Operating instructions

Functions
5.10 Technological functions
CU240S and CU240E Control Units, FW 3.2
146 Operating Instructions, 03/2009, A5E02440075B AA
5.10.4 Positioning down ramp
A basic positioning function in the inverter
In certain applications, e.g. when a conveyor belt is brought to a standstill, the belt may have
to travel a defined braking distance after it has been switched-off so that it always stops at
the same position.
For a fixed ramp-down type, the number of revolutions that a motor requires to reach a
standstill depends on the speed of the motor at the instant of the switch-off. Using the
"positioning down ramp" function, the number of revolutions from the OFF1 command down
to standstill can be defined independent of the speed.
The following diagram shows the principle signal characteristic of velocity (v) and position (s)
of a linearly moved load, e.g. of a conveyor belt, that is stopped using the positioning down
ramp. For a low velocity (v
2
) the down ramp is extended so that the load comes to a standstill
at the same end position (s
0
) as for a higher velocity (v
1
).
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W
V
0
W
Y
Y
1
Y
1
Y
2
Y
2
V
Figure 5-15 Velocity (v) and position (s) of a linearly moved load with the positioning down ramp
The accuracy of this basic positioning function is adequate for many applications. The
accuracy is increased when using a speed encoder.
Table 5- 64 Parameters for the simple positioning function
Parameters Description
P2480 = … Control command for the positioning function
Example: When P2840 = 722.0, the positioning function is activated via digital input
0.
P2481 = …
P2482 = …
Gear ratio = P2481/P2482
P2484 = … Number of shaft revolutions at the gearbox output for one distance unit
P2488 = … Number of distance units until the end position
P2487 = … Additive compensation value for increasing accuracy
For more information about this function, see the List Manual.