Details of a Researcher - Ohnishi, Kouhei

Papers - Ohnishi, Kouhei

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An Approach to Architecture Design of Bilateral Control System based on a Layer Structure

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

IEEJ Journal of Industry Applications (IEEJ Journal of Industry Applications) 9 ( 4 ) 318 - 330 2020.07

ISSN 21871094

©2020 The Institute of Electrical Engineers of Japan. A bilateral control system aims at realizing a fine haptic transmission between a human operator and a remote environment object. Such a system is expected to realize multiple requirements in practical applications, and the architecture design based on a layer structure has to be considered. This paper treats a surgery robot system as an example, and its system has two requirements: "large workspace"and "fine haptic sensation". Using the conventional bilateral control system to realize these requirements simultaneously is difficult because mechanical and control designs are separately discussed. At the same time, a system that has multiple requirements such as a fine/coarse system is often designed only using position information. This study proposed to consider not only mechanical/control design but also the position/force information simultaneously from the perspective of an architecture design. The proposed architecture decomposes the functions into each motor/robot by defining roles and combining each role in the layer structure. The advantage of the proposal is that a complex system can be designed as a entire by combining multiple sub-functions that can be simply designed. As a result, the surgery robot system is designed by considering its requirements, and the experiments are carried out to verify if the requirements are satisfied. Â

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Automatic grasping position adjustment for robotic hand by estimating center of gravity using disturbance observer

Yajima S., Shimono T., Mizoguchi T., Ohnishi K.

IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM (IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM) 2020-July 595 - 600 2020.07

ISSN 9781728167947

© 2020 IEEE. Recently, the demand for collaborative robot is increasing. Most of them are smaller to conventional industrial robots. In order to support humans in various field, it is required that they acquire flexible and dexterous motions. The soft motion based on force control will be one of keys to realize such a motion. However, the introduction of force control leads to a decrease in the rigidity of the system, which results in a decrease in positioning accuracy. This poor position tracking accuracy could cause the drop of grasped object, and it leads property damage accidents. Recently, there have been much discussions about the responsibility, handling, and risk management of accident caused by robots. As a solution, we propose the automatic grasping position adjustment for robotic hand to prevent the grasped object from falling. By observing the center of gravity and adjusting its position, the system attempts to shift unstable grasping position to stable position. This paper shows the automatic grasping position adjustment method. Then the performance of proposed method is verified by using actual robotic hand.

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Development of small-diameter haptic flexible gripping forceps robot

Matsunaga T., Ohnishi K., Wada N., Kitagawa Y.

Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) (Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi)) 211 ( 1-4 ) 47 - 54 2020.06

ISSN 04247760

© 2020 Wiley Periodicals, Inc. Robotic technologies are being increasingly utilized for medical treatments to support surgeons and reduce the burden on patients. Flexible endoscopic surgical systems with an endoscope and flexible forceps robots are state-of-the-art devices that are expected to realize more difficult and less invasive surgery. Surgeons teleoperate these flexible forceps robots as their own hands and conduct various medical tasks. The wire-driven mechanism is applied to many flexible forceps robots to transmit the driving force to the tip of the robots in a narrow space. However, the flexible structure makes it difficult to control the wire-driven robots and implement the haptic technologies to realize safer surgery. In this paper, a force sensor-less, small-diameter flexible forceps robot with the ability to transmit haptic sensation is presented. The driving part at the tip of the flexible part, composed of a small actuator with a reduction mechanism, realizes the miniaturization of the robot. Haptic information is estimated by low-resolution position information. The bending of the flexible part with electric wires does not deteriorate the performance of the end effector. The performance of the haptic flexible forceps robot is evaluated through experiments.

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Disturbance Observer-Based Robust Control and Its Applications: 35th Anniversary Overview

Sariyildiz E., Oboe R., Ohnishi K.

IEEE Transactions on Industrial Electronics (IEEE Transactions on Industrial Electronics) 67 ( 3 ) 2042 - 2053 2020.03

ISSN 02780046

© 1982-2012 IEEE. Disturbance observer (DOB) has been one of the most widely used robust control tools since it was proposed by Ohnishi in 1983. This paper introduces the origins of DOB and presents a survey of the major results on DOB-based robust control in the last 35 years. Furthermore, it explains DOB's analysis and synthesis techniques for linear and nonlinear systems by using a unified framework. In final section, this paper presents concluding remarks on DOB-based robust control and its engineering applications.

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Development of a Multi DOF Haptic Robot for Dentistry and Oral Surgery

Iijima T., Matsunaga T., Shimono T., Ohnishi K., Usuda S., Kawana H.

Proceedings of the 2020 IEEE/SICE International Symposium on System Integration, SII 2020 (Proceedings of the 2020 IEEE/SICE International Symposium on System Integration, SII 2020) 52 - 57 2020.01

ISSN 9781728166674

© 2020 IEEE. There exist many dental surgery such as orthognathic surgery and an implant operation. Jaw deformity is one of the dental diseases such as an abnormality of occlusion and facial distortion in the shape. To treat jaw deformity, the osteotomy is carried out by human hands. However, drilling a jawbone accurately by oral surgeons is difficult. Recently, surgical robots are attracting attention in the medical field. The researches of surgery supporting systems have been carried out. They have possibilities to avoid unexpected accidents in the surgery, a hands shake and so on. The improvement of the minimally invasive surgery can be expected, thanks to robotic technology. The purpose of this research is the design and development of master-slave dentistry and oral surgery assisting robot. By implementing acceleration based bilateral control, haptic information can be communicated. Moreover, the proposed robot has the serial-parallel hybrid mechanism that can obtain the advantages of a serial mechanism and a parallel mechanism. In this paper, the mechanism of the proposed robot is explained and the performance of the proposed robot is validated by experiments.

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Selection of required controller for position-and force-based task in motion copying system

Okano T., Oboe R., Ohnishi K., Murakami T.

Journal of Robotics and Mechatronics (Journal of Robotics and Mechatronics) 32 ( 1 ) 113 - 127 2020

ISSN 09153942

© 2020, Fuji Technology Press. All rights reserved. With the remarkable development of related technologies, the number of robots has been gradually increasing and their presence is becoming much more familiar in our daily lives. The motion copying system (MCS) is utilized as the method for conducting some tasks by robots. This system enables tasks to be reproduced when the environmental conditions are not changed. The task reproduction performance is degraded when environmental variations occur, and human-like adaptable motion is expected to be developed in the MCS. This study reveals the dominant element of motion, and the control strategy is varied at each time in each axis by considering the task realization. The flexibility of motion is learned from both the operator and the task implementation. The task reproduction experiments by MCS are conducted to verify the effectiveness of the proposal.

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Multimodal haptic display for virtual reality: A survey

Wang D., Ohnishi K., Xu W.

IEEE Transactions on Industrial Electronics (IEEE Transactions on Industrial Electronics) 67 ( 1 ) 610 - 623 2020

ISSN 02780046

© 1982-2012 IEEE. Human haptic perception system is complex, involving both cutaneous and kinesthetic receptors. These receptors work together and enable human to perceive the external world. To simulate immersive interaction with virtual objects in virtual reality scenarios haptic devices are desired to reproduce multiproperties of virtual objects, support multigestures of human hands to perform fine manipulation, produce haptic stimuli for simultaneously stimulating multireceptors (including cutaneous and kinesthetic receptors) of human haptic channel, and thus invoke realistic compound haptic sensations. In recent years, such multimodal haptic devices have emerged. In this paper, we survey the latest progress on multimodal haptic devices, identify the gaps, and put forward future research directions on the topic.

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Development of a force sensorless percussion device for rationalization of generator inspection

Kuwahara H., Mizoguchi T., Shimono T., Ohnishi K.

Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering (Seimitsu Kogaku Kaishi/Journal of the Japan Society for Precision Engineering) 86 ( 1 ) 120 - 125 2020

ISSN 09120289

© 2020 Japan Society for Precision Engineering. All rights reserved. For non-deconstructive generator inspection, robots which can crawl in a gap of a rotor and a stator have been developed. Since the robot should be enough thin to crawl in the gap, the inspection devices also need to be compact. Percussion is a method to detect the stator wedge looseness. Since echo vibration excited by striking the target is analyzed in this method, the device requires two functions: A striking function and a sensing function. Basically, two devices such as a hammer and a microphone are utilized to achieve the functions. In this paper, a percussion device with the force control technique and the inspection method to detect the stator wedge looseness are proposed. Since the proposed device can not only control the striking force but also sense the reaction force by itself, it is expected that the device can be compact. Moreover, in the proposed method, inner stator slot model parameters are estimated by analyzing the gain characteristics of the proposed device. Then, the amount of the stator wedge looseness is evaluated based on the model parameters. The validity of the proposed percussion device and the inspection method are evaluated through the experiments.

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Development of a microsurgery-assisted robot for high-precision thread traction and tension control, and confirmation of its applicability

Hangai S., Nozaki T., Soma T., Miyashita H., Asoda S., Yazawa M., Sato K., Kawana H., Ohnishi K., Kobayashi E.

International Journal of Medical Robotics and Computer Assisted Surgery (International Journal of Medical Robotics and Computer Assisted Surgery) 17 ( 2 ) 2020

ISSN 14785951

© 2020 The Authors. The International Journal of Medical Robotics and Computer Assisted Surgery published by John Wiley & Sons Ltd. Background: Microsurgery requires high skills for suturing using fragile threads, often within narrow surgical fields. Precise tension is required for good healing and to avoid the risk of thread breakage. Methods: To meet the demands, we developed a novel assist robot utilizing high-precision sensorless haptic technology. The robot adopts a cable-driven mechanism to maintain a distance from the surgical area and enhances compatibility with surgical equipment such as microscopes. The robot performance was verified through in vitro and in vivo experiments using a rat model. Results: The realization of precise tension control was confirmed in both experiments. In particular, in the in vivo experiments, the developed robot succeeded to produce a knot with an accurate tension of 0.66% error. Conclusions: The developed robot can realize to control traction force precisely. This technology might open up the window for a full assist robot for microsurgery with haptic feeling.

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Reconstruction of pitchfork bifurcation with exogenous disturbances based on equivalent-input-disturbance approach

She J., Yin X., Wu M., Sato D., Ohnishi K.

Nonlinear Dynamics (Nonlinear Dynamics) 102 ( 4 ) 2699 - 2709 2020

ISSN 0924090X

© 2020, Springer Nature B.V. Reconstructing a pitchfork bifurcation that is destroyed by an exogenous disturbance is important to control it. This paper extends the equivalent-input-disturbance (EID) approach to solve the problem of reconstructing a pitchfork bifurcation when there is an exogenous disturbance for the first time. A nonlinear term and a bifurcation parameter are designed in the system to reconstruct the pitchfork bifurcation. The bifurcation characteristics of the equilibriums of the system are analyzed by exploring the features of the EID-based system. This provides us analytic solutions for a system with a degree higher than four for the first time. Unlike other pitchfork-bifurcation control systems, the EID-based control system only rejects the disturbance and retains the nonlinearity. Numerical examples demonstrate the effectiveness of the presented method and show its superiority over others. The robustness of the reconstruction with respect to measurement noise and control of a pitchfork bifurcation are also shown by the examples.

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A study on safe forceps grip force for the intestinal tract using haptic technology

Yatabe K., Ozawa S., Oguma J., Hiraiwa S., Tomita S., Matsunaga T., Togashi N., Yokoyama M., Shimono T., Ohnishi K.

Minimally Invasive Therapy and Allied Technologies (Minimally Invasive Therapy and Allied Technologies) 31 ( 4 ) 573 - 579 2020

ISSN 13645706

Purpose: The present study used haptic technology to determine the safe forceps grip force for preventing organ damage when handling the intestinal tract. Material and methods: The small intestines of ten male beagle dogs (weighing 9.5–10 kg) were grasped with the entire forceps for one minute; the small intestines were then pulled out of the forceps and evaluated for damage. The force at which the shaft inside the forceps was pulled to close the tip of the forceps was defined as the grip force. Small intestine damage was classified into macroscopic (serosal defects, hemorrhage, hematomas, grip marks) and microscopic (damage layer to the mucosa, submucosa/muscularis mucosa, inner orbicularis muscle, external longitudinal muscle, serosa/subserosa). Grip marks and damage layer to the serosa/subserosa have been considered as acceptable safety margins when grasping the small intestines of beagle dogs. Results: The macroscopic findings showed that the maximum grip force that produced a 0% incidence of hemorrhage and hematoma was 15 N. At the microscopic level, the maximum grip force that produced a 0% incidence of external longitudinal muscle injury was 15 N, respectively. Conclusions: A grip force of 15 N does not damage the small intestines of beagle dogs.

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Haptics-Led Innovation for Coming Society

Ohnishi K., Nozaki T., Saito Y., Shimono T., Mizoguchi T.

Technical Digest - International Electron Devices Meeting, IEDM (Technical Digest - International Electron Devices Meeting, IEDM) 2019-December 2019.12

ISSN 9781728140315

© 2019 IEEE. Contact task by artifact has been an unsolved problem since its starting in 1940's. After many RDs including the early works in US and the other countries, bilateral control is a strong solution for this issue. Quality of tactile sensation heavily depends on transparency between master and slave. The Hadamard transformation designed in acceleration space gives the high transparency. The real haptics based on this transformation brings not only the vivid sensation of contact task but also two important applications into the coming society. One is a high-quality tele-operation and the other is a playback of skilled motion by human. The real haptics is a key concept in 21st century where QOL should be the fundamental basis of the society. The paper shows some examples of experiments.

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A Controller Design Method of Bilateral Teleoperation for Velocity Control Driver

Saito Y., Shimmyo S., Nozaki T., Ohnishi K.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference)) 2019-October 3585 - 3590 2019.10

ISSN 9781728148786

© 2019 IEEE. Bilateral control can realize haptic feedback required for securing safety and diversity in teleoperation by robots. Since conventional approaches are based on a servo controller which has high-performance current control or torque control, there is a barrier for advancing into society. The objective of this paper is to propose a design method of the bilateral controller using velocity control driver to achieve haptic feedback. The velocity control driver such as an inverter is widely used in the industrial fields. In the proposed method, a reaction force observer modified for velocity control driver is used to estimate environmental reaction force. The control system is constructed by applying the concept of hybrid control which controls velocity and force independently, and the concept of modal space which separates motions into functions is also applied. Furthermore, the proposed bilateral controller is designed based on the ideal conditions of operationality and reproducibility. The validity of the proposal is verified through a simulation and an experiment. The obtained results show that the proposed controller successfully achieves the teleoperation with haptic feedback using velocity control driver.

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Force Sensorless Haptic Probe Driven by Large Circular Linear Motor for Haptic Rendering

Matsunaga T., Shimono T., Asai H., Ohnishi K.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference)) 2019-October 657 - 662 2019.10

ISSN 9781728148786

© 2019 IEEE. Utilization of haptic sensation for robots has advantages in various fields. Haptic rendering which is a technology to contact with virtual objects will be useful for virtual reality and simulation devices in medical and industrial fields. To realize these applications, technologies to extract environmental information and reconstruct virtual environments have been studied. In this paper, a force sensorless probe to obtain environmental information for a haptic rendering system is presented. Environmental information such as shape and stiffness is automatically recorded by the haptic probe driven by linear motors. By utilizing a large circular linear motor which has circular motion, haptic information of environments which have a two dimensional shape can be extracted by the device with simple structure. In experiments, the haptic probe contacts with an environment which has two kinds of stiffness. The recored environmental information is processed and rendered to an operator by a XY table composed of two linear motors. Experimental results show that the system can capture environmental information and it can be used for haptic rendering.

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Bandwidth Expansion of Bilateral Teleoperation Based on Synergy of Observer Gain and Velocity Feedback Gain

Shimmyo S., Saito Y., Nozaki T., Ohnishi K.

IECON Proceedings (Industrial Electronics Conference) (IECON Proceedings (Industrial Electronics Conference)) 2019-October 3597 - 3602 2019.10

ISSN 9781728148786

© 2019 IEEE. Bilateral control is getting much attention as a key technology in teleoperation. A reproducibility is one of the performance indices of bilateral teleoperation, and four-channel acceleration-based bilateral control (4ch ABC) which has a high reproducibility with wide bandwidth enables operators to feel environmental impedance, clearly. Both position control and force control are required for the 4ch ABC, and a PD controller and a P controller are often utilized with a disturbance observer (DOB) and a reaction force observer (RFOB). This paper discusses how operators can feel environmental impedance with wide bandwidth in the 4ch ABC. A damping ratio of a PD controller has been, conventionally, set about 1 by imitating a traditional design principle of servo control. This paper theoretically reveals that a velocity feedback gain of a PD controller affects a bandwidth of reproducibility as a synergy with observer gains of a DOB, and a PD controller using a high velocity feedback gain is introduced. The validity of the theoretical analysis is confirmed by simulations and experimental results.

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Communication delay compensation for precise force matching in teleoperation

Tojo N., Tashiro T., Yokoyama M., Shimono T., Oboe R., Mizoguchi T., Ohnishi K.

IEEE International Conference on Industrial Informatics (INDIN) (IEEE International Conference on Industrial Informatics (INDIN)) 2019-July 553 - 556 2019.07

ISSN 9781728129273

© 2019 IEEE. Teleoperation technology is widely employed in the fields of industry and human support. Bilateral control, which is one of the possible methods to achieve teleoperation, enables mutual transmission of operational force of an operator and reaction force from remote environment. However, teleoperation often involves non negligible communication delays, due to the limits of the communication networks. As a countermeasure against communication delays, bilateral control using a force-control-based communication delay compensation has been proposed. This approach is effective in stabilizing system behavior and in maintaining the force states, so that operator's operational force and reaction force from environment can act in pairs and opposite direction, even during contact tasks. In this paper, we introduce a bilateral control that makes use of a force-control-based communication delay compensation, with a new control structure in which structural redundancy of conventional system is removed. The proposed bilateral control system demonstrates through experiments a stable teleoperation and an accurate force matching performance through experiments.

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Multi DoF Robotic Platform using Large Circular Linear Motors for Haptic Surgical Robots

Matsunaga T., Asai H., Shimono T., Ohnishi K.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics) 2019-June 1174 - 1179 2019.06

ISSN 9781728136660

© 2019 IEEE. Reduction of burden on patients and surgeons is an issue in the medical field. Robotic surgery utilizing teleoperation robots is a method to realize minimally invasive surgery and support surgeons. Structure of surgical robots can be divided into robotic surgical tools and robotic platforms. Robotic platforms have multi degree of freedom (DoF) arms to mount robotic surgical tools and functions to change workspace of the end effector of robotic surgical tools by its large movable range. Therefore, large output to support robotic surgical tools, precise motion, and enough movable range are necessary for the robotic platforms. In this paper, a novel multi DoF robotic platform with two arms and a robotic surgical tool are presented. The robotic platform consists of large circular linear motors which can generate large output force and realize remote center of motion. As the robotic surgical tool, a master-slave three DoF forceps robot which has ability to transmit haptic sensation to operators is developed. In an experiment, the robotic platform with the slave of the three DoF forceps robot is teleoperated to validate the performance of the robots.

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Design and Analysis of Core-less Multi-layered Axial Motor

Soneda C., Asai H., Hatta Y., Shimono T., Ohnishi K.

IEEE International Symposium on Industrial Electronics (IEEE International Symposium on Industrial Electronics) 2019-June 267 - 272 2019.06

ISSN 9781728136660

© 2019 IEEE. This paper proposes a new multi-layered axial motor. It is designed as a core-less motor. A core-less motor does not generate cogging torque but generates less torque than a motor including core. In the proposed motor, the multi-layered structure is applied in order to improve torque. Multi permanent magnet layers and multi coil layers are arranged alternatively in the axial direction. Because flux density reaching coil layers is improved by the multi-layered structure, torque is improved. By 3D finite element method analysis, the relationship between torque and the ratio of permanent magnet to coil is analyzed. The relationship between torque and the number of layers is analyzed. Moreover the relationship of the outside diameter between the permanent magnet layer and the coil layer is analyzed. Based on the analysis, the experimental model of the multi-layered axial motor is designed.

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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 2019.05

ISSN 9781538669594

© 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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Experimental Study on Bilateral Control System under Different Wireless Communication Methods

Mizoguchi T., Kokubun G., Yamaguchi N., Shimono T., Ohnishi K.

Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019 (Proceedings - 2019 IEEE International Conference on Mechatronics, ICM 2019) 31 - 36 2019.05

ISSN 9781538669594

© 2019 IEEE. This paper examines relationship between haptic sense transmission versus wireless network communication. Network communication is a big issue in haptics research area. It is well studied that time-delay, jitter, and packet-loss deteriorates the performance of haptic sense transmission. Transparency is well known evaluation criteria to examine the performance of haptic transmission. The uniqueness of this paper is that the evaluation is examined in real wireless communication environment. The throughput in the system depends on several different disturbances in wireless communication. The paper examines the performance of haptic system from the aspects of transparency. Series of experimental results supports the paper.

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