9.6.2 Outline
The moment of inertia during operation is automatically calculated by the SERVOPACK
for round-trip (forward and reverse) operation. A reference from the host controller is not
used.
The moment of inertia ratio (i.e., the ratio of the load moment of inertia to the motor
moment of inertia) is a basic parameter for adjusting gains. It must be set as accurately
as possible.
Although the load moment of inertia can be calculated from the weight and structure of
the mechanisms, doing so is very troublesome and calculating it accurately can be very
difficult with the complex mechanical structures that are used these days. With moment of
inertia estimation, you can get an accurate load moment of inertia simply by operating the
Servomotor in the actual system in forward and reverse a few times.
The Servomotor is operated with the following specifications.
n Maximum speed: ±1,000 min
-1
(can be changed)
n Acceleration rate: ±20,000 min
-1
/s (can be changed)
n Travel distance: ±2.5 rotations max. (can be changed)
Note: Execute moment of inertia estimation after jogging to
a position that ensures a suitable range of motion.
SERVOPACK Travel distance
Servomotor
Travel distance
Responses
References
Movement
speed
Fig. 225: Moment of Inertia Estimation
9.6.3 Restrictions
The following restrictions apply to estimating the moment of inertia.
n When the machine system can move only in one direction
n When the range of motion is 0.5 rotations or less
n When a suitable range of motion is not possible
n When the moment of inertia changes within the set operating range
n When the machine has high dynamic friction
n When the rigidity of the machine is low and vibration occurs when positioning is per-
formed
n When the position integration function is used
n When proportional control is used
Check the following settings before you execute moment of inertia estimation.
n The main circuit power supply must be ON.
n There must be no overtravel.
n The servo must be OFF.
n The control method must not be set to torque control.
Systems for which Execu-
tion Cannot Be Performed
Systems for Which Adjust-
ments Cannot Be Made
Accurately
Preparations
Sigma-7 Series SERVOPACKs
Tuning
Estimating the Moment of Inertia > Restrictions
| | PROFINET Communications - SIEP YEUOC7P 02A Revision 0 | en | 309
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