Optimal cascade hydraulic control for a parallel robot platform by PSO

A new cascade load force control design for a parallel robot platform is proposed. A parameter search for a proposed cascade controller is difficult because there is no methodology to set the parameters and the search space is broad. A parameter search based on particle swarm optimization (PSO) is suggested to effectively search the parameters of the cascade controller. We used a unified mathematical model of a hydraulic actuator of parallel robot platform. These equations are readily applicable to various types of proportional valves, and they unify the cases of critical center, overlapped, and underlapped valves. These unified model equations are useful for nonlinear controller design. Simulation results show the advantages of the proposed optimal tuned cascade controller to solve the formulated tracking problem in relation to the classical proportional–integral (PI) controller.     

Isogeometric bending analysis of composite plates based on a higher-order shear deformation theory

This research paper presents an isogeometric plate finite element formulation for analysis of thick composite plates. Isogeometric finite element method which is based on non-uniform rational B-splines (NURBS) basis functions, is a novel numerical procedure developed to bridge the gap between CAD and FEM modeling of structures. In order to investigate the behavior of isogeometric plate elements under static loading, plate kinematics is based on third order shear deformation theory (TSDT) of Reddy, which is free from transverse shear locking. This paper discusses accurate transverse stress recovery procedures for TSDT isogeometric finite elements. Numerical experiments with quadratic, cubic and quartic elements are presented and obtained results are compared to other available ones.     

The investigation of the lower limb geometry using 3D sonography and magnetic resonance

The main aim of this work was to test the developed system of a free hand sonographic probe in the clinical conditions. The measuring system consists of navigation system tracking the position of a linear ultrasound probe and the self-developed software to control the tools and analyse the recorded data. It enables both measurement of geometrical parameters according to the self-designed template and the identification of the three dimensional shape of bone. Moreover the software provides virtual planning of surgery and supports the surgeon to execute the planned scenario in the reality.     

Feature signature prediction of a boring process using neural network modeling with confidence bounds

Prediction of machine tool failure has been very important in modern metal cutting operations in order to meet the growing demand for product quality and cost reduction. This paper presents the study of building a neural network model for predicting the behavior of a boring process during its full life cycle. This prediction is achieved by the fusion of the predictions of three principal components extracted as features from the joint time–frequency distributions of energy of the spindle loads observed during the boring process. Furthermore, prediction uncertainty is assessed using nonlinear regression in order to quantify the errors associated with the prediction. The results show that the implemented Elman recurrent neural network is a viable method for the prediction of the feature behavior of the boring process, and that the constructed confidence bounds provide information crucial for subsequent maintenance decision making based on the predicted cutting tool degradation.NSF Industry/University Cooperative Research Center (NSF I/UCRC) forIntelligent Maintenance Systems(IMS).     

Design of product polar quantizers for A/D conversion of measurement signals with Gaussian distribution

In this paper, a design of product polar quantizers for A/D (analog-to-digital) conversion of measurement signals and an analysis of their performances in the wide range of variances are considered, in a general manner, i.e. for any compression function. Special attention is devoted to the design of robust product polar quantizers, applying the developed theory on μ-law logarithmic compression function, which is very important since a lot of measurement signals are nonstationary. The proposed quantizers achieve much better performances than scalar quantizers (they have higher the maximal SQNR (signal-to-quantization noise ratio) for about 2.5 dB and they are more robust), without increasing of complexity. Theory is proved by simulation. These quantizers can be applied for many different types of measurement signals and can be used in many measurement systems (telemetry, telemedicine, wireless sensor networks, etc.).     

Study of Dependability Evaluation for Multi‐hierarchical Systems Based on Max–Min Composition

This article presents the model for calculating the performance of dependability for complex technical systems. According to ISO‐IEC 300, dependability is an overall indicator for the quality of service and considers simultaneously reliability, maintainability, and maintenance support. For a proper understanding of the quality of service for any technical system, it is important to define dependability performance at the level of single component as well as at the upper levels—levels of subsystems and entire system. As dependability indicators (reliability, maintainability, and maintenance support) have been defined as linguistic variables, the fuzzy max–min composition has been used for the dependability determination and integration of its indicators. A procedure for the synthesis of single components dependability performance to upper levels in complex technical system is proposed. Max–min composition is again used as a tool for fuzzy synthesis because it enables obtaining the comprehensive and synergetic effect in a process of dependability evaluation. A practical engineering example (mechanical systems at bucket wheel excavator) has been used to demonstrate the proposed dependability synthesis model. Copyright © 2012 John Wiley & Sons, Ltd.     

Untersuchung des zweiten Duktilit?tsminimums mikrolegierter St?hle mit einer neu entwickelten Hei?zugprüfung

The chemical composition as well as the temperature cycles and forces arising during the continuous casting process have a decisive influence on the microstructural evolution and therefore on the ductility behaviour of microalloyed steels. During the bending and straightening operation, typically in a temperature range between 700?°C and 1100?°C, the ductility of the continuous cast product is reduced, which often leads to transversal surface cracks. In the present paper this “second ductility minimum” of microalloyed steels with various titanium contents was investigated by means of an in-house developed hot tensile testing method at the Institute for Materials Science and Welding (Graz University of Technology). The technique provides an investigation of the high temperature properties of in-situ solidified steel samples and facilitates new insights into the materials behaviour with focus on the solidification process (“on-cooling” tests), generating microvoids and cracks similar to continuous casting conditions, as well as more or less identical microstructures and precipitation processes. In contrast to conventional hot tensile tests in literature, where an improvement of the ductility by the addition of the micro-alloying element titanium could be observed, this behaviour could not be noticed with the present investigation in the case of the steel with a higher titanium-amount.     

Resource-Saving Press for Oil Extrusion from Plant Sources

Russian Engineering Research - A highly efficient press is developed for extruding oil from low- and high-quality crops.     

An improved non-adiabatic FEM model of a line-to-earth fault in buried power cables

It is shown in this paper that the non-adiabatic nature of phase-to-earth fault thermodynamics in buried power cables can be modelled in an even more precise manner by using the FEM. The nonlinear FEM model has been created on the basis of an authentic case of fault caused by a previous mechanical damage of the cable sheath and insulation, as well as heat sources, thermo-physical and electrical material properties as functions of temperature and time. The proposed model is applicable to power cables of all voltage levels with different polymer insulations laid in soils with changeable moisture content, as well as to the dry arc tracking or wet arc tracking phenomena in PVC-insulated cables.     

A Flexible Approach for the Reinforcement of Water Networks Using Multi-Criteria Decision Analysis

Water Resources Management - This work proposes a multi-criteria decision analysis (MCDA) as a useful tool for supporting interventions to overcome problems faced by water utilities due to...