This paper discusses the design of a Redundant Drive Joint with Double Actuation (RDJ-DA) to produce controlled compliant motions over a higher bandwidth. First, our strategies on mechanical and controller designs to produce compliant motions are described, and the basic structure and impedance control of the RDJ-DA with internal serial structure explained. The standard form of the basic structure is introduced using a set of parameters which can be used to express the inertia property of RDJ-DA. Second, a problem statement for the design of RDJ-DAs is described after pointing out that required torques of the second actuator of the RDJ-DA could be large. Then, a basic idea of introducing springs into the second actuator in parallel is proposed as a part of the structural design of RDJ-DA to reduce the large torques. Simulations are conducted to find out a set of the design parameters of RDJ-DA which obtains a higher natural frequency of the output joint admittance satisfying both the desired output joint admittance and the limitations of two identical motors on their performance. Finally, a prototype design of RDJ-DA using the obtained set of the design parameters is presented.

This paper proposes impedance control of redundant drive joints with double actuation (RDJ-DA) to produce compliant motions with the future goal of higher bandwidth. First, to reduce joint inertia, a double-input-single-output mechanism with one internal degree of freedom (DOF) is presented as part of the basic structure of the RDJ-DA. Next, the basic structure of RDJ-DA is further explained and its dynamics and statics are derived. Then, the impedance control scheme of RDJ-DA to produce compliant motions is proposed and the validity of the proposed controller is investigated using numerical examples.

Force redundant mechanism is adopted to achieve high acceleration. However, utilizing the good velocity control performance of servo motor to achieve a high positional accuracy will arise excessive big internal forces. Therefore, an idea of introducing kinematical redundancy into force redundant parallel mechanism is proposed. In this idea, we do not add kinematical redundancy on the sub arm but introduce internal redundant motion into the top plate. The concept of this research is illustrated by improving a simple force redundant parallel example, and the merits of the improved mechanism are summarized. This theory is applied into modifying the real high speed parallel mechanism NINJA. Its kinematics and static force relationship are derived and compared respectively. The prototype of the new mechanism is proposed.

A systematic approach to compute total stiffness of parallel manipulators is proposed. Link stiffness and joint stiffness can be calculated simultaneously. Stiffness of passive joint (joint without actuator) is temporally assumed as nonzero variable in the procedure and infinite stiffness can be treated. A simple parallel manipulator is used as an example to illustrate the process and its correctness. Then validity of the proposed approach is confirmed by comparing to FEA and conventional joint stiffness method. The total link compliance (inverses of total stiffness) calculated by the developed approach and its counterpart obtained by FEA model are very close. The total joint stiffness computed by the developed approach and its correspondence derived from conventional joint stiffness method are totally the same. Stiffness performance of parallel force redundancy mechanisms is evaluated. These results indicate that this scheme is feasible and effective.

We discuss an analytical method to judge whether an exoskeletal robotic orthosis has the possibility of producing assisting forces while guaranteeing the user's safety. First, an explanation of this judgment is given. Second, a theoretical method to simultaneously evaluate the mechanical safety for the user and the possibility of assistance is proposed based on the force analysis. Then, an application of the proposed method to the mechanical design of the exoskeletal robotic orthosis is described.

This paper describes the process of developing the parallel mechanism "NINJA ", which is designed to achieve an acceleration rate over 100 [G] (G: gravitational acceleration). To design this mechanism, we introduce a two-step design method (an optimum design method). The technical part of this method consists of formulating the design problem of two steps: Step 1, where we assume and select the design parameters, which should satisfy the required specifications, and Step 2, where we optimize the parameters under the constraint conditions based on the required specifications. To demonstrate the acceleration performance, we present experimental results using the prototype NINJA.

A power-assisting device is being developed to help older persons and people with disabilities move themselves from beds to wheelchairs. The device is intended to contribute to a more independent life for these people and to greater utilization of their latent abilities. Self-support assistance, i.e., the support provided by a power-assisting device to the person without the need for aid from a caregiver, and capability of the device to assist the movements of the people are discussed. A method for the production of power assistance and motion guidance is then proposed for the device. Finally, a test of the performance of the developed system is described.

A power-assisting device is presented to help elderly patients and patients with disabilities transfer themselves from beds to wheelchairs. The device is intended to contribute to a more independent life for the patients and to greater utilization of their disabilities. The development of the device, which consists of an upper part capable of motion in a horizontal plane and a lower part capable of motion in a vertical plane, is discussed. The production method for the power assistance and motion guidance of this device is proposed. Finally, the testing of the performance of the developed system in a basic experiment is described.

The Japanese Government plans to hold the International Robot Games Festival in 2001, which is called "RoboFesta 2001". The RoboFesta 2001 will be held both in the Osaka area and Kanagawa Prefecture in Japan, and will consist of several authoritative robot games, an international forum, and lots of robot-related exhibitions during the summer and autumn in 2001. The article describes the aims and organisation of the festival, then describes the various games.

We developed a robotic orthosis capable of helping human forearm motion. This orthosis was carefully designed such that mechanical safety for human beings could be ensured. A power assist control scheme for the robotic orthosis is proposed. The performance of the developed system is examined by several experiments.

Discusses development of a multifingered hand-wrist mechanism for compliant motion. First, a procedure for the mechanical design is proposed, and details of the procedure are shown using a simple two-fingered hand. Second, a three-fingered hand with wrist is designed based on the proposed design procedure, and a force sensor is also designed. Then a three-fingered hand-wrist mechanism with fifteen DOF is manufactured. Finally, basic experimental results are described to investigate part of the performance of the developed mechanism and the force sensor.

Development of a redundant macro-micro manipulator for compliant motion and its application to contour tasks are discussed. Redundant macro-micro manipulators under an appropriate control scheme could have numerous advantages: suitability to compliant motion using micro manipulators and a big motion range as a result of macro manipulators. However, we have to design these mechanisms carefully so as to get the desired merits of this system, because the performance of the control scheme is affected by the properties of this mechanism. In this report, development of a micro manipulator is presented for a given macro manipulator. The experimental results show that compliant motion of the developed mechanism is useful in contour tasks.

A control scheme for grasping and manipulation by arm-hand mechanisms is proposed. The arm-hand mechanisms, consisting of arm and multifingered hand have the same feature as that of redundant macro-micro manipulators concerning manipulation. That is: (1) manipulations are possible by both the arms and hands, (2) the hands are suitable for the compliant motions compared to the arms because of their small inertia, and the motion ranges of the arms are bigger than those of the hands. The control scheme can utilize both merits of the arms and hands. Simultaneously, it can realize the secure grasping during manipulations. Several simulation and experimental results illustrate the validity of the proposed control scheme.

This paper proposes a cooperative control scheme of dual-arm robots, which produces a reasonable pair of the two endpoint motions of the arms for a given relative motion. A dual-arm system with a linear motion is discussed, and the principle of the control scheme is presented. The redundancy of the system and the problem of the motion distribution are explained. The concept of the absolute motion which represents the total motion of the system is introduced, and a cooperative control scheme of dual-arm robots is proposed, using this absolute motion. Basic equations are presented and a cooperative control scheme of dual-arm robots with six degrees of freedom is proposed. Finally, several simulation and experimental results are given to illustrate the validity of the proposed control scheme.

An impedance control scheme of redundant macro-micro manipulators is proposed. In this control scheme, we can specify not only the desired mechanical impedance of the end effector, but also that of the macro manipulator by considering the internal force applied at the tip of the macro manipulator. This control scheme can utilize both of the merits of the macro and micro manipulators. That is, by specifying a suitable set of the desired mechanical impedance, a compliant motion can be realized without any excessive joint torque of the macro manipulator, and a wide motion range of the macro manipulator can be used effectively to compensate a small motion range of the micro manipulator. The validity of the proposed control scheme is shown by several simulation results.>

When a mechanism is overconstrained it leads to the generation of internal forces. These forces do no work but have an effect on the apparent structural stiffness of the mechanisms. The degree of this effect depends on the magnitude or the mode of the internal forces and the geometry of the mechanisms. Internal forces may result from external or gravitational forces or the inertial loads during motion. If a mechanism has a closed chain structure, the redundant actuation may generate internal forces as well. -. . 'o The authors analyse the apparent structural stiffness of the closed mechanisms due to redundant actuation and the forces arising during dynamic motion.>

A new definition of grasping and manipulating forces for multifingered robot hands is proposed. First, a short discussion of the grasping and manipulating forces for two-fingered hands with linear motion is given to explain the motivation more clearly and to give the basic idea of the new definition. Then, for three-fingered hands, based on a representation of the internal force, the grasping force is defined as an internal force that satisfies the static friction constraint. The concept of grasp mode is also introduced. The manipulating force is then defined as a fingertip force that satisfies the following three conditions: (1) it produces the specified resultant force, (2) it is not in the inverse direction of the grasping force, (3) and it is orthogonal to the grasping force component. An algorithm for decomposing a given fingertip force into manipulating and grasping forces is presented. Extensions of the result to cases of two-fingered hands with planar motion and four-fingered hands are discussed. Finally, a simple example of synthesizing fingertip force for a given manipulation task is given to illustrate the usefulness of the proposed definition.>

Evaluation of grasping and determination of grasping forces in manipulation by multifingered hands are discussed. Based on the definitions of manipulating and grasping forces introduced previously, the advantages of determining a grasping force beforehand for the secure grasping against an anticipated class of external forces is described. For evaluation of a given grasping force, a criterion of the remaining ability of grasping is proposed. A method of grasping for a given manipulation tasks, in which grasping forces are determined as those with the maximum value of this criterion, for the expected external forces in each step of the task, is proposed.>

This paper discusses the mechanics of coordinative manipulation by multiple robot manipulators or a multifingered robot hand. The coordinative manipulation problem is divided into two phases. One is determining the resultant force by multiple robotic mechanisms, and the other is determining the internal force between them. The resultant force is used for the manipulation of an object subjected by the external forces or the environmental constraints. The internal force is used for adapting the robotic mechanisms to uncertainty and variety of the static friction. A dynamic coordinative control scheme is proposed for determining the resultant forces. The optimal internal force is defined as the internal force that yields the minimal norm force satisfying static frictional constraints. The optimal internal force promotes the stability of prehension, while the conventional method sometimes result in too much internal force and reduce the stability. Finally, by applying a non-linear programming method, it is clarified that the optimal solution is necessarily obtained by solving, at most, 2(2m-1) (m is the number of robotic mechanisms) sets of algebraic equations if it exists.

Manipulating force and grasping force for skillful manipulation of objects by multifingered robot hands are discussed in this paper. A new representation of the internal force among the fingers is given. Based on this representation, the grasping force is defined as an internal force which satisfies the static friction constraint. The mode of grasping is also introduced. The manipulating force is then defined as a fingertip force which satisfies the following three conditions: 1) It produces the specified resultant force. 2) It is not in the inverse direction of the grasping force. 3) It does not contain any grasping force component. An algorithm for decomposing a given fingertip force into manipulating and grasping forces is presented.