A haptic feedback device including a fluid viscosity-controlled brake that
outputs high forces to the device user at low cost while maintaining
inherent safety. An interface device includes a manipulandum physically
contacted by the user. A sensor senses a position of the manipulandum and
outputs a sensor signal. The interface device also includes a brake
including a field-controlled fluid having a viscosity that can be
controlled by controlling an electric current in a coil, where a
resistive force or drag on the manipulandum is controlled by controlling
the fluid's viscosity. The fluid can be an electrorheological fluid
controlled by an electric field or a magnetorheological fluid controlled
by a magnetic field. In one preferred embodiment, the resistive force is
controlled by adjusting a degree of contact of the brake with the
manipulandum based on the fluid's viscosity. Disclosed embodiments
include fishing devices, bicycle simulators, and control knobs.