Response of the new version: In future, the position read out by the encoder will be used to reconstruct the actual position in the controller. Basically, the actual position can only be reconstructed within the display range of the absolute feedback system (single-turn, multi-turn). If the display range of the encoder is exceeded in the case of an open circuit (for single-turn encoders more than one revolution), this can't be detected principally. The reconstruction of the actual position can't work in this case. The switch-on behaviour remains unchanged, i.e.: after power-up, the actual position in the controller will be set to the position read out by the encoder. In this case, the position still has to be reconstructed inside the controller.
What happens? Reading out the position information from the Hiperface absolute value encoder may lead to an erratic change of the actual position in the controller and, as a result, also in the higher-level control system.
A position step-change occurs if the actual position in the controller has already risen beyond the absolute value encoder's display range and is then overwritten with the absolute position read out from the encoder. In this case, the position information exceeding the encoder's display range will get lost.
The higher-level control system uses the actual position of the controller to generate the actual position of the axis ('AxisRef' structure). In the higher-level control system, the position step-change will not be compensated for and will show a corresponding effect.
When does this behaviour occur? Position step-changes occur under the following conditions:
The actual position in the controller has already reached a value outside the absolute value encoder's display range (Multiturn: >4096 rev., Singleturn: >1 rev.).
After reset of an encoder fault (e.g. open circuit) during operation (controller initialisation has already been completed), the i700 reads out the Hiperface absolute value encoder again.
Which products are affected? - i700 servo inverter
Short-term measures:
After an encoder fault (e.g.: open circuit), carry out another homing process for the axis.
As an alternative, the control system can write the correct actual position in the controller via the parameters 0x2983 and 0x3183.
Evaluation/recommendations:
Observe the recommendations under 'Short-term measures'.
