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Sep
09

Control Using Wireless Measurements

A number of technical challenges must be addressed when using a wireless measurement in closed loop control. In DeltaV v11 we introduced a PID option known as PIDPlus that may be selected when a wireless transmitter is used in a control application. When the PIDPlus option is selected then the same quality control as wired PID can be achieved using a wireless measurement, despite slower wireless measurement update and communication interruptions. The PIDPlus novel algorithm is based on a modification of the PID reset and rate calculation to account for non-periodic measurement updates. The basis for these PID modifications is detailed in Chapter 9 of Advanced Control Foundation – Tools, Techniques, and Applications. Also, a demonstration of this capability may be seen by going to the book’s web site and viewing the Intelligent PID workshop solution. As part of the future architecture team’s continuing work on wireless control, we have explored an alternate approach of PID control based on using a Kalman filter observer to account for non-periodic measurements updates. To address this application it is necessary to modify the Kalman filter as illustrated below.

In this work on wireless control we also addressed how the Smith Predictor may be modified to work with a wireless measurement. At Emerson Exchange Mark Nixon and I will host a workshop in which we present test results that compare the PIDPlus performance to that achieved using these alternate approaches. The tests include a variety of operating conditions that may be encountered when using wireless transmitters. If you are considering using a wireless measurement in a control application then the workshop may be of interest.

 12-4381 – Control Using Wireless Measurements | Terry Blevins, Mark Nixon

This workshop will be given two times at Emerson Exchange: Tuesday, Oct 1, at 9am in room: Dallas 7 and on Thursday, Oct 3rd at 10am in room: Pecos 4.