Journal of Robotics and Mechatronics
Online ISSN : 1883-8049
Print ISSN : 0915-3942
ISSN-L : 0915-3942
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Special Issue on Fluid Powered System and its Application
  • Masahiro Takaiwa, Toshiro Noritsugu, Hideyuki Tsukagoshi, Kazuhisa Ito ...
    Type: Editorial
    2020 Volume 32 Issue 5 Pages 853
    Published: October 20, 2020
    Released: October 20, 2020
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    It is well known that fluid-powered systems are used practically in almost all industrial fields, including construction, manufacturing, transportation, among others.

    Nowadays, the rapid growth in the development of the mechanical elements in fluid-powered systems, such as control valves, actuators, and sensors, and the rapid growth in control strategies have given rise to pioneering in some novel application fields in ways that were thought to be impossible a decade ago. High-precision positioning control using the compressible fluid of pneumatic driving systems and multi-legged robots equipped with standalone hydraulic components are simple examples. Moreover, soft robotics based on fluid-powered technologies has attracted attention not only in academia but also in human support fields, which will become more important as Japan’s society ages.

    This special issue on “Fluid Powered System and its Application” includes one review paper and 22 other interesting papers related to the state of the art in the development of mechanical elements, total drive systems, motion control theory, and concrete applications of fluid-powered systems.

    We thank all of the authors and reviewers of the papers and hope this special issue helps readers to develop fluid powered systems that will contribute to developments in the academia and industry.

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  • Koichi Suzumori
    Type: Review
    2020 Volume 32 Issue 5 Pages 854-862
    Published: October 20, 2020
    Released: October 20, 2020
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    The history of robotics began with fluid power around 1960, at which time, all robots were driven by pneumatic or hydraulic actuators. Subsequently, in the mid-1980s, electromagnetic motors replaced the mainstay of robot actuators, while fluid-powered robots almost completely disappeared. However, in recent years, by utilizing the unique features of flexibility and lightness of pneumatics and the high power and robustness of hydraulics, several robots with unique characteristics, which cannot be realized with conventional electrical motors, are being developed. The author has developed various types of new fluid power actuators, including pneumatic and hydraulic types, to realize novel robots with unique features. This paper reviews the author’s previous works on fluid power actuators and robots driven by them. Furthermore, it presents prospective robots that can be realized using fluid power.

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  • Seigo Kimura, Ryuji Suzuki, Katsuki Machida, Rie Nishihama, Manabu Oku ...
    Type: Paper
    2020 Volume 32 Issue 5 Pages 863-875
    Published: October 20, 2020
    Released: October 20, 2020
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    In recent years, the burden per worker has increased due to a decrease in the working population. Wearable assist suits have been developed as one of the methods for solving the problem. To extend the assist suit to practical situations, it is necessary to provide a motion judgment interface for judging the motion of a wearer. Therefore, in our study, a motion judgment algorithm is proposed for assist suits, based on variable viscoelasticity. The proposed algorithm judges sitting, standing-up, stance, sitting-down, and gait using only the joint angle information of the suit and verification is performed using human joint angles obtained by motion capture. Thus, the motion judgment rate is 90% or more for sitting, standing-up, stance, and sitting-down, and 80% or more for gait, confirming the usefulness of motion judgment. Additionally, based on these results, further verification is performed on an actual machine. As a result, in a series of motions starting from the sitting to the standing-up, the stance, and the gait, the motion judgement is successful five times from the sitting to the standing-up, the stance, and once in gait. In a series of motions from sitting to standing-up, the stance, and sitting-down, the motion judgment is successful five times during sitting; five times during sitting, stance, and sitting-down; and three times during standing-up. In this way, it is confirmed that the proposed method can judge the motion only by angle information, although there is a problem in a success rate depending on the motion.

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  • Seiji Hijikata, Kazuhisa Ito, Hubertus Murrenhoff
    Type: Paper
    2020 Volume 32 Issue 5 Pages 876-884
    Published: October 20, 2020
    Released: October 20, 2020
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    An open center system (OC-System), which is one of the major hydraulic architectures for excavators, has been improved in the world to reduce fuel consumption for global environment conservation and lower operating costs. However, the total system efficiency, including the internal combustion engine (ICE), has not been thoroughly considered. In contrast, a constant pressure system (CP-System) enabling the engine to be driven optimally is developed, but is not accepted in the industry owing to the complexity of the required components. Thus, in this research, a hybrid system combining an OC-System with a CP-System is proposed to improve the total system efficiency. An accumulator, which is used to provide flow rate to actuators, is essential for the new hybrid system, and it is vital to consider the nominal gas volume and pressure level for the accumulator in terms of energy savings and initial cost. Therefore, the influences of accumulator volume and pressure level are discussed in this paper.

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  • Naoki Saito, Daisuke Furukawa, Toshiyuki Satoh, Norihiko Saga
    Type: Paper
    2020 Volume 32 Issue 5 Pages 885-893
    Published: October 20, 2020
    Released: October 20, 2020
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    This paper describes a semi-crouching assistive device using pneumatic artificial muscles. The goal of this device is to reduce the load on the lower back when performing work in the semi-crouching position. The load on the lower back is reduced by decreasing the compressive pressure on the lumbar disk of the lower back. This compressive pressure increases as the contraction force of the erector spine increases. Therefore, it is important to reduce the muscle activity of the erector spine. Based on the analytical result of a worker’s position model, the proposed device adopts a scheme to push the chest of the user as an appropriate assistive method. Additionally, the analytical result shows that a reduction in weight of the device is also important for decreasing the load on the lower back. Based on these results, we prototyped a lightweight semi-crouching assistive device that can generate sufficient assistive force via a pneumatic artificial muscle, which has high power to weight ratio. This device was experimentally evaluated via electromyogram of the erector spine when the user maintains a semi-crouching position. The experimental results confirmed the usefulness of this device.

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  • Nobutsuna Endo, Yuta Kizaki, Norihiro Kamamichi
    Type: Paper
    2020 Volume 32 Issue 5 Pages 894-902
    Published: October 20, 2020
    Released: October 20, 2020
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    There are not many physical models of oral and laryngeal systems for human speech movement in both computer simulators and mechanical simulators. In particular, there is no robot tongue mechanism that completely reproduces the deformation motion of the human tongue. The human tongue is an aggregate of muscles devoid of a skeleton. It only possesses a small hyoid. The purpose of this study is to develop a flexible actuator without a rigid link, aiming at the development of a tongue mechanism for a mechanical speech robot. We propose a flexible pneumatic bending actuator using thin McKibben muscles and a soft body formed by a silicone resin. We have verified its mechanical characteristics and described a control method for displacement and curvature. The elasticity/compliance of the silicone resin forming the soft body of this actuator was quantified by tensile tests. The oscillation parameters were identified, and it is suggested that the dynamic model can be described by a spring-mass-damper system. Assuming an arc-shaped deformation model, a simultaneous control system for the arc length and curvature was constructed and its effectiveness was confirmed.

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  • Takahiro Kosaki, Yuta Kawahara, Shigang Li
    Type: Paper
    2020 Volume 32 Issue 5 Pages 903-910
    Published: October 20, 2020
    Released: October 20, 2020
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    We describe a sliding mode controller design for an artificial rubber muscle driven by tap-water pressure. The hysteretic characteristics of this water-hydraulic artificial rubber muscle (WARM) often deteriorate its control accuracy. To cope with this complicated hysteresis, a modeling approach based on the least squares support vector machine (LS-SVM) with nonlinear kernel functions is first applied to a WARM. By employing this LS-SVM-based WARM model, a sliding mode controller is then derived for the WARM drive system. We verify the control performance of the proposed controller and compare its tracking accuracy with our previously developed controller through experiments.

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  • Mitsuo Komagata, Tianyi Ko, Ko Yamamoto, Yoshihiko Nakamura
    Type: Paper
    2020 Volume 32 Issue 5 Pages 911-922
    Published: October 20, 2020
    Released: October 20, 2020
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    Actuation systems for robots and other machines used in critical applications is an area that requires further research. In such applications, a machine works in a human environment and physically interacts with humans. Reliability and backdrivability are still insufficient in current systems. An electro-hydrostatic actuator has the potential advantage of high reliability by nature and high backdrivability in mechanical simplexity when it is designed to be small and light. This study provides a theoretical investigation of the methods for evaluating internal leaks and other mechanical losses, such as Coulomb and viscous friction, and experimentally evaluates two types (trochoid and involute gear) of prototyped hydraulic pumps.

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  • Kotaro Nishikawa, Kentaro Hirata, Masahiro Takaiwa
    Type: Paper
    2020 Volume 32 Issue 5 Pages 923-930
    Published: October 20, 2020
    Released: October 20, 2020
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    Industrial robots equipped with various grippers have been introduced in production sites and most of them are electrically driven. Because of the electric actuator’s characteristics, they have no back drivability, making it difficult for them to grasp flexible objects. In this study, therefore, we propose a pneumatically driven robot hand capable of grasping flexible objects by effectively employing the compressibility and back drivability of air.

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  • Wei-Hang Tian, Cian-Cheng Jhan, Misaki Inokuma, Tetsuya Akagi, Shujiro ...
    Type: Paper
    2020 Volume 32 Issue 5 Pages 931-938
    Published: October 20, 2020
    Released: October 20, 2020
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    Based on aging Japanese society, there has been a strong desire for development of rehabilitation devices that patients can use at home. The purpose of this study is to develop a home-based compact, lightweight, flexible, and safe rehabilitation device. In this study, a flexible robot arm for wrist rehabilitation that can be used, while patients hold the top of the robot arm, is proposed and tested. The proposed robot arm consists of three extension type flexible pneumatic actuators (EFPAs) restrained by 22 PET sheets. To achieve suitable bending stiffness of the robot arm, three EFPAs are restrained so as to form a tetrahedral shape. The robot arm can bend toward each radial direction. In this paper, the construction and operational principles of the tested robot arm are described. Additionally, the analytical model of the robot arm for attitude control is also described. In addition, the tracking control using the robot arm for the desired orbit is performed. As a result, the tested robot arm can trace the desired orbit based on the model. It is confirmed that the robot arm has the possibility for application as a wrist rehabilitation device for patients.

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  • Yumeta Seki, Yu Kuwajima, Hiroki Shigemune, Yuhei Yamada, Shingo Maeda
    Type: Paper
    2020 Volume 32 Issue 5 Pages 939-946
    Published: October 20, 2020
    Released: October 20, 2020
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    Soft robots have great potential to realize machines that interact and coexist with humans. A key technology to realize soft robots is soft fluidic actuators. Previously, we developed a soft pump using the electrohydrodynamics (EHD) phenomenon. EHD is a flow phenomenon, which is generated by applying a high voltage to a dielectric fluid. In this study, we developed flexible high-power-density EHD pumps. First, a pump was fabricated by a simple design with interdigitated electrodes. Second, a mathematical model was used to analyze the pressure generated per length assuming that electric fields only act between neighboring electrodes in a flexible EHD pump with interdigitated electrodes. The results were used to optimize the gap between electrodes to maximize the pressure per length. Third, we used the optimized process to fabricate multiple flexible EHD pumps. The procedure produced pumps easily and reliably. Fourth, we compared the experimental values with the analytical solutions. The good agreement confirmed that the generated pressure per unit length can be approximated in a uniform electric field between neighboring electrodes. Because our flexible EHD pump can operate even when deformed, it has potential for wearable device applications.

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  • Yasuhiro Hayakawa, Yuta Kimata, Keisuke Kida
    Type: Paper
    2020 Volume 32 Issue 5 Pages 947-957
    Published: October 20, 2020
    Released: October 20, 2020
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    In Japan, accidents involving the falling of elderly people are increasingly becoming a problem. To solve this problem, walking training is effective for preventing falls of elderly people. In this study, a walking training system was developed in which high-performance shoes are used to improve the efficiency of walking training. The high-performance shoes have three functions: 1) measurement of plantar pressure using changes in the inner pressure of the insole, 2) leg movement measurement using a six-axis motion sensor, and 3) applying stimulus to the sole of the foot by changing the shape of the insole. A unique rubber element was developed for these functions. Furthermore, a system to predict the behavior of patients during walking training was developed. Based on experimental results, four types of behavior of patients during walking training were predicted. Moreover, leave-one-person-out cross validation was performed by the random forest (RF) machine-learning algorithm, and the F-measure was calculated. As a result, the four types of behavior were classified with an F-measure of 78.6%.

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  • Junya Tanaka, Nobuto Matsuhira
    Type: Paper
    2020 Volume 32 Issue 5 Pages 958-976
    Published: October 20, 2020
    Released: October 20, 2020
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    We propose a robotic finger with an exoskeleton-type structure that bends and extends by the deformation force of flat tubes. Our objective is to realize a disposable robot hand for gripping unsanitary objects. To reduce the cost of disposing of the robotic finger, a commercially available cable carrier chain was used for the exoskeleton component, and the flat tubes used in the pneumatic actuator were prepared by thermal processing of a commercially available tube. The driving joint of the robotic finger consists of a hollow link mechanism and two flat tubes, which are respectively arranged inside the hollow link mechanism and at the joint boundary. The proposed joint structure achieves both smooth drivability and good load-bearing capacity. The developed robotic finger weighs approximately 85 g and generates a fingertip force of approximately 4 N when a pressure of 0.25 MPa is applied. Because the developed robotic finger is pneumatically driven, it conforms to the object shape and is compliant to external force. Verification of the mechanism demonstrated that the developed robotic finger is useful because it was able to grasp six types of assumed objects.

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  • Jumpei Kawasaki, Yuki Nakamura, Yasukazu Sato
    Type: Paper
    2020 Volume 32 Issue 5 Pages 977-983
    Published: October 20, 2020
    Released: October 20, 2020
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    Generally, the magnetic field applied to a magnetorheological fluid (MRF) is generated by electromagnets. Electromagnets consume electric power during MRF magnetization, which is an issue. In this study, we examine two kinds of magnetizing mechanism using a permanent magnet, instead of electromagnets, to save electric power and generate a magnetic field on the MRF. One mechanism linearly moves the permanent magnet into the magnetic circuit composed of yokes. The magnetic field intensity on the MRF is then controlled by changing the overlap between the magnet and the yokes. The other mechanism rotates a permanent magnet in the magnetic circuit. The magnetic field intensity on the MRF is then controlled by changing the relative angular position between the magnet and the yokes. These two mechanisms normally generate force or torque on the magnet toward a magnetically stable position concerning the magnet, and the force or torque causes power consumption to hold and move the magnet. We design herein special magnetic circuits and a cancelation mechanism for the force or torque that drastically reduce the power consumption during the MRF magnetization compared with an electromagnet-type magnetizing device.

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  • Ha Tham Phan, Seiya Itagaki, Yasukazu Sato
    Type: Paper
    2020 Volume 32 Issue 5 Pages 984-993
    Published: October 20, 2020
    Released: October 20, 2020
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    A switched reluctance motor (SRM) generates a reluctance torque without the power of a permanent magnet, rendering it a candidate for rare-earth free motors. Compared with a permanent magnet synchronous motor (PMSM), SRMs also offer operational advantage in high-temperature environments owing to their robust structure. However, SRMs are generally inferior to PMSMs in terms of torque ripple, noise, and speed control, in particular. Therefore, this study attempts to improve the controllability of SRMs by proposing an SRM driving method in the form of a bidirectional rotation torque and a speed-controllable servomotor. The advantage of this method is evaluated experimentally using a closed-loop hydraulic system (valveless control system), which includes a hydraulic pump driven by an SRM to supply hydraulic power to actuators. The results show that the pump flow rate and hydraulic motor speed are consistent with the sinusoidal commands corresponding to the forward and reverse rotations of the SRM.

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  • Kazushi Sanada
    Type: Paper
    2020 Volume 32 Issue 5 Pages 994-999
    Published: October 20, 2020
    Released: October 20, 2020
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    A laminar flowmeter that estimates the unsteady flowrate in a pipe using a Kalman filter is proposed. The laminar flowmeter has 32 narrow pipes. Kalman filtering is applied to one of the narrow pipes to estimate its flowrate. Three pressure sensors are connected to the narrow pipe. Upstream and downstream pressure signals are applied to a model of pipeline dynamics. The midpoint pressure is calculated and compared with the measured value. The error signal is fed back to the model. According to the principle of the Kalman filter, the estimated flowrate converges to the real flowrate. The Kalman-filtering estimation is conducted in a real-time computing system. In this study, the steady flowrate in a pipe is estimated and calibrated with measured data. The proposed Kalman-filtering-based laminar flowmeter demonstrates very promising performance.

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  • Koki Aizawa, Daisuke Haraguchi, Kotaro Tadano
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1000-1009
    Published: October 20, 2020
    Released: October 20, 2020
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    In robotic surgery, the load exerted on the insertion port in the patient’s abdominal wall due to misalignment of the robot’s remote center of motion and the insertion port or external forces acting on the tip of the forceps during surgery, can not only stress the patient’s body but also increase the friction between the robotic forceps and the trocar, and adversely affect fine surgical manipulations or the accuracy of force estimation. To reduce such loads on the insertion port in robotic surgery, this study proposes a control method for a surgical assist robotic arm with semi-active joints. The control method was implemented on a six-degree-of-freedom pneumatically driven vertical multi-joint robotic arm with a two-axis gimbal joint (two semi-active joints) that only executes torque control, which was previously developed by the authors, and verified through an experiment. The load on the insertion port is reduced by applying torque control on the semi-active joints to compensate for the external forces on the forceps. We constructed a control system that includes a disturbance compensator and conducted a velocity-control experiment by subjecting the forceps constrained by the insertion port to an external force. The results showed that when the torque was compensated for by the semi-active joints, the load on the insertion port was reduced by 65% and 52% when the external force on the tip of the forceps was 0 N and 3 N, respectively.

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  • Makoto Takada, Shuichi Wakimoto, Takero Oshikawa, Takeji Ueda, Takefum ...
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1010-1018
    Published: October 20, 2020
    Released: October 20, 2020
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    In this study, a pneumatically contracting active cloth has been developed; its application is proposed for a safe sitting-posture recovery system for wheelchair users to avoid fall-related accidents. The active cloth consists of thin artificial muscles knitted via a flat string machine. The safe wheelchair system is configured with an active cloth and seating pressure sensor. The seating pressure sensor, located on the seating surface of the wheelchair, estimates the inclination of the upper body of the user; when this reaches an angle that is dangerous for falling from the wheelchair, the active cloth contracts to correct the posture of the upper body. In this paper, we clarify the fabrication process and fundamental characteristics of the active cloth and indicate its potential as a mechanical element for welfare apparatuses by demonstrating a safe wheelchair system.

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  • Daisuke Yamaguchi, Tatsuya Hanaki, Yuji Ishino, Masayuki Hara, Masaya ...
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1019-1026
    Published: October 20, 2020
    Released: October 20, 2020
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    A prototype of a soft actuator for extreme environments was fabricated, and driven in a cryogenic temperature environment. Previous soft actuators cannot be used for robots in extreme environments because resin, the main fabrication material, exhibits weak environmental characteristics. Therefore, this study proposes the application of polyimide (PI) films to soft actuators. PI is characterized by excellent environmental resistance. However, the welding of PI is difficult because of its high resistance. In this study, a welding method was developed for PI films. This method does not require pretreatment, or the use of adhesives or additives to reduce resistance. Hence, an actuator that utilizes all the characteristics of PI was realized. The actuator was characterized in a cryogenic environment, which is one of the extreme environments, and was successfully driven at a liquid nitrogen temperature of 78 K. This proposed technology is not limited to cryogenic environments and is expected to provide extreme environmental resistance to existing soft robots.

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  • Satoru Sakai, Kazuki Nagai, Yasuki Takahashi
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1027-1033
    Published: October 20, 2020
    Released: October 20, 2020
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    The paper provides the first completed version of our identification approach as an intersection of two existing approaches: the physical model approach and the data table approach, for a set of valve flow blocks in nominal hydraulic cylinder dynamics. As one of the well-known physical models, the standard Bernoulli equation needs more accuracy in some cases owing to the steady flow assumption, whereas many data tables often need an expensive flow measurement. The proposed identification approach gives a new matrix representation that resembles the table representation but does not need any flow measurement as well as the steady flow assumption. In particular, unlike the conventional valve flow blocks, the updated valve flow blocks have no empty components via the projection guaranteeing the optimization. The effectiveness is confirmed experimentally by an application to the pressure estimation. The proposed identification approach will be applicable to other blocks including nonlinear friction blocks.

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  • Hironari Taniguchi, Nobuo Takemoto, Ren Yakami, Shuichi Wakimoto, Take ...
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1034-1043
    Published: October 20, 2020
    Released: October 20, 2020
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    It is known that introducing a pediatric externally powered prosthetic hand from an early age has certain merits such as the recovery of body image. However, this process is not popular in Japan. The high cost and technological problems of the hand have resulted in difficulty in its popularization. The pediatric prosthetic hand must be lighter and smaller than the adult one. Furthermore, parents of users prefer a prosthetic hand, such as a human arm and hand. We developed a prosthetic hand that demonstrates certain functionalities and appearances similar to a real human hand. The prosthetic hand consists of miniature McKibben actuators and is manufactured from acrylonitrile-butadiene-styrene resin and covered by a silicon glove. It has flexible joint structures and can grasp objects of various shapes. In this paper, we present a prototype of the pediatric prosthetic hand and the results of gripping experiments, bending and extension of finger experiments, and user tests.

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  • Yasuko Matsui, Daiki Hosomi, Masahiro Takaiwa
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1044-1051
    Published: October 20, 2020
    Released: October 20, 2020
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    Japan has an aging population, and the number of patients with physical impairment is increasing owing to aging and accidents. A contracture is a state in which joint movements are worsened owing to the hardening and loss of elasticity of the surrounding soft tissue such as muscle and skin, when a patient is immobile or bedridden for long durations. In particular, finger and wrist contractures can cause many inconveniences in daily life. Thus far, some rehabilitation devices have been developed. A power assist glove extends the finger but is difficult for patients to wear. This study focuses on wearability and risk avoidance, and develops a device with two parallel sticks that are driven by pneumatic actuators to simulate the motion of a physical therapist. After verifying the fundamental control performances, the safety function based on the estimated force applied by the patient and the improvement of effectiveness in rehabilitation using a USB camera are discussed.

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  • Masashi Yokota, Masahiro Takaiwa
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1052-1060
    Published: October 20, 2020
    Released: October 20, 2020
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    In Japan, where aging is faster than ever, the shortage of a young labor force is a serious problem, especially in the nursing field to support care recipients and in the primary industrial field to support heavy labor. Hence, the use of power assist devices that mechanically reduce the burden on the body is drawing increasing attention. This study focuses on the lifting motion, which can be performed by two methods, the squat method and the stoop method; the former involves bending the knee and the latter involves using the waist. The squat method is recommended because the burden on the waist is lower than that in the case of the stoop method. Currently, many types of wearable power assist devices to reduce the burden on the waist have been developed; however, they are based on the stoop method because of their assist mechanism. In this study, we developed a non-wearing type pneumatic power assist device that allows the squat method. After describing the basic concept and assist mechanism, the support effects are confirmed through experiments.

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  • Peizheng Yuan, Ginjiro Kawano, Hideyuki Tsukagoshi
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1061-1070
    Published: October 20, 2020
    Released: October 20, 2020
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    Soft contraction actuators are becoming important elements particularly for human-friendly robotic applications. However, it is challenging to achieve both a large operating distance while generating practical force. Hence, we present a new soft contraction actuator capable of realizing a high ratio contraction by pneumatic power. It can be easily fabricated using soft materials, including rubber tubes, one-way extensible cloth, and inextensible wire. Its initial shape is tubular but it can curve and coil to a helix shape owing to its different extensibilities on two sides when pressurized. A maximum contraction ratio of 78% and a 23 N contraction force can be achieved with an 11.6 mm initial outer diameter tube under 0.3 MPa. The effect of the tilt angle of a one-way extensible cloth on the helical shape is investigated, and a mathematical model illustrating the relationship between the contraction ratio and force is derived. Our experimental results suggest that this helical actuator has a much higher contraction ratio than a McKibben actuator under the same conditions. Finally, we discuss the potential application of the proposed actuator to a wearable device, i.e., for assisting the dorsiflexion of an ankle joint requiring a wide range of motion.

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Regular Papers
  • Ryosuke Iinuma, Yusuke Kojima, Hiroyuki Onoyama, Takanori Fukao, Shing ...
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1071-1079
    Published: October 20, 2020
    Released: October 20, 2020
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    In Japan, the aging and depopulation of its workforce are issues. Therefore, the development of autonomous agricultural robots is required for saving manpower and labor. In this paper, we described an autonomous pallet handling system for forklift, which can automatically unload and convey pallets for harvesting vegetables outdoors. Because of inserting the forks into a narrow pallet hole, accurate pallet posture estimation and accurate control of a forklift and the forks are required. The system can detect the pallet by deep learning based object detection from an image. Based on the results of object detection and measurement by horizontal 3D light detection and ranging (LiDAR), the system accurately estimates a distance as well as horizontal and vertical deviation between the forklift and the pallet in the outside field. The forklift is controlled by sliding mode control (SMC) which is robust to disturbances. Furthermore, the vertical LiDAR scans the pallet for precisely adjusting the height of the fork. The system requires the environment with no or little preparation for the automation process. We confirmed the effectiveness of the system through an experiment. The experiment is assumed that the forklift unloads the pallet from the vehicle as the real task of agriculture. The experimental results indicated the suitability of the system in real agricultural environments.

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  • Takehito Kikuchi, Taiki Oshimoto, Isao Abe, Kenichiro Tanaka, Yasue As ...
    Type: Paper
    2020 Volume 32 Issue 5 Pages 1080-1087
    Published: October 20, 2020
    Released: October 20, 2020
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    Walking is one of the most important activities in daily living, and difficulty walking presents a severe limitation. In this study, we develop shoes with elastomer-embedded flexible joints (EEFJ) that assist the tibialis anterior in its function during the initial stance and swing phase of the gait cycle. The EEFJ designed is suitable for shoes, with an adjustment mechanism incorporated for easy adjustment. To assess the ease of wearing, we measured the time it took four elderly subjects to wear the shoes for the first time. The donning time was less than one minute for all four participants. Furthermore, no one indicated discomfort when they walked naturally with the shoes. The supporting effect of the EEFJ shoes was assessed for ten healthy male subjects walking with their ankles relaxed. Statistical analysis reveals significant differences in the ankle at initial contact (p=0.02) and maximum plantar flexion (p=0.03). The average angle at initial contact while wearing the EEFJ shoes is 5.3° less than without it, and the average maximum plantar flexion is 5.1° less than without the shoes.

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