Rockwell Automation 1391ES AC Servo Controller - Manual (Page 50)

Start-Up
Chapter 7
7-48
Figure 7.2
Velocity Response Profiles
Commanded Velocity
Time
Underdamped
Critically Damped
Overdamped
R144 Controls Amount of Overshoot
System Compensation Procedure
o 18. Monitor the velocity feedback signal at terminals 6 (common) and 7
of TB2 with an oscilloscope or chart recorder.
ATTENTION: If an oscilloscope (or chart recorder) is used
during Start-Up or Troubleshooting, it must be properly
grounded. The oscilloscope chassis may be at a potentially fatal
voltage if not properly grounded. Always connect the
oscilloscope chassis to earth ground.
When using an oscilloscope (or chart recorder) it is
recommended that the test probe ground be connected to TP12.
!
o 19. Adjust the Velocity GAIN potentiometer (R144) and observe the
velocity response (at TB2-7) profile at various levels of step input
speed commands. The “Underdamped” response curve in Figure 7.2
with a single velocity overshoot of 20-30% on accel and decel is
optimal on a point to point positioning or velocity controlled system.
The “Critically Damped” curve is desirable on a contouring or metal
removing system.
The GAIN pot should be adjusted so that the motor achieves the
commanded speed or final position as quickly as possible with no
overshoot. In addition to the dynamic response, the motor shaft
should not oscillate or exhibit any erratic motion at zero speed.