Description

This is a sample program implementing a Shock Absorber (speed of change limiter).

Typical situation when such an algorithm is required is a PIDA function block using a water control valve in the output. While the output of PIDA can generally change very fast, even momentarily, such a control action may cause a hydraulic shock and severe damage of the pipeline. To prevent it, the speed of change of the valve position must be limited.

Input/output parameters:

Sample Value, 42002, floating-point: input value to be damped
Period, First parameter of the T.01 function block, integer: period between two changes in 0.01 second intervals
Max Change, 42010, floating-point: maximum change of value allowed in one Period
Damped Value, 42004, floating-point: output (damped) value

The function block limits the speed of change of the value to
Max Change [input units] / Period [seconds]

Usually one would keep Period very small (e.g. 100ms), and Max Change at a corresponding level.

Note: In this example Period is set to 1s.

To see the sample's functionality, manually change the input parameters and watch the output.

Instructions

To use this sample program:

• Select the following link: ShockAbsorber.zip
• Select the Open button. (Winzip is opened)
• Select the Use Evaluation Version button. (The Winzip program list is displayed)
• From Winzip, select all files in the display list and then extract them to a target folder on your computer.
• Exit Winzip.

• Open the TelePACE application.
• Select File | Open to display the Open File dialog box.
• Browse to the appropriate directory where the files are located and select the .LAD file.
• Select the OK button to open the file.