Smith predictor

The source files illustrating the use of a Smith predictor in the REXYGEN System are located in this folder.

The Smith predictor is a famous method, how to deal with a deadtime problem in control systems. The predictor is based on estimation of controlled process. If it is possible to estimate parameters of the process, it is possible to predict the process value on mathematical model without a deadtime and control the system according this information.

The PIDMA - PID controller with Moment Autotuner, which is implemented in REXYGEN System, is able to estimate parameters of the process. User can set this parameters into the Smith Predictor and autotune the PID controller according the information from the mathematical model.

Timing of the project

The algorithm runs each 100 milliseconds (0.1 s). See the EXEC function block,
tick x ntick0 = 0.05 x 2 = 0.1

Prerequisites

• REXYGEN Runtime Core and AdvBlk modules must be installed and running on the target device.

Running the example

• The exec.mdl file is the project main file.
• Open it with REXYGEN Studio.
• Check that the CNB_SMITH_ON is off and CNI_ips is equal to 3.
• Compile and download the project to the target device.
• Switch to Watch mode and observe the algorithm.
• Select the PIDMA block and enable online monitoring (Target->Watch Selection).
• Open trend diagnostic window for the block TRND_SMITH to observe trends.
• Tick the BSTATE parameter of the MP_TUNE to switch on the autotuning experiment.
• When the experiment is done, PIDMA:ite parameter is 0 and pk, pti, ptd are estimation of the static gain (pk), dead-time (pti) and time constant (ptd) of the system MDL_PROC.
• Change the CNR_sp to 0.5 and observe regulation process in trends.
• Change the CNR_sp back to 0.
• Open the Smith_Predictor subsystem and change the parameters of MDL_PDT and MDL_P0. Set following parameters to both MDL blocks as: k0 = PIDMA:pk, tau1 = tau2 = PIDMA:ptd. Set parameter del = PIDMA:pti for MDL_PDT block and del = 0 for MDL_P0.
• Switch the CNB_SMITH_ON on.
• When signals are stable, tick the BSTATE parameter of the MP_TUNE again.
• When the tune experiment is done, change the CNR_sp back to 0.5 and observe the fastest regulation process in trends.

Documentation

• Press F1 for help on the selected function block in the REXYGEN Studio.
• PIDMA function block documentation
• Function blocks of REXYGEN
• REXYGEN Studio User Guide
• Complete documentation of REXYGEN

Additional information

• Visit the REXYGEN webpage for more information about the example projects and developing advanced automation and control solutions using REXYGEN.