Using pot-magnets to enable stable and scalable electromagnetic tactile displays

We present the design, fabrication, characterization and psychophysical testing of a scalable haptic display based on electromagnetic (EM) actuators. The display consists of a 4x4 array of taxels, each of which can be in a raised or a lowered position, thus generating different static configurations. One of the most challenging aspects when designing densely-packed arrays of EM actuators is obtaining large actuation forces while simultaneously generating only weak interactions between neighboring taxels. In this work we introduce a lightweight and effective magnetic shielding architecture. The moving part of each taxel is a cylindrical permanent magnet embedded in a ferromagnetic pot, forming a pot-magnet. An array of planar microcoils attracts or repels each pot-magnet. This configuration reduces the interaction between neighboring magnets by more than one order of magnitude, while the coil/magnet interaction is only reduced by 10%. For 4 mm diameter pins on an 8 mm pitch, we obtained displacements of 0.55 mm and forces of 40 mN using 1.7 W. We measured the accuracy of human perception under two actuation configurations which differed in the force vs. displacement curve. We obtained 91% of correct answers in pulling configuration and 100% in pushing configuration

Optimization of the force and power consumption of a microfabricated magnetic actuator

The force (F) and the power consumption (P ) of a magnetic actuator are modeled, measured and optimized in the context of developing micro-actuators for large arrays, such as in portable tactile displays for the visually impaired. We present a novel analytical approach complemented with finite element simulation (FEM) and experiment validation, showing that the optimization process can be performed considering a single figure of merit. The magnetic actuator is a disc-shaped permanent magnet displaced by planar microcoil. Numerous design parameters are evaluated, including the width and separation of the coil traces, the trace thickness, number of turns and the maximum and minimum radius of the coil. We obtained experimental values ranging from 2 to 12 mN/ sqrt(W) using up to 2-layer coils of both microfabricated and commercial printed circuit board (PCB) technologies. This performance can be further improved by a factor of two by adopting a 6-layer technology. The method can be applied to a wide range of electromagnetic actuators

Morphing Tactile Display for Haptic Interaction in Vehicles

Conference of 9th International Conference on Haptics: Neuroscience, Devices, Modeling, and Applications, EuroHaptics 2014 ; Conference Date: 24 June 2014 Through 26 June 2014; Conference Code:110079International audienceThis work describes the design, fabrication and characterization of a morphing (actuated) tactile display based on an array of 32 electromagnetic actuators and a capacitive touch deformable layer. A two-stage locking device allows for reliable pattern creation when the users’ finger is placed on the interface. Taxel (tactile pixel) displacements up to 1.9 mm and a holding force of 1.25 N at 9 W electrical power have been measured. This device integrated in the centre console of vehicles is designed to work in combination with a LCD display mounted in the dashboard to control secondary vehicle systems