The study deals with an above-knee prosthesis that allows amputees stairs ascending/descending with no external energy sources. Our previous study certified that the employed hydraulic system propelled by the antagonistic actions of knee and ankle joints enables stairs ascending/descending as well as level walking. The paper deals with the subsequent developments to get amputee's walking gait close to normal ones. We combined flow control valve (FCV) into the hydraulic system that is automatically driven during walking. The walking experiments certified that the FCV provides the double knee action that normally appears in healthier persons' walking gait, and it also provides a smooth transition from level ground walking to stairs ascending. However, it was found some instability in the stairs descending.

In our research, we have developed a Gripper with Multi Joint Fingers (MJF) that achieves envelope grasping adapting to shape of objects. In this paper, we discuss grasping motion using two or three MJFs. The MJF has 4 serially connected joints controlled by only two actuators, one for driving all joints at the same time for envelope grasping, the other for controlling the stiffness of every joint all together. This MJG achieves envelope grasping adapting various object shapes without sensory feedback from finger parts. The paper also reports an extended mechanism that enables a smooth transition from a state of pinching object with fingertips to a stable envelope grasping. It also shows the gripper can detect a multiple contact points during envelope grasping with no touch or force sensors on the finger sole.

The paper deals with 5 finger hand based on the original finger mechanism consisting of a planetary gear system and serially connected four bar linkages. It takes an all-in-one design: all of the actuators (total five DC motors) are embedded into a palm, while finger parts do not have any electronic devices for attaining to be inherently safe as an end-effector. The mechanism allows us adaptive synergic motions of three joints of a finger (MP, PIP and DIP) according to configuration of gripping objects. The hand also has a mechanism for adjusting stiffness of fingers, which allows to give passive gripping force to a gripping object according to the object's elasticity. Driving tests show that it achieves typical gripping and pinching motions of a human hand in daily life without any sensory feedback and also show that the stiffness adjuster works effectively.

This paper proposes a multi-joint-gripper that achieves envelope grasping for unknown shape objects. Proposed mechanism is based on a chain of Differential Gear Systems (DGS) controlled by only one motor. It also has a Variable Stiffness Mechanism (VSM) that controls joint stiffness to relieve interfering effects suffered from grasping environment and achieve a dexterous grasping. The experiments elucidate that the developed gripper achieves envelop grasping; the posture of the gripper automatically fits the shape of the object with no sensory feedback. And they also show that the VSM effectively works to relieve external interfering. This paper shows the mechanism and experimental results of the second test machine that was developed inheriting the idea of DGS used in the first test machine but has a completely altered VSM.

This paper proposes a multi-joint-gripper that achieves envelope grasping for unknown shape objects. Proposed mechanism is based on a chain of Gear Systems controlled by only one motor. It also has a Variable Stiffness Mechanism (VSM) that controls joint stiffness to relieve interfering effects suffered from grasping environment and achieve a dexterous grasping. The experiments elucidate that the developed gripper achieves envelop grasping; the posture of the gripper automatically fits the shape of the object with no sensory feedback. And they also show that the VSM effectively works to relieve external interfering. This paper shows the detail of the mechanism and the experiments of its motion.

This paper presents a mechanical system that fundamentally mimics a human musculo-skeletal system aiming for using it in anthropomorphic robots or artificial limbs for disabled persons. At first, it introduces a mechanical module called ANLES (Actuator with Non-Linear Elasticity System). It can be used as a voluntary muscle since it is a linear actuator with non-linear elasticity similar to a voluntary muscle. It follows an application of the ANLES into a three DOF artificial joint arranged to use as a wrist joint of an anthropomorphic robot. At first it shows the first model controlled by four ANLESes and one extra-motor, which was under-actuated to control three joint angles and three joint stiffness. Next it shows the second model that is controlled by six ANLESes to control the angle and the stiffness of the concentrated three rotary axes.

This paper investigates the posture of the manipulator that has redundant DOF similar to human upper extremity. The human arm naturally takes a posture with no wandering although it has one or two DOF redundancy. The authors consider that the posture will be determined in task-oriented, which means that human unconsciously takes a posture of his/her upper extremities, which is suitable for the task that the endpoint is about to do. This study also assumes that all joints are capable to adjust the joint stiffness so that the stiffness of the endpoint in the task space is also adjustable. Hence our study aims to establish the theoretical method to make the manipulator take a posture that provides a stiffness of the endpoint suitable for the task. The new formula for shaping the manipulator's posture to provide a desired stiffness of the endpoint is presented followed by the simulation study to verify it.

This paper deals with mechanical stiffness control of multi-DOF joint. It fundamentally mimics the skeleto-muscular system of human articulation, in which at least two muscles handle one rotary axis under their antagonistic (counteractive) action. In the first part of the paper one introduces basic formula for controlling the multi-DOF rotary joint that is assumed to be driven by a couple of novel actuators called ANLES (actuator with non-linear elastic system). It mimics a skeletal muscle in the sense of having a non-linear elasticity. Next the paper describes the structure of the ANLES that is designed and constructed for controlling the wrist joint of an anthropomorphic robot. The experimental results using three DOF joint controlled by four ANLES reveal that the joint angle and the joint stiffness can be independently controlled by the proposed formula.

This paper presents a new mechanism for artificial fingers. It enables adduction/abduction of the MP joint in addition to the synergetic flexion/extension of the DIP, PIP and MP joints. The key mechanism is the newly invented double planetary gear system (DPGS) that allows three DOF motions of the finger in a compact placement of all actuators in a palm. The DPGS receives three input torques; two are active torques coming from DC-motors, which drives solar gears, the other one is a passive torque loaded at the carrier of the planetary gears generated by a spring. This active / passive hybrid actuation enables to grip unknown shape objects with no sensory feedback. This paper describes the kinematics and the kinetics of the newly developed mechanism followed by the kinetics of pinching the object by two-fingers. It also shows the results of a couple of experiments. Additionally, we show a new mechanical design aiming for constructing a multi-fingered hand.

This paper investigates the posture of a manipulator that has redundant DOF similar to human upper extremity. The human arm naturally takes a posture with no wandering although it has some redundant DOF. The authors consider that the posture will be determined task-oriented, which means that human unconsciously takes posture of his/her upper extremities, which is suitable for the task that the endpoint about to do. This study also assumes that all or some joints are capable to adjust the joint stiffness so that the stiffness of the endpoint in the task space is also adjustable. Hence our study aims to establish the way to make the manipulator take a posture that provides a stiffness of the endpoint suitable for the task. The new control formula for shaping the manipulator's posture to provide a desired stiffness of the endpoint is presented followed by the simulation study to verify it.

This paper introduces an extension to the original error-based minimal control synthesis with integral action (Er-MCSI) algorithm, for controlling serial link manipulators. Minimal control synthesis (MCS) methods have a number of attractive features: no a priori knowledge of the robot structure is required; e.g., no need for parameter identification, no precise adjustment of control parameters is necessary and proven stability. After a brief summary of the basic MCS algorithm, we introduce the new algorithm, which provides a more robust environment in terms of gain wind-up protection. A proof of stability is also provided, together with simulation studies upon serial link manipulators, which demonstrate the excellent performance of the proposed algorithm, even under severe test conditions.

This paper deals with mechanical stiffness control of multi-DOF joint. It fundamentally mimics the skeleto-muscular system of human articulation, in which at least two muscles cooperatively handle one DOF under their antagonistic action. In the first part of the paper one describes a novel actuator called ANLES (actuator with non-linear elastic system) that mimics a skeletal muscle in the sense of having a non-linear elasticity. Next one introduces a basic formula for controlling stiffness of the joint as well as its angles using multiple ANLESes. A new mechanism for the wrist joint having three DOF is proposed on the practical feasibility base, in which only four ANLESes with one additional DC-motor are used to control the stiffness of the three DOF wrist. It follows the simulation analysis for evaluating the controllability of the stiffness. It also shows the one DOF wrist joint controlled by two ANLESes

This paper deals with mechanical stiffness control of multi-DOF joint. It fundamentally mimics skeleton-muscular system of human articulation, in which at least two muscles cooperatively handle one DOF under their antagonistic action. In the first part of the paper one describes a novel actuator called ANLES (actuator with non-linear elastic system) that mimics a skeletal muscle in the sense of having a non-linear elasticity. Next one introduces a basic formula for controlling stiffness of the joint as well as its angles using multiple ANLESes. It follows the evaluation of the proposed formula by the simulation analysis. Three DOF joint manipulated by six or eight tendons that are individually controlled by the ANLES is evaluated with respect to the stiffness control.

This paper presents a method for control stiffness of the end-point of manipulator that has redundant DOFs. It is assumed that all of the joints of the manipulator are capable of regulating their joint stiffness mechanically, not by the software feedback using force/torque information. The particular mechanism for regulating the joint stiffness, called the NonLinear Elastic Module (NLEM) is introduced on the antagonistically driven joint system. A new formula for controlling the stiffness ellipsoid of the end-point is derived Although the shape of the stiffness ellipsoid is essentially determined by the configuration of the joints and the posture of the manipulator, the computer simulation demonstrates the volume and the shape of the stiffness ellipsoid can be substantially regulated by using the proposed formula. Next, the optimal posture of the redundant manipulator suited for an associated task is investigated from the viewpoint of the stiffness ellipsoid An anthropomorphic type seven DOF manipulator is taken as a simulation model.

This paper introduces a biped robot named TOKAI ROBO-HABILIS 1. It has some particular mechanisms in the joints, by which it moves with the combination of active driving by the DC motors and passive rotation of the joints, called active/passive hybrid walking. It is essentially the identical way of walking to those of human. As a result, it walks with a subsequently small energy consumption compared to any conventional biped walking robots that walk with driving all of joints actively by actuators. This paper describes at first the mechanisms of TOKAI ROBO-HABILIS 1. Its computer simulation shows the control strategy and the energy consumption for various walking patterns. It follows to show the walking experiments.

We present a method for mechanical stiffness control of the tendon-driven joints of a manipulator. First we propose a formula for controlling the joint stiffness and the joint angles independently. Next, we propose an elastic mechanism (nonlinear elastic module, NLEM) of which nonlinear elastic characteristics are easily designed. It is situated between the actuator and the tendon and it plays a key role for mechanically controlling the stiffness. Two types of the NLEM are designed and produced. A computer simulation of and experiments on the stiffness and joint displacement control, which show validity of the proposed formula are described.