Transient behavior of serial production lines with Bernoulli machines

The steady-state performance of production systems with unreliable machines has been analyzed extensively during the last 50 years. In contrast, the transient behavior of these systems remains practically unexplored. Transient characteristics, however, may have significant manufacturing implications. Indeed, if, for example, transients are sluggish and the steady state is reached only after a relatively long settling time, the production system may lose some of its throughput, thus leading to a lower efficiency. This paper is devoted to analytical and numerical investigation of the transient behavior of serial production lines with machines having the Bernoulli reliability model. The transients of the states (i.e., the probabilities of buffer occupancy) are described by the Second Largest Eigenvalue (SLE) of the transition matrix of the associated Markov chain. The transients of the outputs (i.e., production rate, PR, and work-in-process, WIP) are characterized by both the SLE and Pre-Exponential Factors (PEF). We study SLE and PEF as functions of machine efficiency, buffer capacity and the number of machines in the system. In addition, we analyze the settling times of PR and WIP and show that the former is often much shorter than the latter. Finally, we investigate production losses due to transients and show that they may be significant in serial lines with relatively large buffers and many machines. To avoid these losses, it is suggested that all buffers initially be half full. For two- and three-machine lines these analyzes are carried out analytically; longer lines are investigated by simulations.     

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.     

Modelling and analysis of split and merge production systems with Bernoulli reliability machines

Many production systems have split and merge operations to increase production capacity and variety, improve product quality, and implement product control and scheduling policies. In this paper, we present analytical methods to model and analyse Bernoulli split and merge production systems with circulate, priority and percentage split/merge policies. The recursive procedures for performance analysis are derived, the convergence of the procedures and uniqueness of the solutions, along with the structural properties, are proved, and the accuracy of the estimation is justified with high precision.     

Lean buffering in serial production lines with non-exponential machines

In this paper, lean buffering (i.e., the smallest level of buffering necessary and sufficient to ensure the desired production rate of a manufacturing system) is analyzed for the case of serial lines with machines having Weibull, gamma, and log-normal distributions of up- and downtime. The results obtained show that: (1) the lean level of buffering is not very sensitive to the type of up- and downtime distributions and depends mainly on their coefficients of variation, CV _up and CV _down ; (2) the lean level of buffering is more sensitive to CV _down than to CV _up but the difference in sensitivities is not too large (typically, within 20%). Based on these observations, an empirical law for calculating the lean level of buffering as a function of machine efficiency, line efficiency, the number of machines in the system, and CV _up and CV _down is introduced. It leads to a reduction of lean buffering by a factor of up to 4, as compared with that calculated using the exponential assumption. It is conjectured that this empirical law holds for any unimodal distribution of up- and downtime, provided that CV _up and CV _down are less than 1. Correspondence to: Semyon M. Meerkov     

Energy-aware feedback control for production scheduling and capacity control

In this paper, we propose an energy-aware feedback control model for production scheduling and capacity control. Specifically, we integrate functions of production scheduling and capacity control, taking into account the costs of energy consumption and machine maintenance varied by production capacity, and the penalty cost imposed by just-in-time production requirements. Continuous control variables are used to adjust the system and the resulting dynamics are modelled. Computational experiments show that interrelated dynamics among these three performance factors are well explained by the proposed controllers, and considerably better energy performance, about 20.0–40.0% improvement, in an energy-aware production compared to a conventional strategy.     

高性能模糊控制裹包机的感应电动机驱动系统的设计与实现

针对接缝式裹包机的交流调速系统控制精度较差的问题,提出了具有模糊控制器的有限周期控制的感应电动机驱动.由于转矩和磁通是由有限周期控制技术调节,能达到极快转矩响应.将模糊控制器应用于速度控制反馈环节中,使该驱动系统具有高自适应能力,且对参数和工作条件改变是非常的不灵敏.     

The mass production and quality control of RPCs for the Daya Bay experiment

Resistive plate chambers will be used in the Daya Bay reactor neutrino experiment to help veto backgrounds created by cosmic-ray muons. The mass production of RPCs began in 2008 and by the end of 2009, 1600 RPCs (3500 m²) had been produced and tested. This paper describes the production and quality control procedures, and quality assurance using cosmic-ray testing.     

基于人机集成的生产过程管理系统研究与开发

针对汽车制造企业生产过程复杂的特点,提出了一种基于人机集成的现场生产过程监控、车间调度和计划的集成管理系统的结构框架和原理,并且开发了一套适合某微型汽车生产企业的生产过程管理系统,阐述了该系统的结构功能和关键技术。针对汽车装配线平衡问题,提出了一种多目标优化方案。该系统在某特大型汽车制造企业得到成功应用,对于提高该企业的生产效率以及降低生产成本起到了重要的作用,并在类似汽车流水线生产企业应用上具有广泛的前景。     

一个高温持久/蠕变测控温及试验管理系统

介绍了采用测控分开形式对近百台五六十年代制造的高温持久/蠕变试验机进行测控温系统改造的工作.改造后的控温系统创造了不同热电偶数量(测控温共偶,1～3支)都可实现对试样温度和梯度的稳定控制,系统具有较强抗外界干扰能力,而且控温过程中对电网无干扰.测量系统测量误差≤±0.1%FS.测控温系统采取单炉闭环控制、30台集中巡回...     

Integrated production planning and quality control for linear production systems under uncertainties of cycle time and finished product quality

This work considers serial production systems with several process steps and a possible quality control at final step. It deals with the problem of optimising planned lead time when the real lead time for each process is stochastic and the finished product quality is uncertain unless it is inspected. Three analytical models are proposed aiming to minimise the expected total cost, which is composed of the inventory and backlogging costs for the finished product and quality costs associated with inspection and non-conformities. These models correspond to three quality control policies: (i) without quality control, (ii) with quality control but without taking into account the inspection duration when optimising the planned lead time and (iii) with quality control and with considering the inspection duration when optimising the planned lead time. Based on the results, it can be highlighted the economic advantage of integrating quality control at the early stage of supply and production planning decisions for some cost parameters conditions. The robustness of the proposed models is also analysed regarding the variance of the probability distributions of the lead times.     

可编程序控制器的原理及其在火焰切割机数控系统中的应用

本文介绍了可编程序控制的工作原理,重点放在西门子公司生产的S5-130W上。对火焰切割机数控系统中使用S5-130W所构成的控制系统的软、硬件结构进行较为详细的讨论,并且指出了应用过程中所要注意的事项。     

基于PLC的火腿肠装箱机自动控制系统的设计与实现

火腿肠装箱机是火腿肠自动生产线的关键设备,为了解决火腿肠加工企业火腿肠包装中的问题,详细介绍了基于PLC技术的火腿肠装箱机自动控制系统的设计与实现.     

电容器盖板自动预压机及其控制系统设计

针对电容器盖板预压工序存在自动化程度低、劳动强度大等不足,设计了电容器盖板自动预压机及其控制系统.对电容器盖板自动预压机的机械系统进行了详细设计,包括铝壳放置转盘组件、电容器定位组件、盖板预压组件、电容器推出组件、电容器接收组件等;采用可编程序逻辑控制器(programmable logic controller,PLC)作为控制系统的主控制器,实现多种规格电容器盖板的自动预压;依据电容器高度的不同,通过图形操作终端(graphic operating terminal,GOT)设置和调整生产参数.该设备已投入实际生产使用,运行结果表明:整机性能稳定,实际运行状况良好,满足了生产线高柔性化、高效率、高质量的自动化加工要求.     

Joint production and quality control of unreliable batch manufacturing systems with rectifying inspection

Production control policy and economic sampling plan design problems have been studied separately in previous research. This paper considers a joint production control policy and economic single sampling plan design for an unreliable batch manufacturing system. The production is controlled by a modified hedging point policy which consists of building and maintaining a safety stock of finished product to avoid shortages during corrective maintenance. The main objective of this paper is to determine simultaneously the economic production quantity, the optimal safety stock level and the economic sampling plan design which minimise the expected overall cost. A stochastic mathematical model is developed and solved using a simulation optimisation approach based on the response surface methodology. Simulation is used to imitate the complex dynamic and stochastic behaviour of processes as in the real-life industrial systems. The obtained results show clearly strong interactions between production quantity, inventory state and sampling plan design which confirm the necessity of jointly considering production and quality control parameters in an integrated model. Moreover, it is shown a significant impact of production system reliability on the economic sampling plan design and therefore on the quality of finished product delivered to consumers. Numerical example and sensitivity analyses are presented for illustrative purposes.     

基于不同控制网络的制氧管控中心的开发和应用

鲍德气体通过网络设备实现了制氧生产的管控一体化,实现了企业从经验管理向科学管理的发展。介绍控制系统设备配置等现状,阐述建立制氧管控中心的设计方案,分析管控中心建立过程中网络抗干扰、数据交换、常规仪表改造等关键问题的解决方法。     

基于PLC变频调速的包装印刷位置控制系统的实现

以快速、高精度跟踪为主要目标的位置伺服系统是广泛应用于高精度位置控制的主要控制方式之一,其驱动信号为代表位置命令的脉冲信号。介绍了以全数字式交流伺服MINAS系列为执行结构,利用S7-200CPU214/DC的高速计数器与PTO集成脉冲输出功能实现对包装印刷位置伺服系统驱动的方案和软件的开发。     

Production control policy for tandem workstations with constant service times and queue time constraints

Queue time constraints are commonly imposed to ensure product quality in contemporary production systems. We study the performance of two single stations with deterministic service times and a predetermined time window in between, where both stations suffer time-based pre-emptive breakdowns. To improve productivity, achieving higher capacity and lower rework rate are the two main objectives. While higher capacity requires a higher work-in-process (WIP)-level threshold, a lower rework rate requires a smaller one. To quantify the trade-off between the two objectives, an analytical model is derived. The model is then used to derive the WIP-level threshold control policy for a time-constrained system. We also show that system capacity diminishes with the decrease in WIP-level thresholds.     

基于PC控制的法国克莱梅低温箱故障分析与排除

法国克莱梅低温箱采用了工控机来控制系统,介绍了克莱梅低温箱的故障分析与排除.     

Intelligent decision support system for the adaptive control of a flexible manufacturing system with machine and tool flexibility

This paper describes an intelligent decision support system (IDSS) for real time control of a flexible manufacturing system (FMS). The controller is capable of classifying symptoms in developing the control policies on FMSs with flexibility in operation assignment and scheduling of multi-purpose machining centres which have different tools with their own efficiency. The proposed system is implemented by coupling of rule-based IDSS, simulation block and centralised simulation optimiser for elicitation of shop floor control knowledge. This posteriori adaptive controller uses a new bilateral mechanism in simulation optimiser block for offline training of IDSS based on multi-performance criteria simulation optimisation. The proposed intelligent controller receives online information of the FMS current state and trigger appropriate control rule within real-time simulation data exchange. Finally the FMS intelligent controller is validated by a benchmark test problem. Application of this adaptive controller showed that it could be an effective approach for real time control of various flexible manufacturing systems.     

An optimal batch size for an imperfect production system with quality assurance and rework

We consider a manufacturing system which receives raw material from a supplier, processes it, and delivers it to the customer periodically. The system considered is imperfect and produces defectives at a constant rate. The finished product can only be delivered if the whole lot is quality-certified. Hence, defectives have to be reworked, and the whole lot quality-checked within the cycle. Three different scenarios are considered, viz. (a) a single lot of raw material for multiple lot of finished product and delivery of the product in multiple instalments, (b) a single lot of raw material for a multiple lot of finished product and delivery of the product in a single instalment, and (c) lot-for-lot and delivery of finished product in single instalment. A total cost equation is developed for each model, and the optimal ordering quantities are evaluated. The results found are encouraging and quite simple to use for practical purposes.