8 A team of engineers in the US has developed a robot that can reconfigure itself into eight different modes, including a UAV (writes Nick Flaherty). The Multi-Modal Mobility Morphobot (M4) robot, developed at the Caltech Centre for Autonomous Systems and Technologies (CAST), can autonomously assess the environment it faces to choose the most effective configuration. The 6 kg robot can roll on four wheels, turn its wheels into rotors and fly, balance on two wheels to peer over obstacles, ‘walk’ by using its wheels like feet, or use two rotors to help it roll up steep slopes on two wheels or even tumble over rough terrain. The 3D-printed carbon fibre articulated body has four legs, each one having two actuated hip joints for frontal and side leg movements, and a shrouded propeller that acts as a wheel and thruster simultaneously. The front joints permit the legs to move in the sideways direction, while the sagittal joints accommodate forward and backward swing movements in each leg. This allows the various transformations. To achieve a UAS configuration, the legs first swing forward and backward. They then turn sideways with the front actuators to be used as propellers. In the M4, the propeller’s shroud acts as a wheel, which is actuated by a motor that drives through the gears attached to the shroud’s rim. The propulsion is generated by the propeller and motor inside the shroud aligned with the wheel axis. If the motion of the propellers and shrouds is considered, the robot possesses a total of 16 actuators and body degrees of freedom (DOF). As a result, the total number of DOFs in the M4, including actuated coordinates, body positions and orientations, is 22. The autonomous operation is aimed at space applications, allowing the M4 to assess offworld terrain and change the mode in response. One of the M4’s key features is the ability to repurpose its appendages to form wheels, legs, or thrusters. When it needs to stand up on two wheels, two of its four wheels fold up and the inset propellers spin upwards, providing balance for the robot. When it needs to fly, all four wheels fold up, and the propellers lift the robot off the ground. “Our aim was to push the boundaries of robot locomotion by designing a system that showcases extraordinary mobility capabilities with a wide range of distinct locomotion mode,” said Alireza Ramezani, assistant professor of electrical and computer engineering at Northeastern University, who worked on the design. “The M4 project successfully achieved these objectives.” The M4 uses two microcontrollers for low-level locomotion control. One is used for posture and wheel motion control based on an ARM Cortex-M7 core, the other is to regulate thrusters using an ARM Cortex-M3. There is also a high-level decisionmaking computer for autonomous multi-modal path planning using an Nvidia Jetson Nano GPU module. Multi-mode vehicles Eight robots from one Platform one October/November 2023 | Uncrewed Systems Technology The M4 can autonomously assess the environment it faces to choose its most effective configuration
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