Eiji Shintaku

Minimum energy trajectory for an underwater manipulator and its simple planning method by using a Genetic Algorithm

In this paper, a trajectory planning method for an underwater manipulator is proposed. whose criterion of path generation is the energy consumption during operation. The trajectory planning for an underwater manipulator is formulated as a nonlinear optimal control problem. The minimum energy trajectory is obtained as the solution of the two-point boundary-value problem. From the results of a series of numerical calculations, moving the manipulator (e.g. folding its arm) is effective to reduce energy consumption during motion. It is also clear that the optimal travel time of the motion exists when an unbalance of static forces, buoyancy and gravity forces, occurred by a payload and so on. Then to calculate the trajectory without the complexity of formulation and computation, a simple trajectory planning method is also proposed, which uses a Genetic Algorithm (GA). In this method, a polynomial approximates time histories of the trajectory in joint space; the GA determines the parameter of the polynomial to ...

Piezoelectric sensor for stress intensity factor measurement of two dimensional cracks

Abstract A piezoelectric sensor for the measurement of stress intensity factors (SIFs) of two dimensional cracks induced in a structure is developed. Two small pieces of piezoelectric elements are adhered near the crack tip so that the piezoelectric elements are placed close to each other and the crack tip’s position is between them. The electric currents from the piezoelectric elements are integrated by integration circuits and the output voltages which are proportional to the electric charge induced in the piezoelectric elements are measured. The SIFs of Mode I (KI) as well as of Mode II (KII) based on the piezoelectric constitutive law and fracture mechanics are calculated.

Inherent damage zone model for strength evaluation of small fatigue cracks

Abstract An inherent damage zone model is presented to explain the fatigue properties of small sized cracks near the fatigue limit and the crack growth threshold. A special feature of the paper is using the exact stress distributions of notched and cracked specimens at the strength evaluations. Analytical elastic solutions by Neuber and Westergaard are employed for this purpose. A crack propagation law is newly developed based on the inherent damage zone model, and the propagation properties of small sized cracks and the mechanism of non-propagating crack are discussed based on the model. The estimated propagation rates of small sized fatigue cracks, the crack size effect on threshold strength and the occurrence condition of non-propagating crack in elliptic notches and circular holes show good agreements with the previous experimental results.

Stability of augmented staggered method for electromagnetic and structural coupled problem

Numerical instability occurs in analyses of an electromagnetic and structural coupled problem or a magnetic damping problem when the matrix equations of structure and eddy current are solved alternately. In this paper, an augmented staggered method is proposed for the coupled analysis. The stability of this method is demonstrated for the magnetically damped vibration by finite element analyses. According to the characteristic equation obtained from the recurrence relation of this time integration scheme, it is confirmed that this method is unconditionally stable for the intensity of magnetic field and the size of time increment.

Studies on Ship Inspection Supporting System by the use of Product Model

Authors have been developing integrated information system to support ship inspection. In the 1st report, ship inspection was classified into three stages (Plan, Do and Check), and prototype system for inspection planning stage was developed.In this paper, in order to support the “Do (execution)” of inspection, information system to generate information on corrosion and inspection is developed. By carrying this system into inspection, inspector can generate corrosion information and inspection information only by doing easy operations. In order to realize this, some new models and functions are introduced. These are “Inspection State Model”, “Corrosion Model”, “Inspection State Generating Function”, “Corrosion Information Generating Function” and “Time Information Generating Function”. “Inspection State Model” and “Corrosion Model” are information models by which inspection state and corrosions are expressed statically. These models are generated by the use of above mentioned functions by effectively using Product Model, information on inspection planning and image information on corrosion.In order to verify the proposed models and functions, prototype system is developed. Some examples are shown at the end of this paper.

Quantification of Subjective Information and Its Utilization in Reliability Engineering

Subjective information of human are widely utilized in every sphere of engineering. However, subjective data can not be handled in the same way as objective data, if they are not quantified. As the result, subjective data are not introduced in numerical analysis, usually. In this study, fuzzy membership functions are employed in order to quantify subjective classification information. A probabilistic model which can determine the shape of membership function from fuzzy data is proposed. Further, for the utilization of subjective information in reliability engineering, a recursive method to estimate probability density function from subjective classified data is developed. This probability density function can be used in the reliability analysis in the same way as the ordinary probability density function since all the calculation is carried out based on the probabilistic methods.