Named the flexible ultrasonic motor (FUSM), [Yunosuke Sato] built on top of their work and assembled a pair of FUSM into a closed-loop actuator with motion control in two dimensions.

Each of these gantries is driven by closed-loop servo motors and fancy ball screws, producing a total build volume of 77″x30″x20″. This open air version is printing in PLA.

Toshiba: A three-phase brushless motor driver IC "TC78B025FTG" with a rotation speed control (closed loop control) function for small fans. (Photo: Business Wire) ...