Kharagpur RoboSoccer Students’ Group
Project Status: Ongoing
About KRSSG and Me
KRSSG is a research group of IIT Kharagpur dedicated to the development of autonomous soccer playing robots. The group is headed by Prof. Jayanta Mukhopadhyay, Department of Computer Science and Engineering and co-guided by professors from Electrical and Mechanical Engineering. The group also participates in international competitions RoboCup and FIRA.
I joined the group in my freshman year as a Mechanical Team member and currently lead the team. My work mainly revolves around the Mechanical design of both wheeled and humanoid robots, and the optimization of various sub-systems of the robots. Being with the group also helped me gain insights into embedded electronics, controls and artificial intelligence. My interests in the field of humanoid robotics led me to take up my B-Tech project in the same domain.
My Work
Optimization of Kicker
The SSL robots consist of a straight kicker and chip kicker – to chip the ball through the air. The kicker is composed of a solenoid and an iron plunger. The kicker can kick up to the speeds of 6m/s and the solenoid is powered by a flyback converter based R-C circuit which can charge up to 220V in just 2 seconds. Due to the small size of the robots, measuring about 15 cm in height and 18 cm in diameter, space is a real constraint. In order to utilize the maximum charge stored in the capacitors optimization was required.
The previous design for straight kicker had a cylindrical geometry for the solenoid, which although is a compact design, it is increasing the height of the robot. So, I proposed to use a cuboidal geometry and use two of them one over the other. This would facilitate having solenoids of same power for both straight as well as chip kicking, while earlier a smaller solenoid was used for chip kicking. Then we further optimized the geometry of the solenoid using MATLAB and FEMM and determined the dimensions as well as required amount of wire windings considering factors such as magnetic field, current and resistance. Too much winding would mean more resistance, a lesser current and hence a lowered magnetic field. Also, it would mean lesser volume of iron plunger thus it will decrease the amount of energy absorbed.
Dribbler Design
The earlier design of the ball dribbling mechanism had certain design problems which reduced its dribbling capabilities. As per RoboCup rules, only horizontal rod type dribbler is allowed during the match. So, getting the ball to be in contact with the ball is a tough challenge and required some serious dynamic analysis.
Before we delve deeped it is recommended to go through my blog on “An Ordeal with Dribbling” to know more about dribblers in case you don’t.
Here is a short video of the current dribbler being tested.
Coming to the analysis, it turned out that the dribbling characteristics depended a lot upon the ground and dribbler rod friction values with the ball, the amount of torque provided by the motor, and the angle of contact of the dribbing rod with the ball. As with the previous design, the angle of contact would constantly change – due to rotational motion of the dribbler rod for damping. Also, the gear ratios were not optimum, thus we calculated the optimum gear ratios through mathematical modelling and changed the design to incorporate a linear damping mechanism while still having the flexibility to adjust the angle of contact as per requirement.
3D Printed Bot Design
The manufacturing costs are really high for each of the robots due to a lot of small parts and an aluminium chassis. And given there are seven of them, it becomes infeasible to make quick changes to the design and get it fabricated.
While the idea of 3D printed robots can seem crazy since they can collide with speeds up to 10 m/s and other assembly issues, I am currently working on to make it happen. This way not only can we save on costs but also improve the designs and make quick prototypes.
Some videos to showing the bots in action!
Ankush Roy 