Design of a Hemispherical Magnetic Levitationhaptic Interface

We are currently fabricating a haptic interface device to enable direct physical interaction with dynamic simulated three-dimensional environments by exerting and reacting to forces and motions between the user's hand and a magnetically levitated object. Our device uses magnetic levi-tation rather than a motorized linkage so that the dynamics are simple and actuator nonlinearities such as hystere-sis, backlash and static friction are eliminated. Magnetic levitation haptic interaction was previously demonstrated using a ne motion robot wrist. A new magnetic levita-tion device was then designed speciically to address the requirements of realistic tool-based haptic interaction. A hemispherical device shape was adopted to maximize the ranges of translation and rotation and the ratio of actua-tor surface area to the levitated mass while enabling the user to grip a tool handle at the hemisphere center, near the center of mass, where translation, rotation, force, and torque ranges are the same in all directions. The new device will have a motion range of at least 12 mm and 7 , position sensing resolution within 3 m, and will be capable of generating peak forces up to 60 N. Preliminary results from testing of position sensors and actuator assemblies support the performance data obtained from model analysis.