A Study of Spatial Perception in Virtual Space via Display and the Intervention Effects of Haptic Feedback

Okada K., Matsui K., Atsuumi K., et al. A Study of Spatial Perception in Virtual Space via Display and the Intervention Effects of Haptic Feedback. IEEE Access 12, 90124 (2024); https://doi.org/10.1109/ACCESS.2024.3420724.In recent years, technologies for presenting users with virtual spaces have been rapidly developing. Some applications allow users to observe three-dimensional spaces via screens and influence those virtual spaces using certain devices. In such cases, it is necessary not only to rely on the presentation of depth information but also to adapt to depth in the virtual space to completely execute tasks. In this study, we investigated the spatial perception characteristics of commonly used two-dimensional (2D) displays and advanced spatial reality (SR) displays with spatial presentation capabilities. The research participants performed tasks of tracing a trajectory on a wall surface that changes angles in a three-dimensional virtual space. In addition, we examined the effect of haptic feedback intervention on spatial perception during task execution and its persistence. For 2D displays, we realized that haptic feedback improves task accuracy and that the effect persists even after the feedback is removed. However, this applied only to tasks under feedback conditions, and no broad effect on spatial perception was observed. By contrast, for SR displays, we realized that haptic feedback may have a detrimental effect on spatial perception. Moreover, we quantitatively proved that the use of SR displays improves spatial perception accuracy compared with 2D displays and that the relationship between the line of sight and display angle is critical for spatial perception. In conclusion, the following two points are inferred from this study. (1) To improve spatial perception, it is necessary to consider methods that directly intervene in the body schema and the peripersonal space in the future. (2) Feedback by multiple modalities is not necessarily effective in presenting information on virtual space and obtaining spatial perception

Development of fully automated manufacturing equipment for conductive Nylon thread actuators and evaluation of their characteristics

The nylon thread actuator, a type of super coiled polymer actuator, proposed by Haines et al. in 2014 has many useful advantages, including its relatively high power, lightweight, and low cost. Although the fabrication process seems simple, to fabricate such actuators, we must do so by hand because the finished products are not currently for sale. Thus, we are developing fully automated manufacturing equipment for overtwisted-type actuators using Ag-coated sewing machine nylon threads. In this study, we depict the details of a prototype machine and the basic specifications of conductive nylon thread actuators through experiments. This machine has three stepper motors. We found the maximum recommended drive speed of each spindle: the twist spindle with the drive is approximately 32.8 [rad/s] (313 [rpm]), the feeder speed is 37 [mm/min], and the winding speed is 61 [mm/min]. This condition provides steady overtwisted patterns with simply open-loop control, and the measured tension is approximately 20-30 [cN] during twisting, whereas it is approximately 40-50 [cN] during annealing. These processes run continuously for a single long thread; thus, the overall throughput is equal to the winding speed, which is determined by both the desired annealing tension and time

Pilot study of the relation between various dynamics of avatar experience and perceptual characteristics

In recent years, due to the prevalence of virtual reality (VR) and human-computer interaction (HCI) research, along with the expectation that understanding the process of establishing sense of ownership, sense of agency, and limb heaviness (in this study, limb heaviness is replaced with comfort level) will contribute to the development of various medical rehabilitation, various studies have been actively conducted in these fields. Previous studies have indicated that each perceptual characteristics decrease in response to positive delay. However, it is still unclear how each perceptual characteristic changes in response to negative delay. Therefore, the purpose of this study was to deduce how changes occur in the perceptual characteristics when certain settings are manipulated using the avatar developed in this study. This study conducted experiments using an avatar system developed for this research that uses electromyography as the interface. Two separate experiments involved twelve participants: a preliminary experiment and a main experiment. As observed in the previous study, it was confirmed that each perceptual characteristics decreased for positive delay. In addition, the range of the preliminary experiment was insufficient for the purpose of this study, which was to confirm the perceptual characteristics for negative delay, thus confirming the validity of conducting this experiment. Meanwhile, the main experiment showed that the sense of ownership, sense of agency, and comfort level decreased gradually as delay time decreased, (i.e., this event is prior to action with intention, which could not be examined in the previous study). This suggests that control by the brain-machine interface is difficult to use when it is too fast. In addition, the distribution of the most strongly perceived settings in human perceptual characteristics was wider in regions with larger delays, suggesting this may lead to the evaluation of an internal model believed to exist in the human cerebellum. The avatar developed for this study may have the potential to create a new experimental paradigm for perceptual characteristics

Earable Ω (OMEGA): A Novel Clenching Interface Using Ear Canal Sensing for Human Metacarpophalangeal Joint Control by Functional Electrical Stimulation

(1) Background: A mouth-free interface is required for functional electrical stimulation (FES) in people with spinal cord injuries. We developed a novel system for clenching the human metacarpophalangeal (MP) joint using an earphone-type ear canal movement sensor. Experiments to control joint angle and joint stiffness were performed using the developed system. (2) Methods: The proposed FES used an equilibrium point control signal and stiffness control signal: electrical agonist–antagonist ratio and electrical agonist–antagonist sum. An angle sensor was used to acquire the joint angle, and system identification was utilized to measure joint stiffness using the external force of a robot arm. Each experiment included six and five subjects, respectively. (3) Results: While the joint angle could be controlled well by clenching with some hysteresis and delay in three subjects, it could not be controlled relatively well after hyperextension in the other subjects, which revealed a calibration problem and a change in the characteristics of the human MP joint caused by hyperextension. The joint stiffness increased with the clenching amplitude in five subjects. In addition, the results indicated that viscosity can be controlled. (4) Conclusions: The developed system can control joint angle and stiffness. In future research, we will develop a method to show that this system can control the equilibrium point and stiffness simultaneously