A Direct-Drive Rotary-Linear Machine with Dual-PM Flux Modulation for 2-DOF Kinematic Device

Multiple degree-of-freedom motion mechanisms are increasingly integrated in transportation electrification equipment. This article presents a novel direct-drive rotary-linear machine (RLM) that is suitable for two-degree-of-freedom (2-DOF) kinematic devices. This highly integrated machine, with its dual-permanent magnetic (PM) flux modulation structure, possesses enhanced torque and force density. Instead of the commonly adopted nondirect-drive structure of dual rotary motors combined with the ball screw, the proposed RLM will produce direct-drive rotary-linear motion. In particular, the design mitigates the mutual interference of magnetic fields in two different directions. The innovative structure enables the motor to rotate, move linearly, or perform helical movement throughout the whole stroke. The electromagnetic performance of the dual-PM RLM in different states is evaluated and compared with the existing RLM. A prototype has been produced as the test sample. The experimental results verify the validity of the proposed dual-PM RLM design for 2-DOF motion.