Robots in Surveillance
Article

Robots in Surveillance

Safe Navigation for Autonomous Robot Systems

Unmanned airborne systems operating in tandem with ground-based mobile platforms to capture an area autonomously support and improve the work of surveillance staff, repair servicemen operating in hazardous environments and many others. Yet, such systems are not widely used in civilian applications due to cost and complexity. The authors developed an unmanned ground system which – using GNSS and other positioning devices – accurately follows a pre-specified path while avoiding obstacles. Tests show that the prototype is user-friendly, safe and easy to operate.

The German SiNafaR project (‘Safe Navigation for Autonomous Robot Platforms’) was aimed at developing high navigation accuracy of robotic surveillance systems and their user-friendly, safe and easy operation. In the project, which ran from late 2010 to January 2013 as a co-operation between Fraunhofer IIS, University of Würzburg, Zentrum für Telematik e.V., EADS Deutschland GmbH and Wilkon e.K, laser scanners, cameras, GNSS, INS and other navigation tools were mounted on a copter and on a four-wheeled vehicle. Combined with own software developed during the project, it was possible to achieve high accuracy both for the unmanned airborne system (UAS) and mobile unmanned ground system (UGS).

UAS and UGS

The autonomous mobile robotic systems used within the project operate from the air and from the ground. A UAS can move quickly through the air, generates bird’s-eye view images and images parallel to the terrain, and its operation benefits from the absence of obstacles at higher altitudes. But a UAS can usually stay airborne for less than one hour. In contrast a UGS can operate for many hours if not days, thus allowing near-permanent surveillance. However, the data is taken from a frog’s perspective resulting in much occlusion. Moreover, the wireless connection could be disrupted due to the presence of obstructing buildings and other ground structures. In the project, a fuel-powered helicopter from EADS was chosen as the UAS. Its maintenance is relatively easy, the components are inexpensive and the copter can carry sufficient payload for the purpose at hand. Figure 1 schematically shows the hardware components. The system features a commercial off-the-shelf autopilot that is guided by a pre-specified set of waypoints, which can be easily updated or adapted to flight conditions and the surveillance crew’s demands. The on-board pan-tilt camera is controllable from a ground station, for example to search for obstacles on the ground that may obstruct the locomotion of the UGS. If obstacles are present, the path of the UGS may be adjusted. Tele-command and position information are transmitted through separate data links. The on-board computer handles route planning, marker detection and communication. To meet requirements on payload and size, a four-wheeled vehicle was chosen as the UGS: the Mobile Experimental Robot for Locomotion and Intelligent Navigation (MERLIN). Figure 2 shows the hardware components of the UGS. A laser range finder is used for obstacle detection and the built-in pan-tilt-zoom camera delivers the video stream. Figure 3 shows a diagram of the entire SiNafaR architecture. 

Read the full article in the online edition of GIM International.

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