When I started working at eSolar, I was employed as a mechanical engineer. I was working on the heliostat design, at work, but could not help but bring my work home. I had a few ideas for a different kind of heliostat, so I made a quick table top prototype using just a laser cutter and a few hours in CAD. The result is this tilt-tilt heliostat design which has many advantages:
The drive is a cable drive, so the backlash (which plagues many heliostat designs) is vitually eliminated
The drive pulleys are large in diameter, so the forces induced by wind on the drive system are dramatically reduced
The mechanical singularity points are at the horizon, where they do not interfere with normal operation
The tilt-tilt kinematics allow for cheap, accelerometer based angle feedback in both axes