CHAPTER 5.0 Functional Overview
5-18
CDS7324 (FORMERLY LSF-0819)
Rev. A
INSTALLATION & USER’S MANUAL
5.6.1.7
Direction of rotation
The direction of rotation can be reversed with the parameter
encoder_direction_of_rotation
(Field Number 1707).
Normally positive direction is clockwise rotation when looking onto the encoder shaft. In this case, channel A is
leading the channel B signals. If the direction has to be changed because of different encoder signals or
mounting of the encoder on the motor or machine,
encoder_direction_of_rotation
can be set to 1. This reverses
the direction so that positive direction is counter clockwise rotation when looking onto the encoder shaft. The
change of direction affects the encoder position, the encoder velocity, and the encoder commutation angle.
0
-
normal direction: positive position count when rotating clockwise
looking onto the encoder shaft
1
-
reversed direction: positive position count when rotating counter
clockwise looking onto the encoder shaft
5.6.1.8
Number of data stream bits for SSI encoders
For SSI encoders, the number of bits in the data stream has to be set using the parameter
encoder_ssi_number_bits
(Field Number 1709). It contains the number of bits in the raw data stream (not the
number of encoder position bits !). See encoder manufacturers manual for further information.
5.6.1.9
Data encoding for SSI encoders
The encoding can be changed between binary and Gray code transmission with the parameter
encoder_ssi_coding
(Field Number 1710). The following values are possible:
0
-
Gray code
1
-
Binary code
See encoder manufacturers manual for further information.
5.6.1.10
Position bit mask for SSI encoders
Depending on the encoder, not all bits in the SSI data stream contain position information. To accommodate
this, the parameter
encoder_ssi_data_bit_mask
(Field Number 1711) has to be set to mask off all the unused bits
in the raw data stream. A one in
encoder_ssi_data_bit_mask
means that the bit contains position information.
The least significant bit in
encoder_ssi_data_bit_mask
corresponds to the last bit clocked out of the encoder.
Bits above the number set in
encoder_ssi_number_bits
are 'don't care'; they are ignored.
5.6.1.11
Encoder commutation position
The encoder can also be used for commutation of the motor (motor phase current change depending on rotor
angle position). The parameter
encoder_commutation_position
(Field Number 1714) contains a 16-bit value that
represents a full mechanical revolution independent of the encoder resolution setting
encoder_resolution
. The
encoder direction of rotation parameter
encoder_direction_of_rotation
also changes the direction for the encoder
commutation position.
5.6.1.12
Set Encoder Position
Encoders with a Hiperface or EnDat digital interface provide the facility to be able to set the datum position from
which the absolute position is measured. This feature is supported using the parameter
encoder_set_position
.
