After further research, I could find no reason not to leverage Server 2012 on the new primary domain controller. I checked with the primary control vendor supporting this particular customer, and they saw no reason not to use Server 2012 on the primary domain controller. I went a step further and checked with colleagues on their experiences with the differences between Server 2008 R2 and Server 2012. Since there were no issues identified, I recommended the customer move forward with purchasing and installing this new platform as the primary domain controller for their plant control system. The customer ordered the new server hardware and their IT department purchased their first volume license of Server 2012 standard.

The experience of installing Server 2012 was very similar, if not the same as installing Windows 8 Professional. At the end of the installation, I was surprised to see the start button had disappeared as it had with Windows 8 Professional. With Server 2012, all of the applications are the desktop type, all neatly organized on the start screen based on which roles you assigned to the server (see graphic). On previous versions of Microsoft Server these were inadvertently buried in other submenus and took some digging to find.

This seems to be much more intuitive to use then the start screen that Windows 8 Professional has. I would also like to note that promoting the server to a domain controller was much more automated than previous Server versions, and it added the supporting roles necessary for the domain controller to function properly. Any additional help that I needed was easily found at Microsoft’s support site, or by simply doing an internet search. The other new feature that I found was the new Server Manager’s Dashboard. This makes it very easy to monitor any status and / or issues with any of the roles the server, or servers within a group are providing (see graphic).

During the deployment, the new domain controller computers throughout the plant were joined to the domain with no problems. The plant control system computers contained the following operating systems: Windows XP Professional, Windows 7 Professional, and Server 2008 R2.

This experience should highlight the fact that even though many of our prominent control vendors do not support the latest operating systems that Microsoft releases, this does not mean that supporting systems cannot use the latest Windows operating system available in supporting roles. This not only provides added value for the customer, but also allows us to become proficient on the latest software available. You too can be classified as an early adopter, even if you are working with legacy control software.

This post was written by John Boyd. John is a technology leader at MAVERICK Technologies, a leading system integrator providing industrial automation, operational support, and control systems engineering services in the manufacturing and process industries. MAVERICK delivers expertise and consulting in a wide variety of areas including industrial automation controls, distributed control systems, manufacturing execution systems, operational strategy, and business process optimization. The company provides a full range of automation and controls services – ranging from PID controller tuning and HMI programming to serving as a main automation contractor. Additionally MAVERICK offers industrial and technical staffing services, placing on-site automation, instrumentation and controls engineers.

The post Should You Be An Early Adopter Of Microsoft Server 2012 For Today’s Control Systems? appeared first on MAVERICK Ideas.

Last week we started with proportional. Now let’s look at the next part of the equation, the integral component:

The most striking (and scariest) part of this equation is the big integral sign in the middle. If you’ve had high school calculus, you think to yourself, “I’ve got this. Integrals don’t scare me. I just need to find the area under the curve from time zero to time t of the error function.”

But, this is the real world. What is time zero? How do I integrate an error function? The good news is that the real definition is much simpler than calculus. What the PID function does is take a portion of the error and adds it to a running total. This running total, sometimes called reset, is added to the output. Since reset increases or decreases a little at a time, it adjusts the output of the valve incrementally each scan.

For a PI controller, the two factors that we have covered so far are K_p and K_i, but if you look at the faceplate for most industrial systems, there is only one K (gain) that has no units, and a τ_i (integral time constant) designated as seconds or minutes per repeat. So, a little translation is required. Most industrial controllers don’t use the independent form of the equation shown above. Instead, they use the dependent form of the equation:

The K is typically the same as the proportional gain, K_p.  The factor τ_i determines how much of the error is going to be applied to the accumulated reset on each scan. So in the big mathy equation, K_i can essentially be replaced by the faceplate parameters:  K⁄τ_i.

What’s important to understand from this is that the gain that affects the proportional action of a controller also affects the integral action. But, the integral time constant τ_i only affects the integral action.

In pseudo code this would look like:

Error := Setpoint – ProcessValue;

Reset := Reset + K/tau_i * Error;

Output := K * Error + Reset;

The unit’s minutes per repeat for the integral time constant τ_i  comes from the fact that if the error stays constant, that is how long would it take for the integral accumulator to repeat the proportional change in output.

Note: Another way of specifying the integral tuning parameter is in seconds, and then it is the reciprocal of seconds per repeat. If the integral time constant is in seconds, the bigger the number, then the slower the response. If the integral is in seconds per repeat, the opposite is true.

Derivative

Now let’s look at derivative:

Again, this is another mathy looking equation with a simple explanation. The mathy definition first, the output will be changed by the derivative (or rate of change) of the error function. What this means is that the output will be affected by the change in error from one scan to another. Adding this to our pseudocode gives us:

Error := Setpoint – ProcessValue;

Reset := Reset + K/tau_i * Error;

Output := K * Error + Reset + (PreError * K/tau_d);

PreError := Error;  //Save the error for the next scan

What is intended is for the output to change as soon as the process variable begins to move either toward or away from the setpoint. What results can be a very quick response to a change in error from one scan to another.

The intention of derivative action is to respond to changes as they begin to occur. For example, if a temperature is starting to rise, the valve will begin to open as soon as it sees the change instead of waiting for it to cross a setpoint. This can result in a very rapid response to a small change. This rapid response can become unstable if there is noise in the process variable or on a setpoint change. So, the derivative action is often filtered separately and is sometimes calculated on PV only to ignore setpoint changes.

Summary

So now we have reviewed the three components of the PID algorithm. One way they have been described is in terms of the flow of time. P depends on the present error, I on the accumulation of past errors, and D on the prediction of future errors based on current rate of change.

This post was written by Scott Hayes. Scott is a senior engineer at MAVERICK Technologies, a leading system integrator providing industrial automation, operational support, and control systems engineering services in the manufacturing and process industries. MAVERICK delivers expertise and consulting in a wide variety of areas including industrial automation controls, distributed control systems, manufacturing execution systems, operational strategy, and business process optimization. The company provides a full range of automation and controls services – ranging from PID controller tuning and HMI programming to serving as a main automation contractor. Additionally MAVERICK offersindustrial and technical staffing services, placing on-site automation, instrumentation and controls engineers.

The post PID Math Demystified (Part 2) appeared first on MAVERICK Ideas.

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• Bill R. Hollifield, principal alarm management and HMI consultant at PAS
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Most process control engineers have been exposed to the basic equation in a form that looks something like this:

More than you want to swallow in one bite? Let’s break this down into the major components:

 
Output: u(t)  is the output of the controller at the end of the scan. If the output of the controller is a valve, then the output is the valve position that the controller is requesting after it has seen the inputs. In most controllers, this is actually the change in output from 50%. So if u(t) = 0 then the valve output is 50%; if u(t) = 1 then the valve output is 51%; and if u(t) = -2 then the valve output is 48%. You get the idea. But what’s important is that it’s not a change in output from the previous scan, but a new output.

Proportional

K_pe(t) is the proportional component, the P in PID. If you have a controller configured as proportional only, this is it. So let’s look at how this works.

Let’s start with my own misconception of how I thought it worked. When I imagine a controller, I picture myself turning a valve while watching a gage. I look at the gage, decide if I need more or less, turn that valve a little more or a little less, and then repeat the process until the gage shows the value I want. That sounds fundamentally logical, but it is not how a proportional only controller works. It’s more like if I were to look at the gage, subtract what it reads from what I want it to read, and then take that error over to a chart to look up a new value for the valve.

e(t) usually called error, is simply the difference between the setpoint and the process variable. It is the difference between where you are and where you want to be, right now, at this instant.

K_p gain, is a factor that is multiplied by the error to give you the new output, the new valve position. It’s that simple. The error at that instant of the scan is calculated and the new output is calculated.

Let’s look at an example of pseudo code to explore how this works:

Error = Setpoint – ProcessValue;

Output = K * Error;

This control algorithm is deceptively simple, yet it gives an immediate response to a setpoint change or a disturbance in the process. And if K is set correctly, will quickly move the process toward the setpoint. But, it won’t get the process to the setpoint because there has to be some error if the output is anything other than 50%.

Note: On some systems (though not often in modern systems), gain is expressed as proportional band. Proportional band is defined as the amount of change in the controlled variable required to drive the loop output from 0 to 100%. To convert between the two, gain = 100/PB.

Next week: Understanding I and D.

This post was written by Scott Hayes. Scott is a senior engineer at MAVERICK Technologies, a leading system integrator providing industrial automation, operational support, and control systems engineering services in the manufacturing and process industries. MAVERICK delivers expertise and consulting in a wide variety of areas including industrial automation controls, distributed control systems, manufacturing execution systems, operational strategy, and business process optimization. The company provides a full range of automation and controls services – ranging from PID controller tuning and HMI programming to serving as a main automation contractor. Additionally MAVERICK offersindustrial and technical staffing services, placing on-site automation, instrumentation and controls engineers.

The post PID Math Demystified (Part 1) appeared first on MAVERICK Ideas.

In today’s complex automation environments, decisions made and actions taken in one area, such as migrating to a new technology, can sometimes have adverse and unforeseen affects in others, ranging from higher total cost of ownership to concerns over employee training and plant safety.

Organizations that take an integrated approach to process management and operational improvement—one that proactively incorporates the needs and requirements of safety, people, business, and technology—are more capable of fully leveraging the great power of automation and achieving positive, predictable results in all areas.

Now more than ever before, YOU, the automation professional, directly influence the optimization, sustainability and net profitability of your plant in a measureable way. It doesn’t take super-human abilities to be a key performer and ensure that your decisions in the workplace will boost your company’s bottom line. It takes knowledge and skill.

That’s exactly what you’ll get at ISA Automation Week’s education conference—a modern, enlightened look at new and traditional aspects of manufacturing. You’ll get all the applications-based teaching you’ve come to expect, along with critical insights on how today’s essential operating factors—safety, people, business and technology—affect you every day on the job.

As the 2013 Automation Week Program Chair, I invite you to join leading automation and control experts, authors, innovators, thought leaders, and peers at the ISA Automation Week conference. Explore six educational tracks in relation to meeting the demands of four essential operating factors: safety, people, business and technology.

To help you achieve your own career objectives and drive your company’s financial success, we’ve worked hard to infuse the conference sessions with a fresh perspective, and a holistic view of automation. Your company and other manufacturers must not only invest in automation to survive in an increasingly competitive global economy, but must also invest wisely, using a top-down approach to identify and execute automation projects with the highest and quickest returns.

If you want to network with the “who’s who” of the automation profession, gain knowledge that you can apply now from renowned industry experts—and have some fun along the way—join me in Nashville for ISA Automation Week 2013. It’s the future of automation—TODAY.

I believe it’s critical for all manufacturers in every sector to think about automation as a driver of business goals. I recently published a white paper on how companies who adopt this strategy can position themselves for success. You can download the white paper here: mavtechglobal.com/latest-thinking/white-papers.

Manufacturers, are you up to the challenge?

Join me for Automation Week and help restore competitiveness in your manufacturing operation. See you in Nashville.

The post Automation Week: The Future of Manufacturing is in Your Hands appeared first on MAVERICK Ideas.