Eurotherm Drives 590 DRV Digital, Product Manual, Page: 288 / 318

590 DRV Digital DC Drive Product Manual
App. M - 8
Appendix M Special Blocks and Application Notes
M
PID
The PID block executes a Propor In Derivative control algorithm with
an added filter to attenuate high-frequency noise. P, PD, PI, or PID can be selected as
required. The algorithm modifies the error between the setpoint and the feedback with
the proportional, integral, and derivative terms. The error is clamped internally to
±105 percent maximum.
NOTE. This block is ignored by the drive unless SYSTEM:: CONFIG-
URE I/O:: BLOCK DIAGRAM:: PID is connected to a non-zero tag.
The proportional, integral, and derivative terms are scaled by the PROP. GAIN, INT.
TIME CONST., and DERIVATIVE TC, respectively. An additional gain profiler can
modify the proportional gain as the roll diameter changes. Figure M.8 shows how the
proportional gain changes when using the profiler.
DIGITAL DC DRIVE
MENU LEVEL
MENU LEVEL
DIAGNOSTICS
MENU LEVEL
SETUP PARAMETERS
SETUP PARAMETERS
SPECIAL BLOCKS
SPECIAL BLOCKS
SPECIAL BLOCKS
SPECIAL BLOCKS
SPECIAL BLOCKS
RAMPS
DIAMETER CALC.
TAPER CALC.
TORQUE CALC.
SETPOINT SUM 2.
PID
SETUP PARAMETERS
AUX I/O
SETUP PARAMETERS
SETUP PARAMETERS
SETUP PARAMETERS
JOG/SLACK
RAISE/LOWER
SPECIAL BLOCKS
M
M
M
Figure M.6 - Gain Profiler
Proportional gain scales the output based upon the input error. Increasing PROP. GAIN
will improve the response time while increasing overshoot. MODE selects the propor-
tional gain profile. When set to 0, the proportional gain remains constant over the entire
roll. Changing the value of MODE increases the profile as shown in Figure M.8. PROP.
GAIN and MIN PROFILE GAIN set the maximum and minimum gains over the range of diameters as the roll builds.
Integral eliminates steady-state error. Reducing INT. TIME CONST. improves response; however, if it is set too short,
it will cause instability. The integral value is clamped internally by the settings of POSITIVE LIMIT and NEGATIVE
LIMIT. It is also held at the last value when the PID CLAMPED output is TRUE. Setting INTEGRAL DEFEAT to
ON will disable the integral gain term.
Tag Parameter Description Range Default
410 Input 1 PID setpoint input. ±300.00% 0.00%
412 Ratio 1 Multiplier term for Input 1. ±3.0000 1.0000
418 Divider 1 Divider term for Input 1. ±3.0000 1.0000
411 Input 2 PID feedback input. ±300.00% 0.00%
413 Ratio 2 Multiplier term for Input 2. ±3.0000 1.0000
414 Divider 2 Divider term for Input 2. ±3.0000 1.0000
409 Integral Defeat When On the integral term is disabled. Off/On Off
408 Enable Enables or disables the PID output. Disabled/Enabled Enabled
417 PID Output Output of the PID block. ±315.00%
415 PID Error The difference between Input 1 and Input 2. ±105.00%
416 PID Clamped Signals that one of the PID limits has been reached. False/True
404 Prop. Gain Maximum limit of the proportional gain. 0.0 - 100.0 1.0