Mitsubishi Electric MELDAS C6 Programming Manual page 271

13. Program Support Functions
(2) Reduction of arc radius reduction error amount using feed forward control
With the high-accuracy control, the arc radius reduction error amount can be greatly reduced
by combining the pre-interpolation acceleration/deceleration control method above-mentioned
and the active feed forward control/SHG control.
The logical radius reduction error amount ∆R in the high-accuracy control mode is obtained
with the following expression.
Active feed forward control
By setting Kf to the following value, the delay elements caused by the position loop in the
servo system can be eliminated, and the logical ∆R can be set to 0.
Kf = 1 (Feed forward gain 100%)
The feed forward gain can be set independently for G00 and G01.
(Note)
∆ R ≤
F
R
If the machine vibrates when Kf is set to 1, Kf must be lowered or the servo system
must be adjusted.
263
13.12 High-accuracy control
SHG control + active feed forward control
1
2 ( 1 − K f 2
{ T p ) } (
2 R
R : Arc radius (mm)
F : Cutting feedrate (mm/min)
Tp : Position loop time constant (s)
Kf : Feed forward coefficient
The equivalent feed forward gain to set Kf to 1 can be
obtained with the following expression.
⎧ ⎫
2
⎛ ⎞ ⎪
fwd g _
− −
⎨
⎜ ⎟ ⎬
100 1 1
⎪
⎝ ⎠
⎩ ⎪
50 ⎭ ⎪
∆R
Path for pre-interpolation
acceleration/deceleration control method (Kf = 1)
Path for pre-interpolation
acceleration/deceleration control method (Kf = 0)
Path for post-interpolation
acceleration/deceleration control method
F
2
)
6 0
2
⎛ ⎞
PGN1 for conventional control
⎜ ⎟
⎝ ⎠
2 × PGN1 for SHG control