A neural network compensator for uncertainties of roboticsmanipulators

A neural network controller for trajectory control of robotic manipulators that is used not to internalize the inverse dynamic model of the controlled object but to compensate only the uncertainties of the robotic manipulator is presented. Its performance is compared with that of the conventional adaptive scheme. The results show the ability of the neural network controller to adapt to unstructured effects. A learning method for the neural network compensator with true teaching signals is shown. The tracking error of the robotic manipulator was greatly reduced when this controller was used     

Higher-order structures and mechanical properties of stereocomplex-type poly(lactic acid) melt spun fibers

Equimolar blend of poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) was melt spun into fibers and the relations among the processing conditions, crystalline structures, thermal properties, and mechanical properties were investigated. Drawing and annealing were performed in order to obtain fiber mainly consisting of the stereocomplex crystal phase. Fibers drawn at various temperatures exhibited either amorphous, highly oriented homo crystal, or the mixture of homo and stereocomplex with a fairly low orientation depending on the drawing temperature. Annealing of the drawn fibers at an elevated temperature higher than the melting temperature of homo crystal increased the stereocomplex content significantly. The fractions of the homo and the stereocomplex crystals strongly depended on the higher-order structure of the drawn fibers and the annealing temperature.     

Higher order structures and mechanical properties of bacterial homo poly(3-hydroxybutyrate) fibers prepared by cold-drawing and annealing processes

Pure bacterial homo poly(3-hydroxybutyrate) (PHB) fibers were prepared by melt spinning, followed by cold-drawing in an amorphous state at a temperature just above its glass transition temperature. Cold drawn fibers obtained were further drawn at higher temperatures, followed by annealing at various temperatures under tension. Relations among the processing conditions, higher order structures and mechanical properties were investigated using wide- and small-angle X-ray diffractions (WAXD and SAXD, respectively), birefringence, differential scanning calorimetry (DSC), and tensile measurements. PHB has two different crystalline forms, 2₁ helix conformation (α-form) and planar zigzag conformation (β-form). A single broad reflection of β-form was detected even in a PHB fiber drawn once at a temperature just above its T_g immediately after quenching and it tended to be stronger after 2nd drawing at higher temperatures. Annealing under low temperature and high tension facilitates the occurrence of β-form. It is suggested that the β-form crystal is formed not only from the tie chains between α-form lamella, but also from completely free amorphous chains. Changes in the amount of two types of crystals were analyzed using the WAXD integrated intensity. Birefringence of these fibers shows negative and positive values, depending on process conditions. Changes in higher order structure on the mechanical properties are also discussed.     

Radiation-induced graft copolymerization of butadiene on polyethylene by trapped radicals

The low-temperature grafting of butadiene on polyethylene (PE) preirradiated in air is compared with that on PE preirradiated in vacuo for the effect of several factors on the grafting. Little fundamental difference between the two cases was observed. In both cases the graft conversion curve is trapped radical type and the overall activation energies are 9.7 and 8.4 kcal/mol for 0.947-density PE and 0.916-density PE, respectively. Percent grafting is proportional to the square root of the dose rate (= total dose). The retarding effect of oxygen at irradiation or storage after irradiation on the grafting scarcely appears when the irradiation temperature or storage temperature is below 15°C. For thinner film and lower density of PE this effect appears clearly at the higher temperature. Therefore, it may be concluded that the low-temperature grafting of butadiene onto PE preirradiated in air is initiated predominantly by nonoxidized radical (allyl radical) trapped in PE and that the grafting reaction occurs in the semicrystalline part of PE.     

Visualization of phase objects by use of a differentiation filter

For the visualization of phase objects by use of a differentiation filter, the phase variation is changed into the intensity variation by differentiation, and then the differentiated image is integrated. In the method used in practice, the differentiated image has been recorded on a film, and then integrated by use of a filter. In this paper, however, the image differentiated by means of a filter is entered into a computer using a CCD camera and then integrated. As a result, the method provides rapid on-line processing. We have performed computer simulations and a detailed analysis of the differentiation filter and also provide the experimental results of three-dimensional image visualization.     

Fusion of fuzzy/neuro/evolutionary computing for knowledgeacquisition

Soft computing is a consortium of methodologies, which deal with various kinds of inaccuracies and uncertainties contained in real-world problems. In this paper soft computing is discussed from the viewpoint of a combination of characteristic features unique to fuzzy, neural, and evolutionary computing. This paper is intended to describe particularly the knowledge acquisition from inaccurate and uncertain data and to point out the areas where soft computing can become a breakthrough technology