Monthly Archives: October 2015

Setting up an arm simulation interface in Nengo 2

I got an email the other day asking about how to set up an arm controller in Nengo, where they had been working from the Spaun code to strip away things until they had just the motor portion left they could play with. I ended up putting together a quick script to get them started and thought I would share it here in case anyone else was interested. It’s kind of fun because it shows off some of the new GUI and node interfacing. Note that you’ll need nengo_gui version .15+ for this to work. In general I recommend getting the dev version installed, as it’s stable and updates are made all the time improving functionality.

Nengo 1.4 core was all written in Java, with Jython and Python scripting thrown in on top, and since then a lot of work has gone into the re-write of the entire code base for Nengo 2. Nengo 2 is now written in Python, all the scripting is in Python, and we have a kickass GUI and support for running neural simulations on CPUs, GPUs, and specialized neuromorphic hardware like SpiNNaKer. I super recommend checking it out if you’re at all interested in neural modelling, we’ve got a bunch of tutorials up and a very active support board to help with any questions or problems. You can find the simulator code for installation here: https://github.com/nengo/nengo and the GUI code here: https://github.com/nengo/nengo_gui, where you can also find installation instructions.

And once you have that up and running, to run an arm simulation you can download and run the following code I have up on my GitHub. When you pop it open at the top is a run_in_GUI boolean, which you can use to open the sim up in the GUI, if you set it to False then it will run in the Nengo simulator and once finished will pop up with some basic graphs. Shout out to Terry Stewart for putting together the arm-visualization. It’s a pretty slick little demo of the extensibility of the Nengo GUI, you can see the code for it all in the <code>arm_func</code> in the <code>nengo_arm.py</code> file.

As it’s set up right now, it uses a 2-link arm, but you can simply swap out the Arm.py file with whatever plant you want to control. And as for the neural model, there isn’t one implemented in here, it’s just a simple input node that runs through a neural population to apply torque to the two joints of the arm. But! It should be a good start for anyone looking to experiment with arm control in Nengo. Here’s what it looks like when you pull it up in the GUI (also note that the arm visualization only appears once you hit the play button!):

nengoarm

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