Design and Optimization of Linear Rotary Drilling Motor

In order to improve the drilling efficiency and accuracy of drilling robot, a linear rotary drilling motor (LRDM) is proposed with U-type stator and toroidal winding structure. The stator sections are staggered, which can use the motor space effectively. The asymmetric air gap flux density (AGFD) phenomenon of LRDM is found based on the initial magnetic field analysis by finite-element method (FEM). According to flux tube principle, the variation law of the amplitude of the asymmetric AGFD of the LRDM is derived, which can be used to realize the optimization design with less computation time. The cogging torque, detent force, torque, and thrust are taken as the optimization objectives, and the optimal values of the structure and electromagnetic parameters are obtained. Then a prototype is manufactured. The electromagnetic characteristics of the proposed motor are analyzed and verified by FEM and experimental test.