A Haptic interface with adjustable stiffness using MR fluid

This paper describes a combined tactile sensor and haptic interface that can change its stiffness using magnetorheological fluids (MR fluid). The tactile sensor consists of 6 distributed capacitive sensors that can sense the location and the amount of applied force. Above the sensors is a chamber filled with MR fluid. By changing the magnetic field, the hardness of the MR fluid, and thereby of the haptic interface, can be changed. Fast changes of the magnetization direction lead to a sensation of vibration. The resulting device can be used for novel haptic input devices or for robotic grippers. A prototype device has been constructed, and the effects of the varying magnetic field and the resulting varying stiffness of the MR fluid on the distributed force sensing with the capacitive sensors has been evaluated. We discovered that the measured forces vary very little with changes in the strength of the magnetic field.