Two-Degree-of-Freedom WPT System Using Cylindrical-Joint Structure for Applications With Movable Parts

A new winding structure for wireless power transfer (WPT) systems is proposed. The transmitter (Tx) and receiver (Rx) coils are wound on a semicylindrical and cylindrical structures, respectively. Thus, the Rx coil has two degree-offreedom (2-DoF) movements. The first is linear (Delta) movement along the axial direction of the joint. The second is angular (alpha) movement around the axial direction of the joint, while transferring power. Winding methods and design procedures are discussed in detail. A prototype was built to validate the proposed idea. Experiment results have confirmed that the proposed structure achieved a constant power transfer efficiency (PTE) under linear movement. In addition, the Rx coil rotated up to 85 degrees and maintained low variations of the efficiency, where PTE decreased by 4.61% for rotation between 0 degrees and 85 degrees. Moreover, the proposed WPT coils maintained a constant PTE under dynamic conditions. The proposed winding structure could be a good technique for applications that require linear and angular movements.