
B-65150E/04 4. SERVO FUNCTION DETAILS
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(3) Explanation
(a) Servo system configuration
Fig. 4.7 (a) shows the servo system configuration. Fig. 4.7 (b)
shows the velocity loop configuration.
Fig. 4.7 (a) Digital servo system configuration
Fig. 4.7 (b) Velocity loop configuration
(b) When incomplete integration and overshoot compensation are not
used.
First, the 1–pulse motion command is issued from NC. Initially,
because the Position Feedback and Velocity Feedback are “0”, the
1–pulse multiplied position gain Kp value is generated as the
velocity command (VCMD).
Because the motor will not move immediately due to internal
friction and other factors, the value of the integrator is
accumulated according to the VCMD. When the value of this
integrator creates a torque command, large enough to over come
the friction in the machine system, the motor will move and
VCMD will become “0” as the value of MCMD and the Position
Feedback becomes equal.
Furthermore, the Velocity Feedback becomes “1” only when it is
moved, and afterwards becomes “0”. Therefore the torque
command is held fixed at that determined by the integrator.
The above situation is shown in Fig. 4.7 (c).
NC
Kp Velocity loop 1/s
MCMD VCMD
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+
Position feedback Kp: Position gain
PK1V/s Kt/ (Jm • s)
VCMD
TCMD
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+
Velocity feedback
PK1V: Velocity loop integral gain
PK2V: Velocity loop proportional gain
/s: Integrator
PK2V
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+
Motor