Any ideas what might be a good way to implement linear actuator matrix for such a project?
Here's how I would implement it - it's going to be expensive, no matter how you look at it (even your idea would be expensive in terms of overall time, if not money).
- For every pin, use a micro-servo that can rotate at least (or close to) 180 degrees.
- Attach to the output shaft of the micro-servo a grooved wheel or pulley with a circumference equal to 2x the distance you want the pins to be able to move.
- On each pulley, attach a length of large-gauge fishing line (or small steel cable, or some other stiff-but-thin line) to the outer edge of the pulley at one point, such that when the pulley moves, it can pull in or push out the line.
- Route the line using stiff but thin-walled plastic tubing (made of nylon or similar material - even lubricated thin-wall steel tubing could work) to each pin.
The servos will need to be mounted on a board away from the pin-sculpture, all bends in the tubing need to be fairly gradual (not sharp) to allow smooth movement and prevent binding.
To gain a better understanding of how this would look and work, check out how the cables that connect bicycle hand-brakes are worked and routed, as well as how the cables from an automobile's accelerator pedal are routed and control the air-flow mechanisms in a carburetor or intake of the engine.
I'm not sure I can describe this better than I have; it should suffice to say that you're going to have an extreme mess on your hands, no matter how you decide to implement it, simply because of the sheer number of components involved. The only way around the mess (well, lessening to an extend) would be to scale the size of the "pin board" to something much larger, so that you could mount the servos (or other mechanisms) behind the board and still have enough room to work. Your only other option would be to purchase or manufacture custom linear-motion mechanisms (with position feedback) in the quantity needed for the resolution of the display. Either option will either cost a ton of money (have you priced miniature linear actuators with position feedback lately?), or a ton of money and a ton of time and engineering expertise.
I guess ultimately, it will all depend on your budget, experience, space for the installation, and patience...