We discuss grasp stability under gravity where each finger makes soft-finger contact with an object. By clustering polygon models of a finger and an object, the contact area between a finger and an object is obtained as the common area between an object cluster and a finger cluster. Then, by assuming the Winkler elastic foundation, the pressure distribution within the contact area is obtained. By using this pressure distribution, we show that we can judge grasp stability under soft-finger contact. We further consider defining a quality measure of a soft-finger grasp by assuming that although the gravitational force is applied to an object, the direction of gravity is unknown. To demonstrate the effectiveness of the proposed approach, we show several numerical examples.

To make structured environment aims at establishing the information structured environment which enables robots to get information and knowledge necessary to carry out the given tasks from the environment. In this paper, we build the information structured environment named the u-RT space, and then design and control the librarian robot system based on the proposed environment, which can put books on the proper slot in the bookshelf using the ambient intelligence and the book information. First, we introduce the information structured space where the physical space and the virtual space are connected each other, and propose the robot localization method and the bookshelf information system based on the ambient intelligence realized by the RFID technology. Next, we introduce the librarian robot system which consists of the manipulator which can recognize and manipulate books, and the mobile platform which can localize itself and navigate using the ambient RFID tags implanted under the floor even if there are high bookshelves. Then we propose the classification and integration method of the information from various ambient sensors which enables the proposed robot to complete given missions successfully. Finally, the performance of the proposed librarian robot system is evaluated by the experiment based on an example scenario in the u-RT space.

This paper proposes an analytical methodology of inverse kinematic computation for 7 DOF redundant manipulators with joint limits. Specifically, the paper focuses on how to obtain all feasible inverse kinematic solutions in the global configuration space where joint movable ranges are limited. First, a closed-form inverse kinematic solution is derived based on a parameterization method. Second, how the joint limits affect the feasibility of the inverse solution is investigated to develop an analytical method for computing feasible solutions under the joint limits. Third, how to apply the method to the redundancy resolution problem is discussed and analytical methods to avoid joint limits are developed in the position domain. Lastly, the validity of the methods is verified by kinematic simulations.

This paper proposes a practical redundancy resolution for 7 DOF redundant manipulators with joint limits. The primary concern of the paper is how to resolve the redundancy in the global configuration space when the movable joint angles are considerably restricted. First, a parameterized inverse kinematic solution for a 7 DOF manipulator model is derived. Second, how the joint limits affect the inverse kinematic solution is examined to explicitly identify the feasible solution under the joint limits. Then, an analytical redundancy resolution method for avoiding the joint limits is developed. Finally, kinematic simulations show that the method is effective for avoiding the joint limits as well as expanding the reachable region of the manipulator's tip.

In this paper, we propose a task skill transfer method using a bilateral teleoperation. We assume that a task skill for a complicated motion is described by the suitable trajectory of the impedance center. Thus, a important point is how to get the suitable trajectory of the impedance center. In our method, the suitable trajectory is got from results of bilateral teleoperation. In the bilateral teleoperation, an operator constructs a motion procedure able to execute the task. The suitable trajectory of the impedance center is calculated from the position and the force data in the teleoperation experiment. A basic element of the task skill is composed of an initial condition, a task skill motion and a final condition. The initial and final conditions are described by values of both sensor and tip position. The task skill motion is described by a hybrid impedance/force control. To demonstrate how to use of our method, we choose the nut attachment task as an example

In this paper, we propose RT-middleware for robot system integration. "RT" means "robot technology", which is applied not only to industrial field but also to nonindustrial field such as human daily life support systems. RT-middleware which is proposed in this paper is a software platform for RT systems. We have studied modularization of RT elements and have developed RT-middleware, which promotes application of RT in various fields. Robotic system development methodology and our RT-middleware concepts are discussed. The RT-component, which is a basic software unit of RT-middleware based system integration, is derived from this discussion. A methodology of system development by using RT-components, and a framework for component development are proposed. Evaluations of some RT-component based systems are performed. Finally, conclusions and future work is described.

"Teaching by demonstration" is a method to generate a robot program that makes a robot do the same task as the task that a human operator demonstrates. We have developed a "teaching by demonstration in VR" system (TbDinVR) which automatically generates a robot program to work in the real world after a task is demonstrated by an operator in the virtual world. In this paper, we have explained necessary and sufficient condition for states in a task description, advantages of using state-based TbDinVR system, and a simulator for determining parameters of skill primitives by using sensor simulation in VR and a random search technique in detail. We have shown an experimental result and visualization of that result.

"Teaching by Demonstration" is a method of generating a robot program that makes a robot do the same task as the task that a human operator demonstrates. We have developed a "teaching by demonstration in VR" system that automatically generates a robot program to work in the red world after a task is demonstrated by an operator in the virtual world. This system generates a program that detects each contact state extracted from demonstration in VR and produces it by skillful motion primitives. We find that some types of motion that are included in the recorded motion given by a human operator in the VR in teaching stage cannot be realized in the execution stage if the robot tries to do the same task by using the human demonstration data even on a contact state level. In this paper, based an our observation that a human has the skill wherein contact state transitions are made non-deterministically, we propose a method of dealing with one of the important non-deterministic motions, "non-deterministic search type motion" Experimental results show the feasibility of the method.

Manipulator tasks such as assembly and disassembly can generally be divided into several motion primitives. We call these "skills" and explain how most manipulator tasks can be composed of skill sequences. Skills are also used to compensate for errors both in the geometric model and in manipulator motions. There are dispensable data in the shapes, positions and orientations of objects when achieving skill motions in a task Therefore, we can derive simplified geometric models by considering both dispensable and indispensable data in a skill motion. We call such robust and simplified models "false models." This paper describes our definition of false models in planning and visual sensing and shows the effectiveness of our method using examples.

This paper investigates the handling of a fabric - a limp material with softness and flexibility. The fabric is characterized not only by its malleability but also its nonlinear properties. These properties are considered for picking up a piece of fabric. The robot hand with 3 fingers and a palm, that is used to study various handling techniques, is introduced. Its performance when picking up a piece from layers is experimentally shown.

Describes a unified method for integrating different kinds of sensor-based control. We introduced "control space", which is smoothly related to actuator space. Each sensor-based control law is described in the control space. The integration is done automatically by mapping the control space to the actuator space based on local linear relations between them. We also proposed the multi-agent-based implementation of the control system. Simulation and experiment show the effectiveness of this new method.

Contact state information is indispensable for performing skillful tasks in which an end-effector should be in contact with the environment. In previous work, the authors introduced the concept of a pseudo contact point that is useful for tasks involving contact as one expression of the contact state. In this paper, an extended definition of the pseudo contact point is proposed. The pseudo contact point is defined as the foot of the perpendicular from the nearest point on a reference object to the line on which the contact point and external force vector lie. The system may estimate the contact state and its transitions by monitoring the pseudo contact point in spite of the fact that the pseudo contact point does not always denote the real contact point. Experimental results suggest the effectiveness of our method, which is particularly valuable in providing an intuitive positional description of a contact state.

The paper describes an integrated teleoperation system for maintenance tasks with planning functions based on manipulation skills. We embed planning functions into a telerobotics system to make the system more flexible and robust. A motion teaching system based on contact state transition, a geometric modeling system using teaching trees, and a task execution system based on manipulation skills are integrated. The design concept of the system and essential technologies are described. An experimental task is explained to demonstrate the efficiency of the telerobotics system.

Insertion of a flexible wire into a hole is a difficult task because the wire has a tendency to buckle under external forces. Moreover, the plastic deformation occurs on a flexible wire when the force acting on the wire is big. In this paper, we propose a method of inserting a flexible wire whereby a force acts on the wire and the shape of the wire is observed by stereo vision. A strategy to transform the deformed wire to the straight one and to insert the wire into a hole is presented. Finally, some experimental results are shown.

Measuring the force on a flexible wire is difficult by using force/torque sensors when the flexural rigidity of the wire is small because the wire buckles and the force on the wire is smaller than the force that can be measured by a force/torque sensor. This paper presents a method of calculating the force on a wire from its shape observed by stereo vision. We propose a method of inserting the wire into a hole in a wall by using the estimated force. Three experiments have been successfully carried out.

This paper proposes a multi-agent based implementation of robot skills. As an example, a skill motion for assembly tasks, "move-to-touch", has been implemented on a multi-agent robot control system developed on a transputer network. The skill motion is constructed as an integration of several agents, a motion control agent, event detection agents and a management agent. Our implementation has achieved high flexibility, reliability and extensibility of the skill control system.

Monitoring of a contact state is an important technique to achieve tasks in which an end-effector should be in contact with an object. This paper introduces a pseudo contact point that is useful for precise tasks including contact processes. When the position of a point contact between the end-effector and the object moves to another position, the pseudo contact point denotes the present contact point. The pseudo contact point is defined as the foot of the perpendicular from the previous contact point to the line on which the external force vector lies. Experimental results suggest the applicability of our method.

This paper presents a general approach of model-based adaptive hybrid control for holonomically constrained manipulators. Both time-invariant and time-variant constraints are dealt with. This controller works on the basis of an orthogonalization principle of trajectory and force errors in the joint space and intrinsic characters of the manipulator dynamics. Its asymptotic stability is guaranteed by a passivity-based Lyapunov function. A distributed cooperation controller based on the same concept for multiple manipulators is also presented. Further, we show a parallel implementation of this controller using transputers on a six DOF direct drive manipulator, and some experimental results.

Discusses the task of inserting a flexible beam into a hole when the friction force is large enough to buckle the beam. The authors analyze the buckle shape of the beam and external forces and moments loaded on the beam during the insertion task, under the condition that the potential energy of the beam is minimized. Then, the authors find that the buckling shape has two buckling modes and the modes are changed by varying the orientation angle of the end of the beam. The authors propose a method of performing the insertion task, based on an analysis of the relation between the external forces and friction coefficient. Finally, the authors present experimental results which confirm their analysis.

This paper presents a general approach for adaptively and distributively controlling multiple cooperative manipulators. The proposed approach does not adopt a centralized architecture but assigns a controller to each robot. Any communication requirement is determined by motion constraints existing in the cooperative system. All physical parameters of the manipulators or the load of the system are online estimated by a model-based adaptive algorithm. A Lyapunov function guarantees asymptotic convergence of trading errors of the trajectory and the interactive force among the robots. Performance of this controller is further shown by simulations on six DOF manipulators.

We have been developing a multi-agent robot control system for an intelligent robot which is an integration of many kinds of functional modules. The control system consists of multiple transputers and workstations. To support flexible and high speed communication between agents on the network, we have developed a router software. Using the router, the system realizes a very flexible robot control system which supports throughout of robot control, from the low level control such as servo control to the high level control such as motion planning. This paper describes the multi-agent robot control system with the router software, estimation of its communication performance and a multi-agent based implementation of task coordinate servo control of a direct drive manipulator: ETA3.

A method of generating an optimal approach velocity, to control the collision forces properly, of a manipulator to its environment is presented. Analysis of a contact motion shows the necessity of contact control not only after the collision, but also before it. Using a model of the force-controlled end-effector and its environment, forces generated at the contact are formulated as outputs of an autonomous system of which the initial condition is determined by the approach velocity. The optimal approach velocity is defined as the velocity that minimizes a performance index. A proportional relation between the optimal approach velocity and the contact force reference is derived analytically based on a mass-damper-spring model of the force-controlled end-effector and its environment. Results of the simulation and the experiment are presented to demonstrate the effectiveness of the method.>