ABB ACS880-104

Program features 89
Pos counter init cmd source, such as a proximity switch connected to a digital input, is
activated. A successful initialization is indicated by bit 4 of 90.35 Pos counter status.
Any subsequent initialization of the counter must first be enabled by 90.69 Reset pos
counter init ready. To define a time window for initializations, 90.68 Disable pos
counter initialization can be used to inhibit the signal from the proximity switch. An
active fault in the drive will also prevent counter initialization.
Encoder error handling
When an encoder is used for load feedback, the action taken in case of an encoder
error is specified by 90.55 Load feedback fault. If the parameter is set to Warning, the
calculation will continue smoothly using estimated motor position. If the encoder
recovers from the error, the calculation will smoothly switch back to encoder
feedback. The load position signals (90.04, 90.05 and 90.07) will continue to be
updated all the time, but bit 6 of 90.35 Pos counter status will be set to indicate
potentially inaccurate position data. In addition, bit 4 of 90.35 will be cleared upon the
next stop as a recommendation to reinitialize the position counter.
Parameter 90.60 Pos counter error and boot action defines whether position
calculation resumes from the previous value over an encoder error or control unit
reboot. By default, bit 4 of 90.35 Pos counter status is cleared after an error,
indicating that reinitialization is needed. With 90.60 set to Continue from previous
value, the position values are retained over an error or reboot; bit 6 of 90.35 is set
however to indicate that an error occurred.
Note: With a multiturn absolute encoder, bit 6 of 90.35 is cleared at the next stop of
the drive if the encoder has recovered from the error; bit 4 is not cleared. The status
of the position counter is retained over a control unit reboot, after which position
calculation resumes from the absolute position given by the encoder, taking into
account the initial position specified by 90.58.
WARNING! If the drive is in stopped state when an encoder error occurs, or if
the drive is not powered, parameters 90.04, 90.05, 90.07 and 90.35 are not
updated because no movement of the load can be detected. When using previous
position values (90.60 Pos counter error and boot action is set to Continue from
previous value), be aware that the position data is unreliable if the load is able to
move.
Reading/writing position counter values through fieldbus
The parameters of the position counter function, such as 90.07 Load position scaled
int and 90.58 Pos counter init value int, can be accessed from an upper-level control
system in the following formats:
• 16-bit integer (if 16 bits are sufficient for the application)
• 32-bit integer (can be accessed as two consequent 16-bit words).