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RSLoop Optimizer Technical Data

RS

Loop Optimizer™ uses an intuitive software environment to develop a process model of your control loop

automatically. With this process model, you can analyze and simulate current operating conditions with the most advanced PID optimization software available. After gathering information on the dynamics of the process model, RSLoop Optimizer applies advanced analysis tools to diagnose PID loop disturbances. It then suggests optimal proportional, integral, derivative, and filtering values. These new values can be tested before you download them to your process, allowing you to predict the new loop response and compare improvements with the current settings. RSLoop Optimizer provides powerful tools to optimize your PID

Features

loops to best fit your process type. For example, your process requirements may require that a loop reach setpoint as fast as

• Includes complete RSTune feature set with additional advanced analysis tools

possible or that the setpoint never be overshot. Either way,

• Characterization tools to correct non-linear and pH loops

RSLoop Optimizer can optimize your control loop.

• Valve analysis tools to determine stiction, hysteresis, and excessive valve movement

RSLoop Optimizer includes advanced optimization tools for • Process variable and setpoint filter analysis capability

analyzing and tuning PID control loops in Allen-Bradley

• Loop interaction analysis tools

MicroLogix™, PLC-5®, SLC 500™, FlexLogix™, CompactLogix™, ControlLogix , and ProcessLogix controllers. Optimizing your ®

™

process and reducing process variability with RSLoop Optimizer

Benefits • Optimize process efficiency

improves productivity and plant efficiency.

• Reduce maintenance costs RSLoop Optimizer contains all of the functionality of RSTune , with ®

additional advanced analysis tools. For detail on functionality that is common to both products, see the RSTune Technical Data Sheet, Rockwell Automation document number TUNE-TD001C-EN-P, and the RSTune and RSLoop Optimizer Feature Comparison, document number TUNE-CP001A-EN-E.

• Improve asset utilization • Reduce time to optimize your loops from days to minutes

Advanced Analysis Tools Identify Potential Process Equipment Deficiencies The Power Spectral Density Analysis plot can help you troubleshoot product quality problems that are caused by process equipment.

This powerful frequency analysis tool graphically shows the

Reporting

relative power in the process signal at various frequencies.

RSLoop Optimizer has extensive reporting capabilities to document

Power Spectral Density Analysis identifies the frequencies

loop analyses. The default report includes information such as

at which uncontrollable disturbances are present. Given this

current and new tuning values; loop notes; the PID Tuning Grid;

information, you can examine the process and relate the process

and Process Model, Robustness, and Frequency Response Plots.

dynamics to the frequency at which the disturbances are

Reports can also be customized to accommodate your specific

occurring. Power Spectral Density Analysis has proven to be

needs. Customizable options include recording stiction, hysteresis,

extremely effective at identifying process equipment problems

linearity, Process Model asymmetry, power spectrum, and auto- and

such as worn or improperly sized pumps and valves.

cross-correlation data. Information is added through a simple menu option in RSLoop Optimizer. RSLoop Optimizer creates reports in Microsoft® Word.-C

Tools to Identify and Defeat Nonlinearity in Your System Most control loops experience non-linearity, but some control loops are so non-linear that they cannot be controlled effectively over the entire range. This results in oscillations and sluggishness at various points in the control range. The Characterizer examines the gain over the range of control and identifies the degree of non-linearity. It then guides you through a simple process for deriving the characterization parameters. The Auto Adjust feature interpolates between the process data points and adjusts the

Power Spectral Density Analysis Plot

height of the Characterizer plot. Plot the Statistical Spread of Your Data The Characterizer produces linear algorithms that you can use

The Histogram option in RSLoop Optimizer plots the statistical

in Basic, C, structured text, or X-Y plots. Copy and paste the

spread of your data. This feature displays a histogram of error,

Characterizer code into any Microsoft Windows® application for

process variable, or controller output. This plot can identify a

use as a characterizer on the output of your controller. This helps you

non-linear process or show if the loop is tuned properly.

get uniform performance across the entire range of your process. RSLoop Optimizer also supports other methods for correcting the effects of non-linearity, including gain scheduling and detuning the controller using the most sensitive running conditions. Improve pH Loop Performance pH loops can be difficult to tune because the process is inherently non-linear. RSLoop Optimizer contains a pH Linearizer that converts titration data into an algorithm that can be applied to the input of the process variable signal. This ensures that the control loop is linear over the entire range of control. This feature can also be applied to oxidation-reduction or distillation column temperature control or any other application where there is a steep slope at Histogram Showing Controller Output

the desired point of control. The pH Linearizer produces linear algorithms that you can use in Basic, C, structured text, or X-Y plots.

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Preventive Maintenance for Valves

The RRT gives an indicator of the speed of the control loop. These

RSLoop Optimizer includes valve wear indicators and a hysteresis

indicators help you improve performance of a cascading loop by

check to help you maintain and improve performance of valves.

giving you RRT targets when you set up the inner and outer loops.

Extend Valve Life and Reduce Valve Maintenance

To help you decouple interacting loops, you can adjust the safety

The valve wear indicators in RSLoop Optimizer help you predict

factor or lambda value to achieve a specific RRT factor.

and prevent valve failure. These indicators allow you to compare

Cross and Auto Correlation assist in checking loop interaction and

valve travel and direction changes to determine wear. They also

hidden cycling on complex loops. Cross Correlation can determine

compare current travel and reversal data with new values that have

if two loops are interacting with each other and causing control

been optimized by RSLoop Optimizer, and they provide quantitative

problems. Auto Correlation detects hidden cycling of the control loop.

data indicating the improvements made to the loop.

Monitor Multiple Trends and Loops

Prevent Valve Stiction Performance Degradation

Many processes include other analog values that can be affected

Performance degradation can occur from valve stiction because

by, or can affect, the PID loop. To monitor these values, you can

the controller has to overcompensate for the output. (Valve stiction

add them to the RSLoop Optimizer faceplate as trend lines. Trend

is resistance to the start of motion and is usually measured as the

lines are displayed in real time so you can monitor, tune, and

difference between the driving values required to overcome static

analyze multiple loops from the same trend interface. You can add

friction upscale and downscale.) The Stiction Wizard gives you a

as many additional trend lines as you like.

quantitative measure of stiction and determines if this resistance is

You can also add more than one loop to the faceplate, making

reducing the efficiency of your process.

decoupling and controlling complex control strategies more convenient. You can then create loops from the trends for modeling, analysis, simulation, and tuning. Another tool that helps you monitor multiple trends and loops is the Loop Summary Table, which records and organizes the results of several loop tests.

Loop Interaction and Analysis Tools Analyze Cascading, Feedforward, and Interacting Loops Cascading and interacting loops can be difficult to analyze. The Relative Response Time (RRT) and correlation tools in RSLoop Optimizer help improve the performance of these loops.

Loop Summary Table

Optimize Process Efficiency Select the Best Tuning Values How do you pick the best tuning values for a loop that requires multiple sets of PID and filtering parameters for optimal performance? For example, if you have a temperature control application for an insulated vessel that heats up more quickly than it cools down, you may want separate PID and filtering values for each direction. PID Tuning Grid showing Relative Response Time (RRT)

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To help you pick the best values, the Loop Summary Table records and organizes the results of several loop tests. New and existing values are displayed with information about their effects on the control loop, so you can pick the best options. You can also archive loop history data for each direction. You can add notes to each test in the Loop Summary Table. Stored data include PID values, model parameters, the Relative Response Time (RRT), stability index, dead time values, and the quality of frequency data fit. The Loop Summary Table logs the PID value sets separately and automatically stores associated data, such as the RRT for each entry. Adjust Filters and Evaluate Performance RSLoop Optimizer includes the Robustness Plot, the PV filter

Robustness Plot

analysis, setpoint filter analysis, performance evaluation, time-line analysis, and shrink-swell. These tools are in addition to the

PV Filter Analysis

Process Model window, the Process Frequency Response Plot,

A common method for improving loop performance is to put a filter

and the Control Loop Simulation Plot, described in the RSTune

in the process variable input. You can use RSLoop Optimizer to

Technical Data Sheet.

experiment with different filters and settings, including First Order, Second Order, Second Order Butterworth, and Moving Average. RSLoop Optimizer will automatically calculate the maximum filter value for the selected filter without degrading your process.

Process Frequency Response Plot

Quickly Change the Safety Margin

Process Variable Filtering

The RSLoop Optimizer Dial-In Robustness Plot tool allows you to change the safety margin graphically — automatically recalculating and applying the PID values you selected. Simply drag a line on the robustness plot to make adjustments.

4

Maintain Tight Control

Analyze Control Loop Time Components

If changes to setpoint result in unstable control, you might

Use Time Line Analysis to help understand the relationships

consider using a setpoint filter, especially if you need to maintain

between the time elements of each component in your control

tight, aggressive control. The Setpoint Filter Analysis optimizes

loop. The time elements are charted in an easy-to-read chart

responses to setpoint changes and load upsets by filtering the

that helps you visualize and improve the time relationships.

effect of a setpoint change.

The time elements that RSLoop Optimizer examines are: • Sample interval compared to dead time • Process variable filter time compared to the controller derivative time • Controller derivative time compared to the controller integral time • Process variable filter compared to dead time • Equivalent dead time (only for second-order process) • Relative response time (RRT) Tools for Tuning Re-Boil and Distillation Column Applications The Inverse Response (shrink-swell) helps you tune difficult level loops, such as those found in re-boil and distillation column applications. These loops can be hard to model because the introduction of more liquid briefly lowers the level. RSLoop Optimizer can optimize and help you analyze these hard-to-tune applications.

Faceplate

Judge Performance and Robustness Trade-offs

Additional Features

The Performance Evaluation Analysis shows the trade-offs

• PID tag browsing on set-up screen

between performance and robustness at a glance. The

• Remote connection to a PID loop through RSLinx® Gateway™

performance summary includes:

• Compare statistics between loops using normalization — all values

• Performance Increase: The probable improvement in reaction

are normalized between 0% and 100%

to control upsets with the new tuning value.

• Remove the effects of a process variable filter so you can see

• Robustness Increase: The percentage of robustness

the signal as if it were not filtered

improvement you can expect with the new tuning parameters.

• RSLoop Optimizer supports function block tuning in

• Valve Travel and Reversal Indices

ProcessLogix and ControlLogix controllers

• Current Relative Response Time: The existing speed of the control loop. • New Relative Response Time: The new speed of the control loop.

5

RSLoop Optimizer Integrates with Rockwell Automation’s Integrated Architecture

System Recommendations

Until now, the control systems used for process, discrete, drive,

• Microsoft Windows 98, Windows NT®, Windows 2000,

and motion applications were separate. Now, Rockwell

• Intel® Pentium® processor or greater or Windows XP

Automation’s Integrated Architecture allows manufacturers to

• Minimum of 15MB of hard disk space

integrate a plant, replacing isolated cells of activity with a single

• 256-color or higher VGA graphics adapter,

coordinated system that improves the flow of information — from

1024 x 768 recommended

the simplest sensor on the plant floor to the company’s intranet

• Any Windows-compatible pointing device

and extranet.

• If reporting function will be used, Microsoft Word 2000 or higher

RSLoop Optimizer integrates with this architecture, allowing you to

• Communications software: ProcessLogix 3.0.0 (or higher) or

optimize control loops regardless of the Rockwell Automation

RSLinx 2.3 (or higher). RSLinx packages that can be used with

control strategy platform you choose.

RSLoop Optimizer include Single Node, OEM (OPC only),

Rockwell Automation’s Integrated Architecture consists of Logix for control, the NetLinx Open Architecture for communication, and ViewAnyWare™ for visualization. The result is reduced complexity in an architecture that is easier to keep running.

Professional, or Gateway. RSLinx Lite cannot be used with RSLoop Optimizer. • OPC support: RSLoop Optimizer is an OPC client

Catalog Numbers 9323-LOOP01ENE RSLoop Optimizer PID Loop Tuner 9323-LOOP02ENE RSLoop Optimizer and RSLinx Bundle

Rockwell Software For more information on the latest pricing or a demonstration of any Rockwell Software package, please contact your local Rockwell Automation sales office or Allen-Bradley distributor. For the very latest on Rockwell Software products, visit us at:

www.software.rockwell.com

Publication LOOP-TD001B-EN-D – March 2005

Copyright © 2005 Rockwell Automation, Inc. All rights reserved. Printed in USA.