Eurotherm 590+ Series, Product Manual, Page: 158 / 308

6-48
Programming Your Application
590+ Series DC Digital Converter
Functional Description
The following block diagram shows the internal structure of the PID block.
PID is used to control the response of any closed loop system. It is used specifically in system
applications involving the control of drives to allow zero steady state error between Reference
and Feedback, together with good transient performance.
P roportional Gain (PROP. GAIN)
This is used to adjust the basic response of the closed loop control system. It is defined
as the portion of the loop gain fed back to make the complete control loop stable. The
PID error is multiplied by the Proportional Gain to produce an output.
O/P SCALER (TRIM) Range: -3.0000 to 3.0000
(O/P SCALER(TRIM))
The ratio which the limited PID output is multiplied by in order to give the final PID Output.
Normally this ratio would be between 0 and 1.
INPUT 1 Range: -300.00 to 300.00 %
This can be either a position/tension feedback or a reference/offset.
INPUT 2 Range: -300.00 to 300.00 %
This can be either a position/tension feedback or a reference/offset
RATIO 1 Range: -3.0000 to 3.0000
This multiplies Input 1 by a factor (Ratio 1).
RATIO 2 Range: -3.0000 to 3.0000
This multiplies Input 2 by a factor (Ratio 2).
DIVIDER 1 Range: -3.0000 to 3.0000
This divides Input 1 by a factor (Divider 1).
DIVIDER 2
Range: -3.0000 to 3.0000
This divides Input 2 by a factor (Divider 2).
ENABLE Range: See below
A digital input which resets the (total) PID Output as well as the integral term when FALSE.
0 : DISABLED
1 : ENABLED
INT. DEFEAT Range: See below
A digital input which resets the integral term when TRUE. The block transfer function then
becomes P+D only.
0 : OFF
1 : ON
FILTER T.C. Range: 0.000 to 10.000 SECS
In order to attenuate high-frequency noise a first order filter is added in conjunction with the
differentiator. The ratio k of the Derivative Time Constant (Td) over the Filter Time Constant
(Tf) (typically 4 or 5) determines the high-frequency lift of the transfer function. For Tf = 0
this filter is eliminated.
MODE Range: 0 to 4
This determines the law which the profiler follows versus diameter.
For Mode = 0, Profiled Gain = constant = P.
For Mode = 1, Profiled Gain = A * (diameter - min diameter) + B.
For Mode = 2, Profiled Gain = A * (diameter - min diameter)^2 + B.
For Mode = 3, Profiled Gain = A * (diameter - min diameter)^3 + B.
For Mode = 4, Profiled Gain = A * (diameter - min diameter)^4 + B.
MIN PROFILE GAIN Range: 0.00 to 100.00 %
This expresses the minimum gain required at min diameter (core) as a percentage of the (max)
P gain at full diameter (100%).
PROFILED GAIN Range: xxxx.x
The output of a profiler block which varies the gain versus diameter. This is primarily to be
used with Speed Profiled Winders for compensation against varying diameter and therefore
inertia. When MODE is not ZERO (see above) this overrides the P gain above.