SICK Robot Day 2012.International competition for mobile robot. The challenge, organized by SICK AG, will be some kind of orienteering race. The course is a convex arena about 25 x 25 meters, which contains 27x3 balls of three different colors. At each round three robots must detect, pick and bring the ball with the assigned color to correct pen. The robots must avoid collision with other robots and the border of the arena. For other information see Robot Day general rule. The event took place on Saturday, October 6, 2012 in the Stadthalle in Waldkirch (Germany). Team ReadBeard Button from the University of Parma won the competition bringing 7 balls in first 10 minutes round.
The robot is a MobileRobots Pioneer 3DX equipped with Sick LMS100 and TiM300 range finders placed at two different heights, a Logitech C270 camera and a forklift for taking, carrying and dropping balls. Several alternative solutions have been considered for ball transportation.
The forklift has the advantages of avoiding sensor occlusions and of caging the ball during the navigation, although approaching, raising and dropping of the target require careful software management.
The control architecture consists of independent modules, each devoted to a specific task. During development and testing, components have been added, removed or linked differently to reach the proper final configuration. The ball detection components merge laser scanner and camera data to estimate ball position and color. Target tracking is provided to address intermittent observations and failures of detection algorithm. The localization and mapping modules detect the pen location from laser sensor and use this information to estimate and correct robot pose.
Since the ball positions are ephemeral and may change during the race, the pens and the border of arena represent the only stable landmarks that can be exploited to localize the robot. The navigation component is responsible for the robot behavior in the different situations. It primarily guarantees motion safety by avoiding collision with other robots, obstacles and balls. Furthermore, it handles the different phases of the competition: the random exploration of free space, the approach and detection of the target balls, the navigation to the pen, and the dropping of the ball.
The effectiveness of the developed robotic system has been proved by the 7 green balls picked and brought to the pen in the first round of Sick Robot Day. The robot has approached and caged only the green balls, also when balls of another color were in contact with the target balls. Furthermore, the robot has successfully reached the pen by exploiting the localization system.
The main pitfall has been apparent in the second round, when the robot wasn't able to successfully detect the white balls due to reflections and difficulties in the segmentation of such color. The lack of sensor data in ball dropping phase is the second limitation, which resulted in collision with the border and penalties. When the forklift is lowered, the laser scanner is partially occluded preventing the obstacle detection. A closer integration of sensor data could improve and overcome these problems.
Nonetheless, the experience is positive since the team has successfully addressed several design and development problems and has learned to iteratively improve the system from the experimental results.
- M. Cigolini, A. Costalunga, F. Parisi, M. Patander, I. Salsi, A. Signifredi, D. Valeriani, D. Lodi Rizzini, S. Caselli, Lessons Learned in a Ball Fetch-And-Carry Robotic Competition, Journal of Automation, Mobile Robotics and Intelligent Systems (JAMRIS), Issue 01, Vol. 8, p. 82-90, 2014. [pdf]
- Sick Robot Day Official Page