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For OEM engineers and programmers to avoid the long hours and aggravation that can come from such situations as standard deviation, lack of specifications or inefficient approaches, they may want to consider implementing one of these tips per month.
Shorter time spent in the development stage translates into lower engineering costs and faster time to market. For OEM engineers and programmers to avoid the long hours and aggravation that can come from such situations as standard deviation, lack of specifications or inefficient approaches, A-B Journal (PDF) suggests they implement change in one or more of the following 10 key areas:
1. Descriptions and Specifications
Develop functional descriptions and functional specifications. Well-written instructions define the goals of a project from the small details of how to achieve the goals (i.e., functional specification) all the way up to a high-level point of view (i.e., functional description). As systems become more complex and interconnected, these written documents become vital.
Do not forget fault handling, as a determined-upfront outline of the fault procedures helps prevent the issue from rearing its head later in the project.
2. Functional Models
Develop functional models for applications with critical algorithms. Many applications involve critical algorithms in the form of complex math or complex decision logic. "Using Microsoft Excel, Math CAD, SolidWorks or any flowchart tool to model the algorithms helps clarify the complex processes," A-B Journal suggests.
3. Appropriate Architecture
Choosing an appropriate control architecture that will keep the design simple is a beneficial consideration during design. "From controllers and networks to peripheral devices and operator interface, making decisions purely on the lowest procurement costs may cause problems down the road" says A-B Journal.
It is also important to look for similar built-in communication capabilities. Choosing devices that use the same protocol can save time and eliminate aggravation.
4. Modular Programming
Recognize the differences between supervisory networks and I/O networks, and choose appropriately. As manufacturers continue to push forward into information-enabled systems, it is important to recognize and understand the different uses of such networks.
For instance, supervisory networks typically are well suited for communicating information from the plant floor to higher-level systems, and I/O networks pull data in and actuate things at the machine level.
I/O and supervisory network processes are opposed to each other, so if all processes are running on the same network, one could easily impair another.
5. Segmented Programming
Keep programming for control separate from programming for information sharing. Today’s information-enabled systems make it critical to define what a program does to control equipment versus what it does to gather and send information to a higher level. If your control and information programming are not segmented properly, one can have a notably negative impact on the other.
Users should prioritize control and information functions, and they should ensure that control functions meet critical time requirements and that lower-priority functions (e.g., separating information) are moved to a lower-priority process.
6. Supervisory Versus I/O Networks
Modular programming allows manufacturers to set up an application so the code for various functions is self-contained. For example, the code controlling overall application execution should be isolated from the code controlling specific low-level functions within the application.
7. Structured Data
Use structured data. Although many believe PLCs and control applications are code-centric, most if not all are actually data-centric. In fact, everything that goes on inside a PLC has data behind it. Every decision, every input is data, and every output is data-driven. As a result, data should be structured to coordinate with its functionality.
8. Fully Utilized GUIs
Usually, the graphical capabilities of today’s powerful Graphical User Interfaces (GUIs) go unnoticed, while text and numeric fields are used to add variables or extract information. However, fully utilizing the graphical capabilities to post pictures of each variable is a much more intuitive use of the GUI.
Although all true GUIs have graphical capabilities, according to A-B Journal, the capabilities aren’t being leveraged mostly due to the fact that it’s easier for OEMs to simply drop in text fields as they’re used to doing. OEMs may not be willing to invest the extra time up front to build a graphical interface.
Further, make sure the GUIs are modular and do not overlap screen usage with multiple functions.
9. Modular Programming
It is good practice to display as much information as possible in the most useful way. Status and fault information is extremely valuable to operators, maintenance personnel and plant management, as it can have a big impact on uptime during the long-term life cycle of a machine.
To display status and fault information, OEMs must choose an architecture with good interconnectivity with the operator interface.
10. Project Management
Use project management software to organize the design. Many documents, programs, configuration profiles and revisions are generated during project design. Project management software tools are available to help manage the large quantities of information and provide revision control to track who modified what, when and for what reason.
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