Elsevier BV Acta Medica Okayama 2590-1230 27 2025 Inscribed-type spherical speed reducer with uniform reduction ratio in all directions 106742 EN Seiya Naramura Faculty of Environmental, Life, Natural Science and Technology, Okayama University Koichi Tonegawa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University So Shimooka Faculty of Environmental, Life, Natural Science and Technology, Okayama University Tomoaki Yano Faculty of Environmental, Life, Natural Science and Technology, Okayama University Akio Gofuku Okayama Prefectural University Nagayoshi Kasashima National Institute of Advanced Industrial Science and Technology Tetsushi Kamegawa Faculty of Environmental, Life, Natural Science and Technology, Okayama University A spherical motor is an actuator that can generate rotational motion about all three orthogonal axes. However, it is difficult to obtain high output torque from most electromagnetic spherical motors, primarily due to limitations inherent in electromagnetic actuators, such as restricted magnetic force and thermal constraints. Since its torque cannot be increased using planar gears, spherical speed reducers that transmit rotational torque along three orthogonal axes through sphere-to-sphere contact are required. One major limitation of conventional spherical speed reducers is that their size increases significantly as the reduction ratio becomes higher. To address this issue, we propose a novel inscribed-type spherical speed reducer, in which the deceleration mechanism is integrated within the output sphere. This configuration enables a more compact design, reducing the overall size to approximately half that of conventional designs. To predict the angular velocity and transmitted torque, theoretical models for the rotation and torque transmission of the speed reducer were developed. According to the proposed model, the reduction ratio of the spherical speed reducer is 1/3. To verify the validity of these models, experiments were conducted to measure angular velocity and torque. The theoretical results agreed well with the experimental results. In addition, the theoretical torque exhibited an average relative error of 1.63 % compared to the experimental result. Therefore, it was confirmed that the rotation and torque transmission models were valid. These results demonstrate that a reduction ratio can be obtained in all directions of the 3-DOF of the spherical speed reducer, unlike conventional 1-DOF reducers. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0924-4247 390 2025 Extension-type flexible pneumatic actuator with a large extension force using a cross-link mechanism based on pantographs 116594 EN So Shimooka Faculty of Environmental, Life, Natural Science and Technology, Okayama University Kazuma Tadachi Mechanical and Systems Engineering Program, School of Engineering, Okayama University Tetsushi Kamegawa Faculty of Environmental, Life, Natural Science and Technology, Okayama University In this study, we propose an extension-type flexible pneumatic actuator (EFPA) with a high extension force and no buckling. In a previous study, soft actuators that extended in the axial direction by applying a supply pressure were unable to generate the extension’s pushing force because the actuators buckled owing to their high flexibility. To generate a pushing force, the circumferential stiffness of an extension-type flexible soft actuator must be reinforced. Therefore, a cross-linked EFPA (CL-EFPA) was developed, inspired by a pantograph that restrains the EFPA three-dimensionally using the proposed link mechanism. The proposed CL-EFPA consists of three EFPAs and a cross-linking mechanism for integrating each EFPA circumference. The pushing force of the CL-EFPA is approximately 3.0 times compared with that generated by the previous EFPA with plates to restrain its plane. To perform various bending motions, attitude control was performed using an analytical model and a system that included valves, sensors, and controllers. No potential conflict of interest relevant to this article was reported.

Fuji Technology Press Ltd. Acta Medica Okayama 1883-8049 37 1 2025 Fan-Shaped Pneumatic Soft Actuator that Can Operate Bending Motion for Ankle-Joint Rehabilitation Device 43 53 EN So Shimooka Faculty of Environmental, Life, Natural Science and Technology, Okayama University Hirosato Yokoya Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Masanori Hamada Department of Rehabilitation Medicine, Okayama University Hospital Shun Shiomi Department of Rehabilitation Medicine, Okayama University Hospital Takenori Uehara Department of Orthopaedic Surgery, NHO Okayama Medical Center Takahiro Hirayama Department of Emergency, Critical Care and Disaster Medicine, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Tetsushi Kamegawa Faculty of Environmental, Life, Natural Science and Technology, Okayama University Nowadays, owing to declining birthrates and an aging population, patients and the elderly requiring rehabilitation are not getting enough physical activity. In addressing this issue, devices for rehabilitating them have been researched and developed. However, rehabilitation devices are almost exclusively used for patients who can get up, rather than those who are bedridden. In this study, we aim to develop a rehabilitation device that can provide passive exercise for bedridden patients. The ankle joint was selected as the target joint because the patients who have undergone surgery for cerebrovascular disease remain bedridden, and early recovery in the acute stage is highly desirable. We proposed and tested a fan-shaped pneumatic soft actuator (FPSA) that can expand and bend stably at angles when supply pressure is applied as an actuator for a rehabilitation device to encourage patient exercise. However, the previous FPSA’s movement deviates from the arch of the foot owing to increased supply pressure. In the ideal case, FPSA should push the arch of the foot in an arc motion. This study proposes and tests the FPSA that can operate a bending motion to provide passive exercise to the ankle joint using tensile springs and a winding mechanism powered by a servo motor. The proposed FPSA has a significant advantage of exhibiting no hysteresis in its pressure-displacement characteristics. The configuration and static analytical model of the improved FPSA are described. No potential conflict of interest relevant to this article was reported.

Fuji Technology Press Ltd. Acta Medica Okayama 1883-8049 35 1 2023 Development of Automatic Inspection Systems for WRS2020 Plant Disaster Prevention Challenge Using Image Processing 65 73 EN Yuya Shimizu Okayama University Tetsushi Kamegawa Okayama University Yongdong Wang Okayama University Hajime Tamura Okayama University Taiga Teshima Okayama University Sota Nakano Okayama University Yuki Tada Okayama University Daiki Nakano Okayama University Yuichi Sasaki Okayama University Taiga Sekito Okayama University Keisuke Utsumi Okayama University Rai Nagao Okayama University Mizuki Semba Okayama University In this article, an approach used for the inspection tasks in the WRS2020 Plant Disaster Prevention Challenge is explained. The tasks were categorized into three categories: reading pressure gauges, inspecting rust on a tank, and inspecting cracks in a tank. For reading pressure gauges, the “you only look once” algorithm was used to focus on a specific pressure gauge and check the pressure gauge range strings on the gauge using optical character recognition algorithm. Finally, a previously learned classifier was used to read the values shown in the gauge. For rust inspection, image processes were used to focus on a target plate that may be rusted for rust detection. In particular, it was necessary to report the rust area and distribution type. Thus, the pixel ratio and grouping of rust were used to count the rust. The approach for crack inspection was similar to that for rust. The target plate was focused on first, and then the length of the crack was measured using image processing. Its width was not measured but was calculated using the crack area and length. For each system developed to approach each task, the results of the preliminary experiment and those of WRS2020 are shown. Finally, the approaches are summarized, and planned future work is discussed. No potential conflict of interest relevant to this article was reported.

Frontiers Media Acta Medica Okayama 2296-9144 10 2023 Parameter search of a CPG network using a genetic algorithm for a snake robot with tactile sensors moving on a soft floor 1138019 EN Hajime Tamura Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Tetsushi Kamegawa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University When a snake robot explores a collapsed house as a rescue robot, it needs to move through various obstacles, some of which may be made of soft materials, such as mattresses. In this study, we call mattress-like environment as a soft floor, which deforms when some force is added to it. We focused on the central pattern generator (CPG) network as a control for the snake robot to propel itself on the soft floor and constructed a CPG network that feeds back contact information between the robot and the floor. A genetic algorithm was used to determine the parameters of the CPG network suitable for the soft floor. To verify the obtained parameters, comparative simulations were conducted using the parameters obtained for the soft and hard floor, and the parameters were confirmed to be appropriate for each environment. By observing the difference in snake robot's propulsion depending on the presence or absence of the tactile sensor feedback signal, we confirmed the effectiveness of the tactile sensor considered in the parameter search. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1424-8220 22 22 2022 Realization of Crowded Pipes Climbing Locomotion of Snake Robot Using Hybrid Force-Position Control Method 9016 EN Yongdong Wang Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Tetsushi Kamegawa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University The movement capabilities of snake robots allow them to be applied in a variety of applications. We realized a snake robot climbing in crowded pipes. In this paper, we implement a sinusoidal curve control method that allows the snake robot to move faster. The control method is composed of a hybrid force-position controller that allows the snake robot to move more stably. We conducted experiments to confirm the effectiveness of the proposed method. The experimental results show that the proposed method is stable and effective compared to the previous control method that we had implemented in the snake robot. No potential conflict of interest relevant to this article was reported.

Springer Acta Medica Okayama 0938-7994 30 3 2019 Robotic CT-guided out-of-plane needle insertion: comparison of angle accuracy with manual insertion in phantom and measurement of distance accuracy in animals 1342 1349 EN Toshiyuki Komaki Department of Radiology, Okayama University Medical School Takao Hiraki Department of Radiology, Okayama University Medical School Tetsushi Kamegawa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University Takayuki Matsuno Graduate School of Natural Science and Technology, Okayama University Jun Sakurai Center for Innovative Clinical Medicine, Okayama University Hospital Ryutaro Matsuura Graduate School of Health Sciences, Okayama University Medical School Takuya Yamaguchi Division of Radiology, Department of Medical Technology, Okayama University Hospital Takanori Sasaki Collaborative Research Center for OMIC, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences Toshiharu Mitsuhashi Center for Innovative Clinical Medicine, Okayama University Hospital Soichiro Okamoto Department of Radiology, Okayama University Medical School Mayu Uka Department of Radiology, Okayama University Medical School Yusuke Matsui Department of Radiology, Okayama University Medical School Toshihiro Iguchi Department of Radiology, Okayama University Medical School Hideo Gobara Division of Medical Informatics, Okayama University Hospital Susumu Kanazawa Department of Radiology, Okayama University Medical School Objectives</br> To evaluate the accuracy of robotic CT-guided out-of-plane needle insertion in phantom and animal experiments.</br> Methods</br> A robotic system (Zerobot), developed at our institution, was used for needle insertion. In the phantom experiment, 12 robotic needle insertions into a phantom at various angles in the XY and YZ planes were performed, and the same insertions were manually performed freehand, as well as guided by a smartphone application (SmartPuncture). Angle errors were compared between the robotic and smartphone-guided manual insertions using Student’s t test. In the animal experiment, 6 robotic out-of-plane needle insertions toward targets of 1.0 mm in diameter placed in the kidneys and hip muscles of swine were performed, each with and without adjustment of needle orientation based on reconstructed CT images during insertion. Distance accuracy was calculated as the distance between the needle tip and the target center.</br> Results</br> In the phantom experiment, the mean angle errors of the robotic, freehand manual, and smartphone-guided manual insertions were 0.4°, 7.0°, and 3.7° in the XY plane and 0.6°, 6.3°, and 0.6° in the YZ plane, respectively. Robotic insertions in the XY plane were significantly (p < 0.001) more accurate than smartphone-guided insertions. In the animal experiment, the overall mean distance accuracy of robotic insertions with and without adjustment of needle orientation was 2.5 mm and 5.0 mm, respectively.</br> Conclusion</br> Robotic CT-guided out-of-plane needle insertions were more accurate than smartphone-guided manual insertions in the phantom and were also accurate in the in vivo procedure, particularly with adjustment during insertion. No potential conflict of interest relevant to this article was reported.

TAYLOR & FRANCIS Acta Medica Okayama 0169-1864 2019 Development of a separable search-and-rescue robot composed of a mobile robot and a snake robot EN Tetsushi Kamegawa Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Taichi Akiyama Graduate School of Natural Science and Technology, Okayama University Satoshi Sakai Graduate School of Natural Science and Technology, Okayama University Kento Fujii Graduate School of Natural Science and Technology, Okayama University Kazushi Une Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Eitou Ou Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Yuto Matsumura Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Toru Kishutani Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Eiji Nose Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Yusuke Yoshizaki Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Akio Gofuku Graduate School of Interdisciplinary Science and Engineering in Health Systems, Okayama University, In this study, we propose a new robot system consisting of a mobile robot and a snake robot. The system works not only as a mobile manipulator but also as a multi-agent system by using the snake robot's ability to separate from the mobile robot. Initially, the snake robot is mounted on the mobile robot in the carrying mode. When an operator uses the snake robot as a manipulator, the robot changes to the manipulator mode. The operator can detach the snake robot from the mobile robot and command the snake robot to conduct lateral rolling motions. In this paper, we present the details of our robot and its performance in the World Robot Summit. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1 2003 Extended QDSEGA for Controlling Real Robot : Acquisition of Locomotion Patterns for Snake : like Robot 791 796 EN Kazuyuki Ito Tetsushi Kamegawa Fumitoshi Matsuno <p>Reinforcement learning is very effective for robot learning. It is because it does not need prior knowledge and has higher capability of reactive and adaptive behaviors. In our previous works, we proposed new reinforce learning algorithm: &quot;Q-learning with dynamic structuring of exploration space based on genetic algorithm (QDSEGA)&quot;. It is designed for complicated systems with large action-state space like a robot with many redundant degrees of freedom. However the application of QDSEGA is restricted to static systems. A snake-like robot has many redundant degrees of freedom and the dynamics of the system are very important to complete the locomotion task. So application of usual reinforcement learning is very difficult. In this paper, we extend layered structure of QDSEGA so that it becomes possible to apply it to real robots that have complexities and dynamics. We apply it to acquisition of locomotion pattern of the snake-like robot and demonstrate the effectiveness and the validity of QDSEGA with the extended layered structure by simulation and experiment. </p> No potential conflict of interest relevant to this article was reported.