The primary focus at April's annual AeroSense meeting here was the ongoing War on Terrorism. Sponsored by the optical engineering society SPIE (Society of Photo-optical Instrumentation Engineers), the gathering brings together those involved in aerospace and defense sensors, simulation, and controlsówith applications including robotics, and imaging and vision systems.
In the latest robotic developments, Scott Pratt of iRobot (Somerville, MA) gave insight as to what features future urban search and rescue (USAR) robots will need to be successful. The company's and others' robots were rushed to Ground Zero after the September 11th attacks to locate survivors and victims, and provided some hard lessons for their developers.
Pratt said the USAR environment is more taxing than military applications. Here robots operate in more extreme conditions and need wider mobility to function in close quarters, such as collapsed buildings. At the World Trade Center, he noted some tracked robots experienced debris ingestion, limiting their movement. Many robots were simply too big for the extremely small spaces left in the debris pile, so these were used for building inspection of nearby structures. Quite often robots would flip over, and thus needed to adapt by self-righting or being able to function in both orientations, which robots with wrap-around treads can do (see figure).
Communications with the robots were a challenge, Pratt added. Tethers allowed reliable control and full-frame rate video. But they required extra support equipment and created snag points. Wireless links, on the other hand, were subject to interference in an environment that was awash with RF radiation. And the debris itself attenuated signals. Pratt noted as a result future robots could use a combination of both types of communications, radio relays, and greater autonomy. Also, a tether deployed from the robot is less likely to snag than one that is dragged.
Video imaging was common on the Trade Center robots. Operation in two to three inches of dust highlighted the need sometimes for the operators to elevate the camera's point of view, Pratt said, making robots such as Inuktun Services (Nanaimo, BC, Canada) Micro VGTV useful. But he noted the operators always wanted to look or go a little further than they were able. Other lessons are the usefulness of color imaging to better discern the environment as well as thermal infrared systems to locate survivors via body heat.
Modular robots, such as a single platform with bolt-on systems, created the most flexibility with the least volume of equipment. Waterproof systems are useful in flooded areas and allow vehicle decontamination.
Finally, Pratt added, ease of deployment is vital in being able to get to a disaster site quickly and set up in minimal time. Unfortunately, no survivors were found by the robots, but they were able to find victims missed using traditional search methods.
Flies on the wall. There were also reports on small flying robots, better known as MAVs (Micro Air Vehicles; see DN 5.18.1998, p. 82) These have evolved to what Sam Wilson, head of the MAV development program at DARPA (Defense Advance Research Project Agency), calls "flying RUGS," or Relocatable Unattended Ground Sensors.
Originally these hand-sized systems were to be carried by a soldier and launched to scout the local area, including urban and interior spaces. MAVs were originally seen as fixed-wing aircraft. But such a configuration, without any complex wing flaps, had top and slowest speeds (in tens of mph) very close together. This narrow envelope, he pointed out, doesn't work well for maneuvering within confined spaces. Also, a fixed wing has to keep flying to function, limiting its endurance.
DARPA planners now envision more of a helicopter using a ducted fan (a propeller mounted inside a cylindrical wing). "It could theoretically go up to 80 knots or hover," Wilson noted. As a video clip demonstrated, the shrouded prop allows an operator to safely snatch the vehicle out of the air or launch it easily. In operation, this MAV would not fly constantly but "perch and stare," say on the corner of a building or inside it, for extended periods.
Contributing to such a scenario are new developments in microelectronics. Wilson specifically cited cameras that weighed 2g apiece a couple of years ago now being match-head size, 12 to the gram. GPS systems once the size of a cigarette pack are watch-size today thanks to cell phone electronics that meet Enhanced 911 requirements. And, he added, cheap, tiny lasers with only 30m range will be used for obstacle avoidance.
For propulsion, two systems seem most viable: a diesel that runs on available jet fuel and a thermo-electric device that derives power from exhaust pipe heat. Both also offer less noise than other engines.
The perch-and-stare routine and a form of "snooze" mode offer some operational advantages, he noted. For example, a 5-lb, 9-inch diameter baseline vehicle would require 1,500W to fly for an hour. The same MAV just transmitting data could function for a week, or up to 3 months in a sensor-watching mode, according to Wilson. Thus operation could be modified to achieve, say, 20 minutes of flight, one month of watching, and 2.5 days of transmitting without recovery or refueling. Contributing to power conservation, algorithms will permit only tracking moving objects and transmitting such updated information. The baseline vehicle is "dense" enough, Wilson told me, to be gust-resistant when perched. But if blown off, it should react quickly enough to restart the engine and reposition itself.
Wilson said MAV missions will include aiding ground robotic systems. Such functions include: detecting people in the vicinity of a ground robot or troops; scouting for hazardous holes a vehicle might encounter; and validating selection of firing targets.
Finally, while some components may cost thousands of dollars today, Wilson noted the goal is a vehicle cost of $700. To achieve this, volume component production would be needed along with such construction methods as "foaming" the vehicle in place around the wiring and frame structure.