Wave control has been used for multi-mass models conventionally. On the other hand, this method has the advantage of their simplicity, because of achieving both quick responsiveness and vibration suppression at the same time. In this study, target system is modeled as a two-mass system, not wave model, and controlled by wave control. Proposed method is to find the optimal time delay for a two-mass system. Transfer function of the entire system could be divided into 2 parts, one representing PD control and the other representing vibration suppression by wave control. Especially, the later is only affected by time delay, find the optimal one in this study. Time delay using by wave control, is defined from evaluated function, based on overshoot, steady-state, and time to reach response. This approach leads expanding the range of wave control. Experiments have shown that this method suppresses vibration and improves responsiveness while ensuring stability.

This study introduces quasi-real-time (QRT) motion control, explicitly incorporating measured sampling periods into the digital control loop. Digital control in mechatronic systems typically relies on the assumption of fixed sampling periods. However, practical systems often experience sampling fluctuations due to hardware limitations, sensor-related interrupt processing, and communication delays. To address this issue, a systematic discretization method for continuous-time transfer functions is proposed to enable controller, observer, and filter design under sampling fluctuations. Experimental results demonstrate that the proposed approach performs more robustly than conventional fixed-sampling implementations. QRT motion control relaxes stringent real-time (RT) constraints and is a foundation for user-friendly, general-purpose operating system (GPOS)-based RT execution frameworks in advanced mechatronic applications.

Thumb tip force was estimated from sEMG with an element description method (EDM). At the modeling, a hysteresis between sEMG and force was considered. An EDM is one of a system identification method and it can generate a non-black box model. Also, it is possible to set elements and structure of the model in an EDM modeling. The elements and functions was set to conduct a hysteresis modeling in this modeling. If the model is not a black box, the extensibility improves because it is possible to devise it. Moreover, a mechanical system needs a non-black box model because it is possible to adjust in case of emergency. In this paper, a novel model for the estimation with the EDM was proposed. Then, the estimation accuracy was compared with its of a conventional method. A long short-term memory (LSTM) was implemented as a conventional method in this estimation. In this proposal, the relationship was analyzed in stages which are that the force in increasing and decreasing. The functions were decided from the results of this analysis. At the force increasing and decreasing, the functions were set with an exponential and a hyperbolic tangent, respectively. As the result, the proposed method could improve the accuracy. From the results, the proposed method could estimate the force from sEMG than the conventional method. In addition, the calculation process of the model was clear.

As the population ages, the demand for rehabilitation technologies assisting patients with spinal cord injury and other neurological conditions has become increasingly important. Functional Electrical Stimulation (FES) is one such method, aimed at restoring motor function by electrically activating muscles. FES has contributed to the functional recovery of various parts of the human body. However, it has been difficult to achieve manual dexterity with FES. This is because various muscles are densely packed in the hand and their interlocking with each joint is complex. Therefore, although there have been studies on controlling finger joint angles, position control of the fingertips by FES that takes into account the cooperative motion between finger joints has not yet been achieved. In this study, we propose a fingertip position control system that focuses on the interlocking nature of the two finger joints. For fingertip position control, we consider the finger kinematics and then control the finger joint angle. Experiments showed that fingertip positioning control in the x–axis direction was achieved with high accuracy.

Motion-copying systems (MCS) enable the transfer of motor skills from humans to humans or humans to robots. MCS are becoming increasingly important in the context of human-robot interaction (HRI). However, the biggest challenge with MCS is the lack of a standard for motion abstraction. In practice motion abstraction mostly depends on the end use case or the control scheme employed. The recent advancements in control systems such as hybrid and adaptive impedance control demand the simultaneous abstraction of both the force and position information from motion. In addition, it is also critical to classify the motion type i.e. free or forced motion, and identify the instance of contact. Most methods focus on either the position or the force information. Methods that consider both force and position are not scalable, portable, and/or employ a black box model. In addition, these methods of motion abstraction are unable to classify the motion type. Considering all of these challenges this research proposes the use of wearable sensors, surface electromyography (sEMG), and flex sensors for the abstraction of motion directly from muscles and focuses on a novel framework for identifying contact state and instance of contact without the use of any additional sensors. In addition, the proposed framework will enable context-aware control strategies and is a great resource for human-in-the-loop control strategies for applications such as motor rehabilitation and assistive devices.

Legged robots have the potential to be useful in rescue operations during disasters but their mobility is not adequate. Hydraulic and elastic actuators have been used for leg robots in the past but they have problems such as high weight and being not suitable for long-hour operation. This study aims to solve these problems by applying a variable reduction-ratio gear to robots. To confiSm the effectiveness of the proposed mechanism, we conducted experiments, no load experiment and throwing experiment on a one-degree-of-freedom robot. These experiments showed that the reduction-ratio can be changed and the performance of the throwing motion can be improved by changing the reduction-ratio.

In the development of the multi-DOF manipulator, we focused on the structure of passive exoskeletons, and proposed the new gravity compensation using parallel wire mechanism and springs. The novelty of the proposed gravity compensation is that the low-inertia mechanism with parallel wire can achieve the challenge of passive exoskeletons of the relation between the multi-DOF and the increase of the inertia. Also, in the proposed method, springs for gravity compensation are attached apart from the main body of manipulator, which can change the elastic force to compensate the weight of the manipulator in large range. We conducted the experiment with the manufactured manipulator with the proposed gravity compensation, and discussed the effectiveness of the proposed gravity compensation and the potential when assuming the exoskeleton application.

In this paper, the structure of a model to estimate human motion from surface-electromyography (sEMG) was defined mathematically and physically. Especially, an infinite impulse response (IIR) filter and an element description method were focused to generate the model in this paper. Human motion can be estimated from sEMG. However, the relationship between sEMG and human motion has a complex characteristics such as a non-linear relationship. The cause of the above complex relationship can be thought the muscle contraction velocity. Then, the IIR filter was applied to consider about the previous sEMG value in the estimation. In addition, some conventional models have been a black-box model and it is not easy to interpret the model mathematically and physically. From the above, an element description method (EDM) was applied to generate the model in this paper. EDM is one of the system identification method and it is easy to interpret the model mathematically and physically because EDM can generate the block diagram of the model.In this way, the proposed method could solve two conventional methods about the muscle contraction velocity and the black box model. Then, it was possible to define the structure of the model by the above in this paper. In this paper, the models about a wrist and a fingertip motion were generated and considered about the structure. As the results, the structure of models was defined with a hyperbolic tangent function. It will be possible to apply the model to various motions by just identifying the parameters about the relationship between each joint and muscle because the amount of muscles and range of sEMG are deferent from each muscle.

Effective algorithms for object exploration and manipulation have been widely required for the improvement of the dexterity of robots. Especially, feedback of tactile sensation can be utilized for the precise and versatile manipulation. However, most conventional methods are conservative. This is because they ignore the exploration process and assume that a robot manipulates an object at the tip of its arm. These conditions are not always satisfied, especially in the case that the robot does not have the information about the object and have to explore it firstly. In this paper, we propose an algorithm for sensorless object exploration and stable contact. The algorithm is based on the statics with the extended Jacobian matrix, which relates the joints and an arbitrary point of the robot. The exploration algorithm for the stable contact with unknown environment is also introduced, and represented in a form of a state machine. Experimental results with a robot manipulator are shown for the validation of the proposed algorithm. Furthermore, an advanced experiment with a dual-arm robot is shown and validates the grasping motion with the proposed algorithm.

Vibration suppression has attracted interest in achieving fast, stable motion control in industrial fields. This study uses the wave partial differential equation (PDE) to model resonant systems and connects a lumped load and the PDE model in series. The lumped load is governed by the ordinary differential equation (ODE). This integrated model replaces the conventional two-mass resonant model, referred to as the PDE-ODE model in this study. A matrix representation of the PDE model is eigenvalue decomposed. The decomposition provides the basis transformation of the variables on the actual space into those on a wave space. Based on this transformation, the proposed controller equips the decoupling of the traveling/reflected waves for vibration suppression. Impedance matching explains the conditions necessary for the decoupling and control of vibration. The suppression method requires only the PDE part's parameter, making the control system resistant to inertial variations.

In recent years, there has been a growing interest in developing robots capable of replacing human labor, driven by factors such as the decline in the working-age population. One crucial aspect of developing such robots is the ability to decompose complex tasks into manageable subtasks and establish models that govern the switching between these subtasks. Finite state machines (FSMs) and behavior trees (BTs) are two commonly used models for task-switching in robotics. FSMs are mathematical models that describe the behavior of a system with a finite number of states. They have been extensively employed in various robotic applications, including gait pattern, trajectory, and motion generation of robots. However, these transition models primarily focus on the relationships at the higher level. Additionally, FSMs are rarely utilized in acceleration control systems, which offer precise position and velocity control, as well as flexible force control and hybrid control capabilities. BTs, on the other hand, are graphical models that represent an agent's behavior as a graph composed of nodes and edges. BTs also enable modelling of switching between multiple tasks and have been explored for automatically generating behavior trees through machine learning techniques. This approach is well-suited for motion control using acceleration control. In this research, by combining BT-based task-switching with acceleration control architecture, we enable autonomous switching between target object approaching and obstacle avoidance. The proposed method is validated through simulations and experiments using a 6-DOF manipulator.

Robots are used by humans not only as tools but also to interactively assist and cooperate with humans, thereby forming physical human–robot interactions. In these interactions, there is a risk that a feedback loop causes unstable force interaction, in which force escalation exposes a human to danger. Previous studies have analyzed the stability of voluntary interaction but have neglected involuntary behavior in the interaction. In contrast to the previous studies, this study considered the involuntary behavior: a human’s force reproduction bias for discrete-event human–robot force interaction. We derived an asymptotic stability condition based on a mathematical bias model and found that the bias asymptotically stabilizes a human’s implicit equilibrium point far from the implicit equilibrium point and destabilizes the point near the point. The bias model, convergence of the interaction toward the implicit equilibrium point, and divergence around the point were consistently verified via behavioral experiments under three kinds of interactions using three different body parts: 1) a hand finger; 2) wrist; and 3) foot. Our results imply that humans implicitly secure a stable and close relationship between themselves and robots with their involuntary behavior.

Functional Electrical Stimulation (FES) is a technique to present functional movements by applying electric current to nerve-muscles to induce muscle contraction. In the presentation of hand movements by FES, the flexor digitorum profundus muscle located in the forearm has been used as the muscle that causes flexion. However, the musculature of the forearm is intricate, making it difficult to stimulate arbitrary muscles, and therefore, highly accurate joint angle control has not been achieved. In this study, we aim to realize high-precision servo control of the hand joints by focusing on and stimulating lumbrical located in the hand to increase their independence as a system The performance of tracking the index finger metacarpophalangeal (MP) joint angle was compared when the flexor muscle were flexor digitorum superficialis and lumbrical. Step wave and sinusoidal wave were given as the command values for verification. The root mean square error (RMSE) results showed that the tracking accuracy was higher when the lumbrical was used. In addition, the shape comparison shows that the joints tracked more stably with less vibration when lumbrical was used. In this paper, we proposed a hand joint control system using the lumbrical as flexors. This method is effective for servo control of the hand MP joint angle. Experiments verified the effectiveness of the proposed system.

This study is for a functional electrical stimulation. Functional electrical stimulation is a system that uses electrical stimulation to generate specific joint movements. If the nerve is alive, it is possible to promote muscle contraction from the outside by electrical stimulation. If arbitrary movements are generated, to build a control system is necessary for functional electrical stimulation. A model of muscle contraction is needed for control using functional electrical stimulation. It is assumed that the control accuracy will be improved by incorporating the necessary information into the model based on human physiology. In this study, the angle-dependent term in the reaction during muscle contraction is focused as one of the necessary information characteristics. As the angle changes, the muscle condition changes, resulting in responses such as stretch reflexes and repulsive forces. This is important information because if such a response is not taken into consideration, an error will occur between the model and the actual output. In the conventional research, the angle-dependent term was identified by focusing on the lower limbs, and the parameter fitting was realized by using the double exponential function. In this study, the knowledge of the previous study is applied to the upper limbs to build a model. Since the response is different between the upper limbs and the lower limbs, the movements are not always the same. Therefore, verification was performed. From the experimental results, the model based on the double exponential function was a model that took individual differences into consideration even in the upper limbs.

In recent years, motion-copying systems that store and reproduce human motions have attracted much attention. In the conventional method, the motion is stored using a motor, which affects the original task. In this study, we focused on the relationship between electromyography and force in order to realize unconstrained, non-contact force measurement. In this paper, we modeled the relationship between the force of pressing a force sensor with a fingertip and the myoelectric potential of performing an action by using the elemental description method, which is one of the system identification methods with easy physical interpretation. As a result, an accuracy of 0.260 N, the least squares error, was obtained. In addition, we conducted on copying and reproducing the motion of finger using this model. Although the accuracy of force estimation was low, we were able to estimate the force with the same accuracy. In the future, we aim to improve the accuracy of the estimation and to measure the force using only the myoelectric sensor without the force sensor.

In order to adapt robot hand to daily movements, it is necessary to control the finger pad force. There is an affinity between the elastic joint, which is the mechanism that can press the finger pad, and the two-mass resonance system (TMRS) that can estimate the force at the tip. However there are some elements in the elastic joint that cannot be modeled by TMRS. The elements are include an error caused by the use of a nonlinear spring called rubber in this mechanism, and an error caused by friction generated in this mechanism, which was not generated in the conventional TMRS. Therefore, in this paper, we propose to model those elements by element description method. In order to verify the effectiveness of this method, we verified the accuracy of the value estimated by TMRS in some postures.

With the declining birthrate and aging population, it is important to inherit expert skills. A motion-copying system can accurately reproduce the position, velocity, and force of human motion at the same time. However, it is difficult to reproduce the same motion in an environment different from the saved environment. One of the solutions is to model the relationship between the position, velocity, and force of motion. It is important to improve the accuracy of the model and the versatility of modeling. In this study, we model the environment by using an element description method. Focusing on the calligraphy movement, it was shown that the accuracy of the relationship between the force, position and velocity of the brush is improved compared to the conventional model.

In recent years, multi degree-of-freedom(DOF) robot arms for delicate movements are required in various fields such as industry, medical care, and service industry. For the delicate movements, high-precision force control is required. To achieve this, it is necessary to use direct-drive without gears that reduce back driverbility. However, conventional robot arms use gears to gain the large torque that supports the weight of the arm and hinder the realization of direct-drive. Therefore, in this study, we proposed a direct-drive robot arm with active self-weight compensation by motors. Then, the effect of the proposed method is shown by simulating the torque required to support the arm when the self-weight compensation is performed by the self-weight compensation motor in a 7-DOF manipulator. Furthermore, we actually manufactured a three DOF direct-drive robot arm using the proposed method. All the motors were placed at the base of the arm to prevent the increase in inertia of the robot arm, and the power was transmitted by wires and tubes.

Recently, the rational motion of robots is required for further applications. Human motion gives many clues to studies of robotics. This study focuses on the fact that a human adjusts grip force when he/she performs an impact motion with a tool. The tools often have elasticity, and the human adjustment enables an effective impact motion. For reproduction of the impact motion with a flexible manipulator, this study models the elasticity as a wave system. The flow of the reflected wave is controlled during the impact motion based on the human adjustment of grip force. Since this study is based on the research of vibration suppression in elastic structures, it provides not only rational but also stable motion control. The experimental results show the validity of the proposed method.

Interactions between robots and their environment are essential in many robotic tasks. In the interaction, both visual and haptic information are important. Visual information gives us a state of environment before the interactions. On the other hand, haptic information gives us that after the interactions. Recent studies investigate relationships between vision and touch using deep learning. However, the models become complicated and it is difficult to understand. In this study, we propose a framework that can estimate a probabilistic distribution of a object’s stiffness using visual observation and contact information based on object detection and Gaussian mixture model (GMM). We focused on environmental stiffness as one of the important properties of environment. The proposed framework can use prior knowledge of the environment in designing parameters of GMM. In addition, We applied the proposed method to object identification task and experimentally validated it.

Robots have been introduced into industrial factory automation. It is necessary to consider interactions between the robots and environments to expand executable tasks of the robots. In the interaction, impedance is an essential factor for the robot to contact with the environment, whereas the impedance is unobservable without contact. In this study, we introduce a concept of affordance for impedance estimation without contact. We propose the impedance estimation method from an RGB image input using deep learning. In this paper, we show that the proposed method can extract pixels corresponding to sponges with its impedance composed of stiffness and viscosity, including the distribution of the impedance. We conducted the experiments to validate the proposed method.

Periodic disturbances occur during repetitive operation of machines in industrial production. Compensation for the periodic disturbances is an important issue to realize proper machine works beacause the periodic disturbances deteriorate machining precision. In order to eliminate the periodic disturbances, an adaptive periodic-disturbance observer (APDOB) has been proposed as an effective method that can also estimate and compensate for frequency-varying periodic disturbances. However, the APDOB has a problem that design of the APDOB is complicated owing to its six design parameters, which need to be empirically adjusted. Here, we propose an approach based on a genetic algorithm (GA) including a Lévy flight to automatically adjust the six design parameters. The proposed method can remove the conventional empirical design. Moreover, the Lévy flight could improve the exploration ability of the GA by optimizing mutation operator and the best solution found by the GA including Lévy flight could improve the performance of the APDOB.

The robot controller using the wideband acceleration controller embedded on a programmable system-on-a-chip (PSoC) is presented. Since the robot controller requires to execute both fast and complex processing, a standalone stored-program machine or a field programmable gate array (FPGA) provide an insufficient platform. The PSoC prepares freedoms for platform design and it enables to overcome existing restrictions. Herewith, appropriate task-partitioning is essential to elicit performance. Concretely, high tracking performance and tolerance are ensured by a fast controller, and dexterity of motion by a generic controller. By checking and examining a control architecture in detail, the preferred task-partition is derived. Eventually, an acceleration controller was implemented on the FPGA and a computing-torque method was on the stored-program machine. For verification, positioning of the robot was conducted and high tracking performance was confirmed.

Developing a thermal interface to share a thermal sensation between remote locations can lead to significant progress in the field of haptics. The research focuses on a technique of rendering thermal sensation that is an essential element of the haptics for touching human and machines each other. The thermal technique is required in case of offering a sense of security and sharing a precise hand with thermal sensations between remote places such as nursing care and rehabilitation robot. This paper proposed a method to control heat conduction on a palm by setting virtual thermal conductance between two fingers of the glove. Two thermal gloves are used as a master/slave systems, and the virtual thermal conductance can change heat conduction on the palm. The proposed interface and its control algorithm can be used to share a spatial thermal sensation on a palm. The experimental results indicate the validity of the proposed method. The interface and its control system are expected to connect people in remote locations, and the developed system can potentially be used in medical and multimedia applications.

Repetitive operations are widely conducted by automatic machines in industry. Periodic disturbances induced by the repetitive operations must be compensated to achieve precise functioning. In this paper, a periodic-disturbance observer (PDOB) based on the disturbance observer (DOB) structure is proposed. The PDOB compensates a periodic disturbance including the fundamental wave and harmonics by using a time-delay element. Furthermore, an adaptive PDOB is proposed for the compensation of frequency-varying periodic disturbances. An adaptive notch filter is used in the adaptive PDOB to estimate the fundamental frequency of the periodic disturbance. Simulations compare the proposed methods with a repetitive controller and the DOB. Practical performances are validated in experiments using a multiaxis manipulator. The proposal provides a new framework based on the DOB structure to design controllers using a time-delay element.

Computerized numerical control (CNC) systems are widely used in the processing field. The key technology of these systems is the interpolation that connects the desired points. The interpolation using a clothoid curve is one of the effective methods for connecting the points because of its outstanding smoothness properties. A clothoid curve is a spatial function. Hence, synthesization with a time function is necessary to apply the curve for the actual CNC equipment. The clothoid curve can be easily synthesized with a time function by designing the tangential velocity as the time function. However, a numerical calculation is necessary because the clothoid curve has a limitation in that it does not have an analytical expression. Therefore, the discretization error of the numerical calculation must be considered because the calculating resolution of the clothoid curve is determined by the tangential velocity and the sampling time. This study proposes a clothoid interpolation based on an iterative true-value prediction. This method can immediately estimate the true value of a clothoid curve by pinching integration and Aitken acceleration even in the case where the calculation resolution is limited. Hence, the method can suppress the discretization error of the clothoid curve. A smooth interpolation for the CNC machines can be achieved using the proposed method.

This paper presents a method to improve the robustness of the position control of a small permanent magnet within a living organism, such as the human body in micro-surgery. So far, position control has been achieved up to 5 Degrees of Freedom with robustness against model uncertainties. In order to achieve robust control against non predicted disturbances, this paper uses a disturbance observer (DOB) which adapts to the non-linearity of the system. Disturbance observers require fast and accurate position sensing in order to estimate and compensate the disturbance accurately. The proposed method depends even more on the quality of the position sensing. To ensure good performances, robust stability conditions are derived regarding position feedback, and the proposed DOB is validated by simulations and experiments.

In contrast to precise position control of the robot arms and manipulators, the force control has been studied recently. The robust position control does not allow the robots to share the same space with humans because the robots faithfully follow the position command, and it may lead to break the contacted environments. The impedance and compliance control could set impedances of robots so that the control laws have been utilized for interaction with environments or humans. By using these controls, the robots safety contact with the environments. However, following performance to the reaction force due to the collision generally depends on the setting impedance of the robots. When the robots contact with the hard objects or moving objects, the large force may occur. In order to cope with this, the information of the environment position implicitly is used, as the background that resent techniques of environmental recognition have been precise and high-speed. In the study, the method of impulsive force suppression considering contacted object position is proposed. The method does not use the switching of position control for approaching and force control after the contact. Moreover, the force control is accomplished in desired adding force direction without switching. Therefore, the method does not require especial orbit generation. The validity of the proposed method is confirmed through the simulations and experiments.

This paper proposes a event-triggered formation control method for a leader-follower multi-agent system. The purpose of the multi-agent system is to add more function to the system by cooperative control of multi-robots. Research of multi-agent system is useful for society. Generally, in conventional research, each agent always need to communicate with neighbor agents. So, communication failure like as cross-talk is likely to occur. Furthermore, energy resource of robot is limited. So, it is necessary to save the energy. To solve this problem event-triggered control is researched. In these research, the control input is generated only transmitted information in triggered-time. On the other hand, in the proposed method, each agent estimate the trajectory of neighbor agents. When error between estimated and true trajectory become over the threshold, information is transmitted. By using the proposed method, it is expected to reduce the number of information transmission.

Precise force control and position control is essential for many robotic applications. During unilateral or bilateral object handling remote applications, human operators apply excess forces on the actuators with the intention of better grip and it is possible to damage the handled objects. This paper proposes position control and force control techniques when human applies excess force. The controllers consist of predefined force and equilibrium position which are correspond to remote environmental object safety. The operator applied excess force is modeled as a spring force through a virtual stiffness model. The paper introduces proportional derivative position control loop to conventional virtual stiffness controller. The force control loop and the position control loop references are combined in the common dimension of acceleration to produce current reference to the actuator. The sensorless sensing techniques of disturbance observer and reaction force observer are utilized to disturbance suppression and external force estimation. In the force controller, estimated reaction force is reduced to desired value by introducing virtual force loop between reaction force observer output and reaction force feedback input. The position control is achieved by introducing a scaling factor to reaction force feedback path. The switching between force control and position control is possible with scaling factor value. The performances of proposed methods are compared with conventional method and validity of the proposed methods is verified by simulations and experiments.

Advanced robotic systems have been developed to realize robot society, a mechanism and a control theory of these systems have been researched for a long time. Due to the advantages of low cost and safety, these systems with flexible mechanism are required in the future. However, the fast response of such a system which is regarded as a resonant system induces a vibration caused by mechanical resonances. Therefore, motion control theories for resonant systems have been extensively researched to improve motion response, most of these control theories are directed to the state of tip mass. This paper focuses on control theory for the position of arbitrary mass of multi-mass resonant model, proposes position control of 2-DOF resonant system. In this paper, a 2-DOF resonant system is modeled as a superposition of two-mass resonant models. The controller design is based on an assumptions; two actuators independently act on the state of middle mass, which is regarded as load. Therefore, the position control of middle mass of a 2-DOF resonant system is realized. Simulations and experiments verify the effectiveness of the proposed control theory.

Recently, realizing an ubiquitous energy society is expected due to the development of wireless power transfer technologies. In an ubiquitous energy society, receiving energy with multiple frequencies is required because energy is transferred with multiple frequencies. A dual-mode wireless power transfer system is a system that realizes efficient power transfer with two different frequencies. Normally, these systems are used to transfer different kinds of information but few research consider transferring power with different frequencies at the same time. Therefore, this research clarifies theoretically and experimentally power can be transferred with two different frequencies for dual-mode wireless power transfer system using magnetic resonance. Voltage and power that occurs in receiver circuit when wireless power transfer is done by another two frequencies at the same time is discussed theoretically. Experiment is conducted to verify the theoretical calculation results. Experimental results show the good match with theoretical calculation.

This paper proposes a design method of multilateral systems including system connection. To consider system connection, the proposal uses a reachability matrix. A multilateral system enables us to transmit haptic information between many human operators. If the multilateral systems consists of many master system and one slave system, many operator can share the haptic information of an environment in the slave system. However, a conventional multilateral system is difficult to realize independent operation of master system. The cause is that a control object is realization of position synchronization in all subsystem. Here, subsystem stands for master and slave system of multilateral systems. Therefore, control design has to introduce another view point for independent operation of multilateral systems. The proposed method pays attention to system connection. Concretely, arrival information between sub-systems is derived by a reachability matrix, to consider system connection in control design. The arrival information is defined as information transmitted between subsystems. In considering the arrival information, control design considering system connection is possibility. By using the proposal, the multilateral system enables many human to operate independently. The validity of the proposed method is confirmed by the experiments.

A method of stable contact motions for force tracking control based on the concept of resonance ratio control is proposed in this research. The similarity in the structure for admittance control for contact motions and two mass resonance systems is derived. From the similarity, it is found that the concept of the resonance ratio control is applicable to force tracking control. Based on the concept of resonance ratio control, an admittance controller for contact motion with the environmental disturbance (EnvD) compensation is proposed. By using the proposed method, vibration suppression in contact motion is realized, even if the environment has no, or insufficient, damping (decay). The response characteristics of contact motion for force tracking control can be determined arbitrarily by the proposed method.

Recently, tactile transmission utilizing wearable devices are necessary to support human life or communicating with people in remote locations. One key factor of transmitting tactile sensation is thermal sensation. Flexible thermal devices have been developed, however, precise temperature distribution cannot be reproduced due to the large size and the flexibility of the devices. Therefore, a technique of rendering thermal sensation considering heat propagation is required to obtain the desired temperature distribution. In this paper, a method to control temperature on a curved surface for implementing to wearable devices is proposed. This method can be applied to various shapes of devices because the deformation of a device can be observed by the propagation delay of the heat flow. Experiments are conducted to verify the validity of the proposed method.

In several previous researches, it was discovered that instantaneous phase is one of the universal features of tasks, especially writing tasks. Therefore, this paper focuses on a force-amplitude/phase control of a 1 degree of freedom system. In this paper, the SISO system is extended into a MIMO system defined in a complex plane by using Hilbert transformation. The amplitude/phase controllers of a proposed system are designed in the complex plane, respectively. The proposed system is expected to control force amplitude and force phase of the system, independently. The performance of the proposed system was evaluated through several simulations.

This paper proposes a way to calculate a grasping force that could adapt to a variation of mass of a grasping object. In order to grasp an object, resultant force vector consisted of grasping force and friction force has to be within a friction cone. In conventional method to grasp an object, mass of a grasping object or acceleration caused by transportation have to be measured in order to calculate an optimal grasping force. However, it is difficult to measure these parameters quickly; therefore grasping an unknown object is difficult. The proposed method is a data-driven approach using bilateral control. While human grasps an object, the condition that a resultant force vector is within the friction cone, then the direction of the resultant force vector in the stored human motion are reproduced so as to control grasping force. By using the proposed method, it is able to grasp an object without any need to measure the mass of the object. Experiments are conducted in order to show the validity of the proposed method.

This paper proposes a design method of command compensator with transition of state for command shaping. In the future, a robot is required to be introduced in human society. In this case, force control of high performance is important element of a robot control system. Moreover, it is important that a robot automatically changes a command in accordance with circumstances and a control specification. When the command is changed, there is some possibility that the command becomes discontinuous. Then, it is dangerous because robots might do unexpected motion or become out of control. Therefore, the proposed method focuses on a command difference between pre-transition and post-transition. Moreover, the proposed method considers transition of state. By using the proposed method, a discontinuity of command is solved and the smooth force control and motion can be realized in accordance with circumstances and a control specification. In the experiments, force control having some commands in order to realize a pushing motion stably and repeatedly is applied. The validity of the proposed method is confirmed through experiments.

Network control systems have been attracting attention to manage sophisticated task at a remote place where people cannot enter. However, jitter which is a fluctuation in time delay for an information to be transmitted, is a serious problem in network control systems because it deteriorates the performance of the system. Therefore, designing control system considering jitter is extremely important. Thus, this paper proposes a novel method to reduce the effect of jitter to the system under time delayed conditions. This is done by utilizing two filters that have inverse relationships and an error corrector when information is transmitted via network. The validity of the proposed system is confirmed experimentally by implementing the proposed filter to a one way information transmission and a network control system. Also, the experimental results of the proposed method is compared with conventional methods to show the effectiveness of the proposed method.

Bilateral teleoperation realizes tactile sensation transmission between distant places by realizing two control goals, which are synchronization of position response and the realization of the law of action and reaction. However, a communication delay between the systems deteriorates control performance of the whole system. Bilateral teleoperation that achieves simultaneity property, which is one of the control goals in bilateral control, was proposed by the authors. The system realizes to independently control position and force responses, which was not achieved in the conventional methods, by using a model of a delay time to buffer the force information. However, it is well known that delay time varies in network systems. Therefore, in this paper, control performance of the system in front of modeling error is analyzed and the effect caused by the error is compensated by using a phase-lead compensator. The compensation controller is designed to have enough phase margin and better position tracking performance. The validity of the proposed method is confirmed through experiments.

Rendering technique of tactile sensation is necessary to communicate and share feelings between remote locations. This research focuses on thermal sensation, and not only precise rendering of tactile information but also environmental identification is conducted. Thermal sensation is changed depending on thermal impedance such as thermal resistance and thermal capacitance. In this paper, the identification method of thermal impedance is proposed, and rendering the identified thermal parameters is conducted. The method consists of identification using thermal conductivity and reproduction based on thermal impedance control. In order to identify thermal parameters of an object, an iterative least square technique is used. The proposed method is able to render thermal response precisely for human because thermal impedance is identified based on heat flow in the same way as human skin sensation. The validity of the proposed method is verified through some experiments.

Thermal sensation is important for communication tool and multimedia fields as an element of tactile sensation. This research focuses on thermal sensation, and aims to render the sensation spatially. Most of conventional studies present thermal sensation by directly contacting thermal device such as a Peltier device. In this case, it is difficult to get thermal information by the movements of their hands such as tracing. In this paper, a control method for rendering thermal sensation with the consecutive detection of contacting points is proposed. In order to consider temperature distribution of the system, a copper plate attached to the Peltier devices is regarded as a thermal system. A method to detect multiple contacting points is proposed, which uses the value of heat inflow estimated from heat inflow observer, and temperature control at the detected points is conducted. This method enables the system to render spatial thermal sensation in response to the movements of finger. Experimental results show the viability of the proposed control system.

The researches have been ongoing on various vibration control methods for resonant system. Reflected wave rejection-based vibration control is one of the vibration control for resonant system which considers high order resonances owing to the wave equation. However, the conventional reflected wave rejection-based vibration control mainly focuses on the position control, the torque/force control of the resonant system has not been researched. In this paper, reflected wave rejection-based vibration control is extended to the torque/force control of the resonant system which is modeled as wave equation, and the torque/force control of the resonant system based on a wave-based load disturbance observer is proposed. In the proposed method, the vibration is suppressed by the reflected wave rejection, and torque control is constructed based on an environmental torque estimated by the wave-based load disturbance observer. Additionally, the design procedure of control gains are presented. The validity of the proposed method is confirmed by the experimental results.

In order to achieve contact tasks precisely, it is necessary to suppress position (or velocity) and force errors. The motion-loading system is effective method to achieve this purpose, since position (or velocity) and force information can be controled at the same time. However, when the contacting environment has the different size or location, force error occurs at first contact moment. In this paper, time-adaptation control with multi-degree-of-freedom (MDOF) system is proposed. The most important force value is set as control goal to calculate shift time in this method. Since time adaptation algorithm works to suppress the force error, the control goal is achieved. Therefore, this method can adapt to the size difference of the contacting works. By using this method, high quality manufacturing with contact task can be achieved in industrial field.

This paper presents a novel concept of performance index for evaluating the scaled haptic transmission in a micro space. Bilateral control based on acceleration control enables human to acquire and render a tactile sensation. In order to realize the applications of a tactile sensation as well as audio and visual information, editing tactile information will be considered. However, the signal which is measured by a digital sensor is remarkably affected by a high-frequency domain disturbance or quantization error. The purpose of this paper is to expand the previous performance index with the interference of a high-frequency domain disturbance and quantization error. Considering the novel performance index, a modal space filter to extract expectation value is conducted by employing a Kalman filter for avoiding destruction of a micro object. In the experiments, the trade-off between a disturbance matrix and a quantization error matrix is confirmed, and 1000 times scaled haptic transmission that contacts with water fleas is achieved.

In rehabilitation, a robot is useful and effective for repetitive trainings. However, few rehabilitation robots have adaptability to personal difference. Therefore, an index for quantitative assessment of the difference is required to achieve the adaptability. In conventional research, a hand stiffness is used as one of the indeces, and a dynamic hand stiffness is measured only in 2 dimensions. Then, in this paper the dynamic hand stiffness of reaching motions is measured in 3 dimensions by using an arm robot. The experimental results are represented as stiffness ellipsoids. Moreover, the results are compared with the ellipsoids in 2 dimensions. From these results, it is revealed that the characteristics of the dynamic hand stiffness in 3 dimensions is different from that in 2 dimensions. The fact implicits that a human controlls his/her arm stiffness not in work space but in joint space.

With the technological development of robotics, a bilateral control based on acquiring and rendering tactile sensation, which is one of the human five senses, enables human to manipulate by using wireless network. In order to realize the applications of haptic transmission as well as audio and visual information, the research field of haptic data compression will be considered. However, information volume is restricted by a communication bandwidth in the scaled haptic transmission provided from Shannon-Hartley theorem. Therefore, the purpose of this paper to clarify the compression method of haptic data by using a delta-sigma modulator in quantized scaling-bilateral control. In the proposed system, 1st-order delta-sigma modulator can be transformed as the high-pass filter and it is possible to suppress quantization error. To evaluate scaled haptic transmission, the hybrid parameters including the interference of quantization error are analyzed by the Bode diagrams. Finally, the experimental results show the stable operation as well as the improved performance to compress the position and force information.

The development of motion control enables robot manipulators to reproduce the humans motion as known as motion-copying system. This epochal system is expected to automate delicate tasks that has been treated by human workers. Moreover, the motion-copying system can reproduce the stored motion at high speed by scaling time-axis of the stored motion-data. Using this technique, the efficiency of the industry will be substantially improved. However, there are still some problems that obstruct the practical use of the high speed motion-reproduction. One of the serious problem is how to change the reproduction speed. Although the most simple method is varying the sampling period of the system during the motion-reproduction, this method has to deteriorate the performance of the motion-storing system. In addition, multiple times motion-storing are required to realize several reproduction speed. In this paper, a novel interpolation method based on delta-sigma modulator and the weighted average filter is proposed and evaluated for the implementation of the fractional speed motion-reproduction. The presented interpolation method can achieve the high speed motion-reproduction without degrading the performance of motion-storing system, moreover, it can generate arbitrary reproduction speed from only one-time motion-storing. The effectiveness of the interpolation method is evaluated through several simulations and experiments.

This paper proposes a motion-reproduction method for a multi degree-of-freedom system. For extraction and reproduction of haptic information, motion-copying system was previously proposed. However motion-copying system has a drawback; it is difficult to reproduce the saved motion when the environmental configuration in the motion-loading phase is different from that in the motion-saving phase. There are many methods for adapting variation of environmental configuration. However, in conventional methods the orthogonal axial motors are controlled independently. In the tracing motion, there is a friction and interference between orthogonal axes occurs. Thus, it is impossible to reproduce the saved motion when the coefficient of friction is varied. In this paper, amount of the force information is focused and motion-reproduction method which controls synthetic force using two degree-of-freedom system is proposed. The synthetic force is a total magnitude of the force information and it is important to conduct a human motion. To show the validity of the proposed method, experiments were conducted.

In the field of industrial processing, there are still many parts performed manually. For this problem, a motion-copying system was proposed to put into practical use to create the labor force instead of human. Moreover, motion data that can be processing and reproducing are needed to extend the viability of motion-copying system. In this paper, a temporal compensation method is proposed in order to maintain the reproducibility of saved human motion. Reaction force of loaded motion data is different from saved one when the data is processed by a spatial scaling. Here, a temporal compensation that is based on the variable temporal scaling is introduced in order to make equal reaction force of saved human motion data and that of loaded human motion data. The temporal processing of motion data is based on the first-order hold interpolation. It can process the motion data and solve the resample problem that occurs when discrete motion data is treated at the same time. Validity was confirmed by the experiments.

In haptic communication via the network, transmission period is not able to be designed uniquely since it restricted by the line bandwidth, transmission protocol, hardware constraints and so on. To address this problem, downsampling is often employed. Additionally, to enhance the performance of downsampled system, multirate control is proposed. However, the quantitative analysis on downsampling and multirate control are not treated. Therefore, this paper treats downsampling and multirate control system, and performs quantitative analysis by using hybrid parameter. In order to reveal the most effective combination of holder and single or multirate, holders (ZOH, DFOH and PFOH) are considered explicitly, and it is formulated to Laplace domain. The effectiveness of each combination is verified through experiments.

This paper presents the performance validation of the motion control system for integration force and trajectory information. To realize the implementation high-quality motion that includes contact and non-contact motion to robot system, two contradictory systems; force and trajectory control should be synthesized in one control axis. In order to respond to the request, we proposed a motion synthesis system which integrates two controller in frequency domain. This paper firstly will discuss the acceleration control based force control and position control respectively. And it is also shown that the force reproducibility is decided by contact object's impedance. Then, performance analysis of the motion synthesis system will be shown. From the results, it is confirmed that the motion synthesis system satisfies two control goals without depending on impedance or presence of contact environment. The validity of the design approach is verified by experimental results.

Nanoscale motion control is required for miniaturization and performance improvement of mechatronics systems. In motion control at nanometer scale, disturbances which do not affect the system at macro scale might greatly influence the control performance. The torque ripple caused by distortion of current is one of the most serious disturbance elements and should be eliminated. To address this problem, the method of the filter designing is proposed in this paper. The effect of the distortion of the current can be reduced by designing the filter in disturbance observer to have low-pass filter and band-stop filter. This paper shows the design method and the stability of force control based on the composite filter. By using high-precision acceleration control based on the proposed method, persistent oscillation can be suppressed, control accuracy can be improved. The validity of the proposal is confirmed by experiments.

This paper proposes a novel method to realize simultaneity property and operational force reduction in a bilateral control system under communication delay. Bilateral control system realizes bilateral teleoperation with force sensation feedback to the operator, regarded as the next-generation communication tool transmitting force sensation. However, communication delay between the systems destabilizes the whole control system and the performance is also deteriorated. In this paper, the effect of the time delay is analyzed in a modal space, and considering that the operation is done by human, the interferences between the modal space is removed within the low frequency area that human operates by utilizing the buffered information. As for the stabilization purpose, phase-lag compensator is utilized. The validity of the proposed method is confirmed through experiments.

Recently, “haptic recording” is attracting attention. Haptic recording is the concept for recording and loading of human motions like as audio-visual information. Motion-copying system is the technology which reproduces human motion based on position and force information for this and the applications to various fields is expected. Training system is the important application of this system. For more efficient training, the system for an individual is desired. For this purpose, it is important that the input force by trainee (how a trainee moves) is extracted. However, such a method for extracting only human input force in motion-loading is not considered. Therefore, in this paper, the estimation method for human force in motion-loading step is proposed. In the proposal, by utilizing the saved motion data effectively, not only human motion but also the environment information can be obtained. This is the one of the characteristics of motion-copying system. By using this characteristic, the environmental impedance is identified in motion-saving and the only reaction force from the environment in motion-loading is estimated. From these information, human input force is extracted. In addition, as application of extracted trainee force, one of the structure for training system by utilizing the motion-copying system is presented. This structure can vary the effect from the saved motion and trainee to the reproduced motion arbitrarily. Finally, the validity of the proposed method is confirmed by experiments.

This paper proposes a reduction method of stochastic disturbance that is focused on haptic information in the micro space. Presently in the industry, haptic information is attracting attention as the tertiary media following audio and visual information. Haptic information has characteristics of bidirectionality and scaling that extended human ability by using master and slave robots. Especially, high-precision performance including haptic information is required by the industrial robots such as a field of medical care. In the conventional method, however, desired motion cannot be achieved precisely under the influence of the stochastic disturbance like sensor noise in the minute region. High precision of the motion control is closely related to reduce the influence of the sensor noise and perform acceleration control. Therefore, this paper focuses on resonant filter that is presented the study of quantum physics that treats a probabilistic phenomenon. The control system that considered the stochastic disturbance is proposed by constructing the disturbance observer based on the complex equivalent circuit of Schrödinger equation. The viability of the proposed model and the reduction of the oscillation are confirmed by performing analysis and experiments in scaling bilateral control.

Bilateral control enables human to transmit body sensation to remote area. Bilateral control gives a sense of existing without movement of body, and realizes pseudo-teleportation to everywhere. Bilateral control technology produces a sense of expansion of a body, so this technology is needed to apply to multi-DOF or non-mechanical systems. To expand the range of application, the scheme of bilateral control needs to be more general. The basic law of energy bilateral control is energy conservation law, which is the first principle for all physical systems. This paper proposes energy bilateral control as a generalized bilateral control. Energy bilateral control is an explicit energy control, which enables different structural systems to be implented bilateral control. Energy bilateral control also show a new interpretation about bilateral control: hybrid of internal energy and power flow control. The effectiveness of the proposed methods is verified by experimental results.

This paper proposes a motion-copying system using modal information for motion reproduction. A motion-copying system has been proposed as the system of saving and reproducing a human motion. However, the conventional system can not reproduce the stored motion when an environmental location is changed between a motion-saving phase and a motion-loading phase. Then, a velocity-based motion-copying system has been proposed. Although this system can reproduce the stored motion once the system contacts with the environment, it takes time to adapt the different location of environment. To reproduce the human motion which contains vivid haptic information, it is needed to construct a much strict motion-reproduction system. Therefore, the motion-copying system using modal information is proposed in this paper. The proposed method stores and reproduces the estimated force and the differential mode of position responses, while the conventional method uses force and position responses of the human motion. By the proposed method, the stored motion can be reproduced precisely when the environmental location is unknown. The validity of the proposed method is confirmed by experiments.

Safety operatons are one of most important issues in human society, when robots are introduced there. Recently, human-assist systems acting directly on humans have been developed and opportunities for humans to touch robots are increasing. However, active actuators are often used to generate force in order to perform any tasks and they constitute a possible danger to humans when they are loss of control. Then, stable passive systems would be substituted for active ones. Passive systems will not generate force by themselves. Only when external force acts on them, they generate reaction force. Considering these properties, passive systems are stable and appropriate for the human society because they would be little risks for humans when they are loss of control. In this paper, the passive actuator and the active actuator are combined together in order to generate the torque. The passive system is used like a clutch. By control of the current of passive system, the output torque from MR-fluid actuator is also controlled. The maximum output of MR-fluid actuator is limited by shear stress of MR fluids. By these properties, MR-fluid actuator has high safety for humans. In this paper, the velocity control of MR-fluid actuator is proposed.

This paper proposes the new frequency model of haptic information focused on the vibration component in friction force. Recently, haptic information is attracting attention from many areas as the tertiary media following the audio and visual information. However, due to the characters of the bidirectionality and self-reference, treatment is difficult as compared to the other sensory information. Unified representation method still not been established. Therefore, this paper focuses on the vibration components of friction force in rubbing motion against environmental surface in particular. The friction force in rubbing motion is measured for broadband by using the 2-DOF system constructed by two linear motors. For the quantitative evaluation of the frequency domain, cepstral analysis which is the method for voice-print analysis is applied. The effectiveness of the proposed model is shown by performing experiments and analysis with three different environmental surfaces. Moreover, this paper presents the identification for each parameters of the model from the acquired data, and construct a accurate model of the friction force for each environment.

Recently, in the medical care, in order to achieve micro manipulation, many robots are researched. This paper focuses macro-micro bilateral control system which is one of the micro manipulation robots. Macro-micro bilateral control system consists of position control and force control. Therefore, in this paper, in order to achieve high accuracy macro-micro bilateral control system, high accuracy position control and force control is implemented. Firstly, the high resolution encoder is used. A low friction structure is used to force control. In addition, nominal mass is important for accurate force observation. Therefore, identification of mass is proposed. Macro-micro bilateral control system is implemented with proposed structure and identified nominal mass.

Bilateral control that can render a mechanical impedance of remote object has recently been researched. However, most of the researches assume that master and slave systems of bilateral control have enough bandwidth for transmitting generated torque to an end effector. In practical situation, there might be cases in which mechanically fine systems cannot be utilized. This research discusses a bilateral control in which master side of systems has low control performance. In order to compensate for the interference of position responses with force control caused by the difference of the performances, disturbance observer is constructed in common modal space of bilateral control system. The device characteristics are considered in actual compensation so that the compensation itself does not become the new interference term. The performance enhancement of haptic system relating to contact motion will be shown by simulations and experiments.

Recently, motion control technology has been developed. In this research field, motion-copying system is expected to use some kinds of education in the future. Motion-copying system consists of two systems. One is the motion-saving system, and the other one is the motion-loading system. The structure of motion-saving system is similar to bilateral control system. In the system, human motion is abstracted and stored into motion-data memory. In the motion-loading system, human motion is precisely reproduced using the data in motion-data memory. Conventional motion-copying system is not able to treat the case condition of work object is changed between motion-saving system and motion-loading system. Some approaches are proposed, but most of approaches are related to the position gap. The case environmental impedance has changed is not sufficiently discussed. Therefore, this paper proposes motion-copying system for different environmental impedance. By the introduction of motion qualia into the motion-copying system, the effect of different environmental impedance is compensated. Validity of the proposal is confirmed by simulation results, and good agreement is observed.

In this research, a novel structure of macro - micro bilateral control for reduction of quantization noise and interference in the modal space is proposed. Macro-micro manipulation is needed for various fields such as minimally invasive surgery and investigations. Scaled bilateral control is one of key technology for micro manipulation. However, performance of scaled macro-micro bilateral control is deteriorated because of enlarged quantization noise and interference between force and position control. In this research, Kalman Filter base State Observer is extended and constructed in the common and differential modal space in order to reduce effects of enhanced quantization noise which is enlarged by scaling factor. In addition, interference and disturbance are eliminated by using a structure based on a disturbance observer. Validity of proposal is confirmed by simulations and an experiment.

This paper proposes the best topology in multilateral control system. Multilateral control system is a control system which enables to share tactile information between several subsystems. Specifically, every subsystems communicates position and force information each other to achieve control goal. As shown above, the information flow is bilateral in multilateral control, and when sharing haptic information between several remote places, there occurs delay time in each communication links. When there exists delay time inside control system, the system starts to destabilize and haptic information deteriorates. In order to prevent the deterioration of the information, the optimal topology regarding position information is realized in this paper. The proposed method can be applied to a system where the delay time of each communication links is different from each other. The validity of the proposal is confirmed by experiments, and the results show that the degradation of haptic sensation under communication delay is prevented.

Recently, technology for recording and loading of human motions has been attracted attention in various fields. For that purpose, motion-copying system was proposed. This system saves and reproduces human motions on the basis of position and force information. Conventional motion-copying system is not able to reproduce the saved motion to the environment when an unexpected force is applied to the system. To solve this problem, robust motion-copying system has been proposed. However, in applying this system to education field, it is important that the influence from an input of trainees to reproduced motion is varied. Therefore, this paper proposes a novel motion-copying system in which the effect from human input to reproduced motion toward the environment is variable. By the proposed method, it is possible to change the effect from the unexpected force by human to the reproduced motion to environment according to the learning level of trainees. Finally, the validity of the proposed method is confirmed by experiments.

Several time delay compensation methods for teleoperation systems have been researched for a long time (e.g. Smith predictors, communication disturbance observers, etc). Based on the communication disturbance observer, the authors have proposed a vibration suppression scheme for resonant systems, based on reflected wave rejection and a wave compensator. From this method, it is found that vibration in resonant system can be suppressed by making use of a time delay compensation method and it is observed that a reflected wave induces vibrations. Taking a dual approach, this paper proposes a time delay compensation method, based on our previously developed reflected wave rejection, used for the vibration suppression in the resonant system. Firstly, a wave representation of time delay system is derived and an equivalence of wave and time delay systems is clarified. It is also clarified that a cause of vibration in the time delay system is a reflected wave as well as in a resonant system. Finally, it is shown how the reflected wave rejection can be seems as a time delay compensation method, to be used in time delay systems. The validity of the proposed method is verified by the experimental results.

This paper proposes a simplified integrated reproduction of saved motion components. For storing and reproduction of haptic information, a motion-copying system was proposed. By the motion-copying system, for example, techniques of experts can be reproduced by robots to improve work efficiency. In the skill reproduction by robots, it is possible to reproduce the various motion by integration of the saved motion components which are stored in advance. In fact, the motion which is required some processes of works is achieved according to integrated reproduction of these motion components. By using the proposed method, the design procedure of integration of the motion components is very easy, and the saved motion components are integrated smoothly. Performance of the proposed method is compared with the linear interpolation method by experiments, and the validity is confirmed.

Recently, a field requiring advanced techniques demands a new education system designed to reproduce the haptic sense. The environment-copying system, in which a haptic data is stored and reproduced, has been studied. However, the conventional environment-copying systems reproduce only the haptic sensation on the environmental surface. The haptic sensation is not only changed by the mechanical impedance but also some circumstances, how the condition is and how the operators move the environment. Then, this paper proposes the environment-copying system for the multi degree-of-freedom motion. This paper treats the grasping/manipulation motion as multi DOF motion. In the grasping mode, the mechanical impedance of the environment is identified. On the other hand, the frictional force and the fictitious force are identified in the manipulation mode. Loading the identified impedance and force, the operators feel as if they grasp and manipulate the environment. The validity of the proposal is confirmed by experiments.

Generally, the flexible robot system can be modeled as the two-mass system which consists of a motor and load connected by a spring coefficient. In order to achieve accurate tracking objectives, the correct of parameter identification in the model based controller is necessary. The objective of this paper is the parameter identification of a spring coefficient of flexible robot system. The multi-encoder based disturbance observer (MEDOB) and load side disturbance observer (LDOB) are employed to identify a correct spring coefficient parameter of flexible robot system. The comparison of external force estimation between MEDOB and LDOB is used to find the correct value of spring coefficient. By using the proposed identification method, it is simple to identify the spring coefficient and easy to implement in the real flexible robot system. The effectiveness of the proposed identification method is verified by simulation and experimental results.

Recently, real world haptics are researched. In this paper, the environment copying system is focused. The environment copying system is one of the real world haptics techniques. The environment copying system achieves saving and reproduction of real world environments haptic sensation. The environment copying system needs environment model. The environment model calculates environment reaction force. Thereby, haptic sensation reproduction is achieved. The conventional model consists of a pair of spring and damper. It can not reproduce oscillation of the environment. In this paper, the model based on wave equation is proposed. It can reproduce oscillation of the environment.

Humans can perceive thermal sensation at most in hundreds of milliseconds after the contact with external objects. This point indicates that the temperature of thermal display must be controlled with the tracking time that is shorter than the perception time, in order to ensure the sufficient performance for rendering of thermal sensation. This research utilizes Peltier device as a thermal actuator of the system, and constructs the temperature control system by combining heat disturbance observer and local temperature feedback in order to enhance the response speed of the system. The experimental results show not only that the designed system can track the reference with sub-second settling time, but also that the system is well nominalized to simple second-order system even in the short settling time, which means that the transient response is easily adjusted.

This paper proposes an estimation method of functional mode in grasping/manipulation motion in scaled bilateral control system. In the conventional method, however, it is presupposed that functional-mode is predefined. By using proposed method using principal component analysis(PCA), time-variable functional mode of control system and human motion is directly estimated from motion information without considering predefined functional mode. In grasping/manipulation motion in scaled bilateral control, it is possible to estimate the principal functional mode and evaluate the performance of control systems. Validity of the proposal is confirmed by experiments.

As an academic field which deals with transmission and reproduction of human tactile information, there exists real-world haptics. Bilateral control is an important technology of real-world haptics to transmit tactile information between operators and environment. It is desirable for master or slave systems to work autonomously in order to adapt themselves for motions of operator or environment. In addition, varying the number of driven systems contributes energy conservation and wastes reduction according to change of connection between subsystems. In this paper, a bilateral control system is proposed which realize adaptability to environmental variation of motion and energy conservation by varying system configurations. The variance of system configurations is derived from expression of human fingers as a dynamic model of informationally connected system based on ability to oppos the thumb. ability to oppos the thumb is a necessary function of human fingers and an element which makes the connection vary dynamically. The model is applied to three-fingered bilateral control system. By using proposed method, flexibility to variation of environmental movement and higher concentration to the main tasks and energy conservation are obtained for the bilateral teleoperation. Experimental results show validity of the proposed method.

Recently, the aging of workers and craftsmen are becoming a great issue because of low birthrate and longevity. The advanced skills of craftsmen is a precious property. The “motion database” that realizes recording, searching, and reproduction of human motions is considered to be effective in overcoming this problem. By saving information about advanced techniques in the motion database, these techniques can be reproduced anytime, anywhere. By copying the technique of motion database to robot, technical tradition and power assist are possible.

This paper proposes a force control of a two-mass resonant system based on modal transformation. In the conventional force-control method in resonant system, the control goals are not clearly defined from the point of the view of control stiffness. Moreover, there is a problem that it is needed to know value of an environmental stiffness for setting force gain. Therefore, in this paper, the control stiffness in the case of force control of the two-mass resonant system is defined on the modal spaces which are composed of rigid and torsional modes. Concretely speaking, in the force control, it is defined that a control stiffness of a rigid mode should be zero. Based on the control stiffness, a force control of the two-mass resonant system is designed. Vibration suppression is conducted in torsional mode. On the other hand, in rigid mode, force control is conducted. The validity of the proposed method is verified by both simulation and experimental results.

Recently, following visual and audio information, transmission of tactile sensation has actively been researched in the field of telemanipulation. For the realization of haptic transmission, master and slave systems should be utilized and these systems have to be connected via network. In communication via network, it is known that a communication delay, packet loss and jitter cause undesirable effects on control system. Moreover, in wireless mobile communication, there is a problem that the error rate and the jitter are increased by fading. The adverse effects caused by fading are mainly dealt with by error correcting technologies of communication system. For example, there is convolutional code and viterbi decoding in data link layer. In addition, the check sum function is used in transport layer. This paper pays attention to the influence of frequency change of the communication caused by fading on mobile haptic communication. Moreover, this paper evaluates the performance of wireless haptic communication in terms of two error correcting technologies.

This paper proposes integrated reproduction of saved motion components by using velocity based motion-copying system. A motion-copying system has been studied in order to store and reproduce human haptic information. The motion-copying system is expected to be applied various applications such as industrial applications, training system, medical and welfare human assist, and so on. Above all, this paper considers the skill reproduction by robots. In this field, it is possible to reproduce the various motion by integration of the saved motion components, and the skill which is required some processes of works can be realized according to integrated reproduction of saved motion components. In conventional methods, however, the environmental location is required to know in the motion-loading phase. On the other hand, the proposed method can reproduce the saved motion components when the environmental location is unknown in the motion-loading phase. Finally, performance of the proposed method is compared with the conventional method by experiments, and the validity is confirmed.

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.