Balanced Line Research Articles

An integrated approach for line balancing and AGV scheduling towards smart assembly systems

PurposeOptimizing material handling within the factory is one of the key problems of modern assembly line systems. The purpose of this paper is to focus on simultaneously balancing a robotic assembly line and the scheduling of material handling required for the operation of such a system, a topic that has received limited attention in academia. Manufacturing industries focus on full autonomy because of the rapid advancements in different elements of Industry 4.0 such as the internet of things, big data and cloud computing. In smart assembly systems, this autonomy aims at the integration of automated material handling equipment such as automated guided vehicles (AGVs) to robotic assembly line systems to ensure a reliable and flexible production system.Design/methodology/approachThis paper tackles the problem of designing a balanced robotic assembly line and the scheduling of AGVs to feed materials to these lines such that the cycle time and total tardiness of the assembly system are minimized. Because of the combination of two well-known complex problems such as line balancing and material handling and a heuristic- and metaheuristic-based integrated decision approach is proposed.FindingsA detailed computational study demonstrates how an integrated decision approach can serve as an efficient managerial tool in designing/redesigning assembly line systems and support automated transportation infrastructure.Originality/valueThis study is beneficial for production managers in understanding the main decisional steps involved in the designing/redesigning of smart assembly systems and providing guidelines in decision-making. Moreover, this study explores the material distribution scheduling problems in assembly systems, which is not yet comprehensively explored in the literature.

Оцінювання збалансованості розвитку національної економіки: структурно-динамічний аспект

The work is devoted to the grounding of the scientific and methodological aspects and forming the practical recommendations for evaluation of national economy’s development balance. Assessment’s results are aimed at strict explanation of real economic dynamics to find relevant instruments and impact mechanisms to target national economic development to the mainstream. Structural and dynamic approach to the estimation gives an opportunity to neutralize the complexity of national economy as an object for the evaluation by means of building the phase portraits of national economic sectors’ movements in two-dimensional phase space structured with the balanced lines. Practicability of the “balanced growth concept” implementation as a part of the national economy’s balance development evaluating is scientifically proved. Using of the concept’s mechanisms and principles at the macro level of national economic systems’ evolution is proposed. The structural and logical schema of balanced indicators is formed. Empirical research of Ukrainian national economy’s balance development is done during 2008-2012’ period. Matrix of growth quality assessment is built for the main sectors of national economy. The conclusions about security, sustainability and expediency of national economic growth rates, its structural components are made. The national economy’s sectors characterized with the most sustainable and regular behavior according to assessment based on indicators of a Balanced Growth Rate and Sustainable Development Index are picked out. General results of balance and prospects of national economy’s development are formed.

Design Analysis and Evaluation of a W-Element Model for a Twisted-Pair Cable

Unlike the twisted pair cable's simple installation mechanism, evaluating a circuit equivalent and certifying it is not very convenient anymore. Although the best way to model transmission lines is to use the field solver software programs such as ANSYS Maxwell or HFSS, this procedure is very overwhelming and time-consuming. This paper presents a straightforward approach to extract a W-element model for the twisted pair cable based on its structural and electrical characteristics. The W-element model employs a novel state-of-the-art transmission line simulation method which is very fast, accurate and robust. Both system designers and cable manufacturers can easily exploit the presented equations and the derived models to predict the behavior of the balanced transmission lines with two conductors using simulators such as HSpice, etc. Nexans unshielded CAT6 twisted pair cable, one of the most common types of cables used in today's networks, is selected as a case study in this paper to verify the proposed model. A variety of simulations have been carried out to evaluate the performance and accuracy of the proposed model. Furthermore, the validity of the model is assessed against the real Fluke test results.

Enhanced Model Predictive Control-Based STATCOM Implementation for Mitigation of Unbalance in Line Voltages

This paper presents detailed implementation of static synchronous compensator (STATCOM) based on model predictive control (MPC) for mitigating unbalance in line voltages. The main objective is to evaluate the capability of an enhanced MPC state-space model that can be applied in a general form for any power system. The proposed enhanced MPC state-space model presented in this paper is adapted for mitigating unbalanced voltages at nominated buses by injecting suitable unbalanced currents and reactive powers by STATCOM. In addition, a proposed MPC objective function is developed and implemented to predict STATCOM injected output current according to line voltages of adjacent buses. This enables expecting the fluctuations from any part in the network to maintain nominated bus voltage at reference value. The results of MPC technique are compared with the same MPC technique developed for balanced line voltage mode.

Improvement of Operational Performance through Value Stream Mapping and Yamazumi Chart: A case of Bangladeshi RMG Industry

To secure a competitive position in the global market, the Ready Made Garment (RMG) sector in Bangladesh has been facing various challenges including the improvement of industrial operational performance. Among the various operational issues, balancing the cycle time along the production line is felt to be a common and effective way for enhanced performance. There are numerous exact and approximate methods which have already been proposed and are available in literature for repetitive batch production. Unfortunately such approaches are rarely applied in the real RMG shop floor presumably due to the enormous efforts needed to align with the frequent changes of product lines. Compared to the exact and approximate methods, adoption of lean tools like VSM and Yamazumi chart is highly acclaimed for their simpler and wider applicability with superior capability in addressing and solving the balancing problems. So for balancing purposes of the RMG shop floor an attempt is made to frame and apply an integrated model combining the VSM and Yamazumi chart as presented in this article. Depending on the theoretical framework, operational performance of an RMG shop floor is evaluated upon balancing the cycle time. In doing so, firstly a current state map (CSM) and the corresponding Yamazumi chart are plotted to comprehend the existing operational procedure and analyse the workstation cycle time with respect to the takt time. Using the Yamazumi chart, the workstations are reorganized to reduce or eliminate the non-value added activities, to introduce parallel workstations, and to merge workstations so that a balanced production line is attained. Performance is then assessed by means of Overall Effectiveness of Equipment (OEE), Capacity Utilization and Efficiency. The results as obtained through testing a real life case study of RMG industry, ensure the effectiveness of the integrated system of VSM and Yamazumi chart to identify the wastes, restore the line balance and improve operational performance.

Differential Transmission Lines Loaded With Magnetic LC Resonators and Application in Common Mode Suppression

This paper presents the analysis of magnetic LC (MLC) resonators loaded with differential microstrip transmission lines. The analysis is based on an equivalent circuit model describing the electromagnetic behavior of the MLC resonators. It is shown that a pair of microstrip lines loaded with MLC resonators exhibit a dual-mode bandstop response in the common mode of operation, while being transparent to the differential signals. This characteristic can be used in the design of differential transmission lines with wideband common mode suppression. Circuit models together with Bloch theorem are applied for the systematic design, where the dispersion analysis helps to estimate the maximum achievable common-mode rejection bandwidth. A systematic design procedure is developed for designing differential transmission lines using this method. The theoretical analysis is validated by designing and measuring a balanced transmission line using three cascaded MLC-based cells. The measurements exhibit more than 40-dB common-mode signal suppression for a fractional bandwidth of 32% around 1.3 GHz, whereas the fraction bandwidth for 20-dB suppression level is 57.5%. The fabricated prototype has a compact size of $0.09\lambda _{g}\times 0.37\lambda _{g}$ , where $\lambda _{g}$ is the guided wavelength at 1.3 GHz. A detailed comparison between the designed MLC-based differential transmission line and the state-of-the-art designs shows a superior performance of the MLC-based transmission lines in terms of size, fabrication simplicity, and the common-mode rejection level.

Balanced line separators of unit disk graphs

We prove a geometric version of the graph separator theorem for the unit disk intersection graph: for any set of n unit disks in the plane there exists a line ℓ such that ℓ intersects at most O((m+n)log⁡n) disks and each of the halfplanes determined by ℓ contains at most 2n/3 unit disks from the set, where m is the number of intersecting pairs of disks. We also show that an axis-parallel line intersecting O(m+n) disks exists, but each halfplane may contain up to 4n/5 disks. We give an almost tight lower bound (up to sublogarithmic factors) for our approach, and also show that no line-separator of sublinear size in n exists when we look at disks of arbitrary radii, even when m=0. Proofs are constructive and suggest simple algorithms that run in linear time. Experimental evaluation has also been conducted, which shows that for random instances our method outperforms the method by Fox and Pach (whose separator has size O(m)).

Signal Balancing in Unbalanced Transmission Lines

Balanced lines operating as transmission line interconnects are subjected to differential-mode to common-mode conversion (and vice versa) in situations where symmetry imbalances (e.g., caused by line bends) are unavoidable. In this paper, a technique to compensate for such symmetry imbalances, providing pure differential-mode signals at the differential output port of the line, is presented. Such technique uses a rat-race balun (to generate the differential-mode signal) with the isolated port conveniently loaded, and it is based on the modification of the characteristic impedance of one of the unbalanced lines. A detailed analysis that justifies this compensation technique (valid for any arbitrary four-port network) and provides the design equations is presented. The approach is validated through simulation and experiment, by demonstrating that common-mode signals are not transmitted to the differential output port of a bended (i.e., unbalanced) line pair.

Smart Fault-Tolerant Control System Based on Chaos Theory and Extension Theory for Locating Faults in a Three-Level T-Type Inverter

This study proposes a smart fault-tolerant control system based on the theory of Lorenz chaotic system and extension theory for locating faults and executing tolerant control in a three-level T-type inverter. First, the system constantly monitors the fault states of the 12 power transistor switches of the three-level T-type inverter; if a power transistor fails, the corresponding output phase voltage waveform is converted by a Lorenz chaotic system. Chaos eye coordinates are then extracted from a scatter diagram of chaotic dynamic states and considered as fault characteristics. The system then executes fault diagnosis based on extension theory. The fault characteristic value is used as the input signal for correlation analysis; thus, the faulty power transistor can be located and the fault diagnosis can be achieved for the inverter. The fault-tolerant control system can maintain the three-phase balanced output of the three-level T-type inverter, thereby improving the reliability of the motor drive system. The feasibility of the proposed smart fault-tolerant control system was assessed by conducting simulations in this study, and the results verified its feasibility. Accordingly, after the occurrence of the fault in power switches, the balanced three-phase output line voltage remained unchanged, and the quality of the output voltage was not reduced by using the integration of the proposed fault diagnosis system and fault-tolerant control system for a three-level T-type Inverter.

Investigation on Current Reduction Effects of Baluns for Measurement of a Small Antenna

When connected to a small antenna that is undergoing testing, metal cables, such as coaxial cables, sometimes cause significant errors. This effect can be large when the antenna and ground plane are small and asymmetric. A balun is proposed for use in antenna measurement to reduce the influence of measurement cables. Baluns were originally utilized for a transformer set between unbalanced and balanced lines to feed a balanced antenna, such as a dipole antenna. Many types of baluns are used to transform unbalanced lines into balanced lines, and vice versa. However, when it comes to the utilization of baluns for antenna measurement, it is not clear whether all types of baluns can reduce the influence of the measurement cable. In this paper, baluns are sorted into two groups with regard to their effect on the reduction in unbalanced current when measuring a small antenna. Furthermore, the effect of a balun on improving the accuracy of impedance and radiation pattern measurements is also investigated.

Bipartite Consensus of High-Order Edge Dynamics on Coopetition Multiagent Systems

The bipartite consensus of high-order edge dynamics is investigated for coopetition multiagent systems, in which the cooperative and competitive relationships among agents are characterized by positive weight and negative weight, respectively. By mapping the initial graph to a line graph, the distributed control protocol is proposed for the strongly connected, digon sign-symmetric structurally balanced line graph; and then we give sufficient conditions for the third-order multi-gent system to achieve both the bipartite consensus of edge dynamics and the final value of bipartite consensus. By transforming the coefficients of characteristic polynomial from complex domain to real number domain, the sufficient conditions for the bipartite consensus of high-order edge dynamics are also proposed, and the final values of the high-order edge dynamics on multiagent systems are obtained.

A Multiobjective Integer Linear Programming Model for the Cross-Track Line Planning Problem in the Chinese High-Speed Railway Network

In China, cross-track high-speed trains (CTHSTs) play an important role in railway passenger transportation, with an increasing number of cross-track passengers sourced from the expansion of high-speed railway (HSR) network. The CTHST generally has long travel times, so running CTHSTs is not beneficial for train rescheduling work and plan’s periodicity in the periodic operation context. Thus, the main challenge in cross-track line planning is looking for a symmetry point between passenger transportation and disadvantages of running CTHSTs, which are two conflicting aspects. In this study, we developed a multiobjective integer programming model to produce a balanced cross-track line plan by combining individual-track high-speed trains (ITHSTs) into CTHSTs, which is a discrete optimization problem. This strikes a balance among four goals: the periodicity of the line plan, CTHST quantity, CTHST mileage, and CTHST stops in the context of periodic operation, while satisfying the constraints of passenger demand and the number of available ITHSTs. Numerical experiments are conducted based on a real-world network and optimal solutions were quickly obtained. We analyzed impacts of each goal and parameter on the result and influencing factors of computation. Comparisons with existing methods and real-life plans were also presented to show improvements made by proposed model.

Class of easily implementable fixed‐length to variable‐length balanced binary line codes

This Letter introduces a class of fixed-length to variable-length balanced binary line codes. By considering fixed size blocks of source digits, a balanced line code is constructed by appending a minimum number of 0's or 1's to each such block in order to produce words having equal number of 0's and 1's, i.e. balanced words of variable length. By taking into account the design constraint of being easily implementable in practice, the construction introduced achieves high coding efficiency and is at least asymptotically optimal in terms of redundancy.

Improving Flow Lines by Unbalancing

The paper's aim is to show how the performance of a balanced manufacturing flow line can be improved on the critical WIP level by making it unbalanced to some extent. The explanation and a quantitative example are presented. There is a trade-off between system balance and stability, and it can be handled as an optimization problem. Data are gathered using a physical simulation system. The analysis is carried out with a discrete time simulation program which applies next-event time advance mechanism. The model has been implemented in AIMMS modelling language.

Production Efficiency Improvement by Using <i>Tecnomatix</i> Simulation Software and RPWM Line Balancing Technique: A Case Study

One of the most used production systems is the assembly line balancing which is used to improve or balance different production line of different industries all over the world. This paper is about improving the productivity of a particular sewing line of a Duffle Trolley (DFT) bag of VIP Industries Bangladesh Private Limited by balancing the line. By balancing the line product can be produced at a high production rate in the shortest time with an optimum productive way which is also cheap and demanded quality. This paper identifies the opportunities for improvement of current sewing line by performing RPWM (Ranked Positional Weight Method) line balancing technique and testing feasibility using Tecnomatix simulation software. In this study, at first-time study of each operation was performed. For each process SMV (standard minute value), the existing line efficiency and production cycle time also labor productivity were calculated. Then using the precedence diagram and RPWM a balanced line layout was found and the line was tested by Tecnomatix software for validity. The final result obtained was an optimized and improved balance line layout for the sewing line. Finally, following this, the company will be able to produce the product at a high production rate through the minimum cost and meet the daily production target.

Profound Changes of the World and China-US Trade Disputes

We are facing profound changes in the world in the 21st century. Various contradictions in the world become more intensive. Deep globalization has promoted a more integrated and efficient human society. Meanwhile, it has become more unbalanced, uncertain and contradictory. The movement of contradictions in the world tends to go from extremes to opposites. The development of human society will see the emergence of several civilization centers, instead of civilization center taking the place of another. The current China-US trade disputes is of the important appear of the profound change. The contradictory movements of China-US economic and trade relations are eternal while constants are relative, but changes in the basic structure of China-US relations will take place over a long period of time. The China-US trade problem is actually an imbalance problem, reflectsing the deep-seated and complex contradictions between developed and emerging developing countries in the global transformation. To solve the current China-US trade war, we need to take a balanced line. The China-US trade problem has accumulated over the past decades, and it will take some time to solve them. A scrutiny of China-US trade disputes in the profound changes of the world and the context of modernization shows that China has been working to address many of the issues of concern, which complies with China’s general direction of reform and opening-up and its goal to achieve all-round modernization. The most important thing both of China-US need to consider is not a win-or-lose outcome, but how to convert the fierce trade war to normal trade disputes and how to obtain a leading position in morals, strategies and tactics in the game between major countries. To this end, methods of balanced thinking need to be adopted for proper handling of five major relationships. We need to understand, tolerate and compromise each other. We need to discuss and negotiate the balanced solutions to the problem. This is the requirement of the law of balance. What is the Profound Changes of the world? What is the essence and reason of the profound changes? How should we deal with such profound changes? How do we view China-US trade disputes in the profound changes of the world. This paper attempts to give a preliminary analysis on these questions. This paper is a special research project of the National Social Science Fund, Research on the joint development of China, the one belt and road initiative and the United Nations sustainable development agenda.

A Dipole Sub-Array With Reduced Mutual Coupling for Large Antenna Array Applications

The use of large array antennas in multiple-input multiple-output (MIMO) exploits diversity and reduces the overall transmission power making it a key enabling technology for 5G. Despite all the benefits, mutual coupling (MC) between elements in these array antennas is a concerning issue as it affects the antenna terminal impedance, reflection coefficients, etc. In this paper, a four-element printed dipole sub-array with reduced MC for S-band has been proposed. A balanced transmission line structure has been designed with two dipole arms on the opposite side of the substrate. Simulated and measured results are in good agreement making the design suitable for large array applications such as phased array radars. The proposed array exhibits good impedance matching with a reflection coefficient of -45 dB and resonating at the center frequency of 2.8 GHz. Moreover, isolation of -20 dB has been achieved for each element in a 2×2 planar array structure using out of band, parasitic elements, and planar shift by distributing the separation between the elements.

Electronically reconfigurable parasitic antenna array for pattern selectivity

Antenna arrays are commonly used to achieve high gains and beam steering, but they require complex feeding networks. For applications demanding moderate antenna gains (≃6 dB) and planar radiating structures, printed Yagi-Uda antennas can offer many advantages, but clearly, they cannot cover the whole azimuth plane. A symmetric structure made of two Yagi-Uda antennas with two active elements, a shared reflector and two directors of variable length is here presented and demonstrated to have switched beams that cover all the azimuth plane. By lengthening the physical lengths of the directors, they turn to act as reflectors: as a result, this antenna system has the ability to switch between broadside, bidirectional end-fire and two opposite end-fire patterns. The feeding is provided by a balanced parallel strip-slot line without the need for a balun section and thus reducing the overall size of the antenna. A modified design is also presented, obtained by adding a reflector board which allows for higher gains and focused radiation reconfigurability in the half-space. Simulated and measured results of both designs are reported showing good agreement. The antenna has a compact size, wideband characteristics and directive pattern reconfigurability.

Productivity Improvement Through Time Study Approach: A Case Study from an Apparel Manufacturing Industry of Pakistan

Standard processing timings play an important role in efficient production management and are measured using work measurement techniques. Time study is a widely used work measurement technique in repetitive manufacturing processes. In present study, time study technique was used to enhance productivity of a garment production line in a work wear manufacturing factory. The factory consisted of 350 sewing machines and was producing work wears including trousers, vests, jackets and coveralls. Stop watch time study – analysis of existing set up – explored the existing time losses in production line caused by unevenness of work, excessive material transportation and higher work-in-process. Improvements were made through: (i) sequence of activities, (ii) tasks reassignment to the work stations and (iii) line balancing at predetermined cycle time. Hourly production charts were maintained at each work station to monitor outputs. The results of machine productivity were compared before and after employing changes. From results, 36% increase in average machine productivity was observed. Hence, it can be concluded that time study is an effective tool for increasing productivity in apparel manufacturing. The added advantages including optimization of material flow, balanced production line and reduced work in process were also achieved. The results of this study are useful for sewing factories making other woven, knitted and home textile products. In addition, football, shoe and gloves manufacturing industry may reef benefits from findings of this study.

UNBALANCED METAMATERIALS APPLIED TO PHASE SHIFTER: DEDICATED DESIGN METHOD AND APPLICATION IN C-BAND

In order to design differential phase shifters (DPS) from metamaterial-based transmission lines, research had a long tradition of using balanced transmission lines which are a particular case of metamaterials, specifically characterized by a simplified equivalent circuit model. This paper presents an innovative way of designing DPS metamaterials by exploiting metamaterial properties more widely, using both balanced and unbalanced cases to obtain a broader set of solutions. These solutions are acquired through the dedicated method this paper expounds, and conceived with the help of a new use of metamaterials. For the sake of ensuring time efficiency and implementation easiness of this design method for industrial purpose, the full wave parametric optimization is reduced to its minimum by exploiting as much as possible in analytic parametric study. This method is illustrated by an application of 180 • DPS on C-Band (5-6 GHz). Three prototypes were fabricated, and the measurements show that the best case of DPS has less than 9 • of phase error over the targeted 20% bandwidth, with a return loss less than −14 dB and insertion losses lower than 1 dB.