Zlatan Car

Evolutionary approach for solving cell-formation problem in cell manufacturing

New environmental characteristics and requirements have challenged manufacturing enterprises to improve the efficiency and productivity of their production activities. Cellular manufacturing (CM) as one of the solutions to this problem, as implementation of Group technology (GT), was proposed. Performance of cellular manufacturing systems depends heavily on the cell structure. In this paper we present and evaluate a novel approach for solving the cell-formation problem based on implementation of a GA, called modified genetic algorithm (MGA). Implementation of the GA in here presented simulation model is based on Emergent Synthesis idea, of top-down problem decomposition and emerging solution from bottom-up feedback.

A compressive sensing based method for cross-terms suppression in the time-frequency plane

Signals with time-varying frequency content are generally best represented in the time frequency (TF) domain, with the components instantaneous frequency laws being their key nonstationary features. There are a number of methods for TF distribution calculation (TFD), however, most of them add unwanted artifacts, making the TFD interpretation more difficult. In this paper, we use a compressive sensing approach to suppress or completely eliminate those artifacts. Furthermore, a basis pursuit algorithm is employed for signal reconstruction in order to reduce resolution loss, which is a mayor obstacle of existing TFD design methods.

Running HPC applications on many million cores Cloud

Despite the various hardware and software improvements in Cloud architecture, there still exists the huge performance gap between the commodity supercomputers and Cloud when running HPC communication intensive applications. In order to find what is preventing them to better scale on Cloud, we evaluated HPL and NAMD benchmarks on HPE Openstack testbed, and NAMD benchmarks on supercomputer located at Rijeka University Supercomputing Center. Our results revealed two major bottlenecks: the throughput of the interconnect, and Cloud orchestration layer, among other responsible for the management of the communication between Cloud instances. We investigated the influence of jittering, but did not find the significant influence on performance. Our conclusion is that by solely increasing the interconnect throughput, one will not improve the scalability of HPC communication intensive HPC applications in Cloud. This is also backed up with NAMD performed at HP Labs, and with HPL benchmark performed at San Diego Supercomputing Center. We propose two possible scenarios of scalability improvements. One with distributed model of Cloud Orchestration layer; another with bare metal containers. Efficient load balancing remains the must if we want to see HPC applications scaling over many million Cloud cores. For this, we propose novel SLEM based load balancing strategy.

MPI applications' performances in native vs. virtualized environments using InfiniBand IPoIB virtualization and live migration

Over recent years we have seen a constant evolution of High-Performance Computing moving into commodity servers cluster types of systems. At the same time we have seen Cloud Computing being a proven, stable and reliable IT paradigm, utilising virtualized clusters of commodity servers as key components. This paper presents a face-to-face native-to-virtual HPC MPI application performance analysis on a range of general-use HPC applications by virtualizing InfiniBand via IPoIB at the guest virtual machine level on VMware ESXi as well as KVM hypervisor with production ready live migration support. Applications running on various small and medium HPC clusters are targeted to address users, considering full IT infrastructure virtualization by merging general purpose with HPC IT infrastructure. Live migration is a key component within a virtualized environment as it enables dynamic virtual IT infrastructure, therefore live migration performance impact is evaluated through a pluggable multi-platform architecture on a proactive fault-tolerance use case.

Analysis of Digitizing and Traditional Measuring System at Surface Measurement of Lids

The focus of this paper will be on comparison at the measurement of container lids between Advanced TOpometric Optical Sensor - ATOS III SO (GOM mbH) and traditional coordinate measuring machine CMM for the measurement of surfaces - Form Talysurf Series 2 (Taylor Hobson Ltd). In the paper, two kinds of measuring methods (noncontact method at ATOS and contact method at CMM Form Talysurf) and techniques will be made for comparison: digitizing measuring system based on the triangulation principle and traditional measuring systems based on the collecting of points from an object by touching it.

Multi-Agent Manufacturing System Design Based on Emergent Synthesis Approach

This paper presents a approach for multi-objective design and reconfiguration of the current manufacturing system. A proposed model for multi-objective design and adaptable reconfiguration is based on the multi-agent principles and Emergent Synthesis concept. Emergent Synthesis is introduced in the adaptable reconfiguration within implementation of the layered based architecture and utilizing the multi-agent concept. Based on the proposed approach a simulation model has been built and evaluated. For the purpose of analysis of this approach it was simulated production in the shop-floor of the manufacturing system with the two different initial configurations. For evaluation of here presented approach the case study was performed using realistic data; it was simulated production of the cellular phone devices. From obtained results of the simulation it can be conclude that a proposed model has a high level of multi-objective adaptation of the manufacturing system shop-floor.

Magnetic Bearing Control System based on PI and PID Controllers

This paper describes the implementation of magnetic bearings and their active control system. The working principle of the special combined axial and radial magnetic bearings and their implementation is explained. The overall laboratory system consists of two magnetic bearings with their housings, the suspended shaft and control system with sensors and power electronics. Sensor electronics are used to measure the position of the shaft within a bearing and to determine the appropriate bearing current with outer position control loops and nested current control loops. The motor control board featuring the TMS320F28335 DSP and LDC1000 proximity sensors is used for control and power electronics. In order to implement the control system the X2C tool is used. This is an open source model based development and code generation tool embedded in the Scilab/Xcos environment. The sensor data acquisition time is optimized to increase the speed of the control system.

Autonomous task allocation by artificial evolution for robotic swarms in complex tasks

Swarm robotics is a field in which multiple robots coordinate their collective behavior autonomously to accomplish a given task without any form of centralized control. In swarm robotics, task allocation refers to the behavior resulting in robots being dynamically distributed over different sub-tasks, which is often required for solving complex tasks. It has been well recognized that evolutionary robotics is a promising approach to the development of collective behaviors for robotic swarms. However, the artificial evolution often suffers from two issues—the bootstrapping problem and deception—especially when the underlying task is profoundly complex. In this study, we propose a two-step scheme consisting of task partitioning and autonomous task allocation to overcome these difficulties. We conduct computer simulation experiments where robotic swarms have to accomplish a complex collective foraging problem, and the results show that the proposed approach leads to perform more effectively than a conventional evolutionary robotics approach.

Influence of Punch Geometry on Process Parameters in Cold Backward Extrusion

In cold extrusion of steel tools make direct contact with the metal to be extruded. Those tools are exposed to high contact stresses which, in certain cases, may be limiting factors in applying this technology. The present paper was bound to the influence of punch head design on radial stress at the container wall in the process of cold backward extrusion. Five different punch head geometries were investigated. Radial stress on the container wall was measured by pin load cell technique. Special tooling for the experimental investigation was designed and made.Process has been analyzed also by FE method. 2D models of tools were obtained by UGS NX and for FE analysis Simufact Forming GP software was used. Obtained results (experimental and obtained by FE) were compared and analyzed. Optimal punch head geometry has been suggested.