CONTREX MLP-Drive - Manual (Page 86)

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Tuning
If your system is unstable, or the speed error is unacceptable, tuning stabilizes speed
error differences between the setpoint and feedback. You can achieve a stable system
using conservative tuning Control Parameter values, however, the speed error may be
unacceptable. On the other hand, aggressive tuning Control Parameter values may
cause the system to become unstable. The goal is to reduce the speed error to the
level that you want, yet maintain the system's stability.
Before you adjust the PID parameters (CP-65, 66, 67), you will need to set the
Feedforward (CP-68). To accomplish this, run the MLP-Drive in the Master mode of
operation, using the default PID parameters and a setpoint value of 1000 RPM. When
the MLP-Drive has reached stability at 1000 RPM, enter the value of the PIDF Output
(MP-49) into Feedforward (CP-68).
To achieve an acceptable level of speed error, reduce the Gain (CP-65) until the system
becomes unstable, then increase slightly until the system stabilizes. In systems that
require greater accuracy, it may be necessary to adjust the Integral (CP-66) to reduce
any remaining speed error. In systems with low inertia, the speed error will be reduced
more quickly if you enter low values in CP-66. An entry that is too low, however, can
create instability or overshoot the setpoint before reaching the correct value. Generally,
use larger entries for CP-66 on systems with a large inertia. Sometimes performance
can be improved in systems with a large inertia by lowering the Derivative (CP-67). If
stability cannot be obtained with the above tuning procedure, reduce the Trim Authority
(CP-69) and repeat the tuning procedure.
The MLP–Drive comes factory pre-loaded with default Control Parameters for Tuning.
These default settings are suitable for most applications and do not require
modification. The factory preset, default tuning Control Parameters are found in Table
3-39. To modify these default parameters, refer to Table 3-40.
Table 3-39 Default Master or Follower Tuning Control Parameters
CP Parameter Name Parameter Value
CP-65 Gain (Proportional) 9000
CP-66 Integral 2000
CP-67 Derivative 9000
CP-69 Trim Authority 100