A novel two-degree-of-freedom tactile display reproduces the sensations of sliding contact and incipient slip through the rotation of a ball positioned under the user's fingertip. A pair of motor-driven wheels actuates the ball via contact friction. Mechanical performance requirements are used to define the dimensions and construction method of the device. Kinematic analysis shows that the drive wheel angles and their contact locations with the ball must be carefully selected in order to accurately control the axis of rotation and speed of the ball. However, psychophysical experiments indicate that some kinematic error is tolerable; errors of up to 20° in slip angle and 30% of a nominal velocity may be applied without detection from an average user. The lightweight, modular tactile display was attached to a multi-degree-of-freedom kinesthetic interface and used to display virtual environments with slip. Experimental results demonstrate that users complete a virtual paper manipulation task with lower applied forces using combined slip and force feedback in comparison with conventional force feedback alone.

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Many high-degree-of-freedom haptic devices and teleoperator systems either do not have grippers or do not provide force feedback in the gripper degree of freedom (DOF). The purpose of this work is to determine the effect of gripper force feedback in relation to Cartesian (translational) force feedback on the execution of telemanipulation tasks. We developed a system for adding an additional DOF of grip force feedback on a 3-DOF Phantom haptic device master, as well as 6-DOF force/torque sensing on each "finger" of a coupled gripper on a Phantom haptic device slave. The internal (grip) and external (translational) forces were measured as users performed a soft peg-in-hole task with various DOFs of force feedback: (1) full force feedback, (2) translational force feedback only, (3) grip force feedback only, and (4) no force feedback. Results show that the level of force applied in the translational and gripping DOFs are decoupled for a 3-DOF telemanipulator with added grip force feedback. This is likely due to the decoupled dynamics of internal and external hand forces.