智能制造系统简介

The Intelligent Manufacturing Systems

[Abstract] The current trend of the final product quality increasing is affected by time analysis of the entire manufacturing process. The primary requirement of manufacturing is to produce as many products as soon as possible, at the lowest possible cost, but of course with the highest quality. Such requirements may be satisfied only if all the elements entering and affecting the production cycle are in a fully functional condition. These elements consist of sensory equipment and intelligent control elements that are essential for building intelligent manufacturing systems. Intelligent manufacturing system itself should be a system that can flexibly respond to changes in entering and exiting the process in interaction with the surroundings.

[Keywords] Intelligent manufacturing systems, manufacturing process, control system

1 INTRODUCTION

The industrial intelligence is still forwarding. Today we are not talking only about using of IT, classical automated instruments. But when we are talking about flexible intelligent manufacturing systems it is effective to talk also about possible using of new generation intelligent manufacturing systems. This new generation of manufacturing systems are also called intelligent manufacturing systems (IMS). All IMS subsystems are including parts of so called machine intelligence (sensor equipment). Using of given systems with combination of machineintelligence will lead to the complete labor remove from the manufacturing system. Basics which are needed for realization of machine intelligence in manufacturing systems is so called monitoring, which is able to monitor an internal stay of the system and also changing conditions coming from environment. Monitoring systems are using sensors which are located at some proper place of the system, usually such place is the tool stand, machine or some manipulating device. Sensors are identifying parameters, which are then used as input data of control system. Following to these data is realized some, technological, manipulating or other helping process.^[1]

The automated production systems are part of the machine production. Base of the complex automatic production is automation of technological process control, automatic transport, manipulation, feeding, workpiece and tool exchange.

As the industrial production develops, the new generation production systems – intelligent production systems – are developed as well. These systems are equipped with artificial intelligence parts and intelligent control. On the present, new solutions of artificial intelligence implementation into machine production are searched. Main requirements in installing of intelligent production systems are: shortening of running production times,higher production productivity, economic expediency,elimination of worker hand intervention. ^[2]

The production strategy focused to time requires the change from traditional functional production structure to a production used flexible manufacturing systems.

Production by flexible manufacturing systems (FMS) is the most important manufacturing philosophy in the last years. This philosophy is based on the following similarities:

• Similarity of manufactured parts.

• Similarity of process plans.

Recognition of the similarity of manufactured parts allows to assort them to the groups by machines required for its manufacturing. By manufacturing of a single group of parts economical benefit near to mass production can be achieved.^[3]

2. USE OF CAX SYSTEMS IN THE INTELLIGENT MANUFACTURING

CA systems are computer systems that are intended to support of activities at all stages of manufacturing – from development and design of component, production planning to production and assembly, storage and expedition. Central production planning/manufacturing systems rely on centralized communication, are rigid, lack scalability and robustness, and have a high cost of integration. Mass Production Systems place emphasis on the reduction of products’ costs and full utilization of plant capacity. This manufacturing approach resulted in inflexible plants, associated with work in process and finished goods inventories.

Computer-Aided Design (CAD)/ Computer Aided Manufacturing (CAM) systems integrate different tools (e.g., e-mail, multimedia, 3D CAD geometry viewer) in a distributed multimedia designing environment through the Internet (e.g.). In CAD, the computers are used in the design and analysis of products and processes. In CAM, the computers are used directly to control and monitor the machines/ processes in real time or offline to support manufacturing operations (e.g., process planning).

Computer integrated manufacturing (CIM) systems have been used to integrate different areas within manufacturing enterprises. They use a graphical user interface within a programming environment and incorporate multimedia packages to facilitate the dissemination of product information (e.g.)

3. THE REQUIREMENTS TO INTELLIGENT MANUFACTURING SYSTEM

The automation of the intelligent manufacturing process can be run in term of the manufacturing profile, material flow and information flow. These basic elements of the manufacturing process are usually automated together in praxis. The task of the intelligent manufacturing process control is to provide the process running in the status of dynamical stability and the replacement in the equilibrium status on the same or acceptable standard by the deviation of the equilibrium status. It is necessary to control and direct the main manufacturing processes that have the required functions. It could be to run more hard manufacturing processes together and also individually in the manufacturing process and all these processes could be to control by specific method. This method is named as the manufacturing process control.

The process control is characteristic as the process organization in system that provides the achievement of the required final state. But it is necessary to know its output for the manufacturing process control in the relatively closed system that it could be to influence the inputs back, to eliminate the ineligible influences of the environment, to reorganize the system internal structure so that will be to achieve the required final state. The necessary element of control system is the feedback.

The utilization of this information for the manufacturing process control could be only then if it is known the noted model of system behavior by means of that it is possible to create the control algorithm and technical system for its realization by defined aim. The required final state has to be real, achievable, the algorithm realizable and the information provision comfortable.

3.1 The manufacturing process control

It is needed to know the answers to three basic questions for the right control system realization. Those are the questions:

a ) what has to be controlled?

In this case it is necessary to define the mathematical models of controlled system by physical basis and identification. At the same time it is required to analyze the manufacturing process in term of the operative motion sequence. Also it is necessary to know the character of manufacturing object before the definition of automated control of the manufacturing process. At once also to analyse the manufacturing process in term of several in sequence connected operative motions. The analyze of manufacturing process and the dividing into partial operations are the important steps. The basic element of the manufacturing process is the operative motion. The operative motion may be defined as the individual part of the operative action by the existing regulation.

b ) what shall we to use for control?

In this case is necessary to choose the right devices of automatic control, the type of energy in the automated manufacturing process. The devices of the automatic control is the group of tools, devices, instruments. Knowledge by these it could be realized the practical control of the manufacturing process type. The devices of the automatic control are in general all technical devices, these could enable to achieve, transfer, save, process and utilize the information and also all helpful devices, and these could enable the activity of those named technical devices. On the ground of limpidity is possible to divide the technical devices into several groups by individual aspects these are definitive for the existing view. The technical devices of automation are possible to divide by the next criteria:

• by the relation to information,

• by the type of the signal energy,

• by the type of information signal,

• by the function.

c ) what way shall we choose for control?

The manufacturing process control is often the integral member of the manufacturing process automation. The control is understood as the technical advance by that the machines and devices in the limited system are influenced in its physical and technical values in terms of required method by the valid regularity. The theory of control or the theory of the automatic control is engaged in the technological meaning of control. The theory of automatic control is the theory that checks the principles of control system functioning and designing.[4]

The manufacturing process is created with more quantity of elements, operations and motions. It is existed the more quantity of interacted connections. The control system that is used in the manufacturing process has the hierarchical structure. The hierarchical structure is the one of the manufacturing process base feature. It is necessary to give one’s time to the control of the individual motions and operations and also to interaction cooperation and communication between them and with the environment by control realization. It is used more method, systemic technologies and programming instruments.

For better understanding to term “intelligent” manufacturing systems, is the most suitable to compare its behavior with the classical (“non intelligent”) automated flexible manufacturing system.

The automated manufacturing system is today known as manufacturing device with various levels of automation of operating and nonoperational activities and with various levels of subsystems integration(technological, supervisory, transportation, manipulating, controlling):

• technological (set of technological workstations)

• transportation and manipulating (is realized by industrial robots, manipulators and transporters) •supervisory (is included to system if machines in system do not have own supervisory devices)

• controlling (there are dominating own controlling systems of all devices) [2]

Using of intelligent production systems is conditioned by efficiency of all subsystems, which are contained in given system. Subsystems are developed with automatic manufacturing systems, in order to save the system parameters.

Automatic manufacturing systems what is designed to repetitive production, where is demanded big rate of flexibility, are called flexible manufacturing systems. To category of automated manufacturing systems (flexible manufacturing systems) are included one or more technological workstations, at which are all inputs and material automated. Basic classification of automated manufacturing systems takes into the account also the number of the machines in the system as well as flexibility of the production.

According to this classification we distinguish three basic types of automated manufacturing systems: [5]

• Flexible manufacturing cell – up to maximum three of the machine tools; it’s characterized by highest level of flexibility.

•Flexible manufacturing line – is characterized by the lowest level of flexibility; range of goods is narrow and being produced in large batches.

•Flexible manufacturing system – minimum three machines and more; is characterized by lower level of flexibility.

The intelligent manufacturing system presents system  witch contained capability of adaptation to unexpected  changes, i.e. assortment changes, market requirements,  technology changes, social needs etc.

However, intelligence of these systems is frequently  understood as control of the software product, and not as  implementation of modern technologies of machine  artificial intelligence.

Intelligent production systems consist of subsystems like  automatic production systems (technological, supervisory,  transportation, manipulating). Subsystems have to be  equipped with aids, which give to subsystems specific  level of intelligence. It is possible to consider it as higher  phase of flexible production systems. [6]

The intelligent manufacturing systems consist of :Fig. 1

• intelligent design,

• intelligent operation,

• intelligent control,

• intelligent planning

• intelligent maintenance.

4. THE INTELIGENCE ENHANCEMENT FOR THE MECHANICAL PERIPHERY

Monitoring of all actions inside the production process but  also in its environment is aimed at increase of this system  reliability and failure prevention of the system itself or  avoidance of defective products. There are several  possibilities how to intelligence of production system can  bee enhanced.

In term of automation assembly is the most complicated  operation. Sequences like correct grip, orientation and  positioning of the component entering the assembly system  in disordered condition (e.g. loose in a container) are very  easy to realize by a human. In term of automation however  these seemingly simple acts represent one of the most  complicated problems. Usually we try to keep aloof from  such acts in the automated assembly process so that  individual components enter the assembly system already  oriented and in a defined place by means of various feeders,  tanks or pallets.

In case the automated assembly system is entered by individual components which are unpositioned and non-oriented an intense cooperation between the sensor subsystem and various intelligent mechanical peripheries is  necessary. Various types of sensors (contact, contactless,  pressure, sensors of strength and moments, CCD cameras  and others) are used dependent on specific demands of the  specific application. Simultaneous combined use of various  sensor types affords solution opportunities also of very  complicated monitoring tasks. Individual sensor types can  differ also in their output signals. Some sensors have only  simple binary output signals, others can have a more  complicated output signal consisting of several simple  binary signals (e.g. sensor differentiating colours) and others  can provide an analogue signal (e.g. rheostatic  thermometer). All these signals must be processed and  correctly evaluated by the control system because only on  the basis of this information it can correctly respond to the  actual state of the production system of its individual  subsystems as well as the actual state of the technological  process.

One of the application areas of monitoring systems is the  area of robotized assembly. Equipping of assembly systems  by sensors is one of the basic levels of increasing of  automation and machine intelligence. Sensory systems  provide scanning and monitoring of various functions of  assembly process, assembly technology, properties of  assembly objects, mounted parts and properties of  environment. Realization of monitoring functions provides  suitable sensor sorts, whereupon the supervisory systems  provide the control interventions. Sensors are the basic  devices for capturing of information and their  transformation. The present monitoring systems have  reserved structures which are realized according to  application or purpose.[7]

Selected sensor or sensory systems (monitoring systems)  must meet technical, economic and operative indicts.  Factors, which affect their selection are multiple and  multilevel. Center of the sensor application is mostly in  robotized assembly, where the sensory systems enable to  assembly (so called intelligent robots) and others technical  elements to identify and monitor workspace and system  environment with building elements. In robotized assembly  the ideal event occurs when PR can recognize, place and  grab random oriented object.

Sensory equipment applied in assembly systems use three  basic groups:

• tactile sensors,

• proximity sensors,

• visual sensors.

Development of the new kinds of sensors takes place in all  three groups. Classification of the most frequently used  kinds of sensors is on figure 4.

Tactile sensors are used in case, that technical, realization  instruments, mostly assembly robots, are in direct contact  with object of assembly.Important are especially sensors  which enable control of the object presence, identification of  grasp force, monitoring of the starting position of assembly  tools, let us say other functions. With tactile sensors are  equipped tentacles, position table, transporting units, other  units and devices. For recognizing of the orientation, kind of  objects, detection of edges are used visual sensors of various kinds.

5. CHALLENGES AND TRENDS

The today challenges and trends in field of the new  generation manufacturing systems research are very clearly  defined at [8]

An extensive survey on manufacturing systems allowed the  identification of the main current trends for manufacturing  systems, which can be summarized as follows:

• specialization, characterized by an extensive focus on core competences ;

• outsourcing ;

• transition from vertical to horizontal structures (e.g., concerning management systems), from highly centralized to decentralized structures (e.g., where an individual element, unit or subunit is enhanced with decision making/ intelligence capabilities);

• evolution towards self-properties or sufficiency (e.g., self-adaptation) which generally occur at low levels. Manufacturing systems with these characteristics have a high level of integration, are easy upgradable, evolvable and adaptable (e.g., to new market conditions;

• the development of technologies and applications to support all the requirements of current distributed manufacturing systems;

• competitiveness: the enterprises should remain competitive, e.g., in terms of costs (e.g., lifecycle costs, investments) vs. payoffs; adequate equipments and machines (e.g., sensors) adequate to new manufacturing paradigms; sustainability (e.g., to consider environmental concerns into design);

• technology, equipment and manufacturing systems’selection (e.g., to evaluate various systems  configurations based on life-cycle economics,  quality, system reliability);

•  integration of humans with software and machines;  non-functional properties, e.g., fault tolerance;

• openness, self-adaptability; each unit/sub-unit/  element of the manufacturing system should  independently take optimal wise decisions (e.g.,  concerning resource utilization, incorporating  scheduling algorithms, planning and control  execution techniques), having a goal-driven and  cooperative behave;

• performance assessment.  Concerning future trends: it is rather difficult to forecast  long term trends for manufacturing engineering systems.

6. CONCLUSIONS

During the design process of intelligent manufacturing  cell, and during the design process of automated tool  changing system, a sequential diagram methodology was  used. This methodology was chosen to describe  communication of all devices during the manufacturing  and also assembly process. Sensor equipment was  selected following information, about the communication and signal transmission. The aim of sequential diagram  methodology use was to upgrade flexible manufacturing  cell in to the intelligent one, with help of sensor  equipment. This cell will be used for laboratory purpose. Following upgrades and development of flexible  manufacturing system are integrated to the manufacturing  process also intelligent manufacturing systems. But it is  also important to say, that problematic of intelligent  manufacturing system is still in the stay research and  development. [1]

Concept of all production devices is controlled according to  character of production. New generation production systems  vary from flexible production system not only in  construction, but especially in properties. For all that is  undoubted, that its implementation to production process  brings wide possibilities in increasing of productivity and  decreasing of production costs.

With that relates also decreasing of additional and running  times, mainly entire elimination of worker hand intervention  in production process. [2]

ACKNOWLEDGMENTS

This work was supported by VEGA 1/0285/12 Research on the possibilities of "intelligence" implementation into the assembly process

REFERENCES

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[2] N. Danišová a K. Velíšek, “Intelligent manufacturing and  assembly system.”, MD, s. 413–416, 2007.

[3] P. Košťál, A. Mudriková, a M. Charbulová, “Flexible assembly  cell and material flow planning”, Scientific Bulletin, roč. XXIII,  s. 189–194, 21.22 2009.

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[8] C. Chituc a F. José Restivo, “Challenges and Trends in  Distributed Manufacturing Systems: Are wiseengineering  systems the ultimate answer?”, in Challenges and Trends in  Distributed Manufacturing Systems, Cambridge, Massachusetts,  2009