Master of Science, Miami University, 2023, Mechanical Engineering

Available devices with smaller touchscreen displays (TSDs) offer users adequate haptic feedback, whereas larger TSDs still lack meaningful tactile sensations. This study is focused on rendering vibrotactile feedback on large TSDs. Existing methods for localized vibrotactile rendering on large TSDs use many actuators. Practically, using many actuators is not desirable due to space constraints, power supply limitations, etc., for consumer-centric large TSD devices. Therefore, this study investigates localized vibrotactile feedback on large TSDs using a restricted number of electrostatic resonant actuators (ERAs). Using flexible boundary conditions combined with multi-frequency excitation, a novel method is presented to render localized vibrotactile feedback for two types of large TSDs: a narrow touch bar and a rectangular touch surface. A method for managing/positioning localized haptic feedback on large TSDs is also investigated. In-house finite-element-based simulation models of TSDs are developed along with experimental prototypes for verifying the vibrotactile performance. The modeling and analysis strategy presented here is general and can be extended for haptic rendering methods of different touch surfaces, actuators, and boundary conditions. Finally, model-based parametric studies are presented for better design considerations and improved vibrotactile intensity.

Committee: Kumar Singh (Advisor); Jeong-Hoi Koo (Advisor); James Chagdes (Committee Member) Subjects: Electrical Engineering; Engineering; Mechanical Engineering

Master of Science, Miami University, 2021, Mechanical and Manufacturing Engineering

Vibrotactile feedback is a key feature of many small touchscreen devices, but is often absent or incomplete in large touchscreen displays due to a lack of suitable actuators for such applications. Thus, a growing need exists for haptic actuators capable of producing meaningful feedback in large touch displays. This study proposes and evaluates a dual-electrode electrostatic resonant actuator (ERA) as a means to fulfill such a need. The dual-electrode ERA was compared to a similar singleelectrode ERA to study the effect of electrode configuration. It produced a maximum vibration 73% higher than the single-electrode actuator, showing promising potential for its use in large touchscreen applications. To study the ERA in a large display application, a prototype touch bar system with spring boundaries was designed, fabricated, and evaluated. By varying the number of actuators excited in the system, the actuators' magnitude, excitation frequency, and signal duration, a maximum vibration of 4 g-forces could be achieved throughout the majority of the display in both sustained and pulse sensations. This demonstrates a promising potential for generating a freely positionable and fully controllable point of vibrotactile stimulation at any point of a touch bar display. These results show the feasibility of the actuator spring boundary implementation and the dual-electrode ERA for large touchscreen display applications.

Committee: Jeong-Hoi Koo (Advisor); Tae-Heon Yang (Committee Member); James Chagdes (Committee Member) Subjects: Mechanical Engineering

Master of Science in Electrical Engineering (MSEE), Wright State University, 2023, Electrical Engineering

Stochastic resonance (SR) is a phenomenon that can enhance the detection or transmission of weak signals by adding random noise to a non-linear system. SR introduced into the human motor control system as a subthreshold mechanical vibration has shown promise to improve sensitivity to haptic feedback. SR can be valuable in a laparoscopic surgery application, where haptic feedback is critical. This research sought to find if applying SR to the human motor control system improves performance in a laparoscopic probing task, if the performance differs based on the location of stochastic resonance application, and if there are sustained effects from SR after its removal. Subjects were asked to perform a palpation task using a laparoscopic probe to determine whether a series of simulated tissue samples contained a tumor. Subjects in the treatment groups were presented with a series of samples under the following conditions: Pre-SR, SR applied to the forearm or elbow, and Post-SR. Subjects in the control group did not have SR applied at any point. Performance was measured through the accuracy of tissue assessment, subjects' confidence in their assessment, and assessment time. Data from 27 subjects were analyzed to investigate the application of stochastic resonance and its sustained effects to improve haptic feedback sensitivity in a simulated laparoscopic task. The forearm group was shown to have significant improvement in the accuracy of tissue identification and sensitivity to haptic feedback with the application of SR. Additionally, the forearm group showed a greater improvement in accuracy and sensitivity than the elbow group. Finally, after SR was removed, the forearm group showed sustained significant improvement in accuracy and sensitivity. Therefore, the experiment results supported the hypotheses that stochastic resonance improves subjects' performance and haptic perception, that performance improvement differs based on application location, and that subjec (open full item for complete abstract)

Committee: Luther Palmer III, Ph.D. (Advisor); Caroline Cao Ph.D. (Committee Member); Katherine Lin M.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Engineering; Health; Health Care; Mechanical Engineering; Surgery

Master of Science, Miami University, 2019, Mechanical and Manufacturing Engineering

Realistic haptic feedback is necessary to provide meaningful touch information to users of numerous technologies, such as virtual reality, mobile devices and robotics. For a device to convey realistic haptic feedback, two touch sensations must be present: tactile feedback and kinesthetic feedback. Tactile feedback is felt at the surface of one's skin and displays textures and vibrations, whereas kinesthetic feedback is felt in one's joints and muscles and transmits position and movement information. While many devices today display tactile feedback through vibrations, most neglect to incorporate kinesthetic feedback due to size constraints. To provide comprehensive feedback, this study investigates a new haptic device based on an unconventional actuation method: electrorheological (ER) fluid, a smart fluid with tunable yield stress under the application of electric field. The device's control electronics and structural components are integrated into a compact printed circuit board, resulting in a slim device suitable for mobile applications. By controlling the ER fluid flow via applied electric fields, the device can generate a wide and distinct range of both tactile and kinesthetic sensations. These sensations were derived analytically from ER fluid's governing equations as well as experimentally. The device may be used as a haptic interface between a user and virtual environment.

Committee: Jeong-Hoi Koo Ph.D. (Advisor); Tae-Heon Yang Ph.D. (Committee Member); Michael Bailey Van Kuren Ph.D. (Committee Member) Subjects: Computer Engineering; Materials Science; Mechanical Engineering