Uncrewed Systems Technology | February/March 2025 Robotnik RB-WATCHER | Digest That localisation process is not SLAM. While it is performed in real time, the map within which RB-WATCHER localises is either derived from GPS data when outside or from an embedded dataset that is generated before its autonomous inspection work officially begins. “The robot comes with a remote controller, so that someone can connect it, trigger the mapping procedure via a web browser, and control it as it collects data via its Lidar and RGBD camera for a 3D map of the facilities it is to inspect and the routes it is to take,” Millet says. Compute Data from the GPS, IMU, Lidar and stereo camera all feed into an off-the-shelf Intel i7 CPU model and board chosen for its high RAM and SSD storage capacity (typically, a system between the 10th and 12th generation is used). That CPU processes the navigation inputs to generate movement decisions for the powertrain and the inspection head to go through preplanned mission objectives, such as GNSS waypoints and inspection targets. In addition to using ROS as middleware, Robotnik works with Energy Robotics for an upper layer of software that collates and interprets both the navigation and inspection data coming from the RB-WATCHER, with cloudbased processing for those requiring intelligent analytics of the data (although initial processing of all data is done at the edge as standard). “The RB-WATCHER’s onboard software originally came from the RBSUMMIT, before being developed for key needs like inspection packages particular to industrial users,” Millet says. “We mainly used open-source tools, as well as algorithms developed and stored following the wide range of r&d projects we’ve taken on over the years. The final algorithms used in the RB-WATCHER were created by extrapolating the best lessons and code for this use-case from each of these.” Powertrain The RB-WATCHER runs on four electric motors, each integrated inside its respective wheel and outputting 500 W at the UGV’s 9 kph normal operating speed. This configuration avoids the need for a gearbox that would take up weight and volume inside the small robot body, and it also enables skid-steering by way of torque vectoring. The RB-WATCHER can thus turn on the spot, maximising its nimbleness in potentially cluttered indoor floor spaces. “The tyres around the wheel are the same rubber, deep-tread items we used on the wheels of the RB-SUMMIT for many years. As that UGV was a multipurpose system, which needed to be able to move in different terrains, environmental conditions and inclines, it made sense to use exactly the same tyres on the RB-WATCHER, which may drive through sandy, uneven outdoor spaces, or dirty or wet indoor spaces,” Millet adds. “The motor-control drivers we chose after testing many different units, with reliability being one of the most important traits we were after. We eventually chose a unit that exhibited very consistent communication with the CPU; not just to make sure the driver was receiving control output commands for the motors, but also to be certain that the CPU could always monitor the motor controllers and make sure they’re working correctly, making it a closed loop.” The battery is built around lithium iron phosphate (LFP) cells; a cathode chemistry used in Robotnik’s previous battery-electric solutions for its touted safety and electrical stability benefits. The pack in the RB-WATCHER is designed for a 48 V output bus and it is sized for 15 Ah of energy capacity. Robotnik chose this chemistry and formed its pack design around several other key capabilities it needed. For instance, optimising its ability to recharge quickly would minimise downtime; conversely, fast discharging was important as the motors can occasionally request a very high current – for example, when moving on surfaces with poor grip or on inclines (with the UGV able to move on inclines of 80% or 38.66°). “With the C-Rates the pack can achieve, the RB-WATCHER’s battery can go from empty to a full state of charge in about two hours, which then gives it four to five hours of runtime,” Millet says. After driving into the charging station (with the front of the RB-WATCHER’s body fitting into its receptacle), conductive contacts on the front of the UGV connect with contacts in the station. Magnetic sensors in the charging station confirm whether the connection has occurred successfully, and if it has, power starts being transmitted to the robot, typically at 600 W. 55 The inspection head camera was chosen primarily for its size; too large a unit and the resulting vibrations and inertia would have interfered with stable imagery gathering
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