This paper presents a method for suppressing the vibration of galvanometric mirrors used in laser positioning systems. In such systems, it is important to carry out fast and high-precision positioning of the mirror and maintain the flatness of the mirror after positioning, so that the required control specifications are achieved. However, resonant vibrations of the mirror, which are excited by the moment force during positioning, lead to residual vibrations after positioning, thereby, deteriorating the flatness of the mirror and laser manufacturing accuracy. Therefore, we attempt to suppress such vibrations by mounting a piezoelectric element on the mirror, so that the functions of the actuator and sensor of the piezoelectric element are made use of when designing the vibration suppression controller. The applicability of the proposed method to industrial galvano scanners has been verified by performing experiments using a positioning device.

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Machine tools require XY stages that can be quickly and accurately controlled. However, when an XY stage is moved at a high speed, machine stand vibrates because of the reaction force of the actuator, and this vibration decreases the positioning accuracy. In this paper, we propose a control method based on ZPETC and used a peak filter to achieve quick and accurate tracking control. The effectiveness of the proposed method is verified by performing a simulation and experiment.

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Time delay of bilateral teleoperation seriously deteriorates the performance and stability. Time delay compensation by communication disturbance observer improves the operationality but simultaneously deteriorates the reproducibility of the environmental impedance. In this paper, we propose scaling down compensation value only in motion while in contact with an environment so that both good reproducibility and operationality can be achieved.

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A bimodal coiler system is a system for winding the materials rolled in a tandem mill in a rolling plant. In the bimodal coiler system, the tension changes greatly when the tail end of materials being rolled emerge out of the final stand, and as a result, the winding process might be disturbed. In this study, we attempt to suppress the fluctuation in the tension by employing a feedforward method based on final-state control. The effectiveness of the proposed method is verified by performing simulations.

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Humanoid robots with two arms and legs are expected to act as substitutes for humans, and hence, they are required to move as humans do and accomplish the assigned tasks. Numerous studies have been conducted to stabilize the motion of humanoids. Two methods, Virtual Horizontal Plane (VHP) and Generalized Zero Moment Point (GZMP) are proposed. In both these methods, we consider a stability region; the robot remains stable as long as the defined ZMP is within this region. However, on uneven terrain the robot may not fall down even if ZMP lies outside the defined stability region. To address the issue, we focused on the internal force between a robot and its environment. In this paper, we propose a novel stability condition based on the normal component of the internal force and not the friction force. The validity of the proposed method is confirmed by a simulation and an experiment.

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Recently, there has been increased focus on “haptic recording”; development of a motion-copying system is an efficient method for the realization of haptic recording. Haptic recording involves saving and reproduction of human motion data on the basis of haptic information. To increase the number of applications of the motion-copying system in various fields, it is necessary to reproduce human motion data by using haptic devices with different configurations. In this study, a method for the above-mentioned haptic recording is developed. In this method, human motion data are saved and reproduced on the basis of work space information, which is obtained by coordinate transformation of motor space information. The validity of the proposed method is demonstrated by experiments. With the proposed method, saving and reproduction of human motion data by using various devices is achieved. Furthermore, it is also possible to use haptic recording in various fields.

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This paper presents a structural and controller design approach for fast response and high-precision positioning systems. In order to achieve high positioning performance, it is important to compensate for the effects of mechanical vibration modes around the control bandwidth on the performance, where the suppression of the vibrations by the controller design should be effective, as well as optimize the positioning mechanism. Therefore, in this research, the primary vibration mode is canceled by the structural design in which a node corresponding to the mode is considered; the design guideline is led based on mode shapes obtained by modal analysis. According to the mechanism that we have designed, fast and precise positioning can be effectively achieved in the case of a simple mechanical structure. The proposed approach has been verified by experiments involving the use of a positioning device used for industrial galvano scanners.

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This paper proposes a knee stretch walking method for biped robots; the method involves the use of the toes and heel joints to increase walking strides. A knee can be stretched by switching control variables. By a knee stretch walking with heel contacts to the ground and toe takeoffs from the ground, biped robots can increase their walking stride and speed. The validity of the proposed method is confirmed by simulation and experimental results.

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With an increase in the number of elderly people in our society, the need for equipments that ensure activities of daily living and that can be used in strength training for reducing the need for nursing care is increasing. In this paper, we propose a method for controlling the level of muscle activation for a particular muscle group without EMG sensors; the force exerted by the tips of the limbs during motion is used to control the level of muscle activation. The method is based on a musculoskeletal model for limbs called functionally different effective muscles of three antagonistic pairs of six muscles in 2D space. Hill's equation is incorporated in the method to consider force-velocity characteristics of muscles. EMG measurement results for two muscles under isokinetic contraction in the lower limbs of a subject show that difference between the achieved activation level and the desired activation level is less than the error of the output force distribution. Moreover, the control method is applied to strength training. A manipulator that can facilitate the isokinetic contraction with more than the desired activation level for a specific muscle group is developed.

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In this study, a bilateral control system for tendon-driven robots is proposed. The rotation angle and torque of the robot joints are controlled by the proposed control system. In addition, a tendon-driven robot hand for haptic applications is developed. The proposed control system is employed by the robot hand to transmit force sensations.

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This paper proposes a bilateral control method for a teleoperation system with different sizes and work volumes. In the proposed controller, transformer-type bilateral control and gyrator-type bilateral control are integrated. The proposed control method can be used for the control of the motion of a slave robot; this involves intuitive manipulation of the master robot despite the structural difference between the master and slave.

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Currently, most of the plastic products are manufactured by using injection molding machines. The quality of the products depends largely on the injection force. In a typical force control system of an injection molding machine, the information about the force in the machine environment is obtained by a force sensor. However, force sensors have a few disadvantages such as signal noise, high sensor cost and narrow bandwidth. We have proposed the use of a reaction force observer based on the two-inertia resonant model. However, this method has some estimated error caused by a static friction in the holding process and a Coulomb friction in the screw back-pressure process. The estimation accuracy of the reaction force observer depends on parameter variations and the non-linear friction phenomenon. This paper proposes a new injection-force-estimation method based on the proposed high-order reaction force observer (HORFO), which is not influenced significantly by the nonlinear friction phenomenon. The effectiveness of the proposed method is confirmed by experimental results.

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This paper proposes a motion database based on real-world haptics. In order to treat advanced types of haptic information, the motion database contains not only the name of motion and position trajectory of a human operator but also force information. Moreover, the motion database is constructed and managed by a motion database management system, which performs the tasks of inserting, updating, retrieving, and deleting information pertaining to human motion. The motion database management system consists of a motion-copying system, which stores and reproduces the simple motions of the human operator. In this research, the validity and feasibility of the proposed method are verified. By using the proposed method, the motions of human operators in the industrial and medical fields can be stored, dynamically reproduced, and referred.

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In the future, with progress in robotics, robots will play an important role in the daily lives of human beings. The posture of a robot should be stable so that it does not fall. The posture of robots has been maintained stable mainly by using force and acceleration sensors. However, human beings maintain the stability of their postures on the basis of not only floor reaction force but also visual information. Therefore the use of visual information could be effective in maintaining the stability of the posture of a robot. The rotation invariant phase only correlation (RIPOC) method can be used to measure the rotation angle between two images. The accuracy of the RIPOC method is high in the case of 2D images, for example, in the case of fingerprint recognition and face recognition. However, it is difficult to accurately measure the rotation angle in 3D space by using this method. This paper describes a new extended RIPOC method that can be used to accurately measure the rotation angle in 3D space. By using visual feedback by the proposed method, the posture of robots can be stabilized. Experimental results that confirm the effectiveness of this method are provided in this paper.

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Force sensation plays an important role in force control systems. The bandwidth of force sensing is vital to reproduce the vivid force information. Generally, sensor-less force control systems use the position-sensor-based disturbance observer for force estimation. The bandwidth of force sensation as well as the control performance, however, is limited by the noise problems. This paper proposes a method to achieve the high performance force sensing. In the paper, the force estimation operation is performed by a combination of a Kalman-filter and a disturbance observer implemented in a field programmable gate array (FPGA). The wide bandwidth force sensing can be attained owing to the shortened sampling time by FPGA. Moreover, the noise in the force information is suppressed effectively by the Kalman-filter. The experimental results show the viability of the proposed method.

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Recently, haptic broadcasting technology has received considerable attention, and the construction of haptic broadcasting network is desired. In this paper, we propose a method of the construction of haptic transmission networks for haptic broadcasting by articulated multilateral control. The proposed method can be used to realize the following; 1) real-time-controlled haptic transmission between many systems and 2) change in the number of systems without modifying the control systems. As a result, it is possible to receive force feedback from remote environments when many haptic devices are connected to each other. The experimental results prove the feasibility of the proposed method.

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A two-degree-of-freedom control is generally used in the short-span seeking mode of hard disk drives (HDDs). Authors' group have proposed a perfect tracking control (PTC) method and a learning-based PTC (LPTC) method, which helps in suppressing overshoot by learning the tracking error in the acceleration and deceleration periods, so that high accuracy and presice speed control are achieved. In this paper, designing of a learning filter, which plays an important role in the suppression of the tracking error, is considered. Finally, simulations and experiments are performed to confirm the effectiveness of the designed filter.

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A person operating a mobile robot in a remote environment receives realistic visual feedback about the condition of the road on which the robot is moving. The categorization of the road condition is necessary to evaluate the conditions for safe and comfortable driving. For this purpose, the mobile robot should be capable of recognizing and classifying the condition of the road surfaces. This paper proposes a method for recognizing the type of road surfaces on the basis of the friction between the mobile robot and the road surfaces. This friction is estimated by a disturbance observer, and a support vector machine is used to classify the surfaces. The support vector machine identifies the type of the road surface using feature vector, which is determined using the arithmetic average and variance derived from the torque values. Further, these feature vectors are mapped onto a higher dimensional space by using a kernel function. The validity of the proposed method is confirmed by experimental results.

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In the networked control system, the communication delay and the time-varying communication delay exert a significant influence on the stability of the system and its performance. In particular, in the real-time control system, priority-driven routing is needed. In this paper, we propose a new relay structure and discuss its implementation using RT-Messenger, which is a real-time communication protocol. By performing some experiments, we confirmed that the proposed relay structure showed improved performance in terms of real-time measure.

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In general, voltage imbalances in 3-phase AC power systems are inevitable. 3-Phase PWM (Pulse Width Modulation) converter used in 3-wire systems are generally designed for use under limited imbalances of input voltages, and problems such as input current distortion, deterioration of output properties, degradation of efficiency and failure may occur in some cases.
These problems cause severe damages to industries in some cases, for example, semiconductor production machines: SEMI defined “SEMI F47-0200” and “SEMI F47-0706” standards that have to be satisfied to realize voltage sag immunity. In order to compensate the remained problems due to the unbalanced input voltages, particular storage devices are designed additionally for conventional converters. This paper proposes that the determination of both the instantaneous zero-phase sequence voltage and wye voltages is essential for 3-phase PWM converter control used for a 3-wire system to keep its output rated under occasional or long-term voltage imbalances in an AC system. This paper also describes a general new method to derive the components of the voltages of instantaneous wye and zero-phase sequence voltage from line-line voltages of a 3-wire system. This paper also describes a method to apply the voltages to control the converter. The results obtained on implementation verify that this new converter keeps its output rated under unbalanced conditions wider than those defined by SEMIs without particular storage devices as far as the AC voltages are remained live.

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This study examines a method for obtaining a fixed pulse pattern for a neutral-point-clamped PWM rectifier; the method involves the consideration of harmonic regulations. In the PWM rectifier system, a neutral-point-clamped PWM rectifier is connected to the secondary winding of a transformer connected to the grid, and the current is controlled by varying only the phase difference between the fixed pulse pattern and the power source. Therefore, it is possible to use a pulse pattern with reduced harmonics. Two typical types of harmonic regulations were selected. The harmonic regulations described in Harmonic Guidelines and IEEE-519 for high-capacity PWM rectifiers were considered in the above-mentioned method for obtaining the fixed pulse pattern. The fixed pulse pattern was obtained so as to minimize the ratio of the harmonic current content to the regulation values for each harmonic order. For evaluating the effectiveness of the proposed method, the pattern obtained was compared with the patterns obtained by using two other methods—cancellation of low-order harmonics and THD minimization.

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The major challenges faced during the speedup of the current collection system are improved contact performance (better contact between a pantograph and an overhead line) and reduction in the noise level along the railroad. We have improved the current collection system to reduce contact loss and decreased the number of pantographs to reduce the aerodynamic noise generated from the pantograph. Hence, the present Shinkansen train has usually two pantographs connected with a bus line. For further speedup, we must decrease the noise level to a greater extent. Thus, we must reduce the number of pantographs to one per train set. This 1-pantograph system, which we adopt for the first time as for Shinkansen train, needs to have high contact performance to reduce the contact loss more than ever. To reduce contact loss, without increasing upward force acting on the pantograph, we attempted to improve the compliance characteristics by using pantographs with a low mass head. We confirmed the effectiveness of such a current collection system by performing simulations and conducting on-track tests. The results show that the system implements the allowance for the contact loss ratio. Therefore, with the proposed system, we can complete the operational speeds of 360km/h.

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Magnetic gears have some advantages such as low mechanical loss and maintenance-free operation that are not observed in conventional mechanical gears. In addition, magnetic gears have inherent overload protection. Therefore, magnetic gears are expected to be used in special applications; for example, they can be used in a joint of a humanoid robot. Recently, various types of new magnetic gears have been proposed. Among these new gears, a surface-permanent-magnet-type (SPM-type) magnetic gear employing harmonic magnetic flux has gained attention because of its high transmission torque density, though it has a complex structure with multipole magnets. Some studies on an SPM-type magnetic gear have been carried out, but there are few papers on cogging torque. This paper describes the transmission torque characteristics of an SPM-type magnetic gear. The operating principle and the transmission torque under synchronous operation are formulated in accordance with the gear ratio. High orders of the cogging torque are computed by employing the 3-D finite element method, and the validity of the analysis is verified by carrying out measurements on a prototype. Furthermore, a method for reducing the cogging torque is discussed.

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This paper presents an adaptive feedfowad (FF) compensation method based on a deadbeat control framework for fast and precise positioning in mechatronic systems. The conventional FF compensation approach can design a FF compensator by considering both the frequency shaping and amplitude of FF control input, to suppress the response variations due to the perturbations in plant resonance frequency. However, since the conventional approach is not adaptive against frequency variations, an overshoot and/or undershoot response at the settling region would deteriorate the positioning performance. In this research, therefore, the proposed FF compensation approach with an adaptive identification system for the resonance frequency is adopted to achieve the desired positioning performance. The effectiveness of the proposed FF compensation approach has been verified by experiments using a prototype of an industrial positioning device.

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The structure of field system which gives a high flux density in air-gap is proposed for a linear synchronous motor (LSM) with large gap. The flux density and force density of LSM are analyzed respectively by using two-dimensional finite element method. The air-gap flux density exceeds the value of remanent magnetic flux density of used permanent magnet (PM). The thrust density of 100kN/m² can be obtained easily. This structure can be also applied to a rotational machine and etc.

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[in Japanese]

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[in Japanese]

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