Showzow Tsujio

Trajectory control of flexible manipulators on a free-flying space robot

A space robot consisting of a satellite main body that flies freely and manipulators that have structural flexibility is considered. The position and orientation of the satellite main body may change when the manipulators move. Motions of the space robots also induce vibrating motions of the structurally flexible manipulators. The control schemes used are the virtual rigid manipulator, pseudo-resolved acceleration control, and composite control. A singular perturbation strategy is applied, and the stability of the controls is examined. Numerical examples are given.<<ETX>>

Torque sensing of finger joint using strain-deformation expansion mechanism

/sup F/or dexterously performing object grasping and manipulation with multifingered hand of robot, sensing the finger joint torque is required. In general, the size of finger joint is quite small so that it is hard to realize the torque sensing. This paper proposes a novel mechanism, called the strain-deformation expansion mechanism, to sense the joint torque, which is small enough and fitted in the finger joint. By the torque sensing mechanism, the small joint strain-deformation used for torque sensing can be expanded without reducing the joint stiffness. In this paper, the torque sensing principle is addressed by analyzing the deformation of the sensing mechanism and the torques acting on the joint shaft theoretically. Then, the sensitivity of the sensing mechanism and its expansion rate of sensitivity are defined, and a design method for realizing the sensing mechanism with high sensitivity is discussed. Finally, some experiments with robot finger are performed to show the basic characteristics and the effectiveness of the proposed torque sensing mechanism.

High-performance jumping movements by pendulum-type jumping machines

On vertical jumping movements of humans, swings of arms and counter movements of legs are essential. In this paper, the swings of arms are focused, and two pendulum-type jumping machines are presented. The aim of our research is to show that the presented mechanism, to which the swings of arms am applied, is effective to perform jumping movements. These pendulum-type jumping machines demonstrate abilities of jumping up, soft landing, and going up and down stairs. Consequently, it is concluded that the swings of arms will contribute toward high-performance jumping movements.

Estimation of mass and center of mass of graspless and shape-unknown object

In many cases of manipulating an object stably and accurately by robot, it is required to know the mass and center of mass of the object. For the case when the weight or shape of an object is over the grasp capacity of a robot hand, the paper proposes a technique that can estimate the mass and center of mass of the graspless and shape-unknown object. A plane called gravity equi-effect plane is first defined, which contains the center of mass and a contact line where the object is in line-contact with an environment. If three or over three orientation-different gravity equi-effect planes of an object are obtained, the center of mass of the object can be estimated by the intersect point of the planes. In order to estimate the gravity equi-effect plane, tip operation by robot finger, which tips the object repeatedly, is proposed. Then an algorithm to estimate the gravity equi-effect plane and an algorithm to estimate the mass and center of mass of the object are addressed by using the fingertip position and force information measured from tip operations.

An analytical grasp planning on given object with multifingered hand

In this paper, an analytical approach is proposed for planning finger positions of grasping an object with a multifingered hand. First, a method is given to obtain which combination of the object edges is possible to be used for grasping. Then, a graspable finger position region (GFPR) on a combination of edges is defined where the object can be held successfully. It is shown that the region is bounded by several boundary hyperplanes. By combining these boundary hyperplanes, two propositions for analytically and exactly obtaining the GFPR are proposed. An algorithm is proposed to find a stable GFPR that contains the biggest inscribed hypersphere of GFPR and has the largest volume. Finally, a numerical example is performed to show the effectiveness of the proposed grasp planning approach.

HIGH-STIFFNESS AND HIGH-SENSITIVITY 3-AXIS FORCE SENSOR USING STRAIN-DEFORMATION EXPANSION MECHANISM

For dexterously performing object grasping and manipulation with multifingered hand of robot, sensing the fingertip forces with high-stiffness and high-sensitivity is desired. In general, from previous sensing structures, if the stiffness of a sensor is made be higher, its sensitivity is reduced. This paper proposes a novel mechanism called strain-deformation expansion mechanism for 3-axis force sensing. By the force sensing mechanism, the small strain-deformation used for force sensing can be expanded while the sensor stiffness is not reduced but is heightened. In this paper, the force sensing principle is addressed by analyzing the deformation of the sensing mechanism and the forces acting on the sensor theoretically. Then, the sensitivity of the sensing mechanism and its expansion rate of sensitivity are defined, and a design method for realizing the sensing mechanism with high sensitivity is discussed. Lastly, some experiments are performed to show the basic characteristics and the effectiveness of the sensing mechanism

Estimation of object inertia parameters on robot pushing operation

This paper proposes a technique that can estimate the inertia parameters of a graspless unknown object, which is pushed by robot fingers. Using the fingertip different accelerations (or angular accelerations), velocities (or angular velocities) and forces information measured in pushing operations, the algorithms to estimate the object mass (or moment of inertia) are described. Then, a line called C.M. Line, is defined in thi:i paper. The line contains the center of mass and is between two fingertips which are in point-contact with an object side. By using two or more than two orientation-different C.M. lines, an algorithm to estimate the center of mass of the object is given. Lastly, experiment(a1 verification on the proposed approach is performed and its results are outlined.

Power assist system with power-damped operation information feedbacking

This research considers a human-limb power assist system, which can feedback the power- damped operating forces to human. The system can easily suitable to a person without using EMG sensor and knowing limbs mass, viscosity and elasticity. The control method, assist rate and system unit are discussed in this paper. Lastly, experimental verification on the proposed approach is performed and its results are outlined.

High-Stiffness and High-Sensitivity 3-Axis Force Sensor Using Strain-Deformation Expansion Mechanism

For dexterously performing object grasping and manipulation with multifingered hand of robot, sensing the fingertip forces with high-stiffness and high-sensitivity is desired. In general, from previous sensing structures, if the stiffness of a sensor is made be higher, its sensitivity will be reduced. This paper proposes a novel mechanism called Strain-Deformation Expansion Mechanism for 3-axis force sensing. By the force sensing mechanism, the small strain-deformation used for force sensing can be expanded while the sensor stiffness will not be reduced but will be heightened. In this paper, the force sensing principle is addressed by analyzing the deformation of the sensing mechanism and the forces acting on the sensor theoretically. Then, the sensitivity of the sensing mechanism and its expansion rate of sensitivity are defined, and a design method for realizing the sensing mechanism with high sensitivity is discussed. Lastly, some experiments are performed to show the basic characteristics and the effectiveness of the sensing mechanism.

Estimation of mass and center of mass of unknown cylinder-like object using passing-CM Lines

In many cases of object manipulation by robot, it is required to know the mass and center of mass of the object. For the case when the weight or shape of an object is over the grasp capacity of a robot hand, we propose a technique that can estimate the mass and center of mass of a graspless unknown object, which has curved surfaces and a base plane. A line, called the passing-CM line, which contains the center of mass is defined. For estimating the passing-CM line, a tipping operation by the robot finger which tips the object slowly and repeatedly in a parallel motion with it vertical operation plane, is proposed. Using the fingertip position and force information measured from the tipping operation, an algorithm to estimate the passing-CM line is described. Then the algorithm to estimate the mass and center of mass of the object is given by estimating the intersect point of several orientation-different passing-CM lines.