Constrained incremental predictive controller design for a flexible joint robot

In this paper, an improved predictive control algorithm for controlling a typical nonlinear flexible-joint robot (FJR) with input constraint is proposed. The receding horizon algorithm, called generalized incremental predictive control (GIPC), utilizes both present and previous states rather than present states only. The GIPC algorithm includes the weighted difference of the current and the previous states and the summation of the control action increments. In order to illustrate the effectiveness of the proposed control strategy, it is implemented to the FJR and the results are compared with those of generalized predictive control (GPC). It is demonstrated that the proposed GIPC algorithm is more robust than the standard GPC method. Furthermore, the constrained GIPC algorithm using the quadratic programming removes instabilities caused by actuator saturation.     

Crystallization of hard segment domains with the presence of butane for microcellular thermoplastic polyurethane foams

This paper presents the effects of dissolved butane on the crystallization of hard segment (HS) and its effects on enhancement of cell nucleation to manufacture microcellular thermoplastic polyurethane foams (TPU). The TPU samples were first reprocessed by melt compounding through a twin-screw extruder. A broad distribution of HS domains was generated after this processing, including some perfected HS nano-crystals with a higher melting temperature. In addition to the processing effect, the saturation temperature and the plasticizing butane significantly induced a larger number of HS crystalline domains. Consequently, cell nucleation was significantly promoted in the vicinity of the largely distributed HS crystalline domains over a wider saturation temperature range of 150 °C–170 °C at a saturation pressure of 55 bar.     

Synthesis and properties of new polyamide/multiwalled carbon nanotube nanocomposites containing a pyridine group

The effects of multiwalled carbon nanotubes (MWCNTs) on the thermal properties and flame retardancy of a new polyamide (PA) derived from glutaric acid and aromatic diamine were investigated in this work. The synthesized PA containing pyridine and trialkylamine groups was characterized by ¹H NMR and SEC. The PA unit structure was geometrically optimized at the B₃LYP/6‐311⁺⁺G(d, p) level of theory. PA showed a glass transition temperature of 151 ºC. PA nanocomposites containing two different amounts of MWCNTs were prepared via the solution intercalation technique with the solvent N,N‐dimethylacetamide. Transmission electron microscopy showed that MWCNTs were exfoliated in the polymer matrix, resulting in well‐dispersed morphologies at 3 wt% MWCNT content. The redox behaviors of PA and the nanocomposites were examined using cyclic voltammetry (CV). PA showed a reversible oxidation process in the CV scan. Thermal and flammability properties of the nanocomposites were studied by TGA in nitrogen and air, DSC and with a microscale combustion calorimeter. The TGA results showed that the addition of MWCNTs resulted in a substantial increase in the thermal stability and char yields of the nanocomposites compared with neat PA. The heat release rate and total heat release were significantly reduced in the presence of MWCNTs. © 2013 Society of Chemical Industry     

Development of a Dynamometer to Measure All Forces and Moments Applied on Tillage Tools

A new triaxial dynamometer was designed, constructed and tested to measure and locate the position of all forces and moments on tillage implements, up to a maximum force of 10 kN and a maximum moment of 10 kN × m. The design concept of the facility was based on four frames attached to each other by load cells and tillage tool were attached on the inner frame. Calibration of the system showed the reliable and precise performance of the dynamometer in tracking the forces and moments. Additionally, the designed setup operated desirably under field conditions. Draft measurement was compared to those predicted by ASABE Standard D497.7 and was found to be in standard range. By using the new facility, it would be possible to study the relationship between forces and moments at the varying practical cases and design of tines, toolbars and tillage equipments in regard to the soil type and available tractor power will be facilitated.     

Design and performance of active power filters

This article has demonstrated the feasibility of a three phase active filter based on a half-bridge topology. Design guidelines for the power circuit have been derived and applied to a 5 kVA IGBT laboratory prototype. In the single phase mode, the active filter can reduce the low frequency harmonic content in the AC line to below 1% excluding the harmonics due to switching action of the converter. In the three phase mode, line currents are corrected under balanced and unbalanced conditions. The neutral current is reduced significantly.     

Effect of notch location on fatigue crack growth behavior of strength-mismatched high-strength low-alloy steel weldments

Welding of high-strength low-alloy (HSLA) steels involves the use of low-strength, equal-strength, and high-strength filler materials (electrodes) compared with the parent material, depending on the application of the welded structures and the availability of filler material. In the present investigation, the fatigue crack growth behavior of weld metal (WM) and the heat-affected zone (HAZ) of undermatched (UM), equally matched (EM), and overmatched (OM) joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) has been used to fabricate the butt joints. A center-cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behavior of welded joints, utilizing a servo-hydraulic-controlled fatigue-testing machine at constant amplitude loading (R=0). The effect of notch location on the fatigue crack growth behavior of strength mismatched HSLA steel weldments also has been analyzed.     

Construction Business Competitiveness and Global Benchmarking

The focus of this paper is on developing “quality” and sustainable construction businesses capable of riding market shifts and growing both nationally and internationally. Knowledge of current management tools and techniques will no doubt prove useful in the quest for transforming a nonperforming business. However, no long lasting effect can be expected unless attention is paid to the fundamental principles and practices that govern organizational behavior, including the views an organization has of its customers, competitors, and itself. Commercial performance of organizations has increasingly become not only dependent on resource efficiency, but also on retooling and aggressive new business development initiatives as well as reduction in base production and operational costs. The human factors and mental models that people have within any given organization profoundly affect the success or failure of that organization. In this paper a critical review of the current concepts and techniques influencing construction organizations is offered with a focus on people and organizational improvements. A set of critical success factors is then distilled, followed by a systematic process of applying the same to achieve success.     

A novel hybrid intelligent model of support vector machines and the MultiBoost ensemble for landslide susceptibility modeling

The main aim of this study is to propose a novel hybrid intelligent model named MBSVM which is an integration of the MultiBoost ensemble and a support vector machine (SVM) for modeling of susceptibility of landslides in the Uttarakhand State, Northern India. Firstly, a geospatial database for the study area was prepared, which includes 391 historical landslides and 16 landslide-affecting factors. Then, the sensitivity of different combinations of these factors for modeling was validated using the forward elimination technique. The MBSVM landslide model was built using the datasets generated from the best selected factors and validated utilizing the area under the receiver operating characteristic (ROC) curve (AUC), statistical indexes, and the Wilcoxon signed-rank test. Results show that this novel hybrid model has good performance both in terms of goodness of fit with the training dataset (AUC = 0.972) and the capability to predict landslides with the testing dataset (AUC = 0.966). The efficiency of the proposed model was then validated by comparison with logistic regression (LR), a single SVM, and another hybrid model of the AdaBoost ensemble and an SVM (ABSVM). Comparison results show that the MBSVM outperforms the LR, single SVM, and hybrid ABSVM models. Thus, the proposed model is a promising and good alternative tool for landslide hazard assessment in landslide-prone areas.

     

Fast edge-based stereo matching approach for road applications

Several vision-based road applications use stereo vision algorithms, and they generally must be fast to be applied in real time. The main problem in stereo vision is the stereo matching problem, which consists in finding correspondences between two stereo images. In this paper, we present a new fast edge-based stereo matching approach devoted to road applications. Two passes of the dynamic programming algorithm are applied to estimate the final disparity map. The matching results of the first pass are only exploited to compute an initial disparity map (IDM). The so-called guiding edge points (GEPs) together with disparity ranges, i.e., possible matches, are derived from the IDM. In the second pass, the disparity ranges are used to reduce the search space as well as the mismatches and the GEPs to control and guide the matching process to the optimal solution. The proposed method has been tested on both real and virtual stereo images, it has been compared to a recently proposed method, and the results are satisfactory.