PMHS data into the original tensile neck injury criterion results in an injury protection limit that is significantly more conservative, as recent PMHS data is substantially less censored than the PMHS data included in the earlier criterion. The updated tensile risk function developed in this work is consistent with the tensile risk function published by the Federal Aviation Administration used as the basis for their neck injury criterion for side facing aircraft seats.

Evaluation of the Nij neck injury criteria with human response data for use in future research on helmet mounted display mass properties

Technological advances have enabled components to be added to Helmet Mounted Displays (HMDs) that provide increased pilot capability. Future Air Force fighter aircraft are being developed to incorporate added technologies that could result in heavier and bulkier HMDs. The added weight and center of gravity changes to the pilot’s helmet ensemble from these additional components place the neck at an increased risk of injury during ejection. This paper outlines a preliminary research methodology studying the human neck response data from the Air Force Research Laboratory’s extensive human impact testing database using the Nij criteria as an evaluative tool. Initial results are presented.