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INTELLIGENT ASSEMBLY AND DISASSEMBLY PAST, PRESENT AND FUTURE
INTELLIGENT ASSEMBLY AND DISASSEMBLY PAST, PRESENT AND FUTURE P. Kopacek Intelligent Handling and Robotics (IHRT), Vienna University of Technology Favoritenstraße 9–11, A–1040 Vienna, Austria Tel.: +43-1-58801-31800, Fax: +43-1-58801-31899 Email: [email protected]
Abstract: Assembly automation is a classical field and well known since the late seventies. Disassembly automation is quite new and comes up approximately 15 years ago. In this paper some ideas and recent research results dealing with "intelligent" automation of assembly and disassembly are presented. Assembly automation is a classical application field of robotics today. Robots will be more and more included in assembly cells. The flexibility of these cells offers possibilities to automate assembling and disassembling of small and medium series. An approach for increasing the efficiency of disassembly cells – disassembly families – discussed. First ideas to introduce mobile robots in disassembly are presented. The premises and new direction in development of assembly and disassembly systems conclude the paper. Copyright© IFAC 2007 Keywords: Assembly, Disassembly, Recycling, MAS, Intelligent Control
1. INTRODUCTION
2. ASSEMBLY
Assembly is an important part of the production process, situated at the end of the production chain and influenced by previous manufacturing processes and parts quality. Prior mistakes, defects and errors can affect the assembly process. Disturbances in material and information supply can delay the finish of product.
According to available data, 70% of the assembly systems are designed and realized by the own personnel. Standard components are bought on the market. Currently 70-80% of the components for a semi-automated assembly cell are commercially available. The question is only the price and the maintenance. Usually enterprises have small groups of planners of assembly systems, which implement the components and information available on the market. This limited size of the project planning groups prevents comprehensive research, development of sophisticated design and development methods and implementation of methods for evaluation of chosen solutions.
In assembly and disassembly similar tasks are to solve e.g. design for assembly and disassembly, developing flexible and intelligent assembly and disassembly systems, developing the tools for solving the planning and optimization tasks. Market efforts forced manufacturers to use more and more flexible manufacturing systems with the latest technologies for a higher product quality. The environmental conscious society will have in the future a response in the development disassembly-oriented design of industrial products and automation of disassembly process.
By flexibility in the assembly process the following goals should be reached: - Achieving integral product quality - Limiting assembly and production costs - Limiting the production time - Increasing the automation grade - Ability to react fast on changing market demands
-
Shortening the introduction time for new products.
A specific problem in Small and Medium-sized Enterprises (SME’s) is lack of control and evaluation of the production costs. There is very little experience in estimating the real costs. Therefore an important parameter in deciding about the introduction of the assembly automation, i.e. economical justification is missing. Introduction of the economic criteria in the early phase of product development and later in introducing the production is one of the most important tasks of the computer aided assembly planning. One of the prerequisites for the integration into European area is an integrated management of product quality and business. Assembly automation in small series production using flexible and robotized systems enables an integrated control of the assembly operations and functional control of the product during the assembly process. Furthermore, the automated assembly includes on-line registration and analysis of production interference and production stops. Until now some research institutions directed their research into the development of computer supported models to assist engineers in designing and developing assembly oriented products and assembly systems, as well as models for integration of assembly control into the computer controlled production. These models include functional analysis implementing simulation methods. Computer-aided models (CA-m), developed on different institutions, are mainly intended for use in bigger enterprises. The main problem in the assembly and the important obstacle for introducing automation is the reliability of the systems and their availability, and still to low flexibility. These two aspects made us turn our research into the development and planning of intelligent assembly systems. These assembly systems are supposed to bring substantial improvement in rationalisation and make the small enterprises more competitive. 3. DISASSEMBLY The tremendous increasing amount of products, such as computers, printers, telephones, householdmachines and others, to be recycled (and also to be disassembled), makes it necessary to partially automate this disassembly process to increase the efficiency. Disassembling, as the first and most important point in the recycling process, will be a part of the industry with a high rate of expansion. Currently disassembling for recycling, if it is done anyway, is mainly a manual and sometimes a mechanized process.
For disassembly cells high flexibility and low-cost will be necessary. Until now a very high standard in the field of automation and robotics have been reached, but the focus was only on assembly. Few parts of scrap are recycled after disassembly, however, the degree of automation is still very small - only some pilot or demonstration projects have been realized mainly in research institutes. However also for the disassembly processes high flexibility, high accuracy, vision sensors and lowcost will be necessary. The automation potential will be one of the most important productivity factors for this new production process and becomes a new challenge for engineering. Existing concepts are very inflexible and only developed for a special task or product. „Stiff“ automatized disassembly in single purpose cells – only for one product (e.g. one type of PC`s) – cannot be economically feasible today. The number of devices or parts to be collected and concentrated on the place of the disassembly cell is usually to low for a two shift operation of the cell. For example in the case of computer-keyboards of a distinct type all keyboards from whole Europe per year could be disassembled in three months by one fully automatized cell. 4. COMPONENTS OF ASSEMBLY AND DISASSEMBLY CELLS In the past there were several projects worldwide trying to develop single purpose fully automatized disassembly cells for only distinct products. Such cells can be not operated economically because that is a kind of stiff automation and one of the main problems is to carry this special type of devices to disassembly cells. Therefore such projects yield only to pilot plants, e.g. cells for PC-keyboards. Therefore the new approach on this problem is to develop multipurpose semi-automatized disassembly cells. One approach is to develop a modular system for such cells like a “tool kit”. Such a system must be easily adaptable to various types of devices. Furthermore it should be easily moveable and transportable and therefore it can operate on different places. According to the last estimation is this modular system approximately 60% of the total weight of electr(on)ic devices, especially devices from the consumer electronics, information electronics, communication electronics, industrial electronics, medical devices, laboratory equipments and office equipments could be assembled as well as disassembled. The worldwide literature overview yields to the result that in several research laboratories as well as at universities some project groups are working intensively on this stiff automated single purpose cells as mentioned before. Examples are cells for car
bodies, for some types of PCs, TV-sets, mobile phones, TFT screens….. (Intell.) Cell Control Unit
Disassembly Robot Robot Gripper Disassembly Tools
Storage Devices
Disassembly Cell
Components Database
Transport System Clamping Device Manual Disassembly station
Sensors Force Torque
Visual
Pos. Dist.
Fig. 1 Modules of a disassembly cell (Kopacek and Kopacek, 2001) An analysis of the tools in a disassembly cell was already given by Gschwendtner and Kopacek, 1996 and because of the existing experience about assembly cells, similarities and differences between them and disassembly cells have also be pointed out there. The main parts of such a disassembly cell – the modules of the „tool kit“ – are: Disassembly robots and handling devices: Because of economical reasons it is necessary to use commercially available devices on the market today. These robots or handling devices should have special features for disassembly tasks like a reasonable high accuracy and the possibility for position as well as force control. A marketing research yields to the result that the robots and handling devices commercially available today are not reasonable suitable for these new tasks. Especially the feature the robot controller should be able to be included in a PC network is only partially available today. Furthermore it have to be equipped with a “modern” controller based on an operating system commonly used and offers the possibility to work with signals from a wide range of sensors from simple low-cost sensors (e.g. micro switches, ….) to complex “embedded” sensors ( e.g. force torque sensors,…..). Grippers: This is an old problem in the field of industrial robots to develop universal gripping units with the flexibility like the human hand. Especially in disassembly a broad variety of parts with different geometries and sizes must be handled. Today this problem will be solved by multi-gripper systems or gripper changing systems. Multi-gripper systems are very expensive and very space consuming. Gripper changing devices have the disadvantage of a high price and also a high weight (usually 2 – 3 kg). Furthermore changing a gripper is time consuming. Therefore the development of intelligent, reasonable
cheap, multi-purpose grippers equipped with simple sensors is necessary. They have to be a compromise between flexibility, costs and grasping speed. Disassembly technologies and tools: Several research and university institutes were busy in the last years to develop special disassembly tools. These tools based on very well known tools from manual disassembly are adapted for a robot. Only in some special cases some new tools like a combination between drilling unit with integrated gripper were developed. If we are looking to electronic components it is necessary to desolder such components. Today the desoldering process is carried out by hot vapour as well as hot air. The main problem is the overheating of the electronic components during the desoldering process. Overheating reduce dramatically the remaining lifetime of the components. Usually desoldering temperatures are closely connected to the melting points of the different soldering materials – usually between 175 and 270 ºC. A new technology in this field is laser technology. Feeding systems Feeding systems are very important for disassembly cells. Because of the partially intelligent industrial robots each part must be in the same position in the same orientation. In disassembly the parts to be disassembled are usually always in the same position. Therefore feeding of the cell is currently carried mostly manually for disassembly purposes. In the future intelligent robots will be available. An exact position and orientation of the parts to be handled is than not necessary. Transportation devices: Transportation devices are nearly the same than 30 years ago. Additional features are the much higher accuracy necessary for disassembly operations for positioning the parts. Furthermore in contrast to assembly forces in vertical direction occur some times for disassembly operations. Fixturing systems: Because of the wide variety in geometry and sizes of the parts to be disassembled fixture systems with a high degree of flexibility are necessary. Intelligent control concepts: PLC’s today are equipped with very powerful micro processors according to the availability in the PC world. These processors are responsible to a very high capacity of such controllers. Today PLC’s are available on the market relatively cheap and usually modular. On the other hand industrial PC’s are also available on the market on reasonable prices, equipped with an appropriate interface as well as high capacity.
Fig. 2 Control System of the Disassembly Cell – Example (Kopacek et.al.2000) The control system of a disassembly cell is usually modular. Each module has a controller which can supervise, at least, the execution of a single step. The host computer, usually an industrial PC, has the task coordinate the interaction between the subsystems (Fig. 2). The control system has several databases in which all information about the disassembly cell are stored: parameters for the modules, program numbers of the subsystems, data of the parts, layout and content of the magazine, error codes, runtime errors of the cell…….. Human Machine Interface – HMI: As the demand for real time could be branched out to lower level controllers. Today one possibility is to implement the control system using Microsoft Visual C++ under Microsoft Windows (Fig. 3). Hence the user interface is intuitive and easy to use. The Control System displays the actual state of all modules within the cell. The operating system brings along the infrastructure for networking. So a remote access maintenance system using internet connection can be used. Image processing systems: Image processing system consists of lightning, camera, frame grabber card and software. Today a lot of such systems are available on the market. For this purpose low-cost image processing systems are necessary. This system is a main part and the most important part in a flexible modular Disassembly cell. Previous projects were not very efficient
because the accuracy or the costs for such systems. Lightning: Until now transmitted light yields to a shadow image of the object and therefore it is only applicable for inspirant materials. Usually the parts to be disassembled are transparent and therefore this system is not applicable for this purpose. Further possibilities are: neon tubes, circle light, cold light sources, line lightning, indirect lightning and infrared. After tests we used two line lights. Camera: Usually there are two possibilities: area cameras and CCD-cameras. According to our experiences area cameras a very expensive and have not the necessary accuracy. In most of our applications we selected CCD-cameras with 4096 pixels in an area of 220 x 300 mm. Frame grabber card: The frame grabber card has the task to transfer a video signal from the camera in a format readable for the PC. Image processing software: The image processing software must be in the position size and the positions of the Disassembly parts to recognize with an accuracy of +/- 0.1 mm. Another task is the optical character recognition (OCR) able to recognize in the area mentioned before under the characters in an open three pitch font with a probability of 85 – 90%.
Fig. 3 Example of an HMI (Kopacek et.al., 2000)
External sensors: For this application various sensors for force and moments as well as for position and distance recognition are necessary. Because of the advances in sensor technology in the last years it is no problem to buy such sensors on the market. Manual working places: Manual working places are similar to those of assembly cells. For disassembly cells manual working places are necessary for attaching the printed board on special pallets and to remove the disassembly parts. Storage systems: Usually in disassembly cells we need storage systems for parts and tools because of the necessity to operate the cell without tool changing. On the other hand part storage devices reduce the interruption time of such a cell. Databases for disassembled parts: Main data of reuse-able parts are stored in databases. The efficiency of such a disassembly cell is closely connected to the structure of such a database. One problem is the very high number of data to be stored in such a database.
5. DEVELOPMENT TRENDS OF INTELLIGENT ROBOT CELLS Most of the automation technologies have been developed for large companies with big lot sizes and are usually complex and expensive. Therefore they are not suitable for SME`s. They need simple, flexible and cheap automation solutions. Robot production cells for SME`s have to be available to a reasonable price according to the current international research headline “Cost Oriented Automation – COA “. One of the most important advantages of European SME`s, in contrast to Asian companies, is flexibility. Flexibility is closely related to the production of very small lot sizes – the theoretical goal is the production of one part – in an economic way. One possible approach (Haegele and Nilsson, 2006) is the development of robotic cells with robots from different producers with the same peripheral devices (Fig. 1). The interface will be the connector from the robot to the control computer. The result could be an incomplete, flexible, modular system - “tool kit” - of hard- and software compatible modules with the following goals: - Reducing the average costs of a robot production cell from approximately €150.000.-- to approximately € 75.000.-- or less.
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Reducing of the re-programming time of such cells to 20%. Reducing the installation time of a cell to 20% or three days. Reduce the meantime between operational failures of the system to 10%. Reduce the process-tuning time to 10%. Reduce the time for service and maintenance at least to 50%. Increase the sensor supported operations from 5% to 100%. Guarantee a 100% safe operation
According to the special application the necessary modules can be easily combined to a cell. For some applications missing modules have to be developed for new tasks. This yields to a continuously completion of the “tool kit”. For inclusion such cells have to be hard- and software compatible with CIM- and IMS Systems 6. ROBOTS FOR (DIS) - ASSEMBLY Robots for disassembly cells could be stationary as usual today or mobile as a new approach in the future. 6.1. Stationary disassembly robots Stationary robots are mostly used today. A stationary disassembly robot should have the following features: - Intelligent: equipped with a vision system and other external sensors (force, torque, ...) - Position as well as force control - Reasonable accuracy - Reasonable payload for destroying some connections and carrying tools as well as toolchanging systems - Appropriate kinematics structure - Ability to cooperate with other (stationary) robots - User friendly interface – the employees in recycling companies are mostly unskilled. These features could be reached by: - The robot capable of understanding human-like instructions - The safe and productive human-aware spacesharing robot - The three-day-deployable integrated robot system.
Fig. 4 Disassembly Multi-Agent-Systems (DMAS) In addition to stationary disassembly mobile robots for disassembly should be: - intelligent in the sense of path planning - able to communicate with other robots - cooperative with other (stationary or mobile) robots and - able to form a Disassembly Multi Agent System – DMAS One of the future possibilities to reduce the disassembly costs is Disassembly-Multi-AgentSystems (DMAS). Derived from Multi-AgentSystems (MAS) such systems are one of the key technologies for constructing decentralized, adaptive, intelligent and complex systems. A DMAS consists of several „agents“ (soft- and hardware) working together towards a common goal, having different features for specific subtasks. Therefore only the definition of a global task is necessary for a DMAS. The software of the system divides this global task in a number of subtasks. The „agents“ try to fulfil these subtasks in a cooperative way. 7. CONCLUSIONS AND OUTLOOK Assembly automation is well known since some decades. Disassembly automation is relatively new but absolutely necessary in the nearest future because of End-of-Life Management (EoL) and the dramatically increasing amount of scrap from technical devices. Today unintelligent assembly cells are available on the market and a lot of research is going on to make these more cells intelligent. In disassembly automation only some pilot projects in form of fully automated single purpose solutions – and only for one distinct type of one product – are realized. Main problem is the collection and transportation of a sufficient amount of these products to one place in one area.
6.2. Mobile Disassembly robots Mobile robots offer new possibilities e.g. flexible Disassembly of huge and heavy devices (Fig. 4)
Therefore it is necessary to disassemble more than one product in an automatized or semiautomatized cell. For this purpose products with similar disassembly operations are collected in „Disassembly families“ - families which are disassembled in
modular cells, developed by means of computer aided planning systems. Furthermore a modular concept for developing disassembly cells for different disassembly families in an economic way is also presented. The further development depends from “new technologies” e.g. embedded, cheap sensors; RFID technology……Furthermore the HMI for robot operation will get more and more “human friendly”. There are a lot of security problems to solve e.g. “Softwarewalls or – fences”. The main goals have to be: Modular, intelligent and flexible cells for assembly and disassembly with automated recognition of the parts (kind, surface, dimensions, orientation…), designed computer aided – the process as well as the cells with universal clamping devices. For large and heavy products to disassemble (e.g. cars,... ) a new approach based on mobile robots and Multi-Agent-Systems (MAS) was presented. Such Disassembly-Multi-Agent-Systems (DMAS) avoid disadvantages like construction of huge Disassembly cells for large products. Today only a few steps in that direction are done. The agents-mobile-robots equipped with different tools - get the direction from a host computer. Probably in the next decade real DMAS will be available for practical purpose. 8. REFERENCES Gschwendtner, G. and P. Kopacek (1996). A concept for a Flexible Intelligent Semiautomatized PC Disassembly Cell. In: Proceedings of the 5th International Workshop on Robotics in AlpeAdria-Danube Region RAAD’96, June 10-13, 1996, Budapest, Hungary, p. 405-410. Haegele, M. and K. Nilsson (2006). SMErobot: The European Robot Initiative for Strengthening the Competitiveness of SMEs in Manufacturing. Key-Note at the European Robotics Conference (EUROS 2006), March 17th, 2006, Palermo, Italy. Kopacek, B.; and P. Kopacek (1999). Intelligent Disassembly of Electronic Equipment. In Annual Reviews in Control, Pergamon Press, 23 1999, p.165-170. Kopacek, P. B. Kopacek, H. Zebedin (2000). Hierarchical Control of Disassembly Cells, Preprints of the 4th Symposium on Intelligent Components and Instruments for Control Applications, Buenos Aires, p. 256-272. Kopacek, P and D. Noe (2001). Intelligent, Flexible Assembly and Disassembly. In: Proceedings of the 2nd Workshop on Intelligent Assembly and Disassembly – IAD´2001, Canela, Brasil, 5. - 7. November 2001, p. 1-10. Kopacek, P. and B. Kopacek (2003). Trends in semi automatised assembly and disassembly. In: Proceedings of the 2nd FIRA Robot Soccer World
Congress, Vol. 2, 1st Austrian-Korean Joint Seminar “Intelligent Autonomous Robots”, ISBN 3-902161-01-9, 1. – 3. October 2003 Kopacek, P. and B. Kopacek (2005). Intelligent, flexible disassembly. Published online at www.springerlink.com, in: The International Journal of Advanced Manufacturing Technology, 24. November 2005, SpringerVerlag London Ltd, ISSN 1433-3015
Abstract: Assembly automation is a classical field and well known since the late seventies. Disassembly automation is quite new and comes up approximately 15 years ago. In this paper some ideas and recent research results dealing with "intelligent" automation of assembly and disassembly are presented. Assembly automation is a classical application field of robotics today. Robots will be more and more included in assembly cells. The flexibility of these cells offers possibilities to automate assembling and disassembling of small and medium series. An approach for increasing the efficiency of disassembly cells – disassembly families – discussed. First ideas to introduce mobile robots in disassembly are presented. The premises and new direction in development of assembly and disassembly systems conclude the paper. Copyright© IFAC 2007 Keywords: Assembly, Disassembly, Recycling, MAS, Intelligent Control
1. INTRODUCTION
2. ASSEMBLY
Assembly is an important part of the production process, situated at the end of the production chain and influenced by previous manufacturing processes and parts quality. Prior mistakes, defects and errors can affect the assembly process. Disturbances in material and information supply can delay the finish of product.
According to available data, 70% of the assembly systems are designed and realized by the own personnel. Standard components are bought on the market. Currently 70-80% of the components for a semi-automated assembly cell are commercially available. The question is only the price and the maintenance. Usually enterprises have small groups of planners of assembly systems, which implement the components and information available on the market. This limited size of the project planning groups prevents comprehensive research, development of sophisticated design and development methods and implementation of methods for evaluation of chosen solutions.
In assembly and disassembly similar tasks are to solve e.g. design for assembly and disassembly, developing flexible and intelligent assembly and disassembly systems, developing the tools for solving the planning and optimization tasks. Market efforts forced manufacturers to use more and more flexible manufacturing systems with the latest technologies for a higher product quality. The environmental conscious society will have in the future a response in the development disassembly-oriented design of industrial products and automation of disassembly process.
By flexibility in the assembly process the following goals should be reached: - Achieving integral product quality - Limiting assembly and production costs - Limiting the production time - Increasing the automation grade - Ability to react fast on changing market demands
-
Shortening the introduction time for new products.
A specific problem in Small and Medium-sized Enterprises (SME’s) is lack of control and evaluation of the production costs. There is very little experience in estimating the real costs. Therefore an important parameter in deciding about the introduction of the assembly automation, i.e. economical justification is missing. Introduction of the economic criteria in the early phase of product development and later in introducing the production is one of the most important tasks of the computer aided assembly planning. One of the prerequisites for the integration into European area is an integrated management of product quality and business. Assembly automation in small series production using flexible and robotized systems enables an integrated control of the assembly operations and functional control of the product during the assembly process. Furthermore, the automated assembly includes on-line registration and analysis of production interference and production stops. Until now some research institutions directed their research into the development of computer supported models to assist engineers in designing and developing assembly oriented products and assembly systems, as well as models for integration of assembly control into the computer controlled production. These models include functional analysis implementing simulation methods. Computer-aided models (CA-m), developed on different institutions, are mainly intended for use in bigger enterprises. The main problem in the assembly and the important obstacle for introducing automation is the reliability of the systems and their availability, and still to low flexibility. These two aspects made us turn our research into the development and planning of intelligent assembly systems. These assembly systems are supposed to bring substantial improvement in rationalisation and make the small enterprises more competitive. 3. DISASSEMBLY The tremendous increasing amount of products, such as computers, printers, telephones, householdmachines and others, to be recycled (and also to be disassembled), makes it necessary to partially automate this disassembly process to increase the efficiency. Disassembling, as the first and most important point in the recycling process, will be a part of the industry with a high rate of expansion. Currently disassembling for recycling, if it is done anyway, is mainly a manual and sometimes a mechanized process.
For disassembly cells high flexibility and low-cost will be necessary. Until now a very high standard in the field of automation and robotics have been reached, but the focus was only on assembly. Few parts of scrap are recycled after disassembly, however, the degree of automation is still very small - only some pilot or demonstration projects have been realized mainly in research institutes. However also for the disassembly processes high flexibility, high accuracy, vision sensors and lowcost will be necessary. The automation potential will be one of the most important productivity factors for this new production process and becomes a new challenge for engineering. Existing concepts are very inflexible and only developed for a special task or product. „Stiff“ automatized disassembly in single purpose cells – only for one product (e.g. one type of PC`s) – cannot be economically feasible today. The number of devices or parts to be collected and concentrated on the place of the disassembly cell is usually to low for a two shift operation of the cell. For example in the case of computer-keyboards of a distinct type all keyboards from whole Europe per year could be disassembled in three months by one fully automatized cell. 4. COMPONENTS OF ASSEMBLY AND DISASSEMBLY CELLS In the past there were several projects worldwide trying to develop single purpose fully automatized disassembly cells for only distinct products. Such cells can be not operated economically because that is a kind of stiff automation and one of the main problems is to carry this special type of devices to disassembly cells. Therefore such projects yield only to pilot plants, e.g. cells for PC-keyboards. Therefore the new approach on this problem is to develop multipurpose semi-automatized disassembly cells. One approach is to develop a modular system for such cells like a “tool kit”. Such a system must be easily adaptable to various types of devices. Furthermore it should be easily moveable and transportable and therefore it can operate on different places. According to the last estimation is this modular system approximately 60% of the total weight of electr(on)ic devices, especially devices from the consumer electronics, information electronics, communication electronics, industrial electronics, medical devices, laboratory equipments and office equipments could be assembled as well as disassembled. The worldwide literature overview yields to the result that in several research laboratories as well as at universities some project groups are working intensively on this stiff automated single purpose cells as mentioned before. Examples are cells for car
bodies, for some types of PCs, TV-sets, mobile phones, TFT screens….. (Intell.) Cell Control Unit
Disassembly Robot Robot Gripper Disassembly Tools
Storage Devices
Disassembly Cell
Components Database
Transport System Clamping Device Manual Disassembly station
Sensors Force Torque
Visual
Pos. Dist.
Fig. 1 Modules of a disassembly cell (Kopacek and Kopacek, 2001) An analysis of the tools in a disassembly cell was already given by Gschwendtner and Kopacek, 1996 and because of the existing experience about assembly cells, similarities and differences between them and disassembly cells have also be pointed out there. The main parts of such a disassembly cell – the modules of the „tool kit“ – are: Disassembly robots and handling devices: Because of economical reasons it is necessary to use commercially available devices on the market today. These robots or handling devices should have special features for disassembly tasks like a reasonable high accuracy and the possibility for position as well as force control. A marketing research yields to the result that the robots and handling devices commercially available today are not reasonable suitable for these new tasks. Especially the feature the robot controller should be able to be included in a PC network is only partially available today. Furthermore it have to be equipped with a “modern” controller based on an operating system commonly used and offers the possibility to work with signals from a wide range of sensors from simple low-cost sensors (e.g. micro switches, ….) to complex “embedded” sensors ( e.g. force torque sensors,…..). Grippers: This is an old problem in the field of industrial robots to develop universal gripping units with the flexibility like the human hand. Especially in disassembly a broad variety of parts with different geometries and sizes must be handled. Today this problem will be solved by multi-gripper systems or gripper changing systems. Multi-gripper systems are very expensive and very space consuming. Gripper changing devices have the disadvantage of a high price and also a high weight (usually 2 – 3 kg). Furthermore changing a gripper is time consuming. Therefore the development of intelligent, reasonable
cheap, multi-purpose grippers equipped with simple sensors is necessary. They have to be a compromise between flexibility, costs and grasping speed. Disassembly technologies and tools: Several research and university institutes were busy in the last years to develop special disassembly tools. These tools based on very well known tools from manual disassembly are adapted for a robot. Only in some special cases some new tools like a combination between drilling unit with integrated gripper were developed. If we are looking to electronic components it is necessary to desolder such components. Today the desoldering process is carried out by hot vapour as well as hot air. The main problem is the overheating of the electronic components during the desoldering process. Overheating reduce dramatically the remaining lifetime of the components. Usually desoldering temperatures are closely connected to the melting points of the different soldering materials – usually between 175 and 270 ºC. A new technology in this field is laser technology. Feeding systems Feeding systems are very important for disassembly cells. Because of the partially intelligent industrial robots each part must be in the same position in the same orientation. In disassembly the parts to be disassembled are usually always in the same position. Therefore feeding of the cell is currently carried mostly manually for disassembly purposes. In the future intelligent robots will be available. An exact position and orientation of the parts to be handled is than not necessary. Transportation devices: Transportation devices are nearly the same than 30 years ago. Additional features are the much higher accuracy necessary for disassembly operations for positioning the parts. Furthermore in contrast to assembly forces in vertical direction occur some times for disassembly operations. Fixturing systems: Because of the wide variety in geometry and sizes of the parts to be disassembled fixture systems with a high degree of flexibility are necessary. Intelligent control concepts: PLC’s today are equipped with very powerful micro processors according to the availability in the PC world. These processors are responsible to a very high capacity of such controllers. Today PLC’s are available on the market relatively cheap and usually modular. On the other hand industrial PC’s are also available on the market on reasonable prices, equipped with an appropriate interface as well as high capacity.
Fig. 2 Control System of the Disassembly Cell – Example (Kopacek et.al.2000) The control system of a disassembly cell is usually modular. Each module has a controller which can supervise, at least, the execution of a single step. The host computer, usually an industrial PC, has the task coordinate the interaction between the subsystems (Fig. 2). The control system has several databases in which all information about the disassembly cell are stored: parameters for the modules, program numbers of the subsystems, data of the parts, layout and content of the magazine, error codes, runtime errors of the cell…….. Human Machine Interface – HMI: As the demand for real time could be branched out to lower level controllers. Today one possibility is to implement the control system using Microsoft Visual C++ under Microsoft Windows (Fig. 3). Hence the user interface is intuitive and easy to use. The Control System displays the actual state of all modules within the cell. The operating system brings along the infrastructure for networking. So a remote access maintenance system using internet connection can be used. Image processing systems: Image processing system consists of lightning, camera, frame grabber card and software. Today a lot of such systems are available on the market. For this purpose low-cost image processing systems are necessary. This system is a main part and the most important part in a flexible modular Disassembly cell. Previous projects were not very efficient
because the accuracy or the costs for such systems. Lightning: Until now transmitted light yields to a shadow image of the object and therefore it is only applicable for inspirant materials. Usually the parts to be disassembled are transparent and therefore this system is not applicable for this purpose. Further possibilities are: neon tubes, circle light, cold light sources, line lightning, indirect lightning and infrared. After tests we used two line lights. Camera: Usually there are two possibilities: area cameras and CCD-cameras. According to our experiences area cameras a very expensive and have not the necessary accuracy. In most of our applications we selected CCD-cameras with 4096 pixels in an area of 220 x 300 mm. Frame grabber card: The frame grabber card has the task to transfer a video signal from the camera in a format readable for the PC. Image processing software: The image processing software must be in the position size and the positions of the Disassembly parts to recognize with an accuracy of +/- 0.1 mm. Another task is the optical character recognition (OCR) able to recognize in the area mentioned before under the characters in an open three pitch font with a probability of 85 – 90%.
Fig. 3 Example of an HMI (Kopacek et.al., 2000)
External sensors: For this application various sensors for force and moments as well as for position and distance recognition are necessary. Because of the advances in sensor technology in the last years it is no problem to buy such sensors on the market. Manual working places: Manual working places are similar to those of assembly cells. For disassembly cells manual working places are necessary for attaching the printed board on special pallets and to remove the disassembly parts. Storage systems: Usually in disassembly cells we need storage systems for parts and tools because of the necessity to operate the cell without tool changing. On the other hand part storage devices reduce the interruption time of such a cell. Databases for disassembled parts: Main data of reuse-able parts are stored in databases. The efficiency of such a disassembly cell is closely connected to the structure of such a database. One problem is the very high number of data to be stored in such a database.
5. DEVELOPMENT TRENDS OF INTELLIGENT ROBOT CELLS Most of the automation technologies have been developed for large companies with big lot sizes and are usually complex and expensive. Therefore they are not suitable for SME`s. They need simple, flexible and cheap automation solutions. Robot production cells for SME`s have to be available to a reasonable price according to the current international research headline “Cost Oriented Automation – COA “. One of the most important advantages of European SME`s, in contrast to Asian companies, is flexibility. Flexibility is closely related to the production of very small lot sizes – the theoretical goal is the production of one part – in an economic way. One possible approach (Haegele and Nilsson, 2006) is the development of robotic cells with robots from different producers with the same peripheral devices (Fig. 1). The interface will be the connector from the robot to the control computer. The result could be an incomplete, flexible, modular system - “tool kit” - of hard- and software compatible modules with the following goals: - Reducing the average costs of a robot production cell from approximately €150.000.-- to approximately € 75.000.-- or less.
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Reducing of the re-programming time of such cells to 20%. Reducing the installation time of a cell to 20% or three days. Reduce the meantime between operational failures of the system to 10%. Reduce the process-tuning time to 10%. Reduce the time for service and maintenance at least to 50%. Increase the sensor supported operations from 5% to 100%. Guarantee a 100% safe operation
According to the special application the necessary modules can be easily combined to a cell. For some applications missing modules have to be developed for new tasks. This yields to a continuously completion of the “tool kit”. For inclusion such cells have to be hard- and software compatible with CIM- and IMS Systems 6. ROBOTS FOR (DIS) - ASSEMBLY Robots for disassembly cells could be stationary as usual today or mobile as a new approach in the future. 6.1. Stationary disassembly robots Stationary robots are mostly used today. A stationary disassembly robot should have the following features: - Intelligent: equipped with a vision system and other external sensors (force, torque, ...) - Position as well as force control - Reasonable accuracy - Reasonable payload for destroying some connections and carrying tools as well as toolchanging systems - Appropriate kinematics structure - Ability to cooperate with other (stationary) robots - User friendly interface – the employees in recycling companies are mostly unskilled. These features could be reached by: - The robot capable of understanding human-like instructions - The safe and productive human-aware spacesharing robot - The three-day-deployable integrated robot system.
Fig. 4 Disassembly Multi-Agent-Systems (DMAS) In addition to stationary disassembly mobile robots for disassembly should be: - intelligent in the sense of path planning - able to communicate with other robots - cooperative with other (stationary or mobile) robots and - able to form a Disassembly Multi Agent System – DMAS One of the future possibilities to reduce the disassembly costs is Disassembly-Multi-AgentSystems (DMAS). Derived from Multi-AgentSystems (MAS) such systems are one of the key technologies for constructing decentralized, adaptive, intelligent and complex systems. A DMAS consists of several „agents“ (soft- and hardware) working together towards a common goal, having different features for specific subtasks. Therefore only the definition of a global task is necessary for a DMAS. The software of the system divides this global task in a number of subtasks. The „agents“ try to fulfil these subtasks in a cooperative way. 7. CONCLUSIONS AND OUTLOOK Assembly automation is well known since some decades. Disassembly automation is relatively new but absolutely necessary in the nearest future because of End-of-Life Management (EoL) and the dramatically increasing amount of scrap from technical devices. Today unintelligent assembly cells are available on the market and a lot of research is going on to make these more cells intelligent. In disassembly automation only some pilot projects in form of fully automated single purpose solutions – and only for one distinct type of one product – are realized. Main problem is the collection and transportation of a sufficient amount of these products to one place in one area.
6.2. Mobile Disassembly robots Mobile robots offer new possibilities e.g. flexible Disassembly of huge and heavy devices (Fig. 4)
Therefore it is necessary to disassemble more than one product in an automatized or semiautomatized cell. For this purpose products with similar disassembly operations are collected in „Disassembly families“ - families which are disassembled in
modular cells, developed by means of computer aided planning systems. Furthermore a modular concept for developing disassembly cells for different disassembly families in an economic way is also presented. The further development depends from “new technologies” e.g. embedded, cheap sensors; RFID technology……Furthermore the HMI for robot operation will get more and more “human friendly”. There are a lot of security problems to solve e.g. “Softwarewalls or – fences”. The main goals have to be: Modular, intelligent and flexible cells for assembly and disassembly with automated recognition of the parts (kind, surface, dimensions, orientation…), designed computer aided – the process as well as the cells with universal clamping devices. For large and heavy products to disassemble (e.g. cars,... ) a new approach based on mobile robots and Multi-Agent-Systems (MAS) was presented. Such Disassembly-Multi-Agent-Systems (DMAS) avoid disadvantages like construction of huge Disassembly cells for large products. Today only a few steps in that direction are done. The agents-mobile-robots equipped with different tools - get the direction from a host computer. Probably in the next decade real DMAS will be available for practical purpose. 8. REFERENCES Gschwendtner, G. and P. Kopacek (1996). A concept for a Flexible Intelligent Semiautomatized PC Disassembly Cell. In: Proceedings of the 5th International Workshop on Robotics in AlpeAdria-Danube Region RAAD’96, June 10-13, 1996, Budapest, Hungary, p. 405-410. Haegele, M. and K. Nilsson (2006). SMErobot: The European Robot Initiative for Strengthening the Competitiveness of SMEs in Manufacturing. Key-Note at the European Robotics Conference (EUROS 2006), March 17th, 2006, Palermo, Italy. Kopacek, B.; and P. Kopacek (1999). Intelligent Disassembly of Electronic Equipment. In Annual Reviews in Control, Pergamon Press, 23 1999, p.165-170. Kopacek, P. B. Kopacek, H. Zebedin (2000). Hierarchical Control of Disassembly Cells, Preprints of the 4th Symposium on Intelligent Components and Instruments for Control Applications, Buenos Aires, p. 256-272. Kopacek, P and D. Noe (2001). Intelligent, Flexible Assembly and Disassembly. In: Proceedings of the 2nd Workshop on Intelligent Assembly and Disassembly – IAD´2001, Canela, Brasil, 5. - 7. November 2001, p. 1-10. Kopacek, P. and B. Kopacek (2003). Trends in semi automatised assembly and disassembly. In: Proceedings of the 2nd FIRA Robot Soccer World
Congress, Vol. 2, 1st Austrian-Korean Joint Seminar “Intelligent Autonomous Robots”, ISBN 3-902161-01-9, 1. – 3. October 2003 Kopacek, P. and B. Kopacek (2005). Intelligent, flexible disassembly. Published online at www.springerlink.com, in: The International Journal of Advanced Manufacturing Technology, 24. November 2005, SpringerVerlag London Ltd, ISSN 1433-3015