26 Dossier | Keybotic Keyper It can walk at up to 2 m/s (7.2 kph) on its four legs, but that is too fast for industrial complexes, so typically it is rarely higher than 1 m/s. Rather than undergoing defined iterations or phases, the Keyper’s engineers have repeatedly tuned and upgraded its subsystems using a more evolutionary approach. “If we’d designed this uncrewed vehicle to be modular, we’d risk making individual sections or even the overall design suboptimal, because you can make mistakes like oversizing compartments, fittings or joints to make detaching or replacing subsystems easier,” Tome explains. “With this robot we’re dealing with a major challenge in terms of actuation, for which we can’t afford any sub-optimal decisions. “Industrial robots are precisely controlled for positioning, but generally they’re not made to resist impacts. With the Keyper though, we want it to resist impacts and regulate the force it imparts with its legs. “When you walk, when successful robots walk, there’s little precise control of leg positions. What we’re really doing is controlling the way our limbs interact with the floor and where we place them.” To achieve fine control of locomotive force, Keybotic had previously used harmonic drives (also known as strain wave gear systems) with custombuilt torque sensors for turning the high speed of their actuators into high torque, as is common in robotics; impacts however will cause these to break easily. The company notes two conventional approaches for countering this: a spring to absorb impacts, or a clutch so that the reducer can slip in moments of excess torque. “Both introduce extra components and hence points of failure and expense however,” Tome comments. “So Louis Mouzet, our principal mechanical engineer, decided we’d design a totally new and unbreakable actuation and gearing system ourselves. “That took a few months. Building an actuator requires building a complex test rig and stressing each version of your actuator beyond its limits between five and 20 times, then finding breaking points to inform your next version. We might not have gone for modularity with the Keyper, but in our proprietary actuator we had a modicum of modularity, swapping motors, gears and sensors to evaluate what was best.” Once it was satisfied that its actuator was optimally reliable and could control the leg output force effectively, the leg was optimised around three such actuators, and a test rig was built in which the leg could be subjected to repeated shocks and other forces while stationary or jumping for many hours. Then came the design and engineering of the body, it being a cuboid that at first simply had to sit between four of the leg units. Once that was done it was fastened with four legs, and the prototype was ready, just 6 months after Tome had assembled his team in late 2021. Since then, the team has iterated the subsystems, gradually moving towards tighter integration, optimising for intelligence and efficiency. The Keyper’s architecture In determining the balance of components between the Keyper’s body and its legs, Keybotic has sought to minimise the number of them inside each leg, as a lighter leg means lower inertia, enabling it to move faster to help maintain its balance. As a result, the Keyper’s body contains all the hardware for sensing, processing, comms and energy storage, with the legs storing only the actuators. Energy is stored in a lithium-ion battery and distributed to the rest of the robot via a power control board, with a charging receptacle on the underbelly. Two Intel 12th-generation CPUs form the Keyper’s core processing ‘brain’, one of which is broadly dedicated to deterministic tasks such as locomotion and the required perception, and the other to asynchronous functions such as task planning, optimisation and arbitration of routes, and user code. “Customers will need their own code for integration purposes, and we didn’t want them to install their own companion computer, as allowing the Keyper to run with untried additional core hardware could risk changing its behaviour, so we’ve provided extra processing space and bandwidth by having two Intel CPUs,” Tome explains. October/November 2023 | Uncrewed Systems Technology The company has designed and built its own actuators, with complex test rigs to stress and break each iteration to improve its successor
RkJQdWJsaXNoZXIy MjI2Mzk4