It’s been several long years since RoboWrestling has gone to competition, but the time has finally come. Ahead of RoboWrestling’s first competition in over three years, we’ll be presenting a high level overview of their robot, Kirbi.
The RoboWrestling team was created to compete in autonomous sumo competitions, a specific brand of combat robotics in which small but mighty bots compete to push each other out of a metal ring, called a dohyo. For RoboJackets members who haven’t had a chance to watch a robot sumo match, it’s an intense race of speed and precision, and we recommend viewing the short video below for an overview. This year, RoboWrestling will be traveling to California to compete in the autonomous sumo division at RoboGames. This is the first year that sumo is back in the US after being canceled many years ago, so this is an exciting opportunity for the team to experience a real competition environment!
The work over the past years on Kirbi has been subjected to highs and lows. The lack of competition over the past few years has stunted parts of the design process as well as knowledge transfer from previous team members. Despite the setbacks, the team has been working hard and is excited for competition. On the mechanical side, the goal was to make the robot as robust as possible. Sumo robots are subjected to strict size and weight restrictions, so the focus is on developing a competitive advantage while keeping in mind physical tradeoffs. The mechanical subteam prioritized a good blade, the key part of the robot that leverages up the opponent off the ring, and an arrangement of strong magnets on the bottom of the robot. Since the dohyo is made of steel, the array of magnets give Kirbi an effective weight of over 300 pounds, though the robot’s real mass is only 3 kg. The goal with Kirbi’s mechanical design is to drive the blade underneath opposing robots to reduce their hold on the field and drive them out of the ring. Likewise, the higher Kirbi’s effective weight is, the harder it will be for opponents to leverage the robot off of the field. The mechanical team has also been looking towards the future of RoboWrestling by designing and building their own competition field, which would allow the team to test-drive their robots and gain more experience.
The electrical subteam has also made several improvements to Kirbi’s design. The new electrical configuration uses one motor controller for both motors, as opposed to the previous design which had two separate motor controllers. The single Sabretooth motor controller has improved specifications like higher continuous amperage and consolidated control signals, which will help with robot operation and simplify the circuitry. Kirbi also uses six distance sensors to find its opponent on the ring. Previously, every two sensors were multiplexed together before connecting to the teensy microcontroller. The multiplexed sensors would require a toggle back and forth to read each one through the I/O port, thus delaying data transmission from both sensors. These few milliseconds of delay could have big consequences in the speedy world of sumo robotics. The new sensor configuration still has four of the sensors multiplexed together into two ports, but the other two sensors are now directly and independently connected to the microcontroller for faster data reads. The biggest concern for the team going into competition is the battery life. With such a heavy effective weight, the motors can only be run for just over a minute before the 24V battery is completely drained. The electrical team hopes that with the short sumo matches, this isn’t a game-breaking issue. Overall, the mechanical and electrical foundations of Kirbi are solid and ready to compete.
The software team is responsible for the strategy that Kirbi will employ at competition. With such quick match times and consistent environmental surroundings, simplicity is king. The team opted for a hunt-and-seek strategy, affectionately known as slammy whammy. The algorithm uses data from the distance sensors to determine the opponent’s location. Then, there’s a threshold for action defined by a minimum distance to the opponent plus agreement from the multiple distance sensors on the opponent’s location. Once this threshold is met, Kirbi launches its attack by going full speed to plow the opposing robot off the field.
Each of RoboWrestling’s leads is excited for the opportunity to compete. Electrical lead Alex Peng says “considering that Robowrestling hasn’t competed in over 2 years, maybe 3? I’m just excited to be going to comp[etition].” This sentiment was echoed by the other leads on the team, as well as project manager Jason Katz. He stated, “We’re really excited to compete for the first time in 4 years, but because no one on the team has comp experience…we don’t really know the level of competition we’re up against.” There are many things that could go wrong with a robot which has been untested for so long, but regardless of the result, competition is an invaluable experience and bonding time for the team members. Whatever RoboWrestling achieves and learns this year at RoboGames, they will return with the motivation and inspiration to advance their knowledge of sumo robotics.