Designers of the top adult-size robot in RoboCup’s humanoid soccer league share their work. The recent soccer World Cup was won by a fine French team that triumphed over Croatia in a dramatic finale. You were watching the wrong tournament.
On the other side of the world in Montreal, another tournament was also underway. This was the soccer World Cup for adult-size robots. It was won by a robot called “NimbRo” for the second year in succession. NimbRo is German and represents a nation with a long history of football prowess. Today, NimbRo’s masters outline some of the challenges they faced in designing their electronic hero. The original design was for the 2017 RoboCup in Nagoya, is for adult-size machines. The work suggests that roboticists have made significant progress. There is huge potential for improvement in the next few years.
RoboCup began in 1997. This is to test various emerging technologies related to robotics, machine vision, task planning. But many readers will recall tournaments in which the players have been less than spectacular.
Robot world cups are generally remembered for the clumsy stumbling gait of the players. Their comical mix-ups and the concern of their human masters are often watching through their fingers. These robots have been tiny, and often not even humanoid.
That’s mainly because of the difficulty powering and controlling large machines, particularly of the two-legged variety. And in any case, walking, running, and kicking with two legs are just some of the many tasks that roboticists need to solve to automate football. With the rapid advances in artificial intelligence and robotics, it’s easy to imagine that machines are set to gain mastery over soccer.
They have with chess, Go, and any number of Atari video games. In recent years, more powerful and efficient actuators have made it feasible to build adult-size robots. They can compete in World Cup-style competitions. Enter NimbRo, a two-legged robot built in less than six months for the 2017 tournament by Grzegorz Ficht and colleagues at the University of Bonn in Germany.
Meet the Winner of Robotic’s World Cup
Adult-size robots must be 130 to 180 centimeters (51 to 71 inches) tall. NimbRo is 135 cm tall and weighs 18 kilograms (almost 40 pounds). The competition itself involves a series of games against single opponents followed by a final in which the player that scores the most goals wins. There is also a set of technical challenges such as kicking a moving ball, jumping, and recovering from a push. NimbRo has a number of features that make it particularly good at these tasks. In particular, it is simple, so parts can be easily maintained and replaced.
“The structure of the robot has been simplified as much as possible to maintain low complexity, but retain functionality that is required when playing soccer,” say Ficht and co. The exoskeleton consists of a few simple parts all 3-D-printed from nylon. “By taking advantage of the versatility of 3D printing, we were able to develop an affordable, customizable, highly-capable, adult-sized humanoid robot in little time,” said the team.
Robotic’s World Cup
Most of the parts are symmetrical so that they can be used in multiple places. This reduces the number of spare parts. Vision comes via a single Logitech C905 camera with a 150-degree field of view. The data is processed by an onboard Intel NUC mini PC. This performs object detection, robot localization, task planning, and actuator control. All this gives the robot a number of soccer-playing abilities. It must be able to locate and approach the ball, avoid obstacles such as other players, and kick and dribble.
NimbRo performs well. In five games, the robot scored 46 goals while conceding only one. That was in the final against a robot called, rather unflatteringly, Sweaty. NimbRo also picked up 21 points in the technical challenges, giving it a clear victory.