机电 自动化控制类 外文翻译英文文献 为柔性制造系统设计的可编程控制器平台.docx

1、机电 自动化控制类 外文翻译 英文文献 为柔性制造系统设计的可编程控制器平台Theoretical Computer Science 253 (2001) 6193Developing a Hybrid Programmable Logic Controller Platform for a Flexible Manufacturing SystemHenning Dierks 1University of Oldenburg, Fachbereich Informatik, Postfach 2503, 2900 Oldenburg, GermanyAbstract: In this art

2、icle, we present the design and implementation of a flexible manufacturing system (FMS) control platform based on a programmable logic controller (PLC) and a personal computer (PC)-based visual man-machine interface (MMI) and data acquisition (DAS) unit. The key aspect of an FMS is its flexibility t

3、o adapt to changes in a demanding process operation. The PLC provides feasible solutions to FMS applications, using PC-based MMI/DAS, whereby PLCs are optimized for executing rapid sequential control strategies. PCs running MMI/DAS front-ends make intuitive operation interfaces, full of powerful gra

4、phics and reporting tools. Information from the PC can be distributed through a companys local area network or web using client-server technologies. Currently, with the convergence of underlying microprocessor technology and software program-ming techniques, many users find that PLCs provide a cost-

5、effective solution to real-time control in small- to medium-sized process plants, especially when combined with supervisory PCs using hybrid systems. The major work of this article demonstrates that PLCs are responsive to rapid and repetitious control tasks, using PCs that present the flow of inform

6、ation automation and accept operator instructions, thereby providing the user a tool to modify and monitor the process as the requirements change.Key Words: PLC、FMS、PC.1IntroductionIn a variety of product manufacturing industries, the most automated form of production is a Flexible manufacturing sys

7、tem(FMS),first introduced in 1970s. Since the FMSs can providea high potential for productivity improvement in batch manufacturing, the number of FMSs is growing substantially (Groover and Zimmers, 1984). The acceleration throughout the world is due to increased global competition, reduced manufactu

8、ring cycle times, and cuts in production costs.Generally, an FMS consists of a group of machines or other automated work stations, which form into modular subsystems, such as CNC machines, robots, vision systems, and a process station. These are interconnected by a materials handling system and usua

9、lly driven by a computer(Maleki,1991).Each modular system requires an individual modular control system, with different components being controlled by individual controller units. All of the modular subsystems are controlled by computers as usual. These controllers perform their intended tasks under

10、 supervision of a higher level controller. To the system, both the control devices as well as the flow of information need to be automated. The key aspect of an FMS is its ability to adapt to changes in the control tasks. This flexibility includes the quantities and varieties of part types which it

11、can produce, the order in which operations may be performed, and its ability to reroute parts back into flow paths. In the end, the control platform should have the capability to automate the flow of information.Typically, there are three types of control platforms used in FMSs: minicomputers, micro

12、computers, and PLCs (Maleki, 1991). The minicomputers are best suited for complex large-scale, continuous ,regulatory control applications . The PLCs are used for rapid and repetitious logic control. Personal computers (PCs) are suited for operator interface functions. Primarily, PLCs are designed t

13、o replace hardwiring relays, to operate in an industrial environment, to be easily modified by plant engineers and maintenance personnel, and to be maintained by plant electricians. Currently, with the convergence of underlying microprocessor technology and software programming, many users find that

14、 PLCs provide a cost-effective solution to real-time control in small-to medium-sized process plants, especially when combined with supervisory PCs using hybrid systems.The purpose of this article is to address the state-of-the-art technology of FMSs. The design and construction of an FMS using PLC-

15、controlled and PC-based visual man-machine interface(MMI) and data acquisition system(DAS) are presented. It is organized as follows. Section 2 begins with the description of the FMS on the factory floor of the Center for Manufacturing System sat the NewJersey Institute of Technology(NJIT).Section 3

16、 shows the operational description of the FMS. Sections 4 and 5 present the applications of PLC-controlled and PC-based MMI/DAS for the FMS at NJIT. Section 6 contains a summary of the advantages of this PLC-controlled and PC-based MMI/DAS for FMS application.2. Description of the FMSSI handling con

17、veyor systemThis consists of four carts, A, B, C, and D, with fixtures mounted on each, two transfer tables,TT1 and TT2 , and dual conveyors which transport materials to each workstation.Figure 1. Flexible manufacturing system.NASA II CNC milling machineThe milling machine accepts rectangular solid

18、blanks and machines each part of different types according to its computer controller.GE P50 robotA shared robot is used to load and unload the material between the CNC milling machine and the conveyor system, and between the parts presentation station and conveyor system. It contains five computer

19、programs assignable by the PLC. The computer programs direct the robot to load the material between the parts presentation station and the carts and between the CNC machine and the carts. The last two programs place the completed parts in the accept or reject area.Parts presentation stationThis stat

20、ion includes a gravity-chute, which supplies rectangular solid blanks as raw materials. This station also contains two bin types, one each for accepted parts and rejected parts.Computer vision systemThe vision system provides for the visual automated inspection of the parts. It is a menu-driven, 64-

21、level gray scale, edge detection system.Drilling machineAn IBM7535 industrial robot with an automated drill as an end-effector drills various holes in the parts as directed.In summary, the FMS has two robots, one CNC mill, a material transfer convey or system including transportation carts and posit

22、ioning limit switches, and a vision system, which are supervised by a GE-Series Six PLC and monitored by a PC-based visual MMI/DAS.3. Operational descriptionThe working cycle for this FMS proceeds in the following manner:1.Initially, all four carts on the conveyor system are empty and available for

23、the raw materials to be loaded onto them from the parts presentation station.2.The GE robot loads four parts, one by one, on to the four carts on the convey or system. The carts move clock wise as they are being loaded.3. Figure 2 shows the positions acquired by the four carts once the four parts of

24、 different types have been loaded.4. The IBM robot drills various holes on each blank part as the cart stops at the drilling machine.5. The GE robot moves to the conveyor, removes the part from the cart at position X1,and loads it into the fixture located on the CNC machine table.6. Once the part is

25、 loaded on the CNC milling machine, the robot retracts, and the milling machine mills the rectangular part as required.7. After the milling operation, the robot arm moves to the milling machine to remove the part that was machined from the holding fixture.Figure 2. Loading state of the conveyor syst

26、em.8. The robot returns the finished part to the same cart on the conveyor.9. A signal is sent to the vision camera to inspect the part.10. The vision system analyzes the part and outputs a signal that directs the robot to accept or reject the part.11. The robot runs either an accept program to plac

27、e the part in the accept bin or runs a reject program to place the part in the reject bin.12. The GE robot goes to the parts presentation station and loads a new blank part into the cart.13. The cart is released to the system and the next cycle is started.4. Control of an FMS with a PLCThe significa

28、nt features of the FMS control system are as follows:1.The system is easy to configure and to modify to accommodate changes and updates, because of the ladder logic capability of the system.2.In a similar manner, the system is easy to program and document.3.The system can be easily maintained, and t

29、roubleshooting is decreased because on-line diagnostics are provided to pinpoint problems and decrease maintenance.4.Naturally, the system is readily interfaced with the computer.The PLC is a general purpose industrial computer which is widely used in industrial process control. It is capable of sto

30、ring instructions to implement control functions such as sequencing, timing, counting, arithmetic, data manipulation, and communication to control industrial machines and processes. The PLC is chosen to perform an FMS control task based on the following features:1) good reliability;2) less space req

31、uired and operates in an industrial environment;3) easier to maintain by plant engineer or technician;4) can be reprogrammed if control requirements change;5) can communicate and network with other computers.In this application, a GE-Series Six PLC is equipped with a memory bank, and the I/O racks a

32、re loaded with the following input and output interfaces: 120 VAC input modules with 8 ports/module, 24 VDC input modules with 8 ports/module, and 120 VAC output modules with 8 ports/module.5. PC-based visual operator interface unitWith the convergence of microprocessor technology and software techniques, the PC has become very useful in operator interface applications. PCs running MMI/DAS front-ends make powerful, intuitive operation interfaces, full of useful graphics and reporting tools. Information from these PCs can be distributed t