Comments on: CMU's BallBot – Scientific Advancement or Just-Another-Robot? http://www.robotshop.com/gorobotics/the-news/science/cmus-ballbot-scientific-advancement-or-just-another-robot How to Make a Robot | Robotics Projects & News Fri, 25 May 2012 16:12:35 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Theo (Ted) http://www.robotshop.com/gorobotics/the-news/science/cmus-ballbot-scientific-advancement-or-just-another-robot/comment-page-1#comment-75 Theo (Ted) Tue, 10 Jun 2008 01:16:46 +0000 http://www.robotshop.com/gorobotics/wordpress/?p=113#comment-75 Well, they do do a little bit of science in the design of their LQR controller. They build a simple model of the system and show that their controller is a valid controller for a system modeled as such. The experimentally-tuned PI controller was just added afterwards to get rid of some frictional effects. (the "I" is the important part; it serves as an internal model that deals with the frictional damping by accumulating extra control energy) However, none of this is cutting edge control science. A truly sophisticated handling of this robot would include an input (what they built was purely for stabilization/regulation; it is not meant to track an input) and build an appropriate nonlinear controller. (note: for an inverted pendulum like this, the nonlinearities aren't that great. Gravity adds a sinusoid function, which is globally Lipschitz and looks pretty darn linear when you're very close to the equilibrium; thus, this problem isn't even sufficiently nonlinear to be interesting) So some real science was done here... But it was classroom science. There was no contribution. Nothing *new* is being done here. Well, they do do a little bit of science in the design of their LQR controller. They build a simple model of the system and show that their controller is a valid controller for a system modeled as such. The experimentally-tuned PI controller was just added afterwards to get rid of some frictional effects. (the “I” is the important part; it serves as an internal model that deals with the frictional damping by accumulating extra control energy)

However, none of this is cutting edge control science. A truly sophisticated handling of this robot would include an input (what they built was purely for stabilization/regulation; it is not meant to track an input) and build an appropriate nonlinear controller. (note: for an inverted pendulum like this, the nonlinearities aren’t that great. Gravity adds a sinusoid function, which is globally Lipschitz and looks pretty darn linear when you’re very close to the equilibrium; thus, this problem isn’t even sufficiently nonlinear to be interesting)

So some real science was done here… But it was classroom science. There was no contribution. Nothing *new* is being done here.

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