Platform one A robot can cover diverse environments as adeptly as animals by changing form on the fly, writes Nick Flaherty. The GOAT (Good Over All Terrains) developed at the CREATE lab at EPFL in Switzerland can spontaneously morph between a flat ‘rover’ shape and a sphere as it moves. This allows it to switch between driving, rolling, and even swimming, consuming less energy than a robot with limbs or appendages. “While most robots compute the shortest path from A to B, GOAT considers the travel modality as well as the path to be taken,” said researcher Josie Hughes at EPFL. “For example, instead of going around an obstacle like a stream, GOAT can swim straight through. If its path is hilly, it can passively roll downhill as a sphere to save both time and energy, and then actively drive as a rover when rolling is no longer beneficial.” The robot’s frame is made of two intersecting elastic fiberglass rods, with four motorised rimless wheels. Two winch-driven cables change the frame’s configuration, ultimately shortening like tendons to draw it tightly into a ball. The battery, onboard computer, and sensors are contained in a payload weighing up to 2 kg suspended in the centre of the frame, where it is well protected. This payload includes the power electronics, the electric winches, tendon lengths and morphological state to close the feedback control loop. “Most robots that navigate extreme terrain have lots of sensors to determine the state of each motor, but thanks to its ability to leverage its own compliance, GOAT doesn’t need complex sensing,” says research assistant Max Polzin. Future research avenues include improved algorithms to help exploit the morphing as well as scaling GOAT’s design up and down to accommodate different payloads. Looking ahead, the researchers see many potential applications for their device. “Robots like GOAT could be deployed quickly into uncharted terrain with minimal perception and planning systems, allowing them to turn environmental challenges into computational assets,” says Hughes. Ground vehicles Morphing robot covers more ground all sensors, and processing units. Only the wheel motors are mounted to the frame. GOAT also navigates with minimal sensing equipment, using only a satellite navigation system and an inertial measurement unit (IMU). All the sensors communicate via I2C to the central processing unit, a Raspberry Pi 5 and all motors are directly powered from three lightweight lithium polymer battery cells in series. The robot can be remotely controlled through a ground station computer connected via WiFI or a 3G connection. A cascaded control scheme enables the active reconfiguration of the robot’s shape. The morphological trajectory controller computes the tendon lengths to change the structure, and sends the signals to the winches. Sensor measurements enable estimating the The GOAT robot can change form a rover to a sphere (Image courtesy of EPFL) Is your job search lacking focus? Frustrated at looking for autonomous and robotics related engineering vacancies on generic job boards? Visit www.uncrewedengineeringjobs.com for a clearer view of what’s on offer.
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