Yoji Umetani

Resolved motion rate control of space manipulators with generalized Jacobian matrix

The authors establish a control method for space manipulators taking dynamical interaction between the manipulator arm and the base satellite into account. The kinematics of free-flying multibody systems is investigated by introducing the momentum conservation law into the formulation and a novel Jacobian matrix in generalized form for space robotic arms is derived. The authors develop a control method for space manipulators based on the resolved motion control concept. The proposed method is widely applicable in solving not only free-flying manipulation problems but also attitude-control problems. The validity of the method is demonstrated by computer simulations with a realistic model of a robot satellite. >

The development of soft gripper for the versatile robot hand

Abstract This paper deals with a new type of soft gripper which can softly and gently conform to objects of any shape and hold them with uniform pressure. This gripping function is realized by means of a mechanism consisting of multi-links and series of pulleys which can be simply actuated by a pair of wires. The possibilities of this gripper are demonstrated by a pair of mechanical model.

Human-robot contact in the safeguarding space

In this paper, we discuss a human-robot (H-R) coexistent system which allows H-R contact actions in the safeguarding space mechanically bounded by the human pain tolerance limit. The first half of this paper describes our study on the evaluation of the human pain tolerance limit which determines an individuals safeguarding space. We also show the human-safety-oriented design of a robot. The robot is covered with a viscoelastic material to achieve both impact force attenuation and contact sensitivity, keeping within the human pain tolerance limit. The robot, with simple direct-drive (DD) motor torque detection and emergency stop capabilities, automatically stops whenever any severe H-R contact occurs. In the second half of the paper, we propose a more efficient H-R system, which allows H-R contact for improving work efficiency, as long as the contact does not exceed the human pain tolerance limit. For this purpose, a robot is controlled to reduce its velocity with high reliability at an incipient stage of its contact with a human. Through experiments, we demonstrate the validity and efficient utility of the safeguarding space. The first experiment verifies that the developed robot exerts a contact force less than the human pain tolerance limit establishing the safeguarding space. The second experiment comparatively shows the robots velocity reduction to accept a safe contact with the human in the space.

Continuous path control of space manipulators mounted on OMV

Abstract Theoretical analysis on the formulation of kinematics for the manipulator mounted on a satellite is presented. Firstly, to solve the inverse kinematics, the authors define a new generalized Jacobian matrix, and utilizing this generalized matrix, the problem can be treated analytically. Secondly, the authors verify the method proposed here in the simulation study. Thirdly, they also discuss on the several points which are indispensable for further investigations.

Dual arm coordination in space free-flying robot

The control problem of multiple manipulators installed on a free-flying space robot is presented. Kinematics and dynamics are studied and the generalized Jacobian matrix is formulated for the motion control of a multiarm system. Individual and coordinated control of dual manipulators is discussed. For the coordinated operation, a new method of controlling two arms simultaneously-one arm traces a given path, while the other arm works both to keep the satellite attitude and to optimize the total operation torque of the system-is developed. By means of this control method, an interesting torque optimum behavior is observed and a practical target capture operation is exhibited by computer simulation.<<ETX>>

The standard circular gait of a quadruped walking vehicle

A quadruped walking vehicle has the potential capability of being developed into a vehicle of high mobility and adaptability to terrain by making use of its high degree of motion freedom. The authors have investigated the gait control problems of a walking vehicle, i.e. the straightforward or crab walk of the vehicle on rough terrains. This paper introduces a more generalized gait, namely, a circular gait around an arbitrarily located turn center, and discusses a standard circular gait. The standard circular gait is the one which maximizes the speed of walking and the rotational angle in a circular walk, and this consideration forms the basis of the discussion on advanced gait control problems. This paper formalizes the problems and analyses them by using mathematical optimization methods such as non-linear programming. Computations are carried out on a TITAN III, the quadruped walking vehicle model constructed by the authors. Several characteristics of the optimum gait and the final gait selection chart ...

Modeling of collision dynamics for space free-floating links with extended generalized inertia tensor

The authors present a basic formulation of motion dynamics of a free-floating rigid-link system to establish a basis of the collision dynamics. They propose a novel concept named extended generalized inertia tensor (Ex-GIT), which is an extended version of the GIT for ground-based arms, and discuss the virtual mass concept. By means of these concepts, they formulate the collision problem focusing on a velocity relationship just before and after the collision without sensing the impact force, but considering the momentum conservation law.<<ETX>>

Control of Space Manipulators with Generalized Jacobian Matrix

Space has been attracting special interest as a new application field of robotics. A robotic teleoperator system installed with space manipulators will play an important role in future space projects, such as constructing space structures or servicing satellites. However, in space environment, the lack of a fixed base arises serious problems in controlling space manipulators. Any motion of the manipulator arm will induce reaction forces and moments, and they disturb position and attitude of the satellite which is a footing base of the manipulator. To establish a control method for space manipulators with taking dynamical interaction between the manipulator arm and the base satellite into acconnt, the present authors investigate kinematics and dynamics of free-flying multibody systems by introducing a momentum conservation law into the formulation, and propose a new Jacobian matrix in a generalized form. By means of it, Resolved Motion Rate Control method, as well as Resolved Acceleration Control, is developed for space manipulation. The proposed method is widely applicable for not only free-flying operation but also attitude control problems. The validity and effectiveness of the method is exhibited by computer simulations and experimental study.

Development of shape-memory alloy actuators. Performance assessment and introduction of a new composing approach

A servo actuator using shape-memory alloy (SMA actuator), which performs special functions not found in conventional actuators, is expected to be a new driving source for future robots. This paper evaluates its performance and discusses the fundamental issues in designing such actuators. Being driven by the thermal martensitic transformation of the SMA itself, an SMA actuator is a driving system which can in principle, perform without any frictional parts, can be designed at a high output/weight ratio especially when a light-weight actuator is to be constructed But has low energy efficiency due to its mechanical characteristics of operating at a small temperature difference, and has a relatively low response. Our study shows some ways of overcoming these disadvantages by a special design approach. The method is called ξarray and is characterized by SMA wires being connected in parallel structurally and in series electrically. This approach enables the response to be enhanced due to the increased surface a...

Control of space free-flying robot

Both theoretical and experimental studies on the control of a free-flying robot manipulator for space application are presented. The goal of the studies is to develop a new control method for target capturing in a space micro-gravity environment, considering the dynamical interaction between the manipulator operation and the base vehicle motion. In the theoretical study, a generalized Jacobian matrix (GJM) concept of motion control and a guaranteed workspace (GWS) for path planning are investigated. In the experimental study, a laboratory model of a robot satellite supported on air bearings is developed; the model comprises a base satellite and a two-link manipulator arm. An on-line control scheme with vision feedback is developed for experimenting with capture operations, on the basis of the GJM and GWS. The manipulator can properly chase and capture both a standing target and a moving target in spite of the complex satellite/manipulator dynamical interaction.<<ETX>>