Control Using Wireless Measurements

During the initial development of WirelessHart we began researching how to address control applications that use a wireless measurement and/or wireless actuator. To extend battery life a wireless transmitter may be setup to communication the measurement value much slower than the update rate of a wired installation. Also, when the transmitter supports Window communications (as defined in the WirelessHART standard) then the control must be able to deal with non-period measurement updates. To address these technical challenges, the PIDPlus capability was introduced in DeltaV v11. The DeltaV PIDPlus is designed to account for slow and non-periodic measurement updates. Earlier this month at Emerson Exchange, Mark Nixon and I hosted a workshop on Control Using a Wireless Measurement. In this workshop we examine an alternate approach for wireless control based on using PID with a modified Kalman filter or modified Smith Predictor observer. Test results that compare the PIDPlus to these alternate approaches were presented in the workshop. This presentation was given two times at Emerson Exchange and both presentations were well attended as illustrated below.

You can see and listen to this presentation using the embedded link shown below. The presentation is approximately 33 minutes in length:

  •  0-7 background information wireless control and PIDPlus.
  •  7-12 wireless control based on PID and an observer
  • 12-20 test results for setpoint changes and unmeasured process disturbances
  •  20-22 conclusions and where to get more information
  •  22-33 questions and answers

The technical basis for PIDPlus is addressed in Chapter 8 of Advanced Control Foundation – Tools, Techniques, and Applications. In the workshop for this chapter the performance of PIDPlus using a wireless measurement is compared to PID using a wired measurement. A 10 minute YouTube video that shows the workshop solution can be found on the book’s web site.