Sunday, July 15, 2007

A Robot Fielder for Cricket

A number of robots bowling cricket balls have been proposed, and many have been built. But there are not many machines for fielding, which requires computer vision or some substitute, the ability to predict the ball’s trajectory, considerable skills in catching a ball in flight and effectively throwing it back to the wicket keeper or bowler. One publication you may wish to consult is

An introductory course in mechatronics: Robo-CricketWyeth, G.Mechatronics and Machine Vision in Practice, 1997. Proceedings, Fourth Annual Conference onVolume, Issue, 23-25 Sep 1997 Page(s): 20 - 25Digital Object Identifier 10.1109/MMVIP.1997.625232

What I propose here is a free running fielding robot to play with human cricketers on a real cricket field. There must be a hundred different options in building a robot like this, but let me offer one set of options for the design for the main subsystems.

The computer vision component: Three cameras strategically located around the playground, looking at the batsman, should work with a computer to identify the ball and predict its trajectory and time and place of falling. Wireless links should carry the information to the robot. There is no reason why the robot cannot carry the computer, though that is not very necessary to demonstrate the working of the basic design.

Ball capture mechanism: This would need to catch balls in different trajectories – including a high trajectory, a low trajectory and one which involves the ball bouncing off the ground in a few places and/or rolling. A funnel like device about a square meter in cross section could be useful to catch balls coming down after flying several meters above the ground. Tilting the bucket-like funnel could catch low flying balls. Catching a ball bouncing along or rolling along the ground would require a bucket that can be tilted to come close to touching the ground. A square or rectangular mouthed funnel would be ideal for intercepting bouncing or rolling balls.

Navigation: A three wheeled vehicle with three independently driven wheels could be useful. The wheels could be suspended by individual legs, each working like the nose wheel of an aircraft, being free to swivel around the vertical support axle. I believe that this could eliminate the mechanical component of a steering mechanism. Sensing the direction along which each wheel is rolling and differential drive to the wheels could provide for electronic steering. Navigation would involve running to a suitable place to catch the ball and orienting oneself to face the incoming ball.
All this would involve the robot having to “know” its own coordinates and orientation. Some form of a position sensor and a gyrocompass-like device might be necessary.

Building a system with adequate power to provide the necessary acceleration and speed would be a demanding challenge. I estimate that a human fielder manages to do this using about 600 watts of power. A vehicle driven by a large rechargeable battery could manage with less power. How many hours of fielding such a battery would cover has to be examined. Is there room for a solar panel? I do not know.

Communication: It would be useful for the robot to use a speech synthesizer and a variety of canned utterances to radio its own comments as it chases balls. A few examples of the utterances follow:

Boy! That one is a sixer!

Well, I will get that one!

He is a goner!

Now I have to run like crazy!

John, I leave this one to you!

Throwing the ball back: This might require some form of an air gun, and a pump for recharging the pneumatic tank. The computation fo the launch angle, throwing velocity and direction of throw would be a demanding one.

Why do we need to build this gadget? I do believe that this would be a great training ground for future robotics engineers. And they would have a whale of a time during the learning phase!

I believe that a channel telecasting a cricket match would love to have a fielding robot to liven up the match! Will they pay for the R & D? That is the important question.

Srinivasan Ramani

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