Industrial Automation Tech Note 09 - TNIA09
Abstract
This document describes the basic parameters and common functionality of the Crimson based PID controllers.
Products
CSPID1xx, CSPID2xx, CSSGxxxx, GMP1xxxx, GMP2xxxx
Use Case
Configuring systems that incorporate Crimson based PID controllers.
Commonly Used Parameters
Loop – Status – PV
Loop – Control – ReqSP
Loop – Status – HeatPower/CoolPower
Loop – Control – Power
Loop – Control – ReqManual
Loop – Control – ReqTune
Loop – Status – TuneDone
Loop – Status – TuneFail
Loop – Status – ActSP
Loop – Status – AckManual
Loop – Status - AckTune
Turning the Loop Off
Properly turning off a loop will prevent loss of control when set point control is once again required.
Required Module Properties
Loop – Control – ReqManual
Loop – Control – Power
Optional Module Properties
Loop – Status – AckManual
Action
1. Set ReqManual to 1
2. Set Power to 0
Example: ReqManual = 1, Power = 0
Manual Control of the Loop
Properly turning off a loop will prevent loss of control when set point control is once again required.
Required Module Properties
Loop – Control – ReqManual
Loop – Control – Power
Optional Module Properties
Loop – Status – AckManual
Action
1. Set ReqManual to 1
2. Set Power to the required output level 0-10000 (0-100.00%)
Autotuning the Loop
Required Module Properties
Loop – Control – ReqTune
Loop – Control – ReqSP
Loop – Status – TuneDone
Optional Module Properties
Loop – Status – AckTune
Loop – Status – PV
Action
1. Set ReqTune to 1
2. Monitor TuneDone, when it becomes true, set ReqTune to 0.
Figure 1.
Note: Referring to Figure 1, adding an Active On Trigger to the tag mapped to TuneDone with an action to clear ReqTune is recommended.
Overview
Auto-tune may be used to establish the optimal P, I, D, and Power Filter values. By cycling the process through four on/off cycles, the module learns information about the process and determines the best values.
Figure 2.
As shown in Figure 2, the setpoint used during auto-tune is the value 75 % above the difference between the current PV and the setpoint. This allows the oscillations to occur close to setpoint, while avoiding excessive overshoot. Since the module performs on/off control during auto-tune, it is important to set a suitable On/Off Hysteresis value prior to invoking auto-tune.
Customization of the PID set that auto-tune will yield is achieved by adjusting the Tune Response setting. The Tune Response setting can be set to Very Aggressive, Aggressive, Default, Conservative, or Very Conservative. Further, the Tune Response setting can be adjusted by writing 0-4 respectively to the Tune Response register.