Mitsubishi Electric MELSEC iQ-R16MTCPU Programming Manual page 231

Optimum corner deceleration
When the composite speed that is generated at the joints between blocks is kept equal to or lower than the common tolerable
acceleration for each axis determined by the G-code control system parameters "acceleration/deceleration before
interpolation - maximum speed", "acceleration/deceleration before interpolation - time constant", and the accuracy coefficient
by deceleration control, highly precise edges can be cut. When entering a corner, the optimum speed (optimum corner speed)
is calculated from the angle with the next block (corner angle), and the common tolerable acceleration for all axes. The
system decelerates to this speed in advance, and after passing the corner, returns to the command speed.
Y-axis
F: Speed before passing corner
∆F: Acceleration at corner
Composite speed
F0 =
X-axis speed
F0x
Y-axis speed
F0y
When blocks are joined smoothly, deceleration is not required therefore optimum corner deceleration is not performed. The
basis of whether blocks are joined smoothly or not is set in [Motion Control Parameter][G-code Control Parameter][G-
code Control System Parameter]"High-accuracy Control""Corner Deceleration Angle". When the corner angle is equal to
or less than the set corner deceleration angle, it is deemed to be a smooth corner and optimum corner deceleration is not
performed. Also, when improving the precision of edges, set the accuracy coefficient in [Motion Control Parameter][G-code
Control Parameter][G-code Control System Parameter]"High-accuracy Control""Corner Accuracy Coefficient".
When a value close to the upper limit of the accuracy coefficient is set, the edge precision improves, but the cycle time
increases due to the slower optimum corner speed. When a negative value is set to the accuracy coefficient, the optimum
corner speed increases and the cycle time shortens, but the edge precision is reduced.
The common tolerable acceleration for all axes can be calculated with the following formula.
Common tolerable acceleration for all axes[mm/s
When passing through the corner with corner angle () at speed (F), the acceleration
(F) that corresponds with corner angle () and speed (F) is generated.
F: Speed after passing corner
X-axis
The corner speed (F) is controlled so that the acceleration (F) does not exceed the
common tolerable acceleration for all axes. The speed pattern is shown in the figure to
the left.
2 2
F0x + F0y
Time
Time
Time
Acceleration/deceleration before
interpolation - maximum speed[mm/min] ÷ 60
2
] =
Acceleration/deceleration before
interpolation - time constant[ms] ÷ 1000
100 - Corner accuracy coefficient
×
100
6 AUXILIARY AND APPLIED FUNCTIONS
6.7 High-Accuracy Control
6
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