Development of Virtual Three-Dimensional Tactile Display Based on Electromagnetic Localization.

This dissertation describes the development of an assist-device aimed to deliver 3D graphic information to the visually impaired people. A human-in-loop approach was used to analyze whether a virtual 3D shape can be transferred correctly to the human users. The proposed device consists of two major parts: (a) A system of position sensors for real time localization based on magnetization, and (b) A single vibratory actuator working at varied frequencies based on its real time location. The error bound of the position measurement was tested to be 2 mm, which defined the machine resolution of the shape display. In order to realize the refresh rate of the localization that can follow user's scanning speed, the parallel data processing sequences for computer and microcontroller were designed. Additionally, vibratory electromagnetic (EM) actuators were discussed based on eddy current and permanent magnet methods. The simulation study showed that eddy current method was not applicable for millimeter size coil. Accordingly, the permanent magnet method was developed and the force detection threshold of human tactile perceptions was studied. Virtual shape perception experiments were made with participation of 3 volunteers who were not aware of the 3D shape information prior to the tests. Based on the four sets of shape tests, we conclude that the majority of the shape information is able to be delivered to users by using the proposed device. Difficulties for perceiving the local sharp profile e.g. thin plates and large curvature in small shapes may be better addressed by multiple actuators simultaneously providing shape information in the local boundary detection. The major contribution of this dissertation is the 3D shape display implemented by a miniature and low cost device. The developed device utilizes both passive stimulation and active search so that a commonly used large scale actuators matrix based on mere active touch method is avoided. The studies on the required force/energy input from the actuator showed that EM actuators can be miniaturized to millimeter scale without sacrificing the ability to induce tactile stimulation. Additional uniqueness of the proposed system is the ability to present hollow features, which is impossible to display by the existing devices.