Till date, various seven-degrees-of-freedom (7-DOF)robot arms have been developed globally. In general, the robot arms utilized in factories are required to possess speed, power, and accuracy. They are isolated from humans using a fence to ensure human safety. However, a home robot should work near humans at an appropriate speed without a fence. One approach to meeting this requirement involves the installation of various sensors on the robot to control and stop the robot safely even if a collision has occurred. However, a robot system is complicated and expensive. In order to give inherent safety to the robot, we should lighten the robot arm. In this study, a 7-DOF lightweight arm with a wide wrist-motion range is introduced. The weight of movable parts is approximately 2.87 kg. To achieve such properties, we propose the use of three mechanisms: a shoulder mechanism with hollow cylinders, a wrist mechanism with a wide workspace, and an integrated wrist and elbow mechanisms of high power. To verify its feasibility, a prototype of the robot is designed and developed. The experimental results demonstrate its powerful performance and wide workspace of the wrist.

We have been studying an omnidirectional driving gear mechanism that can generate thrusting force in an arbitrary direction on one surface, which may be flat or curved. This omnidirectional gear is driven by spur gears that are perpendicular. When one spur gear rotates to drive the omnidirectional gear, the other slides between the teeth of the omnidirectional gear and vice versa. In this paper, we introduce gears with passive rollers to reduce the frictional resistance with a mechanism including smooth rolling motion of conical or flat passive rollers, which can boost the power transmission efficiency of the omnidirectional driving gear system. We also confirmed another useful function of this gear with passive rollers as a worm wheel to transmit power from a worm gear with higher energy efficiency than an ordinary worm wheel.

This video shows multiple omnidirectional driving gears to realize smaller size and weight than the ordinary X-Y stages. The examinations of different materials and sizes of the gear teeth to improve the performances of the omnidirectional driving gears are the main progress of this paper from our previous reports [1].

In this paper, the principles and the actual configurations of the omnidirectional driving gear mechanism that was implemented by the authors were described. The validity of the proposed structure was also confirmed and its basic characteristics understood through experiments using the actual prototypes.

The 20-DOF miniature humanoid “MH-2” designed as a wearable telecommunicator, is a personal telerobot system. An operator can communicate with remote people through the robot. The robot acts as an avatar of the operator. To date, four prototypes of the wearable telecommunicator T1, T2, T3 and MH-1, have been developed as research platforms. MH-1 is also a miniature humanoid robot with 11-DOF for mutual telexistence. Although human-like appearance might be important for such communication systems, it is unable to achieve sophisticated gestures due to the lack of both wrist and body motions. In this paper, to tackle this problem, a 3-DOF parallel wire mechanism with novel wire arrangement for the wrist is introduced, while 3-DOF body motions are also adopted. Consequently, a 20-DOF miniature humanoid with dual 7-DOF arms has been designed and developed. Details of the concept and design are discussed, while fundamental experiments with a developed 7-DOF arm are also executed to confirm the mechanical properties.

As ordinary dual-axis driving mechanisms in X-Y directions, for example, commercially available X-Y stages with ball screws are familiar. However, such driving mechanisms have two stages, namely both upper and lower linear actuators, the latter of which must generate sufficient thrust to carry large weights, including that of the upper actuator mechanism, which has hampered efforts to achieve suitably fast and smooth driving motion due to the inertial force effect. It is also difficult to achieve a small and slimline driving mechanism with such overlapping two-stage structure. In these ordinary two-stage driving mechanisms, the motion of the X-Y stage can be disturbed by the wires of the upper actuator. In this research, we have considered the abovementioned problems, and propose a new omnidirectional driving gear mechanism that enhances its driving area from the normal X-Y plane to convex and concave curved surfaces respectively, and even various combinations of both. The smoothness of basic omnidirectional motion and effectiveness of the driving method of this proposed omnidirectional driving gear mechanism have been confirmed with several experiments involving our setups.

In this paper, additional manipulating function for limited narrow space with omnidirectional driving gear was described. The validity and advantage of the proposed function was also confirmed through experiments using the actual prototype of the planar omnidirectional driving gear units for the parallel gripper.

It is well known that parallel mechanisms have several advantages, namely high power, rapidity and high stiffness. However, their workspace is limited due to interference of each chain. In our previous work, to expand the workspace of Delta mechanisms, ball bearings were employed instead of ball joints. Although this allowed a relatively wide workspace to be achieved, the clearance gap of the ball bearings introduced undesirable flexibility, while mechanical limitations persisted. In this paper, to tackle these problems, a novel parallel mechanism with wire-pulleys is proposed. The basic structure of the new mechanism is the same as that of the conventional Delta mechanism, but wire-pulleys are employed instead of a parallel four-bar mechanism. The key feature of the wire-pulleys is its lack of mechanical limitations. A prototype has been designed and developed, which achieves a wider workspace and reduced backlash. In addition, the total parts quantity has declined by more than 25%. Fundamental experiments show its potential.

With aging, human skin develops a dry condition called senile xerosis. The skin lesion can be prevented by daily skin care such as applying an ointment containing moisturizing factors several times a day. Aged persons, however, have difficulties in accessing the back and rely therefore on nursing care for such treatment. Unfortunately, in underpopulated areas such nursing care may not always be available. To tackle this problem, the concept of a skincare robot is proposed. The feasibility of the concept is then confirmed by designing a real skincare robot and by performing experiments for applying ointment on human's back. The robot developed is able to recognize the shape of the body, to plan the appropriate motion paths for the hand, and to execute the task without applying any excessive forces.

This special section editorial defines home automation and investigates the various approaches to home automation which can be used to facilitate independent living. The paper concludes by introducing the three technical papers that are part of the special section.

In general, either a position or a velocity command is utilized during teleoperation. However, when teleoperating a free-flying robot in space, it is difficult to ensure the commanded position or velocity because of the specific system dynamics. An acceleration command is much more appropriate. However, it is very difficult to handle the acceleration command for the operator. In this paper, a new predictive display technique named "predictive motion display" is introduced to overcome the problem. The experimental results show that the proposed method reduces both task completion time and collision frequency by 33% and 86%, respectively. In addition, the effectiveness is discussed based on a simple feedback control model

This paper addresses the problem of naturally looking and energy efficient walk of biped humanoids. We presuppose that such walk requires motion control capability around kinematic singularities, such that the knee can be fully extended. This problem is tackled by adopting the singularity-consistent method developed for manipulator motion control at and around kinematic singularities. We implemented the method with a HOAP-2 humanoid robot, demonstrating stable static walk as a first step in this direction

A kinematic redundancy resolution approach for the S-R-S manipulator is introduced which uses arm plane orientation as the redundancy resolution criterion. The approach can handle both kinematic and algorithmic singularities in a consistent way, without introducing motion instabilities, yielding thereby motions that can be predicted easily by a human operator. The method is verified by experiments with a seven-DOF Mitsubishi Heavy Industries PA10-7C arm and data from both simulations and experiments is presented.

In our previous research, we developed space robot teleoperation technology to achieve control from the ground of effective manual manipulations in orbit. To solve the communication time delay in the space robot teleoperation, we propose a mixed force and motion command-based space robot teleoperation system that is a model-based teleoperation. Moreover, we have also developed a compact 6-degree-of-freedom haptic interface as a master device. The important features of our teleoperation system are its robustness against modeling errors and its ability to realize the force exerted by the operator at the remote site. We introduce a new control method, which modified our model-based teleoperation system, to control the real robotic system Engineering Test Satellite VII manipulator. Surface-tracking and peg-in-hole tasks have been performed to confirm the effectiveness of our system. The experimental results obtained with our system including the haptic interface demonstrate its ability to perform these tasks in space without any major problems. We also evaluated different master device approaches for the model-based space teleoperation system. For this purpose, we used two methods, which are a master-slave (MS) approach and a force-joystick approach. Our results show that the MS approach is the best control method for contact tasks in which the directions of motion of the slave arm and of the operator's input force are different, as in the surface-tracking task.

The SC method is applied to a 7-DOF manipulator arm with a spherical wrist and zero joint offsets, such as the Mitsubishi Heavy Industries PA-10 arm. We obtain two vector fields for driving the positioning subchain and one vector field for the wrist, in analytical form. The former two vector fields are used to realize decoupled motion control of the end-effector and the arm plane, respectively. No additional singularities are introduced, and motion through kinematic singularities is stable and cyclic.

The shortage of human resources on the International Space Station (ISS) is becoming a serious problem. To tackle this problem, smart robot systems that support human activities in space should be developed. In this paper, a new space robot system named "Intra-Vehicular Free-Flyer System (IVFFS)" is proposed. The IVFFS supports not only non-contact but also contact tasks during intra-vehicular activities (IVA). To accomplish such requirements, we introduce a prototype model called "Space Humming Bird" (SHB) which has a variably structured body to satisfy both safety and dexterity requirements. Furthermore, several SHBs can be combined to achieve more complicated tasks. To confirm the feasibility of our concept, a CG simulator is developed. In addition, several operator support techniques are incorporated into the tele-operation system.

The SC method is applied to the positioning sub-chain of a seven-DOF with zero joint offsets, such as the MHI PA-10 arm. Via the two vector fields obtained, decoupled motion control of the end-effector and the arm plane, respectively, can be realized. No additional singularities are introduced, and motion through kinematic singularities is stable.

During teleoperation, when the operator's attention is focused on controlling the end-effector's motion, it is very difficult to recognize possible link collisions. Such collisions may damage the environment or the links seriously, because usually the links have no sensors. We propose a so-called "virtual radar" which displays the collision information related to the motion of the whole manipulator at the end-effector level. The computer checks for unreachable areas due to the presence of obstacles and displays the appropriate information mapped on the task space using 3D graphics. This would enhance the reliability of the system. When applied to a 6-DOF manipulator, the possible collision space must also be 6-dimensional. Hence it is difficult to visualized and comprehend by the operator. To tackle this problem, the virtual radar displays the collision information by means of a deformable sphere and various patterns on it. The effectiveness of this method has been verified by experiments with a real telerobotic system.

In this paper, we present a method for analyzing parallel mechanism stiffness including elastic deformations in the structure. In our previous works, we developed a compact 6-DOF haptic interface as a master device which achieved an effective manual teleoperation. The haptic interface contains a modified Delta parallel-link positioning mechanism. Parallel mechanism is usually characterized by a high stiffness, however, it is reduced by elastic deformations of both parts and bearings. Therefore, to study such a parallel mechanism, we analyzed stiffness in a parallel mechanism, including elastic deformation of both parts and bearings. Key points of our method are a modeling of bearings, a modeling of a elasticity coefficient of a passive axis in a bearing and a modeling of a parallel mechanism. Finally, we show that our stiffness analysis method of a parallel mechanism is high reliability and precision.

To tackle the singularity problem, the SC (singularity-consistent) approach was introduced. It achieves very stable control at and around a singularity with feasible joint velocities and no directional error in the end-effector velocity. This approach is very suited for a direct manual teleoperation system because of its errorless character for the direction. Until now, it was applied for the teleoperation of a nonredundant manipulator. In this paper, the SC approach for a 7-DOF manipulator will be addressed. To derive the whole properties of the SC approach, analytical studies for both the adjoint and the determinant of the Jacobian are necessary. However, it is very difficult to realize this goal, since the kinematics of a 7-DOF manipulator is quite complicated. Therefore, here, we establish a method to apply the SC approach to a 7-DOF manipulator numerically without analyzing the kinematic properties. This method, though, cannot realize the whole properties of the SC approach but a stable control at and around the singularities is achieved which is the most important and demanded property of the SC approach. Moreover, this method can also be applied for any type of articulated manipulator if its Jacobian can be defined. The results of our approach have been confirmed by experiments with graphics model.

In our previous works, we have proposed a mixed force and motion commands-based space robot teleoperation system and a compact 6-DOF haptic interface to achieve an effective manual teleoperation. Until now, the effectiveness of this system and the haptic interface has been confirmed by the experiments in our laboratory. The most important features of this teleoperation system are robustness against modeling errors and ability to realize the operator exerted force at a remote site. In this paper, elements of this system and the haptic interface have been employed to teleoperate the 6-DOF manipulator mounted on the Engineering Test Satellite VII (ETS-VII) which is a real space robotic system. Surface-tracking and peg-in-hole tasks with modeling errors have been executed in this experiment. The results show that our space robot teleoperation system including the haptic interface has been able to execute these tasks in real space environment without any big problems.

The development of a vision-only intelligent interface for dexterous robots is described, capable of tracking operator motions: evaluating trajectory feasibility, and providing visual feedback to the operator. This interface analyses the operator's arm motion for safety, and then converts it into trajectory commands for a mechanical arm. Potentially dangerous situations, such as singularity and self collision, are displayed to the operator as graphical icons superimposed over the robot video images. The paper summarizes the main features of the current implementation, presents the approach developed for singularity identification and describes the performance of the demonstration prototype.

In our previous work, several system elements for space teleoperation were introduced: a Singularity Consistent (SC) teleoperation system, a mixed force and motion commands based space teleoperation system, and a 6-DOF haptic interface (Y. Tsumaki and M. Uchiyama, 1997; Y. Tsumaki et al., 1998). We introduce an advanced space teleoperation system which includes all the above elements. As a result, the system realizes safety against the singularities and excessive force, with good perception for the operator. In addition, to verify the effectiveness of this system, we conducted experiments through the Internet between DLR in Germany and Tohoku University in Japan in January 1999.

We compare the main features of the singularity-consistent (SC) method and the damped-least-squares (DLS) method. It is shown that both methods introduce a so-called algorithmic error in the vicinity of a singular point. The direction of this error is, however, different in each method. This is shown to play an important role for system stability.

In this paper we propose a new compact 6-DOF haptic interface with large workspace. It contains a newly developed five bar spatial gimbal mechanism for orientation, placed on a modified Delta parallel-link mechanism. The motion range of each axis of the five bar mechanism is over /spl plusmn/70 degrees. Quick motions can be realized easily due to the parallelism inherent to both the modified Delta substructure and the five bar substructure.

In our previous work (1997, 1998) we proposed two approaches to singularity treatment: one is based on a null space notation, and the other on the adjoint Jacobian. We use the term "singularity-consistent (SC) approach" in referring to any of them. The SC approach guarantees the direction of motion in the whole work space. Thus, it becomes possible to move through singularities in teleoperated mode, without producing an infeasible joint velocity. However, a precise command direction is needed to accomplish such a specific motion. In this paper, we propose a supporting system for the operator to handle the above problem. An advanced SC teleoperation system is obtained, based on virtual reality techniques. Experimental results show that a real peg-in-hole task, including through-singularity motion, can be easily realized by the operator.

The singularity-consistent path-planning and motion control approach has so far been successfully tested within a teleoperation environment, but with separate control of the positioning subsystem and the wrist of the slave arm. In this paper, we show that the approach can be applied to a 6-DOF slave arm with a non-spherical wrist. The problems arising from the coupling between position and orientation are handled easily within the null-space/adjoint Jacobian framework of the singularity-consistent approach. The experiments show that the operator is able to approach the shoulder singularity smoothly, to move through it or to perform motions without leaving it.

Teleoperation with long time delay causes bilateral control to become unstable. A possible solution to the problem can be found with the help of virtual reality. Forces, reflected from the virtual world, do not depend upon the existing time delay in the system. Unfortunately, virtual reality based systems strongly depend on the accuracy of the model. In this paper we propose a teleoperation system which is robust to modeling errors, including geometric and dynamic ones. The reference force command is generated by using both force and position information simultaneously. The effectiveness of our approach is confirmed by experiments.

We analyze some aspects of human physical skill and propose a model thereof, with a view to implementing such skills in robots. We implement our model in a control scheme which makes use of impedance control in combination with low-gain force control and feedforward control. The summation results show that the model is able to achieve the reference force, and at the same time, the manipulator shows impedance-type behavior. Furthermore, with this scheme it is possible to track the reference force quickly, when the disturbance is known apriori. The experiments show that the performance of our control scheme is very close to that of the human operator.

Proposes a new technique for closed-loop kinematic control of nonredundant robotic mechanisms, based on the adjoint matrix of the kinematic Jacobian. Using the Lyapunov direct method, the authors show that the adjoint Jacobian approach guarantees asymptotic stability at regular points, around singularities, and at so-called instantaneous self-motion singularities. The new property, as compared to previous approaches, is that direction of motion can be precisely controlled at those points. To guarantee the asymptotic stability around any singularity and at instantaneous self-motion singularities, the desired (scalar) end-effector velocity is appropriately modified, and at the same time, restriction on the joint velocity norm according to a user-specified valve is imposed. In the vicinity of a singularity an error in the position along the desired path is tolerated, which however, does not lead to deviation from the path.

In this paper we discuss the relation between the two approaches to velocity command generation for nonredundant robotic mechanisms, which the two groups of the authors proposed recently and independently of each other. It will be shown analytically that the singularity-consistent null space based approach, and the split Jacobian approach, are equivalent. Analysis of the behavior at a singularity will be presented from the viewpoint of both approaches. An analytical example will be used to demonstrate the theoretical results.

We discuss the implementation and experimental verification of two new approaches to control of a nonredundant manipulator at and around singularities. One of the approaches is based on the adjoined matrix of the manipulator Jacobian, while the other one is a null-space based approach. The approaches share a common theoretical base described in our previous work. We focus mainly on several implementation issues and the experimental results obtained from our teleoperation system.

We develop further our singularity-consistent approach to arrive at a parameterized form of the dynamics of a nonredundant robotic mechanism tracking a desired path in Cartesian space. It is shown that this form is suitable for incorporating joint torque limits, which is an important issue for practical applications. We propose a closed-loop controller which behaves as a "conventional" resolved-acceleration type controller at regular points of the kinematic function. Around any singularity and at so-called instantaneous self-motion singularities the controller is able to truck the direction of the specified path exactly. The limit on the torque norm results in some position error, without deteriorating, however, the direction tracking ability. It is shown also that motion through the bifurcation type singularity can be easily controlled in practice as well.

It is well known that teleoperation with time delay causes force feedback control to become unstable. Therefore, bilateral control could not be used in such applications as space teleoperation with time delay. Force feedback information is, however, very important for the operator when performing contact tasks. Recently, virtual reality has been introduced to support force feedback based teleoperation with long time delay. The operator can feel the forces which are generated in the virtual world, even if there is long time delay. Unfortunately, virtual reality based teleoperation is prone to modeling errors between the real world and the virtual world. In this paper we propose such a teleoperation system which combines velocity-level commands with certain slave arm autonomy. The experimental results show that our system is robust with respect to tolerances in the geometrical model, and also, through the feedback loop from the virtual environment the operator can always feel a stable force.

Time delay reduced significantly the ability of teleoperation. This problem becomes especially serious in case of earth-to-space teleoperation, when the time delay is large. To overcome the problem, a predictive display technique has been proposed for non-contact tasks. However, the effectiveness of this technique has not been verified sufficiently. In this paper we propose a teleoperation system with time delay, based on the predictive display of a virtual beam, as well as on the concept of optimal approach velocity. The experimental results show that a peg-in-hole task, which includes a contact task, is realized very effectively by our method in spite of the long time delay. These results have been verified from various viewpoints such as task completion time, deviation of the task completion time, contact force, command, and integration of contact force and command.