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Reinforcement Learning and SOFM

I'm actually just looking into RL for my bots. There's quite a bit to be done, especially for speeding up the learning. But as you said, it does have an impact on the performance, and you also notice some fairly erratic behaviour at first! This can be quite dangerous for a physical robot, but taking especial care when modelling the problem seems to do the trick...

One thing you might be interested in for learning feature maps, are Neural Gas Networks. They're quite popular at the moment, and rightly so! They can expand to match the dimensionality of your data, and refine and contract as more feedback is obtained from the environment. I'll see if I can find some links for you...

935 posts.
Monday 10 December, 08:36
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Hyper

For a physical robot its definately useful to have the outputs from whatever adaptive system is being used put through a checking routine to ensure that the desired servo positions won't cause the robot to be damaged.

The ability to have the feature space expand or contract depending on the dimensionality of the sensory input received by the robot would certainly be an advantage. One problem with using a SOM type system is that according to the classical algorithm the system gradually moves into an equilibrium state (learning rate and neighbourhood size gradually reducing at some fixed rate) until a solution of some sort is reached. Of course in the real world living systems never reach a state of equilibrium, but are instead in a continuous state of change. You could argue that the ultimate equilibrium state for a living system is death, but even in death biological systems are in a state of being degraded and eventually transformed into other types of organic matter or new forms of life.

I recently upgraded my PC from windoze ME to XP, and there does seem to be a dramatic improvement in the performance of the video cameras, to the point where the gains which I was using for motion tracking no longer work. With much faster video processing the robot appears to become hyperactive, with the servos perpetually overshooting and trying to compensate back. It's probably worth making the gains adjustable in the software so that it could potentially be run on different PCs.

- Bob

136 posts.
Monday 10 December, 14:24
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Upgrades

I'm surprised and impressed that the OS upgrade made such a difference!

I guess adding parameters to adjust the gain was a good idea anyway, but I'm sure there are plenty other things that you could do with the extra speed...

935 posts.
Wednesday 12 December, 05:49
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