Application frameworks aid complex control system programming

Control system software is getting more complex. Controllers have faster CPUs and are increasingly networked, creating a whole new level of system complexity. To create software for these complex, distributed systems, software developers are starting to use application frameworks, which are domain-specific software architectures.

02/01/2001


Control system software is getting more complex. Controllers have faster CPUs and are increasingly networked, creating a whole new level of system complexity. To create software for these complex, distributed systems, software developers are starting to use application frameworks, which are domain-specific software architectures. Frameworks include design templates, tools, and ready-to-use components that require less set up.

Several commercial frameworks target particular application domains. For instance, frameworks for telecommunications switches, Java-based graphical user interfaces, distributed e-commerce (JavaBeans), expert systems, and others are available.



In high-level work cell architecture, subsystems are represented by
components interconnected with programming interfaces. Implementation
of the robot component includes both state machine logic and data flow
programming constructs.

Simplify with subsystems

In control systems, event and continuous processing are tightly integrated. An application framework requires two different programming constructs: cyclical-data processing (such as feedback control loops) and event-driven logic (such as error handling and start-up sequences). The framework must make it simple to efficiently program, design, and integrate these constructs.

To manage complexity of large control systems, its software system must easily break down into recognizable subsystems. The framework must encourage a hierarchical, object-oriented design with well-defined interfaces. For instance, first-tier objects can be controllers and devices. After that, complex devices can subdivide into subsystem objects, continuing the process, until it makes sense to define the functionality of each object. Over time, as the team develops standardized interfaces between objects, they can be reused.

For example, the diagram (below, left) outlines a simplified robotic work-cell controller. With an application framework, the system can be divided into subsystem objects that include robot, vision system, graphical interface, and the cell controller. These subsystems can use a network to synchronize activities and pass data.

Defining objects, behavior

Drilling down into the robot, high-level state machine control logic and cyclical data processing objects are defined. Further down in the object hierarchy are defined the implementation of event and continuous functionality of the robot controller.

This example was developed with an application framework called ControlShell from Real-Time Innovations (Sunnyvale, Calif.). ControlShell combines graphical programming diagrams for both cyclic processing and event-driven behavior.

Cyclic blocks in the diagram can be implemented as sub-diagrams, C++ object-oriented code, or even dynamic systems in Simulink from MathWorks (Natick, Mass.). Event-driven behavior is implemented in UML (universal modeling language)-style statechart diagrams.

Both types of diagrams are integrated into objects called Composite Object Groups (COGs), which provide intuitive building blocks for more complex systems. All the objects can be stored as components in a repository for future reuse.

By breaking complex systems into reusable subsystems, object-oriented application frameworks reduce system complexity. They also focus on constructs that fit the domain and let engineers think intuitively; provide structure that speed designs and coordinate teams; and enable reuse that produces more-reliable code in less time.

For more information, visit www.rti.com or www.controleng.com/freeinfo .


Author Information

Brett Murphy, vp, Real-Time Innovations; e-mail comments to gmintchell@cahners.com




No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Integrated mobility; Artificial intelligence; Predictive motion control; Sensors and control system inputs; Asset Management; Cybersecurity
Big Data and IIoT value; Monitoring Big Data; Robotics safety standards and programming; Learning about PID
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Big Data and bigger solutions; Tablet technologies; SCADA developments
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me