This post is an excerpt from the journal ISA Transactions. All ISA Transactions articles are free to ISA members, or can be purchased from Elsevier Press.

Abstract: Chemical plants are complex large-scale systems which need designing robust fault detection schemes to ensure high product quality, reliability and safety under different operating conditions. The present paper is concerned with a feasibility study of the application of the black-box modeling method and Kullback Leibler divergence (KLD) to the fault detection in a distillation column process. A nonlinear auto-regressive moving average with exogenous input (NARMAX) polynomial model is firstly developed to estimate the nonlinear behavior of the plant. Furthermore, the KLD is applied to detect abnormal modes. The proposed FD method is implemented and validated experimentally using realistic faults of a distillation plant of laboratory scale. The experimental results clearly demonstrate the fact that proposed method is effective and gives early alarm to operators.

Free Bonus! To read the full version of this ISA Transactions article, click here.

2006-2018 Elsevier Science Ltd. All rights reserved.

IEC 61131-3, along with PLCopen extensions and support, provides software standards essential for efficiently achieving competitive manufacturing—including implementing Industry 4.0, Industrial Internet of Things, and Internet of Things systems. The standards enable engineers to create industrial automation applications using structured modern software techniques that have been proven in the computer industry over many years to increase productivity, quality, and functionality of industrial automation systems. Another major benefit is a common base of understanding and training for application engineers and service people.

IEC 61131-3 and PLCopen standards improve every aspect of a control and automation life cycle.

Background

The IEC 61131-3 standard is supported by two groups: the International Electrotechnical Commission (IEC) and PLCopen.

International Electrotechnical Commission

IEC 61131 is an International Electrotechnical Commission (www.iec.ch) standard for industrial controllers that has seven parts. IEC 61131-3 defines programming languages. Since 1906, the IEC has been a nonprofit, nongovernmental international standards organization that prepares and publishes international standards for all electrical, electronic, and related technologies collectively known as “electrotechnology.” Eighty two countries are IEC members, and another 82 participate in the affiliate country program. The IEC is headquartered in Geneva, Switzerland, with regional centers in Asia-Pacific (Singapore), Latin America (São Paulo, Brazil), and North America (Boston).

PLCopen

The PLCopen (PLCopen.org) organization was founded in 1992 as a not-for-profit industry association of member companies committed to developing open industrial automation software standards to increase functionality while reducing engineering, training, operations, and maintenance costs. PLCopen has a vendor certification program, and certified products are listed on the organization website. PLCopen is headquartered in The Netherlands, with regional representatives in North America (www.plcopen-na.org), Japan (www.plcopen-japan.jp), and China (www.plcopen.org.cn). The website describes certifications of IEC 61131-3 compliant programming systems.  

PLCopen certification include conformance, safety, and motion control. Vendor-certified products are listed on the PLCopen website (www.PLCopen.org).

Internet of Things

Internet of Things (IoT) concepts are driving computing into edge devices, such as sensors and powerful single-chip computers, and IEC 61131-3 is suited for these embedded applications. It provides the programming standard to support implementations of IoT technology for industrial controls in automation.

Software intensive systems

Industrial automation systems are becoming software intensive, making them more flexible and feature-rich and creating the need for more efficient programming based on an integrated modular programming software standard. IEC 61131-3’s logical high-level modular programming environment increases productivity and quality. This is consistent with the evolution in the computer industry from low-level programming to higher-level modular programming. The IEC 61131-3 software programming environment is inherently self-documenting, so it is easier to perform additions and add new functions to existing systems. PLCopen functions added within the framework of the IEC 61131-3 standard continually bring new capabilities. Improving the efficiency of software development and ongoing support is important, since typically software enhancements and maintenance costs are at least twice the initial development investment of applications.

The integrated design environment to develop, simulate, and debug automation, control, and human-machine interfaces

Integrated development environment

The IEC 61131-3 development platform for building applications is an integrated design environment (IDE) for creating, simulating, and debugging applications. Using IDE applications, people build control and automation logic, define alarms, and create human-machine interface screens in one software platform. IEC 61131-3 programs developed in an IDE are downloaded into target processors where they control processes in real time. When applications are downloaded to a target controller, the IDE engineering tools include online debugging, break points, watch windows, and forcing variable functions.

Multitasking oriented

IEC 61131-3 defines a task-oriented environment that has the flexibility to meet the control requirements for any application. At the highest level, all the software required to solve a particular control problem can be formulated as a “configuration.” A configuration is specific to a particular type of control system, including the arrangement of the hardware (processing resources, memory addresses for I/O channels, and system capabilities). Within a configuration, users define one or more resources. One can look at a resource as a processing facility that can execute IEC programs. Within a resource, one or more tasks can be defined. Tasks control the execution of a set of programs or function blocks. These can be executed either periodically or upon the occurrence of a specified trigger, such as the change of a variable. Programs are built from a number of different software elements written in any of the IEC-defined languages. Typically, a program consists of a network of functions and function blocks, which can exchange data. Function and function blocks are the basic building blocks, containing a data structure and an algorithm.

Data types

IEC 61131-3 defines strong data typing to prevent programming errors (e.g., dividing a date by an integer). Common data types are Boolean, integer, real and byte and word, date, array, time of day, and string. Based on these, users can define specific data types for an application, known as derived data types. Variables are only assigned to explicit hardware addresses (e.g., input and outputs) in configurations, resources, or programs, so there is a high level of hardware independence that supports the reusability of the software. The scopes of the variables are normally limited to the organizational unit in which they are declared (e.g., local). This means that their names can be reused in other parts without any conflict, eliminating another source of error. If the variables have global scope, they have to be declared as global. Parameters can be assigned an initial value at start up and cold restart to ensure proper operation.

Programming languages

The IEC 61131-3 standard defines five languages that all can be used together and share common data types.

Instruction List

Instruction List (IL) is textual language that resembles low-level assembler programming.

Ladder Diagram

Ladder Diagram (LD) has its roots in the U.S. and is based on the graphical presentation of Relay Ladder Logic. Relay Ladder Logic is acknowledged to be the first graphical industrial automation programming method that significantly improved productivity.

Function Block Diagram

Function Block Diagram (FB) has been very common in the process industry and is now used in all applications. It expresses the behavior of functions, function blocks, and programs as a set of interconnected graphical blocks, like in electronic circuit diagrams. It looks at a system in terms of the flow of signals between processing elements. Function blocks contain algorithms and may contain data if required. The inputs and outputs of function blocks have defined data types to prevent errors in programming.

A temperature control loop, or proportional, integral, derivative (PID), is an excellent example of a function block. Once defined, it can be used over and over again, in the same program, different programs, or even different projects. This makes it highly reusable.

Function blocks can be written in any of the IEC languages. In addition, for many implementations, users can create functions with the “C” programming language. These capabilities let users create new function blocks for projects and applications to promote reuse of proven code.

Structured Text

Structured Text (ST) is a very powerful high-level language with its roots in Ada, Pascal, and “C.” It contains all the essential elements of a modern programming language, including selection branches (IF-THEN-ELSE and CASE OF) and iteration loops (FOR, WHILE, and REPEAT). All standard IEC 61131-3 functions can be used in Structured Text programming, and users can create their own function blocks for applications and projects.

Sequential Function Chart

Sequential Function Chart (SFC) describes graphically the sequential behavior of control programs and helps to decompose a control problem into manageable parts, while maintaining an overview of the execution flow. SFC consists of steps, linked with action blocks and transitions. Each step represents a particular state of the systems being controlled. A transition is associated with a condition, which, when true, causes the step before the transition to be deactivated, and the next step to be activated. Steps are linked to action blocks performing a certain control action. Each element can be programmed in any of the IEC languages, including SFC itself. One can use alternative sequences and even parallel sequences, such as those commonly required in batch applications. For instance, one sequence is used for the primary process, and the second for monitoring the overall operating constraints. Because of its general structure, SFC also provides a communication tool, combining people of different backgrounds, departments, or countries. SFC can be used to define both serial and parallel processes. Application examples include startup sequences, shutdown sequences, batch process control, and machine cycle operations.

Recent developments

Two major new developments are the addition of the PLCopen XML interchange standard and the PLCopen OPC UA standard.

XML interchange

The PLCopen XML standard provides an open, nonproprietary, software interface for the interchange of industrial and process control programs between controls, product life-cycle management, machine and process simulation, computer-aided design, documentation software, and other systems. The PLCopen XML schemas, documentation, and an introduction are available free at www.control-xml.com. The files include an explanation of the PLCopen XMLSchema, a document on XML formats for IEC 61131-3, and XML schema files. The PLCopen standard has gained acceptance by the AutomationML organization (www.AutomationML.org).

OPC UA

PLCopen jointly developed the PLC open OPC UA standard with the OPC Foundation. It includes data models to simplify the interface between controllers, control software, and business enterprise systems. The integration of data with real-time control and business information systems is done using these function blocks.

The function blocks are also defined for direct machine-to-machine communications between multiple vendor controllers to coordinate automation. These are important functions for achieving the goals of Industry 4.0, the Industrial Internet of Things, and smart factory applications to improve manufacturing efficiency and productivity. These function blocks simplify the integration of production, process control, packaging, and other machines into efficient new system architectures.

Design philosophy fundamentals

IEC 61131-3 and PLCopen standards lower the life-cycle cost of automation and control implementations with a design philosophy enabled by the standards. Engineers that leverage the standards have a great advantage when programming applications that make all aspects of the control and automation life cycle more efficient.

A version of this article also was published at InTech magazine. 

This automation industry quiz question comes from the ISA Certified Automation Professional (CAP) certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.

Which choice is NOT a major advantage of using cascade control?

a) Any disturbances that affect the slave variable are detected and compensated for by the slave controller before they have time to affect the primary control variable.
b) The controllability of the outside loop is improved because the inside loop speeds up the response of the process dynamic elements between the control variable and slave variable.
c) Nonlinearities of the process in the inner loop are handled by that loop and removed from the more important outer loop.
d) It can further improve the performance of loops that are already very controllable.
e) None of the above

Image Credit: Wikipedia

Luis Navas’ Introduction

The process depicted in Figure 1 shows a concentrator with its process inputs and outputs. I have the following questions regarding the process testing in order to generate process models for a MPC in the correct way. I know that MPC process inputs must be perturbed to allow an identification and modeling of each process input and output relationship.  

Figure 1: Variables for model predictive control of a concentrator

Luis Navas’ First Question

Before I start perturbing the feed flow or steam flow, should the disturbance be avoided or at least minimized? Or simply let it be as usual in the process since this disturbance is always present?

Mark Darby’s Answer

If it is not difficult, you can try to suppress the disturbance. That can help the model identification for the feed and steam. To get a model to the disturbance, you will want movement of the disturbance outside the noise level (best is four to five times). If possible, this may require making changes upstream (for example, LIC.SP or FIC.SP).

Luis Navas’ Second Question

What about the steam flow? Should it be maintained a fix flow, (FIC in MAN with a fix % open FCV), while perturbing the feed flow and in the same way when perturbing the steam flow, should the feed flow be fixed? I know some MPC software packages excite its outputs in a PRBS (Pseudo Random Binary Sequence) practically at the same time while the process testing is being executed, and through mathematics catches the input and output relationships, finally generating the model.  

Mark Darby’s Answer

Because the steam and feed setpoints are manipulated variables, it is best to keep them both in auto for the entire test. PRBS is an option, but it will take more setup effort to get the magnitudes and the average switching interval right. An option is to start with a manual test and switch to PRBS after you’ve got a feel for the process and the right step sizes. Note: a pretest should have already been conducted to identify instrument issues, control issues, tuning, etc. Much more detail is offered in my Section 9.3 on in the McGraw-Hill handbook Process/Industrial Instruments and Control Sixth Edition.

Luis Navas’s Last Questions

What are the pros & cons for process testing  if the manipulated variables are perturbed through FIC Setpoints, (closed loop), or through FIC Outputs, (open loop)? Or simply: should it be done according with the MPC design? What are the pros & cons if in the final design the FCVs are directly manipulated by the MPC block or through FICs, as MPC’s downstream blocks? I know in this case the FICs will be faster than MPC, so I expect a good approach is to retain them.

Mark Darby’s Answers

Correct – do according to the MPC design. Note sometimes the design will need to change during a step test as you learn more about the process. Flow controllers should normally be retained unless they often saturate. This is the same idea for justifying a cascade – to have the inner loop manage the higher frequency disturbances (so the slower executing MPC doesn’t have to). The faster executing inner loop also helps with linearization (for example, valve position to flow).  

Batch process manufacturers are continuously looking for new ways to improve processes and production techniques and to be more efficient to remain competitive. Although manufacturers see new technologies as a key to improving their operations, there is a mindset shift occurring about the role those technologies should play. Rather than trying to make a batch process fit the available technology, manufacturers want batch systems to have flexibility and options to better fit and adapt to the needs of the process.

Modern batch systems, which incorporate technology advances and new capabilities, can help industrial producers do just that. As batch users in the food and beverage, pharmaceutical, and chemical industries seek to implement or modernize their existing batch systems, the three core capabilities they should look for in their new control and information technology are mobility, enhanced controller integration, and information-enabled decision making.

Mobility

Traditional batch systems use server-client thick architectures, with user interfaces that are stationed either close to the production line or in a control room. As a result, workers always need to be at those interfaces to make or approve any supervisory changes, or to troubleshoot and resolve production issues.

This can be especially cumbersome in large process-control operations that contain multiple lines or multiple facilities. There is an inherent productivity cost and lost opportunity when the workforce is spread out and forced to walk large distances because of the constraints of legacy platforms.

For instance, production can come to a standstill while a supervisor is sought out and then brought to a station to approve an action, such as starting a new batch or making a recipe parameter change. Likewise, a downtime event or product changeover can last longer than necessary simply because of the time spent waiting for a technician to arrive.

A batch system with mobile capabilities frees workers from these time-draining activities. A mobile platform allows operators, supervisors, and maintenance technicians to perform a range of actions—such as running schedules, viewing logs, and troubleshooting diagnostics—from a mobile device regardless of their location. This reduces steps and improves workflows in batch operations to keep production running and minimize downtime.

Also, mobile solutions must be easy to implement and offer the same control and security as traditional control methods. A mobile solution should not be a simple display of a traditional human-machine interface on a mobile device. The wide array of devices, operating systems, and sizes calls for an adaptable interface with consistent usability in all applications.

Enhanced controller integration

In many cases, there has been a shift to place custom-batch sequences in the controller, but a modern batch system should provide flexibility regardless of the infrastructure. Depending on a facility’s specific architecture and process needs, the correct solution could be controller-based, server-based, or a combination of the two.

Bringing batch operations to the controller—and closer to a process—can be especially useful in critical applications, where close control of equipment or batch processes must be maintained. A bio reactor or tire rubber mix, for example, may have transition speeds between phases that are too fast for a server. And a simple server disconnect could cause a lost batch and cost the company hundreds of thousands or even millions of dollars.

Maintaining a server-based solution is also a key component of modern batch solutions. Managing large, complex batch operations is best performed in a supervisory system independent of the controllers. A server-based batch solution provides a layer of security and incorporates visualization capabilities that are required to fully contribute to a connected batch enterprise. As process control solutions continue to become more integrated with manufacturing execution systems, warehousing, and enterprise resource planning systems, it is important to incorporate a batch-management server as a major component within the infrastructure, so there are more options for future integration, connectivity, and scalability across large facilities.

A modern batch system truly differentiates itself by easily allowing server-based and controller-based architectures to work together and create a unified user experience. Consider the example of a clean-in-place skid for a pharmaceutical operation. Traditionally, end users receive the skid from the equipment builder and then have to reprogram it for integration with the batch control system. Not only are the end users paying for unused engineering, but they also have to spend additional time rewriting the skid’s code and redoing the testing and commissioning. Building the batch operation into the controller eliminates the need to rewrite coding, because the skid can be seamlessly integrated into the larger control system. This helps end users reduce startup and commissioning times by as much as two months, while also minimizing or even eliminating redesign and engineering costs.

Information-enabled decision making

Modern batch software allows end users to configure, view, and obtain batch-sequence data stored in the controller. This increases visibility and accessibility to all stages of production. In a connected enterprise, batch and process data can be seamlessly shared via industrial-process and enterprise systems to support better decision making at all levels of an organization.

Campari, the Italy-based spirits giant, saw an opportunity for using its data at a new processing and bottling facility that was recently constructed for its iconic Wild Turkey bourbon. The 144,000-square-foot facility houses approximately 40 tanks, as well as three high-speed automated bottling lines and one manual bottling line.

Campari implemented a modern process batch system for ingredient receipt, batch management, and control across the processing operations. The company coupled this system with a visualization software that allows operators to monitor the flow of spirits down to the gallon. Operators can use this information to track production and make reports for regulatory purposes.

In the 10 months from the opening of the new facility to when it became fully operational, operational equipment effectiveness (OEE) increased from 10 to 20 percent to approximately 70 percent. Despite this significant improvement, the operations team set its sights even higher with the goal of reaching a best-in-class OEE performance level of 85 percent.

“The system has helped us get better and better every day with regard to our processing, bottling, and material-handling operations,” said Wayne Knabel, packaging director for Wild Turkey. “Our KPIs [key performance indicators] are all trending up, and our cost per case is going down.”

Of course, with greater connectivity and information sharing across an enterprise come new security risks. Batch end users must keep this in mind when specifying and selecting a batch control system. New control technologies, for example, are developed using a design-for-security philosophy, in which quality, resiliency, and operational integrity are built into the product.

Improving systems and empowering users

Batch manufacturers today are under pressure to increase production performance, achieve faster product changes and turnovers, and improve yields, while at the same time meeting quality, safety, and compliance goals. As a result, they are looking for more innovative batch systems that go beyond a satisfactory compliance experience.

Modern batch systems can help address these challenges by providing faster, more reliable control and by empowering workers through smarter, more responsive decision making.

A version of this article also was published at InTech magazine.

This automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for more information about the CCST program.

A flow metering device comprised of a body, flow straightener, hub, bearing, rotor, and pickup is called a:

a) vortex shedding flowmeter
b) magnetic flowmeter
c) parshall flume
d) turbine flowmeter
e) none of the above

This post is an excerpt from the journal ISA Transactions. All ISA Transactions articles are free to ISA members, or can be purchased from Elsevier Press.

Abstract: This article presents the development of inferential control scheme based on adaptive linear neural network (ADALINE) soft sensor for the control of fermentation process. The ethanol concentration of bioreactor is estimated from temperature profile of the process using soft sensor. The prediction accuracy of ADALINE is enhanced by retraining it with immediate past measurements. The ADALINE and retrained ADALINE are used along with PID and 2-DOF-PID leading to APID, A2PID, RAPID and RA2PID inferential controllers. Further the parameters of 2-DOF-PID are optimized using non-dominated sorted genetic algorithm-II and used with retrained ADALINE soft sensor which leads to RAN2PID inferential controller. Simulation results demonstrate that performance of proposed RAN2PID controller is better in comparison to other designed controllers in terms of qualitative and quantitative performance indices.

Free Bonus! To read the full version of this ISA Transactions article, click here.

2006-2018 Elsevier Science Ltd. All rights reserved.

Understanding the difficulties of batch processing and the new technologies and techniques offered can lead to solutions by better automation and control that offer much greater increases in efficiency and capacity than usually obtained for continuous process. Industry veteran and author Greg McMillan discusses analyzing batch data, elevating the role of the operator, tuning key control loops, and setting up simple control strategies to optimize batch operations. The presentation concludes with an extensive list of best practices.

This automation industry quiz question comes from the ISA Certified Automation Professional (CAP) certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.

Which of the following temperature measuring elements/devices measures temperature as the result of an electromotive force being generated that is proportional to a temperature difference (Seebeck effect) between two dissimilar, joined metals?

a) RTD
b) bimetallic expansion thermometer
c) thermocouple
d) IR thermometer
e) none of the above

Image Credit: Wikipedia

What a great event ISA recently conducted in Montreal, Canada! We held our Annual Leaders Conference (ALC), previously known as the Fall Leaders Meeting (FLM). It was so exciting and fulfilling spending time with our dedicated ISA staff and volunteer leadership teams. Attendance was great, with many new faces present. And, of course, all enjoyed the excitement and splendor of this year’s Honors & Awards Gala. (Click here to watch video!)

Immediately following was ISA@Montreal 2018, the Society’s new multi-dimensional automation conference sponsored jointly by the ISA Food and Pharmaceuticals, Automatic Controls and Robotics, Construction and Design, and Process Measurement and Control Divisions.

At the beginning of the ALC, I had the good fortune of meeting with new leaders and first-time attendees. On hand were 35 new ISA leaders from sections and divisions across three continents, including members of five ISA student sections. The passion and commitment these young people exhibited were clearly evident in our interactive discussions. I came away encouraged and enthused about the future of our Society and the automation profession. To further cultivate interest in ISA among student sections at technical institutes and colleges, ISA is in the early stages of an outreach initiative to student advisors.

The ALC also provided a great opportunity for several important subset meetings, including gatherings of the Council of Society Delegates and the Standards & Practices (S&P) committees. The work of our Standards and Practices committees are essential in our continuing efforts to improve the security, safety, and efficiency of automation and advanced manufacturing of tomorrow and well into the future.

The Council of Society Delegates (CSD) meeting had 73% of ISA eligible sections represented by a delegate. These delegates represented more than 80% of the eligible votes. The four motions on the agenda were all approved. These motions pave the way for the following actions/changes.

1. A dues increase of 10 USD per professional member. In some countries the dues increase will be reduced to 5 USD.
2. Nominations for the ballot for elected leader petition will now be accepted by petition of any combination of at least five current and past Executive Board members or Society Vice Presidents who are in good standing.
3. Any member, regardless of membership grade, is now eligible to hold elected office.
4. The Executive Board can suspend a member if there is good and sufficient cause. The suspension can be appealed to the Council.

The ALC was also a time to recognize volunteer and industry leaders. It was humbling to meet the honorees who have done so much for our industry and profession. These are the people who contribute so much of their time and talent to develop high-value ISA content, including standards and best practices. They help develop our training and certification programs and help create world-class events. As an automation professional, I and the Society will always be grateful. Thank you for all you do for ISA and our great profession.

To ensure the long-term health of our Society and profession, we need to continue to develop the next generation of ISA leaders. The Society needs you to step up to a leadership role within your section, district, division, or committee.

ISA can benefit greatly from the knowledge and expertise you’ve gained in your chosen field.  Serving as an ISA leader can significantly advance career and professional development. It’s a great opportunity to gain vital leadership skills and experiences.

While we are fortunate to have great leaders and contributors for 2019, we need to encourage more of those to raise their hands and get involved. (Nominations for our 2020 elections will be open in the early days of 2019.) Many of our elected positions are uncontested. Moreover, for 2019, there were only three candidates outside of North America and only one woman. Leadership development and continuity remains one of our most significant long-term challenges.

Our Board is focused on positioning the Society for future success and relevance. If we want to become more globally viable and reach out to younger and more diverse automation professionals, we have to find a way to attract these groups to the Society and to the automation profession as a whole. 

I have no doubt, there will be some obstacles and wrong turns along this road, but we have created a continuous improvement culture that sets a framework for sustainable growth and value for members, automation professionals, and customers.

All of us need to work together to keep the Society focused on achieving its critical objectives. If we work as a team and stay actively engaged, we’re sure to keep the positive energy going.

In closing, I would like to send best wishes to all as we approach the Thanksgiving season and hope that your family and the ISA family have a peaceful and enjoyable Thanksgiving celebration.

A version of this article also has been published at ISA Insights.