VERY interesting idea!
Thank you...I learned years ago to never just "accept" the norm, but to always question it. Sometimes coming from a problem from a different direction yields a different, sometimes better (often worse) solution.
One revolution of the cam would make the head move it's whole travel so unless you use a gearbox your resolution would be poor.
Again, I guess it depends on your intentions. If it's not to implement a 3D function, but only to implement "pen up" or "pen down," then the cam might be the simplest possible solution.
Just off the top of my head I Think you would have positioning trouble because the cam is not liner.
You're right...the cam would not have a linear response. It would be controlled by a formula that I'm not in the mood to integrate... My calculus is rusty.
As to having a linear response, if the cam was designed right, it could be made linear. The "lifter" (can't really call it a cam anymore) would have to be a spiral form, rather than an offset disc, but still quite simple to make. Basically just an inclined plane wrapped around a central axis.
Another way to do it would be to implement it in software, but since resolution is a fixed value dependent on the hardware itself, that's probably not the best solution.
Yet another way would be to use some sort of optical feedback, probably scrounged from a modern optical mouse, but now we're adding real complexity. The idea was to keep it as simple as is possible. KISS.
-- Chuck Knight  |