Robots are being developed to perform tasks in homes and factories autonomously. Several studies have examined motion generation based on haptic information, and some studies consider the environment as physical property information. However, there is a trade-off between the accuracy and the time required for the physical property estimation. Therefore, in this study, we propose a method for estimating physical properties based on training the relationship between the two estimation models. The first is a fast sequential estimation model, and the second is a highly accurate posterior estimation model. Training the relationship between the two models makes highly accurate sequential property estimation possible. Validation results showed improved accuracy of property estimation for learning samples and some untrained samples.

This paper proposes a novel online motion modification method in motion reproduction system. Motion reproduction is used to reproduce human motion saved through bilateral control. Bilateral control is a teleoperation which can transmit both position and force. Human judgement is needed for compensating the saved motion when the environment is different. However, conventional motion reproduction system only relies on saved motion or environment in slave side. Therefore operators in master side cannot modify the motion after motion has been saved. Instead of just reproducing the motion data, the proposed method adds master system at motion reproduction phase so that an operator can modify the motion. If the master system is simply added to motion reproduction system, the operator's motion and saved motion will interfere each other. Therefore, we propose to use weightings to suppress the interference. Simulated results validates the effectiveness of the proposal.

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.

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.

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.

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.

In this paper, friction-reduced scaling bilateral control system for micro force transmission is proposed. Recently, demand for micro manipulation is drastically increasing in the fields of medical or biological science. In order to support micro manipulation, many researchers are trying to apply force feedback to the manipulation. One of the methods is bilateral control with Reaction Force Observer(RFOB). Bilateral control system is composed of a master robot and slave robot. Slave robot tracks master robot's motion and transmits reaction force to operator at master side. In the conventional bilateral control system, if reaction force is smaller than frictional force of machine structure, operator cannot distinguish the slight reaction force at hand. In this paper, actuator is supported by fiber to reduce the frictional force. Furthermore, disturbance arisen by fiber tension is modeled, and compensated. Experiments are conducted to validate the proposal.

Hand recovery process is a major issue in the rehabilitation field as hands are vital to perform most daily activities. This paper presents the design and evaluation of a one actuated degree-of-freedom exoskeleton finger using flexible actuator to assist patients in rehabilitation process and more specifically in tendon recovery protocols. The control strategy based on the motion-copying system is used to be able to take advantages of the sensation of the patient. The wearability and adaptability of the device are improved, compared to other specific devices, mainly by the use of remote actuation and light-weight materials. Evaluation of the device in terms of wearability, adaptability, repeatability and accuracy of the position estimation are conducted. All these criteria are confirmed. The next step is to test the device in actual recovery protocols to evaluate its efficiency.

Minimally invasive surgery (MIS) has many benefits, e.g., unnecessary trauma and blood loss can be minimized by opening tiny surgery scars, recovery process of patients can be lessened, and the possibilities of complications can be decreased. The natural orifice transluminal surgery (NOTES) is one of the MIS surgical methodologies. NOTES surgery is performed using an endoscope. This methodology does not rely on making holes to patients' body to insert the medical instruments. Although some medical robots for NOTES have been proposed, current robots mainly suffer from the absence/limitation of haptic feedback to the surgeon's hands. In order to overcome this problem, this paper proposes electro hydraulic transmission system (EHTS) based forceps. The EHTS is a remote actuation system using fluid energy. By using the EHTS, the classical position and force transmission losses will not be influenced by the tube's shape. The validity of the proposal and its advantages have been experimentally verified and presented in this paper.

Master-slave surgical robots have been studied and developed to support surgeons. Robotic functions such as motion scaling and hand shaking correction can extend the ability of surgeons. However, some problems are remaining in robotic surgery. Operation time which can become the burden to surgeons is still long. Surgeons must assess the situation, decide the next task correctly, and achieve tasks precisely in long operation. By conducting a part of surgical tasks by automatic motion of surgical robots, the burden to surgeons can be reduced. However, surgical tasks require skill of surgeons. Therefore, human skill must be incorporated in robotic motion. In this paper, a teleoperation system to conduct a ligation task by both the teleoperation and the automatic motion is presented. The teleoperation system is composed of haptic forceps robots implementing the motion reproduction system which is a method to preserve and reproduce human motion by a master-slave system. A ligation task is achieved by the bilateral teleoperation and the reproduced motion in the experiment. The saved motion and the reproduced motion are evaluated to validate the usefulness of the teleoperation system implementing the motion reproduction system.

This paper aims to develop the method for identifying human and environmental impedances with information in the frequency domain by using bilateral control system. In the conventional method, a sinusoidal wave is added to the common mode of bilateral control system, however, this method cannot extract haptic information in frequency domain. Human impedances are assumed to change every moment, and the identification method of impedance is strongly desired to develop. In this paper, low-pass filtered M-sequence signal is added to the bilateral control system for identifying both human and environmental impedances with information in the frequency domain. Experiments were conducted for verifying the effectiveness of the proposed method.

In this paper, motion-reproduction system for picking by multiple-DoFs manipulator with a stereo camera is proposed. The conventional motion-reproduction is able to pick different sized objects because of considering force in the control system. However, the conventional system has difficulty in picking the positional changed objects in motion-reproduction. The proposed method compensates the positional fluctuation of picking objects by image processing information and reproduce saved motion successfully. The superiority of proposal is confirmed through experiments. In the experiment tomato and a toy strawberry was used for picking by multiple-DoFs manipulator. The manipulator with proposed method picked the object successfully.

This paper proposes a haptic prosthetic hand to realize intuitive operation for upper limb amputees. In the conventional myoelectric prostheses, it was hardly unable to control the grasping force precisely or to grasp an unevenly shaped object flexibly. In this paper, development of haptic prosthetic hand is achieved, which realizes intuitive operation by the following two functions: first, is the transmission of force sensation to the master interface attached to the healthy part of the body, second, is an adaptation to the shape of an object with flexibleness. The developed haptic prosthetic hand has multi degrees of freedom (DOFs), and the master interface has a limited number of DOF. Therefore, to control the multi-DOFs haptic prosthetic hand by a simple operation of the master interface, different DOF bilateral control is implemented as a control method. Haptics is used to realize intuitive operation, and the proposed variable compliance control is used for environmental adaptation. These functions enable to replace the force sensation of the missing hand, by any remaining healthy part of the body. Experiments were conducted to evaluate the function of the developed haptic prosthetic hand.

In medical field, teleoperation robots for surgery have been studied and developed to support surgeons. Surgical tasks such as needle insertion and suturing are realized by multi degree of freedom (DoF) forceps robots which are a component of a surgical robot. Besides, surgical robots have some advantages such as automation of tasks to reduce the burden to surgeons. Motion reproduction system is a method to automate tasks. The haptic data is used as the data of human motion for motion reproduction system. However, realization of tasks by using multi DoF robots as a motion reproduction system is still difficult. In this paper, in order to realize support for surgeons by automatic motion, needle insertion is realized by the haptic surgical robot composed of multi DoF haptic forceps robots. Experimental results show that the motion of operator was reproduced by using the haptic data, and automatic needle insertion based on motion reproduction system was achieved.

Several technological solutions have ben recently proposed for fingers rehabilitation in patients who were affected by a stroke, in particular for those who cannot generate the finger force but with preserved sEMG signals. In fact, a very promising approach uses a robot rehabilitation system controlled through sEMG signals. However, this system has two main problems: 1) the placement of electrodes is made manually and this could bring to a non-optimal detection of signals; 2) the cost of treatments is very high, mainly due to the usage of single-use, dispodsable electrodes. Our proposal is to use a robot rehabilitation system with a low-cost armband instead of standard electrodes. The armband has 8 sEMG sensors and a 9-DoF inertial sensor, it has electrically safe setup with low voltage battery and Bluetooth protocol. Moreover it is a very low cost and reusable equipment. The validity of the proposal was confirmed through experiments.

Functional recovery for paralyzed patients is realized by repetition of trainings with advice from the therapist. However, in clinical practice, output function of patients is evaluated by qualitative way. For effective training, therapists must quantitatively evaluate the patient's limbs function. To improve this matter, evaluation method of human motion using mechanical power factor is proposed in this study. “Power factor” has also been used in the electrical system, it can be applied to the mechanical system based on an analogy. In electrical system, power factor represents the percentage of power that is effectively consumed by the load impedance. By using mechanical power factor, impedance characteristics of upper limbs can be acquired. This paper describes the concept of power factor in mechanical system and the evaluation method of upper limb function by using mechanical power factor.

This paper proposes a novel, simultaneous bipedal locomotion method with the use of human skill of walking, to increase the performance of walking of the biped robot. Traditional walking methods require high computational power and advanced controllers to realize bipedal walking. In this proposed method, an exoskeleton attached to the human's lower body is used to obtain the joint information and the obtained joint information is then replicated on a biped robot in real time. The lateral motion of the center of mass of the biped is constrained in this experiment and is not discussed in this paper. Since a direct motion transmission is used in the proposal, this method is quite straight forward and a simultaneous walking can be realized at the same time with a high performance. Also, it doesn't require any dynamic model of the biped or specific trajectory planning method. The gait of the biped is directly determined by that of the human. Therefore, this method can copy the motion of human walking to a biped. Results obtained from the experiments validate the proposed method.

In recent years, the demand for technique to transmit the touching sensation is increasing in a medical field. This paper shows that Voice Coil Motor (VCM)-based haptic system enables operators to grasp and manipulate a small and fragile environment with tactile sensation. Author proposed that bilateral control between different degree-of-freedom without position controller system attain the grasping task and the manipulation task simultaneously. However, the system without the position controller cannot position accurately because of the friction. Thus, bilateral control between different degree-of-freedom with position controller system accomplishing the grasping task and the manipulation task simultaneously by updating command is proposed. In addition, the proposed method based on both oblique coordinate control and decoupling method using MDOB are verified.

This paper proposes a novel design method of disturbance observer (DOB) and reaction force observer (RFOB) for acceleration-based bilateral control (ABC) utilizing DC brushed motor (abbreviated as DC motor later). ABC is one of the control method to enable the transmission of haptic sensation between master and slave robots. In order to transmit highly precise haptic sensation, both DOB and RFOB are used for ABC. Conventionally, in case of utilizing these observers, a motor has been considered to be driven by an ideal current source by utilizing the motor driver which has a current minor loop. The gain of current minor loop must be set large value in order to improve current tracking performance. However, there is a limit to increase the gain since it is affected by the the time delay of current minor loop. Therefore, this paper proposes design methods for DOB and RFOB without using current minor loop. Proposed observers estimate disturbance force from acceleration reference, voltage reference, and acceleration response by utilizing novel nominal model for DC motor. Proposed method can improve disturbance estimation performance. Moreover, by utilizing proposed method, DC motor can be controlled without using current sensor. The validity of proposed methods are experimentally verified.

This paper presents the master-slave system which is composed of multi degrees of freedom (DoF) forceps robots. In minimally invasive surgery, there are some advantages for patients because incision is small. However, it is difficult for surgeons. Therefore, in order to support surgeons, surgical robots are studied and developed. Although conventional surgical robots have high position accuracy, the transmission of force sensation is not adequate. Therefore, two types of the five DoF surgical robot are developed to transmit force sensation. Force sensation can be transmitted by bilateral control. In this paper, the master-slave system with bilateral control is constructed. Two types of the five DoF surgical robot are used as two human hands. In the experiments, simple tasks are carried out and the transmission of force sensation is validated.

This paper proposes a novel viewpoint of the bilateral control with time delay in terms of modal space and the control method to track position and return force information from the slave to the master well. The bilateral control is characterized by a remote control, which return force information to the local site. Time delay is one of the problems of the bilateral control system, because it degrades the performance and stability of the control system. Various methods for the problems about time delay have been proposed. However, in these methods, the control goals in bilateral control in the presence of time delay have been not taken into account clearly or been not set properly. Therefore, this paper sets novel control goals of bilateral control with time delay in terms of modal space and the control method in which the slave position tracks the master position and the slave's force return to the master well. The validity of the proposed method is demonstrated experimentally.

Bilateral control system makes it possible to transmit haptic sensation. When there is time delay between master and slave, position error occurs. This error is undesirable for delicate works. 3-channel bilateral control system can compensate this error, however asymmetric structure is problem. From this reason, operator can manipulate only master. To solve these problems, this paper proposes a compensation method of position error with symmetric structure in bilateral control system under time delay. The validity of the proposed method is verified through experiments.

Dead-times are widely utilized for the inverters to prevent short-circuits. In motor drive applications, 6th-order torque pulsations caused by dead-times depend on rotational speeds of motors. A Disturbance OBserver (DOB) approach is effective for the dead-time compensation in low load operations. The performance of the DOB depends on the observer gains. Hence, if we use the conventional constant observer gains, the 6th-order torque pulsation cannot be suppressed effectively. In this paper, the DOB with the variable gain is proposed. Besides, its stability is analyzed based on the Popov criterion, because the proposed system contains the nonlinear system. In this paper, the ability to reduce the voltage errors by using the multi-level inverters is also introduced. In our analysis, the value of the voltage errors affects the stability. The validity of the proposed method is confirmed by our experimental results.

In recent years, the demand for technique to transmit the touching sensation is increasing in a medical field. This paper shows that the Voice Coil Motor (the VCM)-based haptic system enables operators to grasp and manipulate a small and fragile environment with tactile sensation. In addition, bilateral control between different degrees-of-freedom system is inspected to acquire clearer tactile sensation than same degrees-of-freedom system. Moreover, the stiffness of the fragile environment is measured because the property of the environment is acquired. Finally, the validity of these methods are verified through experiments.

The basic structure and null space analysis of 5 DoF implant assist robot for position and angle adjustment is conducted in this paper. The problem of position control using the inverse matrix is the singular postures that make the system unstable. In this paper, the modulated potential field is also extended to 5 DoF robot manipulator for both position adjustment and angle adjustment. It is proposed to achieve the three requirement performances for teaching the information of "where to start cutting". That is 1) Physician can Free moving the manipulator when far from the destination. 2) The manipulator will apply adjusting force for easy converge to the destination when close in the destination. 3) The manipulator will apply adjusting force for collision avoidance when over the destination. The validity of the analysis results of modulated potential field for 5 DoF manipulator was confirmed by the simulation and experiment.

Power factor in mechanical system is a new concept to express characteristic in mechanical system. It defines dynamic behavior of the impedance characteristic in the motion. However, conventional derivation method requires short-time Fourier transformation in order to consider random input in mechanical system as a combination of sinusoidal waves. This paper proposes a novel method to obtain power factor in mechanical system. The proposed method is technically a simplified version of short-time Fourier transformation algorithm, but it does not require any Fourier transformation or complex calculations. The theory is supported by experimental comparison of the results.

The purpose of this research is to realize the novel palpation method called “organ palpation”. In conventional palpation method, the doctor knows the hardness of organ by his force sense. However, the organ palpation can get the quantitative hardness value by pushing the organ directly. In order to measure the hardness of organ directly, a remote actuator and an endoscope are utilized. In this paper, Electro-hydraulic transmission system (EHTS) based remote actuator is utilized for organ palpation. EHTS is one of the actuating systems using the fluid energy and mechanical energy. This actuator can transmit the position and force remotely without transmission loss. In order to confirm the efficacy of organ palpation device, the experiment assuming organ palpation is done. Through the experimental results, the environment stiffness calculation performance of EHTS based remote actuator is confirmed. In addition, the performance of EHTS based remote actuator is compared with “flexible actuator”.

Position error between master and slave occurs in bilateral control system under time delay and it is undesirable for delicate works. To solve this problem, this paper proposes a compensation method of position error in bilateral control under time delay. Firstly, the cause of position error is expressed. After that, it is shown that 3-channel bilateral control system, which is the conventional method, compensates position error. However, 3-channel bilateral control system is known to be unstable in contact motion. In 3-channel bilateral control system, a compensation term is added in master. In contrast, in the proposed method, a compensation term is added in slave. Moreover, stable contact motion and compensation of position error are realized. The validity of the proposed method is verified through experiments.

In recent years, it becomes more common for humans to use teleoperated robot systems. Mobile robot is effective as the teleoperated robot due to its large working area. The conventional mobile robots are generally controlled based on position and velocity control system, and they are not able to transmit tactile information. Introduction of force feedback is an effective solution, but it increases the operational force and deteriorates a operational ease. However, the deterioration of the operational ease can't be evaluated because there is no index until now. This paper proposed maneuverability as a new index of operational ease in teleoperation. Maneuverability is evaluated based on operational effort. By using this index, the appropriate teleoperation system can be determined in view of operational ease. Then, frequency domain dimensional scaling bilateral control (FDDBC) is designed to reduce operational effort. 5 types of control method including FDDBC are compared by using maneuverbility and the effectiveness of the proposed index is verified through the experiments.

This paper presents the design of a five degrees of freedom surgical robot suitable for laparoscopic surgery. Robots based on this design must fulfil the constraints of manipulability for the operating surgeon and the possibility of use through Master/Slave system as a tele-operated haptic device. The proposed robot is able to perform a full human-like wrist motion and operates a surgical forceps. Screenshots of both Computer- Aided Design and simulation results of the robot workspace, as well as the manipulability model are shown in this paper.

In this paper, the four-channel acceleration based control with communication disturbance observer and band eliminate filter is proposed. In previous research, authors proposed 4ch ABC with BEE In this method, BEF is set on position response of slave, and this method suppresses an oscillation of position response. Therefore, position response is improved. However, this method makes the large operational force, so it is necessary to improve operationality. In this paper, the method which combine previous method and communication disturbance observer(CDOB) which improve operationality is proposed. The performances of previous method and proposed method are evaluated through experiments.

In this paper, robot control by human motion data is considered. The conventional motion reproduction structure had its limitation on the performance due to the lack of means for environmental sensing. This study implements the widely used vision based approach. The possible reproduction structure with both visual and tactile senses are discussed. The proposed reproduction structure with both visual and tactile senses are evaluated in experiments in which the conventional reproduction structure is not applicable.

This paper proposes a new surface recognition method by a robot. Nowadays, demands for “Real World Haptics” are increasing. Tactile sensation which is acquired by rubbing motion is important for haptics. Therefore, surface recognition based on haptic information is focused in this paper. First, the surface sensing is needed to collect feature values. There are some researches which focus on sensing and analysis of surface tactile information by using sensors with robots. However, there are some disadvantages of using sensors such as signal noise. From that reason, this paper proposes getting surface haptic information without sensors at the tip of the robot. Second, a pattern recognition method needs to be applied for surface recognition. There are some pattern recognition methods. Self-organizing maps (SOM) is one of the solutions. SOM is able to summarize high dimensional data to low dimension with preserving the topological properties of data. SOM is suitable for multi-class recognition. From these reasons, this paper proposes the surface recognition based on haptic information using SOM. Multi class surface recognition is achieved by the proposed method. The validity of the proposed method was confirmed through 7 surface recognition experiments.

This paper proposes a method to calculate operational force in time-delayed 4-channel bilateral control systems. In 4-channel bilateral control systems, operational force becomes unnecessary force for haptic sense transmission. Under time-delay, it is known that this force becomes larger than the force without time-delay. In this paper, it is shown that new force, communicative operational force, is generated in time-delayed 4-channel bilateral control, and a method for calculating the force is proposed. Furthermore, well-known conventional time-delay compensation methods, 3-channel bilateral control and CDOB, are interpreted from the view of communicative operational force. The validity of the proposed method is verified by some experiments.

Bilateral control is the control technology transmitting the sense of the force to the remote area by using master robot and slave robot. In this control system, it is desirable for operational force to be small. If there is large operational force, it is difficult to recognize stiffness of the remote object, because differences between the contact force and the operational force come small. In addition, under the real situation, transmittable information may be limited. To solve these problems, in this paper, the operational force reduction method in bilateral control by acceleration model addition is proposed. This method reduces the operational force for manipulating master robot without imposing load on the network. Furthermore, instability can be avoided by using low-pass filter. At first, equations are assembled to reduce the operational force by using hybrid parameters. Afterwards, the validity of the proposed method is confirmed in simulations. Moreover, the time delay response, which is a new evaluation index, is introduced and the effectiveness of the proposed method is verified in time delay system. At last, the effectiveness of the proposal is shown in experiments by using actual robots.

Many studies on bilateral control based on 4ch bilateral controller have been carried out hitherto. Micro-macro bilateral control is an application of this method for micro manipulations. Micro-macro bilateral control enables magnifying and demagnifying the force information using scaling gains. However, in the case of a single system as a conventional method, there is a limit of scaling because of instability. This paper analyzes the stability of conventional method considering scaling gain by using root locus analysis. Furthermore, it proposes a two-step scaling micro-macro bilateral control using double master slave system as a new solution. For the new system, two master slave systems are used and connected to each other. A stable whole system is realized by connecting two stable systems with suitable scaling gain. Thus, the proposed method enables a higher scaling micro-macro bilateral control with multiplication of two scalings. Simulations and experimental results are given to show the validity of the proposed method. Comparison with conventional method is achieved by using stability analysis and experiments.

As far as authors' understanding, scaling factors presented in this paper are the highest values in the researches about force sensorless bilateral control. The cantilever is nominalized by disturbance observer in order to control master and slave with same method, which is intended to simplify the control system. An operator can feel magnified reaction force applied to the cantilever without force sensors by utilizing reaction force observer. Operationality and reproducibility are defined mathematically. Characteristics of these values and stability are analyzed and experimentally verified.

Demand for using robots in unstructured environments has been increasing. Since it is necessary to make contact with objects in order to execute complicated tasks, not only contact avoidance but also contact detection and stabilization of contact are required. This paper focuses on detecting contact during operation and applies the contact detection method using a dither signal to detect contact state at the moment of contact event. Methods for reducing influence of the dither on control or motion are then proposed considering the following two cases: application of the dither on an object is acceptable; and it is preferable to be avoided. A method of separating the dither element from the measured force using a ratio of inputs while applying the force including the dither to an object was proposed for the former case. A method of applying the dither in limited situation and stopping application in the contact state was proposed for the latter case. The validity of the proposed methods was verified by experiments on contact detection during teleoperation.

This paper proposes a novel time-delay compensation method for multi degree-of-freedom bilateral control system with different configuration. Bilateral control is a remote control technology, which enables transmission of force sensation. Time-delay is the one of the problems of the bilateral control, because it degrades the transparency and stability of the control system. Communication disturbance observer (CDOB) has been proposed to compensate time-delay without dead time model. However, CDOB cannot compensate time-delay if the bilateral control system has different configuration and is controlled in work space. Therefore, this paper proposes a novel observer, work space communication disturbance observer (WCDOB), for time-delay compensation. The proposed method can compensate time-delay if the bilateral control system has different configuration and is controlled in work space. Experiments were conducted by using actual network. The experimental results show the validity of the proposed method.

Robotics is a major field that is being researched for decades. With the use of robotic technology, applications of the microscopic level to the places where the human cannot reach are facilitated. When it comes to the larger robots, large actuators and drives have to be used to obtain the desired amount of power and the force or torque needed. As the electric motors have a limitation of torque output with its capacity, the most desirable way is to use the gears. However this introduces large inertia, backlash and friction to the system. If the system is used for the transmission of haptic information in bilaterally controlled systems, it greatly deteriorates the performance of the system and necessitates a compensation for the backlash caused by the gears. This paper introduces a method to compensate the backlash generated by the geared system. This method uses two identical counter operating drives per joint to compensate the backlash effect. Experiments are carried out for the proposed method to validate its accuracy.

In the conventional design of disturbance observer (DOB), a first order low pass filter (LPF) is used to prevent algebraic loop and satisfy causality in the inner-loop. Although a conventional DOB has a good robustness, its performance is limited by the dynamic characteristics of a first order LPF. A DOB that uses a higher order LPF is called as a higher order disturbance observer (HODOB) and can be used to improve performance of a system. However, improving performance may cause robustness problems. Therefore, there is a trade-off between robustness and performance of a DOB based robust control system, and it is directly related to order of the LPF of DOB. This paper analyzes robustness and performance of robust control systems based on DOB. The relation between performance and robustness is derived analytically, and a new design tool, which improves robustness and performance, is proposed for HODOB. A general second order plant model is analyzed, and simulation results are given to show the validity of the proposed method.

Disturbance observer (DOB), which is one of the key points of acceleration based motion control systems, guarantees robustness of a system by nominalizing real plant and suppressing external disturbances. Besides that, it can be used to estimate external forces/torques by identifying system uncertainties, and it is called as a reaction torque/force observer (RTOB/RFOB) in the literature. RTOB/RFOB has several superiorities over force sensors, and therefore, it has been widely used, specifically in the motion control area, in the last two decades. The main disadvantage of a RTOB/RFOB is that it is affected significantly by the identification of system uncertainties. However, there is no a clear report on the design constraints of RTOB/RFOB based force control systems. This paper shows that not only performance but also robustness and stability of a robust force control system are affected significantly by the identification errors in the design of RTOB/RFOB. A new design criterion which improves stability and performance of RTOB/RFOB based force control systems is proposed. RTOB/RFOB and force sensor based force control systems are compared and simulation results are given to show the validity of the proposed method.

This paper reviews the study progress of existing liver fibrosis assessment methods. After reviewing, this paper proposes a method to assess stiffness which intends the fibrosis, in the liver biopsy teleoperations. In this method, the liver biopsy operation is modeled. Also, teleoperated liver biopsy operations are conducted by a doctor. During the teleoperation, the force data is recorded by constructing reaction force observer (RFOB) without utilizing force sensors. The recorded force data is then treated in the force modeling equation of needle insertion movements. Finally, the quantitative stiffness assessment method is presented. The proposed method is applied to the evaluation of stiffness of three different environments which all imitate the liver. The experimentally assessed stiffness values are compared with the stiffness measured by the durometer. The comparisons validate that the proposal is effective to quantitatively assess the stiffness of needle inserting environments.

An estimation of bone density is important for dental implant. CT value has been used in clinical and diagnostic as a quantitative evaluation method of bone density. In this paper, a method for estimating the CT value is proposed by modeling the relation between the cutting force and the CT value. The cutting force is calculated by the thrust force of the linear motor and the torque of the rotary motor. The estimated CT value can be obtained in real time by comparing between the force from reaction force observer and the formula of CT value with the pre-estimated parameters. The validity of the proposal was confirmed through experiments using wood mentioned in Misch's bone density classification. The experimental results indicated that the error of CT value estimation was ±91 HU and the estimation accuracy was 84 %.

Human motion recognition systems play an important role in improving the ability of robots to support human life. This paper proposes a novel motion recognition method based on haptic data (i.e., position and force information). First, haptic data are obtained using a bilateral control system. Second, the haptic data are divided into action components, using modal transformation. Finally, both the position and the force information in each action component are compared with recorded data. A dynamic programming pattern-matching algorithm is used to recognize the desired motion, and the validity of the proposed method is verified experimentally. In the experiments, the proposed method is applied to a grasping motion. The proposed method can trigger scaled bilateral control and assist the operator in real time.

This paper examines a stability characteristic of gyrator type bilateral control in order to determine a definite feedback gain and scaling design. Stability is examined based on root locus. Maximum stable gain, transfer impedance and transfer admittance are observed in the examination. Moreover, it is observed that at certain transfer impedance and admittance, gyrator type bilateral control and transformer type bilateral control become equivalent to each other. Validity of the analysis and characteristics of several transfer impedance and transfer admittance design are examined based on experiments.

Motion canceling bilateral control (MCBC) is a method to synchronize motion of a teleoperation robot and a target, while an operator can obtain tactile sensation of the remote target. This interface helps the operator by taking a task and reduces his/her workload. However, the delay caused by the sensors deteriorates the synchronization performance and transparency of the MCBC. Therefore, synchronization performance improving method for MCBC utilizing an extended dual sampling rate observer (EDSR observer) is proposed in this research. The target motion is modeled as a motion with constant acceleration and the EDSR observer is utilized to estimate the present position of the target. The experimental results indicated that the synchronization performance was improved by 12.2 % in maximum error ratio and 14.8 % in root mean square error ratio. The experimental results indicate an improvement of the target operationality, which suggests the clear tactile sense transmission was achieved.

Since the advance of the aging society with a falling birthrate, technical inheritance has been a serious problem. This paper proposes a method to provide a skillful motion. First, haptic data (i.e., position and force information) is acquired using a bilateral control system. Second, the acquired haptic data is divided into action components by using modal transformation. Third, position and force information in each action component are compared with recorded data concerning the skillful motion. Finally, if an operator performs motion similar to skillful motion, the recorded data is loaded to the bilateral control system. Similarity between the performed motion and the skillful motion is calculated based on dynamic programming matching algorithms. The validity of the proposed method was experimentally verified. In the experiments, the proposed method was applied for grasping motion, and the recorded skillful motion was reproduced when the operator tried to perform the skillful motion. The maximum position error was 0.072 cm.

The Disturbance Observer (DOB) is widely used in many robust control applications such as robotics and industrial automation due to its simplicity and efficiency. The DOB estimates and compensates the system disturbances by using an inner-feedback loop in the range of its bandwidth. It includes the inverse of the nominal system model and a low pass filter (LPF) which determines the bandwidth of the DOB. The dynamic characteristic and bandwidth of the LPF directly affect the robust stability and performance of the system. The dynamic characteristic of the LPF can be adjusted by using Higher Order Disturbance Observers (HODOB). The bandwidth of the DOB is demanded to be as high as possible to suppress the system disturbances in a wide frequency range. However, it is bounded by the noise and robustness of the system. The conventional robustness analysis method which is based on the Small Gain theorem and unstructured uncertainties, unnecessarily limits the bandwidth of the DOB due to conservatism. The conservatism can be decreased by using the structured uncertainty based robustness analysis methods. In this paper, the robust stability and performance of the system with DOB/HODOB is analyzed by using the conventional analysis method and Singular Structured Values (SSV) that is based on the structured uncertainties. The pros and cons of these methods are shown. A general second order system model is analyzed and simulation results are given to show the validity of the proposed methods.

Cable driven systems have been applied in several manipulators and due to their high backdrivability and apparent low inertia have been successfully used in telemanipulation systems. However, in order to achieve high performances, a control to keep the cables taut is needed. In this paper, a position control in the null and range space is used to avoid cables from slacking and to achieve the desired performances. Indeed, a cable driven manipulator is a redundant system and its null space represents the internal forces, that is the tensions of the cables. To guarantee robustness against model parametric uncertainties and external disturbances, a position based disturbance observer has been designed. Proof of stability of the proposed control and bounds of the estimation error have been given. Simulation and experimental results show that the proposed control achieve the desired performances keeping the cables taut.

This paper proposes a method to design bilateral control systems based on interactive parameters. Conventional design methods were based on F parameters and, mainly took care of the elements A and D in F matrix. In this research, all four elements are taken care in order to increase the degree of freedom in system design. A design is based on interactive parameters, Z1, Z2, and θI. The new design method enables an independent design of impedance transmission and scaling. The effect of the proposal is experimentally verified.

Tendon-driven rotary actuators are utilized in various robots because they are small and high output. However, if the tendon-driven rotary actuators are utilized in bilateral control system, there are two problems. The first problem is interference. Bilateral control systems with tendon-driven mechanisms require decoupling of angle tracking, torque feedback, and tension control on master side, and slave side. The second problem is elongation. The tendons are extended by applied force. Therefore, it is difficult to control the angle precisely. In this paper, a method to compensate the error caused by the tendon elongation for tendon-driven mechanisms is proposed. This compensation method is designed based on modal transformation. The validity of the proposed method is verified by an experiment. Elongation is reduced by the proposed method. In addition, angle tracking, torque feedback, and tension control on master side, and slave side are achieved independently. Experiments were conducted to confirm the validity of the proposed method. In this experiment, proposed method is applied to a bilateral control system.

Several studies have been performed on the robustness of the systems with the disturbance observer (DOB). These studies are generally based on the frequency domain analysis which uses unstructured uncertainty and the Small Gain theorem. However, the frequency domain analysis can be easily implemented any kind of systems and it can properly define any kind of uncertainties of the system; it suffers by the conservatism due to the nature of the Small Gain theorem. The main drawback of the conservatism on the DOB based control system is that the bandwidth of the low pass filter (LPF) of DOB is unnecessarily limited by the conservatism. It was shown that the conservatism can be decreased by using the Structured Singular Values (SSV) method. However, this analysis is not suitable to define the constraints on the LPF of DOB in properly. The real parametric uncertainty based analysis shows us that if the bandwidth of the LPF of DOB is higher than its lower bound then the system with DOB becomes stable. The real parametric uncertainty based analysis does not suffer from conservatism however it can only consider the parametric uncertainties and the computational efficiency of this method highly depends on the system structure. These results were proved in the first paper of this research. In this paper, the stability margin of the system with DOB is analyzed and it is shown that as the bandwidth of the LPF of DOB increases the stability margin of the system also increases in the presence of the real parametric uncertainties. To show the validity of the proposed method, a general second order system with the real parametric uncertainties is analyzed and the simulation results are given.

This research treats a tendon-driven spherical joint mechanism. At most, tendon-driven spherical joint mechanisms have three rotational degrees of freedom in one joint. Moreover, the mechanisms are lightweight and simple. As a result, the mechanisms are suited for transmission of force sensation by bilateral control. In conventional researches about the mechanisms, transmission of force sensation was difficult. In this research, tension control, position control, force control, and bilateral control is proposed for spherical joint mechanisms. The proposed control utilizes projected force on an imaginary plane which touches the sphere. In addition, a spherical joint mechanism with three linear motors is developed. The mechanism has two rotational degrees of freedom achieved by three tension-controlled strings. To simplify the mechanism, sensors are not attached to the spherical joint. Only encoders attached to linear motors are used as sensors. Rotation angles of the sphere are estimated by position responses of linear motors. Results of experiments shows that force sensation was transmitted without strings slacking.

This paper proposes an analysis and evaluation method for a human motion skill proficiency. In this method, the skill proficiency of individual human is analyzed and evaluated from its time series action force. The action force data of a skill is recorded at first. To record the data, master-slave robots on which bilateral control is implemented are utilized. By using the recorded data, skill proficiency is analyzed from two aspects. One is skill accuracy and the other is skill repeatability. Finally, the skill proficiency of individual is evaluated quantitatively by employing graph theory. For skill evaluation, a pocket billiard robotic system is constructed. The proposed method is applied to the evaluation of a pocket billiard stroke motion. The experimental results validate that the proposal abstracts one's skill characteristic, which indicates skill proficiency.

In this paper, bilateral control with two degrees of freedom (2-DOF) haptic spherical interface is proposed. There is much research about the mechanical structure of the haptic interface to realize large movable range. However, these are not suitable for the interface of the open environment. In addition, to achieve wide movable range, there are some problems that the robot gets large and the large inertia deteriorates the operationality according to the movable range. In this paper, by utilizing a sphere as a interface, the interface has the two degrees of freedom and the unlimited movable range. The interface is utilized as the master robot. Meanwhile, an X-Y stage is utilized as the slave robot. The number of the actuators, the actuator type, and the structures are different between master-slave robots. Hence, bilateral control considering the differences is proposed.

In this study, we achieve haptic communication between different structures. In haptic communication, tactile sensation is transmitted to a remote place by cooperating robots. Conventional haptic communication is implemented under the assumption that the masses of the actuators are equal. We have found that haptic communication system is a kind of position/force hybrid control system and that it is not necessary to follow that assumption. In addition, exact modeling of haptic communication system and decoupling of tasks are essential for highly precise haptic communication. First, we describe the kinetic and dynamic behaviors of haptic communication system for cardiac surgery. The deterioration of haptic performance is shown to depend on an interference term, due to off-diagonal parameters in the modal mass matrix. Second, we propose a novel hybrid controller for the decoupling of the responses, and we analyze its performance, stability, and robustness. Simulations and experiments toward cardiac surgery are shown, and the effectiveness of the proposed method is verified.

In this study, we show that tasks can be realized by appropriate coordinate transformation. This approach, oblique coordinate control, decouples tasks. Even though a system is large, they can be designed by a combination of small tasks. Therefore, tasks can be regarded as reusable components. In this study, micro-macro bilateral control is achieved as a complicated task. Small objects can be manipulated as large objects in micro-macro bilateral control. However, ideal micro-macro bilateral controllers are usually derived only for single-degree-of-freedom (DOF) systems. Then, we propose a micro-macro bilateral controller for multi-DOF on the basis of oblique coordinate control. To obtain multi-DOF bilateral control, we first derive control goals as kinematic relations. This study also considers the case where scaling gains of position and force are selected in a different manner. The goals of micro-macro bilateral control are then controlled by oblique coordinate control. The validity of the proposed method is experimentally verified.

To solve the problem of force estimating error in reaction force observer based sensor-less bilateral control, the online identification and compensation method is proposed based on the recursive least squares algorithm with discontinuous projection mapping. The proposal can identify the system parameters in a fixed bounded range, which guarantees that good performance of the system are not influenced by the compensation. Besides, the force estimating error caused by the parameters mismatch can be canceled. According to experimental results, validity of the proposal is confirmed.

This paper presents a novel flow control method using PI controller for motion control system over network. UDP/IP protocol is known to be effective for motion control systems over network such as bilateral control system. However, UDP does not have a mechanism of congestion avoidance. The congestion, which causes large communication delay, jitter and packet loss, significantly deteriorates performance and stability of motion control systems. To avoid this congestion, a novel congestion control method, which adjusts a packet-sending period in real time, is proposed. The validity of the proposed method is shown by simulation and experimental results.

In a research field of network-based control systems (NBCSs), the time delay problem is one of the most significant issues. Efficient stabilization methods of time delayed control systems enable NBCSs to be flexibly applied to many kinds of situations. A novel time delay compensation method based on the concept of network disturbance (ND) and communication disturbance observer (CDOB) has been proposed. The compensation method has the same effectiveness as that of the Smith predictor. In addition, since the method is simple and does not need time delay model or time delay measurement, it can be easily implemented to various applications. However, the design method has not been concerned so far. This paper therefore presents stability analysis and studies a practical design procedure of the time delayed control systems with CDOB. At first, the concept of ND is introduced and the validity of the time delay compensation method is described. Then an analysis about the effects of parameters in control systems on stability is conducted. Characteristics of the effects of parameters on stability come out. Then we study a practical design procedure of the time delayed control systems. The validity of the design procedure is validated by experimental results. In the experiment, we also verify the performance of the system in the case of time-varying delay. Finally, comparative study of the method to the Smith predictor is presented.

This paper describes real-time gait planning for pushing motion of humanoid robots. This method deals with an object whose mass is not known. In order that a humanoid robot pushes an unknown object in both single support phase and double support phase, real-time gait planning for pushing the unknown object is proposed. Real-time gait planning consists of zero moment point (ZMP) modification and cycle time modification. ZMP modification is the method that modifies the influence of reaction force to ZMP. By cycle time modification, the period in double support phase is modified to avoid a robot tipping over. These modifications are calculated from reaction force on arms in every cycle. With these methods, trajectory planning for pushing an unknown object in both single support phase and double support phase is calculated. Even if parameters of an object and friction coefficient on the floor vary, the robot keeps on walking while pushing an object. The effectiveness of the proposed method is confirmed by a simulation and an experiment.

Motion control in open environment will be more and more important. The recent machines are required to have an ability to contact with unknown environment. The environmental information is a key to be compliant to unknown environment. This paper develops a novel viewpoint of motion control based on quarrying of environmental information. The quarry process means to abstract and express the environmental information by its inner variables. A disturbance observer is a basic technology for quarry process and attainment of robust acceleration control. Since the disturbance observer can observe the external force from the environment without force sensors, adaptive ability to environmental changes is improved. A haptic ability is also important for cooperative motion with a human. It means that a robot should control the interaction. Once such kind of ability is installed, then it becomes cooperative with humans. Since the control stiffness of ideal force control is zero, cooperation of a human and a robot is realized through force control. The proposed method is applied for a power-assist wheelchair. Human operationality and safety at the collision to obstacles are improved. As a result, compliant motion to unknown environment is attained. The experimental results show viability of the proposed method.

The paper proposes a method for estimating the mixed spectrum which is composed of line and continuous spectra, the latter of which is characterized by an AR or ARMA noise model. Line spectrum is represented by multiple sinusoids. In order to avoid simultaneous minimization of a prediction error criterion with respect to all unknown parameters, the authors give an efficient iterative algorithm for estimating the frequencies of the sinusoids and other parameters separately. By adopting the genetic algorithm in choice of initial values of the AR or ARMA parameters in the iterative estimation, one can attain globally optimal estimates of unknown parameters. The frequency estimate is given by a modified Toeplitz approximation method using a shifted correlation matrix of observed signals. The effectiveness of the proposed algorithm is validated in numerical simulations.

Requirements for fast and accurate motion in industrial robot manipulators demand more advanced control techniques. Past techniques, such as the resolved acceleration method and nonlinear feedback control, etc. require detailed information on mechanical parameters. In these methods, the modelling errors adversely effect manipulator motion. To overcome this problem, this paper proposes a method for constructing nominal dynamic modelling for a robotic arm in the operational space. When the proposed method realizes a disturbance observer in the operational space, individual coordinate motions can be decoupled and independently controlled. Further, individual motion in the operational space coordinate is driven as if only nominally fixed mechanical dynamics in the operational space existed. As a result, the method enables one to construct the control law without any calibration for the mechanical parameters. Finally, the authors present experimental results from an implementation of the proposed method.>

Recent requirements for fast and accurate motion in industrial robot manipulators demand more advanced control techniques. For these requirements, many manipulator control methods have been developed. One of them is a manipulator control based on the disturbance observer. The disturbance observer estimates the disturbance torque (force) using a nominal model and compensates for the parameter variations between the real manipulator and the nominal model. Because of the high performance and simple algorithm, its usefulness for real time control the disturbance observer has recently been employed for manipulator control. This paper analyzes a manipulator control based on the disturbance observer. From this analysis, we also propose a design method of the manipulator control based on the disturbance observer. Finally, we present experimental results from an implementation of the proposed method.>

The paper presents the state of the art of motion systems particularly emphasizing both estimation and identification of parameters and control variables of an electric-motor-driven motion system. In a modern electrical drive system, it is required to take not only the electrical aspect but also the mechanical phase into total system consideration. Improvement in electrical aspect needs a variety of information pertaining to electrical machines and power electronic circuits for improving AC variable-speed drives. Important techniques of identification or estimation of parameters and control variables in AC drives are explained. Such information includes machine parameters, flux, speed, position, and so on. Also, the paper shows that there is some theoretical limit of performance. For improvement of the mechanical phase, the disturbance torque is the most important variable to be identified. It is used in motion control systems, for example, in the feedback loop. Various applications are possible by modification of such a basic approach. As a conclusion, the paper shows that the total robustness is attained by integrating advances of control technique on the electrical aspect and the mechanical aspect. There are numerous variations of controller by possible combinations of these two aspects according to applications.>

The authors propose robot force control strategies that are robust against disturbance and parameter variation. These strategies are expansions of a disturbance observer which estimates disturbance and parameter variations of motors with a simple computation. Observers are proposed to estimate parameter variations of the environment on which the force is imposed. Since the control system is fixed to a nominal system by the observer, a second derivative of force can be controlled. Force control is introduced using a controller of the second derivative of the force. The force response similar to the force command is realized in spite of the disturbance and the parameter variations of the control object. The effectiveness was confirmed experimentally.>

The authors propose a simple high-performance control strategy based on disturbance compensation by the disturbance observer in task space. The disturbance observer makes robot manipulators linear in task space and realizes acceleration control. The inverse kinematics routine can be simplified, because the disturbance observer compensates not only the disturbance but also the error due to the simplification of the inverse kinematics routine. The strategy was applied to a three-degree-of-freedom direct drive robot to show its effectiveness experimentally.>

A simple high-performance hybrid position/force control that is based on the acceleration tracing orientation method (ATOM) is proposed. From the analysis of ATOM, it is pointed out that precise acceleration control is a key to improve the performance of the motion of the robot. The realization of a strict acceleration controller, however, is almost impossible by the conventional disturbance compensation methods. Recent research on a disturbance observed shows the realization of the acceleration controller. Compared with the inverse dynamics, the observer is simple and robust against parameter variation. Moreover, the disturbance observer can perform parallel computation in each joint by the same algorithm. ATOM was applied to a three-degrees-of-freedom robot to show the effectiveness of the ATOM experimentally.>

The dynamics of the multi-degrees of freedom manipulator is highly nonlinear and the compensationagainst this nonlinearity should be indispensable. This paper proposes the decentralizedjoint control method based on the disturbance observer where the dynamical equation is not directly solved. By using the information of the acceleration, the nonlinear term in the dynamical equation is estimated without the mathematically complicated process, and as a result, the joints are able to be decoupled and controlled independently each other by using even 16 bit microprocessors. The simulated and experimented results are shown in the paper to confirm the industrial viability of this method.