Design and Experimental Analysis of a Selfbearing Double-Stator Linear-Rotary Actuator

Linear-rotary actuators (LiRAs) are today used in industry applications where a controlled linear and rotary motion is necessary such as pick-and-place robots, servo actuation of gearboxes or tooling machines. However, in special industry applications that require high purity and/or high precision positioning, the usage of conventional LiRAs with mechanical bearings is limited. Therefore, in this paper a LiRA with integrated magnetic bearings, i.e. a selfbearing/bearingless LiRA, is analyzed. The actuator employs concentrically arranged linear and rotary stators placed inside and outside a cylindrically shaped mover, which results in a so-called selfbearing double-stator (SBDS) LiRA. A FEM geometry optimization of the SBDS LiRA is performed and Pareto performance plots concerning linear force and torque generation are obtained. A SBDS LiRA hardware demonstrator and an 18-phase inverter power supply hardware prototype are built and their operation is experimentally verified by rotary and linear position step response measurements.