arXiv subjects

Yoshihiro Nakata

Publications and source records attributed to Yoshihiro Nakata.

4 recordsLinked to original sources

arXiv2026

SHAPE: Simultaneous Water Hydraulic Actuation and Position Estimation of a Sensorless Remote Actuator through a Thin and Long Flexible Tube

Robot sensors and electronic equipment are prone to failure in harsh environments. With water hydraulic drive, thin and long tubes enable remote operation without actuator-side sensors. Furthermore, the elasticity of the tubes reduces the impedance of the joints (actuators), benefiting robot tasks involving unexpected contact with the environment or vibrations. However, owing to the low impedance and limited camera visibility, accurately positioning the joint (or end effector) to the target location under varying load conditions is challenging. This study proposes a novel method that employs water-filled flexible tubes to enable the transmission of driving power and actuator-side information to and from the actuator, respectively, without actuator-side sensors. By modeling volumetric loss during transmission based on pressure fluctuations and incorporating minor air entrapment, simultaneous power transmission and position estimation is achieved through a tube up to 50 m. Thus, it becomes possible to use a feedback control framework that was previously difficult to implement in sensorless systems. Experimental validation confirms stable position control of a sensorless water hydraulic cylinder under varying loads. Furthermore, a field parameter-identification method accounts for tube and air entrainment variability without requiring actuator-side sensors. These contributions promote reliable remote control of robots in harsh environments.

cs.RO↗

arXiv2026

Cybernetic Android Avatar "Yui": System Integration, Field Deployment, and Evaluation

Remote communication technologies have become widely used; however, supporting a sense of shared physical space and conveying rich non-verbal cues remain challenging in many social interaction scenarios. This study presents "Yui," a full-body cybernetic android avatar designed to integrate operator-side immersive teleoperation with interlocutor-side human-like social signaling. Yui combines a 55-degrees of freedom full-body mechanism with a previously developed android head, facial expression and gaze control, upper-body and arm motion, hand actuation, and a mobile platform. It can be operated through either the immersive mode using a head mounted display-based interface or desktop mode using a webcam-based interface. We evaluated the system through three real-world deployments: a long-term public exhibition at Expo 2025 in Osaka, Kansai, Japan; a remote educational exchange between elementary school students; and a public interaction study with general participants. During the Expo deployment, two units accumulated approximately 1131 h of operation, demonstrating both operational feasibility and maintenance challenges. In the public study, both operators and interlocutors reported positive impressions of co-presence and willingness to use the system. Interlocutors also rated the avatar positively in terms of human likeness and the transmission of emotions and intentions. The results indicate usability for general operators while suggesting room for improvement in precise controllability. These findings provide field-derived evidence and design implications for socially deployable full-body android avatars.

cs.RO↗

arXiv2025

MOFU: Development of a MOrphing Fluffy Unit with Expansion and Contraction Capabilities and Evaluation of the Animacy of Its Movements

Robots designed for therapy and social interaction aim to evoke a sense of animacy in humans. While many studies have focused on life like appearance or joint based movements, the effect of whole body volume changing movements commonly observed in living organisms has received little attention. In this study, we developed MOFU MOrphing Fluffy Unit, a mobile robot capable of whole body expansion and contraction using a single motor enclosed in a fluffy exterior. MOFU employs a Jitterbug geometric transformation mechanism that enables smooth diameter changes from approximately 210 mm to 280 mm with a single actuator, and is equipped with a differential two wheel drive mechanism for locomotion. We conducted an online survey using videos of MOFU behaviors and evaluated perceived animacy using the Godspeed Questionnaire Series. First, we compared stationary conditions with and without expansion contraction and with and without rotational motion. Both expansion contraction and rotation independently increased perceived animacy. Second, we examined whether presenting two MOFUs simultaneously would further enhance animacy perception, but no significant difference was observed. Exploratory analyses were also conducted across four dual robot motion conditions. Third, when expansion contraction was combined with locomotion, animacy ratings were higher than for locomotion alone. These results suggest that whole body volume changing movements enhance perceived animacy in robots, indicating that physical volume change is an important design element for future social and therapeutic robots.

cs.RO↗

arXiv2023

Development of the Lifelike Head Unit for a Humanoid Cybernetic Avatar `Yui' and Its Operation Interface

In the context of avatar-mediated communication, it is crucial for the face-to-face interlocutor to sense the operator's presence and emotions via the avatar. Although androids resembling humans have been developed to convey presence through appearance and movement, few studies have prioritized deepening the communication experience for both operator and interlocutor using android robot as an avatar. Addressing this gap, we introduce the ``Cybernetic Avatar `Yui','' featuring a human-like head unit with 28 degrees of freedom, capable of expressing gaze, facial emotions, and speech-related mouth movements. Through an eye-tracking unit in a Head-Mounted Display (HMD) and degrees of freedom on both eyes of Yui, operators can control the avatar's gaze naturally. Additionally, microphones embedded in Yui's ears allow operators to hear surrounding sounds in three dimensions, enabling them to discern the direction of calls based solely on auditory information. An HMD's face-tracking unit synchronizes the avatar's facial movements with those of the operator. This immersive interface, coupled with Yui's human-like appearance, enables real-time emotion transmission and communication, enhancing the sense of presence for both parties. Our experiments demonstrate Yui's facial expression capabilities, and validate the system's efficacy through teleoperation trials, suggesting potential advancements in avatar technology.

cs.RO↗