Abstract:
Relocation of haptic feedback from the fingertips to the wrist enables haptic interaction with virtual environments while leaving the fingers free for dexterous manipulation tasks. Human tactile perception is correlated with mechanoreceptor density in the skin and is therefore greater in the glabrous skin of the fingertips than elsewhere on the body, making the fingertips ideal for tactile interactions. However, haptic devices designed for enabling tactile interaction in virtual environments are often bulky and cumbersome, limiting the ability to perform fine motor tasks, such as dexterous manipulation, or directly manipulating physical objects. Devices mounted on the fingertips also hinder finger tracking during interaction with virtual or augmented reality environments by occluding optical trackers or occupying space for electromagnetic tracking elements. First, we developed a pair of wrist-worn tactile haptic devices and a virtual environment to study how various mappings between fingers and tactors affect task performance. The haptic feedback rendered to the wrist reflects the interaction forces occurring between a virtual object and virtual avatars controlled by the index finger and thumb. We performed a user study comparing four different finger-to-tactor haptic feedback mappings and one no-haptic-feedback condition as a control. We evaluated users’ ability to perform a simple pick-and-place task via the metrics of task completion time, path length of the fingers and virtual cube, and magnitudes of normal and shear forces at the fingertips. We found that multiple mappings were effective, and there was a greater impact when visual cues were limited. Next, we enabled relocation of finger interaction forces in a virtual environment is using soft, 3D-printed, pneumatic wrist-worn haptic devices called haptic voxels, or Hoxels, a soft, 3D-printed, pneumatically actuated wrist-worn haptic device that can apply skin deformation in up to 3-DoF. Hoxels can display up to 20 N of force normal to the skin. Due to off-board pumps and flexible pneumatic transmission lines, the worn mass of a pair of Hoxels is only 75 grams. Using the Hoxels, we performed a user study in which participants grasped and moved a cube in a virtual environment, with virtual interaction forces displayed to the wrist. We showed that dual-tactor and single-tactor relocated haptic feedback reduced grasp forces compared to no haptic feedback. This lays the foundation for multi-degree-of-freedom (DoF) feedback to the wrist, leaving the fingers unencumbered for mixed reality applications. Next, we performed a post-hoc blocked force characterization for the Hoxel and blocked force-torque characterization for the FingerPrint, a soft, 3D-printed, pneumatically actuated finger-worn haptic device that can apply skin deformation in up to 4-DoF. Our aim was to give physical significance to the duty cycle input used during the psychophysical study. Despite the intention to output unidirectional shear force and torque, we measured non-negligible off-axis components. We show the resulting 3-DoF vectors, which includes necessary normal forces, for each force or torque command. Finally, we conducted three parallel method of constant stimuli psychophysical studies to find the just noticeable difference of stimuli produced by soft pneumatically actuated devices at the index finger, thumb, and wrist. Additionally, we sought to quantify the difference along the phalanges of the fingers, the dorsal and ventral sides of the wrist, and between the multiple locations of the fingers and wrist. We discuss the measured force and torque range and accuracy from the characterization experiment and the measured just noticeable differences and Weber Fractions for the psychophysical studies. We also discuss the limitations of these studies and what insights in can be gathered and applied for designing soft wearable haptic devices and rendering schemes. This dissertation focuses on the design, perception, and effectiveness of wrist-based feedback for haptic interactions with virtual environments. We demonstrate that relocated feedback from the fingertips to the wrist can be effective at helping users modulate interaction forces applied to virtual objects during dexterous manipulation tasks. We also demonstrate that there is a quantifiable difference in the multi-DoF stimuli produced by soft wearable devices. This lays the groundwork for designing next-generation virtual environments augmented with relocated haptic feedback.
My Contributions
As the first author, I led the design and development of the virtual environment used in the study. I was responsible for designing the user study protocol, conducting data analysis, and creating visualizations to effectively communicate our findings.
Skills
Experiment Design, Scientific Writing, Data Analysis, Data Visualization, Virtual Reality, CHAI3D, 3D Printing, MATLAB
