NORDAC SK 530E with PosiCon funktion
3 Function description
BU 0510 EN
Subject to technical changes
13
3.2.1.2 Reset Position via digital inputs or BUS I/O In Bits
Alternatively to the reference point run, one of the digital inputs can be programmed to the setting "
Reset Position
"
(P420-P425 or P470, setting 61). Control via one of the Bus IO In Bits is correspondingly identical. In contrast to
the function reference point , the input or the Bus IO In Bit is always effective and sets the actual position during a
signal change from 0
→
1 immediately to 0. If an offset is parameterised in parameter P609 "Offset actual
position", the axis will always travel by this value. The position reset is implemented independently of the setting for
the "Position control" in parameter P600. The setpoint position is set to 0 in the "Setpoint mode" (in parameter
P610, 2 = position increment array).
The repeat accuracy of referencing via the Reset position is not as good as in the reference point run, it depends
on the tolerance of the reference point switch and the speed with which the switch is approached. However, the
achievable accuracy is sufficient for many applications. In addition, referencing can be implemented without
interrupting the position control.
The function "Reset position" can also be realised via a serial interface or the Bus IO In Bits. To do this, one of the
"Bus setpoint values" (P546, P547 and P548) must be set to the setting 17 "Bus IO In Bits 0..7" and the function
setting 61 assigned to the corresponding bit in P480 "Function Bus I/O In Bits".
NOTE:
Further details on the setting options for functions can be found in the respective parameter
descriptions in Chapter 4 Parameter settings.
3.2.2 Position
acquisition
with CANopen absolute encoder
The absolute encoder transmits the position actual value serially via the CANopen interface to the frequency
inverter. The position is always fully present in the absolute encoder and is also correct after the axis is shifted
when the inverter is switched off. There is therefore no need to make a reference point run.
When connecting an absolute encoder, 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 ratio from motor to absolute encoder must be
parameterised. The absolute encoder revolutions are converted into motor revolutions in the encoder with the aid of
the parameters P607 "Ratio" and P608 "Reduction ratio".
n
M
: Motor
revolution
n
M
= n
G
* Ü
b
/ U
n
n
G:
:
Absolute value encoder revolution
Ü
b
:
Ratio (P607 [02])
U
n
:
Reduction ratio (P608 [02])
Example:
The incremental encoder is attached to the gear output side, the gear has a ratio of i = 26.3. The following values are
parameterised:
Ratio: 263; Reduction ratio: 10
The rotation direction of the absolute encoder must correspond to that of the motor. With a positive output
frequency (rotation right), the position actual value must be larger. If the rotation direction does not correspond, this
can be corrected with a negative value in P607 "Ratio".
The zero point of the axis can be corrected with the help of a parameterisable value in parameter P609 [02] "Offset
position. The offset is taken into account after conversion. After changes to the ratio/reduction ratio in P607 [02]
and P608 [02], the value in parameter P609 "Offset actual position" must be entered again.
ATTENTION
The maximum possible position in parameter P615 "Maximum Position" is based on the
resolution of the encoder and the ratio/reduction ratio (P607 and P608). The maximum value
must in all cases not /- 65535 (16Bit) revolutions. Exceeding this range is not
allowed. Endless axes that run mainly in one direction must be implemented with an
incremental encoder (see Chapter 3.2). Position setpoints are limited internally to the
maximum possible value range.
