NORD Drivesystems BU0210 - Manual (Page 16)

SK 2x5E with "PosiCon Functionality"
16 Subject to technical amendments BU 0210 GB
3.2.2 Position detection with CANopen absolute encoders
The absolute encoder communicates the actual position value serially via the CANopen interface on the
frequency inverter. The position is always completely available in the absolute encoder and is also correct after
displacement of the axis when the inverter is switched off. A reference point run is therefore not necessary.
If an absolute encoder is connected the parameter P604 "Encoder Type" must be parameterised to one of the
absolute functions (Setting 1, 5, 6 or 7) for the CANopen absolute encoder.
If the absolute encoder is not mounted on the motor shaft the gear ratio between the motor and the absolute
encoder must be parameterised. Rotations of the absolute encoder are converted to motor revolutions by the
inverter with the aid of parameter P607 "Speed Ratio" and P608 "Reduction Ratio".
n
M
: Motor rotations
n
M
= n
G
* Ü
b
/ U
n
n
G:
: Absolute encoder rotations
Ü
b
: Speed Ratio (P607[02])
U
n
: Reduction Ratio (P608[02])
Example: The absolute encoder is installed on the output side of the gear unit. The gear unit has a ratio of i = 26.3.
The following values are parameterised.
Speed ratio: 263; Reduction ratio: 10
The direction of rotation of the absolute encoder must comply with the direction of rotation of the motor. With a
positive output frequency (clockwise rotation) the actual position value must increase. If the direction of rotation
is not correct, this can be adjusted with a negative value in P607 "Speed Ratio".
The zero point of the axis can be adjusted with the aid of value which can be parameterised in parameter P609
[02] "Offset Position". The offset is applied after the calculation. After changes to the Speed Ratio/Reduction
Ratio P607 [02] and P608 [02] the value in parameter P609 "Offset Position" must be entered again.
ATTENTION
The maximum possible position in parameter P615 "Maximum Position" results from the resolution of
the encoder and the Speed Ratio/Reduction Ratio (P607 and P608). Under no circumstances can the
maximum value exceed +/- 65535 (16Bit) rotations. Circulation is not permissible. Endless items,
which mainly run in a single direction must be realised with an incremental encoder (See Section
3.2.1). Position setpoints should be internally limited to the maximum possible value range.