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Stable Passing and Ball Motion Planning for a Bipedal Robot

Established in 1997, the RoboCup promotes research in cooperative multi-robot and multi-agent systems through the game of soccer. ETH's team, the Nomadz, competes in the RoboCup Standard Platform League, a five-a-side robotic soccer league. The teams in this league use humanoid NAO robots, developed by Aldebaran Robotics.

Accurate and stable passing is a crucial feature that our team needs help with. This project will focus on improving the stability of kicking motions, adding more advanced kicking motions like an angled side kick, and reducing the time spent lining up behind the ball prior to a pass. Several previous student projects have focused on features related to passing, including variable-strength kicking, targeted passing to a specific location on the field, ball detection using an external vision system, and determination of locations on the field where passing is possible. These projects provide a good basis for this project, but refinement and iteration of these features is also needed.

In addition to the physical passing motion, this project will also determine a passing strategy. Since the robot can now adjust the pass strength to (more or less) precisely kick the ball to a given location on the field, the next task is determine where to kick it. This part of the project will determine locations on the field that are more accessible to teammates than to opponents, based on the position and orientation of the opponents.

The project is composed of two tasks:

• Improving Passing Motion:
  • Undertake a literature review and theoretical study of the kinematics of kicking a ball. Determine the leg joint trajectories that correspond to the foot striking a ball in a particular direction, with the ball moving at a given velocity after the kick.
  • Study and improve upon previous efforts to kick the ball sideways, rather than simply straight ahead with the front of the foot.
  • Reduce the time the robot spends aligning behind the ball in preparation for kicking.
• Strategic Passing:
  • Given complete knowledge about the position and orientation of all robots, devise a strategy to determine where to pass the ball next. This will potentially take into account game theoretical aspects, and should be flexible for use in a defensive context as well – namely how to position defenders to prevent opponents' dangerous passes.

The student will start with a review of the robot kinematics, as well as the current software architecture for passing and kicking. The student will develop a simple Matlab simulation illustrating the optimal location of a pass given the position of players on the field, as well as the optimal position of defenders to prevent such a pass. The student will understand the steps necessary to improve the current kicking behavior and introduce sideways passing. This summary, as well as a results of the Matlab optimization will be presented in a short midterm report. The stable passing behavior, sideways kicking, ball alignment, and strategic passing locations will be implemented and tested in the SimRobot simulation framework. Once this is working, the behavior will be tested and verified on the physical robots.

The student will produce accurate and extensive documentation of the behavior being implemented. The final documentation must be a self-contained description for later reference by other users. It is recommended that the student produces updated drafts of the final paper as the project tasks are being accomplished.