〔Major achievements〕Development of a Jumping Mechanism Inspired by Leg Synchronization of PlanthopperYoshinobu Onozawa; Keisuke Yagi; Yoshikazu Mori, Corresponding, Abstract
We developed a small jumping mechanism inspired by planthopper. The planthopper jump is characterized by two functions of the hind legs; the leg synchronization using physical contact of the trochanter head and the power amplification using a torque reversal latch. The proposed jump mechanism adopts the unique leg synchronization strategy of the planthopper, and the nymphal and adult models of the hind legs are designed. However, the power amplification is modified to incorporate two torque reversal structures in a single-motion axis. The mechanisms were fabricated by 3D printer with polylactic acid (PLA) material and equipped with extension springs. They weighed 26 g and performed 260 cm vertical jump within one rotation in the frontal plane. The jump height is over 40 times greater than the body length. The experimental findings indicate that the precise synchronization of the rapid leg movement is an effective approach for the design of a jumping mechanism., ASME International
Journal of Mechanisms and Robotics, 03 Sep. 2024,
[Reviewed] Estimation of Time-varying Wrist Impedance in Peg-in-hole Task
Keisuke Yagi; Motoki Uchikoshi; Nobumichi Miyahara; and Yoshikazu Mori, Lead
Proceedings of SICE Annual Conference, Sep. 2023, [Reviewed]
ユニバーサルビーチで使用できる水陸両用車いすの開発
森 善一; 山中 裕登; 岡野 佑哉; 矢木 啓介
ライフサポート学会誌, Aug. 2023, [Reviewed]
Tele-Snap: a joint impedance estimation system using snap motor and openPose for remote rehabilitation diagnosisYuki Endo; Keisuke Yagi; Yoshikazu Mori; Toshinobu Takei; and Hiromi Mochiyama, Corresponding, We propose a remote joint impedance estimation system called Tele-snap for a rehabilitation diagnosis under the COVID-19 pandemic. Dynamic resistance of the human joint is essential physical information reflecting the motor function. The resistance is assessed based on the touching sensation of the doctor (physiotherapist), but the pandemic restricts such an in-person manner. Our proposing system aims to provide this physical information quantified by the joint impedance for a diagnosis in the telerehabilitation context. The proposed system employs a compact impulsive perturbation generator called the snap motor and a marker-less motion capture technology called the OpenPose. The subsystem installed in the patient's place is then simplified remarkably, which consists of the wearable snap motor and Raspberry Pi with a built-in camera module. The proposed system can collect the dataset for impedance estimation through the examiner's teleoperation of the snap motor and camera via a virtual private network, with no need for the operation by the patient. We verify the proposed system through an in-person experiment and then demonstrate the remote impedance estimation scheme., TAYLOR & FRANCIS LTD
Advanced Robotics, Apr. 2023,
[Reviewed] Experimental Verification of the Feedback Linearization Plant-Input-Mapping Discretization
Ryuya Tsuchida; Keisuke Yagi; and Yoshikazu Mori
Proc. of SICE International Symposium on Control Systems 2022, Mar. 2022, [Reviewed]
Development of a Boots-type Perturbation Device for Ankle Joint Impedance Estimation
Keisuke Yagi; Shohei Ito; Yoshikazu Mori, Lead
2022 IEEE/SICE International Symposium on System Integration (SII), Jan. 2022, [Reviewed]
〔Major achievements〕Plant-Input-Mapping Discretization Method for a Feedback System in the State-Space Form
Keisuke Yagi; Hiroaki Muto; and Yoshikazu Mori, Lead
Journal of Dynamic Systems, Measurement, and Control, Sep. 2021, [Reviewed]
Feasibility Study of a Wheel-Type Walking Assist Orthosis for Persons with Hemiparesis
Y. Mori; Y. Yonekura; E. Komatsu; K. Yagi
Proc. of The 2021 IEEE International Conference on Advanced Robotics and its Social Impacts, Jul. 2021, [Reviewed]
Remote Impedance Diagnosis with Snap Motor
H. Mochiyama; T. Takei; K. Yagi; M. Ando
Proc. of The 2021 IEEE International Conference on Advanced Robotics and its Social Impacts, Jul. 2021, [Reviewed]
A Study on the Plant-Input-Mapping Discretization for Nonlinear Control Systems Utilizing Feedback Linearization
Ryuya Tsuchida; Keisuke Yagi; Yoshikazu Mori
Proceedings of the 59th Annual Conference of the Society of Instrument and Control Engineers of Japan (SICE), Sep. 2020, [Reviewed]
Device Supporting Sitting Up Motion for Parkinson's Patients
小島祥平; 森善一; 矢木啓介
ライフサポート学会誌, 2019, [Reviewed]
Human Wrist Impedance Estimation Based on Impulse Response Induced by Snap-Through Buckling of Closed-Elastica
Keisuke Yagi; Hiromi Mochiyama, Lead
Proceedings of Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC'19), 2019, [Reviewed]
Development and Improvement of Semi-active Robotic Ankle Foot,Orthosis based on MR Fluid Technology
Modar Hassan; Keisuke Yagi; Hideki Kadone; Tomoyuki Ueno; Hiromi Mochiyama; Kenji Suzuki
Proceedings of Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC'19), 2019, [Reviewed]
Wearable Kinesthetic I/O Device for Sharing Wrist Joint StiffnessJun Nishida; Keisuke Yagi; Modar Hassan; Kenji Suzuki, In this paper, we developed a wearable kinesthetic I/O system, which is able to share wrist joint stiffness by measuring and intervening in four muscle activities on the forearm simultaneously through the same electrodes. This achieves interactive peg rehabilitation by sharing muscle activities among patients and therapists. Through the performance study, it was shown that 1) applied EMS and measured wrist joint stiffness, and 2) produced wrist joint stiffness and measured EMG value has a linear correlation, which allows designing a mapping function between the measured EMG value on one person and the EMS value applied to another person. In a perceptual study, which shared the wrist stiffness between two persons, participants were able to recognize the level of their confederate's wrist joint stiffness using a 4-point Likert scale linearly. The developed system would benefit a physical therapist and a patient for sharing their wrist stiffness and grip force, which are usually difficult to be observed in a visual contact.
Proceedings of Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC'19), 2019,
[Reviewed] MRLift: a Semi-active Lower Back Support Exoskeleton based on MR,Fluid and Force Retention TechnologyModar Hassan; Maxwell Kennard; Keisuke Yagi; Hideki Kadone; Hiromi Mochiyama; Kenji Suzuki, Wearable robots suffer from issues of usability, cost-performance, and battery life. These drawbacks hinder the development of their market and their implementation in healthcare and industry. Back support exoskeletons in particular rely heavily on mechanical storing of energy but are still mostly using traditional mechanical elements and actuators to achieve the task. The core technology of our work, named MRLink, uses a smart fluid in combination with a compression spring to produce a unique energy store-and-release functionality. With only 5 Watts MRLink can produce over 500N of braking force. The braking force, variable viscosity, can be continuously controlled through the supply current. With appropriate selection of the spring and control method, the required assist energy can be acquired from body weight and movement dynamics, stored momentarily and, released at the appropriate timing to assist the body motion. The MRLink does not require an external power source like pneumatic actuators, does not require gearboxes and large batteries like DC motors, and comes in a compact package. Thus, this technology has the potential to significantly contribute to wearable exoskeletons in general, and back support exoskeletons in particular. In this work we present the development of a back support exoskeleton prototype based on MRLink, we describe its functional details, and a pilot test partially verifying the proposed functions.
Proceedings of IEEE IROS2019, 2019,
[Reviewed] Plant-input-mapping discretization in state-space formKeisuke Yagi; Noriyuki Hori, The digital redesign technique called the Plant-Input-Mapping (PIM) method, which was developed previously in the transfer-function form, has been extended to a state-space based method, making the application of the method to multi-input multi-output systems easier. The transfer-function-based design uses the matched-pole-zero discretization, which is available only for single-input single-output systems, to satisfy the control-zero-principle. In the present study, the role of the principle is interpreted in the form of the uncontrollable modes under an observer-based state feedback structure. The step invariant model of the underlying continuous-time closed-loop system is used as the reference model, and the parameters of the digital controller are determined to match the discrete-time closed-loop system with this reference model. The resulting PIM controller guarantees the stability for any non-pathological sampling intervals as in the conventional transfer-function-based PIM and its superior performances to conventional digital redesign techniques are verified through some numerical simulations., Institute of Electrical and Electronics Engineers Inc.
Proceedings of the IEEE International Conference on Industrial Technology, 27 Apr. 2018,
[Reviewed] Human Joint Impedance Estimation With a New Wearable Device Utilizing Snap-Through Buckling of Closed-Elastica
Keisuke Yagi; Kenji Suzuki; and Hiromi Mochiyama, Lead
IEEE Robotics and Automation Letters, 2018, [Reviewed]
On the Determination of Mapping Rule and Sampling Interval for Human Joint Impedance EstimationKeisuke Yagi; Hiromi Mochiyama, The paper provides reasonable determination of the mapping rule and the sampling interval for human joint impedance estimation based on the observation from a variety of viewpoints. While a human joint can be modeled by a linear second-order continuous-time system, conventional parametric estimation methods such as the least squares method is carried out with the sampled input-output data, and thus, the obtained results belong to a difference model. In the paper, using the mapping model, the algebraic relationship transforming the difference model to the continuous-time model is derived with remaining a parameter to determine the mapping rule. This enables us to evaluate the effect of the determination of the mapping rule with the selected sampling interval, and the paper shows an example of the human ankle case. Although other examples are not shown here, based on the discussion, the determination provided by the paper can be utilized for other cases to estimate the human joint impedance by the parametric estimation methods., IEEE
2017 56TH ANNUAL CONFERENCE OF THE SOCIETY OF INSTRUMENT AND CONTROL ENGINEERS OF JAPAN (SICE), 2017,
[Reviewed] Steady-state error-compensation by feedforward-gain tuning for digital pim current regulation of a stepping-motor driverKeisuke Yagi; Noriyuki Hori, The present paper is concerned with the use of a self-Tuning feedforward-gain in place of integral control. The method is aimed at removing the steady-state error in following a nonzero reference step signal without having an integrator in the feedback loop. This technique is used to improve the PIM method, which is a digital redesign method for discretizing an analog controller with guaranteed stability but without system-Type preservation. The method is applied to the design of a digital current regulator in the driver for a stepping motor. Experiments are carried out to show that the resulting controller works in a safe manner under all the conditions tested and yields the same performance as that designed using the PIM method with the integrator included, which increases the controller order and can complicate the design., Acta Press
Proceedings of the IASTED International Conference on Modelling, Identification and Control, 2016,
[Reviewed] EXPERIMENTAL VERIFICATION OF A PRACTICAL DIGITAL DRIVER WITH SWITCHED GAIN-TUNING FOR FIVE-PHASE STEPPING-MOTORSKeisuke Yagi; Noriyuki Hori; Meyer Nahon, A digital driver that has a switched self-tuning gain in its current regulator is designed for five-phase stepping motors so that their performance could be improved and adjusted more easily, than with an analog driver. The regulator has a fixed gain block in its feedback loop and an adjustable gain in the feedforward path, replacing the integrator and the high gain that were required in previous designs to achieve good steady-state performance and fast response. Extensive experiments have been conducted under typical and extreme actuation conditions, and revealed that the proposed driver performs better than the analog drivers or their discretized equivalents, especially in eliminating undershoots, which were problematic with previous drivers., CSME TRANS
TRANSACTIONS OF THE CANADIAN SOCIETY FOR MECHANICAL ENGINEERING, 2015,
[Reviewed] A Study on Loss-of-Synchronism in Stepping Motors based on Equilibrium Rotor-AnglesK. Yagi and N. Hori, Lead, The present paper is concerned with a fundamental study on the phenomenon called Loss of Synchronism (LOS) in a stepping motor from the view-point of rotor-angles in equilibria. Conditions of the rotor are deliberated in terms of its angle, velocity, and acceleration, and a set of three conditions is proposed for determining the state of LOS. A simulation model is constructed in the Simulink environment for a hybrid live phase stepping-motor that is driven by an industrial driver and is used for evaluating the derived conditions through extensive simulations. They show that the LOS state of the motor under ideal conditions can be detected correctly. The developed motor driver model and the LOS algorithm are useful tools for simulating LOS and expected to pave a way to practical techniques for preventing and recovering from LOS., IEEE
Proceedings of IEEE IECON'15, 2015,
[Reviewed] Design of a fail-safe mechanism for a five-phase stepping motor
M. Ishizawa; K. Yagi; and N. Hori, Corresponding
Proceedings of SICE Annual Conference 2013, 2013, [Reviewed]
Prevention of loss-of-synchronism in stepping motors through self-tuning current regulationKeisuke Yagi; Noriyuki Hori, A self-tuning current-regulator is designed for a stepping-motor such that loss-of-synchronism (LOS) between the input pulses and the angular position is prevented by increasing motor current when the torque load is applied to the motor shaft. This is based on the observation that the driver voltage drops as the torque disturbance increases and this can be interpreted as a reduction of a gain. An adjustable gain is self-tuned such that the motor current is increased to maintain, under torque variations, the overall gain constant, which is set to meet the torque requirement with a suitable safety-margin. The proposed driver is tested through extensive experiments on a commercial driver for an industrial stepping-motor to illustrate the practical veracity of the proposed method.
Proceedings of the IASTED International Conference on Control and Applications, CA 2012, 2012,
[Reviewed] Prediction of loss-of-synchronism for a five-phase stepping motor
K. Yagi and N. Hori, Lead
Proceedings of SICE Annual Conference 2011, 2011, [Reviewed]
