CONTREX ML-Drive - Manual (Page 61)

3 - 27
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 ML-Drive in the Master mode of
operation, using the default PID parameters and a setpoint value of 1000 RPM. When
the ML-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, adjust the Gain (CP-65) 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 Integral (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 Integral (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). Refer to Table 3-22 to modify the
Control Parameters for Tuning.
The ML-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
3-21. If you are uncertain how to enter a Control Parameter, review the
Operations:
Keypad section, page 3-3.
Table 3-21 Default Master or Follower Tuning Control Parameters
CP Parameter Name Parameter Value
CP-65 Gain (Proportional) 5000
CP-66 Integral 2000
CP-67 Derivative 9000
CP-68 Feedforward 1000