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Gain Adjustment
1-1
Types and Meanings of Gain
The word "gain" appears frequently in this technical guide. The gain is one of the indis-
pensable parameters of the Servo System. If the gain adjustment of the Servo System is
insufficient, the operation of the Servo System will be unsatisfactory, in which case the
Servo System will cause machinery vibration and an alarm will result. A summary of the
Servo System and all gains used for the Servo System loops are described below.
1-1-1 Summary of Servo System
The Servo System uses feedback loops. In a feedback loop, the response value is fed back after the
command so that the difference between the response and command values will be as close as pos-
sible to zero. The Servo System consists of three feedback loops (i.e., position loop, speed loop, and
current loop). Refer to the following block diagram.
Position Loop
• The position loop is used to let the rotation angle of the motor reach the desired position (i.e., the de-
sired rotation angle) that was externally designated.
• The speed command is output from the position loop to the speed loop.
• The position loop feeds back the position data (i.e., the information on rotation angle) of the encoder or
resolver.
Speed Loop
• The speed loop is used to let the motor rotate at the speed designated by the external analog speed
command or the speed command that is output from the position loop.
• The current command is output from the speed loop to the current loop.
• The speed loop feeds back the speed data of the encoder or resolver.
Current Loop
• The current loop provides the motor with the current designated by the current command that is output
from the speed loop.
• The current loop feeds back the motor current value.
The gain is a parameter to adjust the response speed of a feedback loop.
1-2
Chapter 1
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