This study proposes a novel handheld vibrotactile display (T-hive) to provide a human operator with spatial and directional information. The proposed design is composed of a spherical knob with a vibrotactile surface and a moving base that allows 6-DOF motion. To isolate vibrotactile stimuli provided by multiple actuators, the spherical knob is divided into 13 vibrotactile modules. Each vibrotactile module consists of a vibration motor, a patch of spherical surface, and a vibration isolator. By coordinating the vibrotactile modules, the vibrotactile display delivers spatial and directional information based on phantom sensation and sensory saltation. Through experiments, we evaluated the effectiveness of the spatial and directional information perceived on the palm and fingers of the operator's hand. The experimental results confirm that vibrotactile feedback is useful for object control by providing intuitive information.

Thermal cues provide information about the thermal properties of an object held in the hand. These cues can be simulated in a thermal display and used to assist in identifying the object. Two experiments were conducted using a thermal display that simulated the cues associated with contact with different materials. The thermal contact model was based on a semi-infinite body model that included thermal contact resistance and blood perfusion. Its performance was evaluated in two experiments, the first of which involved discriminating between simulated materials, and in the second, subjects were required to identify simulated materials based on the thermal cues presented to one, three, or five fingers. The results from the first experiment indicated that when the temperature profile associated with contact with a real material is presented to the finger, subjects can use this cue to discriminate between simulated materials. Their performance on this task is comparable to that achieved with real materials with similar thermal properties. In the second experiment, the accuracy with which subjects identified a simulated material based on thermal cues improved as the number of fingers stimulated increased, suggesting that spatial summation of cold occurs when the area stimulated is noncontiguous. However, most of the improvement in identifying materials occurred when the display presented thermal cues to three as compared to one finger, with little further enhancement in performance when five fingers were stimulated. These results indicate that thermal displays can be used effectively to present information about the material composition of objects in virtual environments.