This study proposes a methodology to deliver contact information on construction robots to the remote operator by transmitting measured collision vibrations, which are often beyond the human-perceivable range. We focus on the human capacity to discriminate the envelope of high-frequency vibrations as an essential cue to perceive contact materials and collision conditions. The proposed method preserves the envelope shapes with amplitude-modulated waves with a single carrier frequency in the human sensitive range. In the preliminary experiments, a miniature shovel digging experiment confirmed that the proposed method improves the discriminability of the contact materials and sliding velocities. A psychophysical experiment also showed that the participants could discriminate the envelope differences irrespective of the carrier frequency. The proposed method was applied to the tactile transmission system for a construction robot developed in the ImPACT program. A vibration sensor was attached on the robot arm, and the vibrotactile feedback was applied to the operator's wrist. Performance evaluations under a delicate teleoperated task (insertion of a bar into bricks) showed that the peak force was reduced by the proposed method significantly for two out of the three participants. The results show that our proposal could improve the maneuverability of teleoperation.

Humans can judge the hardness of an object by tapping its surface using a fingertip. The damped natural vibration caused by tapping is a vibrotactile cue for hardness perception. We investigated how dynamic characteristics of an object or vibration influence the hardness perceived by tapping. Using multivariate analyses, the subjectively reported hardness was linked with the dynamic stiffness of an object. Dynamic stiffness, which characterizes the impulsive response of an object, was acquired across 40-1,000 Hz for fourteen types of material cuboid through a hammering test. These blocks were also ranked by seven participants based on their hardness perceived when the participants tapped them with a finger. It was found that the dynamic stiffness did not equally affect the hardness perception across the wide frequency range. Its sensitivity displayed a peak around 200-400 Hz and decreased or disappeared at greater frequency bands in which human perceptual capability is limited.

A high-resolution haptic display that reproduces tactile distribution information on the contact surface between a finger and an object realizes the presentation of the softness of the object and the magnitude and direction of the applied force. In this paper, we developed a 32-channel suction haptic display that can reproduce tactile distribution on fingertips with high resolution. The device is wearable, compact, and lightweight, thanks to the absence of actuators on the finger. A FE analysis of the skin deformation confirmed that the suction stimulus interfered less with adjacent stimuli in the skin than when pressing with positive pressure, thus allowing more precise control of local tactile stimuli. The optimal layout with the least error was selected from three configurations dividing 62 suction holes into 32 ports. The suction pressures were determined by calculating the pressure distribution by a real-time finite element simulation of the contact between the elastic object and the rigid finger. A discrimination experiment of softness with different Young's modulus and its JND investigation suggested that the higher resolution of the suction display improved the performance of the softness presentation compared to a 16-channel suction display previously developed by the authors.

Haptic feedback enables material perceptionviaremote robotics. Both force and vibration information are essential for haptic feedback, and it is important to understand their applicability in different situations. In this study, the relationship between the effective type of haptic feedback and target properties in robot-mediated material discrimination was investigated. A remote-control system including a force presentation device and a wearable vibrotactile display was constructed. In the first experiment, the discrimination performance of material hardness was compared between two types of feedback, force and hybrid (vibrotactile and force) conditions. The results show that both feedback systems allow statistically-significant discrimination of the stimuli, and a significant difference in correct-answer rates between the two feedback conditions was not observed. This indicates that the force system was effective for hardness discrimination, and that there was no superimposed effect of the hybrid system. In the second experiment, the discrimination performance of material roughness was compared between three types of feedback (force, vibrotactile, and hybrid). The results indicate that the rate of correct responses for hybrid feedback condition are significantly higher than those for the force condition. This suggests that hybrid feedback is effective for roughness discrimination. Therefore, the effective type of feedback depends on the properties of target materials, and the superimposed effect of hybrid feedback was only observed in roughness discrimination. These findings play an important role in selecting the best feedback method for a given situation or constructing multiple feedback methods that achieve high discrimination performance.

Temporal dominance of sensations (TDS) methods are used to record temporally developing sensations while eating food samples. Results of TDS tasks are typically discussed using averages across multiple trials and panels, and few methods have been developed to analyze differences between individual trials. We defined a similarity index between two time-series responses of TDS tasks. This index adopts a dynamic level to determine the importance of the timing of attribute selection. With a small dynamic level, the index focuses on the duration for attributes to be selected rather than on the timing of the attribute selection. With a large dynamic level, the index focuses on the temporal similarity between two TDS tasks. We performed an outlier analysis based on the developed similarity index using the results of TDS tasks performed in an earlier study. Certain samples were categorized as outliers irrespective of the dynamic level, whereas the categorization of a few samples depended on the level. The similarity index developed in this study achieved individual analyses of TDS tasks, including outlier detection, and adds new analysis techniques to TDS methods.

This paper presents a novel experimental case study in which tactile sensation is analyzed as 4-dimensional subjective data consisting of stimulus, participant, evaluation term, and temporal components, using a temporal measurement approach. Specifically, the skin and lotion interaction was evaluated using the Temporal Check-All-That-Apply (TCATA) method. Two practical analysis examples were conducted to experimentally demonstrate the potential use cases of time-series subjective tactile data. In the first example, stimulus classification accuracy was compared between different sampling periods, including the whole and late periods, with the latter being akin to the conventional Semantic Differential (SD) method condition. The results indicate that the whole and early periods exhibit higher accuracy compared to the latest period, implying that temporal measurements may capture more stimulus characteristics than the conventional approach. In the second example, cluster analysis based on the time-series subjective data was conducted. The results revealed that the participants were classified into two distinct clusters, with the trends of time-series changes being significantly different between the clusters.