The Defense Advanced Research Projects Agency (DARPA) inaugurated a program addressing research and development for an Exoskeleton for Human Performance Augmen-tation in FY 2001. A team consisting of Oak Ridge National Laboratory, the prime contractor, AeroViron-ment, Inc., the Army Research Laboratory, the University of Minnesota, and the Virginia Polytechnic Insti-tute has recently completed an 18-month Phase I effort in support of this DARPA program. The Phase I effort focused on the development and proof-of-concept demonstrations for key enabling technologies, lay-ing the foundation for subsequently building and demonstrating a prototype exoskeleton. The overall ap-proach was driven by the need to optimize energy efficiency while providing a system that augmented the operator in as transparent manner as possible (non-impeding). These needs led to the evolution of two key distinguishing features of this team’s approach. The first is the “no knee contact” concept. This concept is dependent on a unique Cartesian-based control scheme that uses force sensing at the foot and backpack attachments to allow the exoskeleton to closely follow the operator while avoiding the difficulty of connecting and sensing position at the knee. The second is an emphasis on energy efficiency manifested by an energetic, power, actuation and controls approach designed to enhance energy efficiency as well as a reconfigurable kinematic structure that provides a non-anthropomorphic configuration to support an energy saving long-range march/transport mode. The enabling technologies addressed in the first phase were controls and sensing, the soft tissue interface between the machine and the operator, the power system, and actuation. The controller approach was implemented and demonstrated on a test stand with an actual operator. Control stability, low operator fatigue, force amplification and the human interface were all successfully demonstrated, validating the controls approach. A unique, lightweight, low profile, multi-axis foot sensor (an integral element of the controls approach) was designed, fabricated, and its perfor-mance verified. A preliminary conceptual design of the human coupling and soft tissue interface, based on biomechanics research has been developed along with a test plan to support an iterative design process. The power system concept, a fuel cell hybrid power supply using chemical generated hydrogen, was succes-sfully demonstrated and shown to be able to efficiently meet both steady-state and transient peak loads. Two actuator approaches, a piezoelectric actuator, with theoretical high power densities and an approach based on a high-performance, high-speed electric motor driving a miniature hydraulic pump have been investigated. The first shows great potential but will require further research before reaching that promise. The other approach has been modeled and simulated and shown to provide the possibility for significant energy savings (>30%) and improved power densities in comparison to conventional hydraulics. Biomechanics analysis and testing were also performed in support of these enabling technologies, to pro-vide a basis for design criteria. An analysis was performed to determine baseline data for initial mecha-nical design and power supply sizing. Testing conducted to evaluate boot sole thickness found that thick-ness increases up to two inches could be accommodated without significant impact on human factors issues. This 18-month long Phase I effort has evaluated key enabling technologies and demonstrated advances in these technologies that have significantly increased the likelihood of building a functional prototype exoskeleton.

Категория: Научные статьи | Нет комментариев »

Комментарии