Serial Lines Research Articles

Taking a Look at Capacitive Power Conversion [White Hot

Recently, I wrote about the workshops and presentations at APEC 2017 that talked about the challenges of magnetics in high-frequency power conversion. Those challenges include losses at high frequency, a lack of good data and models on losses in magnetic materials and devices, and lack of standardization of data from manufacturers. But there were also two other presentations that got me thinking in an entirely different direction: capacitive power conversion. By capacitive power conversion, I generally mean the use of “charge pump” techniques. For example, I am sure many of us have used the charge pump in RS-232 serial line driver ICs to convert +12 Vdc to –12 Vdc. Or maybe we have used a simple charge pump to create a +12 V or +15 Vdc from a +5 Vdc rail to power some small amount of analog circuitry.

Choosing the system configuration for high-volume manufacturing

When designing a new large manufacturing system with high throughput, the corporation should weigh several factors: the capital investment cost, the system’s responsiveness to future varying market demand, the production losses due to disruptive events, and the product quality. These performance metrics depend heavily on the system configuration. In this paper, typical configurations of large-volume manufacturing systems for mechanical products are compared from cost, responsiveness and product quality perspectives. In addition to traditional serial lines and pure parallel systems, we also discuss two practical configurations – parallel serial lines, and reconfigurable manufacturing systems. The results offer managerial insights for selecting the system configuration that creates the maximum economic value over the lifetime of the system, and fits the corporation needs and culture.

Transient Performance Analysis of Closed Production Lines With Bernoulli Machines, Finite Buffers, and Carriers

In many manufacturing systems, each piece of intermediate product is attached to a dedicated carrier (e.g., pallet, skid, fixture, etc.) throughout the entire process for material handling and/or transportation purposes. Once a part finishes all processing steps, the associated carrier will be removed and returned to the front of the production process to pick up new incoming parts. We referred to production systems operating in such manner as “closed.” In the current literature, available results on closed production systems are very limited. In this paper, we study transient performance of closed serial lines with machines that operate according to the Bernoulli reliability model. Specifically, exact mathematical model for the system considered is derived based on Markov analysis. Then, formulas for calculating the system's performance measures during transients are obtained based on the model. An approximation method is proposed to estimate a closed Bernoulli line's performance in completing a finite production run. Finally, properties of finite production run-based closed Bernoulli lines during transient are investigated.

Reducing energy consumption in serial production lines with Bernoulli reliability machines

This paper is devoted to developing an integrated model to minimise energy consumption while maintaining desired productivity in Bernoulli serial lines with unreliable machines and finite buffers. For small systems, such as three- and four-machine lines with small buffers, exact analysis to optimally allocate production capacity is introduced. For medium size systems (e.g. three- and four-machine lines with larger buffers, or five-machine lines with small buffers), an aggregation procedure to evaluate line production rate is introduced. Using it, optimal allocation of machine efficiency is searched to minimise energy consumption. Insights and allocation principles are obtained through the analyses. Finally, for larger systems, a fast and accurate heuristic algorithm is presented and validated through extensive numerical experiments to obtain optimal allocation of production capacity to minimise energy consumption while maintaining desired productivity.

Performance Evaluation of Bernoulli Serial Lines with Waiting Time Constraints

Manufacturing systems with waiting time constraints are widely observed in battery, automotive, semiconductor, food and many other industries. Under such requirements, the residence time of a part in a buffer is constrained by a given time limit and the part exceeding the limit is subject to quality inspection and could be scrapped with a certain probability. To evaluate the performance of such systems, in this paper, we study Bernoulli serial lines with waiting time limits. For two-machine lines, analytical formulas are derived to predict the system performance in the steady state. In case of longer lines, direct analysis is intractable, thus an iterative aggregation procedure is presented. Based on extensive numerical experiments, the convergent results of the procedure can be obtained and high precision in performance estimation is achieved.

Multi-job production systems: definition, problems, and product-mix performance portrait of serial lines

This paper pursues two goals: (a) Define a class of widely used in practice flexible manufacturing systems, referred to as Multi-Job Production (MJP) and formulate industrially motivated problems related to their performance. (b) Provide initial results concerning some of these problems pertaining to analysis of the throughput and bottlenecks of MJP serial lines as functions of the product-mix. In MJP systems, all job-types are processed by the same sequence of manufacturing operations, but with different processing time at some or all machines. To analyse MJP with unreliable machines, we introduce the work-based model of production systems, which is insensitive to whether single- or multi-job manufacturing takes place. Based on this model, we investigate the performance of MJP lines as a function of the product-mix. We show, in particular, that for the so-called conflicting jobs there exists a range of product-mixes, wherein the throughput of MJP is larger than that of any constituent job-type manufactured in a single-job regime. To characterise the global behaviour of MJP lines, we introduce the Product-Mix Performance Portrait, which represents the system properties for all product-mixes and which can be used for operations management. Finally, we report the results of an application at an automotive assembly plant.

A mathematical model for productivity rate of APSL segmented on sections with buffers of limited capacity

Automated production lines with high productivity are represented the complex and expensive systems based on mechanical, electric and electronic units, while predicting the efficiency of the automated lines is an important analytical task. Calculating the productivity rate of the automated production serial line (APSL) segmented on sections with embedded buffers of limited capacity is a complex and crucial problem for manufacturers. The productivity rate of APSL with balanced technological processes depends on the reliability of mechanism, workstations, transport and other units. Balancing the machining time leads to an increase in the number of workstations and in productivity rate of APSL. It also leads to an increase in the failure rates and hence to deceasing in the productivity rate of the production line. Solution for enhancing productivity is presented in terms of segmenting of APSL into sections with embedded buffers. This paper represents an analytical solution for the productivity rate of APSL segmented on sections with embedded buffers of limited capacity. The mathematical model for the productivity rate of APSL is derived as a function of the technological parameters, the capacity of the buffers and the number of stations and sections with different failure rates and cycle times.

Standalone closed-form formula for the throughput rate of asynchronous normally distributed serial flow lines

Flexible flow lines use flexible entities to generate multiple product variants using the same serial routing. Evaluative analytical models for the throughput rate of asynchronous serial flow lines were mainly developed for the Markovian case where processing times, arrival rates, failure rates and setup times follow deterministic, exponential or phase-type distributions. Models for non-Markovian processes are non-standalone and were obtained by extending the exponential case. This limits the suitability of existing models for real-world human-dependent flow lines, which are typically represented by a normal distribution. We exploit data mining and simulation modelling to derive a standalone closed-form formula for the throughput rate of normally distributed asynchronous human-dependent serial flow lines. Our formula gave steady results that are more accurate than those obtained with existing models across a wide range of discrete data sets.

Serial Interface through Stream Protocol on EPICS Platform for Distributed Control and Monitoring

Remote operation of any equipment or device is implemented in distributed systems in order to control and proper monitoring of process values. For such remote operations, Experimental Physics and Industrial Control System (EPICS) is used as one of the important software tool for control and monitoring of a wide range of scientific parameters. A hardware interface is developed for implementation of EPICS software so that different equipment such as data converters, power supplies, pump controllers etc. could be remotely operated through stream protocol. EPICS base was setup on windows as well as Linux operating system for control and monitoring while EPICS modules such as asyn and stream device were used to interface the equipment with standard RS-232/RS-485 protocol. Stream Device protocol communicates with the serial line with an interface to asyn drivers. Graphical user interface and alarm handling were implemented with Motif Editor and Display Manager (MEDM) and Alarm Handler (ALH) command line channel access utility tools. This paper will describe the developed application which was tested with different equipment and devices serially interfaced to the PCs on a distributed network.

Flexible Serial Lines With Setups: Analysis, Improvement, and Application

Setup times commonly exist in many flexible manufacturing lines to adjust tools and carry out safety and quality check during product changeovers. In this paper, a Markov chain model is introduced to study flexible manufacturing lines with setups. An aggregation-based recursive procedure is introduced to evaluate system performance. The convergence of the procedure is proved analytically and the accuracy is justified numerically. Using such a method, the impact of setups is analyzed and the effectiveness of downtime and setup time reduction is investigated. Indicators are derived to identify the setup bottlenecks with respect to machine and product type, whose setup time reduction can lead to the largest improvement in line production rate. Finally, an application study at a furniture manufacturing plant is introduced.

The impact of maintainability on the manufacturing system architecture

The rapid development of big data technologies can improve the maintainability of machines and equipment in manufacturing systems, which could impact the selection of the optimal system architecture. In this paper, two typical architectures for large manufacturing systems − serial lines in parallel and reconfigurable manufacturing systems − are considered, and their productivities are compared. A decision locus is calculated that divides the configuration space into two areas; in each area, one of the architectures is the preferred one. It is also investigated how the locus is affected by different parameters, such as system size, buffer capacity and machine or gantry maintainability. The analysis provides valuable managerial insights for designing the architecture of large manufacturing systems.

Level workforce planning for multistage transfer lines

AbstractIn this article, we define two different workforce leveling objectives for serial transfer lines. Each job is to be processed on each transfer station for c time periods (e.g., hours). We assume that the number of workers needed to complete each operation of a job in precisely c periods is given. Jobs transfer forward synchronously after every production cycle (i.e., c periods). We study two leveling objectives: maximin workforce size () and min range (R). Leveling objectives produce schedules where the cumulative number of workers needed in all stations of a transfer line does not experience dramatic changes from one production cycle to the next. For and a two‐station system, we develop a fast polynomial algorithm. The range problem is known to be NP‐complete. For the two‐station system, we develop a very fast optimal algorithm that uses a tight lower bound and an efficient procedure for finding complementary Hamiltonian cycles in bipartite graphs. Via a computational experiment, we demonstrate that range schedules are superior because not only do they limit the workforce fluctuations from one production cycle to the next, but they also do so with a minor increase in the total workforce size. We extend our results to the m‐station system and develop heuristic algorithms. We find that these heuristics work poorly for min range (R), which indicates that special structural properties of the m‐station problem need to be identified before we can develop efficient algorithms. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 577–590, 2016

Monolithic 56 Gb/s silicon photonic pulse-amplitude modulation transmitter

Silicon photonics promises to address the challenges for next-generation short-reach optical interconnects. Growing bandwidth demand in hyper-scale data centers and high-performance computing motivates the development of faster and more-efficient silicon photonics links. While it is challenging to raise the serial line rate, further scaling of the data rate can be realized by, for example, increasing the number of parallel fibers, increasing the number of wavelengths per fiber, and using multi-level pulse-amplitude modulation (PAM). Among these approaches, PAM has a unique advantage because it does not require extra lasers or a costly overhaul of optical fiber cablings within the existing infrastructure. Here, we demonstrate the first fully monolithically integrated silicon photonic four-level PAM (PAM-4) transmitter operating at 56 Gb/s and demonstrate error-free transmission (bit-error-rate < 10$^{-12}$) up to 50 Gb/s without forward error correction. The superior PAM-4 waveform is enabled by optimization of silicon traveling wave modulators and monolithic integration of the CMOS driver circuits. Our results show that monolithic silicon photonics technology is a promising platform for future ultrahigh data rate optical interconnects.

Optimally configuring a two-stage serial line supply chain under the guaranteed service model

Design-and-development buyers sourcing new supply chains and strategic sourcing analysts making outsourcing decisions for existing supply chains are in different organizations but share a common problem. Both determine whether an existing part should be replaced. Relative to the existing part, new candidates could be cheaper with longer leadtime, or more expensive with shorter leadtime. Furthermore, a longer leadtime part could be buffered with inventory and this could be cheaper than paying more for a shorter leadtime part.To derive analytical insights into the nature of this problem, we restrict our scope to a two-stage serial line supply chain. This restriction is consistent with sourcing analysts that consider sourcing a single part from different vendors and different transportation alternatives. The resulting two-stage supply chain configuration model jointly determines the chosen option and inventory stocking level at each stage to minimize cost of goods sold, pipeline stock cost and safety stock cost.We prove it is preferable to synchronize the supply chain by employing the same type of option, either low cost long leadtime or high cost short leadtime, at both stages. We prove that the selection threshold for high cost short lead time options is lowest at just the downstream stage, highest for just the upstream stage, and between these extremes if such a candidate is selected for both stages. If a part’s cost-time relationship follows a functional form, we establish conditions when it is optimal to choose the lowest cost, longest leadtime, option available.

The effect of work content imbalance and its interaction with scheduling method on sequential flow line performance

Uneven workflow in serial flow lines is common when job work content varies. Unfortunately, work content imbalance between stations or between jobs degrades system performance. The effect of this imbalance can be mitigated by proper job sequencing. In this paper, we uncouple the influence of station-to-station and job-to-job imbalance within a set of jobs, introducing metrics to quantify the degree of imbalance, and determine their impact on line performance. We then examine the sensitivity of several scheduling methods at different problem scales and processing time variance levels, and compare the sensitivity to process time stability radii. Within the case studies explored, we determine that greater station imbalance can degrade solution quality regardless of problem scale and variance level. Greater job imbalance can either improve or diminish solution quality (i.e. relative performance from a given scheduling method), but less than station imbalance. Scheduling methods that sequence jobs based on the sums of processing times, e.g. SPT, can benefit from greater station imbalance. Scheduling methods that sequence jobs based on idle time between stations, e.g. the state-space heuristic, are more sensitive to station imbalance, but can also benefit from job imbalance. Finally, we conclude that job sequence has a greater impact on solution quality than stability radii.

Performance Analysis of Assembly Systems With Bernoulli Machines and Finite Buffers During Transients

Serial lines and assembly systems are two of the most fundamental production system structures used in practical manufacturing environments. While serial lines have been studied extensively in production systems literature and practice, assembly systems have received much less attention. Among existing results on assembly systems, most are focused on steady state performance evaluation, system properties, and improvement. On the other hand, transient behavior of such systems remains largely unexplored. In the framework of assembly systems with Bernoulli machines and finite buffers, this paper develops a mathematical model for transient analysis and derives closed-form formulas to calculate the real-time production rate, consumption rates, work-in-process, and probabilities of machine starvation and blockage, during transients. Then, an improved computationally efficient algorithm for transient performance evaluation in Bernoulli serial lines is proposed. Based on the improved algorithm, an effective and efficient method for transient performance evaluation in Bernoulli assembly systems is derived. Finally, the method is extended to complex assembly system structures.

Production Lead Time in Serial Lines: Evaluation, Analysis, and Control

Production Lead Time $\mbi (LT)$ is the average time a part spends in the system, being processed or waiting for processing. In systems with unlimited buffers, $\mbi LT$ may be orders of magnitude larger than the total processing time, leading to serious economic and quality problems. At present, no systematic analytical methods for evaluation, analysis, and control of $\mbi LT$ in systems with machines having up- and downtime characterized by continuous random variables are available. This paper is intended to develop such methods. Specifically, we address synchronous serial lines with exponential machines and derive formulas for $\mbi LT$ as a function of machine parameters and raw material release rate. Using these formulas, we develop methods for open- and closed-loop raw material release, which result in the desired $\mbi LT$ . For asynchronous exponential lines, we provide an upper bound on $LT$ . For non-exponential lines (e.g., Weibull, gamma, and log-normal), we offer an empirical formula for $\mbi LT$ as an affine function of the coefficient of variation. The results reported in this paper enable a new paradigm for production systems management, namely: manage a production system so that the desired $\mbi LT$ is ensured, while the throughput is maximized.

Triple‐band impedance transformers using equal‐length serial transmission lines

A new formulation of the fundamental load impedance circuit in the z -plane is employed to study transformers. The design employs prototypes of transfer function, parametric modelling techniques, and optimisation methods; a model describing multisection transmission-line transformers is proposed to match load impedance for use in wireless and mobile communication applications. Configuration of the transformer consists of multisection serial transmission lines. This transformer was designed on a PCB FR4 substrate featuring a permittivity of 4.4, a loss tangent of 0.0245, and a thickness of 1.6 mm. Microstrip line circuits were fabricated to verify the feasibility of the technique. The simulation and measurement results show that real and complex load impedances can be matched simultaneously at three different frequency bands. The characteristic impedance values of the transmission lines synthesising the transformers were adjusted according to the autoregressive process by using optimisation algorithms. The experimental results are in agreement with theoretical values.

Improving energy efficiency in Bernoulli serial lines: an integrated model

In this paper, we present an integrated model of both productivity and energy consumptions in serial production lines with two machines. Bernoulli reliability is assumed for both machines and the capacity of the buffer is finite. The energy consumption of each machine includes the energy required to set up the machine until it is ready for processing, and the additional energy needed to carry out the processing operation to make the product. The former is typically fixed for a specific manufacturing process, while the latter is proportional to the processing rate. The objective of the model is to minimise energy consumption, while maintaining the desired production rate. Specifically, analytical investigation has been carried out to discover the conditions that energy consumption can be minimised with and without the constraints of workforce or machine processing capability. Optimal allocations of them under different scenarios have been derived. Insights for reducing energy consumption while still ensuring desired productivity have been obtained.

The impact of corporate culture on manufacturing system design

The work-culture of an industrial firm has a profound impact on the selection of the right production system configuration when cost, throughput, and maintenance capability are weighted in the analysis. We present a novel mathematical analysis that computes the optimal system configuration that fits the culture at the workplace. The analysis is based on the extension of k-out-of-n systems in reliability theory to multistage manufacturing systems, and yields a locus that divides the configuration space into two architectures: serial lines in parallel, and RMS. The analysis clarifies why Japanese manufacturing system design practice is different than the system configurations in U.S. factories.