Passive Viscous Haptic Textures

We describe the use of eddy current brakes for the synthesis haptic textures. Textural effects are achieved through rapid variations of the viscous damping coefficient that these brakes create when activated. We demonstrate that eddy current brakes can be actuated reliably at frequencies typical of haptic texture rendering. Performance is evaluated by measuring the movement of the manipulandum with an accelerometer while modulating the viscous force at high frequency. Key advantages of this technique include guaranteed passivity of the haptic synthesis, accurate results from the linear dynamics of these brakes, and elimination of the need to estimate or observe velocity.