Omron NJ501-1300, User Manual

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9-31
9 Motion Control Functions
NJ-series CPU Unit Motion Control User’s Manual (W507)
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9
9-5-4
Jer
k
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 on the
machine.
Additional Information
Jerk is also called jolt, surge and lurch.
Jerk is given in command units/s
3
. The command unit is the value obtained from unit conversion of the
position display unit and the electronic gear.
The jerk used in an actual positioning motion is specified with the Jerk input variable to the motion con-
trol instruction. This value is used for both acceleration and deceleration and can be set for all opera-
tions except for synchronized control operations.
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.
z
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.
Example: Acceleration of 25,000 mm/s
2
, Acceleration Time of 0.1 s, and a Jerk Application Rate
of 50%
Jerk = 25,000/(0.1
×
0.5/2) = 1,000,000 (mm/s
3
)
9-5-4 Jerk
Jerk Unit
Specifying Jerk for Axis Motion
25% 25%
Velocity
Time
Time
Time
Acceleration rate
at startup
Jerk
at startup
Target velocity
at startup
Jerk
Acceleration
rate