Design and Analysis of a Novel Axial-Flux Slotless Limited-Angle Torque Motor With Trapezoidal Cross Section for the Stator

This paper presents a novel limited-angle torque motor as a modified double-sided slotless axial-flux permanent-magnet motor (DSAPM) with a trapezoidal cross section for the stator. A new approach to the magnetic equivalent circuit and semi-three-dimensional (3-D) analytical armature reaction field modeling for the proposed actuator are derived and implemented in the design process. Designing is done based on avoidance of saturation at maximum torque production to prevent distortion of torque characteristic in short-time operations. Next, finite-element analysis is utilized to confirm the accuracy of the design equations and to compare the proposed actuator with conventional industrial limited-angle torque motors and the conventional DSAPM structure. Finally, the proposed actuator is prototyped and its experimental results are presented and discussed. Finite-element analysis and experimental data show better accuracy of the model, electromagnetic capability improvements by this new structure and excellent applicability of the proposed rotary actuator.