110 Digest | Skyline Robotics Ozmo safety system that stops it when it detects any contact. A modular add-on, customfitted to each robot model, the Airskin is a system of soft, pressure-sensitive pads that form an airtight skin over a flexible support structure. This structure also houses dualchannel sensors that detect pressure changes when a pad is deformed by a contact anywhere on its surface. Each pad has an integral piezo-electric micropump that maintains an overpressure of 400 Pascals which serves as a reference for correct operation, while all the pads are connected in series and monitor each other for integrity every 4 ms. The force threshold that triggers a safety-rated protected stop is 5 Newtons. The Ozmo, however, is more than a collection of components from vendors, and creating an effective integrated whole presented some engineering challenges. As Blum explains, “Robotic systems in general are relatively complex, and you need to bring a few competencies together across mechanical, electrical and software disciplines. High-rise challenges “With the Ozmo, we have a few challenges in our working environment. We’re in an outdoor multi-variable environment, and we need to be able to adjust and react to things in true real time. Wind gusts can come along at any moment, so we have to stabilise the platform to ensure the basket doesn’t crash into the facade or create any sort of safety incident,” Blum says. “From a machine vision standpoint, we’re localising and mapping on highly transparent and reflective surfaces, so sunshine, shade and cloud movements present different challenges.” To help tackle this problem, the cameras are spaced vertically and laterally from one another so that they can image the facade from different angles, which is helpful in 3D mapping of reflective/transparent surfaces because algorithms can use it to reduce optical noise from such surfaces. This photogrammetry is combined with the direct range measurements to the surfaces provided by the Lidar. The mapping itself is performed by 3D point cloud stitching and processing, with localisation through visual odometry. He also notes that Skyline had to solve some knotty comms problems over a long tether. “When you’re in the centre of these metropolitan areas, there are some really interesting radio frequency patterns, and we need to be able to pass comms from the rooftop down to the robot and vice versa, in absolute real time,” Blum says. “These days, when you’re constructing a building, you’re advised not to run an Ethernet cord for more than 100 m, because at that length you’re going to start to lose throughput. We’ve had to come up with an innovative solution and, at this point, we’re able to transmit about 127 Mbit/s at 400 m through a cable that’s insulated and protected.” Like most of the comms equipment in the Ozmo system, this shielded cable and its connectors come from Rockwell International’s Allen Bradley division. The cable also carries electrical power to the Ozmo. “I wish it were batterypowered, but, that doesn’t seem like a viable solution at the moment because of weight. All these cradles have weight limitations for safety,” Blum says. “So the power and comms lines come from the rooftop, pass power down to the robot on the platform, and then the robot gives its sensors the power they need.” Under pressure Water pressure is also an issue, but it is one of avoiding excessive pressure rather than dealing with insufficient pressure. This is because the Ozmo takes the water supply from the building’s main tank on the roof, which is much easier than pumping it up from ground level. “We don’t want a water line to burst down the side of the building. If you’re 100, 200, 300 m down a building, you have to imagine yourself diving that deep into the ocean where the pressure would increase around you,” Blum says. “So we had to come up with a system that would allow a mixture of air and water flow into the water line.” While water is incompressible, air will compress and absorb energy that might otherwise rupture the hose. “So, depending on the elevation of the platform, there would be different mixtures of air and water,” he says. December/January 2024 | Uncrewed Systems Technology The Airskin pressure/impact sensing safety system installed on a Kuka robotic arm will stop all movement in response to a calibrated contact force (Courtesy of Airskin)
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