Masatoshi Seki

Waseda University, Tokyo, Tokyo-to, Japan

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Publications (29)7.07 Total impact

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    ABSTRACT: Surgical robots have improved considerably in recent years, but their intuitive operability, and thus their user interoperability, has yet to be quantitatively evaluated. Thus, we propose a method for measuring a user's brain activity while operating such a robot, to better enable the design of a robot with intuitive operability. The objective of this study was to determine the angle and radius between an endoscope and manipulator that best allows the user to perceive the manipulator as being part of their own body. In the experiments, a subject operated a hand controller to position the tip of a virtual slave manipulator onto a target in a surgical simulator while his/her brain activity was measured using a brain imaging device. The experiment was carried out several times with the virtual slave manipulator configured in a variety of ways. The results show that the amount of brain activity is significantly greater with a particular slave manipulator configuration. We concluded that the hand-eye coordination between the body image and the robot should be closely matched in the design of a robot having intuitive operability.
    No preview · Article · Jan 2015 · Journal of Advanced Computational Intelligence and Intelligent Informatics
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    ABSTRACT: An essential tremor (ET) is a disorder that causes involuntary oscillations. ET patients face serious difficulties in performing such daily living activities as eating, drinking, and writing. We have been developing an exoskeleton to suppress tremors and support the eating movements of ET patients. The objective of this study is to propose a passive mechanism that prevents the appearance of the compensatory shoulder movement without using an actuator. The basic concept of this study is developing the mechanism to coordinate two DoF movement of elbow joint. Two DoF movement of elbow joint is constrained to passive one DoF by our wearable robot. The mechanism of our robot and constrain mechanism is optimally designed to reduce the compensatory movement during eating movement. To develop such mechanism, we first analysed the eating movement to derive the required specification of the mechanism. Then, we proposed a prototype based on the requirement. Finally, we evaluate the effect of the prototype to reduce the compensatory movement. It is confirmed that the proposed prototype had great effect on the reduction. As a future work, we will optimize the structure and the material of the mechanism to reduce the weight of the mechanism
    No preview · Article · Oct 2014
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    ABSTRACT: Essential tremor is a disorder that causes involuntary oscillations in patients both while they are engaged in actions and when maintaining a posture. Such patients face serious difficulties in performing such daily living activities as eating, drinking, and writing. We have been developing an electromyogram (EMG)-controlled exoskeleton to suppress tremors and to support the movements of these patients. In this paper, we proposed a novel signal processing method to demodulate the patients' EMG signal, which contains the voluntary movement signal and the tremor noise. This is a real-time signal processing method for multiple types of noise. From a technical point of view, this processing is essential because, at present, there are no real-time methods addressing the multiple noise sources. Also, from an application point of view, this method is essential for the accurate control of the exoskeleton depending on the patients' voluntary movement intention. We confirmed that the proposed method showed feasibility to demodulate the EMG signal which is modulated by the tremor signal.
    No preview · Article · Oct 2014
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    ABSTRACT: Surgical robots have undergone considerable improvement by only mechanical performance in recent years, but the intuitive operability has not been quantitatively evaluated. This paper presents the brain activity measurement method to determine intuitive operability to design a robot with intuitive operability. The objective of this paper is to validate that the specific brain area which is the intraparietal sulcus activates if the user controls the slave manipulator positioned intuitively. 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 the functional near-infrared spectroscopy (f-NIRS). We carried out the experiment a number of times with the virtual slave manipulator configured in a variety of ways. The results show that the brain activated significantly with the specific slave manipulator configured such that the angles matched the human body. We conclude that the how strongly human feels the manipulator belongs to his body affects hand-eye coordination, which is related to visual and somatic sense feedback.
    Preview · Article · Jan 2014
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    ABSTRACT: Essential tremor is a disorder that causes involuntary oscillations in patients both while they are engaged in actions and when maintaining a posture. Such patients face serious difficulties in performing such daily living activities as eating, drinking, and writing. We have been developing an electromyogram-controlled exoskeleton to suppress tremors and support the eating movements of these patients. This exoskeleton is designed to suppress tremors and support voluntary movement at the elbow in terms of flexion and extension: movement of the elbow is essential in eating movements. In this study, we examined the effectiveness of our prototype exoskeleton at suppressing tremors. Our goal was to answer two questions: To what extent are the oscillations suppressed when wearing the exoskeleton? Is the exoskeleton able to suppress the oscillations sufficiently to allow eating movements? We were able to confirm experimentally that our exoskeleton can effectively suppress tremors to support eating movements.
    No preview · Article · Dec 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.
    No preview · Conference Paper · May 2013
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    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.
    No preview · Conference Paper · Jan 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.
    No preview · Conference Paper · Jan 2013
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    ABSTRACT: Learning is essential for human being. In this article, we analyzed the human learning strategy in the multi-movement discrimination by learning machine. Especially, the leg movements' discrimination using Self Organizing Mapping was taken as an example. Firstly, based on the experiment by ten healthy subjects, learning strategies were divided into two strategies; Convergence strategy (improving the repeatability of each movement) and Independence strategy (conducting different movements). Secondly, a child with severe impairment conducted similar experiments. He selected Convergence strategy and his index values to evaluate the degree of convergence and independence of his leg's movements were quite similar with healthy subjects' value. The generality of Convergence and Independence strategies was suggested in multi-movement discrimination task.
    No preview · Article · Jan 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.
    No preview · Conference Paper · Jan 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.
    Full-text · Conference Paper · Nov 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.
    No preview · Article · Nov 2012 · IEEE Transactions on Industrial Electronics
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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.
    Full-text · Conference Paper · Aug 2012
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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.
    No preview · Article · Aug 2012 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
  • [Show abstract] [Hide abstract]
    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.
    No preview · Article · Aug 2012 · Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
  • [Show abstract] [Hide abstract]
    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.
    No preview · Conference Paper · Jun 2012
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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.
    Full-text · Conference Paper · May 2012
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    Yo Kobayashi · Takao Watanabe · Masatoshi Seki · Takeshi Ando · Masakatsu · G Fujie
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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.
    Full-text · Article · Jan 2012 · Advanced Robotics

  • No preview · Article · Jan 2012
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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. 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”.
    No preview · Conference Paper · Oct 2011