Basketball robot shoots worse than some humans

Today, at the Carnegie Science Museum in Pittsburgh, I watched their resident basketball robot shoot some free throws.  Here's a video of what it looks like.

How accurate do you think the robot is?  Take a guess before you read on.  (Or, just read on -- who am I to give you orders?)

The answer is ... not that accurate.  Well, at least, a lot less accurate than I thought.  When I was there, the robot's FT% was only 83 percent (405 for 488).

I was a bit shocked.  I expected close to perfect.  After all, it's the same throw under exactly the same circumstances, every time.  (Actually, it's two different shots: sometimes the robot throws underhand, and sometimes overhand from behind his back.  But, I witnessed the robot missing shots from both positions.)

It seems wrong, doesn't it, that a human can outperform an expensive robot at a repetitive physical task?  In his career, Rick Barry routinely shot over 90 percent (albeit underhanded).   So, the machine misses almost twice as many shots as Barry. 

What's going on?  I don't know.  

For what it's worth, here's my theory:

The robot lets the ball roll down the ramp that's his "hand" before actually doing the throw with his "arm".  Maybe the position it reaches varies randomly, based on random differences in friction.  Maybe if a dirty part of the ball contacts a dirty part of the arm, the ball doesn't quite reach the expected point, and the throw misses.

There could be other friction-related issues that cause variation, like, perhaps, the axis of rotation of the ball when it's released.  (The robot hits the backboard every time.)

Any physicists reading who can deliver a more informed hypothesis?

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If a human can outperform a robot, then it must be that he does *something* better than the machine does.  What? 

My guess is: when the human shoots, he can notice if something's a little off, like the ball slips a bit.  In that case, he can adjust his motion on the spot to try to counter that.  The robot, of course, doesn't do that.

That's the only thing I can think of.  

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I'd love to hear other opinions, because I'm very, very surprised.  I would have bet good money that you could easily make a robot that shoots, say, 98 percent.  Could it really be that tiny differences caused by friction could make such a big difference in outcomes?