air and ground vehicles at this scale should consider power needs, and very little about this important consideration was presented.
ARL Millimeter-Scale Aerial Platforms This project’s objective is to provide the Army with a low-cost, low-observable, mobile sensor platform using PZT and MEMS technology. The study is focused on a feasibility analysis of millimeter-scale robotics. Key challenges in this work include developing and integrating appropriate power sources at this length scale, providing adequate load-bearing capacity for flight vehicles designed using MEMS production techniques, and appropriate framing of the mobility design problem. The focus resides in studying flapping-wing propulsive devices to look at aerial vehicles ranging in mass from tens to hundreds of mg. There is significant dependence on the promise of thin-film battery technology for delivering the power needs for this project.
The approach completely embraces the idea of build-and-fly test concepts, with a focus on MEMS production techniques. Very simplistic aerodynamic theories are used to predict the flight characteristics of these devices, and further improvement is promised as other portions of MAST provide the necessary tools for more refined analysis. To date, the work has resulted in millimeter-scale flapping-wing designs that have been demonstrated on static test rigs. At this length scale, this work represents the state of the art and is one of the most promising developments at ARL in this area. A significant amount of formal design work (including coupled multidisciplinary analysis and optimization, albeit with simplified analysis modules) has been performed in support of this project. Understandably, the work has been well received in the literature, as evidenced by both conference and archive journal papers. The lack of more robust aerodynamic calculations should not hold back this development. The requirements of mechanical power, however, could be a major impediment to success. Parallel developments at appropriate power electronics to get the voltages required for appropriate deformations in pitch and flap should be a continuing focus in this regard.
Overall Technical Quality
ARL is to be complimented for the range of robotics sizes and the different types of mobility devices in its robot research portfolio. Also, the research portfolio is well balanced in terms of analysis and physics-based modeling and experiments. It addresses real-world effects and has great focus on meeting a specific need. Metrics are fairly well defined, and the inherent requirement of a test vehicle drives the system thinking and approach. The work on the “micro flyers” and legged robotic systems are best-in-class. There was a good portfolio of vehicles and platforms from small scale to meso- and microscale. Specific efforts were judged to be leading the state of the art in their areas. Briefers are aware of and addressed the system perspective. A candidate area for increased emphasis is discrete awareness of mission, sensors, and power requirements to meet the application vision and scenario. The efficiency of existing robotic systems in transferring energy from the engine to the environment is still several orders of magnitude worse than biological devices, and therefore continued work in this area is required. Because of the burden imposed on soldiers by battery packs and robots’ limited time on mission, research that improves the overall energy density and the efficiency of converting energy to motion is required. In particular, research on the combustion of small JP-8 combustion engines and research on the efficient creation and transfer of force to the environment should be added to the research portfolio.