Setting Of Positioning Adjustment Parameter (Pr. 426, Pr. 427) - Mitsubishi Electric FR-A720-0.4K Instruction Manual

Position control by vector control
Relationship between position resolution Δ
Since overall accuracy (positioning accuracy of machine) is the sum of electrical error and mechanical error, normally
take measures to prevent the electrical system error from affecting the overall error. As a guideline, refer to the
following relationship.
1 1
( )
Δ < to
5 10
<Stopping characteristic of motor>
When parameters are used to run the motor, the internal command pulse frequency and motor speed have the
relationship as shown in the chart on page 129, and as the motor speed decreases, pulses are accumulated in the
deviation counter of the inverter. These pulses are called droop pulses (ε) and the relationship between command
frequency (fo) and position loop gain (Kp: Pr. 422) is as represented by the following expression.
fo
ε =
[pulse]
Kp
When the initial value of Kp is 25s
Since the inverter has droop pulses during running, a stop settling time (ts) is needed from when the command has
zeroed until the motor stops. Set the operation pattern in consideration of the stop settling time.
1
ts = 3 ×
[s]
Kp
When the initial value of Kp is 25s
The positioning accuracy Δε is (5 to 10) × Δ
(2) Position command acceleration/deceleration time constant (Pr. 424 )
⋅ When the electronic gear ratio is large (about 10 or more times) and the speed is low, rotation will not be smooth,
resulting in pulse-wise rotation. At such a time, set this parameter to smooth the rotation.
⋅ When acceleration/deceleration time cannot be provided for the command pulses, a sudden change in command
pulse frequency may cause an overshoot or error excess alarm. At such a time, set this parameter to provide
acceleration/deceleration time.
Normally set 0.
♦Parameters referred to♦
Pr. 422 Position loop gain
4.6.5

Setting of positioning adjustment parameter (Pr. 426, Pr. 427)

Parameter
Name
Number
426 In-position width
427 Excessive level error
The above parameters can be set when the FR-A7AP (option) is mounted.
* When the operation panel (FR-DU07) is used, the maximum setting is 9999. When a parameter unit is used, up to the maximum value within
the setting range can be set.
(1) In-position width (Pr. 426 )
The Y36 signal acts as an in-position signal.
When the number of droop pulses has fallen below the setting value, the in-position signal (Y36) turns on.
For the Y36 signal, assign the function by setting "36" (positive logic) or "136" (negative logic) in any of Pr. 190 to Pr.
196 (output terminal function selection) .
(2) Excessive level error (Pr. 427 )
When droop pulses exceed the value set in Pr. 427 , position error large occurs and displays an error (E.OD) to stop
the inverter. When you decreased the Pr. 422 Position loop gain setting, increase the error excessive level setting.
Also decrease the setting when you want to detect an error slightly earlier under large load.
When "9999" is set in Pr. 427 , position error large (E.OD) does not occur regardless of droop pulses.
136
and overall accuracy
× Δε Δε:positioning accuracy
204800
ε =
[pulse] (rated motor speed)
25
-1
, the droop pulses (ε) are 8192 pulses.
-1
, the stop settling time (ts) is 0.12s.
= Δε [mm]
Refer to page 137
Initial Value
100 pulses
40K
Setting Range
When the number of droop pulses has fallen below
0 to 32767 pulses
*
the setting value, the in-position signal (Y36) turns on.
A position error excessive (E.OD) occurs when the
0 to 400K
number of droop pulses exceeds the setting.
9999 Function invalid
Vector Vector Vector
Description