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48 Emergency services UGV manufacturer Tecdron’s newest system, the Sentinel, is now in service with the Paris Fire Brigade. The Sentinel is designed with rails and mounts to allow it to be equipped with a number of different systems. A fire hose can be fitted to project jets of water, and the vehicle can also pull up to 200 m of hose with water flowing in it. A series of pipes and nozzles can also divert water from the main supply and spray it across the electronics, motors and tracks of the system to protect itself against fire damage. For underground fires, a smoke extraction fan can be fitted, and a stretcher can also be fixed atop the vehicle for carrying injured people to safety. The Sentinel weighs 450 kg and can carry up to 800 kg. It moves on two caterpillar tracks that can take the UGV up 45° slopes, 40° side slopes, over 30 cm obstacles and deliver up to 12,500 N of traction force. “Unlike our previous platforms, we chose to manufacture the Sentinel using ‘boiler-making’ processes – fabricating with metal tubes and plates and the like – as they are more economical than conventional machining, and give a lower total parts count, which makes the assembly, disassembly and maintenance of the robots much easier,” says JeanCharles Mammana, program manager at Tecdron. “We also decided to change from the DC brushed motors we normally use to brushless DC motors,” he adds. “While brushless motors are more complex to implement, they offer more power for a given weight, they do not wear down as much if properly controlled and monitored and thus require less maintenance. They also have a much longer lifespan.” The Sentinel also uses a custom- designed embedded computer to monitor the health of all the onboard systems, to help ensure they are functioning normally in the extreme heat and dust of a fire. That said, all its motors, batteries and electronics are housed in dust-proof enclosures for extra protection. And in a boon to mountain rescue or earthquake relief workers, researchers from the University of Tokyo are developing technologies for teaming a UAV with a UGV to help the latter scale steep obstacles such as cliffs or rubble. In their technique, the UAV would first survey the UGV’s preferred route and generate a 3D map of the area. This information would then be fed back to the UGV, to generate an elevation map. This will enable the UGV to engage in dynamic route planning to minimise the number of cliffs and other obstacles encountered. Thanks to its greater SWaP capacity, it will be able to use a larger and more powerful onboard computer than the UAV. If a cliff cannot be avoided during an ascent, the UAV will be able to lift a tether from a winch on the UGV, and attach it to a fixed structure such as a tree, enabling the UGV to pull itself up the steep incline. The team has performed initial tests of this concept at an artificial indoor ‘field’, using a customised quadrotor UAV powered by an Nvidia Jetson TX 2 processor and a 100 Hz Lidar. The UGV’s caterpillar tracks are custom-made, and it runs a UP Core processor. Although various tether attachment April/May 2019 | Unmanned Systems Technology Tecdron’s Sentinel UGV is in service with the Paris Fire Brigade, and can be fitted with smoke extractor fans (left) or hoses for helping to deal with underground fires