VOLUME 1, NUMBER 1 | SPRING 1998
The hardware for manufacturing applications includes various controllers: programmable logic controllers (PLCs) for equipment control; motion controllers for positioning equipment; computer numerical controls (CNCs) for various machining applications; and the operator interfaces (OIs) for all of these controllers. As individual pieces of equipment are collected and integrated into manufacturing cells, transfer lines and assembly systems, peripheral pieces of equipment are often added. It is critical that the individual controllers be fully integrated with all of the equipment. It is also critical that programming software fully supports each controller. And, for the complete system, the programming packages must integrate with the monitoring and control software that ties the entire system together. To ensure that integration is maximized, there are certain key features to look for in the controlling hardware and the supporting software.
Programmable Logic Controllers. Motion Controllers. The typical task of motion control hardware is to move product or equipment from place to place, repeatedly. To consistently achieve the same positions, speed and timing, the equipment must be extremely reliable and predictable. Motion control hardware must also be highly integrated with the servo systems they control Ð the amplifiers, servo motors and the feedback devices. Together these hardware elements act as a team to produce the required motion profiles. While the control of the positioning devices themselves is the key focus of motion controllers, they also control equipment interlocks to start and stop ancillary equipment and to support appropriate operator safety devices. Therefore, a motion control system that extensively supports I/O integration and leverages the I/O capabilities already developed for other control architecture including PLCs offers the most flexible and comprehensive solution. Computer Numerical Controls. CNCs have long been the hallmark of the industry for precision control in machining and turning applications. CNC technology has advanced and adopted many breakthroughs from other product areas, especially microprocessor technology. More powerful CNCs have adopted the 486 and Pentium¨ processors and also support additional reduced instruction set computer (RISC) add-on options to support high precision machining applications. CNCs face the challenge of combining high precision and accuracy with the flexibility and adaptability needed to properly machine a variety of parts. As do motion controllers, CNCs interface to external equipment. Interlocks, safety connections, tool changers, part loaders, and washers are examples of equipment whose I/O may be connected to the CNC. Probing devices and temperature indicators may also provide information needed for the machining cycle. Again, extensive I/O capabilities can be had by tapping the technology available through other control architecture. Operator Interface Hardware. OI hardware typically interfaces a local user to the process. OIs can be as simple as a one or two line display or as powerful as a CRT and keyboard attached to a CNC machine. One of the key features for an OI is the ability to interface to different makes and models of industrial controllers, including CNC, PLC, motion and other controllers. The OI must be easy to use so that the operator can readily monitor and control the equipment, diagnose problems and keep things running smoothly.
Integrated Software While individual software tools, such as a stand-alone PLC programming package, may be optimized for their key application, they are often difficult to use in conjunction with other software productivity tools. Many of these packages were originally developed in the DOS operating system and have not made the transition to Microsoft® Windows®. Others have moved to Windows, but have still not fully adopted the 32-bit platforms and standards that are becoming increasingly essential to today's computing environments.
Programmable Logic Controller Support. Data sharing between the PLC software and the HMI should be a built-in function, possibly using common data variables and fault table information. In the ultimate solution, the programming package and the HMI communicate to the PLC at the same time via the same communications network. Eliminating redundant configuration is the true aim of integration. Users working with "soft control" or "soft PLC" approaches face similar challenges while implementing the logic solving capabilities of a PLC using the hardware and software platform of a personal computer. The software features needed to support open architecture solutions still include program editing and broad I/O support. The runtime logic engine is a new requirement it executes under the personal computer's real-time operating -- system (Windows NT®) so the computer can switch between logic solving and providing a user interface. This is the software component that actually emulates what the PLC does in terms of logic solving. While the more basic soft PLC approaches include a limited user interface, a full function soft PLC supports a full HMI, either on the same personal computer or linked across an Ethernet network. By including Ethernet capabilities, an HMI package can collect and integrate data from multiple soft PLC systems just as it would from a variety of PLCs. Motion Controller Support. Motion control software has similar requirements and must be tailored to mirror the life cycle of a motion application from the conceptual stage through the production and maintenance phases while minimizing the time and resources required for these phases. Overall, many of the requirements are common to those of the PLCs -- intuitive graphic user environments, the ability to program the motion controller in a graphic language and compatibility with Windows 95 and Windows NT.
The more useful motion control packages allow users to create motion components as well as customize component toolbars and libraries. Icon creation and edit features let users customize their development environment. Dialog boxes and help information are also customizable in some packages. The motion control software should also be able to monitor the operation of a profile for testing or debugging and offer back-up and restore configuration folders. Computer Numerical Controller Support. A wide variety of Computer Aided Drafting (CAD) development tools allow users to design products and perform the calculations necessary to develop a part program for CNCs. The transfer of the completed part program to the controller is now via direct numerical control (DNC) instead of paper tape. With an open communications CNC, the HMI can send data and part programs and can also obtain information from the CNC. Shared information includes the part program name or number, current machine tool position data, process data from sensors and parameters. On complex machine systems, additional data may be available such as part number, pallet number, tool ID and tool life information. The HMI software can then display, log, analyze and create a single, consistent user interface across multiple CNCs and across combinations of PLCs and motion controllers as well. HMI support brings a new range of possibilities to CNC applications. Custom screens can now be readily developed and tailored to individual CNC applications: large or small part turning, manual or automatic part load stations, tool change systems and manufacturing cells and automated maintenance reporting systems. The user interface can be an integral part of the application, guiding the operator through the steps needed to manufacture parts and bringing equipment problems directly to their attention. Operator Interface Support. Operator interface (OI) software primarily configures and programs. Current operator interface hardware includes small multi-line displays, some with color, some with touch screens and some with function buttons or keypads. Since the OI has traditionally been viewed as a stand-alone user interface, its software development initially focused on ease of development features and migration to the Windows 95 and Windows NT environment. These devices generally have a look and feel that is unique to their hardware design -- typically different from a Windows-based HMI. Human Machine Interface. No longer an "add-on" to control systems, HMIs are an essential component of factory automation systems. They support the installation and commissioning of the controllers by spotting problem areas and recording test results during checkout. Once installation is complete, the HMI operates and helps the user maintain the system. The HMI acts as the higher level user interface and considered in conjunction with operator interface design and purchase decisions. The most cost-effective systems are achieved when the system is engineered and designed with both OI and HMI considered from the start. Where user interfaces are required, the HMI workstations or OI panels can be traded-off for the most appropriate form, fit and function. Whether connected to a CNC, a motion controller or a PLC, the HMI is responsible for collecting data, logging it for future action, sending new data to the controller and providing a single, powerful, consistent user interface across an entire facility and across all types of devices. Because the HMI also supports remote dial-in capabilities and extensive networking support, this data can be made available to other users in the same plant or at an equipment builder's facility. The HMI package also acts as the enterprise wide server, collecting data from a number of different process areas or zones within a facility, merging the data, and presenting it in an understandable way. While the OI and HMI may be interchangeable as local machine user interfaces, the HMI offers superior capability to bring together data from multiple controllers and HMIs. The controller support and HMI software all needs to take full advantage of the Microsoft Windows 32-bit architecture and the accompanying standards including OLE (object linking and embedding), ActiveXTM, and ODBC (open database connectivity). These tools make it possible to share data between packages so that projects are easily documented and controls can more easily integrate into a complete enterprise wide Manufacturing Execution System (MES) solution. Wizards and communication drivers that benefit each application individually become more powerful when combined. Integration between the HMI and the other software packages helps to reduce configuration efforts.
Summary The integrated software suite reduces the total project life cycle costs including designing, developing, commissioning, documenting and maintaining the system. By heavily leveraging the technology for office automation, factory automation users obtain the best of all worlds. A consistent and intuitive user interface helps minimize the training cycle because users already familiar with products like Microsoft Office are already well on their way to using factory automation products. Conforming to the Microsoft Win32 architecture simplifies integration to other application packages and makes it easier for system integrators to develop additional software of their own that can seamlessly merge with the software suite. And by using the application program interfaces provided with these packages, software developers are protected against technology changes at lower levels in the software. Integration to the hardware itself and among the hardware components is required to make a system work. Integration of the software to the hardware and among the software tools helps to make the work go quickly, smoothly and economically. Mark Anderson is the CIMPLICITY product marketing manager at GE Fanuc, Charlottesville, Va.Web Site © Copyright 2020 by Lionheart Publishing, Inc. All rights reserved. Lionheart Publishing, Inc. 2555 Cumberland Parkway, Suite 299, Atlanta, GA 30339 USA Phone: +44 23 8110 3411 | E-mail: Web: www.lionheartpub.com Web Design by Premier Web Designs E-mail: webmaster@lionhrtpub.com |