1.Introduction

Most industrial control loops are still of PID types. According to statistics, many industrial PID loops are poorly tuned, which greatly hinders the operation of production units. Therefore, optimization of PID parameters will improve production unit operation and bring huge economic benefit. Much PID tuning work is done manually, which is time consuming and tuning quality cannot always be guaranteed. Currently, most PID tuning packages use open loop step test for model identification. This will disturb unit operation.

Tai-Ji PID® Net is a website for PID auto-tuning. It is based on closed-loop process identification. The website loads input-output data, then perform model identification and PID parameter tuning, all automatically. Both open loop and closed-loop test data can also be used.

Tai-Ji PID® Net functionalities and features includes:

• Modelling using closed-loop identification
• Closed-loop test do not disturb unit operation
• User-friendly, designed for layman of PID control
• • Compatible with many DCS systems: Honeywell, Foxboro, Bailey, Yokogawa, DeltaV, Siemens and more...

Tai-Ji PID® Net implemented a small part of the functionalities of Tai-Ji PID®, a stand-alone PC software for PID tuning. Tai-Ji PID® has more functionalities:

• Connectivity to DCS using OPC.
• Performing plant test, both open loop and closed-loop.

2.How to Use Tai-Ji PID® Net

Start your session

Visit www.taijipid.com and type in your PID loop name.

Specify your DCS, PID type and data sampling time

In the upper left corner of the screen, click “DCS Vendor” box and select your DCS system; then click “Controller Type” to determine your controller formula. Also specify the PID type as “PID” or “PI”, sampling time of the data, Setpoint (SP) Range and controller output (OP) range.

Model identification and PID tuning

In the upper right corner, click “Tune” button. After a few seconds, tuning results will be shown under the signal plots. Three sets of tuning will be give: slow tuning, medium tuning and fast tuning. Each tuning is shown in a row. The left entry are the closed-loop step responses of the new tuning (purple line) and that of the old tuning (green line, only for close-loop test); the middle entry are the closed-loop load response of the new tuning (purple line) and that of the old tuning (green line, only for closed-loop test). The right entry shows the PID parameters for the given DCS formula.

Clicking the “Model and Analysis” button on the right bottom of the screen, model identification results will be plotted. The left is the step response of the open loop process: the middle are the model frequency response (green line) and model error bound (purple line): the right are the measured process variable (green line) and model simulation (purple line).

Finally, you can put all results in a PDF file by clicking the “Doanload Pdf” button.

That's all.