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LabWindows TM /CVI TM PID Control Toolkit User Manual LabWindows/CVI PID Control T oolkit User Manual May 2008 371685C-01.
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© National Instruments Corporation v LabWi ndows/CVI PID Contro l Toolkit User Manual Contents About This Manual Conventions ............ .............. .............. ........... .............. ............... .............. .............. ....... v ii Related Documentation .
Contents LabWindows/CVI PID Control Toolkit User Manual vi ni.com Converting between Percentage of Full S cale and Engineering Units ........... 3-9 Using PID on Real-Time (RT) Targets ......................... .............. .............. ...... 3-10 Using PID with DAQ Devices .
© National Instruments Corporation vii LabWi ndows/CVI PID Contro l Toolkit User Manual About This Manual The LabWindows/CVI PID Contro l Toolkit User Manual descri bes the PID Control T oolkit for LabWindo ws ™ /CVI ™ . The manual describes the features, functions, and operation of the toolkit.
© National Instruments Corporation 1-1 LabWin dows/CVI PID Control T oolkit User Manual 1 Over view of the PID Control T oolkit This chapter describes how to install the toolkit and describes Proportional-Integral-Deriv ati ve (PID) control applications.
Chapter 1 Overview of th e PID Control T oolkit LabWindows/CVI PID Control T oolkit User Manual 1-2 ni.com Activation Instructions The first time you launch LabWindo ws/CVI after installing the PID Co ntrol T oolkit, you are prompted to activ ate the toolkit.
Chapter 1 Overview of th e PID Control T oolkit © National Instruments Corporation 1-3 LabWin dows/CVI PID Control T oolkit User Manual PID Control Currently , the PID algorithm is the most comm on control algorithm used in industry .
© National Instruments Corporation 2-1 LabWin dows/CVI PID Control T oolkit User Manual 2 PID Algorithms This chapter explains the f ast PID, precise PID, and autotuning algorithms.
Chapter 2 PID Algorithms LabWindows/CVI PID Control T oolkit User Manual 2-2 ni.com Implementing the PID Algor ithm with the PID Functions This section describes how the PID Control T oolkit fu nctions implement the fast (positional) PID algorith m. The f ast PID algo rithm is th e default algorithm used in the PID Control T oolkit.
Chapter 2 PID Algorithms © National Instruments Corporation 2-3 LabWin dows/CVI PID Control T oolkit User Manual Output Limiting The actual controller output is limited to the range speci fied for control output, as fo llows: and The follo wing formula sho ws the prac tical model of the PID controller .
Chapter 2 PID Algorithms LabWindows/CVI PID Control T oolkit User Manual 2-4 ni.com The Precise PID Algorithm This section describes how the PID Control T o olkit functions implem ent the precise PID algorithm.
Chapter 2 PID Algorithms © National Instruments Corporation 2-5 LabWin dows/CVI PID Control T oolkit User Manual T rapezoidal Integration T rapezoidal integration is used to a void shar p changes in integral action when there is a sudden change in the PV or SP .
Chapter 2 PID Algorithms LabWindows/CVI PID Control T oolkit User Manual 2-6 ni.com Figure 2-2 illustrates the auto tuning procedure excited by the setpoint relay experiment, which connects a relay and an e xtra feedback si gnal with the SP . Noti ce that the PID Library autotuning functions directly implement this process.
Chapter 2 PID Algorithms © National Instruments Corporation 2-7 LabWin dows/CVI PID Control T oolkit User Manual Table 2-2. T uning Formula under P-Only Control (Normal) Contr oller K c T i T d P 0.2 K u — — PI 0.18 K u 0.8 T u — PID 0.25 K u 0.
Chapter 2 PID Algorithms LabWindows/CVI PID Control T oolkit User Manual 2-8 ni.com Note During tuning, the process remains under closed-loop PID control . It is not necessary to switch off the e xisting controll er and perform the experiment under open-loop conditions.
© National Instruments Corporation 3-1 LabWin dows/CVI PID Control T oolkit User Manual 3 Using the PID Control T oolkit This chapter contains the basic information you need to design a control strategy using the PID Control T oolkit functions.
Chapter 3 Using the PID Control T oolkit LabWindows/CVI PID Control T oolkit User Manual 3-2 ni.com T uning Controllers Manually The following controller tuning procedures are based on the work of Zi .
Chapter 3 Using the PID Control T oolkit © National Instruments Corporation 3-3 LabWin dows/CVI PID Control T oolkit User Manual Open-Loop (Step T est) T uning Procedure The open-loop (step test) tuning procedure as sumes that you can model an y process as a first-order lag and a pure deadtime.
Chapter 3 Using the PID Control T oolkit LabWindows/CVI PID Control T oolkit User Manual 3-4 ni.com Using the PID Librar y The following sections describe how to use th e PID Library to implement a control strateg y .
Chapter 3 Using the PID Control T oolkit © National Instruments Corporation 3-5 LabWin dows/CVI PID Control T oolkit User Manual The fast PID algorithm is faster and simpler than the precise PID algorithm. Use the fast algorithm in fast control lo ops.
Chapter 3 Using the PID Control T oolkit LabWindows/CVI PID Control T oolkit User Manual 3-6 ni.com Using PID with Autotuning Y ou can use autotuning to improv e controller pe rformance. There are tw o ways in which you can autotune a controller . • Wizard-Based Autotuning —Y ou can use the PID Autotuning W izard to tune the parameters.
Chapter 3 Using the PID Control T oolkit © National Instruments Corporation 3-7 LabWin dows/CVI PID Control T oolkit User Manual If you are using LabW indows/CVI 8.0 and later , click Add Addi tional Mod ule in the Drivers & Components tab of the Edit Installer dialog box.
Chapter 3 Using the PID Control T oolkit LabWindows/CVI PID Control T oolkit User Manual 3-8 ni.com Using PID with Lead-Lag The lead-lag compensator uses a positional algorithm that approximates a true exponential lead-lag. Feed forwar d control schemes often use this kind of algorithm as a dynamic compensator .
Chapter 3 Using the PID Control T oolkit © National Instruments Corporation 3-9 LabWin dows/CVI PID Control T oolkit User Manual Y ou can use the setpoint profiler as follo ws: 1.
Chapter 3 Using the PID Control T oolkit LabWindows/CVI PID Control T oolkit User Manual 3-10 ni.com value of 1 produces an output of 10 fo r a difference between the SP and PV of 10, regardless of the output range and setpoint range.
Chapter 3 Using the PID Control T oolkit © National Instruments Corporation 3-11 LabWi ndows/CVI PID Control T oolkit User Manu al The control loops can be timed in the following ways: • Software-Timed —In software-timed control loop s, the timing is controlled by the software loop rate.
© National Instruments Corporation A- 1 LabWin dows/CVI PID Control T oolkit User Manual A References The Instrument Society of America (ISA), the organization that sets standards for process control.
© National Instruments Corporation B- 1 LabWin dows/CVI PID Control T oolkit User Manual B T echnical Support and Professional Ser vices Visit the following sections of the award-winning National Instruments Web site at ni.com for technical support and professional services: • Support —T echnical support resources at ni.
Appendix B T echnical Support and Professional Services LabWindows/CVI PID Control T oolkit User Manual B-2 ni.com If you searched ni.com and could not find the answers you need, contact your local off ice or NI corporate h eadquarters. Phone numbers for our worldwide of f ices are listed at the front of this manual.
© National Instruments Corporation G-1 LabWin dows/CVI PID Control T oolkit User Manual Glossar y A algorithm A prescribed set of well-defined rules or processes for the solut ion of a problem in a finite number of steps.
Glossary LabWindows/CVI PID Control T oolkit User Manual G-2 ni.com D damping The progressiv e reduction or suppression of oscillation in a device or system. dead time (T d ) The interval of time, expressed in minutes, between initiation of an input change or stim ulus and the start of the resulting observable response.
Glossary © National Instruments Corporation G-3 LabWin dows/CVI PID Control T oolkit User Manual I Instrument Societ y of America (ISA) The organization that sets standards for process con trol instrumentation i n the United States. integral (control) action Control action in wh ich the output is proportional to the time int egral of the input.
Glossary LabWindows/CVI PID Control T oolkit User Manual G-4 ni.com O output limi ting Pre ve nting a controller’ s output from trav eling beyond a desired maximum range. ov ershoot The maximum excursion beyond the fi nal steady-state value of output as the result of an in put change.
Glossary © National Instruments Corporation G-5 LabWin dows/CVI PID Control T oolkit User Manual R ramp The total (transient plus steady-state) time respon se resulting from a sudden increase in the rate of change from zero to some f inite v alue of input stimulus.
© National Instruments Corporation I-1 LabWi n dows/CVI PID Control T oolkit User Manual Index A applications, 1-3 autotuning, 3-6 classic, 3-6 procedure, 3-6 wizard based, 3-6 distributing applicati.
Index LabWindows/CVI PID Control T oolkit User Manual I-2 ni.com I installation instructions, 1-1 instrument driv ers (NI resources), B-1 integral action, 2-1 integral time, 2-1 K Kno wledgeBase, B-1 L lag compensation, 3-8 lead compensation, 3-8 lead-lag compensator, 3-8 N National Instruments support and services, B-1 Nichols, N.
Index © National Instruments Corporation I-3 LabWi n dows/CVI PID Control T oolkit User Manual S setpoint, 1-3 relay experiment, 2-6 software (NI resources), B-1 step test tuning procedure, 3-3 suppo.
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