Rockwell-automation 1391ES AC Servo Controller User Manual download pdf (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.

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Rockwell-automation 1391ES AC Servo Controller User Manual Page 50