Integrated Manufacturing Cell Formation Technology Orienting Multi-product Type and Variant Volume Production

What is pursued by multi-product type and variant volume（MPTVV） production is rapid response and quick switching,so that structure of transferring line in manufacturing system is no longer unalterable.Cell formation（CF） algorithm is the key technology of cellular manufacturing system（CMS）.Currently,CF methods are mainly extended on the idea of group technology（GT） that covers a lot on analysis of resource capability matching and its algorithm.Various constraints are considered,but seldom utilized comprehensively.Aimed to the problem of manufacturing cell（MC） formation under MPTVV production mode,integrated formation technologies for typical MC as group type of cell（GC）,flow type of cell（FC） and inherited cell（IC） are presented based on technical analysis of CF.Oriented to practical production constraints like delivery time,product batch,equipment ability,key machine,key part and machine sharing,etc,an integrated formation model is constructed and internal interrelations of these constraints are analyzed synthetically.Ulteriorly,formation goals of types of MCs and their formation procedures under joint effect of formation constraints and rules are spread.In case study,three highly balanced GC are formed first;then FC formation are implemented based on the same data which indicate good balancing effect of cell load and flow-style production for key tasks;When task is adjusted,a new scheme is constructed on the result of FC configuration by using IC formation method,and more optimal performance of flow-style production is manifested.The proposed comparative study of different type of cells strongly explains the validation of integrated MC formation in support of rapid manufacturing resource transformation under MPTVV production mode.

Deadlock-free Supervisor Design for Robotic Manufacturing Cells With Uncontrollable and Unobservable Events

In this paper,a deadlock prevention policy for robotic manufacturing cells with uncontrollable and unobservable events is proposed based on a Petri net formalism.First,a Petri net for the deadlock control of such systems is defined.Its admissible markings and first-met inadmissible markings(FIMs)are introduced.Next,place invariants are designed via an integer linear program(ILP)to survive all admissible markings and prohibit all FIMs,keeping the underlying system from reaching deadlocks,livelocks,bad markings,and the markings that may evolve into them by firing uncontrollable transitions.ILP also ensures that the obtained deadlock-free supervisor does not observe any unobservable transition.In addition,the supervisor is guaranteed to be admissible and structurally minimal in terms of both control places and added arcs.The condition under which the supervisor is maximally permissive in behavior is given.Finally,experimental results with the proposed method and existing ones are given to show its effectiveness.

Petri net based modeling and analysis for weldingflexible manufacturing cell

Due to the development of advanced manufacturing technology and the introduction of Smart Manufacturing notion in the field of modern industrial production, welding flexible manufacturing using robot technology has become the inevitable developing direction on welding automation. Based on a new intelligent arc welding flexible manufacturing cell (WFMC), its system structure and control policies are studied in this paper. Aiming at the different information flows among every subsystem and central monitoring computer in this WFMC, Petri net theory is introduced into the process of welding manufacturing. A discrete control model of WFMC has been constructed, in which the system's status is regarded as place and the control process is regarded as transition. Moreover, grounded on automation Petri net principle, the judging and utilizing of information obtained from welding sensors are imported into Petri net structure, which extends the traditional Petri net concepts. The control model and policies researched in this paper have established foundation for further intelligent real time control on welding flexible manufacturing cell and system.

Research on Cell Manufacturing Facility Layout Problem Based on Improved NSGA-II

With the rapid development of the individualized demand market,the demand for manufacturing flexibility has increased over time.As a result,a cell manufacturing system suitable for many varieties and small batches has been produced.With the goal of minimizing the area and logistics handling volume,and considering the arrangement order of facilities and channel constraints,a mathematical model was established,and the problem was solved by improved NSGA-II.After non-dominated sorting,traditional NSGA-II will cross-operate the individuals with the best sorting to generate new individuals.Such a selection strategy is extremely easy to fall into the local optimal solution.The improved NSGA-II is to improve the original selection operation,which is to select the first half of the excellent individuals in the non-dominated sorting into the cross operation,and then select the last sorted ones of the remaining individuals into the cross operation,and combine the best and the worst ones into the cross operation.Finally,an example is given to simulate and improve the solution of NSGA-II and NSGA-II.The simulation results indicate that the improved NSGA-II population shows more obvious diversity,it is easier to jump out of the local optimal solution than NSGA-II,and the satisfactory layout scheme of manufacturing cells is obtained.Therefore,it is more effective to use improved NSGA-II to solve the problem of manufacturing cell layout.

Current Developments in the Stable Production of Human Induced Pluripotent Stem Cells

Induced pluripotent stem cells(iPSCs)are considered to be ideal and promising cell sources for various applications such as regenerative medicine and drug screening.However,effective mass production systems for the stable supply of desired numbers of iPSCs are yet to be developed.This review introduces the various approaches that are currently available for stable iPSC production.We start by discussing the limiting factors to be controlled during iPSC culture,such as nutrient supply,waste removal,and oxygen availability.We then introduce recent investigations on iPSC culture systems based on adhesion,suspension,and scaffolds.We also discuss the downstream processes that follow the culture process,such as filling and freezing processes,which limit the production scale due to decreased cell viability during suspension in cryopreservation medium.Finally,we summarize the possibility of the stable mass production of iPSCs and highlight the limitations that remain to be overcome.We suggest that multidisciplinary investigations are essential to understand the different factors that influence cell growth and quality in order to obtain an optimal and stable iPSC mass production system.

Prospects for the therapeutic development of umbilical cord bloodderived mesenchymal stem cells

Umbilical cord blood(UCB)is a primitive and abundant source of mesenchymal stem cells(MSCs).UCB-derived MSCs have a broad and efficient therapeutic capacity to treat various diseases and disorders.Despite the high latent selfrenewal and differentiation capacity of these cells,the safety,efficacy,and yield of MSCs expanded for ex vivo clinical applications remains a concern.However,immunomodulatory effects have emerged in various disease models,exhibiting specific mechanisms of action,such as cell migration and homing,angiogenesis,anti-apoptosis,proliferation,anti-cancer,anti-fibrosis,anti-inflammation and tissue regeneration.Herein,we review the current literature pertaining to the UCB-derived MSC application as potential treatment strategies,and discuss the concerns regarding the safety and mass production issues in future applications.

APPLICATIONS AND MANUFACTURE OF THE MICROSCALE LONG-OPTICAL-PATH ELECTROCHEMICAL CELL WITH A PLUG-IN THIN-LAYER ELECTRODE

The construction and characteristics of a microscale long-optical-path electrochemi- cal cell with a plug-in thin-layer electrode are described.Using ferricyanide as the test species,the thermodynamic parameters of electron transfer processes are determined at car- bon,plantinum,and gold electrodes.

Recent advances of flexible perovskite solar cells

In few years only, the efficiency record of perovskite solar cells（PSCs） has raised quickly from 3.8% to over 22%. This emerging photovoltaic technology has primarily shown its great potential of industrialization. Flexible PSCs are thought to be one of the most priority options for mass production, related to the intrinsic advantage of perovskite thin films which could be deposited by facile solution processes at low temperature. Flexible PSCs have at least four advantages in comparison to the rigid counterpart：（1） it can generate higher power output at lighter weight,（2） it is easily portable,（3） it can be easily attached to architectures or textiles with diverse shapes, and（4） it is compatible with roll-to-roll fabrication in a large scale. In this review, we have summarized recent development of the key materials and technologies applied in flexible PSCs. The key materials including flexible substrates, transparent and conductive electrodes, and interfacial materials; some key technologies about roll-to-roll manufacture, encapsulation technology have been overviewed. Finally, a prospect on possible application directions of flexible PSCs has been discussed.

Mechano-responsive hydrogel for direct stem cell manufacturing to therapy

Bone marrow-derived mesenchymal stem cell(MSC)is one of the most actively studied cell types due to its regenerative potential and immunomodulatory properties.Conventional cell expansion methods using 2D tissue culture plates and 2.5D microcarriers in bioreactors can generate large cell numbers,but they compromise stem cell potency and lack mechanical preconditioning to prepare MSC for physiological loading expected in vivo.To overcome these challenges,in this work,we describe a 3D dynamic hydrogel using magneto-stimulation for direct MSC manufacturing to therapy.With our technology,we found that dynamic mechanical stimulation(DMS)enhanced matrix-integrinβ1 interactions which induced MSCs spreading and proliferation.In addition,DMS could modulate MSC biofunctions including directing MSC differentiation into specific lineages and boosting paracrine activities(e.g.,growth factor secretion)through YAP nuclear localization and FAK-ERK pathway.With our magnetic hydrogel,complex procedures from MSC manufacturing to final clinical use,can be integrated into one single platform,and we believe this‘all-in-one’technology could offer a paradigm shift to existing standards in MSC therapy.

Research on Multi-Agent Based Framework of Reconfigurable Shop Floor Control System

Manufacturing systems are in a dynamically changing e nvironment with uncertainty. Management of complexity, changes and disturbances is one of the key issues of production. The traditional hierarchical control of CIM systems limits the agility and the flexibility of the shop floor control sys tems and makes the reconfiguration and maintenance of shop floor control systems need high cost and much time. So new architectures are required to meet these c hallenges for the shop floor control systems. Recent fundamental research in distributed artificial intelligence and related applied research in intelligent manufacturing systems have shown that the Multi -Agent based system is one of the most promising methods. In a multi-agent man ufacturing system, the agents react to the information acquired from environment and communicate with other agents to co-operate to solve the global problem. I n this paper, a framework of reconfigurable shop floor control system based on m ulti-agent is presented. The concept of dynamic and logical manufacturing cell is proposed to organize manufacturing resources to achieve the ability of re configuration in dynamic shop floor environment. The framework is composed of three levels. First, the level of shop floor comp rises order agent, resource management agent, product management agent and t ask agent. Second, the level of dynamical cells consists of production agents an d control agents. Finally, the resource agents, such as AGV agents and machine a gents, belong to the equipment level. The control architecture in the framework is different from hierarchical control. It is hybrids of hierarchical and hetera rchical control architecture. The Contract Net protocol and its bidding mechanism are suitable and efficient t o implement the dynamic and logical manufacturing cells. Based on the Contract N et Model, dynamic negotiation during the process of forming the dynamic and logi cal manufacturing cells is analyzed in the paper. In this paper the dynamic and logical manufacturing cell is the basis of the r econfiguration of multi-agent systems. It is organized in logical way while the traditional cell based on GT (group technology) is organized in physical way. I n the framework, resource agents are organized according to orders coming to sho p floor, and dismissed when the tasks are finished. Dynamically created cells ca n be overlapped in shop floor so that resource agents may belong to more than on e dynamic and logical manufacturing cells at a time. The order-oriented product ion agents and control agents that are created dynamically exist for the dur ation of the task and are destroyed when the task is completed. They have the li fecycle of creation, execution and destruction. Control agents are the coordinat ors and monitors that are responsible for organizing resource agents and monitor ing disturbances, but they are not strict controllers. They may recruit new reso urce agents into cells when disturbances such as machine breakdown appear. In the paper, the software architecture of shop floor control system based on Multi-Agent is also presented. And the distributed object technology based on C ORBA and KQML language are discussed.

Application of Timed Petri Nets to Analysis and Scheduling of Flexible Manufacturing Cells

In this paper, steady-state behaviors for a large class of flexible manufacturing cells are considered under two types of schedules, i.e., simple schedule and composite schedule. It is shown that each composite schedule can be obtained by composition of simple ones. A systematic approach to modeling and analysis of schedules is proposed cycle times of timed petri net models of schedules are derived. A example of three-machine cell is given.