Advanced Materials Research Vols. 468-471

Abstract: The analytical stiffness equations of 6-SPS spatial parallel manipulator were deduced based on the Conservative Congruence Transformation (CCT) stiffness matrix. The stiffness mappings of the 6-SPS manipulator were given to show the change and behavior of the stiffness with external forces acted on the manipulator. The results show that the stiffness of the 6-SPS manipulator is configuration dependent, and proportional to the actuating forces and joint stiffness. The stiffness is correlates not only to the magnitude of external forces but also the direction of the external force acted upon.

Abstract: A dynamic hybrid position/force control method is developed for the coordination of two manipulators of a dual-arm robot to cope with the case of dual-arm tightly cooperate a common rigid object in the presence of environmental constraint. Begin with the definition of a group of generalized motion and force vectors used for task description, and by synthesizing the object dynamics and manipulator dynamics, an object-oriented dynamic equation of the dual-arm rigid coordination system is first derived, where relationships between object motion, internal stress force, and environmental contact force are explicitly presented. Furthermore, this equation and that of single arm dynamics in Cartesian still remain the same form. Based on this definition and description, the dynamic hybrid position/force control scheme for dual-arm symmetric coordination is then designed, and the decomposition and parallel realization of the control algorithm is also discussed. Several experiments have been done on two coordinated PUMA562 robot manipulators, which show that the proposed method works effectively, where the object motion and internal/external force can be simultaneously controlled during cooperation.

Abstract: The changes on microstructure, including cortical cell structure, density and degree of crystalline, of yak hair fiber have been analyzed after the stretching slenderization in this paper. It was found that the cortical cell has been elongated and became thinner, which average length-diameter ratio could be raised from 18 to about 40. By means of ultrasonic separation technology, the effect of stretching on packing action of fiber cortical cells has been investigated. It was proved that the stretching slenderization would improve the structure of yak hair cortex, and cortical cells were packed tighter along the fiber. The density and degree of crystalline also increased as raise of stretching rate. At the same time, the results form tensile test indicated that the fiber physical property would be improved through stretching treatment.

Abstract: In this thesis, we apply Power Spectrum in fabric weave recognition, use power spectrum to analyze fabric image by image lightness features at definite illumination, and then extract fabric weave texture features. We can obtain fabric weave image power spectrum curve by Fourier Transform. From the curve, we can extract direction information of fabric weave, and get fabric weft density, then calculate weft Tex, weft number, weft repeats. Experiments prove the method practical and useful for fabric weave computer automatic analysis.

Abstract: In the present study, an amino group modified hypercrosslinked polymeric adsorbent RDM-200 was prepared and its ability to adsorb pipemidic acid from aqueous solution was tested by using Amberlite XAD-4 as a comparison. Pipemidic acid adsorption isotherm onto RDM-200 is well described by the Freundlich model. The RDM-200 adsorption capacity for PPA was about 510.5 mg/g at 293 K, exhibited larger uptake and stronger affinity of pipemidic acid than XAD-4. The adsorption thermodynamic parameters were calculated and the adsorption was an exothermic, favorable, and more ordered process. The RDM-200 spontaneously adsorbs pipemidic acid mainly by both entropy change and enthalpy change. The RDM-200 exhibited excellent adsorption ability over the pH range 6-10, NaCl showed the positive effect.

Abstract: N-methyl pyrrolidonium hydrosulfate ([Hnmp]HSO₄) was synthesized and characterized. N-butyl acetate was synthesized from acetic acid and n-butanol with [Hnmp]HSO₄ as catalyst in a catalytic rectification column 30 mm in diameter and 2.5 m in height. Effects of catalyst dosage, bottom temperature, feeding ratio of acetic acid to n-butanol, feeding method and reflux ratio on esterification and rectification were investigated. Under optimal condition which taking both energy cost and product quality into account: catalyst dosage was 0.5% of feed weight, bottom temperature was 120 °C, mole ratio of acetic acid to butanol was 1:1.2, acetic acid and butanol were mixed and fed above second section of packing, feeding rate was 150 mL/h and reflux ratio was 4, mass fraction of n-butyl acetate in bottom could reach 92.49 %.

Abstract: The ultra-fine TiB2-Ti(C, N) composite powders were prepared by self-propagating high-temperature synthesis (SHS) with Ti, BN and C powders as its starting materials. The morphology of the products was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed the composite powders were consisted of the mainly phases Ti(C, N), TiB2 and a small amount of TiN phase. With the Ni addition, the brittle phase Ni3B was appeared. SEM results revealed that the composite powders had a uniform particle size, a round grain-shaped structure and a narrow size distribution and the average particle size of which is less than 1μm.

Abstract: Since the heavy current and frequent start-stop of portable electric tool, the special energy saving power assisted system is designed. The method for solving these problems is to make a binary power supply with super capacitor and lead-acid battery. The super capacitor provides power assistance to increase output current when starting and recycles inertia energy when stopping, the energy distribution is done by control system. In this paper, the operation principle and control circuit are described and the effect of the proposed system is tested by experiment. The experiment results show that the proposed system double the output current and save energy around 20%. In this way, the problems of short-lifetime and inefficient power take off are solved and this energy saving power assisted system is also appropriate to electric mobile and so on which employ secondary electric power supply as power.

Abstract: In this paper, the variation equivalence problem in machining process is investigated. First, the variation equivalence model is introduced to study the equivalent transformation among different variation sources. Then we propose a concept of maximum possible variation equivalence area, based on which an approach to estimating the possibility of occurrence of the variation equivalence phenomenon is given. An example is presented to illustrate the proposed approaches.

Abstract: Aim at Individual Soldier Automatic Weapon (ISAW), three-dimensional FE model and thermoelasticity coupling model of barrel were built. The coupling temperature field and coupling stress field of the barrel were calculated. Laws of the coupling temperature field and coupling stress field were obtained. The coupling temperature field and coupling stress field of different set of barrel aim at automatic fire were compared. The results show that the Material Properties of the barrel is security. Current research work will be helpful the Individual Soldier Automatic weapon design and the life of barrel study.