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Tactical mobile robots used in military and lawenforcement operations normally require a robust, longrange, and non-line-of-sight (NLOS) communications link to the remote control station. This is especially true for Explosive Ordnance Disposal (EOD) operators using robots to defeat Improvised Explosive Devices (IEDs). Highfrequency digital radio communications, currently the preferred technology, are subject to line-of-sight (LOS) limitations, and thus are often impossible to maintain in urban environments. We have developed a system that will allow the mobile robot to carry multiple relay radios that are automatically deployed when and where needed in order to maintain robust communications. This process is completely transparent to the operator and is entirely handled by the ad-hoc network formed by the relay radios. The system is plug-and-playable, and can be attached to many manned and unmanned vehicles requiring long-range and non-LOS operational capability. Experimental data compares the effective range achieved with and without the use of our relay deployment system.

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Maintaining a solid radio communication link between a mobile robot entering a building and an external base station is a well-recognized problem. Modern digital radios, while affording high bandwidth and Internet-protocol-based automatic routing capabilities, tend to operate on line-of-sight links. The communication link degrades quickly as a robot penetrates deeper into the interior of a building. This project investigates the use of mobile autonomous communication relay nodes to extend the effective range of a mobile robot exploring a complex interior environment. Each relay node is a small mobile slave robot equipped with sonar, ladar, and 802.11b radio repeater. For demonstration purposes, four Pioneer 2-DX robots are used as autonomous mobile relays, with SSC-San Diego's ROBART III acting as the lead robot. The relay robots follow the lead robot into a building and are automatically deployed at various locations to maintain a networked communication link back to the remote operator. With their onboard external sensors, they also act as rearguards to secure areas already explored by the lead robot. As the lead robot advances and RF shortcuts are detected, relay nodes that become unnecessary will be reclaimed and reused, all transparent to the operator. This project takes advantage of recent research results from several DARPA-funded tasks at various institutions in the areas of robotic simulation, wireless ad hoc networking, route planning, and navigation. This paper describes the progress of the first six months of the project.Keywords: robotics, communications, RF, relays, 802.11, ad hoc networking OBJECTIVESOne of the vulnerabilities of current mobile robots operating in real-world scenarios is the communication link to the operator's console. Fiber-optic cables reduce mobility and often become entangled and broken, rendering the robot inoperable. User surveys have identified radio-frequency (RF) communications systems as more desirable.1,2 However, most RF communication systems currently employed on teleoperated robots in the field are analog, which very often experience signal interference, multipath, and attenuation problems when used in an urban environment. Spread spectrum digital systems are more immune to these problems and provide a level of transmission security, but operate at shorter ranges and mostly on line of sight.To extend the range of digital radios and provide non-line-of-sight service, the use of dropped static relays or autonomous robots as relays have been discussed, usually in the context of a larger project, from creating a network of distributed mobile sensors 3 to exploring for life on Mars. 4 Our project goal is to move this concept out of the discussion and simulation stages and demonstrate it using real hardware to solve a real-world problem.We want to automatically maintain a solid high-bandwidth digital RF communication link between a robot exploring a large indoor environment and the operator stationed outside the building. This task must be performed without operat...

In the area of logistics, there currently is a capability gap between the one-ton Army robotic Multifunction Utility/Logistics and Equipment (MULE) vehicle and a soldier's backpack. The Unmanned Systems Branch at Space and Naval Warfare Systems Center (SPAWAR Systems Center, or SSC), San Diego, with the assistance of a group of interns from nearby High Tech High School, has demonstrated enabling technologies for a solution that fills this gap. A small robotic transport system has been developed based on the Segway Robotic Mobility Platform TM (RMP). We have demonstrated teleoperated control of this robotic transport system, and conducted two demonstrations of autonomous behaviors. Both demonstrations involved a robotic transporter following a human leader. In the first demonstration, the transporter used a vision system running a continuously adaptive mean-shift filter to track and follow a human. In the second demonstration, the separation between leader and follower was significantly increased using Global Positioning System (GPS) information. The track of the human leader, with a GPS unit in his backpack, was sent wirelessly to the transporter, also equipped with a GPS unit. The robotic transporter traced the path of the human leader by following these GPS breadcrumbs. We have additionally demonstrated a robotic medical patient transport capability by using the Segway RMP to power a mock-up of the Life Support for Trauma and Transport (LSTAT) patient care platform, on a standard NATO litter carrier. This paper describes the development of our demonstration robotic transport system and the various experiments conducted.