論文 - 村上　俊之

Estimation of Posture and Position Based on Geometric Calculation Using IMUs

Murata Y., Murakami T.

IECON Proceedings (Industrial Electronics Conference) （IECON Proceedings (Industrial Electronics Conference)）  2019-October   5388 - 5393 2019年10月

ISSN  9781728148786

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© 2019 IEEE. In IMUs, three sensors, acceleration, gyroscope, and magnetic, are implemented. Data get from these sensors are used to acquire posture and position of each sensor. Theoretically, from a simple integration of an acceleration and an angular velocity, position and posture could be calculated. The IMU is applied to many fields due to its user friendly structure. Human motion detection is one of interesting applications. However, small error in the measured data are also integrated, hence position error and posture error, which is also called drift, occur. The purpose of this paper is to estimate position and posture using IMUs without human model. Two IMUs are used to estimate posture and position. For posture estimation, complementation of posture angle are done from an 'angular velocity' and a 'gravity acceleration'. For position estimation, complementation by relative relationship between 2 sensors has been proposed. This is the novel part of this paper. Two ways of position complementation algorithm are proposed. One method is complementation by Kalman Filter, and the other is complementation by error estimation. Error estimation is based on a theory of mode transfer between relative space and world space. The validation of proposed method is done by experiment.

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Continuously Variable Transmission by High-speed Path Switching of Linear Electro-hydrostatic Actuator

Sugihara K., Nozaki T., Murakami T.

IECON Proceedings (Industrial Electronics Conference) （IECON Proceedings (Industrial Electronics Conference)）  2019-October   3603 - 3608 2019年10月

ISSN  9781728148786

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© 2019 IEEE. In robotic systems, reduction drives are utilized to increase actuators' force. Actuators with a constant reduction ratio can not achieve characteristics of both high velocity driving and high force driving. In order to perform various tasks, high force drive and high velocity drive are required for robotic actuators since required driving characteristics are different among tasks. Therefore, a mechanism which can change a reduction ratio continuously is needed. This paper proposes a mechanism that can change a reduction ratio with a linear electro-hydrostatic actuator (EHA). The proposed mechanism switches between two discrete reduction ratios by switching two oil paths with solenoid valves. Furthermore, this paper realizes a continuously variable reduction ratio by switching the solenoid valves quickly. This paper confirms that the reduction ratio changes continuously and widely by simulations.

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Evaluation of Langevin Model for Human Stabilogram Based on Reproducibility of Statistical Indicators

Tawaki Y., Murakami T.

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS （Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS）     1934 - 1939 2019年07月

ISSN  9781538613115

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© 2019 IEEE. Fall risk is a serious problem especially for the elderly. Fall accident causes fracture, and it leads to bedridden. Early detection of balance inability and rehabilitation training is important to decrease the risk. Quiet standing test is one of the physical tests to assess the balance inability of human. When the human is standing, he/she controls the plantar force to keep the balance. Center of pressure (COP) is the representative parameter to explain the plantar force movement. During the quiet standing test, COP fluctuates unconsciously. There are many researches that analyze the relationship between the COP fluctuation and balance inability. Many statistical indicators have been developed to assess the fluctuation specification.In contrast, several researchers have been tried to reveal the COP fluctuation mechanism by introducing stochastic mathematical model. Ornstein-Uhlenbeck process and diffusion equation are often introduced to the model. The mathematical models have been developed, and analyzed how visual input is related to the model parameters. If the mathematical model can explain the COP fluctuation completely, it becomes easier to assess the balance ability by comparing the model parameters.However, statistical indicators are still used in the clinical cases, thus there is room to discuss which statistical indicators to be used for assessment. The purpose of this research is to explore the relationship between statistical indicators and numerical model by evaluating whether the numerical model reproduces the same values with real data. The reproduced indicators and original indicators are compared, and the magnitude of the errors are evaluated.

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A Decentralized Force Controller Synthesis for Compliant Robots Driven by Series Elastic Actuators

Sariyildiz E., Mutlu R., Nozaki T., Murakami T.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 （Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019）     661 - 666 2019年05月

ISSN  9781538669594

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© 2019 IEEE. This paper deals with the decentralized force control problem of compliant robots driven by Series Elastic Actuators (SEAs). The decentralized force control problem of a compliant robot manipulator is transformed into the robust position control problem of a servo system by using Hooke's law and lumping the nonlinear dynamics and unknown disturbances of the robot manipulator into a fictitious disturbance variable. In order to precisely follow the reference force trajectories at joint space, i.e., the position trajectories of the servo systems, the robust controller is synthesized by using Disturbance Observer (DOb) and Sliding Mode Control (SMC). Although the robust force controller can be synthesized by using only SMC, the force control signal may suffer from high control signal chattering as the force reference input is increased. In addition to improving the robustness of force control, DOb significantly suppresses the discontinuous control signal chattering by allowing to decrease the SMC gain. When the proposed decentralized robust force controller is implemented, the compliant robot can precisely track desired force trajectories and safely contact to different environments. The validity of the proposed force controller is verified by giving the simulation results of a redundant robot manipulator.

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Bilateral Control between Manipulators with Different Structure Considering Fluctuation of Equivalent Mass Matrix

Lyu W., Murakami T.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 （Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019）     370 - 375 2019年05月

ISSN  9781538669594

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© 2019 IEEE. This paper proposes the bilateral control method for a pair of manipulators which have different structures considering the fluctuation of an equivalent mass matrix. Bilateral control is one of the methods that controls position and force bidirectionally between two actuators. By using this method, operators can get haptic sensation from the remote environment during teleoperation. When considering the practical situation, the desired structure of robots would be different between the operator and remote sides depending on a task or environment. Therefore, bilateral control between two manipulators with different structure needs to be considered. In the method using Workspace Observer (WOB), conventionally, the nominal value is used for the equivalent mass matrix. However, an error occurs between the nominal and true values of equivalent mass matrix, and this error deteriorates the stability or noise-sensitivity of the system. In addition, it deteriorates the accuracy of the force estimation since Workspace Reaction Force Observer (WRFOB) estimates external force including this error. To overcome this problem, the control system needs to be designed based on the equivalent mass, which fluctuates depending on the posture of manipulators. By using the estimated equivalent mass matrix for WOB, the mass fluctuation can be considered, however, the interference between position control and force control occurs as the equivalent mass is different between the master and slave. Therefore, in the proposed method, Modal space Disturbance Observer (MDOB) with estimated task mass matrix is used to reduce the interference. Experiments were conducted to validate the proposed method.

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Variable Slave Force Gain for Oblique Coordinate Control under the Presence of Time-Delay

Okano T., Ohnishi K., Murakami T.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 （Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019）     249 - 254 2019年05月

ISSN  9781538669594

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© 2019 IEEE. Teleoperation gets a significant attention from the society, and 4ch bilateral control is known as a method to realize the haptics transmission. Its controller is able to achieve the rich haptics transmission, but the performance is degraded under the presence of time-delay due to the interference between the position and force controllers. In particular, its interference becomes larger when position and force scaling are set more than 1 and the mass difference between the master and slave is large. 3ch architecture has proposed to tackle with the performance deterioration when the position and force scaling are set more than 1, but no researches have conducted for considering both the scaling and mass difference. This paper considers the situation that the scaling are set and the mass difference is existed in addition to the time-delay. Oblique coordinate control is utilized, and the superiority of 4ch and 3ch architectures are discussed. The proposal takes the superiority of these two architectures, and its effectiveness was verified through simulations and experiments.

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Sensorless Bilateral Control Using Hall ICs

Akutsu S., Nozaki T., Murakami T.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 （Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019）     243 - 248 2019年05月

ISSN  9781538669594

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© 2019 IEEE. Sensorless bilateral control has been studied to improve fault-tolerance of teleoperation without using torque sensors, position sensors, and other mechanical sensors. However, sensorless control often has less control accuracy due to model errors, parameter variations, and other unexpected factors. Feedback control with some position sensors is practically required for teleoperation. Therefore, this study aims at sensorless bilateral control using Hall ICs. A proposed bilateral control does not necessarily require disturbance observers unlike a conventional method originally using high-resolution sensors. Owing to this advantage, low-resolution sensors are applicable to the proposed bilateral control. Experiments showed that the proposed method succeeded bilateral control using Hall ICs without mechanical sensors, although the conventional control did not work using the low-resolution sensors. Therefore, the proposed method will be able to enhance fault-tolerance of teleoperation systems.

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Grasping Point Estimation Based on Stored Motion and Depth Data in Motion Reproduction System

Sun X., Nozaki T., Murakami T., Ohnishi K.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 （Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019）     471 - 476 2019年05月

ISSN  9781538669594

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© 2019 IEEE. Most countries are running shortage of working force due to the aging population and reduction in the birthrate. Robot manipulators are expected to replace human work. However, it it still difficult for manipulators to do simple tasks such as fruit harvesting, foods cooking or toy assembling. A problem for robotic automation arise in the difficulty in teaching how much force manipulators should use for a task execution. Motion reproduction system, which uses bilateral control to store motion data, is one of a method to teach manipulators motion including position and force. The problem concerning motion reproduction system is that the motion reproducing fails if environment is changed between motion saving phase and motion reproducing phase. Motion reproduction system which can understand and adapt to environment is required. Vision sensor can sense environment. Computer vision is mainly focus on how to classify objects. Vision information is seldom combined with motion control especially force motion. Therefore, I propose a motion reproduction system in which reproduced motion is decided based on several motions and collected depth data. Convolutional Neural Network(CNN) was used to estimate a motion command from a depth image. Saved force data was used to generate labels for training. The label decision is different from conventional Machine learning alzorithm.

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A Control of under Actuated AUV by Nonlinear Controller

Kawamura A., Okano T., Murakami T.

Proceedings of the 2019 IEEE/SICE International Symposium on System Integration, SII 2019 （Proceedings of the 2019 IEEE/SICE International Symposium on System Integration, SII 2019）     295 - 300 2019年04月

ISSN  9781538636152

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© 2019 IEEE. Technologies for machine automation are strongly demanded in some developed countries for achieving various tasks which should be treated by the robot. Autonomous Underwater Vehicles (AUVs) are currently being utilized for scientific and commercial applications. To achieving these tasks, it is required autonomous the guidance and the control systems. Therefore, modeling, system identification and control strategy of these vehicles are still major areas of research and development. Normally, the full actuated AUV is considered for facilitating its control and the disturbance compensation. However, it increases the cost to create and maintain. And thus in author's previous research, an under actuated AUV which still can be controlled when the disturbance exists, was considered to decrease the cost with the same performance as the full actuated one. However, some disturbance effects could not be compensated because of severe nonlinearity of it and the non-holonomic constraint. Therefore, the new control strategy which is considered its nonlinearity, is proposed in this paper and the simulation supports this argument.

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A fusion control of impedance and vibration suppression for a manipulator with flexible base

Mori R., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology （Proceedings of the IEEE International Conference on Industrial Technology）  2019-February   42 - 47 2019年02月

ISSN  9781538663769

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© 2019 IEEE. Accidents caused by a collision between an environment and a robot become a problem, so safety strategies of robots are indispensable. Since the impact force sharply increases at the time of a collision, position-based impedance control which has low responsiveness to the collision can not sufficiently reduce the damage. This paper proposes the manipulator with passive and flexible base for collision force suppression. The proposed flexible base has a rotating structure and it is possible to suppress the collision from any direction when an environment contacts the working manipulator. When a large external force is applied, the variable impedance control according to the strain amount of the base spring in order to avoid the strain limit of flexible base is proposed. Also, when the external force is estimated with force sensorless, the estimation error increases due to the friction model error of the motor, and the position followability deteriorates. Therefore, the contact state is judged by the strain amount of the flexible base, and correction is added to the estimated reaction force, thereby improving the position followability of the impedance control in non-contact.

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Impedance Field Expression of Bilateral Control for Reducing Data Traffic in Haptic Transmission

Nozaki T., Shimizu S., Murakami T., Oboe R.

IEEE Transactions on Industrial Electronics （IEEE Transactions on Industrial Electronics）  66 （ 2 ） 1142 - 1150 2019年02月

ISSN  02780046

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© 1982-2012 IEEE. It is expected that bilateral control will find broad applications such as mobile robot exploration and operations in extreme environments. However, the transmission of vivid haptic sensation requires a rapid data-transfer rate of haptic data due to the short sampling period and high-frequency communication. The objective of this paper is aimed at the traffic reduction of haptic data by exploiting an impedance field equivalence of a standard bilateral control. The proposed approach theoretically clarifies the equivalence of the standard bilateral control and impedance control in terms of haptic transmission. Based on this equivalence, the same performance of a standard bilateral control can be achieved by only communicating the force information that determines the equilibrium position of the impedance control. The validity of the proposed approach is confirmed through both simulations and experiments. The obtained results show that the proposed approach successfully reduced the amount of communicated haptic data without any disadvantages compared with the standard acceleration-based bilateral system. This paper shows novel interpretation that haptic transmission is realized by controlling the equilibrium force, which contributes reducing data traffic in haptic transmission and understanding motion generation.

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Design of bilateral control based on equivalent circuit model

Akutsu S., Nozaki T., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology （Proceedings of the IEEE International Conference on Industrial Technology）  2019-February   1351 - 1356 2019年02月

ISSN  9781538663769

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© 2019 IEEE. Haptic teleoperation has been studied as an attractive technology for a long time. Although the haptic teleoperation has been already realized by conventional methods, their physical meanings are remained vague and unclear. This paper explains bilateral control for the haptic teleoperation using an equivalent circuit model. Owing to the circuit model, which takes into account characteristics of electrical actuators, a control strategy and its physical meanings are clearly illustrated. Torque (force) control and position (velocity) control for the haptic teleoperation can be designed independently because of mode decomposition. Feedback controller design for each control is based on analyses of sensitivity derived from the equivalent circuit. The control strategy derived from the equivalent circuit have been confirmed by experiments and resulted in the haptic teleoperation.

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An approach to air pressure interface for position control of manipulator

Amma Y., Murakami T.

Proceedings of the IEEE International Conference on Industrial Technology （Proceedings of the IEEE International Conference on Industrial Technology）  2019-February   54 - 59 2019年02月

ISSN  9781538663769

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© 2019 IEEE. Nowadays, a low birthrate and longevity are proceeding in developed countries. Due to the low birthrate and longevity, there is a shortage of caregivers. Therefore, an assistance of nursing care is necessary. Also, according to a multidisciplinary advance of robots, robots increase opportunities for operating in environment in which human intervene. Operating a robot in human presence is a dangerous for human. Therefore, a signal transmission between human and robots is necessary. This paper uses a cuff of sphygmomanometer as an interface of signal transmission. This interface is attached to an arm of user and an air pressure of interface is controlled to constant. An error between pressure command and response caused by a muscle bulge of user is regarded as an intention of user. An integration of error is given to a manipulator as a position command. According to this system, the interface user can operate a position of manipulator based on the user's intention.

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Advanced deceleration control considering driving resistance by predicting the position of pedestrians

Nakamura Y., Murakami T.

IEEJ Journal of Industry Applications （IEEJ Journal of Industry Applications）  8 （ 2 ） 334 - 341 2019年

ISSN  21871094

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© 2019 The Institute of Electrical Engineers of Japan. This study aims to realize an automated deceleration system to avoid the collision of a vehicle with a pedestrian. The proposed system can predict a pedestrian’s future position from the current position, and detect the collision probability. Furthermore, the controller employing model predictive control, which can compensate the driving resistance and the modeling error is also proposed. The effectiveness of the proposed method is verified through a simulation and experiment.

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Simultaneous bipedal locomotion based on haptics for teleoperation

Prasanga D., Tanida K., Ohnishi K., Murakami T.

Advanced Robotics （Advanced Robotics）  33 （ 15-16 ） 824 - 839 2019年

ISSN  01691864

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© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group and The Robotics Society of Japan. This paper proposes a novel, simultaneous bipedal locomotion method using haptics for remote operation of biped robots. In general, traditional biped walking methods require very high computational power and advanced controllers to perform the required task. However, in this proposed method, a master exoskeleton attached to the human’s lower body is used to obtain the trajectory and haptic information to generate the trajectory of the slave biped robot in real time. Lateral motion of the center of mass of the biped is constrained in this experiment. Also, it is considered that no communication delay is presented in between the two systems in this experiment, and they are not discussed in this paper. Since a direct motion transmission is used in the proposed method, this method is quite straight forward and a simultaneous walking can be realized at the same time with high performance. Also, it does not require an exact dynamic model of the biped or specific method to plan the trajectory. The gait pattern of the biped is directly determined by that of the human. Also, the operator can feel the remote environment through the exoskeleton robot. Results obtained from the experiments validate the proposed method.

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Multilevel inverter topology using current path change for zero current switching

Sugimoto T., Nozaki T., Murakami T.

IEEJ Journal of Industry Applications （IEEJ Journal of Industry Applications）  8 （ 2 ） 250 - 255 2019年

ISSN  21871094

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© 2019 The Institute of Electrical Engineers of Japan. In motor drive applications, a high switching frequency is required to mitigate current harmonics, which cause a copper loss. However, the high switching frequency makes the switching loss large. Hence, some switching loss reduction techniques have been studied in the past. These techniques have some problems. This paper proposes a multilevel inverter topology for switching loss reduction. Because of provision of multiple current paths, the proposed inverter realizes the zero current switching. Consequently, a loss of the whole system including an inverter and motor can be reduced with a higher switching frequency. The switching loss of the proposed inverter is smaller than that of the conventional one. It was verified that the proposed inverter has some advantages at high switching frequency, through calculations.

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Control Structure Determination of Bilateral System based on Reproducibility and Operationality

Tanida K., Okano T., Murakami T., Ohnishi K.

IEEJ Journal of Industry Applications （IEEJ Journal of Industry Applications）  8 （ 5 ） 767 - 777 2019年

ISSN  21871094

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© 2019 The Institute of Electrical Engineers of Japan. The 4ch bilateral control is a teleoperation method that transmits the position and force information between the master and slave, and the reproducibility and operationality are often used to evaluate it. Conventionally, the reproducibility and operationality have been utilized only for performance evaluation, although many controllers based on the 4ch bilateral control scheme have been proposed. Therefore, the aim of this paper is to determine the controller structure based on the target reproducibility and operationality in advance. The contribution of this paper is to develop an appropriate controller from the reproducibility and operationality through numerical computations and analyses. The structure of the proposed controller is verified through simulations and experiments.

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Design of iterative learning control for force control considering environmental impedance

Fukui M., Akutsu S., Okano T., Nozaki T., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society （Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society）     4569 - 4574 2018年12月

ISSN  9781509066841

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© 2018 IEEE. In this paper, a new approach for high-precise force control in repeated tasks is proposed. In the general force control, the feedback control tends to be used for a matching the output force to the desired force safely. However, when the feedback control is used, the input of the plant does not change until the error is observed. The characteristic makes reactivity bad. In the position control, the model-based feedforward control is often used to solve this problem. However, the model-based feedforward control cannot be used in force control due to the difficulty of making the accurate model. The main reason of this problem is the uncertainty of the environmental impedance. Owing to the uncertainty, the model-based feedforward control cannot work properly. To solve this problem, Iterative Learning Control (ILC) is used in this paper. ILC does not require the accurate model, and it is able to match the output force to the desired one through repeated trials. However, the convergence condition in force control has not been analyzed until now. In this paper, by taking account of the environmental impedance of the object, a new convergence restriction is proposed. Under the proposed condition, the force control in repeated tasks becomes more precise. The procedure was demonstrated on simulations.

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Verification of the knee exoskeleton controller using novel gait phase detection method

Tawaki Y., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society （Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society）     3304 - 3309 2018年12月

ISSN  9781509066841

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© 2018 IEEE. Gait motion is the essential function for human being. Some diseases make it difficult for people to walk. Walking assist robot has been developed to assist gait motion for disabled people. Knee Exoskeleton is one of the walking assist robots. Knee Exoskeleton generates the assist torque for knee flexion or knee extension. The direction of the assist torque is controlled by the gait phase detection method. However, the conventional robot interferes with human intention because it generates flexion torque consistently in stance phase. In early stance phase, the user wants assist torque to support knee extension, but he wants knee flexion assist torque in late stance phase. The conventional controller does not detect late stance phase. In the previous study of the author, the novel gait phase detection algorithm is proposed to distinguish late stance phase. In this research, the novel algorithm is introduced for the proposed controller. A subject walks on the treadmill while wearing the knee exoskeleton. In the experiment, the exoskeleton is controlled by the conventional controller and the proposed controller. EMG of the popliteal muscle during gait motion is analyzed to evaluate whether the proposed controller succeeds to prevent interference with user's intention. Through the experiment, it is verified that the proposed controller succeeds to decrease the EMG of knee muscle by distinguishing early stance phase and late stance phase.

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Selective wireless power transfer via magnetic resonant coupling by using variable impedance circuit

Nakagawa T., Sugimoto T., Nozaki T., Murakami T.

Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society （Proceedings: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society）     4834 - 4839 2018年12月

ISSN  9781509066841

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© 2018 IEEE. Recently, Wireless Power Transfer (WPT) via Magnetic Resonant Coupling is especially focused around the world. Since a space will have a lot of devices in the future, WPT considering multiple devices will be required. It is important to consider not only power transfer efficiency but also power distribution when power is wirelessly transferred to multiple devices. The amount of received power in a receiver depends on the impedance of the receiver and the ratio of power distribution has the relation to the impedance. Conventional WPT system requires a few controllable repeaters and the large size of the receiver. In this paper, a variable impedance circuit for power distribution is proposed. Using the proposed circuit controllable by DC voltage, the problem for the conventional system is solved. In the future when WPT is popular, the circuit realizes electrically controllable power distribution.

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