Coil configuration design for the Lorentz force maximization by the topology optimization method: applications to optical pickup coil design

Coil design is an important problem in magnetic circuit design, so various optimization methods have been used to find optimal coils. The objective of this research is to develop a method optimizing the coil configuration for the maximum Lorentz force in a given direction, and the minimum Lorentz forces and torques in other directions. Our idea to achieve this goal is to formulate the design problem as a coil topology optimization problem. Unlike the existing application of the topology optimization method in coil design which involves a fixed-direction current density field only, the proposed topology optimization approach is so formulated as to deal with varying current density magnitudes and directions that should be taken into account for the Lorentz force maximization problem. For the formulation, coils are modeled as conductors and their conductivities are chosen as design variables. As specific problems, the design optimization of fine-pattern tracking and focusing coils of an optical pickup actuator is considered.