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5 Servo Adjustment
MITSUBISHI CNC
(1) Overshooting compensation (OVS compensation)
In OVS compensation, the overshooting is suppressed by subtracting the torque command set in the parameters
when the motor stops.
OVS compensation type 3 has a compensation effect for the overshooting during either rapid traverse settling or
pulse feed. To compensate overshooting during feed forward control, refer to the following section "(2) Adjusting for
feed forward control".
<Setting and adjustment methods>
[1] Set the servo function selection 1 (SV027: SSF1)/bit A, B. (OVS compensation type 3 will start.)
[2] Observe the position droop waveform using the D/A output, and increase the overshooting compensation 1
(SV031: OVS1) value 1% at a time. Set the smallest value where the overshooting does not occur. If SV042
(OVS2) is 0, the overshooting will be compensated in both the forward/reverse directions with the OVS1
setting value.
[3] If the compensation amount is to be changed in the direction to be compensated, set the + direction
compensation value in OVS1 and the - direction compensation value in OVS2. If only one direction is to be
compensated, set the side not to be compensated as -1. The compensation direction setting will be as
reversed with the NC parameter CW/CCW setting.
(2) Adjusting for feed forward control
When using feed forward control (high-speed high-accuracy control), the feed forward control must be stopped
(fwd_g =0) before adjusting the overshooting compensation. After adjusting the overshooting compensation with
normal control, set the overshooting compensation non-sensitive zone (SV034 (SSF3)/bitC to F (ovsn) to 1 (2µm)
and start up feed forward control.
If overshooting compensation is used during feed forward control, the overshooting will increase, or protrusions
could appear during arc cutting. This is because, when the NC is carrying out feed forward (fwd) control,
overshooting equivalent to the operation fraction unit occurs in the position command, and the OVS compensation
is recognized as a change in the command direction, resulting in compensation in the reverse direction. This can be
improved by setting the overshooting compensation non-sensitive zone width.
If overshooting does not occur during normal control, and occurs only during feed forward control, adjust the feed
forward gain (fwd_g).
POINT
1. When either parameter SV031: OVS1 or SV042: OVS2 is set to 0, the same amount of compensation is carried
out in both the positive and negative direction, using the setting value of the other parameter (the parameter not set to 0).
2. To compensate in only one direction, set -1 in the parameter (OVS1 or OVS2) for the direction in which compensation is
prohibited.
3. For contour cutting, the projection at the arc end point is compensated with OVS compensation. LMC compensation is
carried out at the arc starting point.
Cutting direction
LMC compensation
OVS compensation