Kato, FumihiroShi, MiaohuiKamishima, KaitoIwata, HiroyasuHasegawa, ShoichiSakata, NobuchikaSundstedt, Veronica2024-11-292024-11-292024978-3-03868-245-51727-530Xhttps://doi.org/10.2312/egve.20241368https://diglib.eg.org/handle/10.2312/egve20241368In this paper, we propose a vision-based haptic sensor (VHS) capable of acquiring force at the required speed for softness discrimination during palpation, along with a force measurement algorithm. Palpation requires the simultaneous acquisition of surface imagery from the affected area and haptic information, such as softness and surface texture. Additionally, the sensor must exhibit softness comparable to human skin to avoid causing discomfort to the patient. By designing a force sensor that tracks markers embedded in transparent gel using a camera, we enable the concurrent capture of visual and haptic data. An algorithm is also presented for calculating normal forces based on the extension of the markers' image plane. Accurate force modeling was achieved by training a normal force estimation model using an asymmetric stiffness coefficient matrix, which effectively mitigates cross-talk effects. Furthermore, the process was optimized by employing sparse search techniques with narrow marker search ranges between frames during high-speed imaging, enabling rapid detection of circular force markers and achieving force acquisition at 601.25 Hz. Compared to previous methods, the proposed approach offers higher measurement accuracy and speed within the force range required for palpation. It can measure at 500 Hz or higher, which is crucial for discriminating the five levels of softness important in dermatological palpation. Therefore, the proposed haptic sensor shows promise for use in robotic palpation.Attribution 4.0 International LicenseCCS Concepts: Human-centered computing → Haptic devicesHuman centered computing → Haptic devices10.2312/egve.202413688 pages