Motor control solution on the truntable for computer vision and optics usage


I'm lack of electrical engineering knowledge, I'm just a software engineer, so I need your help on the turntable design and control problem.

I need a very accurate turntable to allow me to scan some objects with a DSLR camera, and I can use a computer vision based algorithm to properly digest the images.

Unfortunately my algorithm only works well on very accurate turntable. Each rotation must be exactly same, say the rotation precision should be around 0.01 degree.

The rotation is like every time it rotates 3 degree, then stop, allowing the camera take the photo, and repeat the rotation again, until some images are taken. Since the object I'm scanning is fragile, so the rotation speed is around 1 degree per second.

The potential design can be like the following graph and design .

enter image description here

So I'm asking a question that how can I control the turntable with computer precisely ? Do I really need an encoder to tell me the angle it reaches ? I wish to get the actual hardware type suggestion, and of course I wish the entire control module (without the computer) could be less than 1000 dollars.

Best Answer

I once used a spectrometer that was just a grating on a rotation stage. It had a worm gear drive and a stepper motor turning the worm gear. Given different worm gears and stepper motrs you can get very fine resolution. The problem is then repeatably. There is gear back lash which can be removed by always going in the same direction. And then finally you'll need a way to set a zero point. For the spectrometer this was done by observing the zeroth order reflection from the grating. You could do a similar optical thing. Or perhaps a mechanical limit switch. Once you have zero getting to any angle is just a matter of counting pulses into the stepper.