Need an extremely accurate and fast rack and pinion system? Linear move too long for a ball screw? Check out Nexen’s RPS system. RPS stands for Roller Pinion System. The pinion has spring loaded rollers that keep 3 teeth (actually rollers) engaged in the rack continuously. Racks can be linked in line for long travel.
The RPS is nifty but you need to rotational motion? Nexen has RPS “gears” and a slew ring setup for that.