Masatoshi Seki

Waseda University, Tokyo, Tokyo-to, Japan

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Publications (22)7.01 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Recently, a large amount of stroke survivors are suffering from motor impairment. However, existed therapy interventions have limited effects to restore normal motor function. Thus, we proposed a novel control strategy for gait rehabilitation of hemiplegic patients. The whole system consists of a Functional Electrical Stimulation (FES) device and Treadmill-Walk system. FES contributes to improve the quality of the gait based on real-time adjustment of gait pattern. During gait, the electrical stimuli from separate output channels of an FES device are launched to stimulate two lower extremity muscles (Tibialis Anterior (TA) and Hamstrings). Stimulus launching procedure is based on identifying subject's gait state (stance and swing phases). According to the current variation of treadmill motor, gait phase and muscle activation of lower limbs can be determined during walking on Treadmill-Walk. Three able-bodied subjects simulated hemiplegic patients in the experiment. The results indicated that the proposed method is a safe, feasible and promising intervention.
    Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on; 01/2013
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    ABSTRACT: Mechanical performance of a surgical robot can be evaluated and improved based on a working score; however, intuitive operability cannot be evaluated in this way. We propose a method that measures the user's brain activity for evaluating intuitive operability from the perspective of cognitive science. We hypothesized that hand-eye coordination, such as the slave configuration for the endoscope, has the greatest effect on intuitive operability, because it is the cause of physical differences between a human and a robot. The objective of this paper is to clarify the appropriate slave configuration for the endoscope to study hand-eye coordination using brain activity measurements. In the experiment, we used a brain imaging device, optical topography, to measure the users' brain activity while they controlled the hand-controller to position the tip of the virtual arm on the target. The experiment was carried out a number of times with the virtual arm position configured in a variety of ways. According to the results, some subjects showed peak performance with a specific slave configuration. We conclude that the slave configuration with the highest brain activity depends on the body image, which is a spatial symbol in the human brain from the perspective of cognitive science.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: Powered prosthetic hands are becoming increasingly functional through sensory feedback. However, when using electrical stimulation as sensory feedback for electromyographic (EMG) prosthetics, stimulation artifacts may cause EMG data noise. Electrical stimulation and EMG measurements are therefore performed using time-division methods in rehabilitation facilities. Under time-division methods, EMG levels cannot be acquired at the stimulation time. Highly functional prosthetic hands that can estimate grip force, however, use advanced signal processing and require detailed EMG information. EMG measuring cycle expansion may make grip force estimation unstable. We therefore developed a grip force estimation system using muscle stiffness and EMG as the estimation source signals. The estimation system consists of a muscle stiffness sensor, an EMG sensor and an estimation algorithm. We chose a tray holding task for the system evaluation. A weight is dropped on the tray and subjects are expected to control the tray's attitude. Grip force, EMG, and muscle stiffness are measured, and the measured and estimated grip forces are compared. The proposed algorithm estimates grip force with an error of just 18[N], which is 30% smaller than in EMG-only methods. The system response time is lower than human mechanical reaction time, validating the effectiveness of the proposed method.
    Robotics and Automation (ICRA), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: In consideration of a large proportion of stroke survivors with persistent deficits, current interventions have limited ability to restore normal motor function. We propose a gait training system for gait rehabilitation of hemiplegic patients with convalescent stroke. It consists of a functional electrical stimulation (FES) device which is used to influence the gait pattern instantly to improve the quality of the gait, and a treadmill with two separated belts. The stimulus triggers from the FES could be controlled automatically by the subject's gait phase determination, including stance phase and swing phase. Gait phase could be estimated and recognized through observing current value variation of the treadmill motor during the subject's walking on the treadmill belts. In this paper, we have preliminarily tested the feasibility of the proposed method through hemiplegic simulation experiments. Also, Tibialis Anterior (TA) and quadriceps on the hemiplegic side were successfully stimulated by the expected FES stimuli during gait.
    Control, Automation and Systems (ICCAS), 2013 13th International Conference on; 01/2013
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    ABSTRACT: Surgical robot has been considerable improvement in recent years, but their intuitive operability, representing user interoperability, has yet to be quantitatively evaluated. Thus, we propose a method for measuring brain activity to determine intuitive operability so as to design a robot with intuitive operability. The objective of this paper is to determine the angle and radius between the endoscope and the manipulator that allows users to perceive the manipulator as part of their body. In the experiments, subjects moved the hand controller to position the tip of the virtual slave manipulator on the target in the surgical simulator, measured the brain activity through brain imaging devices. The experiment was carried out a number of times with the virtual slave manipulator configured in a variety of ways. The results show that brain activation is significantly greater with a particular slave manipulator configuration. It concludes that the hand–eye coordination between the body image and the robot should be closely matched in the design of a robot with intuitive operability.
    SCIS-ISIS 2012; 11/2012
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    ABSTRACT: In this paper, we develop a new haptic interface called “Force Blinker 2” to navigate the visually impaired. In Force Blinker 2, rotating weights and repulsive magnets are used to reduce the force generated in the opposite direction to the traveling direction, which caused false recognition in the previous system, “Force Blinker 1.” In Force Blinker 2 [diameter: 30 (mm), weight: 365 (g)], based on the balance of the centrifugal force of the weight and repulsive force of permanent magnets, the rotational radius of the weight varies depending on the velocity of the rotational weight. First, from a mechanical and control performance perspective, it has been confirmed using an encoder and high-speed camera that the rotational angle, velocity, and weight position are well controlled. Second, ten visually impaired subjects evaluated Force Blinker 2 by comparing it with Force Blinker 1, a fixed radius type interface. The directions presented by Force Blinker 2 were correctly recognized at a rate of approximately 85%, which is about a 10% improvement over the rate achieved by Force Blinker 1. This means the effect of decreasing the force in the opposite direction to the traveling direction on recognition thereof yields about a 10% improvement in recognition performance. In the future, we intend to integrate a route decision system with a cane containing the built-in haptic interface.
    IEEE Transactions on Industrial Electronics 11/2012; 59(11):4112-4119. · 6.50 Impact Factor
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    ABSTRACT: Surgical robots have improved considerably in recent years, but intuitive operability, which represents user inter-operability, has not been quantitatively evaluated. Therefore, for design of a robot with intuitive operability, we propose a method to measure brain activity to determine intuitive operability. The objective of this paper is to determine the master configuration against the monitor that allows users to perceive the manipulator as part of their own body. We assume that the master configuration produces an immersive reality experience for the user of putting his own arm into the monitor. In our experiments, as subjects controlled the hand controller to position the tip of the virtual slave manipulator on a target in a surgical simulator, we measured brain activity through brain-imaging devices. We performed our experiments for a variety of master manipulator configurations with the monitor position fixed. For all test subjects, we found that brain activity was stimulated significantly when the master manipulator was located behind the monitor. We conclude that this master configuration produces immersive reality through the body image, which is related to visual and somatic sense feedback.
    the 34th Annual International Conference of the IEEE Engineering in Medicine and Biology Society; 08/2012
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    ABSTRACT: Surgical robots have improved considerably in recent years, but intuitive operability, which represents user inter-operability, has not been quantitatively evaluated. Therefore, for design of a robot with intuitive operability, we propose a method to measure brain activity to determine intuitive operability. The objective of this paper is to determine the master configuration against the monitor that allows users to perceive the manipulator as part of their own body. We assume that the master configuration produces an immersive reality experience for the user of putting his own arm into the monitor. In our experiments, as subjects controlled the hand controller to position the tip of the virtual slave manipulator on a target in a surgical simulator, we measured brain activity through brain-imaging devices. We performed our experiments for a variety of master manipulator configurations with the monitor position fixed. For all test subjects, we found that brain activity was stimulated significantly when the master manipulator was located behind the monitor. We conclude that this master configuration produces immersive reality through the body image, which is related to visual and somatic sense feedback.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2012; 2012:337-43.
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    ABSTRACT: Essential tremor is a disorder that causes involuntary oscillations in patients while engaging in actions or while maintaining a posture. ET patients have serious difficulties in performing activities of daily living such as eating food, drinking water, and writing. We have thus been developing an EMG-controlled exoskeletal robot to suppress tremors. The EMG signal of ET patients involves a mix of voluntary movement and tremor signals. To control the exoskeletal robot accurately, tremor signals must be removed from the patient's EMG signal. To date, we have been developing a filter to remove tremor signals from the patient's EMG. The design of this filter was based on the hypothesis that the rectified tremor signals are able to be approximated by a powered sine wave. This filter was found to have a large effect on removing tremor signals. However, tremor signals are generated both while performing voluntary movement and while maintaining a posture, and the filter was attenuating both signals. To control this robot accurately, the signal generated while performing voluntary movement is expected not to be attenuated. To accomplish this, we try to use a parameter that reflects a state of the patient's movement, performing a voluntary movement or maintaining a posture, as a switch to activate the powered sine filter. This paper provides an analysis of the favorable parameters. We focus on two parameters: the peak-to-peak interval of the rectified EMG signal, and the interval of the flat and low amplitude area of the rectified EMG signal. Through evaluation, it is affirmed that both parameters change with the state of the patient's movement. However, the latter parameter is superior to the former in terms of variability, which indicates that the interval of the flat and low amplitude area of the rectified EMG signal is a more favorable parameter to promote control of the exoskeletal robot. As a future work, we will mount the parameter to the algorithm and evaluate the robotic system.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2012; 2012:2244-50.
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    ABSTRACT: Surgical robots have undergone considerable improvement in recent years, but the intuitive operability, representing user inter-operability, has not been quantitatively evaluated. Thus, we propose a method for measuring brain activity to determine intuitive operability in order to design a robot with intuitive operability. The objective of this paper is to clarify the angle between the endoscope and the manipulator that facilitates users perceiving the manipulator as part of their body. In the experiments, while subjects controlled the hand controller to position the tip of the virtual slave manipulator on the target in the surgical simulator, we measured the brain activity through brain imaging devices. We carried out the experiment a number of times with the virtual slave manipulator configured in a variety of ways. The results show that activation of the brain is significant with the slave manipulator configured such that the angles are slanted with respect to the horizontal. We conclude that the body image affects hand-eye coordination, which is related to visual and somatic sense feedback.
    2012 IEEE International Conference on Robotics and Automation; 05/2012
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    ABSTRACT: In recent years, research and development have been conducted on robots designed to assist people with disabilities in daily activities. There is a great demand for control technology for realizing flexible contact and cooperative behavior. We here report a novel impedance control method based on a fractional calculation inspired by the viscoelastic properties of biomaterials such as muscle. This paper presents an evaluation of this concept by simulation and by experiment using a robotic system for body weight support. The experimental results demonstrated that the fractional impedance controller has superior contact force absorption performance compared with a conventional controller, especially for high-stiffness objects and high-velocity movement. This fractional impedance controller may be useful especially for the purpose of flexible contact for assistive and rehabilitation robots for people.
    Advanced Robotics 01/2012; · 0.51 Impact Factor
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    ABSTRACT: Essential Tremor (ET) refers to involuntary oscillations of a part of the body. ET patients face serious difficulties in performing daily living activities. Our motivation is to develop a system that can enable ET patients to perform their daily living activities; hence we have been developing a myoelectric controlled exoskeletal robot for ET patients. However, the EMG signal of ET patients contains not only voluntary movement signals but also tremor signals. Accordingly, to control this robot correctly, tremor signals must be removed from the EMG signal of ET patients. To date, we have been developing a filter to remove tremor signals, which has been largely effective in this. However, tremor signals are generated both while voluntary movement is being performed and while a posture is being maintained, and the filter ended up attenuating both these signals. But, to control this robot accurately, the signal generated during performance of voluntary movement is expected not to be attenuated. Therefore, in this paper, we propose a method that attenuates only tremor signals arising during maintenance of a posture. To accomplish this objective, we focus on the frequency of tremor signals. From the experiment, we confirmed the characteristic that the frequency of tremor signals changed depending on the state of the patient's movement. We then used frequency as a switch to activate the previously proposed filter by setting a threshold. As an evaluation, signals processed by the proposed method were input to a time delay neural network. The proposed method succeeded in partly improving recognition due to reduction of attenuation during performance of voluntary movement. However, the proposed method failed recognition in cases where the frequency of tremor signals varied widely. As a future work we will review the method to calculate the frequency of tremor signals and improve recognition.
    Biomedical Robotics and Biomechatronics (BioRob), 2012 4th IEEE RAS & EMBS International Conference on; 01/2012
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    ABSTRACT: A number of upper limb amputees experience difficulty in picking up a food bowl during a meal, because grip force estimation using EMG currently does not provide sufficient accuracy for this task. In this paper, we propose a grip force estimation system that allows amputees to pick up a bowl with a prosthetic hand by using the properties of muscle stiffness in addition to EMG. We have chosen a tray holding task to evaluate the proposed system. A weight is dropped on the tray and the subjects are expected to control the tray's attitude during the task. Actual grip force, EMG, and muscle stiffness are measured, and the actual measured grip force is compared with the estimated grip force for evaluation. As a result, the proposed algorithm is found to be able to estimate grip force with an error of just 18[N], which is 30% smaller than in the method that uses only EMG. From the result that the response time estimated by proposed system is even less than a human's mechanical reaction time, the effectiveness of the proposed method has been validated.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:4116-9.
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    ABSTRACT: Radio frequency ablation (RFA) for lung cancer has increasingly been used over the past few years because RFA is minimally invasive treatment for patients. As a feature of RFA for the lung cancer, lung has the air having low thermal conductivity. Therefore, RFA for lung has the advantage that only the tumor is coagulated because heating area is confined to the immediate vicinity of the heating point. However, it is difficult for operators to control the precise formation of coagulation zones due to inadequate imaging modalities. We propose a method using numerical simulation to analyze the temperature distribution of the organ in order to overcome the current deficiencies. Creating an accurate thermophysical model was a challenging problem because of the complexities of the thermophysical properties of the organ. In this work, as the processes in the development of ablation simulator, measurement of the pressure dependence of lung thermal conductivity and in vitro estimation of the temperature distribution during RFA is presented.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:5753-7.
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    ABSTRACT: Essential Tremor (ET) refers to involuntary movements of a part of the body. ET patients have serious difficulties in performing daily living activities. Our ultimate goal is to develop a system that can enable ET patients to perform daily living activities. We have been developing an exoskeleton robot for ET patients. We make use of the electromyogram (EMG) signal to control this robot. However, the EMG signal of ET patients contains not only signals from voluntary movements but also noise from involuntary tremors. In this paper, we focus on developing a signal processing method to suppress tremor noise present in the surface EMG signal. The proposed filter detected attenuation ratio by the correlation between the last EMG data and one period squared sine wave. The filtered EMG signals indicated that essential tremor noise of the elbow flexed posture while holding a water-filled bottle was suppressed. In addition, voluntary information was less affected by the filter. Welch's t-value test confirmed that ease of extraction of voluntary movement was increased by the proposed filter.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:7487-91.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Essential Tremor (ET) refers to involuntary movements of a part of the body. ET patients have serious difficulties in performing daily living activities. We have been developing a myoelectric controlled exoskeletal robot to suppress tremor. However, the EMG signal of ET patients contains not only signals from voluntary movements but also noise from involuntary tremors. Then, we have developed a signal processing method to suppress tremor noise present in the surface EMG signal. The proposed filter is based on the hypothesis that tremor noise could be approximate to powered sine wave. In this paper, we have integrated tremor canceling filter and neural network (NN) to recognize the tremor patient's movement. According to the result, it was confirmed that the proposal filter increased accuracy of recognition, especially stable phase on elbow flexed position as “OFF”.
    Proceedings of the IEEE International Conference on Systems, Man and Cybernetics, Anchorage, Alaska, USA, October 9-12, 2011; 01/2011
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    ABSTRACT: Essential Tremor (ET) refers to involuntary movements of a part of the body. ET patients have serious difficulties in performing their daily living activities. Our ultimate goal is to develop a system that can enable ET patients to perform their daily living activities. We are in the process of developing an exoskeletal robot for ET patients. This robot is controlled by estimation of voluntary movement using surface electromyogram (EMG) signal input and a Neural Network (NN) learning algorithm. However, the EMG signal of ET patients contains not only signals from voluntary movements but also noise from involuntary tremors. We have therefore developed a signal processing method to suppress tremor noise present in the surface EMG signal. The proposed filter is based on the hypothesis that tremor noise can be approximated to powered sine wave. It have been confirmed that the proposed filter increases the accuracy of recognition. In this paper, we have focused on the effect of inconsistency of weight load between instruction signal and input signal. When the instruction signal comprised unloaded motion, our voluntary movement estimation method worked stably with the loaded motion's EMG input.
    01/2011;
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    ABSTRACT: In the navigation of the visually impaired, an external input such as force or sound is required about the direction of travel to reach a particular target position. We develop a new haptic interface called “Force Blinker 2” to navigate the visually impaired. In Force Blinker 2, rotating weights and repulsive magnets are used to reduce the force generated to the direction opposite the traveling direction, which caused false recognition in the previous system, “Force Blinker 1.” In Force Blinker 2, the rotational radius of the weight varies depending on the velocity of the rotational weight. Ten visually impaired subjects evaluated Force Blinker 2 by comparing it with Force Blinker 1, a fixed radius type interface. The directions presented by Force Blinker 2 were correctly recognized at a rate of approximately 85%, which is approximately a 10% improvement over the rate by Force Blinker 1.
    Intelligent Robots and Systems (IROS), 2010 IEEE/RSJ International Conference on; 11/2010
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    ABSTRACT: We reported a novel impedance control method based on a fractional calculation inspired by the viscoelastic properties of biomaterials such as muscle. This fractional impedance controller was found to realize superior impact absorption for the purpose of flexible contact for assistive and rehabilitation robots. This paper presents a preliminary evaluation of this concept using simulations and experiments. The numerical analysis results demonstrate that a fractional impedance controller has superior impact absorption performance than a conventional controller for contact with the elastic objects, especially for high stiffness objects and high velocity movement. The numerical analysis also reveals that using a fractional controller improved the robustness with respect to the robot dynamics. Moreover, the experimental results demonstrate that the fractional controller effectively suppresses the force between a person and a robot.
    2010 IEEE/RSJ International Conference on Intelligent Robots and Systems, October 18-22, 2010, Taipei, Taiwan; 01/2010
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    ABSTRACT: We here report a novel impedance control method based on a fractional calculation inspired by the viscoelastic properties of biomaterials such as muscle. This fractional impedance controller was found to realize superior impact absorption for the purpose of flexible contact for assistive and rehabilitation robots for people. This paper presents an evaluation of this concept using simulations and experiments. The numerical analysis results demonstrated that a fractional impedance controller has superior impact absorption performance than a conventional controller for contact with elastic objects, especially for high-stiffness objects and high-velocity movement. Moreover, experiments using a robotic system for body weight support demonstrate the effectiveness of the fractional controller for suppressing a large contact force between subject and robot.
    01/2010;