Mitsubishi Electric FR-A700 Technical Manual page 395

Servo rigidity adjustment [Pr. 362, Pr. 396 to Pr. 398]
To increase the servo rigidity
stop in [Pr. 396, Pr. 397], adjust with the following
procedures.
1) Increase the [Pr. 362 Orientation position loop gain]
value to the extent that rocking does not occur
during orientation stop
2) Increase [Pr. 396, Pr. 397] at the same rate.
Generally adjust [Pr. 396] in the range from 10 to
100, and [Pr. 397] from 0.1 to 1.0s. (Note that
these do not need to be set to the same rate.)
[Example]
When the [Pr. 396] value is multiplied by 1.2,
divide the [Pr. 397] value by 1.2. If vibration
occurs during orientation stop, the scale
cannot be raised any higher.
3) [Pr. 398] is the lag/advance compensation gain.
The limit cycle can be prevented by increasing the
value, and the running can be stopped stably.
However, the torque in regard to the position
deviation will drop, and the motor will stop with
deviation.
[Application of lag/advance control and PI control]
PI control can be applied by setting [Pr. 398 = 0].
Normally, the lag/advance control is selected.
When using a machine with a high spindle
stationary friction torque and requires a stopping
position precision.
*1 Servo rigidity : This is the response when a
position control loop is configured.
When the servo rigidity is raised, the holding
force will increase, the running will stabilize, but
vibration will occur easily.
When the servo rigidity is lowered, the holding
force will drop, and the settling time will
increase.
*2 Limit cycle :This is a phenomenon that
generates ± continuous vibration centering on
the target position.
*3 Rocking : Movement in which return occurs if
the stopping position is exceeded.
Orientation speed [Pr. 351]
Set the speed when switching between the speed
control mode and the position control mode is
performed under orientation operation.
Decreasing the set speed enables stable
orientation stop. Note that the orientation time will
increase.
When [Pr. 52 DU/PU main display data selection =
19], position pulse monitor is displayed on the PU
instead of output voltage monitor.
[Hz]
Frequency
[Pr.351]
Orientation speed
ON
OFF
Orientation start
(X22)
Orientation
completion
(ORA)
Encoder
Z phase pulse
during orientation
*1
.
*3
*2
Decelerate according to the
deceleration ratio of [Pr. 399]
Orientation command completion
Time [t]
ON
Orientation deceleration ratio [Pr. 399]
Make adjustments as shown below according to
the orientation status. Refer to the [Pr. 396 and Pr.
397] details also.
Generally adjust [Pr. 362] in the range from 5 to 20
and [Pr 399] from 5 to 50.
Orientation stop operation can not be performed
and excessive position error alarm occurs. Or, if
the motor does forward/reverse reciprocation
operation
orientation detector installation direction may be
incorrect. Review [Pr. 393 Orientation selection]
(refer to
page 428
direction] (refer to
Case
[Pr. 396] [Pr. 397] [Pr. 362] [Pr. 399]
Rocking
3)
occurs
during
stopping
The
orientation
time is long
Hunting
2)
occurs when
stopping
The servo
rigidity
1)
during
stopping is
low
*1
:Increase the parameter setting value.
:Do not change the parameter setting value.
:Decrease the parameter setting value.
*2
The numbers 1) 2) and 3) in the table show the
order of priority for changing the parameters
setting value.
(8) Orientation control at machine side
To simultaneously perform orientation control at
machine side with encoder feedback control / vector
control using an encoder at machine side and FR-
A7AL, set the number of encoder pulses to [Pr.829
Number of machine end encoder pulses].
Orientation control to the encoder at machine side is
enabled.
[Setting example]
Number of pulses equivalent for the motor side is
calculate as below when the number of encoder
pulses at machine side is 4000 pulses, and the gear
ratio between motor side and machine side is 4:1
(motor rotates four times while machine rotates
once).
Number of pulses equivalent for the motor side =
×
4000 1/4 =1000
Thus, set [Pr. 369 =1000] and [Pr. 829 =4000]
(encoder pulses at machine side.)
429
PARAMETER
, the parameter setting value for the
) and [Pr. 359 Encoder rotation
).
page 421
Adjustment Procedure
3) 2) 1)
2) 1)
2) 1)
1) 2)
2