Jerk - Omron NX701-1 User Manual

Example of Acceleration/Deceleration Operation
Maximum velocity
(2) Target velocity
after velocity
change
(1) Target velocity
at startup
When Starting
Ta1: Actual acceleration time
A:
If you specify a short travel distance or a low acceleration/deceleration rate, the target velocity may not
be reached. If the target position is exceeded after re-execution of the motion control instruction with
the newly updated acceleration or deceleration rate, positioning is performed at an acceleration or
deceleration rate that will enable stopping at the target position.
9-5-4

Jerk

The jerk specifies the rate of change in the acceleration rate or deceleration rate. If the jerk is specified,
the velocity waveform during acceleration will be an S-curve, which will reduce the shock and vibration
on the machine.
Additional Information
Jerk is also called jolt, surge and lurch.
Jerk Unit
Jerk is given in command units/s
position display unit and the electronic gear.
Specifying Jerk for Axis Motion
The jerk used in an actual positioning motion is specified with the Jerk input variable to the motion con-
trol instruction. The same value is used for acceleration and deceleration.
Use the following formula to calculate the value to set for the jerk.
Jerk = Acceleration rate ÷ (Time of acceleration × Ratio of time to apply jerk during acceleration/2)
Jerk is applied in two sections: at the start of acceleration and at the end of acceleration. The time that
jerk is applied is therefore divided by 2.
 Example of Velocity Control When Jerk Is Specified
The acceleration will change at a constant rate over the range where jerk is specified. The command
velocity will form a smooth S curve. A fixed acceleration rate is used in areas where the jerk is set to
0. This command velocity will form a straight line.
NJ/NX-series CPU Unit Motion Control User's Manual (W507)
Velocity
A
A
Ta1
Acceleration rate
3
. The command unit is the value obtained from unit conversion of the
Ta2
For Velocity Changes When Decelerating
Ta2: Actual acceleration time Td: Actual deceleration time
A: Acceleration rate D: Deceleration rate
9 Motion Control Functions
D
Time
Td
9
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