In the video it's being driven at 1/8th step. I'm considering switching to two servo motors and using a polar system.

The problem is I need it to also be fast enough to fee lag free for the artist.

You can get good 1/32 drivers like the DRV8825 (https://www.pololu.com/product/2133) for not too much - I'm pretty confident they'll be able to do what you need (You can buy knockoffs for even cheaper). Even 1/16 is pretty dang smooth.

It also might be that you're supplying too much or too little current to the motors - both will result in jerkiness and noise. If your current drivers are current limiting, I'd look into tuning that. If they aren't, the ones I linked are.

They are current limiting and can go down to 1/16 step I believe. However, even at the current settings the motors can't keep up if the artist whips their arm from one side to the other.

But why can't the artist do their work in real time and get feedback digitally from the monitor and you then playback their strokes at a later time to do all the rendering/plotting. I can see how they may like to use the plotter medium for their feedback but all the noise I would think would be distracting.

That's definitely something we're working on. To be honest it's not very hard. I'd just modify the capture script to capture pen and pressure input and turn it into vectors, instead of capturing movement from the robot like it is now.

The problem though is that the actual brush strokes are different from a brush stroke generated in Photoshop. Controlling the machine lets them see the final output in real time, so they can paint it more like a real physical painting, and then the robot can reproduce the physical painting.

I think in the next demo it'll be more evident the difference between lines on the computer and physically rendered brush strokes.

Aha, yes in the prototyping stage that sort of immediate feedback would prove useful to converge upon the modeling necessary to properly translate the brush stroke pressure from the tablet into accurate saturation on the canvas. My comment was assuming that sort of translation was in place, but if you're discovering it then they would have to train the device. Which is an interesting thing, maybe apply machine learning to train the device much like how Andrew Ng and team trained that helicopter to fly upside down.

Also I tried to design this based on real-life applications. Digital artwork is never designed to be produced physically, and physical artwork is done physically with real-time feedback loop from observing the brushwork and colors.

That being said, turning digital artwork into physical is still an interesting problem domain since artists can't be expected to all come wield my machine. I'd like an artist to be able to remotely work the machine in some manner.

Yea I saw that stepper motor driver. It's $229, which is more than it cost to build this whole machine.