Magnet-Coil Role-Switching Real-Time Wrench Model for Magnetic Levitated Motors With Extendable Motion Range

Magnetic levitation motors are broadly employed for haptic devices and precision manufacturing. The motor developed in this study comprises a disc-magnet mover and stating square coils. Such actuators are commonly controlled using lookup tables, which require large amounts of memory and time-consuming offline preparation. To accurately calculate the system wrench in real time, a novel wrench model is proposed by considering the disc magnet and the square coils as thin-walled solenoid and multiple stacked magnets, respectively. The Gauss–Legendre quadrature and magnetic surface charge approach are utilized to numerically estimate the Lorentz force and torque. The role-switching model computes the wrench matrix between a single disc magnet and nine coils in 96.5 $\boldsymbol{\mu}$s via parallel computing. Considering the system current limits, the weighted pseudoinverse is incorporated for commutation to further extend the motion range. The model accuracy is evaluated and verified through the Frobenius norm and load cell measurements. The experimental results show that the motion resolutions are $\boldsymbol{\pm}$10 $\boldsymbol{\mu}$m and $\boldsymbol{\pm}$0.02${}^{\circ}$ in the translational and rotational axes, respectively. The trajectory tracking results show that the magnetic levitation motor can translate the mover across the platform with a 380 mm side length limited only by the platform geometry, and the mover can be levitated up to a noticeably large air gap of 65 mm and rotated up to an extensive range of $\boldsymbol{\pm}$45${}^{\circ}$.