Magnetic Field Control for Haptic Display: System Design and Simulation

We present magnetic rendering, a new haptic display method applying an electromagnet array to produce magnetic field in mid-air where the force field can be felt as magnetic repulsive force exerted on the hand through the attached magnet disks. The magnetic field is generated by a specifically designed electromagnet array driven by direct current. By attaching small magnet disks on the hand, the tactile sensation can be perceived by the user. This method can provide a strong tactile force and avoid cumbersome attachments with wires, and thus, it is suitable for a colocated visual and haptic display. In this paper, we introduce the detailed design of the electromagnet array for haptic rendering purposes, which is modeled and tested using finite-element method simulations. We characterize the model mathematically, and apply recursive least squares adaptive control algorithm for controlling the magnetic field. We evaluate the performance of our simulated model in terms of force strength, operation distance, and force stiffness. We then implement and test the control algorithm, which results in fast and accurate convergence. We conclude with simulations on a 15-by-15 model to generate a haptic human face, which results in a smooth force field and accurate force exertion on the control points.